Fixed out-of-bounds read errors in ssl3_get_key_exchange.

PR#3450
Reviewed-by: NEmilia Käsper <emilia@openssl.org>

ssl/s3_clnt.c

@@ -1378,8 +1378,8 @@ int ssl3_get_key_exchange(SSL *s)
 #endif
 	EVP_MD_CTX md_ctx;
 	unsigned char *param,*p;
-	int al,i,j,param_len,ok;
-	long n,alg_k,alg_a;
+	int al,j,ok;
+	long i,param_len,n,alg_k,alg_a;
 	EVP_PKEY *pkey=NULL;
 	const EVP_MD *md = NULL;
 #ifndef OPENSSL_NO_RSA
@@ -1455,36 +1455,48 @@ int ssl3_get_key_exchange(SSL *s)
 		s->session->sess_cert=ssl_sess_cert_new();
 		}
 
+	/* Total length of the parameters including the length prefix */
 	param_len=0;
+
 	alg_k=s->s3->tmp.new_cipher->algorithm_mkey;
 	alg_a=s->s3->tmp.new_cipher->algorithm_auth;
 	EVP_MD_CTX_init(&md_ctx);
 
+	al=SSL_AD_DECODE_ERROR;
+
 #ifndef OPENSSL_NO_PSK
 	if (alg_k & SSL_kPSK)
 		{
 		char tmp_id_hint[PSK_MAX_IDENTITY_LEN+1];
 
-		al=SSL_AD_HANDSHAKE_FAILURE;
+		param_len = 2;
+		if (param_len > n)
+			{
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
 		n2s(p,i);
-		param_len=i+2;
+
 		/* Store PSK identity hint for later use, hint is used
 		 * in ssl3_send_client_key_exchange.  Assume that the
 		 * maximum length of a PSK identity hint can be as
 		 * long as the maximum length of a PSK identity. */
 		if (i > PSK_MAX_IDENTITY_LEN)
 			{
+			al=SSL_AD_HANDSHAKE_FAILURE;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
 				SSL_R_DATA_LENGTH_TOO_LONG);
 			goto f_err;
 			}
-		if (param_len > n)
+		if (i > n - param_len)
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
 				SSL_R_BAD_PSK_IDENTITY_HINT_LENGTH);
 			goto f_err;
 			}
+		param_len += i;
+
 		/* If received PSK identity hint contains NULL
 		 * characters, the hint is truncated from the first
 		 * NULL. p may not be ending with NULL, so create a
@@ -1496,6 +1508,7 @@ int ssl3_get_key_exchange(SSL *s)
 		s->ctx->psk_identity_hint = BUF_strdup(tmp_id_hint);
 		if (s->ctx->psk_identity_hint == NULL)
 			{
+			al=SSL_AD_HANDSHAKE_FAILURE;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, ERR_R_MALLOC_FAILURE);
 			goto f_err;
 			}	   
@@ -1508,14 +1521,22 @@ int ssl3_get_key_exchange(SSL *s)
 #ifndef OPENSSL_NO_SRP
 	if (alg_k & SSL_kSRP)
 		{
-		n2s(p,i);
-		param_len=i+2;
+		param_len = 2;
 		if (param_len > n)
 			{
-			al=SSL_AD_DECODE_ERROR;
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
+		n2s(p,i);
+
+		if (i > n - param_len)
+			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_BAD_SRP_N_LENGTH);
 			goto f_err;
 			}
+		param_len += i;
+
 		if (!(s->srp_ctx.N=BN_bin2bn(p,i,NULL)))
 			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_BN_LIB);
@@ -1523,14 +1544,24 @@ int ssl3_get_key_exchange(SSL *s)
 			}
 		p+=i;
 
+
+		if (2 > n - param_len)
+			{
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
+		param_len += 2;
+
 		n2s(p,i);
-		param_len+=i+2;
-		if (param_len > n)
+
+		if (i > n - param_len)
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_BAD_SRP_G_LENGTH);
 			goto f_err;
 			}
+		param_len += i;
+
 		if (!(s->srp_ctx.g=BN_bin2bn(p,i,NULL)))
 			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_BN_LIB);
@@ -1538,15 +1569,25 @@ int ssl3_get_key_exchange(SSL *s)
 			}
 		p+=i;
 
+
+		if (1 > n - param_len)
+			{
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
+		param_len += 1;
+
 		i = (unsigned int)(p[0]);
 		p++;
-		param_len+=i+1;
-		if (param_len > n)
+
+		if (i > n - param_len)
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_BAD_SRP_S_LENGTH);
 			goto f_err;
 			}
+		param_len += i;
+
 		if (!(s->srp_ctx.s=BN_bin2bn(p,i,NULL)))
 			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_BN_LIB);
@@ -1554,14 +1595,23 @@ int ssl3_get_key_exchange(SSL *s)
 			}
 		p+=i;
 
+		if (2 > n - param_len)
+			{
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
+		param_len += 2;
+
 		n2s(p,i);
-		param_len+=i+2;
-		if (param_len > n)
+
+		if (i > n - param_len)
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_BAD_SRP_B_LENGTH);
 			goto f_err;
 			}
+		param_len += i;
+
 		if (!(s->srp_ctx.B=BN_bin2bn(p,i,NULL)))
 			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_BN_LIB);
@@ -1599,14 +1649,23 @@ int ssl3_get_key_exchange(SSL *s)
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_MALLOC_FAILURE);
 			goto err;
 			}
-		n2s(p,i);
-		param_len=i+2;
+
+		param_len = 2;
 		if (param_len > n)
 			{
-			al=SSL_AD_DECODE_ERROR;
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
+		n2s(p,i);
+
+		if (i > n - param_len)
+			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_BAD_RSA_MODULUS_LENGTH);
 			goto f_err;
 			}
+		param_len += i;
+
 		if (!(rsa->n=BN_bin2bn(p,i,rsa->n)))
 			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_BN_LIB);
@@ -1614,14 +1673,23 @@ int ssl3_get_key_exchange(SSL *s)
 			}
 		p+=i;
 
+		if (2 > n - param_len)
+			{
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
+		param_len += 2;
+
 		n2s(p,i);
-		param_len+=i+2;
-		if (param_len > n)
+
+		if (i > n - param_len)
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_BAD_RSA_E_LENGTH);
 			goto f_err;
 			}
+		param_len += i;
+
 		if (!(rsa->e=BN_bin2bn(p,i,rsa->e)))
 			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_BN_LIB);
@@ -1653,14 +1721,23 @@ int ssl3_get_key_exchange(SSL *s)
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_DH_LIB);
 			goto err;
 			}
-		n2s(p,i);
-		param_len=i+2;
+
+		param_len = 2;
 		if (param_len > n)
 			{
-			al=SSL_AD_DECODE_ERROR;
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
+		n2s(p,i);
+
+		if (i > n - param_len)
+			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_BAD_DH_P_LENGTH);
 			goto f_err;
 			}
+		param_len += i;
+
 		if (!(dh->p=BN_bin2bn(p,i,NULL)))
 			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_BN_LIB);
@@ -1668,14 +1745,23 @@ int ssl3_get_key_exchange(SSL *s)
 			}
 		p+=i;
 
+		if (2 > n - param_len)
+			{
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
+		param_len += 2;
+
 		n2s(p,i);
-		param_len+=i+2;
-		if (param_len > n)
+
+		if (i > n - param_len)
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_BAD_DH_G_LENGTH);
 			goto f_err;
 			}
+		param_len += i;
+
 		if (!(dh->g=BN_bin2bn(p,i,NULL)))
 			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_BN_LIB);
@@ -1683,14 +1769,23 @@ int ssl3_get_key_exchange(SSL *s)
 			}
 		p+=i;
 
+		if (2 > n - param_len)
+			{
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
+		param_len += 2;
+
 		n2s(p,i);
-		param_len+=i+2;
-		if (param_len > n)
+
+		if (i > n - param_len)
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_BAD_DH_PUB_KEY_LENGTH);
 			goto f_err;
 			}
+		param_len += i;
+
 		if (!(dh->pub_key=BN_bin2bn(p,i,NULL)))
 			{
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,ERR_R_BN_LIB);
@@ -1750,15 +1845,21 @@ int ssl3_get_key_exchange(SSL *s)
 		 */
 
 		/* XXX: For now we only support named (not generic) curves
-		 * and the ECParameters in this case is just three bytes.
+		 * and the ECParameters in this case is just three bytes. We
+		 * also need one byte for the length of the encoded point
 		 */
-		param_len=3;
+		param_len=4;
+		if (param_len > n)
+			{
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
 		/* Check curve is one of our preferences, if not server has
-		 * sent an invalid curve.
+		 * sent an invalid curve. ECParameters is 3 bytes.
 		 */
-		if (!tls1_check_curve(s, p, param_len))
+		if (!tls1_check_curve(s, p, 3))
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_WRONG_CURVE);
 			goto f_err;
 			}
@@ -1805,15 +1906,15 @@ int ssl3_get_key_exchange(SSL *s)
 
 		encoded_pt_len = *p;  /* length of encoded point */
 		p+=1;
-		param_len += (1 + encoded_pt_len);
-		if ((param_len > n) ||
+
+		if ((encoded_pt_len > n - param_len) ||
 		    (EC_POINT_oct2point(group, srvr_ecpoint, 
 			p, encoded_pt_len, bn_ctx) == 0))
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_BAD_ECPOINT);
 			goto f_err;
 			}
+		param_len += encoded_pt_len;
 
 		n-=param_len;
 		p+=encoded_pt_len;
@@ -1856,12 +1957,18 @@ int ssl3_get_key_exchange(SSL *s)
 		{
 		if (SSL_USE_SIGALGS(s))
 			{
-			int rv = tls12_check_peer_sigalg(&md, s, p, pkey);
+			int rv;
+			if (2 > n)
+				{
+				SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+					SSL_R_LENGTH_TOO_SHORT);
+				goto f_err;
+				}
+			rv = tls12_check_peer_sigalg(&md, s, p, pkey);
 			if (rv == -1)
 				goto err;
 			else if (rv == 0)
 				{
-				al = SSL_AD_DECODE_ERROR;
 				goto f_err;
 				}
 #ifdef SSL_DEBUG
@@ -1872,15 +1979,21 @@ fprintf(stderr, "USING TLSv1.2 HASH %s\n", EVP_MD_name(md));
 			}
 		else
 			md = EVP_sha1();
-			
+
+		if (2 > n)
+			{
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
 		n2s(p,i);
 		n-=2;
 		j=EVP_PKEY_size(pkey);
 
+		/* Check signature length. If n is 0 then signature is empty */
 		if ((i != n) || (n > j) || (n <= 0))
 			{
 			/* wrong packet length */
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_WRONG_SIGNATURE_LENGTH);
 			goto f_err;
 			}
@@ -1951,7 +2064,6 @@ fprintf(stderr, "USING TLSv1.2 HASH %s\n", EVP_MD_name(md));
 		/* still data left over */
 		if (n != 0)
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_EXTRA_DATA_IN_MESSAGE);
 			goto f_err;
 			}