Enable use of TLSv1.1 and TLSv1.2 for IMAP.

CHANGELOG

@@ -12,6 +12,7 @@ CHANGELOG Roundcube Webmail
 - Fix PHP7 warning "session_start(): Session callback expects true/false return value" (#1490624)
 - Fix XSS issue in SVG images handling (#1490625)
 - Fix missing language name in "Add to Dictionary" request in HTML mode (#1490634)
+- Enable use of TLSv1.1 and TLSv1.2 for IMAP.
 
 RELEASE 1.2-beta
 ----------------

program/lib/Roundcube/rcube_imap_generic.php

@@ -997,7 +997,13 @@ class rcube_imap_generic
                 return false;
             }
 
-            if (!stream_socket_enable_crypto($this->fp, true, STREAM_CRYPTO_METHOD_TLS_CLIENT)) {
+            // There is no flag to enable all TLS methods. Net_SMTP
+            // handles enabling TLS similarly.
+            $crypto_method = STREAM_CRYPTO_METHOD_TLS_CLIENT
+                | @STREAM_CRYPTO_METHOD_TLSv1_1_CLIENT
+                | @STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT;
+
+            if (!stream_socket_enable_crypto($this->fp, true, $crypto_method)) {
                 $this->setError(self::ERROR_BAD, "Unable to negotiate TLS");
                 $this->closeConnection();
                 return false;