crypto/evp: harden AEAD ciphers.
authorAndy Polyakov <appro@openssl.org>
Wed, 18 Jan 2017 23:20:49 +0000 (00:20 +0100)
committerMatt Caswell <matt@openssl.org>
Thu, 26 Jan 2017 10:54:01 +0000 (10:54 +0000)
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>
crypto/evp/e_aes.c
crypto/evp/e_chacha20_poly1305.c

index c0b0a1e..2e5e4ed 100644 (file)
@@ -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;
         }
index befd805..46bc2cb 100644 (file)
@@ -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);