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crypto/evp: harden AEAD ciphers.

Originally a crash in 32-bit build was reported CHACHA20-POLY1305
cipher. The crash is triggered by truncated packet and is result
of excessive hashing to the edge of accessible memory. Since hash
operation is read-only it is not considered to be exploitable
beyond a DoS condition. Other ciphers were hardened.

Thanks to Robert Święcki for report.

CVE-2017-3731

Reviewed-by: Rich Salz <rsalz@openssl.org>
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dot-asm authored and mattcaswell committed Jan 18, 2017
1 parent f3a7e57 commit 00d965474b22b54e4275232bc71ee0c699c5cd21
Showing with 15 additions and 4 deletions.
  1. +12 −2 crypto/evp/e_aes.c
  2. +3 −2 crypto/evp/e_chacha20_poly1305.c
@@ -1388,10 +1388,15 @@ static int aes_gcm_ctrl(EVP_CIPHER_CTX *c, int type, int arg, void *ptr)
EVP_CIPHER_CTX_buf_noconst(c)[arg - 2] << 8
| EVP_CIPHER_CTX_buf_noconst(c)[arg - 1];
/* Correct length for explicit IV */
if (len < EVP_GCM_TLS_EXPLICIT_IV_LEN)
return 0;
len -= EVP_GCM_TLS_EXPLICIT_IV_LEN;
/* If decrypting correct for tag too */
if (!EVP_CIPHER_CTX_encrypting(c))
if (!EVP_CIPHER_CTX_encrypting(c)) {
if (len < EVP_GCM_TLS_TAG_LEN)
return 0;
len -= EVP_GCM_TLS_TAG_LEN;
}
EVP_CIPHER_CTX_buf_noconst(c)[arg - 2] = len >> 8;
EVP_CIPHER_CTX_buf_noconst(c)[arg - 1] = len & 0xff;
}
@@ -1946,10 +1951,15 @@ static int aes_ccm_ctrl(EVP_CIPHER_CTX *c, int type, int arg, void *ptr)
EVP_CIPHER_CTX_buf_noconst(c)[arg - 2] << 8
| EVP_CIPHER_CTX_buf_noconst(c)[arg - 1];
/* Correct length for explicit IV */
if (len < EVP_CCM_TLS_EXPLICIT_IV_LEN)
return 0;
len -= EVP_CCM_TLS_EXPLICIT_IV_LEN;
/* If decrypting correct for tag too */
if (!EVP_CIPHER_CTX_encrypting(c))
if (!EVP_CIPHER_CTX_encrypting(c)) {
if (len < cctx->M)
return 0;
len -= cctx->M;
}
EVP_CIPHER_CTX_buf_noconst(c)[arg - 2] = len >> 8;
EVP_CIPHER_CTX_buf_noconst(c)[arg - 1] = len & 0xff;
}
@@ -398,6 +398,8 @@ static int chacha20_poly1305_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg,
len = aad[EVP_AEAD_TLS1_AAD_LEN - 2] << 8 |
aad[EVP_AEAD_TLS1_AAD_LEN - 1];
if (!ctx->encrypt) {
if (len < POLY1305_BLOCK_SIZE)
return 0;
len -= POLY1305_BLOCK_SIZE; /* discount attached tag */
memcpy(temp, aad, EVP_AEAD_TLS1_AAD_LEN - 2);
aad = temp;
@@ -407,8 +409,7 @@ static int chacha20_poly1305_ctrl(EVP_CIPHER_CTX *ctx, int type, int arg,
actx->tls_payload_length = len;
/*
* merge record sequence number as per
* draft-ietf-tls-chacha20-poly1305-03
* merge record sequence number as per RFC7905
*/
actx->key.counter[1] = actx->nonce[0];
actx->key.counter[2] = actx->nonce[1] ^ CHACHA_U8TOU32(aad);

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