1 files changed, 80 insertions, 43 deletions

diff --git a/ssl/s3_enc.c b/ssl/s3_enc.c
index c5df2cb90ae1..e3cd4f062c5a 100644
--- a/ssl/s3_enc.c
+++ b/ssl/s3_enc.c
@@ -466,12 +466,21 @@ void ssl3_cleanup_key_block(SSL *s)
 	s->s3->tmp.key_block_length=0;
 	}
 
+/* ssl3_enc encrypts/decrypts the record in |s->wrec| / |s->rrec|, respectively.
+ *
+ * Returns:
+ *   0: (in non-constant time) if the record is publically invalid (i.e. too
+ *       short etc).
+ *   1: if the record's padding is valid / the encryption was successful.
+ *   -1: if the record's padding is invalid or, if sending, an internal error
+ *       occured.
+ */
 int ssl3_enc(SSL *s, int send)
 	{
 	SSL3_RECORD *rec;
 	EVP_CIPHER_CTX *ds;
 	unsigned long l;
-	int bs,i;
+	int bs,i,mac_size=0;
 	const EVP_CIPHER *enc;
 
 	if (send)
@@ -522,32 +531,16 @@ int ssl3_enc(SSL *s, int send)
 		if (!send)
 			{
 			if (l == 0 || l%bs != 0)
-				{
-				SSLerr(SSL_F_SSL3_ENC,SSL_R_BLOCK_CIPHER_PAD_IS_WRONG);
-				ssl3_send_alert(s,SSL3_AL_FATAL,SSL_AD_DECRYPTION_FAILED);
 				return 0;
-				}
 			/* otherwise, rec->length >= bs */
 			}
 		
 		EVP_Cipher(ds,rec->data,rec->input,l);
 
+		if (EVP_MD_CTX_md(s->read_hash) != NULL)
+			mac_size = EVP_MD_CTX_size(s->read_hash);
 		if ((bs != 1) && !send)
-			{
-			i=rec->data[l-1]+1;
-			/* SSL 3.0 bounds the number of padding bytes by the block size;
-			 * padding bytes (except the last one) are arbitrary */
-			if (i > bs)
-				{
-				/* Incorrect padding. SSLerr() and ssl3_alert are done
-				 * by caller: we don't want to reveal whether this is
-				 * a decryption error or a MAC verification failure
-				 * (see http://www.openssl.org/~bodo/tls-cbc.txt) */
-				return -1;
-				}
-			/* now i <= bs <= rec->length */
-			rec->length-=i;
-			}
+			return ssl3_cbc_remove_padding(s, rec, bs, mac_size);
 		}
 	return(1);
 	}
@@ -716,7 +709,7 @@ int n_ssl3_mac(SSL *ssl, unsigned char *md, int send)
 	EVP_MD_CTX md_ctx;
 	const EVP_MD_CTX *hash;
 	unsigned char *p,rec_char;
-	unsigned int md_size;
+	size_t md_size, orig_len;
 	int npad;
 	int t;
 
@@ -741,28 +734,72 @@ int n_ssl3_mac(SSL *ssl, unsigned char *md, int send)
 	md_size=t;
 	npad=(48/md_size)*md_size;
 
-	/* Chop the digest off the end :-) */
-	EVP_MD_CTX_init(&md_ctx);
-
-	EVP_MD_CTX_copy_ex( &md_ctx,hash);
-	EVP_DigestUpdate(&md_ctx,mac_sec,md_size);
-	EVP_DigestUpdate(&md_ctx,ssl3_pad_1,npad);
-	EVP_DigestUpdate(&md_ctx,seq,8);
-	rec_char=rec->type;
-	EVP_DigestUpdate(&md_ctx,&rec_char,1);
-	p=md;
-	s2n(rec->length,p);
-	EVP_DigestUpdate(&md_ctx,md,2);
-	EVP_DigestUpdate(&md_ctx,rec->input,rec->length);
-	EVP_DigestFinal_ex( &md_ctx,md,NULL);
-
-	EVP_MD_CTX_copy_ex( &md_ctx,hash);
-	EVP_DigestUpdate(&md_ctx,mac_sec,md_size);
-	EVP_DigestUpdate(&md_ctx,ssl3_pad_2,npad);
-	EVP_DigestUpdate(&md_ctx,md,md_size);
-	EVP_DigestFinal_ex( &md_ctx,md,&md_size);
-
-	EVP_MD_CTX_cleanup(&md_ctx);
+	/* kludge: ssl3_cbc_remove_padding passes padding length in rec->type */
+	orig_len = rec->length+md_size+((unsigned int)rec->type>>8);
+	rec->type &= 0xff;
+
+	if (!send &&
+	    EVP_CIPHER_CTX_mode(ssl->enc_read_ctx) == EVP_CIPH_CBC_MODE &&
+	    ssl3_cbc_record_digest_supported(hash))
+		{
+		/* This is a CBC-encrypted record. We must avoid leaking any
+		 * timing-side channel information about how many blocks of
+		 * data we are hashing because that gives an attacker a
+		 * timing-oracle. */
+
+		/* npad is, at most, 48 bytes and that's with MD5:
+		 *   16 + 48 + 8 (sequence bytes) + 1 + 2 = 75.
+		 *
+		 * With SHA-1 (the largest hash speced for SSLv3) the hash size
+		 * goes up 4, but npad goes down by 8, resulting in a smaller
+		 * total size. */
+		unsigned char header[75];
+		unsigned j = 0;
+		memcpy(header+j, mac_sec, md_size);
+		j += md_size;
+		memcpy(header+j, ssl3_pad_1, npad);
+		j += npad;
+		memcpy(header+j, seq, 8);
+		j += 8;
+		header[j++] = rec->type;
+		header[j++] = rec->length >> 8;
+		header[j++] = rec->length & 0xff;
+
+		ssl3_cbc_digest_record(
+			hash,
+			md, &md_size,
+			header, rec->input,
+			rec->length + md_size, orig_len,
+			mac_sec, md_size,
+			1 /* is SSLv3 */);
+		}
+	else
+		{
+		unsigned int md_size_u;
+		/* Chop the digest off the end :-) */
+		EVP_MD_CTX_init(&md_ctx);
+
+		EVP_MD_CTX_copy_ex( &md_ctx,hash);
+		EVP_DigestUpdate(&md_ctx,mac_sec,md_size);
+		EVP_DigestUpdate(&md_ctx,ssl3_pad_1,npad);
+		EVP_DigestUpdate(&md_ctx,seq,8);
+		rec_char=rec->type;
+		EVP_DigestUpdate(&md_ctx,&rec_char,1);
+		p=md;
+		s2n(rec->length,p);
+		EVP_DigestUpdate(&md_ctx,md,2);
+		EVP_DigestUpdate(&md_ctx,rec->input,rec->length);
+		EVP_DigestFinal_ex( &md_ctx,md,NULL);
+
+		EVP_MD_CTX_copy_ex( &md_ctx,hash);
+		EVP_DigestUpdate(&md_ctx,mac_sec,md_size);
+		EVP_DigestUpdate(&md_ctx,ssl3_pad_2,npad);
+		EVP_DigestUpdate(&md_ctx,md,md_size);
+		EVP_DigestFinal_ex( &md_ctx,md,&md_size_u);
+		md_size = md_size_u;
+
+		EVP_MD_CTX_cleanup(&md_ctx);
+	}
 
 	ssl3_record_sequence_update(seq);
 	return(md_size);