diff options
Diffstat (limited to 'src/crypto/modes/cbc.c')
| -rw-r--r-- | src/crypto/modes/cbc.c | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/src/crypto/modes/cbc.c b/src/crypto/modes/cbc.c index ba4805b..931b718 100644 --- a/src/crypto/modes/cbc.c +++ b/src/crypto/modes/cbc.c @@ -63,7 +63,8 @@ void CRYPTO_cbc128_encrypt(const uint8_t *in, uint8_t *out, size_t len, size_t n; const uint8_t *iv = ivec; - assert(in && out && key && ivec); + assert(key != NULL && ivec != NULL); + assert(len == 0 || (in != NULL && out != NULL)); if (STRICT_ALIGNMENT && ((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) { @@ -119,9 +120,17 @@ void CRYPTO_cbc128_decrypt(const uint8_t *in, uint8_t *out, size_t len, uint8_t c[16]; } tmp; - assert(in && out && key && ivec); + assert(key != NULL && ivec != NULL); + assert(len == 0 || (in != NULL && out != NULL)); - if (in != out) { + const uintptr_t inptr = (uintptr_t) in; + const uintptr_t outptr = (uintptr_t) out; + /* If |in| and |out| alias, |in| must be ahead. */ + assert(inptr >= outptr || inptr + len <= outptr); + + if ((inptr >= 32 && outptr <= inptr - 32) || inptr < outptr) { + /* If |out| is at least two blocks behind |in| or completely disjoint, there + * is no need to decrypt to a temporary block. */ const uint8_t *iv = ivec; if (STRICT_ALIGNMENT && @@ -152,6 +161,9 @@ void CRYPTO_cbc128_decrypt(const uint8_t *in, uint8_t *out, size_t len, } memcpy(ivec, iv, 16); } else { + /* |out| is less than two blocks behind |in|. Decrypting an input block + * directly to |out| would overwrite a ciphertext block before it is used as + * the next block's IV. Decrypt to a temporary block instead. */ if (STRICT_ALIGNMENT && ((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) { uint8_t c; |