Add support for IMAP STARTTLS

starttls/imap.go

@@ -0,0 +1,67 @@
+/*-
+ * Copyright 2017 Square Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package starttls
+
+import (
+	"bufio"
+	"crypto/tls"
+	"fmt"
+	"net"
+)
+
+func dumpAuthTLSFromIMAP(dialer Dialer, address string, config *tls.Config) (*tls.ConnectionState, error) {
+	c, err := dialer.Dial("tcp", address)
+	if err != nil {
+		return nil, err
+	}
+
+	conn := c.(*net.TCPConn)
+	status, err := readIMAP(conn)
+	if err != nil {
+		return nil, err
+	}
+	if status != "OK" {
+		return nil, fmt.Errorf("IMAP server responded with %s, was expecting OK", status)
+	}
+
+	fmt.Fprintf(conn, "1 STARTTLS\r\n")
+	status, err = readIMAP(conn)
+	if err != nil {
+		return nil, err
+	}
+	if status != "OK" {
+		return nil, fmt.Errorf("IMAP server responded with %s, was expecting OK", status)
+	}
+
+	tlsConn := tls.Client(conn, config)
+	err = tlsConn.Handshake()
+	if err != nil {
+		return nil, err
+	}
+
+	state := tlsConn.ConnectionState()
+	return &state, nil
+}
+
+func readIMAP(conn *net.TCPConn) (string, error) {
+	reader := bufio.NewReader(conn)
+	response, err := reader.ReadString('\n')
+	if err != nil {
+		return "", err
+	}
+	return response[2:4], nil
+}

starttls/starttls.go

@@ -35,7 +35,7 @@ import (
 )
 
 // Protocols are the names of supported protocols
-var Protocols []string = []string{"mysql", "postgres", "psql", "smtp", "ldap", "ftp"}
+var Protocols []string = []string{"mysql", "postgres", "psql", "smtp", "ldap", "ftp", "imap"}
 
 type connectResult struct {
 	state *tls.ConnectionState
@@ -234,6 +234,10 @@ func GetConnectionState(startTLSType, connectName, connectTo, identity, clientCe
 			addr := withDefaultPort(connectTo, 21)
 			state, err = dumpAuthTLSFromFTP(dialer, addr, tlsConfig)
 			res <- connectResult{state, err}
+		case "imap":
+			addr := withDefaultPort(connectTo, 143)
+			state, err = dumpAuthTLSFromIMAP(dialer, addr, tlsConfig)
+			res <- connectResult{state, err}
 		default:
 			res <- connectResult{nil, fmt.Errorf("unknown StartTLS protocol: %s", startTLSType)}
 		}