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 b854d4337c7d191b0f7f1b6296eac064898f16dc..589424c6dd4e515c1a44602f10b5eacdba59848d 100644 (file)
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/libpq/be-secure.c,v 1.43.2.5 2009/01/28 15:06:48 mha Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/libpq/be-secure.c,v 1.43.2.6 2009/12/09 06:37:09 mha Exp $
  *
  *       Since the server static private key ($DataDir/server.key)
  *       will normally be stored unencrypted so that the database
@@ -801,12 +801,34 @@ open_server_SSL(Port *port)
        }
        else
        {
+               int r;
+
                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 3a445b780d030aa1ba80e501800bc2987d65ca50..ed85c452d450408d2863daeb15d845990eb97c54 100644 (file)
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-secure.c,v 1.32.2.2 2009/01/28 15:06:48 mha Exp $
+ *       $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-secure.c,v 1.32.2.3 2009/12/09 06:37:09 mha Exp $
  *
  * NOTES
  *       The client *requires* a valid server certificate.  Since
@@ -967,9 +967,28 @@ 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;
+               }
+       }
 
        /* verify that the common name resolves to peer */