crypto/tls: optional ocspStapling

OptionalCertificateStatus.patch

diff -r 088975427829 src/crypto/tls/handshake_client.go
--- a/src/crypto/tls/handshake_client.go	Wed Nov 19 09:47:56 2014 +1100
+++ b/src/crypto/tls/handshake_client.go	Wed Nov 19 17:57:09 2014 -0600
@@ -276,26 +276,34 @@
 
 	c.peerCertificates = certs
 
-	if hs.serverHello.ocspStapling {
-		msg, err = c.readHandshake()
-		if err != nil {
-			return err
-		}
-		cs, ok := msg.(*certificateStatusMsg)
-		if !ok {
+	msg, err = c.readHandshake()
+	if err != nil {
+		return err
+	}
+
+	cs, ok := msg.(*certificateStatusMsg)
+	if ok {
+		// RFC4366 on Certificate Status Request:
+		// The server MAY return a "certificate_status" message.
+
+		if !hs.serverHello.ocspStapling {
+			// If a server returns a "CertificateStatus" message, then the
+			// server MUST have included an extension of type "status_request"
+			// with empty "extension_data" in the extended server hello.
+
 			c.sendAlert(alertUnexpectedMessage)
-			return unexpectedMessageError(cs, msg)
+			return fmt.Errorf("tls: received unexpected handshake message of type %T", cs)
 		}
 		hs.finishedHash.Write(cs.marshal())
 
 		if cs.statusType == statusTypeOCSP {
 			c.ocspResponse = cs.response
 		}
-	}
 
-	msg, err = c.readHandshake()
-	if err != nil {
-		return err
+		msg, err = c.readHandshake()
+		if err != nil {
+			return err
+		}
 	}
 
 	keyAgreement := hs.suite.ka(c.vers)