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authorDavid Howells <dhowells@redhat.com>2019-06-26 21:02:32 +0100
committerDavid Howells <dhowells@redhat.com>2019-06-26 21:02:32 +0100
commitb206f281d0ee14969878469816a69db22d5838e8 (patch)
tree56828bdaec25c05d6b4126196276bf969d056929 /security
parentdcf49dbc8077e278ddd1bc7298abc781496e8a08 (diff)
keys: Namespace keyring names
Keyring names are held in a single global list that any process can pick from by means of keyctl_join_session_keyring (provided the keyring grants Search permission). This isn't very container friendly, however. Make the following changes: (1) Make default session, process and thread keyring names begin with a '.' instead of '_'. (2) Keyrings whose names begin with a '.' aren't added to the list. Such keyrings are system specials. (3) Replace the global list with per-user_namespace lists. A keyring adds its name to the list for the user_namespace that it is currently in. (4) When a user_namespace is deleted, it just removes itself from the keyring name list. The global keyring_name_lock is retained for accessing the name lists. This allows (4) to work. This can be tested by: # keyctl newring foo @s 995906392 # unshare -U $ keyctl show ... 995906392 --alswrv 65534 65534 \_ keyring: foo ... $ keyctl session foo Joined session keyring: 935622349 As can be seen, a new session keyring was created. The capability bit KEYCTL_CAPS1_NS_KEYRING_NAME is set if the kernel is employing this feature. Signed-off-by: David Howells <dhowells@redhat.com> cc: Eric W. Biederman <ebiederm@xmission.com>
Diffstat (limited to 'security')
-rw-r--r--security/keys/keyctl.c3
-rw-r--r--security/keys/keyring.c99
2 files changed, 45 insertions, 57 deletions
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 169409b611b0..8a813220f269 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -30,7 +30,7 @@
#define KEY_MAX_DESC_SIZE 4096
-static const unsigned char keyrings_capabilities[1] = {
+static const unsigned char keyrings_capabilities[2] = {
[0] = (KEYCTL_CAPS0_CAPABILITIES |
(IS_ENABLED(CONFIG_PERSISTENT_KEYRINGS) ? KEYCTL_CAPS0_PERSISTENT_KEYRINGS : 0) |
(IS_ENABLED(CONFIG_KEY_DH_OPERATIONS) ? KEYCTL_CAPS0_DIFFIE_HELLMAN : 0) |
@@ -40,6 +40,7 @@ static const unsigned char keyrings_capabilities[1] = {
KEYCTL_CAPS0_RESTRICT_KEYRING |
KEYCTL_CAPS0_MOVE
),
+ [1] = (KEYCTL_CAPS1_NS_KEYRING_NAME),
};
static int key_get_type_from_user(char *type,
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 20891cd198f0..fe851292509e 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -16,6 +16,7 @@
#include <linux/security.h>
#include <linux/seq_file.h>
#include <linux/err.h>
+#include <linux/user_namespace.h>
#include <keys/keyring-type.h>
#include <keys/user-type.h>
#include <linux/assoc_array_priv.h>
@@ -29,11 +30,6 @@
#define KEYRING_SEARCH_MAX_DEPTH 6
/*
- * We keep all named keyrings in a hash to speed looking them up.
- */
-#define KEYRING_NAME_HASH_SIZE (1 << 5)
-
-/*
* We mark pointers we pass to the associative array with bit 1 set if
* they're keyrings and clear otherwise.
*/
@@ -55,17 +51,20 @@ static inline void *keyring_key_to_ptr(struct key *key)
return key;
}
-static struct list_head keyring_name_hash[KEYRING_NAME_HASH_SIZE];
static DEFINE_RWLOCK(keyring_name_lock);
-static inline unsigned keyring_hash(const char *desc)
+/*
+ * Clean up the bits of user_namespace that belong to us.
+ */
+void key_free_user_ns(struct user_namespace *ns)
{
- unsigned bucket = 0;
-
- for (; *desc; desc++)
- bucket += (unsigned char)*desc;
+ write_lock(&keyring_name_lock);
+ list_del_init(&ns->keyring_name_list);
+ write_unlock(&keyring_name_lock);
- return bucket & (KEYRING_NAME_HASH_SIZE - 1);
+#ifdef CONFIG_PERSISTENT_KEYRINGS
+ key_put(ns->persistent_keyring_register);
+#endif
}
/*
@@ -104,23 +103,17 @@ static DEFINE_MUTEX(keyring_serialise_link_lock);
/*
* Publish the name of a keyring so that it can be found by name (if it has
- * one).
+ * one and it doesn't begin with a dot).
*/
static void keyring_publish_name(struct key *keyring)
{
- int bucket;
-
- if (keyring->description) {
- bucket = keyring_hash(keyring->description);
+ struct user_namespace *ns = current_user_ns();
+ if (keyring->description &&
+ keyring->description[0] &&
+ keyring->description[0] != '.') {
write_lock(&keyring_name_lock);
-
- if (!keyring_name_hash[bucket].next)
- INIT_LIST_HEAD(&keyring_name_hash[bucket]);
-
- list_add_tail(&keyring->name_link,
- &keyring_name_hash[bucket]);
-
+ list_add_tail(&keyring->name_link, &ns->keyring_name_list);
write_unlock(&keyring_name_lock);
}
}
@@ -1097,50 +1090,44 @@ found:
*/
struct key *find_keyring_by_name(const char *name, bool uid_keyring)
{
+ struct user_namespace *ns = current_user_ns();
struct key *keyring;
- int bucket;
if (!name)
return ERR_PTR(-EINVAL);
- bucket = keyring_hash(name);
-
read_lock(&keyring_name_lock);
- if (keyring_name_hash[bucket].next) {
- /* search this hash bucket for a keyring with a matching name
- * that's readable and that hasn't been revoked */
- list_for_each_entry(keyring,
- &keyring_name_hash[bucket],
- name_link
- ) {
- if (!kuid_has_mapping(current_user_ns(), keyring->user->uid))
- continue;
-
- if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
- continue;
+ /* Search this hash bucket for a keyring with a matching name that
+ * grants Search permission and that hasn't been revoked
+ */
+ list_for_each_entry(keyring, &ns->keyring_name_list, name_link) {
+ if (!kuid_has_mapping(ns, keyring->user->uid))
+ continue;
- if (strcmp(keyring->description, name) != 0)
- continue;
+ if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
+ continue;
- if (uid_keyring) {
- if (!test_bit(KEY_FLAG_UID_KEYRING,
- &keyring->flags))
- continue;
- } else {
- if (key_permission(make_key_ref(keyring, 0),
- KEY_NEED_SEARCH) < 0)
- continue;
- }
+ if (strcmp(keyring->description, name) != 0)
+ continue;
- /* we've got a match but we might end up racing with
- * key_cleanup() if the keyring is currently 'dead'
- * (ie. it has a zero usage count) */
- if (!refcount_inc_not_zero(&keyring->usage))
+ if (uid_keyring) {
+ if (!test_bit(KEY_FLAG_UID_KEYRING,
+ &keyring->flags))
+ continue;
+ } else {
+ if (key_permission(make_key_ref(keyring, 0),
+ KEY_NEED_SEARCH) < 0)
continue;
- keyring->last_used_at = ktime_get_real_seconds();
- goto out;
}
+
+ /* we've got a match but we might end up racing with
+ * key_cleanup() if the keyring is currently 'dead'
+ * (ie. it has a zero usage count) */
+ if (!refcount_inc_not_zero(&keyring->usage))
+ continue;
+ keyring->last_used_at = ktime_get_real_seconds();
+ goto out;
}
keyring = ERR_PTR(-ENOKEY);