diff options
Diffstat (limited to 'fs/crypto')
| -rw-r--r-- | fs/crypto/Kconfig | 2 | ||||
| -rw-r--r-- | fs/crypto/Makefile | 10 | ||||
| -rw-r--r-- | fs/crypto/crypto.c | 45 | ||||
| -rw-r--r-- | fs/crypto/fname.c | 47 | ||||
| -rw-r--r-- | fs/crypto/fscrypt_private.h | 399 | ||||
| -rw-r--r-- | fs/crypto/hkdf.c | 181 | ||||
| -rw-r--r-- | fs/crypto/hooks.c | 6 | ||||
| -rw-r--r-- | fs/crypto/keyinfo.c | 611 | ||||
| -rw-r--r-- | fs/crypto/keyring.c | 984 | ||||
| -rw-r--r-- | fs/crypto/keysetup.c | 591 | ||||
| -rw-r--r-- | fs/crypto/keysetup_v1.c | 340 | ||||
| -rw-r--r-- | fs/crypto/policy.c | 434 |
12 files changed, 2833 insertions, 817 deletions
diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig index 5fdf24877c17..ff5a1746cbae 100644 --- a/fs/crypto/Kconfig +++ b/fs/crypto/Kconfig @@ -7,6 +7,8 @@ config FS_ENCRYPTION select CRYPTO_ECB select CRYPTO_XTS select CRYPTO_CTS + select CRYPTO_SHA512 + select CRYPTO_HMAC select KEYS help Enable encryption of files and directories. This diff --git a/fs/crypto/Makefile b/fs/crypto/Makefile index 4f0df5e682e4..232e2bb5a337 100644 --- a/fs/crypto/Makefile +++ b/fs/crypto/Makefile @@ -1,5 +1,13 @@ # SPDX-License-Identifier: GPL-2.0-only obj-$(CONFIG_FS_ENCRYPTION) += fscrypto.o -fscrypto-y := crypto.o fname.o hooks.o keyinfo.o policy.o +fscrypto-y := crypto.o \ + fname.o \ + hkdf.o \ + hooks.o \ + keyring.o \ + keysetup.o \ + keysetup_v1.o \ + policy.o + fscrypto-$(CONFIG_BLOCK) += bio.o diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c index 45c3d0427fb2..32a7ad0098cc 100644 --- a/fs/crypto/crypto.c +++ b/fs/crypto/crypto.c @@ -141,7 +141,7 @@ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num, memset(iv, 0, ci->ci_mode->ivsize); iv->lblk_num = cpu_to_le64(lblk_num); - if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY) + if (fscrypt_is_direct_key_policy(&ci->ci_policy)) memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE); if (ci->ci_essiv_tfm != NULL) @@ -188,10 +188,8 @@ int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw, res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); skcipher_request_free(req); if (res) { - fscrypt_err(inode->i_sb, - "%scryption failed for inode %lu, block %llu: %d", - (rw == FS_DECRYPT ? "de" : "en"), - inode->i_ino, lblk_num, res); + fscrypt_err(inode, "%scryption failed for block %llu: %d", + (rw == FS_DECRYPT ? "De" : "En"), lblk_num, res); return res; } return 0; @@ -453,7 +451,7 @@ fail: return res; } -void fscrypt_msg(struct super_block *sb, const char *level, +void fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...) { static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, @@ -467,8 +465,9 @@ void fscrypt_msg(struct super_block *sb, const char *level, va_start(args, fmt); vaf.fmt = fmt; vaf.va = &args; - if (sb) - printk("%sfscrypt (%s): %pV\n", level, sb->s_id, &vaf); + if (inode) + printk("%sfscrypt (%s, inode %lu): %pV\n", + level, inode->i_sb->s_id, inode->i_ino, &vaf); else printk("%sfscrypt: %pV\n", level, &vaf); va_end(args); @@ -479,6 +478,8 @@ void fscrypt_msg(struct super_block *sb, const char *level, */ static int __init fscrypt_init(void) { + int err = -ENOMEM; + /* * Use an unbound workqueue to allow bios to be decrypted in parallel * even when they happen to complete on the same CPU. This sacrifices @@ -501,31 +502,19 @@ static int __init fscrypt_init(void) if (!fscrypt_info_cachep) goto fail_free_ctx; + err = fscrypt_init_keyring(); + if (err) + goto fail_free_info; + return 0; +fail_free_info: + kmem_cache_destroy(fscrypt_info_cachep); fail_free_ctx: kmem_cache_destroy(fscrypt_ctx_cachep); fail_free_queue: destroy_workqueue(fscrypt_read_workqueue); fail: - return -ENOMEM; -} -module_init(fscrypt_init) - -/** - * fscrypt_exit() - Shutdown the fs encryption system - */ -static void __exit fscrypt_exit(void) -{ - fscrypt_destroy(); - - if (fscrypt_read_workqueue) - destroy_workqueue(fscrypt_read_workqueue); - kmem_cache_destroy(fscrypt_ctx_cachep); - kmem_cache_destroy(fscrypt_info_cachep); - - fscrypt_essiv_cleanup(); + return err; } -module_exit(fscrypt_exit); - -MODULE_LICENSE("GPL"); +late_initcall(fscrypt_init) diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c index 00d150ff3033..3da3707c10e3 100644 --- a/fs/crypto/fname.c +++ b/fs/crypto/fname.c @@ -71,9 +71,7 @@ int fname_encrypt(struct inode *inode, const struct qstr *iname, res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); skcipher_request_free(req); if (res < 0) { - fscrypt_err(inode->i_sb, - "Filename encryption failed for inode %lu: %d", - inode->i_ino, res); + fscrypt_err(inode, "Filename encryption failed: %d", res); return res; } @@ -117,9 +115,7 @@ static int fname_decrypt(struct inode *inode, res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait); skcipher_request_free(req); if (res < 0) { - fscrypt_err(inode->i_sb, - "Filename decryption failed for inode %lu: %d", - inode->i_ino, res); + fscrypt_err(inode, "Filename decryption failed: %d", res); return res; } @@ -127,44 +123,45 @@ static int fname_decrypt(struct inode *inode, return 0; } -static const char *lookup_table = +static const char lookup_table[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,"; #define BASE64_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3) /** - * digest_encode() - + * base64_encode() - * - * Encodes the input digest using characters from the set [a-zA-Z0-9_+]. + * Encodes the input string using characters from the set [A-Za-z0-9+,]. * The encoded string is roughly 4/3 times the size of the input string. + * + * Return: length of the encoded string */ -static int digest_encode(const char *src, int len, char *dst) +static int base64_encode(const u8 *src, int len, char *dst) { - int i = 0, bits = 0, ac = 0; + int i, bits = 0, ac = 0; char *cp = dst; - while (i < len) { - ac += (((unsigned char) src[i]) << bits); + for (i = 0; i < len; i++) { + ac += src[i] << bits; bits += 8; do { *cp++ = lookup_table[ac & 0x3f]; ac >>= 6; bits -= 6; } while (bits >= 6); - i++; } if (bits) *cp++ = lookup_table[ac & 0x3f]; return cp - dst; } -static int digest_decode(const char *src, int len, char *dst) +static int base64_decode(const char *src, int len, u8 *dst) { - int i = 0, bits = 0, ac = 0; + int i, bits = 0, ac = 0; const char *p; - char *cp = dst; + u8 *cp = dst; - while (i < len) { + for (i = 0; i < len; i++) { p = strchr(lookup_table, src[i]); if (p == NULL || src[i] == 0) return -2; @@ -175,7 +172,6 @@ static int digest_decode(const char *src, int len, char *dst) ac >>= 8; bits -= 8; } - i++; } if (ac) return -1; @@ -185,8 +181,9 @@ static int digest_decode(const char *src, int len, char *dst) bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, u32 max_len, u32 *encrypted_len_ret) { - int padding = 4 << (inode->i_crypt_info->ci_flags & - FS_POLICY_FLAGS_PAD_MASK); + const struct fscrypt_info *ci = inode->i_crypt_info; + int padding = 4 << (fscrypt_policy_flags(&ci->ci_policy) & + FSCRYPT_POLICY_FLAGS_PAD_MASK); u32 encrypted_len; if (orig_len > max_len) @@ -272,7 +269,7 @@ int fscrypt_fname_disk_to_usr(struct inode *inode, return fname_decrypt(inode, iname, oname); if (iname->len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) { - oname->len = digest_encode(iname->name, iname->len, + oname->len = base64_encode(iname->name, iname->len, oname->name); return 0; } @@ -287,7 +284,7 @@ int fscrypt_fname_disk_to_usr(struct inode *inode, FSCRYPT_FNAME_DIGEST(iname->name, iname->len), FSCRYPT_FNAME_DIGEST_SIZE); oname->name[0] = '_'; - oname->len = 1 + digest_encode((const char *)&digested_name, + oname->len = 1 + base64_encode((const u8 *)&digested_name, sizeof(digested_name), oname->name + 1); return 0; } @@ -380,8 +377,8 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname, if (fname->crypto_buf.name == NULL) return -ENOMEM; - ret = digest_decode(iname->name + digested, iname->len - digested, - fname->crypto_buf.name); + ret = base64_decode(iname->name + digested, iname->len - digested, + fname->crypto_buf.name); if (ret < 0) { ret = -ENOENT; goto errout; diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h index 8978eec9d766..e84efc01512e 100644 --- a/fs/crypto/fscrypt_private.h +++ b/fs/crypto/fscrypt_private.h @@ -4,9 +4,8 @@ * * Copyright (C) 2015, Google, Inc. * - * This contains encryption key functions. - * - * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015. + * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar. + * Heavily modified since then. */ #ifndef _FSCRYPT_PRIVATE_H @@ -15,30 +14,133 @@ #include <linux/fscrypt.h> #include <crypto/hash.h> -/* Encryption parameters */ +#define CONST_STRLEN(str) (sizeof(str) - 1) + #define FS_KEY_DERIVATION_NONCE_SIZE 16 -/** - * Encryption context for inode - * - * Protector format: - * 1 byte: Protector format (1 = this version) - * 1 byte: File contents encryption mode - * 1 byte: File names encryption mode - * 1 byte: Flags - * 8 bytes: Master Key descriptor - * 16 bytes: Encryption Key derivation nonce - */ -struct fscrypt_context { - u8 format; +#define FSCRYPT_MIN_KEY_SIZE 16 + +#define FSCRYPT_CONTEXT_V1 1 +#define FSCRYPT_CONTEXT_V2 2 + +struct fscrypt_context_v1 { + u8 version; /* FSCRYPT_CONTEXT_V1 */ u8 contents_encryption_mode; u8 filenames_encryption_mode; u8 flags; - u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE]; + u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE]; -} __packed; +}; -#define FS_ENCRYPTION_CONTEXT_FORMAT_V1 1 +struct fscrypt_context_v2 { + u8 version; /* FSCRYPT_CONTEXT_V2 */ + u8 contents_encryption_mode; + u8 filenames_encryption_mode; + u8 flags; + u8 __reserved[4]; + u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]; + u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE]; +}; + +/** + * fscrypt_context - the encryption context of an inode + * + * This is the on-disk equivalent of an fscrypt_policy, stored alongside each + * encrypted file usually in a hidden extended attribute. It contains the + * fields from the fscrypt_policy, in order to identify the encryption algorithm + * and key with which the file is encrypted. It also contains a nonce that was + * randomly generated by fscrypt itself; this is used as KDF input or as a tweak + * to cause different files to be encrypted differently. + */ +union fscrypt_context { + u8 version; + struct fscrypt_context_v1 v1; + struct fscrypt_context_v2 v2; +}; + +/* + * Return the size expected for the given fscrypt_context based on its version + * number, or 0 if the context version is unrecognized. + */ +static inline int fscrypt_context_size(const union fscrypt_context *ctx) +{ + switch (ctx->version) { + case FSCRYPT_CONTEXT_V1: + BUILD_BUG_ON(sizeof(ctx->v1) != 28); + return sizeof(ctx->v1); + case FSCRYPT_CONTEXT_V2: + BUILD_BUG_ON(sizeof(ctx->v2) != 40); + return sizeof(ctx->v2); + } + return 0; +} + +#undef fscrypt_policy +union fscrypt_policy { + u8 version; + struct fscrypt_policy_v1 v1; + struct fscrypt_policy_v2 v2; +}; + +/* + * Return the size expected for the given fscrypt_policy based on its version + * number, or 0 if the policy version is unrecognized. + */ +static inline int fscrypt_policy_size(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return sizeof(policy->v1); + case FSCRYPT_POLICY_V2: + return sizeof(policy->v2); + } + return 0; +} + +/* Return the contents encryption mode of a valid encryption policy */ +static inline u8 +fscrypt_policy_contents_mode(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return policy->v1.contents_encryption_mode; + case FSCRYPT_POLICY_V2: + return policy->v2.contents_encryption_mode; + } + BUG(); +} + +/* Return the filenames encryption mode of a valid encryption policy */ +static inline u8 +fscrypt_policy_fnames_mode(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return policy->v1.filenames_encryption_mode; + case FSCRYPT_POLICY_V2: + return policy->v2.filenames_encryption_mode; + } + BUG(); +} + +/* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */ +static inline u8 +fscrypt_policy_flags(const union fscrypt_policy *policy) +{ + switch (policy->version) { + case FSCRYPT_POLICY_V1: + return policy->v1.flags; + case FSCRYPT_POLICY_V2: + return policy->v2.flags; + } + BUG(); +} + +static inline bool +fscrypt_is_direct_key_policy(const union fscrypt_policy *policy) +{ + return fscrypt_policy_flags(policy) & FSCRYPT_POLICY_FLAG_DIRECT_KEY; +} /** * For encrypted symlinks, the ciphertext length is stored at the beginning @@ -68,23 +170,37 @@ struct fscrypt_info { struct crypto_cipher *ci_essiv_tfm; /* - * Encryption mode used for this inode. It corresponds to either - * ci_data_mode or ci_filename_mode, depending on the inode type. + * Encryption mode used for this inode. It corresponds to either the + * contents or filenames encryption mode, depending on the inode type. */ struct fscrypt_mode *ci_mode; + /* Back-pointer to the inode */ + struct inode *ci_inode; + + /* + * The master key with which this inode was unlocked (decrypted). This + * will be NULL if the master key was found in a process-subscribed + * keyring rather than in the filesystem-level keyring. + */ + struct key *ci_master_key; + + /* + * Link in list of inodes that were unlocked with the master key. + * Only used when ->ci_master_key is set. + */ + struct list_head ci_master_key_link; + /* - * If non-NULL, then this inode uses a master key directly rather than a - * derived key, and ci_ctfm will equal ci_master_key->mk_ctfm. - * Otherwise, this inode uses a derived key. + * If non-NULL, then encryption is done using the master key directly + * and ci_ctfm will equal ci_direct_key->dk_ctfm. */ - struct fscrypt_master_key *ci_master_key; + struct fscrypt_direct_key *ci_direct_key; - /* fields from the fscrypt_context */ - u8 ci_data_mode; - u8 ci_filename_mode; - u8 ci_flags; - u8 ci_master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE]; + /* The encryption policy used by this inode */ + union fscrypt_policy ci_policy; + + /* This inode's nonce, copied from the fscrypt_context */ u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE]; }; @@ -98,16 +214,16 @@ typedef enum { static inline bool fscrypt_valid_enc_modes(u32 contents_mode, u32 filenames_mode) { - if (contents_mode == FS_ENCRYPTION_MODE_AES_128_CBC && - filenames_mode == FS_ENCRYPTION_MODE_AES_128_CTS) + if (contents_mode == FSCRYPT_MODE_AES_128_CBC && + filenames_mode == FSCRYPT_MODE_AES_128_CTS) return true; - if (contents_mode == FS_ENCRYPTION_MODE_AES_256_XTS && - filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS) + if (contents_mode == FSCRYPT_MODE_AES_256_XTS && + filenames_mode == FSCRYPT_MODE_AES_256_CTS) return true; - if (contents_mode == FS_ENCRYPTION_MODE_ADIANTUM && - filenames_mode == FS_ENCRYPTION_MODE_ADIANTUM) + if (contents_mode == FSCRYPT_MODE_ADIANTUM && + filenames_mode == FSCRYPT_MODE_ADIANTUM) return true; return false; @@ -125,12 +241,12 @@ extern struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags); extern const struct dentry_operations fscrypt_d_ops; extern void __printf(3, 4) __cold -fscrypt_msg(struct super_block *sb, const char *level, const char *fmt, ...); +fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...); -#define fscrypt_warn(sb, fmt, ...) \ - fscrypt_msg(sb, KERN_WARNING, fmt, ##__VA_ARGS__) -#define fscrypt_err(sb, fmt, ...) \ - fscrypt_msg(sb, KERN_ERR, fmt, ##__VA_ARGS__) +#define fscrypt_warn(inode, fmt, ...) \ + fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) +#define fscrypt_err(inode, fmt, ...) \ + fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) #define FSCRYPT_MAX_IV_SIZE 32 @@ -155,7 +271,172 @@ extern bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len, u32 max_len, u32 *encrypted_len_ret); -/* keyinfo.c */ +/* hkdf.c */ + +struct fscrypt_hkdf { + struct crypto_shash *hmac_tfm; +}; + +extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, + unsigned int master_key_size); + +/* + * The list of contexts in which fscrypt uses HKDF. These values are used as + * the first byte of the HKDF application-specific info string to guarantee that + * info strings are never repeated between contexts. This ensures that all HKDF + * outputs are unique and cryptographically isolated, i.e. knowledge of one + * output doesn't reveal another. + */ +#define HKDF_CONTEXT_KEY_IDENTIFIER 1 +#define HKDF_CONTEXT_PER_FILE_KEY 2 +#define HKDF_CONTEXT_PER_MODE_KEY 3 + +extern int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context, + const u8 *info, unsigned int infolen, + u8 *okm, unsigned int okmlen); + +extern void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf); + +/* keyring.c */ + +/* + * fscrypt_master_key_secret - secret key material of an in-use master key + */ +struct fscrypt_master_key_secret { + + /* + * For v2 policy keys: HKDF context keyed by this master key. + * For v1 policy keys: not set (hkdf.hmac_tfm == NULL). + */ + struct fscrypt_hkdf hkdf; + + /* Size of the raw key in bytes. Set even if ->raw isn't set. */ + u32 size; + + /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */ + u8 raw[FSCRYPT_MAX_KEY_SIZE]; + +} __randomize_layout; + +/* + * fscrypt_master_key - an in-use master key + * + * This represents a master encryption key which has been added to the + * filesystem and can be used to "unlock" the encrypted files which were + * encrypted with it. + */ +struct fscrypt_master_key { + + /* + * The secret key material. After FS_IOC_REMOVE_ENCRYPTION_KEY is + * executed, this is wiped and no new inodes can be unlocked with this + * key; however, there may still be inodes in ->mk_decrypted_inodes + * which could not be evicted. As long as some inodes still remain, + * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or + * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again. + * + * Locking: protected by key->sem (outer) and mk_secret_sem (inner). + * The reason for two locks is that key->sem also protects modifying + * mk_users, which ranks it above the semaphore for the keyring key + * type, which is in turn above page faults (via keyring_read). But + * sometimes filesystems call fscrypt_get_encryption_info() from within + * a transaction, which ranks it below page faults. So we need a + * separate lock which protects mk_secret but not also mk_users. + */ + struct fscrypt_master_key_secret mk_secret; + struct rw_semaphore mk_secret_sem; + + /* + * For v1 policy keys: an arbitrary key descriptor which was assigned by + * userspace (->descriptor). + * + * For v2 policy keys: a cryptographic hash of this key (->identifier). + */ + struct fscrypt_key_specifier mk_spec; + + /* + * Keyring which contains a key of type 'key_type_fscrypt_user' for each + * user who has added this key. Normally each key will be added by just + * one user, but it's possible that multiple users share a key, and in + * that case we need to keep track of those users so that one user can't + * remove the key before the others want it removed too. + * + * This is NULL for v1 policy keys; those can only be added by root. + * + * Locking: in addition to this keyrings own semaphore, this is + * protected by the master key's key->sem, so we can do atomic + * search+insert. It can also be searched without taking any locks, but + * in that case the returned key may have already been removed. + */ + struct key *mk_users; + + /* + * Length of ->mk_decrypted_inodes, plus one if mk_secret is present. + * Once this goes to 0, the master key is removed from ->s_master_keys. + * The 'struct fscrypt_master_key' will continue to live as long as the + * 'struct key' whose payload it is, but we won't let this reference + * count rise again. + */ + refcount_t mk_refcount; + + /* + * List of inodes that were unlocked using this key. This allows the + * inodes to be evicted efficiently if the key is removed. + */ + struct list_head mk_decrypted_inodes; + spinlock_t mk_decrypted_inodes_lock; + + /* Per-mode tfms for DIRECT_KEY policies, allocated on-demand */ + struct crypto_skcipher *mk_mode_keys[__FSCRYPT_MODE_MAX + 1]; + +} __randomize_layout; + +static inline bool +is_master_key_secret_present(const struct fscrypt_master_key_secret *secret) +{ + /* + * The READ_ONCE() is only necessary for fscrypt_drop_inode() and + * fscrypt_key_describe(). These run in atomic context, so they can't + * take ->mk_secret_sem and thus 'secret' can change concurrently which + * would be a data race. But they only need to know whether the secret + * *was* present at the time of check, so READ_ONCE() suffices. + */ + return READ_ONCE(secret->size) != 0; +} + +static inline const char *master_key_spec_type( + const struct fscrypt_key_specifier *spec) +{ + switch (spec->type) { + case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR: + return "descriptor"; + case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER: + return "identifier"; + } + return "[unknown]"; +} + +static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec) +{ + switch (spec->type) { + case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR: + return FSCRYPT_KEY_DESCRIPTOR_SIZE; + case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER: + return FSCRYPT_KEY_IDENTIFIER_SIZE; + } + return 0; +} + +extern struct key * +fscrypt_find_master_key(struct super_block *sb, + const struct fscrypt_key_specifier *mk_spec); + +extern int fscrypt_verify_key_added(struct super_block *sb, + const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]); + +extern int __init fscrypt_init_keyring(void); + +/* keysetup.c */ struct fscrypt_mode { const char *friendly_name; @@ -166,6 +447,36 @@ struct fscrypt_mode { bool needs_essiv; }; -extern void __exit fscrypt_essiv_cleanup(void); +static inline bool +fscrypt_mode_supports_direct_key(const struct fscrypt_mode *mode) +{ + return mode->ivsize >= offsetofend(union fscrypt_iv, nonce); +} + +extern struct crypto_skcipher * +fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key, + const struct inode *inode); + +extern int fscrypt_set_derived_key(struct fscrypt_info *ci, + const u8 *derived_key); + +/* keysetup_v1.c */ + +extern void fscrypt_put_direct_key(struct fscrypt_direct_key *dk); + +extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, + const u8 *raw_master_key); + +extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings( + struct fscrypt_info *ci); +/* policy.c */ + +extern bool fscrypt_policies_equal(const union fscrypt_policy *policy1, + const union fscrypt_policy *policy2); +extern bool fscrypt_supported_policy(const union fscrypt_policy *policy_u, + const struct inode *inode); +extern int fscrypt_policy_from_context(union fscrypt_policy *policy_u, + const union fscrypt_context *ctx_u, + int ctx_size); #endif /* _FSCRYPT_PRIVATE_H */ diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c new file mode 100644 index 000000000000..f21873e1b467 --- /dev/null +++ b/fs/crypto/hkdf.c @@ -0,0 +1,181 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation + * Function"), aka RFC 5869. See also the original paper (Krawczyk 2010): + * "Cryptographic Extraction and Key Derivation: The HKDF Scheme". + * + * This is used to derive keys from the fscrypt master keys. + * + * Copyright 2019 Google LLC + */ + +#include <crypto/hash.h> +#include <crypto/sha.h> + +#include "fscrypt_private.h" + +/* + * HKDF supports any unkeyed cryptographic hash algorithm, but fscrypt uses + * SHA-512 because it is reasonably secure and efficient; and since it produces + * a 64-byte digest, deriving an AES-256-XTS key preserves all 64 bytes of + * entropy from the master key and requires only one iteration of HKDF-Expand. + */ +#define HKDF_HMAC_ALG "hmac(sha512)" +#define HKDF_HASHLEN SHA512_DIGEST_SIZE + +/* + * HKDF consists of two steps: + * + * 1. HKDF-Extract: extract a pseudorandom key of length HKDF_HASHLEN bytes from + * the input keying material and optional salt. + * 2. HKDF-Expand: expand the pseudorandom key into output keying material of + * any length, parameterized by an application-specific info string. + * + * HKDF-Extract can be skipped if the input is already a pseudorandom key of + * length HKDF_HASHLEN bytes. However, cipher modes other than AES-256-XTS take + * shorter keys, and we don't want to force users of those modes to provide + * unnecessarily long master keys. Thus fscrypt still does HKDF-Extract. No + * salt is used, since fscrypt master keys should already be pseudorandom and + * there's no way to persist a random salt per master key from kernel mode. + */ + +/* HKDF-Extract (RFC 5869 section 2.2), unsalted */ +static int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm, + unsigned int ikmlen, u8 prk[HKDF_HASHLEN]) +{ + static const u8 default_salt[HKDF_HASHLEN]; + SHASH_DESC_ON_STACK(desc, hmac_tfm); + int err; + + err = crypto_shash_setkey(hmac_tfm, default_salt, HKDF_HASHLEN); + if (err) + return err; + + desc->tfm = hmac_tfm; + err = crypto_shash_digest(desc, ikm, ikmlen, prk); + shash_desc_zero(desc); + return err; +} + +/* + * Compute HKDF-Extract using the given master key as the input keying material, + * and prepare an HMAC transform object keyed by the resulting pseudorandom key. + * + * Afterwards, the keyed HMAC transform object can be used for HKDF-Expand many + * times without having to recompute HKDF-Extract each time. + */ +int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key, + unsigned int master_key_size) +{ + struct crypto_shash *hmac_tfm; + u8 prk[HKDF_HASHLEN]; + int err; + + hmac_tfm = crypto_alloc_shash(HKDF_HMAC_ALG, 0, 0); + if (IS_ERR(hmac_tfm)) { + fscrypt_err(NULL, "Error allocating " HKDF_HMAC_ALG ": %ld", + PTR_ERR(hmac_tfm)); + return PTR_ERR(hmac_tfm); + } + + if (WARN_ON(crypto_shash_digestsize(hmac_tfm) != sizeof(prk))) { + err = -EINVAL; + goto err_free_tfm; + } + + err = hkdf_extract(hmac_tfm, master_key, master_key_size, prk); + if (err) + goto err_free_tfm; + + err = crypto_shash_setkey(hmac_tfm, prk, sizeof(prk)); + if (err) + goto err_free_tfm; + + hkdf->hmac_tfm = hmac_tfm; + goto out; + +err_free_tfm: + crypto_free_shash(hmac_tfm); +out: + memzero_explicit(prk, sizeof(prk)); + return err; +} + +/* + * HKDF-Expand (RFC 5869 section 2.3). This expands the pseudorandom key, which + * was already keyed into 'hkdf->hmac_tfm' by fscrypt_init_hkdf(), into 'okmlen' + * bytes of output keying material parameterized by the application-specific + * 'info' of length 'infolen' bytes, prefixed by "fscrypt\0" and the 'context' + * byte. This is thread-safe and may be called by multiple threads in parallel. + * + * ('context' isn't part of the HKDF specification; it's just a prefix fscrypt + * adds to its application-specific info strings to guarantee that it doesn't + * accidentally repeat an info string when using HKDF for different purposes.) + */ +int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context, + const u8 *info, unsigned int infolen, + u8 *okm, unsigned int okmlen) +{ + SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm); + u8 prefix[9]; + unsigned int i; + int err; + const u8 *prev = NULL; + u8 counter = 1; + u8 tmp[HKDF_HASHLEN]; + + if (WARN_ON(okmlen > 255 * HKDF_HASHLEN)) + return -EINVAL; + + desc->tfm = hkdf->hmac_tfm; + + memcpy(prefix, "fscrypt\0", 8); + prefix[8] = context; + + for (i = 0; i < okmlen; i += HKDF_HASHLEN) { + + err = crypto_shash_init(desc); + if (err) + goto out; + + if (prev) { + err = crypto_shash_update(desc, prev, HKDF_HASHLEN); + if (err) + goto out; + } + + err = crypto_shash_update(desc, prefix, sizeof(prefix)); + if (err) + goto out; + + err = crypto_shash_update(desc, info, infolen); + if (err) + goto out; + + BUILD_BUG_ON(sizeof(counter) != 1); + if (okmlen - i < HKDF_HASHLEN) { + err = crypto_shash_finup(desc, &counter, 1, tmp); + if (err) + goto out; + memcpy(&okm[i], tmp, okmlen - i); + memzero_explicit(tmp, sizeof(tmp)); + } else { + err = crypto_shash_finup(desc, &counter, 1, &okm[i]); + if (err) + goto out; + } + counter++; + prev = &okm[i]; + } + err = 0; +out: + if (unlikely(err)) + memzero_explicit(okm, okmlen); /* so caller doesn't need to */ + shash_desc_zero(desc); + return err; +} + +void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf) +{ + crypto_free_shash(hkdf->hmac_tfm); +} diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c index c1d6715d88e9..bb3b7fcfdd48 100644 --- a/fs/crypto/hooks.c +++ b/fs/crypto/hooks.c @@ -39,9 +39,9 @@ int fscrypt_file_open(struct inode *inode, struct file *filp) dir = dget_parent(file_dentry(filp)); if (IS_ENCRYPTED(d_inode(dir)) && !fscrypt_has_permitted_context(d_inode(dir), inode)) { - fscrypt_warn(inode->i_sb, - "inconsistent encryption contexts: %lu/%lu", - d_inode(dir)->i_ino, inode->i_ino); + fscrypt_warn(inode, + "Inconsistent encryption context (parent directory: %lu)", + d_inode(dir)->i_ino); err = -EPERM; } dput(dir); diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c deleted file mode 100644 index 207ebed918c1..000000000000 --- a/fs/crypto/keyinfo.c +++ /dev/null @@ -1,611 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0 -/* - * key management facility for FS encryption support. - * - * Copyright (C) 2015, Google, Inc. - * - * This contains encryption key functions. - * - * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015. - */ - -#include <keys/user-type.h> -#include <linux/hashtable.h> -#include <linux/scatterlist.h> -#include <crypto/aes.h> -#include <crypto/algapi.h> -#include <crypto/sha.h> -#include <crypto/skcipher.h> -#include "fscrypt_private.h" - -static struct crypto_shash *essiv_hash_tfm; - -/* Table of keys referenced by FS_POLICY_FLAG_DIRECT_KEY policies */ -static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */ -static DEFINE_SPINLOCK(fscrypt_master_keys_lock); - -/* - * Key derivation function. This generates the derived key by encrypting the - * master key with AES-128-ECB using the inode's nonce as the AES key. - * - * The master key must be at least as long as the derived key. If the master - * key is longer, then only the first 'derived_keysize' bytes are used. - */ -static int derive_key_aes(const u8 *master_key, - const struct fscrypt_context *ctx, - u8 *derived_key, unsigned int derived_keysize) -{ - int res = 0; - struct skcipher_request *req = NULL; - DECLARE_CRYPTO_WAIT(wait); - struct scatterlist src_sg, dst_sg; - struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0); - - if (IS_ERR(tfm)) { - res = PTR_ERR(tfm); - tfm = NULL; - goto out; - } - crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); - req = skcipher_request_alloc(tfm, GFP_NOFS); - if (!req) { - res = -ENOMEM; - goto out; - } - skcipher_request_set_callback(req, - CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, - crypto_req_done, &wait); - res = crypto_skcipher_setkey(tfm, ctx->nonce, sizeof(ctx->nonce)); - if (res < 0) - goto out; - - sg_init_one(&src_sg, master_key, derived_keysize); - sg_init_one(&dst_sg, derived_key, derived_keysize); - skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize, - NULL); - res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); -out: - skcipher_request_free(req); - crypto_free_skcipher(tfm); - return res; -} - -/* - * Search the current task's subscribed keyrings for a "logon" key with - * description prefix:descriptor, and if found acquire a read lock on it and - * return a pointer to its validated payload in *payload_ret. - */ -static struct key * -find_and_lock_process_key(const char *prefix, - const u8 descriptor[FS_KEY_DESCRIPTOR_SIZE], - unsigned int min_keysize, - const struct fscrypt_key **payload_ret) -{ - char *description; - struct key *key; - const struct user_key_payload *ukp; - const struct fscrypt_key *payload; - - description = kasprintf(GFP_NOFS, "%s%*phN", prefix, - FS_KEY_DESCRIPTOR_SIZE, descriptor); - if (!description) - return ERR_PTR(-ENOMEM); - - key = request_key(&key_type_logon, description, NULL); - kfree(description); - if (IS_ERR(key)) - return key; - - down_read(&key->sem); - ukp = user_key_payload_locked(key); - - if (!ukp) /* was the key revoked before we acquired its semaphore? */ - goto invalid; - - payload = (const struct fscrypt_key *)ukp->data; - - if (ukp->datalen != sizeof(struct fscrypt_key) || - payload->size < 1 || payload->size > FS_MAX_KEY_SIZE) { - fscrypt_warn(NULL, - "key with description '%s' has invalid payload", - key->description); - goto invalid; - } - - if (payload->size < min_keysize) { - fscrypt_warn(NULL, - "key with description '%s' is too short (got %u bytes, need %u+ bytes)", - key->description, payload->size, min_keysize); - goto invalid; - } - - *payload_ret = payload; - return key; - -invalid: - up_read(&key->sem); - key_put(key); - return ERR_PTR(-ENOKEY); -} - -static struct fscrypt_mode available_modes[] = { - [FS_ENCRYPTION_MODE_AES_256_XTS] = { - .friendly_name = "AES-256-XTS", - .cipher_str = "xts(aes)", - .keysize = 64, - .ivsize = 16, - }, - [FS_ENCRYPTION_MODE_AES_256_CTS] = { - .friendly_name = "AES-256-CTS-CBC", - .cipher_str = "cts(cbc(aes))", - .keysize = 32, - .ivsize = 16, - }, - [FS_ENCRYPTION_MODE_AES_128_CBC] = { - .friendly_name = "AES-128-CBC", - .cipher_str = "cbc(aes)", - .keysize = 16, - .ivsize = 16, - .needs_essiv = true, - }, - [FS_ENCRYPTION_MODE_AES_128_CTS] = { - .friendly_name = "AES-128-CTS-CBC", - .cipher_str = "cts(cbc(aes))", - .keysize = 16, - .ivsize = 16, - }, - [FS_ENCRYPTION_MODE_ADIANTUM] = { - .friendly_name = "Adiantum", - .cipher_str = "adiantum(xchacha12,aes)", - .keysize = 32, - .ivsize = 32, - }, -}; - -static struct fscrypt_mode * -select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode) -{ - if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) { - fscrypt_warn(inode->i_sb, - "inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)", - inode->i_ino, ci->ci_data_mode, - ci->ci_filename_mode); - return ERR_PTR(-EINVAL); - } - - if (S_ISREG(inode->i_mode)) - return &available_modes[ci->ci_data_mode]; - - if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) - return &available_modes[ci->ci_filename_mode]; - - WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", - inode->i_ino, (inode->i_mode & S_IFMT)); - return ERR_PTR(-EINVAL); -} - -/* Find the master key, then derive the inode's actual encryption key */ -static int find_and_derive_key(const struct inode *inode, - const struct fscrypt_context *ctx, - u8 *derived_key, const struct fscrypt_mode *mode) -{ - struct key *key; - const struct fscrypt_key *payload; - int err; - - key = find_and_lock_process_key(FS_KEY_DESC_PREFIX, - ctx->master_key_descriptor, - mode->keysize, &payload); - if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) { - key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix, - ctx->master_key_descriptor, - mode->keysize, &payload); - } - if (IS_ERR(key)) - return PTR_ERR(key); - - if (ctx->flags & FS_POLICY_FLAG_DIRECT_KEY) { - if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) { - fscrypt_warn(inode->i_sb, - "direct key mode not allowed with %s", - mode->friendly_name); - err = -EINVAL; - } else if (ctx->contents_encryption_mode != - ctx->filenames_encryption_mode) { - fscrypt_warn(inode->i_sb, - "direct key mode not allowed with different contents and filenames modes"); - err = -EINVAL; - } else { - memcpy(derived_key, payload->raw, mode->keysize); - err = 0; - } - } else { - err = derive_key_aes(payload->raw, ctx, derived_key, - mode->keysize); - } - up_read(&key->sem); - key_put(key); - return err; -} - -/* Allocate and key a symmetric cipher object for the given encryption mode */ -static struct crypto_skcipher * -allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key, - const struct inode *inode) -{ - struct crypto_skcipher *tfm; - int err; - - tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); - if (IS_ERR(tfm)) { - fscrypt_warn(inode->i_sb, - "error allocating '%s' transform for inode %lu: %ld", - mode->cipher_str, inode->i_ino, PTR_ERR(tfm)); - return tfm; - } - if (unlikely(!mode->logged_impl_name)) { - /* - * fscrypt performance can vary greatly depending on which - * crypto algorithm implementation is used. Help people debug - * performance problems by logging the ->cra_driver_name the - * first time a mode is used. Note that multiple threads can - * race here, but it doesn't really matter. - */ - mode->logged_impl_name = true; - pr_info("fscrypt: %s using implementation \"%s\"\n", - mode->friendly_name, - crypto_skcipher_alg(tfm)->base.cra_driver_name); - } - crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); - err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize); - if (err) - goto err_free_tfm; - - return tfm; - -err_free_tfm: - crypto_free_skcipher(tfm); - return ERR_PTR(err); -} - -/* Master key referenced by FS_POLICY_FLAG_DIRECT_KEY policy */ -struct fscrypt_master_key { - struct hlist_node mk_node; - refcount_t mk_refcount; - const struct fscrypt_mode *mk_mode; - struct crypto_skcipher *mk_ctfm; - u8 mk_descriptor[FS_KEY_DESCRIPTOR_SIZE]; - u8 mk_raw[FS_MAX_KEY_SIZE]; -}; - -static void free_master_key(struct fscrypt_master_key *mk) -{ - if (mk) { - crypto_free_skcipher(mk->mk_ctfm); - kzfree(mk); - } -} - -static void put_master_key(struct fscrypt_master_key *mk) -{ - if (!refcount_dec_and_lock(&mk->mk_refcount, &fscrypt_master_keys_lock)) - return; - hash_del(&mk->mk_node); - spin_unlock(&fscrypt_master_keys_lock); - - free_master_key(mk); -} - -/* - * Find/insert the given master key into the fscrypt_master_keys table. If - * found, it is returned with elevated refcount, and 'to_insert' is freed if - * non-NULL. If not found, 'to_insert' is inserted and returned if it's - * non-NULL; otherwise NULL is returned. - */ -static struct fscrypt_master_key * -find_or_insert_master_key(struct fscrypt_master_key *to_insert, - const u8 *raw_key, const struct fscrypt_mode *mode, - const struct fscrypt_info *ci) -{ - unsigned long hash_key; - struct fscrypt_master_key *mk; - - /* - * Careful: to avoid potentially leaking secret key bytes via timing - * information, we must key the hash table by descriptor rather than by - * raw key, and use crypto_memneq() when comparing raw keys. - */ - - BUILD_BUG_ON(sizeof(hash_key) > FS_KEY_DESCRIPTOR_SIZE); - memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key)); - - spin_lock(&fscrypt_master_keys_lock); - hash_for_each_possible(fscrypt_master_keys, mk, mk_node, hash_key) { - if (memcmp(ci->ci_master_key_descriptor, mk->mk_descriptor, - FS_KEY_DESCRIPTOR_SIZE) != 0) - continue; - if (mode != mk->mk_mode) - continue; - if (crypto_memneq(raw_key, mk->mk_raw, mode->keysize)) - continue; - /* using existing tfm with same (descriptor, mode, raw_key) */ - refcount_inc(&mk->mk_refcount); - spin_unlock(&fscrypt_master_keys_lock); - free_master_key(to_insert); - return mk; - } - if (to_insert) - hash_add(fscrypt_master_keys, &to_insert->mk_node, hash_key); - spin_unlock(&fscrypt_master_keys_lock); - return to_insert; -} - -/* Prepare to encrypt directly using the master key in the given mode */ -static struct fscrypt_master_key * -fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode, - const u8 *raw_key, const struct inode *inode) -{ - struct fscrypt_master_key *mk; - int err; - - /* Is there already a tfm for this key? */ - mk = find_or_insert_master_key(NULL, raw_key, mode, ci); - if (mk) - return mk; - - /* Nope, allocate one. */ - mk = kzalloc(sizeof(*mk), GFP_NOFS); - if (!mk) - return ERR_PTR(-ENOMEM); - refcount_set(&mk->mk_refcount, 1); - mk->mk_mode = mode; - mk->mk_ctfm = allocate_skcipher_for_mode(mode, raw_key, inode); - if (IS_ERR(mk->mk_ctfm)) { - err = PTR_ERR(mk->mk_ctfm); - mk->mk_ctfm = NULL; - goto err_free_mk; - } - memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE); - memcpy(mk->mk_raw, raw_key, mode->keysize); - - return find_or_insert_master_key(mk, raw_key, mode, ci); - -err_free_mk: - free_master_key(mk); - return ERR_PTR(err); -} - -static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt) -{ - struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm); - - /* init hash transform on demand */ - if (unlikely(!tfm)) { - struct crypto_shash *prev_tfm; - - tfm = crypto_alloc_shash("sha256", 0, 0); - if (IS_ERR(tfm)) { - fscrypt_warn(NULL, - "error allocating SHA-256 transform: %ld", - PTR_ERR(tfm)); - return PTR_ERR(tfm); - } - prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm); - if (prev_tfm) { - crypto_free_shash(tfm); - tfm = prev_tfm; - } - } - - { - SHASH_DESC_ON_STACK(desc, tfm); - desc->tfm = tfm; - - return crypto_shash_digest(desc, key, keysize, salt); - } -} - -static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key, - int keysize) -{ - int err; - struct crypto_cipher *essiv_tfm; - u8 salt[SHA256_DIGEST_SIZE]; - - essiv_tfm = crypto_alloc_cipher("aes", 0, 0); - if (IS_ERR(essiv_tfm)) - return PTR_ERR(essiv_tfm); - - ci->ci_essiv_tfm = essiv_tfm; - - err = derive_essiv_salt(raw_key, keysize, salt); - if (err) - goto out; - - /* - * Using SHA256 to derive the salt/key will result in AES-256 being - * used for IV generation. File contents encryption will still use the - * configured keysize (AES-128) nevertheless. - */ - err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt)); - if (err) - goto out; - -out: - memzero_explicit(salt, sizeof(salt)); - return err; -} - -void __exit fscrypt_essiv_cleanup(void) -{ - crypto_free_shash(essiv_hash_tfm); -} - -/* - * Given the encryption mode and key (normally the derived key, but for - * FS_POLICY_FLAG_DIRECT_KEY mode it's the master key), set up the inode's - * symmetric cipher transform object(s). - */ -static int setup_crypto_transform(struct fscrypt_info *ci, - struct fscrypt_mode *mode, - const u8 *raw_key, const struct inode *inode) -{ - struct fscrypt_master_key *mk; - struct crypto_skcipher *ctfm; - int err; - - if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY) { - mk = fscrypt_get_master_key(ci, mode, raw_key, inode); - if (IS_ERR(mk)) - return PTR_ERR(mk); - ctfm = mk->mk_ctfm; - } else { - mk = NULL; - ctfm = allocate_skcipher_for_mode(mode, raw_key, inode); - if (IS_ERR(ctfm)) - return PTR_ERR(ctfm); - } - ci->ci_master_key = mk; - ci->ci_ctfm = ctfm; - - if (mode->needs_essiv) { - /* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */ - WARN_ON(mode->ivsize != AES_BLOCK_SIZE); - WARN_ON(ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY); - - err = init_essiv_generator(ci, raw_key, mode->keysize); - if (err) { - fscrypt_warn(inode->i_sb, - "error initializing ESSIV generator for inode %lu: %d", - inode->i_ino, err); - return err; - } - } - return 0; -} - -static void put_crypt_info(struct fscrypt_info *ci) -{ - if (!ci) - return; - - if (ci->ci_master_key) { - put_master_key(ci->ci_master_key); - } else { - crypto_free_skcipher(ci->ci_ctfm); - crypto_free_cipher(ci->ci_essiv_tfm); - } - kmem_cache_free(fscrypt_info_cachep, ci); -} - -int fscrypt_get_encryption_info(struct inode *inode) -{ - struct fscrypt_info *crypt_info; - struct fscrypt_context ctx; - struct fscrypt_mode *mode; - u8 *raw_key = NULL; - int res; - - if (fscrypt_has_encryption_key(inode)) - return 0; - - res = fscrypt_initialize(inode->i_sb->s_cop->flags); - if (res) - return res; - - res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); - if (res < 0) { - if (!fscrypt_dummy_context_enabled(inode) || - IS_ENCRYPTED(inode)) - return res; - /* Fake up a context for an unencrypted directory */ - memset(&ctx, 0, sizeof(ctx)); - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS; - ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS; - memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE); - } else if (res != sizeof(ctx)) { - return -EINVAL; - } - - if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) - return -EINVAL; - - if (ctx.flags & ~FS_POLICY_FLAGS_VALID) - return -EINVAL; - - crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS); - if (!crypt_info) - return -ENOMEM; - - crypt_info->ci_flags = ctx.flags; - crypt_info->ci_data_mode = ctx.contents_encryption_mode; - crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; - memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE); - memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); - - mode = select_encryption_mode(crypt_info, inode); - if (IS_ERR(mode)) { - res = PTR_ERR(mode); - goto out; - } - WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE); - crypt_info->ci_mode = mode; - - /* - * This cannot be a stack buffer because it may be passed to the - * scatterlist crypto API as part of key derivation. - */ - res = -ENOMEM; - raw_key = kmalloc(mode->keysize, GFP_NOFS); - if (!raw_key) - goto out; - - res = find_and_derive_key(inode, &ctx, raw_key, mode); - if (res) - goto out; - - res = setup_crypto_transform(crypt_info, mode, raw_key, inode); - if (res) - goto out; - - if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) - crypt_info = NULL; -out: - if (res == -ENOKEY) - res = 0; - put_crypt_info(crypt_info); - kzfree(raw_key); - return res; -} -EXPORT_SYMBOL(fscrypt_get_encryption_info); - -/** - * fscrypt_put_encryption_info - free most of an inode's fscrypt data - * - * Free the inode's fscrypt_info. Filesystems must call this when the inode is - * being evicted. An RCU grace period need not have elapsed yet. - */ -void fscrypt_put_encryption_info(struct inode *inode) -{ - put_crypt_info(inode->i_crypt_info); - inode->i_crypt_info = NULL; -} -EXPORT_SYMBOL(fscrypt_put_encryption_info); - -/** - * fscrypt_free_inode - free an inode's fscrypt data requiring RCU delay - * - * Free the inode's cached decrypted symlink target, if any. Filesystems must - * call this after an RCU grace period, just before they free the inode. - */ -void fscrypt_free_inode(struct inode *inode) -{ - if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { - kfree(inode->i_link); - inode->i_link = NULL; - } -} -EXPORT_SYMBOL(fscrypt_free_inode); diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c new file mode 100644 index 000000000000..c34fa7c61b43 --- /dev/null +++ b/fs/crypto/keyring.c @@ -0,0 +1,984 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Filesystem-level keyring for fscrypt + * + * Copyright 2019 Google LLC + */ + +/* + * This file implements management of fscrypt master keys in the + * filesystem-level keyring, including the ioctls: + * + * - FS_IOC_ADD_ENCRYPTION_KEY + * - FS_IOC_REMOVE_ENCRYPTION_KEY + * - FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS + * - FS_IOC_GET_ENCRYPTION_KEY_STATUS + * + * See the "User API" section of Documentation/filesystems/fscrypt.rst for more + * information about these ioctls. + */ + +#include <crypto/skcipher.h> +#include <linux/key-type.h> +#include <linux/seq_file.h> + +#include "fscrypt_private.h" + +static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret) +{ + fscrypt_destroy_hkdf(&secret->hkdf); + memzero_explicit(secret, sizeof(*secret)); +} + +static void move_master_key_secret(struct fscrypt_master_key_secret *dst, + struct fscrypt_master_key_secret *src) +{ + memcpy(dst, src, sizeof(*dst)); + memzero_explicit(src, sizeof(*src)); +} + +static void free_master_key(struct fscrypt_master_key *mk) +{ + size_t i; + + wipe_master_key_secret(&mk->mk_secret); + + for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++) + crypto_free_skcipher(mk->mk_mode_keys[i]); + + key_put(mk->mk_users); + kzfree(mk); +} + +static inline bool valid_key_spec(const struct fscrypt_key_specifier *spec) +{ + if (spec->__reserved) + return false; + return master_key_spec_len(spec) != 0; +} + +static int fscrypt_key_instantiate(struct key *key, + struct key_preparsed_payload *prep) +{ + key->payload.data[0] = (struct fscrypt_master_key *)prep->data; + return 0; +} + +static void fscrypt_key_destroy(struct key *key) +{ + free_master_key(key->payload.data[0]); +} + +static void fscrypt_key_describe(const struct key *key, struct seq_file *m) +{ + seq_puts(m, key->description); + + if (key_is_positive(key)) { + const struct fscrypt_master_key *mk = key->payload.data[0]; + + if (!is_master_key_secret_present(&mk->mk_secret)) + seq_puts(m, ": secret removed"); + } +} + +/* + * Type of key in ->s_master_keys. Each key of this type represents a master + * key which has been added to the filesystem. Its payload is a + * 'struct fscrypt_master_key'. The "." prefix in the key type name prevents + * users from adding keys of this type via the keyrings syscalls rather than via + * the intended method of FS_IOC_ADD_ENCRYPTION_KEY. + */ +static struct key_type key_type_fscrypt = { + .name = "._fscrypt", + .instantiate = fscrypt_key_instantiate, + .destroy = fscrypt_key_destroy, + .describe = fscrypt_key_describe, +}; + +static int fscrypt_user_key_instantiate(struct key *key, + struct key_preparsed_payload *prep) +{ + /* + * We just charge FSCRYPT_MAX_KEY_SIZE bytes to the user's key quota for + * each key, regardless of the exact key size. The amount of memory + * actually used is greater than the size of the raw key anyway. + */ + return key_payload_reserve(key, FSCRYPT_MAX_KEY_SIZE); +} + +static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m) +{ + seq_puts(m, key->description); +} + +/* + * Type of key in ->mk_users. Each key of this type represents a particular + * user who has added a particular master key. + * + * Note that the name of this key type really should be something like + * ".fscrypt-user" instead of simply ".fscrypt". But the shorter name is chosen + * mainly for simplicity of presentation in /proc/keys when read by a non-root + * user. And it is expected to be rare that a key is actually added by multiple + * users, since users should keep their encryption keys confidential. + */ +static struct key_type key_type_fscrypt_user = { + .name = ".fscrypt", + .instantiate = fscrypt_user_key_instantiate, + .describe = fscrypt_user_key_describe, +}; + +/* Search ->s_master_keys or ->mk_users */ +static struct key *search_fscrypt_keyring(struct key *keyring, + struct key_type *type, + const char *description) +{ + /* + * We need to mark the keyring reference as "possessed" so that we + * acquire permission to search it, via the KEY_POS_SEARCH permission. + */ + key_ref_t keyref = make_key_ref(keyring, true /* possessed */); + + keyref = keyring_search(keyref, type, description, false); + if (IS_ERR(keyref)) { + if (PTR_ERR(keyref) == -EAGAIN || /* not found */ + PTR_ERR(keyref) == -EKEYREVOKED) /* recently invalidated */ + keyref = ERR_PTR(-ENOKEY); + return ERR_CAST(keyref); + } + return key_ref_to_ptr(keyref); +} + +#define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE \ + (CONST_STRLEN("fscrypt-") + FIELD_SIZEOF(struct super_block, s_id)) + +#define FSCRYPT_MK_DESCRIPTION_SIZE (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + 1) + +#define FSCRYPT_MK_USERS_DESCRIPTION_SIZE \ + (CONST_STRLEN("fscrypt-") + 2 * FSCRYPT_KEY_IDENTIFIER_SIZE + \ + CONST_STRLEN("-users") + 1) + +#define FSCRYPT_MK_USER_DESCRIPTION_SIZE \ + (2 * FSCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1) + +static void format_fs_keyring_description( + char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE], + const struct super_block *sb) +{ + sprintf(description, "fscrypt-%s", sb->s_id); +} + +static void format_mk_description( + char description[FSCRYPT_MK_DESCRIPTION_SIZE], + const struct fscrypt_key_specifier *mk_spec) +{ + sprintf(description, "%*phN", + master_key_spec_len(mk_spec), (u8 *)&mk_spec->u); +} + +static void format_mk_users_keyring_description( + char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE], + const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) +{ + sprintf(description, "fscrypt-%*phN-users", + FSCRYPT_KEY_IDENTIFIER_SIZE, mk_identifier); +} + +static void format_mk_user_description( + char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE], + const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) +{ + + sprintf(description, "%*phN.uid.%u", FSCRYPT_KEY_IDENTIFIER_SIZE, + mk_identifier, __kuid_val(current_fsuid())); +} + +/* Create ->s_master_keys if needed. Synchronized by fscrypt_add_key_mutex. */ +static int allocate_filesystem_keyring(struct super_block *sb) +{ + char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE]; + struct key *keyring; + + if (sb->s_master_keys) + return 0; + + format_fs_keyring_description(description, sb); + keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, + current_cred(), KEY_POS_SEARCH | + KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW, + KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); + if (IS_ERR(keyring)) + return PTR_ERR(keyring); + + /* Pairs with READ_ONCE() in fscrypt_find_master_key() */ + smp_store_release(&sb->s_master_keys, keyring); + return 0; +} + +void fscrypt_sb_free(struct super_block *sb) +{ + key_put(sb->s_master_keys); + sb->s_master_keys = NULL; +} + +/* + * Find the specified master key in ->s_master_keys. + * Returns ERR_PTR(-ENOKEY) if not found. + */ +struct key *fscrypt_find_master_key(struct super_block *sb, + const struct fscrypt_key_specifier *mk_spec) +{ + struct key *keyring; + char description[FSCRYPT_MK_DESCRIPTION_SIZE]; + + /* pairs with smp_store_release() in allocate_filesystem_keyring() */ + keyring = READ_ONCE(sb->s_master_keys); + if (keyring == NULL) + return ERR_PTR(-ENOKEY); /* No keyring yet, so no keys yet. */ + + format_mk_description(description, mk_spec); + return search_fscrypt_keyring(keyring, &key_type_fscrypt, description); +} + +static int allocate_master_key_users_keyring(struct fscrypt_master_key *mk) +{ + char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE]; + struct key *keyring; + + format_mk_users_keyring_description(description, + mk->mk_spec.u.identifier); + keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, + current_cred(), KEY_POS_SEARCH | + KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW, + KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); + if (IS_ERR(keyring)) + return PTR_ERR(keyring); + + mk->mk_users = keyring; + return 0; +} + +/* + * Find the current user's "key" in the master key's ->mk_users. + * Returns ERR_PTR(-ENOKEY) if not found. + */ +static struct key *find_master_key_user(struct fscrypt_master_key *mk) +{ + char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE]; + + format_mk_user_description(description, mk->mk_spec.u.identifier); + return search_fscrypt_keyring(mk->mk_users, &key_type_fscrypt_user, + description); +} + +/* + * Give the current user a "key" in ->mk_users. This charges the user's quota + * and marks the master key as added by the current user, so that it cannot be + * removed by another user with the key. Either the master key's key->sem must + * be held for write, or the master key must be still undergoing initialization. + */ +static int add_master_key_user(struct fscrypt_master_key *mk) +{ + char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE]; + struct key *mk_user; + int err; + + format_mk_user_description(description, mk->mk_spec.u.identifier); + mk_user = key_alloc(&key_type_fscrypt_user, description, + current_fsuid(), current_gid(), current_cred(), + KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL); + if (IS_ERR(mk_user)) + return PTR_ERR(mk_user); + + err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL); + key_put(mk_user); + return err; +} + +/* + * Remove the current user's "key" from ->mk_users. + * The master key's key->sem must be held for write. + * + * Returns 0 if removed, -ENOKEY if not found, or another -errno code. + */ +static int remove_master_key_user(struct fscrypt_master_key *mk) +{ + struct key *mk_user; + int err; + + mk_user = find_master_key_user(mk); + if (IS_ERR(mk_user)) + return PTR_ERR(mk_user); + err = key_unlink(mk->mk_users, mk_user); + key_put(mk_user); + return err; +} + +/* + * Allocate a new fscrypt_master_key which contains the given secret, set it as + * the payload of a new 'struct key' of type fscrypt, and link the 'struct key' + * into the given keyring. Synchronized by fscrypt_add_key_mutex. + */ +static int add_new_master_key(struct fscrypt_master_key_secret *secret, + const struct fscrypt_key_specifier *mk_spec, + struct key *keyring) +{ + struct fscrypt_master_key *mk; + char description[FSCRYPT_MK_DESCRIPTION_SIZE]; + struct key *key; + int err; + + mk = kzalloc(sizeof(*mk), GFP_KERNEL); + if (!mk) + return -ENOMEM; + + mk->mk_spec = *mk_spec; + + move_master_key_secret(&mk->mk_secret, secret); + init_rwsem(&mk->mk_secret_sem); + + refcount_set(&mk->mk_refcount, 1); /* secret is present */ + INIT_LIST_HEAD(&mk->mk_decrypted_inodes); + spin_lock_init(&mk->mk_decrypted_inodes_lock); + + if (mk_spec->type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) { + err = allocate_master_key_users_keyring(mk); + if (err) + goto out_free_mk; + err = add_master_key_user(mk); + if (err) + goto out_free_mk; + } + + /* + * Note that we don't charge this key to anyone's quota, since when + * ->mk_users is in use those keys are charged instead, and otherwise + * (when ->mk_users isn't in use) only root can add these keys. + */ + format_mk_description(description, mk_spec); + key = key_alloc(&key_type_fscrypt, description, + GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(), + KEY_POS_SEARCH | KEY_USR_SEARCH | KEY_USR_VIEW, + KEY_ALLOC_NOT_IN_QUOTA, NULL); + if (IS_ERR(key)) { + err = PTR_ERR(key); + goto out_free_mk; + } + err = key_instantiate_and_link(key, mk, sizeof(*mk), keyring, NULL); + key_put(key); + if (err) + goto out_free_mk; + + return 0; + +out_free_mk: + free_master_key(mk); + return err; +} + +#define KEY_DEAD 1 + +static int add_existing_master_key(struct fscrypt_master_key *mk, + struct fscrypt_master_key_secret *secret) +{ + struct key *mk_user; + bool rekey; + int err; + + /* + * If the current user is already in ->mk_users, then there's nothing to + * do. (Not applicable for v1 policy keys, which have NULL ->mk_users.) + */ + if (mk->mk_users) { + mk_user = find_master_key_user(mk); + if (mk_user != ERR_PTR(-ENOKEY)) { + if (IS_ERR(mk_user)) + return PTR_ERR(mk_user); + key_put(mk_user); + return 0; + } + } + + /* If we'll be re-adding ->mk_secret, try to take the reference. */ + rekey = !is_master_key_secret_present(&mk->mk_secret); + if (rekey && !refcount_inc_not_zero(&mk->mk_refcount)) + return KEY_DEAD; + + /* Add the current user to ->mk_users, if applicable. */ + if (mk->mk_users) { + err = add_master_key_user(mk); + if (err) { + if (rekey && refcount_dec_and_test(&mk->mk_refcount)) + return KEY_DEAD; + return err; + } + } + + /* Re-add the secret if needed. */ + if (rekey) { + down_write(&mk->mk_secret_sem); + move_master_key_secret(&mk->mk_secret, secret); + up_write(&mk->mk_secret_sem); + } + return 0; +} + +static int add_master_key(struct super_block *sb, + struct fscrypt_master_key_secret *secret, + const struct fscrypt_key_specifier *mk_spec) +{ + static DEFINE_MUTEX(fscrypt_add_key_mutex); + struct key *key; + int err; + + mutex_lock(&fscrypt_add_key_mutex); /* serialize find + link */ +retry: + key = fscrypt_find_master_key(sb, mk_spec); + if (IS_ERR(key)) { + err = PTR_ERR(key); + if (err != -ENOKEY) + goto out_unlock; + /* Didn't find the key in ->s_master_keys. Add it. */ + err = allocate_filesystem_keyring(sb); + if (err) + goto out_unlock; + err = add_new_master_key(secret, mk_spec, sb->s_master_keys); + } else { + /* + * Found the key in ->s_master_keys. Re-add the secret if + * needed, and add the user to ->mk_users if needed. + */ + down_write(&key->sem); + err = add_existing_master_key(key->payload.data[0], secret); + up_write(&key->sem); + if (err == KEY_DEAD) { + /* Key being removed or needs to be removed */ + key_invalidate(key); + key_put(key); + goto retry; + } + key_put(key); + } +out_unlock: + mutex_unlock(&fscrypt_add_key_mutex); + return err; +} + +/* + * Add a master encryption key to the filesystem, causing all files which were + * encrypted with it to appear "unlocked" (decrypted) when accessed. + * + * When adding a key for use by v1 encryption policies, this ioctl is + * privileged, and userspace must provide the 'key_descriptor'. + * + * When adding a key for use by v2+ encryption policies, this ioctl is + * unprivileged. This is needed, in general, to allow non-root users to use + * encryption without encountering the visibility problems of process-subscribed + * keyrings and the inability to properly remove keys. This works by having + * each key identified by its cryptographically secure hash --- the + * 'key_identifier'. The cryptographic hash ensures that a malicious user + * cannot add the wrong key for a given identifier. Furthermore, each added key + * is charged to the appropriate user's quota for the keyrings service, which + * prevents a malicious user from adding too many keys. Finally, we forbid a + * user from removing a key while other users have added it too, which prevents + * a user who knows another user's key from causing a denial-of-service by + * removing it at an inopportune time. (We tolerate that a user who knows a key + * can prevent other users from removing it.) + * + * For more details, see the "FS_IOC_ADD_ENCRYPTION_KEY" section of + * Documentation/filesystems/fscrypt.rst. + */ +int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg) +{ + struct super_block *sb = file_inode(filp)->i_sb; + struct fscrypt_add_key_arg __user *uarg = _uarg; + struct fscrypt_add_key_arg arg; + struct fscrypt_master_key_secret secret; + int err; + + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + + if (!valid_key_spec(&arg.key_spec)) + return -EINVAL; + + if (arg.raw_size < FSCRYPT_MIN_KEY_SIZE || + arg.raw_size > FSCRYPT_MAX_KEY_SIZE) + return -EINVAL; + + if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved))) + return -EINVAL; + + memset(&secret, 0, sizeof(secret)); + secret.size = arg.raw_size; + err = -EFAULT; + if (copy_from_user(secret.raw, uarg->raw, secret.size)) + goto out_wipe_secret; + + switch (arg.key_spec.type) { + case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR: + /* + * Only root can add keys that are identified by an arbitrary + * descriptor rather than by a cryptographic hash --- since + * otherwise a malicious user could add the wrong key. + */ + err = -EACCES; + if (!capable(CAP_SYS_ADMIN)) + goto out_wipe_secret; + break; + case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER: + err = fscrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size); + if (err) + goto out_wipe_secret; + + /* + * Now that the HKDF context is initialized, the raw key is no + * longer needed. + */ + memzero_explicit(secret.raw, secret.size); + + /* Calculate the key identifier and return it to userspace. */ + err = fscrypt_hkdf_expand(&secret.hkdf, + HKDF_CONTEXT_KEY_IDENTIFIER, + NULL, 0, arg.key_spec.u.identifier, + FSCRYPT_KEY_IDENTIFIER_SIZE); + if (err) + goto out_wipe_secret; + err = -EFAULT; + if (copy_to_user(uarg->key_spec.u.identifier, + arg.key_spec.u.identifier, + FSCRYPT_KEY_IDENTIFIER_SIZE)) + goto out_wipe_secret; + break; + default: + WARN_ON(1); + err = -EINVAL; + goto out_wipe_secret; + } + + err = add_master_key(sb, &secret, &arg.key_spec); +out_wipe_secret: + wipe_master_key_secret(&secret); + return err; +} +EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key); + +/* + * Verify that the current user has added a master key with the given identifier + * (returns -ENOKEY if not). This is needed to prevent a user from encrypting + * their files using some other user's key which they don't actually know. + * Cryptographically this isn't much of a problem, but the semantics of this + * would be a bit weird, so it's best to just forbid it. + * + * The system administrator (CAP_FOWNER) can override this, which should be + * enough for any use cases where encryption policies are being set using keys + * that were chosen ahead of time but aren't available at the moment. + * + * Note that the key may have already removed by the time this returns, but + * that's okay; we just care whether the key was there at some point. + * + * Return: 0 if the key is added, -ENOKEY if it isn't, or another -errno code + */ +int fscrypt_verify_key_added(struct super_block *sb, + const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]) +{ + struct fscrypt_key_specifier mk_spec; + struct key *key, *mk_user; + struct fscrypt_master_key *mk; + int err; + + mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER; + memcpy(mk_spec.u.identifier, identifier, FSCRYPT_KEY_IDENTIFIER_SIZE); + + key = fscrypt_find_master_key(sb, &mk_spec); + if (IS_ERR(key)) { + err = PTR_ERR(key); + goto out; + } + mk = key->payload.data[0]; + mk_user = find_master_key_user(mk); + if (IS_ERR(mk_user)) { + err = PTR_ERR(mk_user); + } else { + key_put(mk_user); + err = 0; + } + key_put(key); +out: + if (err == -ENOKEY && capable(CAP_FOWNER)) + err = 0; + return err; +} + +/* + * Try to evict the inode's dentries from the dentry cache. If the inode is a + * directory, then it can have at most one dentry; however, that dentry may be + * pinned by child dentries, so first try to evict the children too. + */ +static void shrink_dcache_inode(struct inode *inode) +{ + struct dentry *dentry; + + if (S_ISDIR(inode->i_mode)) { + dentry = d_find_any_alias(inode); + if (dentry) { + shrink_dcache_parent(dentry); + dput(dentry); + } + } + d_prune_aliases(inode); +} + +static void evict_dentries_for_decrypted_inodes(struct fscrypt_master_key *mk) +{ + struct fscrypt_info *ci; + struct inode *inode; + struct inode *toput_inode = NULL; + + spin_lock(&mk->mk_decrypted_inodes_lock); + + list_for_each_entry(ci, &mk->mk_decrypted_inodes, ci_master_key_link) { + inode = ci->ci_inode; + spin_lock(&inode->i_lock); + if (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) { + spin_unlock(&inode->i_lock); + continue; + } + __iget(inode); + spin_unlock(&inode->i_lock); + spin_unlock(&mk->mk_decrypted_inodes_lock); + + shrink_dcache_inode(inode); + iput(toput_inode); + toput_inode = inode; + + spin_lock(&mk->mk_decrypted_inodes_lock); + } + + spin_unlock(&mk->mk_decrypted_inodes_lock); + iput(toput_inode); +} + +static int check_for_busy_inodes(struct super_block *sb, + struct fscrypt_master_key *mk) +{ + struct list_head *pos; + size_t busy_count = 0; + unsigned long ino; + struct dentry *dentry; + char _path[256]; + char *path = NULL; + + spin_lock(&mk->mk_decrypted_inodes_lock); + + list_for_each(pos, &mk->mk_decrypted_inodes) + busy_count++; + + if (busy_count == 0) { + spin_unlock(&mk->mk_decrypted_inodes_lock); + return 0; + } + + { + /* select an example file to show for debugging purposes */ + struct inode *inode = + list_first_entry(&mk->mk_decrypted_inodes, + struct fscrypt_info, + ci_master_key_link)->ci_inode; + ino = inode->i_ino; + dentry = d_find_alias(inode); + } + spin_unlock(&mk->mk_decrypted_inodes_lock); + + if (dentry) { + path = dentry_path(dentry, _path, sizeof(_path)); + dput(dentry); + } + if (IS_ERR_OR_NULL(path)) + path = "(unknown)"; + + fscrypt_warn(NULL, + "%s: %zu inode(s) still busy after removing key with %s %*phN, including ino %lu (%s)", + sb->s_id, busy_count, master_key_spec_type(&mk->mk_spec), + master_key_spec_len(&mk->mk_spec), (u8 *)&mk->mk_spec.u, + ino, path); + return -EBUSY; +} + +static int try_to_lock_encrypted_files(struct super_block *sb, + struct fscrypt_master_key *mk) +{ + int err1; + int err2; + + /* + * An inode can't be evicted while it is dirty or has dirty pages. + * Thus, we first have to clean the inodes in ->mk_decrypted_inodes. + * + * Just do it the easy way: call sync_filesystem(). It's overkill, but + * it works, and it's more important to minimize the amount of caches we + * drop than the amount of data we sync. Also, unprivileged users can + * already call sync_filesystem() via sys_syncfs() or sys_sync(). + */ + down_read(&sb->s_umount); + err1 = sync_filesystem(sb); + up_read(&sb->s_umount); + /* If a sync error occurs, still try to evict as much as possible. */ + + /* + * Inodes are pinned by their dentries, so we have to evict their + * dentries. shrink_dcache_sb() would suffice, but would be overkill + * and inappropriate for use by unprivileged users. So instead go + * through the inodes' alias lists and try to evict each dentry. + */ + evict_dentries_for_decrypted_inodes(mk); + + /* + * evict_dentries_for_decrypted_inodes() already iput() each inode in + * the list; any inodes for which that dropped the last reference will + * have been evicted due to fscrypt_drop_inode() detecting the key + * removal and telling the VFS to evict the inode. So to finish, we + * just need to check whether any inodes couldn't be evicted. + */ + err2 = check_for_busy_inodes(sb, mk); + + return err1 ?: err2; +} + +/* + * Try to remove an fscrypt master encryption key. + * + * FS_IOC_REMOVE_ENCRYPTION_KEY (all_users=false) removes the current user's + * claim to the key, then removes the key itself if no other users have claims. + * FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS (all_users=true) always removes the + * key itself. + * + * To "remove the key itself", first we wipe the actual master key secret, so + * that no more inodes can be unlocked with it. Then we try to evict all cached + * inodes that had been unlocked with the key. + * + * If all inodes were evicted, then we unlink the fscrypt_master_key from the + * keyring. Otherwise it remains in the keyring in the "incompletely removed" + * state (without the actual secret key) where it tracks the list of remaining + * inodes. Userspace can execute the ioctl again later to retry eviction, or + * alternatively can re-add the secret key again. + * + * For more details, see the "Removing keys" section of + * Documentation/filesystems/fscrypt.rst. + */ +static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users) +{ + struct super_block *sb = file_inode(filp)->i_sb; + struct fscrypt_remove_key_arg __user *uarg = _uarg; + struct fscrypt_remove_key_arg arg; + struct key *key; + struct fscrypt_master_key *mk; + u32 status_flags = 0; + int err; + bool dead; + + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + + if (!valid_key_spec(&arg.key_spec)) + return -EINVAL; + + if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved))) + return -EINVAL; + + /* + * Only root can add and remove keys that are identified by an arbitrary + * descriptor rather than by a cryptographic hash. + */ + if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR && + !capable(CAP_SYS_ADMIN)) + return -EACCES; + + /* Find the key being removed. */ + key = fscrypt_find_master_key(sb, &arg.key_spec); + if (IS_ERR(key)) + return PTR_ERR(key); + mk = key->payload.data[0]; + + down_write(&key->sem); + + /* If relevant, remove current user's (or all users) claim to the key */ + if (mk->mk_users && mk->mk_users->keys.nr_leaves_on_tree != 0) { + if (all_users) + err = keyring_clear(mk->mk_users); + else + err = remove_master_key_user(mk); + if (err) { + up_write(&key->sem); + goto out_put_key; + } + if (mk->mk_users->keys.nr_leaves_on_tree != 0) { + /* + * Other users have still added the key too. We removed + * the current user's claim to the key, but we still + * can't remove the key itself. + */ + status_flags |= + FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS; + err = 0; + up_write(&key->sem); + goto out_put_key; + } + } + + /* No user claims remaining. Go ahead and wipe the secret. */ + dead = false; + if (is_master_key_secret_present(&mk->mk_secret)) { + down_write(&mk->mk_secret_sem); + wipe_master_key_secret(&mk->mk_secret); + dead = refcount_dec_and_test(&mk->mk_refcount); + up_write(&mk->mk_secret_sem); + } + up_write(&key->sem); + if (dead) { + /* + * No inodes reference the key, and we wiped the secret, so the + * key object is free to be removed from the keyring. + */ + key_invalidate(key); + err = 0; + } else { + /* Some inodes still reference this key; try to evict them. */ + err = try_to_lock_encrypted_files(sb, mk); + if (err == -EBUSY) { + status_flags |= + FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY; + err = 0; + } + } + /* + * We return 0 if we successfully did something: removed a claim to the + * key, wiped the secret, or tried locking the files again. Users need + * to check the informational status flags if they care whether the key + * has been fully removed including all files locked. + */ +out_put_key: + key_put(key); + if (err == 0) + err = put_user(status_flags, &uarg->removal_status_flags); + return err; +} + +int fscrypt_ioctl_remove_key(struct file *filp, void __user *uarg) +{ + return do_remove_key(filp, uarg, false); +} +EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key); + +int fscrypt_ioctl_remove_key_all_users(struct file *filp, void __user *uarg) +{ + if (!capable(CAP_SYS_ADMIN)) + return -EACCES; + return do_remove_key(filp, uarg, true); +} +EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key_all_users); + +/* + * Retrieve the status of an fscrypt master encryption key. + * + * We set ->status to indicate whether the key is absent, present, or + * incompletely removed. "Incompletely removed" means that the master key + * secret has been removed, but some files which had been unlocked with it are + * still in use. This field allows applications to easily determine the state + * of an encrypted directory without using a hack such as trying to open a + * regular file in it (which can confuse the "incompletely removed" state with + * absent or present). + * + * In addition, for v2 policy keys we allow applications to determine, via + * ->status_flags and ->user_count, whether the key has been added by the + * current user, by other users, or by both. Most applications should not need + * this, since ordinarily only one user should know a given key. However, if a + * secret key is shared by multiple users, applications may wish to add an + * already-present key to prevent other users from removing it. This ioctl can + * be used to check whether that really is the case before the work is done to + * add the key --- which might e.g. require prompting the user for a passphrase. + * + * For more details, see the "FS_IOC_GET_ENCRYPTION_KEY_STATUS" section of + * Documentation/filesystems/fscrypt.rst. + */ +int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg) +{ + struct super_block *sb = file_inode(filp)->i_sb; + struct fscrypt_get_key_status_arg arg; + struct key *key; + struct fscrypt_master_key *mk; + int err; + + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + + if (!valid_key_spec(&arg.key_spec)) + return -EINVAL; + + if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved))) + return -EINVAL; + + arg.status_flags = 0; + arg.user_count = 0; + memset(arg.__out_reserved, 0, sizeof(arg.__out_reserved)); + + key = fscrypt_find_master_key(sb, &arg.key_spec); + if (IS_ERR(key)) { + if (key != ERR_PTR(-ENOKEY)) + return PTR_ERR(key); + arg.status = FSCRYPT_KEY_STATUS_ABSENT; + err = 0; + goto out; + } + mk = key->payload.data[0]; + down_read(&key->sem); + + if (!is_master_key_secret_present(&mk->mk_secret)) { + arg.status = FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED; + err = 0; + goto out_release_key; + } + + arg.status = FSCRYPT_KEY_STATUS_PRESENT; + if (mk->mk_users) { + struct key *mk_user; + + arg.user_count = mk->mk_users->keys.nr_leaves_on_tree; + mk_user = find_master_key_user(mk); + if (!IS_ERR(mk_user)) { + arg.status_flags |= + FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF; + key_put(mk_user); + } else if (mk_user != ERR_PTR(-ENOKEY)) { + err = PTR_ERR(mk_user); + goto out_release_key; + } + } + err = 0; +out_release_key: + up_read(&key->sem); + key_put(key); +out: + if (!err && copy_to_user(uarg, &arg, sizeof(arg))) + err = -EFAULT; + return err; +} +EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_key_status); + +int __init fscrypt_init_keyring(void) +{ + int err; + + err = register_key_type(&key_type_fscrypt); + if (err) + return err; + + err = register_key_type(&key_type_fscrypt_user); + if (err) + goto err_unregister_fscrypt; + + return 0; + +err_unregister_fscrypt: + unregister_key_type(&key_type_fscrypt); + return err; +} diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c new file mode 100644 index 000000000000..d71c2d6dd162 --- /dev/null +++ b/fs/crypto/keysetup.c @@ -0,0 +1,591 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Key setup facility for FS encryption support. + * + * Copyright (C) 2015, Google, Inc. + * + * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar. + * Heavily modified since then. + */ + +#include <crypto/aes.h> +#include <crypto/sha.h> +#include <crypto/skcipher.h> +#include <linux/key.h> + +#include "fscrypt_private.h" + +static struct crypto_shash *essiv_hash_tfm; + +static struct fscrypt_mode available_modes[] = { + [FSCRYPT_MODE_AES_256_XTS] = { + .friendly_name = "AES-256-XTS", + .cipher_str = "xts(aes)", + .keysize = 64, + .ivsize = 16, + }, + [FSCRYPT_MODE_AES_256_CTS] = { + .friendly_name = "AES-256-CTS-CBC", + .cipher_str = "cts(cbc(aes))", + .keysize = 32, + .ivsize = 16, + }, + [FSCRYPT_MODE_AES_128_CBC] = { + .friendly_name = "AES-128-CBC", + .cipher_str = "cbc(aes)", + .keysize = 16, + .ivsize = 16, + .needs_essiv = true, + }, + [FSCRYPT_MODE_AES_128_CTS] = { + .friendly_name = "AES-128-CTS-CBC", + .cipher_str = "cts(cbc(aes))", + .keysize = 16, + .ivsize = 16, + }, + [FSCRYPT_MODE_ADIANTUM] = { + .friendly_name = "Adiantum", + .cipher_str = "adiantum(xchacha12,aes)", + .keysize = 32, + .ivsize = 32, + }, +}; + +static struct fscrypt_mode * +select_encryption_mode(const union fscrypt_policy *policy, + const struct inode *inode) +{ + if (S_ISREG(inode->i_mode)) + return &available_modes[fscrypt_policy_contents_mode(policy)]; + + if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) + return &available_modes[fscrypt_policy_fnames_mode(policy)]; + + WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", + inode->i_ino, (inode->i_mode & S_IFMT)); + return ERR_PTR(-EINVAL); +} + +/* Create a symmetric cipher object for the given encryption mode and key */ +struct crypto_skcipher *fscrypt_allocate_skcipher(struct fscrypt_mode *mode, + const u8 *raw_key, + const struct inode *inode) +{ + struct crypto_skcipher *tfm; + int err; + + tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); + if (IS_ERR(tfm)) { + if (PTR_ERR(tfm) == -ENOENT) { + fscrypt_warn(inode, + "Missing crypto API support for %s (API name: \"%s\")", + mode->friendly_name, mode->cipher_str); + return ERR_PTR(-ENOPKG); + } + fscrypt_err(inode, "Error allocating '%s' transform: %ld", + mode->cipher_str, PTR_ERR(tfm)); + return tfm; + } + if (unlikely(!mode->logged_impl_name)) { + /* + * fscrypt performance can vary greatly depending on which + * crypto algorithm implementation is used. Help people debug + * performance problems by logging the ->cra_driver_name the + * first time a mode is used. Note that multiple threads can + * race here, but it doesn't really matter. + */ + mode->logged_impl_name = true; + pr_info("fscrypt: %s using implementation \"%s\"\n", + mode->friendly_name, + crypto_skcipher_alg(tfm)->base.cra_driver_name); + } + crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); + err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize); + if (err) + goto err_free_tfm; + + return tfm; + +err_free_tfm: + crypto_free_skcipher(tfm); + return ERR_PTR(err); +} + +static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt) +{ + struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm); + + /* init hash transform on demand */ + if (unlikely(!tfm)) { + struct crypto_shash *prev_tfm; + + tfm = crypto_alloc_shash("sha256", 0, 0); + if (IS_ERR(tfm)) { + if (PTR_ERR(tfm) == -ENOENT) { + fscrypt_warn(NULL, + "Missing crypto API support for SHA-256"); + return -ENOPKG; + } + fscrypt_err(NULL, + "Error allocating SHA-256 transform: %ld", + PTR_ERR(tfm)); + return PTR_ERR(tfm); + } + prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm); + if (prev_tfm) { + crypto_free_shash(tfm); + tfm = prev_tfm; + } + } + + { + SHASH_DESC_ON_STACK(desc, tfm); + desc->tfm = tfm; + + return crypto_shash_digest(desc, key, keysize, salt); + } +} + +static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key, + int keysize) +{ + int err; + struct crypto_cipher *essiv_tfm; + u8 salt[SHA256_DIGEST_SIZE]; + + if (WARN_ON(ci->ci_mode->ivsize != AES_BLOCK_SIZE)) + return -EINVAL; + + essiv_tfm = crypto_alloc_cipher("aes", 0, 0); + if (IS_ERR(essiv_tfm)) + return PTR_ERR(essiv_tfm); + + ci->ci_essiv_tfm = essiv_tfm; + + err = derive_essiv_salt(raw_key, keysize, salt); + if (err) + goto out; + + /* + * Using SHA256 to derive the salt/key will result in AES-256 being + * used for IV generation. File contents encryption will still use the + * configured keysize (AES-128) nevertheless. + */ + err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt)); + if (err) + goto out; + +out: + memzero_explicit(salt, sizeof(salt)); + return err; +} + +/* Given the per-file key, set up the file's crypto transform object(s) */ +int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key) +{ + struct fscrypt_mode *mode = ci->ci_mode; + struct crypto_skcipher *ctfm; + int err; + + ctfm = fscrypt_allocate_skcipher(mode, derived_key, ci->ci_inode); + if (IS_ERR(ctfm)) + return PTR_ERR(ctfm); + + ci->ci_ctfm = ctfm; + + if (mode->needs_essiv) { + err = init_essiv_generator(ci, derived_key, mode->keysize); + if (err) { + fscrypt_warn(ci->ci_inode, + "Error initializing ESSIV generator: %d", + err); + return err; + } + } + return 0; +} + +static int setup_per_mode_key(struct fscrypt_info *ci, + struct fscrypt_master_key *mk) +{ + struct fscrypt_mode *mode = ci->ci_mode; + u8 mode_num = mode - available_modes; + struct crypto_skcipher *tfm, *prev_tfm; + u8 mode_key[FSCRYPT_MAX_KEY_SIZE]; + int err; + + if (WARN_ON(mode_num >= ARRAY_SIZE(mk->mk_mode_keys))) + return -EINVAL; + + /* pairs with cmpxchg() below */ + tfm = READ_ONCE(mk->mk_mode_keys[mode_num]); + if (likely(tfm != NULL)) + goto done; + + BUILD_BUG_ON(sizeof(mode_num) != 1); + err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, + HKDF_CONTEXT_PER_MODE_KEY, + &mode_num, sizeof(mode_num), + mode_key, mode->keysize); + if (err) + return err; + tfm = fscrypt_allocate_skcipher(mode, mode_key, ci->ci_inode); + memzero_explicit(mode_key, mode->keysize); + if (IS_ERR(tfm)) + return PTR_ERR(tfm); + + /* pairs with READ_ONCE() above */ + prev_tfm = cmpxchg(&mk->mk_mode_keys[mode_num], NULL, tfm); + if (prev_tfm != NULL) { + crypto_free_skcipher(tfm); + tfm = prev_tfm; + } +done: + ci->ci_ctfm = tfm; + return 0; +} + +static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, + struct fscrypt_master_key *mk) +{ + u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; + int err; + + if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { + /* + * DIRECT_KEY: instead of deriving per-file keys, the per-file + * nonce will be included in all the IVs. But unlike v1 + * policies, for v2 policies in this case we don't encrypt with + * the master key directly but rather derive a per-mode key. + * This ensures that the master key is consistently used only + * for HKDF, avoiding key reuse issues. + */ + if (!fscrypt_mode_supports_direct_key(ci->ci_mode)) { + fscrypt_warn(ci->ci_inode, + "Direct key flag not allowed with %s", + ci->ci_mode->friendly_name); + return -EINVAL; + } + return setup_per_mode_key(ci, mk); + } + + err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, + HKDF_CONTEXT_PER_FILE_KEY, + ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE, + derived_key, ci->ci_mode->keysize); + if (err) + return err; + + err = fscrypt_set_derived_key(ci, derived_key); + memzero_explicit(derived_key, ci->ci_mode->keysize); + return err; +} + +/* + * Find the master key, then set up the inode's actual encryption key. + * + * If the master key is found in the filesystem-level keyring, then the + * corresponding 'struct key' is returned in *master_key_ret with + * ->mk_secret_sem read-locked. This is needed to ensure that only one task + * links the fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race + * to create an fscrypt_info for the same inode), and to synchronize the master + * key being removed with a new inode starting to use it. + */ +static int setup_file_encryption_key(struct fscrypt_info *ci, + struct key **master_key_ret) +{ + struct key *key; + struct fscrypt_master_key *mk = NULL; + struct fscrypt_key_specifier mk_spec; + int err; + + switch (ci->ci_policy.version) { + case FSCRYPT_POLICY_V1: + mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR; + memcpy(mk_spec.u.descriptor, + ci->ci_policy.v1.master_key_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + break; + case FSCRYPT_POLICY_V2: + mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER; + memcpy(mk_spec.u.identifier, + ci->ci_policy.v2.master_key_identifier, + FSCRYPT_KEY_IDENTIFIER_SIZE); + break; + default: + WARN_ON(1); + return -EINVAL; + } + + key = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec); + if (IS_ERR(key)) { + if (key != ERR_PTR(-ENOKEY) || + ci->ci_policy.version != FSCRYPT_POLICY_V1) + return PTR_ERR(key); + + /* + * As a legacy fallback for v1 policies, search for the key in + * the current task's subscribed keyrings too. Don't move this + * to before the search of ->s_master_keys, since users + * shouldn't be able to override filesystem-level keys. + */ + return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); + } + + mk = key->payload.data[0]; + down_read(&mk->mk_secret_sem); + + /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */ + if (!is_master_key_secret_present(&mk->mk_secret)) { + err = -ENOKEY; + goto out_release_key; + } + + /* + * Require that the master key be at least as long as the derived key. + * Otherwise, the derived key cannot possibly contain as much entropy as + * that required by the encryption mode it will be used for. For v1 + * policies it's also required for the KDF to work at all. + */ + if (mk->mk_secret.size < ci->ci_mode->keysize) { + fscrypt_warn(NULL, + "key with %s %*phN is too short (got %u bytes, need %u+ bytes)", + master_key_spec_type(&mk_spec), + master_key_spec_len(&mk_spec), (u8 *)&mk_spec.u, + mk->mk_secret.size, ci->ci_mode->keysize); + err = -ENOKEY; + goto out_release_key; + } + + switch (ci->ci_policy.version) { + case FSCRYPT_POLICY_V1: + err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); + break; + case FSCRYPT_POLICY_V2: + err = fscrypt_setup_v2_file_key(ci, mk); + break; + default: + WARN_ON(1); + err = -EINVAL; + break; + } + if (err) + goto out_release_key; + + *master_key_ret = key; + return 0; + +out_release_key: + up_read(&mk->mk_secret_sem); + key_put(key); + return err; +} + +static void put_crypt_info(struct fscrypt_info *ci) +{ + struct key *key; + + if (!ci) + return; + + if (ci->ci_direct_key) { + fscrypt_put_direct_key(ci->ci_direct_key); + } else if ((ci->ci_ctfm != NULL || ci->ci_essiv_tfm != NULL) && + !fscrypt_is_direct_key_policy(&ci->ci_policy)) { + crypto_free_skcipher(ci->ci_ctfm); + crypto_free_cipher(ci->ci_essiv_tfm); + } + + key = ci->ci_master_key; + if (key) { + struct fscrypt_master_key *mk = key->payload.data[0]; + + /* + * Remove this inode from the list of inodes that were unlocked + * with the master key. + * + * In addition, if we're removing the last inode from a key that + * already had its secret removed, invalidate the key so that it + * gets removed from ->s_master_keys. + */ + spin_lock(&mk->mk_decrypted_inodes_lock); + list_del(&ci->ci_master_key_link); + spin_unlock(&mk->mk_decrypted_inodes_lock); + if (refcount_dec_and_test(&mk->mk_refcount)) + key_invalidate(key); + key_put(key); + } + kmem_cache_free(fscrypt_info_cachep, ci); +} + +int fscrypt_get_encryption_info(struct inode *inode) +{ + struct fscrypt_info *crypt_info; + union fscrypt_context ctx; + struct fscrypt_mode *mode; + struct key *master_key = NULL; + int res; + + if (fscrypt_has_encryption_key(inode)) + return 0; + + res = fscrypt_initialize(inode->i_sb->s_cop->flags); + if (res) + return res; + + res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + if (res < 0) { + if (!fscrypt_dummy_context_enabled(inode) || + IS_ENCRYPTED(inode)) { + fscrypt_warn(inode, + "Error %d getting encryption context", + res); + return res; + } + /* Fake up a context for an unencrypted directory */ + memset(&ctx, 0, sizeof(ctx)); + ctx.version = FSCRYPT_CONTEXT_V1; + ctx.v1.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; + ctx.v1.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; + memset(ctx.v1.master_key_descriptor, 0x42, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + res = sizeof(ctx.v1); + } + + crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS); + if (!crypt_info) + return -ENOMEM; + + crypt_info->ci_inode = inode; + + res = fscrypt_policy_from_context(&crypt_info->ci_policy, &ctx, res); + if (res) { + fscrypt_warn(inode, + "Unrecognized or corrupt encryption context"); + goto out; + } + + switch (ctx.version) { + case FSCRYPT_CONTEXT_V1: + memcpy(crypt_info->ci_nonce, ctx.v1.nonce, + FS_KEY_DERIVATION_NONCE_SIZE); + break; + case FSCRYPT_CONTEXT_V2: + memcpy(crypt_info->ci_nonce, ctx.v2.nonce, + FS_KEY_DERIVATION_NONCE_SIZE); + break; + default: + WARN_ON(1); + res = -EINVAL; + goto out; + } + + if (!fscrypt_supported_policy(&crypt_info->ci_policy, inode)) { + res = -EINVAL; + goto out; + } + + mode = select_encryption_mode(&crypt_info->ci_policy, inode); + if (IS_ERR(mode)) { + res = PTR_ERR(mode); + goto out; + } + WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE); + crypt_info->ci_mode = mode; + + res = setup_file_encryption_key(crypt_info, &master_key); + if (res) + goto out; + + if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) { + if (master_key) { + struct fscrypt_master_key *mk = + master_key->payload.data[0]; + + refcount_inc(&mk->mk_refcount); + crypt_info->ci_master_key = key_get(master_key); + spin_lock(&mk->mk_decrypted_inodes_lock); + list_add(&crypt_info->ci_master_key_link, + &mk->mk_decrypted_inodes); + spin_unlock(&mk->mk_decrypted_inodes_lock); + } + crypt_info = NULL; + } + res = 0; +out: + if (master_key) { + struct fscrypt_master_key *mk = master_key->payload.data[0]; + + up_read(&mk->mk_secret_sem); + key_put(master_key); + } + if (res == -ENOKEY) + res = 0; + put_crypt_info(crypt_info); + return res; +} +EXPORT_SYMBOL(fscrypt_get_encryption_info); + +/** + * fscrypt_put_encryption_info - free most of an inode's fscrypt data + * + * Free the inode's fscrypt_info. Filesystems must call this when the inode is + * being evicted. An RCU grace period need not have elapsed yet. + */ +void fscrypt_put_encryption_info(struct inode *inode) +{ + put_crypt_info(inode->i_crypt_info); + inode->i_crypt_info = NULL; +} +EXPORT_SYMBOL(fscrypt_put_encryption_info); + +/** + * fscrypt_free_inode - free an inode's fscrypt data requiring RCU delay + * + * Free the inode's cached decrypted symlink target, if any. Filesystems must + * call this after an RCU grace period, just before they free the inode. + */ +void fscrypt_free_inode(struct inode *inode) +{ + if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { + kfree(inode->i_link); + inode->i_link = NULL; + } +} +EXPORT_SYMBOL(fscrypt_free_inode); + +/** + * fscrypt_drop_inode - check whether the inode's master key has been removed + * + * Filesystems supporting fscrypt must call this from their ->drop_inode() + * method so that encrypted inodes are evicted as soon as they're no longer in + * use and their master key has been removed. + * + * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 + */ +int fscrypt_drop_inode(struct inode *inode) +{ + const struct fscrypt_info *ci = READ_ONCE(inode->i_crypt_info); + const struct fscrypt_master_key *mk; + + /* + * If ci is NULL, then the inode doesn't have an encryption key set up + * so it's irrelevant. If ci_master_key is NULL, then the master key + * was provided via the legacy mechanism of the process-subscribed + * keyrings, so we don't know whether it's been removed or not. + */ + if (!ci || !ci->ci_master_key) + return 0; + mk = ci->ci_master_key->payload.data[0]; + + /* + * Note: since we aren't holding ->mk_secret_sem, the result here can + * immediately become outdated. But there's no correctness problem with + * unnecessarily evicting. Nor is there a correctness problem with not + * evicting while iput() is racing with the key being removed, since + * then the thread removing the key will either evict the inode itself + * or will correctly detect that it wasn't evicted due to the race. + */ + return !is_master_key_secret_present(&mk->mk_secret); +} +EXPORT_SYMBOL_GPL(fscrypt_drop_inode); diff --git a/fs/crypto/keysetup_v1.c b/fs/crypto/keysetup_v1.c new file mode 100644 index 000000000000..ad1a36c370c3 --- /dev/null +++ b/fs/crypto/keysetup_v1.c @@ -0,0 +1,340 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Key setup for v1 encryption policies + * + * Copyright 2015, 2019 Google LLC + */ + +/* + * This file implements compatibility functions for the original encryption + * policy version ("v1"), including: + * + * - Deriving per-file keys using the AES-128-ECB based KDF + * (rather than the new method of using HKDF-SHA512) + * + * - Retrieving fscrypt master keys from process-subscribed keyrings + * (rather than the new method of using a filesystem-level keyring) + * + * - Handling policies with the DIRECT_KEY flag set using a master key table + * (rather than the new method of implementing DIRECT_KEY with per-mode keys + * managed alongside the master keys in the filesystem-level keyring) + */ + +#include <crypto/algapi.h> +#include <crypto/skcipher.h> +#include <keys/user-type.h> +#include <linux/hashtable.h> +#include <linux/scatterlist.h> + +#include "fscrypt_private.h" + +/* Table of keys referenced by DIRECT_KEY policies */ +static DEFINE_HASHTABLE(fscrypt_direct_keys, 6); /* 6 bits = 64 buckets */ +static DEFINE_SPINLOCK(fscrypt_direct_keys_lock); + +/* + * v1 key derivation function. This generates the derived key by encrypting the + * master key with AES-128-ECB using the nonce as the AES key. This provides a + * unique derived key with sufficient entropy for each inode. However, it's + * nonstandard, non-extensible, doesn't evenly distribute the entropy from the + * master key, and is trivially reversible: an attacker who compromises a + * derived key can "decrypt" it to get back to the master key, then derive any + * other key. For all new code, use HKDF instead. + * + * The master key must be at least as long as the derived key. If the master + * key is longer, then only the first 'derived_keysize' bytes are used. + */ +static int derive_key_aes(const u8 *master_key, + const u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE], + u8 *derived_key, unsigned int derived_keysize) +{ + int res = 0; + struct skcipher_request *req = NULL; + DECLARE_CRYPTO_WAIT(wait); + struct scatterlist src_sg, dst_sg; + struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0); + + if (IS_ERR(tfm)) { + res = PTR_ERR(tfm); + tfm = NULL; + goto out; + } + crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); + req = skcipher_request_alloc(tfm, GFP_NOFS); + if (!req) { + res = -ENOMEM; + goto out; + } + skcipher_request_set_callback(req, + CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, + crypto_req_done, &wait); + res = crypto_skcipher_setkey(tfm, nonce, FS_KEY_DERIVATION_NONCE_SIZE); + if (res < 0) + goto out; + + sg_init_one(&src_sg, master_key, derived_keysize); + sg_init_one(&dst_sg, derived_key, derived_keysize); + skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize, + NULL); + res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); +out: + skcipher_request_free(req); + crypto_free_skcipher(tfm); + return res; +} + +/* + * Search the current task's subscribed keyrings for a "logon" key with + * description prefix:descriptor, and if found acquire a read lock on it and + * return a pointer to its validated payload in *payload_ret. + */ +static struct key * +find_and_lock_process_key(const char *prefix, + const u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE], + unsigned int min_keysize, + const struct fscrypt_key **payload_ret) +{ + char *description; + struct key *key; + const struct user_key_payload *ukp; + const struct fscrypt_key *payload; + + description = kasprintf(GFP_NOFS, "%s%*phN", prefix, + FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor); + if (!description) + return ERR_PTR(-ENOMEM); + + key = request_key(&key_type_logon, description, NULL); + kfree(description); + if (IS_ERR(key)) + return key; + + down_read(&key->sem); + ukp = user_key_payload_locked(key); + + if (!ukp) /* was the key revoked before we acquired its semaphore? */ + goto invalid; + + payload = (const struct fscrypt_key *)ukp->data; + + if (ukp->datalen != sizeof(struct fscrypt_key) || + payload->size < 1 || payload->size > FSCRYPT_MAX_KEY_SIZE) { + fscrypt_warn(NULL, + "key with description '%s' has invalid payload", + key->description); + goto invalid; + } + + if (payload->size < min_keysize) { + fscrypt_warn(NULL, + "key with description '%s' is too short (got %u bytes, need %u+ bytes)", + key->description, payload->size, min_keysize); + goto invalid; + } + + *payload_ret = payload; + return key; + +invalid: + up_read(&key->sem); + key_put(key); + return ERR_PTR(-ENOKEY); +} + +/* Master key referenced by DIRECT_KEY policy */ +struct fscrypt_direct_key { + struct hlist_node dk_node; + refcount_t dk_refcount; + const struct fscrypt_mode *dk_mode; + struct crypto_skcipher *dk_ctfm; + u8 dk_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE]; + u8 dk_raw[FSCRYPT_MAX_KEY_SIZE]; +}; + +static void free_direct_key(struct fscrypt_direct_key *dk) +{ + if (dk) { + crypto_free_skcipher(dk->dk_ctfm); + kzfree(dk); + } +} + +void fscrypt_put_direct_key(struct fscrypt_direct_key *dk) +{ + if (!refcount_dec_and_lock(&dk->dk_refcount, &fscrypt_direct_keys_lock)) + return; + hash_del(&dk->dk_node); + spin_unlock(&fscrypt_direct_keys_lock); + + free_direct_key(dk); +} + +/* + * Find/insert the given key into the fscrypt_direct_keys table. If found, it + * is returned with elevated refcount, and 'to_insert' is freed if non-NULL. If + * not found, 'to_insert' is inserted and returned if it's non-NULL; otherwise + * NULL is returned. + */ +static struct fscrypt_direct_key * +find_or_insert_direct_key(struct fscrypt_direct_key *to_insert, + const u8 *raw_key, const struct fscrypt_info *ci) +{ + unsigned long hash_key; + struct fscrypt_direct_key *dk; + + /* + * Careful: to avoid potentially leaking secret key bytes via timing + * information, we must key the hash table by descriptor rather than by + * raw key, and use crypto_memneq() when comparing raw keys. + */ + + BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE); + memcpy(&hash_key, ci->ci_policy.v1.master_key_descriptor, + sizeof(hash_key)); + + spin_lock(&fscrypt_direct_keys_lock); + hash_for_each_possible(fscrypt_direct_keys, dk, dk_node, hash_key) { + if (memcmp(ci->ci_policy.v1.master_key_descriptor, + dk->dk_descriptor, FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0) + continue; + if (ci->ci_mode != dk->dk_mode) + continue; + if (crypto_memneq(raw_key, dk->dk_raw, ci->ci_mode->keysize)) + continue; + /* using existing tfm with same (descriptor, mode, raw_key) */ + refcount_inc(&dk->dk_refcount); + spin_unlock(&fscrypt_direct_keys_lock); + free_direct_key(to_insert); + return dk; + } + if (to_insert) + hash_add(fscrypt_direct_keys, &to_insert->dk_node, hash_key); + spin_unlock(&fscrypt_direct_keys_lock); + return to_insert; +} + +/* Prepare to encrypt directly using the master key in the given mode */ +static struct fscrypt_direct_key * +fscrypt_get_direct_key(const struct fscrypt_info *ci, const u8 *raw_key) +{ + struct fscrypt_direct_key *dk; + int err; + + /* Is there already a tfm for this key? */ + dk = find_or_insert_direct_key(NULL, raw_key, ci); + if (dk) + return dk; + + /* Nope, allocate one. */ + dk = kzalloc(sizeof(*dk), GFP_NOFS); + if (!dk) + return ERR_PTR(-ENOMEM); + refcount_set(&dk->dk_refcount, 1); + dk->dk_mode = ci->ci_mode; + dk->dk_ctfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, + ci->ci_inode); + if (IS_ERR(dk->dk_ctfm)) { + err = PTR_ERR(dk->dk_ctfm); + dk->dk_ctfm = NULL; + goto err_free_dk; + } + memcpy(dk->dk_descriptor, ci->ci_policy.v1.master_key_descriptor, + FSCRYPT_KEY_DESCRIPTOR_SIZE); + memcpy(dk->dk_raw, raw_key, ci->ci_mode->keysize); + + return find_or_insert_direct_key(dk, raw_key, ci); + +err_free_dk: + free_direct_key(dk); + return ERR_PTR(err); +} + +/* v1 policy, DIRECT_KEY: use the master key directly */ +static int setup_v1_file_key_direct(struct fscrypt_info *ci, + const u8 *raw_master_key) +{ + const struct fscrypt_mode *mode = ci->ci_mode; + struct fscrypt_direct_key *dk; + + if (!fscrypt_mode_supports_direct_key(mode)) { + fscrypt_warn(ci->ci_inode, + "Direct key mode not allowed with %s", + mode->friendly_name); + return -EINVAL; + } + + if (ci->ci_policy.v1.contents_encryption_mode != + ci->ci_policy.v1.filenames_encryption_mode) { + fscrypt_warn(ci->ci_inode, + "Direct key mode not allowed with different contents and filenames modes"); + return -EINVAL; + } + + /* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */ + if (WARN_ON(mode->needs_essiv)) + return -EINVAL; + + dk = fscrypt_get_direct_key(ci, raw_master_key); + if (IS_ERR(dk)) + return PTR_ERR(dk); + ci->ci_direct_key = dk; + ci->ci_ctfm = dk->dk_ctfm; + return 0; +} + +/* v1 policy, !DIRECT_KEY: derive the file's encryption key */ +static int setup_v1_file_key_derived(struct fscrypt_info *ci, + const u8 *raw_master_key) +{ + u8 *derived_key; + int err; + + /* + * This cannot be a stack buffer because it will be passed to the + * scatterlist crypto API during derive_key_aes(). + */ + derived_key = kmalloc(ci->ci_mode->keysize, GFP_NOFS); + if (!derived_key) + return -ENOMEM; + + err = derive_key_aes(raw_master_key, ci->ci_nonce, + derived_key, ci->ci_mode->keysize); + if (err) + goto out; + + err = fscrypt_set_derived_key(ci, derived_key); +out: + kzfree(derived_key); + return err; +} + +int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, const u8 *raw_master_key) +{ + if (ci->ci_policy.v1.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) + return setup_v1_file_key_direct(ci, raw_master_key); + else + return setup_v1_file_key_derived(ci, raw_master_key); +} + +int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci) +{ + struct key *key; + const struct fscrypt_key *payload; + int err; + + key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX, + ci->ci_policy.v1.master_key_descriptor, + ci->ci_mode->keysize, &payload); + if (key == ERR_PTR(-ENOKEY) && ci->ci_inode->i_sb->s_cop->key_prefix) { + key = find_and_lock_process_key(ci->ci_inode->i_sb->s_cop->key_prefix, + ci->ci_policy.v1.master_key_descriptor, + ci->ci_mode->keysize, &payload); + } + if (IS_ERR(key)) + return PTR_ERR(key); + + err = fscrypt_setup_v1_file_key(ci, payload->raw); + up_read(&key->sem); + key_put(key); + return err; +} diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c index 4941fe8471ce..4072ba644595 100644 --- a/fs/crypto/policy.c +++ b/fs/crypto/policy.c @@ -5,8 +5,9 @@ * Copyright (C) 2015, Google, Inc. * Copyright (C) 2015, Motorola Mobility. * - * Written by Michael Halcrow, 2015. + * Originally written by Michael Halcrow, 2015. * Modified by Jaegeuk Kim, 2015. + * Modified by Eric Biggers, 2019 for v2 policy support. */ #include <linux/random.h> @@ -14,70 +15,303 @@ #include <linux/mount.h> #include "fscrypt_private.h" -/* - * check whether an encryption policy is consistent with an encryption context +/** + * fscrypt_policies_equal - check whether two encryption policies are the same + * + * Return: %true if equal, else %false + */ +bool fscrypt_policies_equal(const union fscrypt_policy *policy1, + const union fscrypt_policy *policy2) +{ + if (policy1->version != policy2->version) + return false; + + return !memcmp(policy1, policy2, fscrypt_policy_size(policy1)); +} + +/** + * fscrypt_supported_policy - check whether an encryption policy is supported + * + * Given an encryption policy, check whether all its encryption modes and other + * settings are supported by this kernel. (But we don't currently don't check + * for crypto API support here, so attempting to use an algorithm not configured + * into the crypto API will still fail later.) + * + * Return: %true if supported, else %false + */ +bool fscrypt_supported_policy(const union fscrypt_policy *policy_u, + const struct inode *inode) +{ + switch (policy_u->version) { + case FSCRYPT_POLICY_V1: { + const struct fscrypt_policy_v1 *policy = &policy_u->v1; + + if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode, + policy->filenames_encryption_mode)) { + fscrypt_warn(inode, + "Unsupported encryption modes (contents %d, filenames %d)", + policy->contents_encryption_mode, + policy->filenames_encryption_mode); + return false; + } + + if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) { + fscrypt_warn(inode, + "Unsupported encryption flags (0x%02x)", + policy->flags); + return false; + } + + return true; + } + case FSCRYPT_POLICY_V2: { + const struct fscrypt_policy_v2 *policy = &policy_u->v2; + + if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode, + policy->filenames_encryption_mode)) { + fscrypt_warn(inode, + "Unsupported encryption modes (contents %d, filenames %d)", + policy->contents_encryption_mode, + policy->filenames_encryption_mode); + return false; + } + + if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) { + fscrypt_warn(inode, + "Unsupported encryption flags (0x%02x)", + policy->flags); + return false; + } + + if (memchr_inv(policy->__reserved, 0, + sizeof(policy->__reserved))) { + fscrypt_warn(inode, + "Reserved bits set in encryption policy"); + return false; + } + + return true; + } + } + return false; +} + +/** + * fscrypt_new_context_from_policy - create a new fscrypt_context from a policy + * + * Create an fscrypt_context for an inode that is being assigned the given + * encryption policy. A new nonce is randomly generated. + * + * Return: the size of the new context in bytes. */ -static bool is_encryption_context_consistent_with_policy( - const struct fscrypt_context *ctx, - const struct fscrypt_policy *policy) +static int fscrypt_new_context_from_policy(union fscrypt_context *ctx_u, + const union fscrypt_policy *policy_u) { - return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE) == 0 && - (ctx->flags == policy->flags) && - (ctx->contents_encryption_mode == - policy->contents_encryption_mode) && - (ctx->filenames_encryption_mode == - policy->filenames_encryption_mode); + memset(ctx_u, 0, sizeof(*ctx_u)); + + switch (policy_u->version) { + case FSCRYPT_POLICY_V1: { + const struct fscrypt_policy_v1 *policy = &policy_u->v1; + struct fscrypt_context_v1 *ctx = &ctx_u->v1; + + ctx->version = FSCRYPT_CONTEXT_V1; + ctx->contents_encryption_mode = + policy->contents_encryption_mode; + ctx->filenames_encryption_mode = + policy->filenames_encryption_mode; + ctx->flags = policy->flags; + memcpy(ctx->master_key_descriptor, + policy->master_key_descriptor, + sizeof(ctx->master_key_descriptor)); + get_random_bytes(ctx->nonce, sizeof(ctx->nonce)); + return sizeof(*ctx); + } + case FSCRYPT_POLICY_V2: { + const struct fscrypt_policy_v2 *policy = &policy_u->v2; + struct fscrypt_context_v2 *ctx = &ctx_u->v2; + + ctx->version = FSCRYPT_CONTEXT_V2; + ctx->contents_encryption_mode = + policy->contents_encryption_mode; + ctx->filenames_encryption_mode = + policy->filenames_encryption_mode; + ctx->flags = policy->flags; + memcpy(ctx->master_key_identifier, + policy->master_key_identifier, + sizeof(ctx->master_key_identifier)); + get_random_bytes(ctx->nonce, sizeof(ctx->nonce)); + return sizeof(*ctx); + } + } + BUG(); } -static int create_encryption_context_from_policy(struct inode *inode, - const struct fscrypt_policy *policy) +/** + * fscrypt_policy_from_context - convert an fscrypt_context to an fscrypt_policy + * + * Given an fscrypt_context, build the corresponding fscrypt_policy. + * + * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized + * version number or size. + * + * This does *not* validate the settings within the policy itself, e.g. the + * modes, flags, and reserved bits. Use fscrypt_supported_policy() for that. + */ +int fscrypt_policy_from_context(union fscrypt_policy *policy_u, + const union fscrypt_context *ctx_u, + int ctx_size) { - struct fscrypt_context ctx; + memset(policy_u, 0, sizeof(*policy_u)); + + if (ctx_size <= 0 || ctx_size != fscrypt_context_size(ctx_u)) + return -EINVAL; + + switch (ctx_u->version) { + case FSCRYPT_CONTEXT_V1: { + const struct fscrypt_context_v1 *ctx = &ctx_u->v1; + struct fscrypt_policy_v1 *policy = &policy_u->v1; + + policy->version = FSCRYPT_POLICY_V1; + policy->contents_encryption_mode = + ctx->contents_encryption_mode; + policy->filenames_encryption_mode = + ctx->filenames_encryption_mode; + policy->flags = ctx->flags; + memcpy(policy->master_key_descriptor, + ctx->master_key_descriptor, + sizeof(policy->master_key_descriptor)); + return 0; + } + case FSCRYPT_CONTEXT_V2: { + const struct fscrypt_context_v2 *ctx = &ctx_u->v2; + struct fscrypt_policy_v2 *policy = &policy_u->v2; + + policy->version = FSCRYPT_POLICY_V2; + policy->contents_encryption_mode = + ctx->contents_encryption_mode; + policy->filenames_encryption_mode = + ctx->filenames_encryption_mode; + policy->flags = ctx->flags; + memcpy(policy->__reserved, ctx->__reserved, + sizeof(policy->__reserved)); + memcpy(policy->master_key_identifier, + ctx->master_key_identifier, + sizeof(policy->master_key_identifier)); + return 0; + } + } + /* unreachable */ + return -EINVAL; +} + +/* Retrieve an inode's encryption policy */ +static int fscrypt_get_policy(struct inode *inode, union fscrypt_policy *policy) +{ + const struct fscrypt_info *ci; + union fscrypt_context ctx; + int ret; + + ci = READ_ONCE(inode->i_crypt_info); + if (ci) { + /* key available, use the cached policy */ + *policy = ci->ci_policy; + return 0; + } + + if (!IS_ENCRYPTED(inode)) + return -ENODATA; - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - memcpy(ctx.master_key_descriptor, policy->master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE); + ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + if (ret < 0) + return (ret == -ERANGE) ? -EINVAL : ret; - if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode, - policy->filenames_encryption_mode)) + return fscrypt_policy_from_context(policy, &ctx, ret); +} + +static int set_encryption_policy(struct inode *inode, + const union fscrypt_policy *policy) +{ + union fscrypt_context ctx; + int ctxsize; + int err; + + if (!fscrypt_supported_policy(policy, inode)) return -EINVAL; - if (policy->flags & ~FS_POLICY_FLAGS_VALID) + switch (policy->version) { + case FSCRYPT_POLICY_V1: + /* + * The original encryption policy version provided no way of + * verifying that the correct master key was supplied, which was + * insecure in scenarios where multiple users have access to the + * same encrypted files (even just read-only access). The new + * encryption policy version fixes this and also implies use of + * an improved key derivation function and allows non-root users + * to securely remove keys. So as long as compatibility with + * old kernels isn't required, it is recommended to use the new + * policy version for all new encrypted directories. + */ + pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n", + current->comm, current->pid); + break; + case FSCRYPT_POLICY_V2: + err = fscrypt_verify_key_added(inode->i_sb, + policy->v2.master_key_identifier); + if (err) + return err; + break; + default: + WARN_ON(1); return -EINVAL; + } - ctx.contents_encryption_mode = policy->contents_encryption_mode; - ctx.filenames_encryption_mode = policy->filenames_encryption_mode; - ctx.flags = policy->flags; - BUILD_BUG_ON(sizeof(ctx.nonce) != FS_KEY_DERIVATION_NONCE_SIZE); - get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + ctxsize = fscrypt_new_context_from_policy(&ctx, policy); - return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL); + return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL); } int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg) { - struct fscrypt_policy policy; + union fscrypt_policy policy; + union fscrypt_policy existing_policy; struct inode *inode = file_inode(filp); + u8 version; + int size; int ret; - struct fscrypt_context ctx; - if (copy_from_user(&policy, arg, sizeof(policy))) + if (get_user(policy.version, (const u8 __user *)arg)) return -EFAULT; + size = fscrypt_policy_size(&policy); + if (size <= 0) + return -EINVAL; + + /* + * We should just copy the remaining 'size - 1' bytes here, but a + * bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to + * think that size can be 0 here (despite the check above!) *and* that + * it's a compile-time constant. Thus it would think copy_from_user() + * is passed compile-time constant ULONG_MAX, causing the compile-time + * buffer overflow check to fail, breaking the build. This only occurred + * when building an i386 kernel with -Os and branch profiling enabled. + * + * Work around it by just copying the first byte again... + */ + version = policy.version; + if (copy_from_user(&policy, arg, size)) + return -EFAULT; + policy.version = version; + if (!inode_owner_or_capable(inode)) return -EACCES; - if (policy.version != 0) - return -EINVAL; - ret = mnt_want_write_file(filp); if (ret) return ret; inode_lock(inode); - ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + ret = fscrypt_get_policy(inode, &existing_policy); if (ret == -ENODATA) { if (!S_ISDIR(inode->i_mode)) ret = -ENOTDIR; @@ -86,14 +320,10 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg) else if (!inode->i_sb->s_cop->empty_dir(inode)) ret = -ENOTEMPTY; else - ret = create_encryption_context_from_policy(inode, - &policy); - } else if (ret == sizeof(ctx) && - is_encryption_context_consistent_with_policy(&ctx, - &policy)) { - /* The file already uses the same encryption policy. */ - ret = 0; - } else if (ret >= 0 || ret == -ERANGE) { + ret = set_encryption_policy(inode, &policy); + } else if (ret == -EINVAL || + (ret == 0 && !fscrypt_policies_equal(&policy, + &existing_policy))) { /* The file already uses a different encryption policy. */ ret = -EEXIST; } @@ -105,37 +335,57 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg) } EXPORT_SYMBOL(fscrypt_ioctl_set_policy); +/* Original ioctl version; can only get the original policy version */ int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg) { - struct inode *inode = file_inode(filp); - struct fscrypt_context ctx; - struct fscrypt_policy policy; - int res; + union fscrypt_policy policy; + int err; - if (!IS_ENCRYPTED(inode)) - return -ENODATA; + err = fscrypt_get_policy(file_inode(filp), &policy); + if (err) + return err; - res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); - if (res < 0 && res != -ERANGE) - return res; - if (res != sizeof(ctx)) - return -EINVAL; - if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1) + if (policy.version != FSCRYPT_POLICY_V1) return -EINVAL; - policy.version = 0; - policy.contents_encryption_mode = ctx.contents_encryption_mode; - policy.filenames_encryption_mode = ctx.filenames_encryption_mode; - policy.flags = ctx.flags; - memcpy(policy.master_key_descriptor, ctx.master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE); - - if (copy_to_user(arg, &policy, sizeof(policy))) + if (copy_to_user(arg, &policy, sizeof(policy.v1))) return -EFAULT; return 0; } EXPORT_SYMBOL(fscrypt_ioctl_get_policy); +/* Extended ioctl version; can get policies of any version */ +int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg) +{ + struct fscrypt_get_policy_ex_arg arg; + union fscrypt_policy *policy = (union fscrypt_policy *)&arg.policy; + size_t policy_size; + int err; + + /* arg is policy_size, then policy */ + BUILD_BUG_ON(offsetof(typeof(arg), policy_size) != 0); + BUILD_BUG_ON(offsetofend(typeof(arg), policy_size) != + offsetof(typeof(arg), policy)); + BUILD_BUG_ON(sizeof(arg.policy) != sizeof(*policy)); + + err = fscrypt_get_policy(file_inode(filp), policy); + if (err) + return err; + policy_size = fscrypt_policy_size(policy); + + if (copy_from_user(&arg, uarg, sizeof(arg.policy_size))) + return -EFAULT; + + if (policy_size > arg.policy_size) + return -EOVERFLOW; + arg.policy_size = policy_size; + + if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + policy_size)) + return -EFAULT; + return 0; +} +EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex); + /** * fscrypt_has_permitted_context() - is a file's encryption policy permitted * within its directory? @@ -157,10 +407,8 @@ EXPORT_SYMBOL(fscrypt_ioctl_get_policy); */ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) { - const struct fscrypt_operations *cops = parent->i_sb->s_cop; - const struct fscrypt_info *parent_ci, *child_ci; - struct fscrypt_context parent_ctx, child_ctx; - int res; + union fscrypt_policy parent_policy, child_policy; + int err; /* No restrictions on file types which are never encrypted */ if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) && @@ -190,41 +438,22 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) * In any case, if an unexpected error occurs, fall back to "forbidden". */ - res = fscrypt_get_encryption_info(parent); - if (res) + err = fscrypt_get_encryption_info(parent); + if (err) return 0; - res = fscrypt_get_encryption_info(child); - if (res) + err = fscrypt_get_encryption_info(child); + if (err) return 0; - parent_ci = READ_ONCE(parent->i_crypt_info); - child_ci = READ_ONCE(child->i_crypt_info); - - if (parent_ci && child_ci) { - return memcmp(parent_ci->ci_master_key_descriptor, - child_ci->ci_master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE) == 0 && - (parent_ci->ci_data_mode == child_ci->ci_data_mode) && - (parent_ci->ci_filename_mode == - child_ci->ci_filename_mode) && - (parent_ci->ci_flags == child_ci->ci_flags); - } - res = cops->get_context(parent, &parent_ctx, sizeof(parent_ctx)); - if (res != sizeof(parent_ctx)) + err = fscrypt_get_policy(parent, &parent_policy); + if (err) return 0; - res = cops->get_context(child, &child_ctx, sizeof(child_ctx)); - if (res != sizeof(child_ctx)) + err = fscrypt_get_policy(child, &child_policy); + if (err) return 0; - return memcmp(parent_ctx.master_key_descriptor, - child_ctx.master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE) == 0 && - (parent_ctx.contents_encryption_mode == - child_ctx.contents_encryption_mode) && - (parent_ctx.filenames_encryption_mode == - child_ctx.filenames_encryption_mode) && - (parent_ctx.flags == child_ctx.flags); + return fscrypt_policies_equal(&parent_policy, &child_policy); } EXPORT_SYMBOL(fscrypt_has_permitted_context); @@ -240,7 +469,8 @@ EXPORT_SYMBOL(fscrypt_has_permitted_context); int fscrypt_inherit_context(struct inode *parent, struct inode *child, void *fs_data, bool preload) { - struct fscrypt_context ctx; + union fscrypt_context ctx; + int ctxsize; struct fscrypt_info *ci; int res; @@ -252,16 +482,10 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child, if (ci == NULL) return -ENOKEY; - ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1; - ctx.contents_encryption_mode = ci->ci_data_mode; - ctx.filenames_encryption_mode = ci->ci_filename_mode; - ctx.flags = ci->ci_flags; - memcpy(ctx.master_key_descriptor, ci->ci_master_key_descriptor, - FS_KEY_DESCRIPTOR_SIZE); - get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE); + ctxsize = fscrypt_new_context_from_policy(&ctx, &ci->ci_policy); + BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE); - res = parent->i_sb->s_cop->set_context(child, &ctx, - sizeof(ctx), fs_data); + res = parent->i_sb->s_cop->set_context(child, &ctx, ctxsize, fs_data); if (res) return res; return preload ? fscrypt_get_encryption_info(child): 0; |