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authorEric Biggers <ebiggers@google.com>2017-11-28 18:01:38 -0800
committerHerbert Xu <herbert@gondor.apana.org.au>2017-11-29 13:39:15 +1100
commitaf3ff8045bbf3e32f1a448542e73abb4c8ceb6f1 (patch)
treec6201b05bafc29103a179e0f2d14c82d23866818 /include/crypto/internal
parent887207ed9e5812ed9239b6d07185a2d35dda91db (diff)
downloadlinux-stericsson-af3ff8045bbf3e32f1a448542e73abb4c8ceb6f1.tar.gz
crypto: hmac - require that the underlying hash algorithm is unkeyed
Because the HMAC template didn't check that its underlying hash algorithm is unkeyed, trying to use "hmac(hmac(sha3-512-generic))" through AF_ALG or through KEYCTL_DH_COMPUTE resulted in the inner HMAC being used without having been keyed, resulting in sha3_update() being called without sha3_init(), causing a stack buffer overflow. This is a very old bug, but it seems to have only started causing real problems when SHA-3 support was added (requires CONFIG_CRYPTO_SHA3) because the innermost hash's state is ->import()ed from a zeroed buffer, and it just so happens that other hash algorithms are fine with that, but SHA-3 is not. However, there could be arch or hardware-dependent hash algorithms also affected; I couldn't test everything. Fix the bug by introducing a function crypto_shash_alg_has_setkey() which tests whether a shash algorithm is keyed. Then update the HMAC template to require that its underlying hash algorithm is unkeyed. Here is a reproducer: #include <linux/if_alg.h> #include <sys/socket.h> int main() { int algfd; struct sockaddr_alg addr = { .salg_type = "hash", .salg_name = "hmac(hmac(sha3-512-generic))", }; char key[4096] = { 0 }; algfd = socket(AF_ALG, SOCK_SEQPACKET, 0); bind(algfd, (const struct sockaddr *)&addr, sizeof(addr)); setsockopt(algfd, SOL_ALG, ALG_SET_KEY, key, sizeof(key)); } Here was the KASAN report from syzbot: BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:341 [inline] BUG: KASAN: stack-out-of-bounds in sha3_update+0xdf/0x2e0 crypto/sha3_generic.c:161 Write of size 4096 at addr ffff8801cca07c40 by task syzkaller076574/3044 CPU: 1 PID: 3044 Comm: syzkaller076574 Not tainted 4.14.0-mm1+ #25 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 print_address_description+0x73/0x250 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report+0x25b/0x340 mm/kasan/report.c:409 check_memory_region_inline mm/kasan/kasan.c:260 [inline] check_memory_region+0x137/0x190 mm/kasan/kasan.c:267 memcpy+0x37/0x50 mm/kasan/kasan.c:303 memcpy include/linux/string.h:341 [inline] sha3_update+0xdf/0x2e0 crypto/sha3_generic.c:161 crypto_shash_update+0xcb/0x220 crypto/shash.c:109 shash_finup_unaligned+0x2a/0x60 crypto/shash.c:151 crypto_shash_finup+0xc4/0x120 crypto/shash.c:165 hmac_finup+0x182/0x330 crypto/hmac.c:152 crypto_shash_finup+0xc4/0x120 crypto/shash.c:165 shash_digest_unaligned+0x9e/0xd0 crypto/shash.c:172 crypto_shash_digest+0xc4/0x120 crypto/shash.c:186 hmac_setkey+0x36a/0x690 crypto/hmac.c:66 crypto_shash_setkey+0xad/0x190 crypto/shash.c:64 shash_async_setkey+0x47/0x60 crypto/shash.c:207 crypto_ahash_setkey+0xaf/0x180 crypto/ahash.c:200 hash_setkey+0x40/0x90 crypto/algif_hash.c:446 alg_setkey crypto/af_alg.c:221 [inline] alg_setsockopt+0x2a1/0x350 crypto/af_alg.c:254 SYSC_setsockopt net/socket.c:1851 [inline] SyS_setsockopt+0x189/0x360 net/socket.c:1830 entry_SYSCALL_64_fastpath+0x1f/0x96 Reported-by: syzbot <syzkaller@googlegroups.com> Cc: <stable@vger.kernel.org> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'include/crypto/internal')
-rw-r--r--include/crypto/internal/hash.h8
1 files changed, 8 insertions, 0 deletions
diff --git a/include/crypto/internal/hash.h b/include/crypto/internal/hash.h
index f0b44c16e88f..c2bae8da642c 100644
--- a/include/crypto/internal/hash.h
+++ b/include/crypto/internal/hash.h
@@ -82,6 +82,14 @@ int ahash_register_instance(struct crypto_template *tmpl,
struct ahash_instance *inst);
void ahash_free_instance(struct crypto_instance *inst);
+int shash_no_setkey(struct crypto_shash *tfm, const u8 *key,
+ unsigned int keylen);
+
+static inline bool crypto_shash_alg_has_setkey(struct shash_alg *alg)
+{
+ return alg->setkey != shash_no_setkey;
+}
+
int crypto_init_ahash_spawn(struct crypto_ahash_spawn *spawn,
struct hash_alg_common *alg,
struct crypto_instance *inst);