OpenSSL: don't disable security work-around

OpenSSL added a work-around for a SSL 3.0/TLS 1.0 CBC vulnerability
(http://www.openssl.org/~bodo/tls-cbc.txt). In 0.9.6e they added a bit
to SSL_OP_ALL that _disables_ that work-around despite the fact that
SSL_OP_ALL is documented to do "rather harmless" workarounds.

The libcurl code uses the SSL_OP_ALL define and thus logically always
disables the OpenSSL fix.

In order to keep the secure work-around workding, the
SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS bit must not be set and this change
makes sure of this.

Reported by: product-security at Apple

diff --git a/lib/ssluse.c b/lib/ssluse.c
index 3754904f4b5b20421a89b3e386c2e5ab4f034409..014d5b56af29dc2eaf72432f4bbf83cc179f5389 100644 (file)
--- a/lib/ssluse.c
+++ b/lib/ssluse.c
@@ -1545,6 +1545,13 @@ ossl_connect_step1(struct connectdata *conn,
      become ineffective as of OpenSSL 0.9.8q and 1.0.0c. In order to mitigate
      CVE-2010-4180 when using previous OpenSSL versions we no longer enable
      this option regardless of OpenSSL version and SSL_OP_ALL definition.
+
+     OpenSSL added a work-around for a SSL 3.0/TLS 1.0 CBC vulnerability
+     (http://www.openssl.org/~bodo/tls-cbc.txt). In 0.9.6e they added a bit to
+     SSL_OP_ALL that _disables_ that work-around despite the fact that
+     SSL_OP_ALL is documented to do "rather harmless" workarounds. In order to
+     keep the secure work-around, the SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS bit
+     must not be set.
   */
 
   ctx_options = SSL_OP_ALL;
@@ -1558,6 +1565,10 @@ ossl_connect_step1(struct connectdata *conn,
   ctx_options &= ~SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG;
 #endif
 
+#ifdef SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS
+  ctx_options &= ~SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;
+#endif
+
   /* disable SSLv2 in the default case (i.e. allow SSLv3 and TLSv1) */
   if(data->set.ssl.version == CURL_SSLVERSION_DEFAULT)
     ctx_options |= SSL_OP_NO_SSLv2;