From: Eric Biggers ebiggers@google.com
commit e1354400b25da645c4764ed6844d12f1582c3b66 upstream.
The "hmac(sha3-224-generic)" algorithm has a descsize of 368 bytes, which is greater than HASH_MAX_DESCSIZE (360) which is only enough for sha3-224-generic. The check in shash_prepare_alg() doesn't catch this because the HMAC template doesn't set descsize on the algorithms, but rather sets it on each individual HMAC transform.
This causes a stack buffer overflow when SHASH_DESC_ON_STACK() is used with hmac(sha3-224-generic).
Fix it by increasing HASH_MAX_DESCSIZE to the real maximum. Also add a sanity check to hmac_init().
This was detected by the improved crypto self-tests in v5.2, by loading the tcrypt module with CONFIG_CRYPTO_MANAGER_EXTRA_TESTS=y enabled. I didn't notice this bug when I ran the self-tests by requesting the algorithms via AF_ALG (i.e., not using tcrypt), probably because the stack layout differs in the two cases and that made a difference here.
KASAN report:
BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:359 [inline] BUG: KASAN: stack-out-of-bounds in shash_default_import+0x52/0x80 crypto/shash.c:223 Write of size 360 at addr ffff8880651defc8 by task insmod/3689
CPU: 2 PID: 3689 Comm: insmod Tainted: G E 5.1.0-10741-g35c99ffa20edd #11 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x86/0xc5 lib/dump_stack.c:113 print_address_description+0x7f/0x260 mm/kasan/report.c:188 __kasan_report+0x144/0x187 mm/kasan/report.c:317 kasan_report+0x12/0x20 mm/kasan/common.c:614 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x137/0x190 mm/kasan/generic.c:191 memcpy+0x37/0x50 mm/kasan/common.c:125 memcpy include/linux/string.h:359 [inline] shash_default_import+0x52/0x80 crypto/shash.c:223 crypto_shash_import include/crypto/hash.h:880 [inline] hmac_import+0x184/0x240 crypto/hmac.c:102 hmac_init+0x96/0xc0 crypto/hmac.c:107 crypto_shash_init include/crypto/hash.h:902 [inline] shash_digest_unaligned+0x9f/0xf0 crypto/shash.c:194 crypto_shash_digest+0xe9/0x1b0 crypto/shash.c:211 generate_random_hash_testvec.constprop.11+0x1ec/0x5b0 crypto/testmgr.c:1331 test_hash_vs_generic_impl+0x3f7/0x5c0 crypto/testmgr.c:1420 __alg_test_hash+0x26d/0x340 crypto/testmgr.c:1502 alg_test_hash+0x22e/0x330 crypto/testmgr.c:1552 alg_test.part.7+0x132/0x610 crypto/testmgr.c:4931 alg_test+0x1f/0x40 crypto/testmgr.c:4952
Fixes: b68a7ec1e9a3 ("crypto: hash - Remove VLA usage") Reported-by: Corentin Labbe clabbe.montjoie@gmail.com Cc: stable@vger.kernel.org # v4.20+ Cc: Kees Cook keescook@chromium.org Signed-off-by: Eric Biggers ebiggers@google.com Reviewed-by: Kees Cook keescook@chromium.org Tested-by: Corentin Labbe clabbe.montjoie@gmail.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- crypto/hmac.c | 2 ++ include/crypto/hash.h | 8 +++++++- 2 files changed, 9 insertions(+), 1 deletion(-)
--- a/crypto/hmac.c +++ b/crypto/hmac.c @@ -168,6 +168,8 @@ static int hmac_init_tfm(struct crypto_t
parent->descsize = sizeof(struct shash_desc) + crypto_shash_descsize(hash); + if (WARN_ON(parent->descsize > HASH_MAX_DESCSIZE)) + return -EINVAL;
ctx->hash = hash; return 0; --- a/include/crypto/hash.h +++ b/include/crypto/hash.h @@ -152,7 +152,13 @@ struct shash_desc { };
#define HASH_MAX_DIGESTSIZE 64 -#define HASH_MAX_DESCSIZE 360 + +/* + * Worst case is hmac(sha3-224-generic). Its context is a nested 'shash_desc' + * containing a 'struct sha3_state'. + */ +#define HASH_MAX_DESCSIZE (sizeof(struct shash_desc) + 360) + #define HASH_MAX_STATESIZE 512
#define SHASH_DESC_ON_STACK(shash, ctx) \