path: root/crypto
diff options
authorEric Biggers <>2018-12-16 23:23:22 -0800
committerHerbert Xu <>2019-01-10 21:37:31 +0800
commit8f9c469348487844328e162db57112f7d347c49f (patch)
tree661adb4ed0b78db712241e5b5f22b46a6c2a33b4 /crypto
parentbfeffd155283772bbe78c6a05dec7c0128ee500c (diff)
crypto: authenc - fix parsing key with misaligned rta_len
Keys for "authenc" AEADs are formatted as an rtattr containing a 4-byte 'enckeylen', followed by an authentication key and an encryption key. crypto_authenc_extractkeys() parses the key to find the inner keys. However, it fails to consider the case where the rtattr's payload is longer than 4 bytes but not 4-byte aligned, and where the key ends before the next 4-byte aligned boundary. In this case, 'keylen -= RTA_ALIGN(rta->rta_len);' underflows to a value near UINT_MAX. This causes a buffer overread and crash during crypto_ahash_setkey(). Fix it by restricting the rtattr payload to the expected size. Reproducer using AF_ALG: #include <linux/if_alg.h> #include <linux/rtnetlink.h> #include <sys/socket.h> int main() { int fd; struct sockaddr_alg addr = { .salg_type = "aead", .salg_name = "authenc(hmac(sha256),cbc(aes))", }; struct { struct rtattr attr; __be32 enckeylen; char keys[1]; } __attribute__((packed)) key = { .attr.rta_len = sizeof(key), .attr.rta_type = 1 /* CRYPTO_AUTHENC_KEYA_PARAM */, }; fd = socket(AF_ALG, SOCK_SEQPACKET, 0); bind(fd, (void *)&addr, sizeof(addr)); setsockopt(fd, SOL_ALG, ALG_SET_KEY, &key, sizeof(key)); } It caused: BUG: unable to handle kernel paging request at ffff88007ffdc000 PGD 2e01067 P4D 2e01067 PUD 2e04067 PMD 2e05067 PTE 0 Oops: 0000 [#1] SMP CPU: 0 PID: 883 Comm: authenc Not tainted 4.20.0-rc1-00108-g00c9fe37a7f27 #13 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014 RIP: 0010:sha256_ni_transform+0xb3/0x330 arch/x86/crypto/sha256_ni_asm.S:155 [...] Call Trace: sha256_ni_finup+0x10/0x20 arch/x86/crypto/sha256_ssse3_glue.c:321 crypto_shash_finup+0x1a/0x30 crypto/shash.c:178 shash_digest_unaligned+0x45/0x60 crypto/shash.c:186 crypto_shash_digest+0x24/0x40 crypto/shash.c:202 hmac_setkey+0x135/0x1e0 crypto/hmac.c:66 crypto_shash_setkey+0x2b/0xb0 crypto/shash.c:66 shash_async_setkey+0x10/0x20 crypto/shash.c:223 crypto_ahash_setkey+0x2d/0xa0 crypto/ahash.c:202 crypto_authenc_setkey+0x68/0x100 crypto/authenc.c:96 crypto_aead_setkey+0x2a/0xc0 crypto/aead.c:62 aead_setkey+0xc/0x10 crypto/algif_aead.c:526 alg_setkey crypto/af_alg.c:223 [inline] alg_setsockopt+0xfe/0x130 crypto/af_alg.c:256 __sys_setsockopt+0x6d/0xd0 net/socket.c:1902 __do_sys_setsockopt net/socket.c:1913 [inline] __se_sys_setsockopt net/socket.c:1910 [inline] __x64_sys_setsockopt+0x1f/0x30 net/socket.c:1910 do_syscall_64+0x4a/0x180 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Fixes: e236d4a89a2f ("[CRYPTO] authenc: Move enckeylen into key itself") Cc: <> # v2.6.25+ Signed-off-by: Eric Biggers <> Signed-off-by: Herbert Xu <>
Diffstat (limited to 'crypto')
1 files changed, 11 insertions, 3 deletions
diff --git a/crypto/authenc.c b/crypto/authenc.c
index 37f54d1b2f66..4be293a4b5f0 100644
--- a/crypto/authenc.c
+++ b/crypto/authenc.c
@@ -58,14 +58,22 @@ int crypto_authenc_extractkeys(struct crypto_authenc_keys *keys, const u8 *key,
return -EINVAL;
if (rta->rta_type != CRYPTO_AUTHENC_KEYA_PARAM)
return -EINVAL;
- if (RTA_PAYLOAD(rta) < sizeof(*param))
+ /*
+ * RTA_OK() didn't align the rtattr's payload when validating that it
+ * fits in the buffer. Yet, the keys should start on the next 4-byte
+ * aligned boundary. To avoid confusion, require that the rtattr
+ * payload be exactly the param struct, which has a 4-byte aligned size.
+ */
+ if (RTA_PAYLOAD(rta) != sizeof(*param))
return -EINVAL;
+ BUILD_BUG_ON(sizeof(*param) % RTA_ALIGNTO);
param = RTA_DATA(rta);
keys->enckeylen = be32_to_cpu(param->enckeylen);
- key += RTA_ALIGN(rta->rta_len);
- keylen -= RTA_ALIGN(rta->rta_len);
+ key += rta->rta_len;
+ keylen -= rta->rta_len;
if (keylen < keys->enckeylen)
return -EINVAL;