kernel/crypto/shash.c, branch linux-5.1.y

crypto: shash - remove pointless checks of shash_alg::{export,import}

2019-01-18T10:40:24Z

crypto_init_shash_ops_async() only gives the ahash tfm non-NULL ->export() and ->import() if the underlying shash alg has these non-NULL. This doesn't make sense because when an shash algorithm is registered, shash_prepare_alg() sets a default ->export() and ->import() if the implementor didn't provide them. And elsewhere it's assumed that all shash algs and ahash tfms have non-NULL ->export() and ->import(). Therefore, remove these unnecessary, always-true conditions. Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu

crypto: shash - require neither or both ->export() and ->import()

2019-01-18T10:40:24Z

Prevent registering shash algorithms that implement ->export() but not ->import(), or ->import() but not ->export(). Such cases don't make sense and could confuse the check that shash_prepare_alg() does for just ->export(). I don't believe this affects any existing algorithms; this is just preventing future mistakes. Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu

crypto: hash - set CRYPTO_TFM_NEED_KEY if ->setkey() fails

2019-01-18T10:40:24Z

Some algorithms have a ->setkey() method that is not atomic, in the sense that setting a key can fail after changes were already made to the tfm context. In this case, if a key was already set the tfm can end up in a state that corresponds to neither the old key nor the new key. It's not feasible to make all ->setkey() methods atomic, especially ones that have to key multiple sub-tfms. Therefore, make the crypto API set CRYPTO_TFM_NEED_KEY if ->setkey() fails and the algorithm requires a key, to prevent the tfm from being used until a new key is set. Note: we can't set CRYPTO_TFM_NEED_KEY for OPTIONAL_KEY algorithms, so ->setkey() for those must nevertheless be atomic. That's fine for now since only the crc32 and crc32c algorithms set OPTIONAL_KEY, and it's not intended that OPTIONAL_KEY be used much. [Cc stable mainly because when introducing the NEED_KEY flag I changed AF_ALG to rely on it; and unlike in-kernel crypto API users, AF_ALG previously didn't have this problem. So these "incompletely keyed" states became theoretically accessible via AF_ALG -- though, the opportunities for causing real mischief seem pretty limited.] Fixes: 9fa68f620041 ("crypto: hash - prevent using keyed hashes without setting key") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu

crypto: user - clean up report structure copying

2018-11-09T09:41:39Z

There have been a pretty ridiculous number of issues with initializing the report structures that are copied to userspace by NETLINK_CRYPTO. Commit 4473710df1f8 ("crypto: user - Prepare for CRYPTO_MAX_ALG_NAME expansion") replaced some strncpy()s with strlcpy()s, thereby introducing information leaks. Later two other people tried to replace other strncpy()s with strlcpy() too, which would have introduced even more information leaks: - https://lore.kernel.org/patchwork/patch/954991/ - https://patchwork.kernel.org/patch/10434351/ Commit cac5818c25d0 ("crypto: user - Implement a generic crypto statistics") also uses the buggy strlcpy() approach and therefore leaks uninitialized memory to userspace. A fix was proposed, but it was originally incomplete. Seeing as how apparently no one can get this right with the current approach, change all the reporting functions to: - Start by memsetting the report structure to 0. This guarantees it's always initialized, regardless of what happens later. - Initialize all strings using strscpy(). This is safe after the memset, ensures null termination of long strings, avoids unnecessary work, and avoids the -Wstringop-truncation warnings from gcc. - Use sizeof(var) instead of sizeof(type). This is more robust against copy+paste errors. For simplicity, also reuse the -EMSGSIZE return value from nla_put(). Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu

crypto: shash - Remove VLA usage in unaligned hashing

2018-09-04T03:37:03Z

In the quest to remove all stack VLA usage from the kernel[1], this uses the newly defined max alignment to perform unaligned hashing to avoid VLAs, and drops the helper function while adding sanity checks on the resulting buffer sizes. Additionally, the __aligned_largest macro is removed since this helper was the only user. [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook Signed-off-by: Herbert Xu

crypto: hash - Remove VLA usage

2018-09-04T03:35:03Z

In the quest to remove all stack VLA usage from the kernel[1], this removes the VLAs in SHASH_DESC_ON_STACK (via crypto_shash_descsize()) by using the maximum allowable size (which is now more clearly captured in a macro), along with a few other cases. Similar limits are turned into macros as well. A review of existing sizes shows that SHA512_DIGEST_SIZE (64) is the largest digest size and that sizeof(struct sha3_state) (360) is the largest descriptor size. The corresponding maximums are reduced. [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook Signed-off-by: Herbert Xu

crypto: hash - prevent using keyed hashes without setting key

2018-01-12T12:03:37Z

Currently, almost none of the keyed hash algorithms check whether a key has been set before proceeding. Some algorithms are okay with this and will effectively just use a key of all 0's or some other bogus default. However, others will severely break, as demonstrated using "hmac(sha3-512-generic)", the unkeyed use of which causes a kernel crash via a (potentially exploitable) stack buffer overflow. A while ago, this problem was solved for AF_ALG by pairing each hash transform with a 'has_key' bool. However, there are still other places in the kernel where userspace can specify an arbitrary hash algorithm by name, and the kernel uses it as unkeyed hash without checking whether it is really unkeyed. Examples of this include: - KEYCTL_DH_COMPUTE, via the KDF extension - dm-verity - dm-crypt, via the ESSIV support - dm-integrity, via the "internal hash" mode with no key given - drbd (Distributed Replicated Block Device) This bug is especially bad for KEYCTL_DH_COMPUTE as that requires no privileges to call. Fix the bug for all users by adding a flag CRYPTO_TFM_NEED_KEY to the ->crt_flags of each hash transform that indicates whether the transform still needs to be keyed or not. Then, make the hash init, import, and digest functions return -ENOKEY if the key is still needed. The new flag also replaces the 'has_key' bool which algif_hash was previously using, thereby simplifying the algif_hash implementation. Reported-by: syzbot Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu

crypto: hmac - require that the underlying hash algorithm is unkeyed

2017-11-29T02:39:15Z

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 #include 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 Cc: Signed-off-by: Eric Biggers Signed-off-by: Herbert Xu

crypto: shash - Fix zero-length shash ahash digest crash

2017-10-10T16:34:07Z

The shash ahash digest adaptor function may crash if given a zero-length input together with a null SG list. This is because it tries to read the SG list before looking at the length. This patch fixes it by checking the length first. Cc: Reported-by: Stephan Müller Signed-off-by: Herbert Xu Tested-by: Stephan Müller

crypto: shash - Fix a sleep-in-atomic bug in shash_setkey_unaligned

2017-10-07T04:04:32Z

The SCTP program may sleep under a spinlock, and the function call path is: sctp_generate_t3_rtx_event (acquire the spinlock) sctp_do_sm sctp_side_effects sctp_cmd_interpreter sctp_make_init_ack sctp_pack_cookie crypto_shash_setkey shash_setkey_unaligned kmalloc(GFP_KERNEL) For the same reason, the orinoco driver may sleep in interrupt handler, and the function call path is: orinoco_rx_isr_tasklet orinoco_rx orinoco_mic crypto_shash_setkey shash_setkey_unaligned kmalloc(GFP_KERNEL) To fix it, GFP_KERNEL is replaced with GFP_ATOMIC. This bug is found by my static analysis tool and my code review. Signed-off-by: Jia-Ju Bai Signed-off-by: Herbert Xu