Fixed out-of-bounds read errors in ssl3_get_key_exchange.

PR#3450

Conflicts:
	ssl/s3_clnt.c

Reviewed-by: Emilia Käsper <emilia@openssl.org>

1 files changed, 80 insertions, 27 deletions

diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index c11048edaa..99de1bf608 100644
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -1095,8 +1095,8 @@ 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;
+	int al,j,ok;
+	long i,param_len,n,alg;
 	EVP_PKEY *pkey=NULL;
 #ifndef OPENSSL_NO_RSA
 	RSA *rsa=NULL;
@@ -1160,10 +1160,12 @@ 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=s->s3->tmp.new_cipher->algorithms;
 	EVP_MD_CTX_init(&md_ctx);
 
+	al=SSL_AD_DECODE_ERROR;
 #ifndef OPENSSL_NO_RSA
 	if (alg & SSL_kRSA)
 		{
@@ -1172,14 +1174,23 @@ 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);
@@ -1187,14 +1198,23 @@ 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);
@@ -1226,14 +1246,23 @@ 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);
@@ -1241,14 +1270,23 @@ 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);
@@ -1256,14 +1294,23 @@ 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);
@@ -1315,12 +1362,19 @@ 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;
-		if ((param_len > n) ||
-		    (*p != NAMED_CURVE_TYPE) || 
-		    ((curve_nid = curve_id2nid(*(p + 2))) == 0)) 
+		param_len=4;
+		if (param_len > n)
+			{
+			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,
+				SSL_R_LENGTH_TOO_SHORT);
+			goto f_err;
+			}
+
+		if ((*p != NAMED_CURVE_TYPE) || 
+		    ((curve_nid = curve_id2nid(*(p + 2))) == 0))
 			{
 			al=SSL_AD_INTERNAL_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_UNABLE_TO_FIND_ECDH_PARAMETERS);
@@ -1362,15 +1416,15 @@ 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;
@@ -1421,10 +1475,10 @@ int ssl3_get_key_exchange(SSL *s)
 		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;
 			}
@@ -1518,7 +1572,6 @@ int ssl3_get_key_exchange(SSL *s)
 			}
 		if (n != 0)
 			{
-			al=SSL_AD_DECODE_ERROR;
 			SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE,SSL_R_EXTRA_DATA_IN_MESSAGE);
 			goto f_err;
 			}