diff options
| author | David Benjamin <davidben@chromium.org> | 2015-03-19 03:11:13 +0300 |
|---|---|---|
| committer | Adam Langley <agl@google.com> | 2015-03-19 14:33:46 +0300 |
| commit | ced555394f527876910c4299059ab71226f8cc4d (patch) | |
| tree | ea9be36d72e6f777507a1aa71b593b91bf341159 /crypto/aes | |
| parent | 34860739dea8bd7e55ae196ae481b52b49607418 (diff) | |
Fix undefined behavior in shifts.
Td4 is an array of u8. A u8 << int promotes the u8 to an int first then shifts.
If the mathematical result of a shift (as modelled by lhs * 2^{rhs}) is not
representable in an integer, behaviour is undefined. In other words, you can't
shift into the sign bit of a signed integer. Fix this by casting to u32
whenever we're shifting left by 24.
(For consistency, cast other shifts, too.)
Caught by -fsanitize=shift
Submitted by Nick Lewycky (Google)
(Imported from upstream's 8b37e5c14f0eddb10c7f91ef91004622d90ef361.)
Change-Id: Id0f98d1d65738533c6ddcc3c21bc38b569d74793
Reviewed-on: https://boringssl-review.googlesource.com/4040
Reviewed-by: Adam Langley <agl@google.com>
Diffstat (limited to 'crypto/aes')
| -rw-r--r-- | crypto/aes/aes.c | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/crypto/aes/aes.c b/crypto/aes/aes.c index 97b4fbdf..933aa073 100644 --- a/crypto/aes/aes.c +++ b/crypto/aes/aes.c @@ -1033,17 +1033,25 @@ void AES_decrypt(const uint8_t *in, uint8_t *out, const AES_KEY *key) { #endif /* ?FULL_UNROLL */ /* apply last round and * map cipher state to byte array block: */ - s0 = (Td4[(t0 >> 24)] << 24) ^ (Td4[(t3 >> 16) & 0xff] << 16) ^ - (Td4[(t2 >> 8) & 0xff] << 8) ^ (Td4[(t1) & 0xff]) ^ rk[0]; + s0 = ((uint32_t)Td4[(t0 >> 24)] << 24) ^ + ((uint32_t)Td4[(t3 >> 16) & 0xff] << 16) ^ + ((uint32_t)Td4[(t2 >> 8) & 0xff] << 8) ^ + ((uint32_t)Td4[(t1) & 0xff]) ^ rk[0]; PUTU32(out, s0); - s1 = (Td4[(t1 >> 24)] << 24) ^ (Td4[(t0 >> 16) & 0xff] << 16) ^ - (Td4[(t3 >> 8) & 0xff] << 8) ^ (Td4[(t2) & 0xff]) ^ rk[1]; + s1 = ((uint32_t)Td4[(t1 >> 24)] << 24) ^ + ((uint32_t)Td4[(t0 >> 16) & 0xff] << 16) ^ + ((uint32_t)Td4[(t3 >> 8) & 0xff] << 8) ^ + ((uint32_t)Td4[(t2) & 0xff]) ^ rk[1]; PUTU32(out + 4, s1); - s2 = (Td4[(t2 >> 24)] << 24) ^ (Td4[(t1 >> 16) & 0xff] << 16) ^ - (Td4[(t0 >> 8) & 0xff] << 8) ^ (Td4[(t3) & 0xff]) ^ rk[2]; + s2 = ((uint32_t)Td4[(t2 >> 24)] << 24) ^ + ((uint32_t)Td4[(t1 >> 16) & 0xff] << 16) ^ + ((uint32_t)Td4[(t0 >> 8) & 0xff] << 8) ^ + ((uint32_t)Td4[(t3) & 0xff]) ^ rk[2]; PUTU32(out + 8, s2); - s3 = (Td4[(t3 >> 24)] << 24) ^ (Td4[(t2 >> 16) & 0xff] << 16) ^ - (Td4[(t1 >> 8) & 0xff] << 8) ^ (Td4[(t0) & 0xff]) ^ rk[3]; + s3 = ((uint32_t)Td4[(t3 >> 24)] << 24) ^ + ((uint32_t)Td4[(t2 >> 16) & 0xff] << 16) ^ + ((uint32_t)Td4[(t1 >> 8) & 0xff] << 8) ^ + ((uint32_t)Td4[(t0) & 0xff]) ^ rk[3]; PUTU32(out + 12, s3); } |