Make SSL False Start work with asynchronous certificate validation

net/third_party/nss/ssl/ssl.h

Index: net/third_party/nss/ssl/ssl.h
===================================================================
--- net/third_party/nss/ssl/ssl.h	(revision 227672)
+++ net/third_party/nss/ssl/ssl.h	(working copy)
@@ -121,14 +121,17 @@
 #define SSL_ENABLE_FALSE_START         22 /* Enable SSL false start (off by */
                                           /* default, applies only to       */
                                           /* clients). False start is a     */
-/* mode where an SSL client will start sending application data before      */
-/* verifying the server's Finished message. This means that we could end up */
-/* sending data to an imposter. However, the data will be encrypted and     */
-/* only the true server can derive the session key. Thus, so long as the    */
-/* cipher isn't broken this is safe. Because of this, False Start will only */
-/* occur on RSA or DH ciphersuites where the cipher's key length is >= 80   */
-/* bits. The advantage of False Start is that it saves a round trip for     */
-/* client-speaks-first protocols when performing a full handshake.          */
+/* mode where an SSL client will start sending application data before
+ * verifying the server's Finished message. This means that we could end up
+ * sending data to an imposter. However, the data will be encrypted and
+ * only the true server can derive the session key. Thus, so long as the
+ * cipher isn't broken this is safe. The advantage of false start is that
+ * it saves a round trip for client-speaks-first protocols when performing a
+ * full handshake.
+ *
+ * In addition to enabling this option, the application must register a
+ * callback using the SSL_SetCanFalseStartCallback function.
+ */
 
 /* For SSL 3.0 and TLS 1.0, by default we prevent chosen plaintext attacks
  * on SSL CBC mode cipher suites (see RFC 4346 Section F.3) by splitting
@@ -741,14 +744,45 @@
 SSL_IMPORT SECStatus SSL_InheritMPServerSIDCache(const char * envString);
 
 /*
-** Set the callback on a particular socket that gets called when we finish
-** performing a handshake.
+** Set the callback that gets called when a TLS handshake is complete. The
+** handshake callback is called after verifying the peer's Finished message and
+** before processing incoming application data.
+**
+** For the initial handshake: If the handshake false started (see
+** SSL_ENABLE_FALSE_START), then application data may already have been sent
+** before the handshake callback is called. If we did not false start then the
+** callback will get called before any application data is sent.
 */
 typedef void (PR_CALLBACK *SSLHandshakeCallback)(PRFileDesc *fd,
                                                  void *client_data);
 SSL_IMPORT SECStatus SSL_HandshakeCallback(PRFileDesc *fd, 
 			          SSLHandshakeCallback cb, void *client_data);
 
+/* Applications that wish to enable TLS false start must set this callback
+** function. NSS will invoke the functon to determine if a particular
+** connection should use false start or not. SECSuccess indicates that the
+** callback completed successfully, and if so *canFalseStart indicates if false
+** start can be used. If the callback does not return SECSuccess then the
+** handshake will be canceled. NSS's recommended criteria can be evaluated by
+** calling SSL_RecommendedCanFalseStart.
+**
+** If no false start callback is registered then false start will never be
+** done, even if the SSL_ENABLE_FALSE_START option is enabled.
+**/
+typedef SECStatus (PR_CALLBACK *SSLCanFalseStartCallback)(
+    PRFileDesc *fd, void *arg, PRBool *canFalseStart);
+
+SSL_IMPORT SECStatus SSL_SetCanFalseStartCallback(
+    PRFileDesc *fd, SSLCanFalseStartCallback callback, void *arg);
+
+/* This function sets *canFalseStart according to the recommended criteria for
+** false start. These criteria may change from release to release and may depend
+** on which handshake features have been negotiated and/or properties of the
+** certifciates/keys used on the connection.
+*/
+SSL_IMPORT SECStatus SSL_RecommendedCanFalseStart(PRFileDesc *fd,
+                                                  PRBool *canFalseStart);
+
 /*
 ** For the server, request a new handshake.  For the client, begin a new
 ** handshake.  If flushCache is non-zero, the SSL3 cache entry will be