Fix seg fault with 0 p val in SKE

If a client receives a ServerKeyExchange for an anon DH ciphersuite with the
value of p set to 0 then a seg fault can occur. This commits adds a test to
reject p, g and pub key parameters that have a 0 value (in accordance with
RFC 5246)

The security vulnerability only affects master and 1.0.2, but the fix is
additionally applied to 1.0.1 for additional confidence.

CVE-2015-1794

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>

diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index 6af145a8b744daaa60c292d39a38da185477ccc2..2059151a46b7c37bd74d79a5f40d8e0f246e9688 100644 (file)
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -1699,6 +1699,12 @@ int ssl3_get_key_exchange(SSL *s)
         }
         p += i;
 
+        if (BN_is_zero(dh->p)) {
+            SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_BAD_DH_P_VALUE);
+            goto f_err;
+        }
+
+
         if (2 > n - param_len) {
             SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_LENGTH_TOO_SHORT);
             goto f_err;
@@ -1719,6 +1725,11 @@ int ssl3_get_key_exchange(SSL *s)
         }
         p += i;
 
+        if (BN_is_zero(dh->g)) {
+            SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_BAD_DH_G_VALUE);
+            goto f_err;
+        }
+
         if (2 > n - param_len) {
             SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_LENGTH_TOO_SHORT);
             goto f_err;
@@ -1740,6 +1751,11 @@ int ssl3_get_key_exchange(SSL *s)
         p += i;
         n -= param_len;
 
+        if (BN_is_zero(dh->pub_key)) {
+            SSLerr(SSL_F_SSL3_GET_KEY_EXCHANGE, SSL_R_BAD_DH_PUB_KEY_VALUE);
+            goto f_err;
+        }
+
 # ifndef OPENSSL_NO_RSA
         if (alg_a & SSL_aRSA)
             pkey =

diff --git a/ssl/ssl.h b/ssl/ssl.h
index 6fe1a2474d43a8c8b937bfe71eba75fb4e446610..c6c5bce4af625a6b5197ca1f4f117f28bc0fbbf7 100644 (file)
--- a/ssl/ssl.h
+++ b/ssl/ssl.h
@@ -2846,8 +2846,11 @@ void ERR_load_SSL_strings(void);
 # define SSL_R_BAD_DATA_RETURNED_BY_CALLBACK              106
 # define SSL_R_BAD_DECOMPRESSION                          107
 # define SSL_R_BAD_DH_G_LENGTH                            108
+# define SSL_R_BAD_DH_G_VALUE                             375
 # define SSL_R_BAD_DH_PUB_KEY_LENGTH                      109
+# define SSL_R_BAD_DH_PUB_KEY_VALUE                       393
 # define SSL_R_BAD_DH_P_LENGTH                            110
+# define SSL_R_BAD_DH_P_VALUE                             395
 # define SSL_R_BAD_DIGEST_LENGTH                          111
 # define SSL_R_BAD_DSA_SIGNATURE                          112
 # define SSL_R_BAD_ECC_CERT                               304

diff --git a/ssl/ssl_err.c b/ssl/ssl_err.c
index 1a6030e6238dee099d36c60beedf6461fc9bbf14..202228b48ddb512d1358db44a0851c5b675b99f9 100644 (file)
--- a/ssl/ssl_err.c
+++ b/ssl/ssl_err.c
@@ -386,8 +386,11 @@ static ERR_STRING_DATA SSL_str_reasons[] = {
      "bad data returned by callback"},
     {ERR_REASON(SSL_R_BAD_DECOMPRESSION), "bad decompression"},
     {ERR_REASON(SSL_R_BAD_DH_G_LENGTH), "bad dh g length"},
+    {ERR_REASON(SSL_R_BAD_DH_G_VALUE), "bad dh g value"},
     {ERR_REASON(SSL_R_BAD_DH_PUB_KEY_LENGTH), "bad dh pub key length"},
+    {ERR_REASON(SSL_R_BAD_DH_PUB_KEY_VALUE), "bad dh pub key value"},
     {ERR_REASON(SSL_R_BAD_DH_P_LENGTH), "bad dh p length"},
+    {ERR_REASON(SSL_R_BAD_DH_P_VALUE), "bad dh p value"},
     {ERR_REASON(SSL_R_BAD_DIGEST_LENGTH), "bad digest length"},
     {ERR_REASON(SSL_R_BAD_DSA_SIGNATURE), "bad dsa signature"},
     {ERR_REASON(SSL_R_BAD_ECC_CERT), "bad ecc cert"},