Reject certificates with embedded NULLs in the commonName field. This stops

attacks where an attacker would put <attack>\0<propername> in the field and
trick the validation code that the certificate was for <attack>.

This is a very low risk attack since it reuqires the attacker to trick the
CA into issuing a certificate with an incorrect field, and the common
PostgreSQL deployments are with private CAs, and not external ones. Also,
default mode in 8.4 does not do any name validation, and is thus also not
vulnerable - but the higher security modes are.

Backpatch all the way. Even though versions 8.3.x and before didn't have
certificate name validation support, they still exposed this field for
the user to perform the validation in the application code, and there
is no way to detect this problem through that API.

Security: CVE-2009-4034

diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index ef2db7f17456a3cba37f35ee5a7bad9d78bca411..3e4756f1c7c2e27847ca2e732efddd4132d4f6be 100644 (file)
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/libpq/be-secure.c,v 1.92 2009/06/11 14:48:58 momjian Exp $
+ *       $PostgreSQL: pgsql/src/backend/libpq/be-secure.c,v 1.93 2009/12/09 06:37:06 mha Exp $
  *
  *       Since the server static private key ($DataDir/server.key)
  *       will normally be stored unencrypted so that the database
@@ -953,9 +953,29 @@ aloop:
                X509_NAME_oneline(X509_get_subject_name(port->peer),
                                                  port->peer_dn, sizeof(port->peer_dn));
                port->peer_dn[sizeof(port->peer_dn) - 1] = '\0';
-               X509_NAME_get_text_by_NID(X509_get_subject_name(port->peer),
+               r = X509_NAME_get_text_by_NID(X509_get_subject_name(port->peer),
                                           NID_commonName, port->peer_cn, sizeof(port->peer_cn));
                port->peer_cn[sizeof(port->peer_cn) - 1] = '\0';
+               if (r == -1)
+               {
+                       /* Unable to get the CN, set it to blank so it can't be used */
+                       port->peer_cn[0] = '\0';
+               }
+               else
+               {
+                       /*
+                        * Reject embedded NULLs in certificate common name to prevent attacks like
+                        * CVE-2009-4034.
+                        */
+                       if (r != strlen(port->peer_cn))
+                       {
+                               ereport(COMMERROR,
+                                               (errcode(ERRCODE_PROTOCOL_VIOLATION),
+                                                errmsg("SSL certificate's common name contains embedded null")));
+                               close_SSL(port);
+                               return -1;
+                       }
+               }
        }
        ereport(DEBUG2,
                        (errmsg("SSL connection from \"%s\"", port->peer_cn)));

diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index dbd37d50390d7aa6a92591dd2289151442c4b5d0..6f6052b2b05d378cbb0d7f5df1f77a04dd8f5e9a 100644 (file)
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/interfaces/libpq/fe-secure.c,v 1.128 2009/07/24 17:58:31 tgl Exp $
+ *       $PostgreSQL: pgsql/src/interfaces/libpq/fe-secure.c,v 1.129 2009/12/09 06:37:06 mha Exp $
  *
  * NOTES
  *
@@ -1265,9 +1265,28 @@ open_client_SSL(PGconn *conn)
                                          conn->peer_dn, sizeof(conn->peer_dn));
        conn->peer_dn[sizeof(conn->peer_dn) - 1] = '\0';
 
-       X509_NAME_get_text_by_NID(X509_get_subject_name(conn->peer),
+       r = X509_NAME_get_text_by_NID(X509_get_subject_name(conn->peer),
                                                          NID_commonName, conn->peer_cn, SM_USER);
-       conn->peer_cn[SM_USER] = '\0';
+       conn->peer_cn[SM_USER] = '\0'; /* buffer is SM_USER+1 chars! */
+       if (r == -1)
+       {
+               /* Unable to get the CN, set it to blank so it can't be used */
+               conn->peer_cn[0] = '\0';
+       }
+       else
+       {
+               /*
+                * Reject embedded NULLs in certificate common name to prevent attacks like
+                * CVE-2009-4034.
+                */
+               if (r != strlen(conn->peer_cn))
+               {
+                       printfPQExpBuffer(&conn->errorMessage,
+                                                         libpq_gettext("SSL certificate's common name contains embedded null\n"));
+                       close_SSL(conn);
+                       return PGRES_POLLING_FAILED;
+               }
+       }
 
        if (!verify_peer_name_matches_certificate(conn))
        {