[release-branch.go1.9] net/smtp: NewClient: set tls field to true when already using a TLS connection

Change-Id: I34008f56c191df0edcaafc20d569bbc6184f89fc
Reviewed-on: https://go-review.googlesource.com/68470
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-on: https://go-review.googlesource.com/70982
Run-TryBot: Russ Cox <rsc@golang.org>

src/net/smtp/smtp.go

@@ -67,6 +67,7 @@ func NewClient(conn net.Conn, host string) (*Client, error) {
 		return nil, err
 	}
 	c := &Client{Text: text, conn: conn, serverName: host, localName: "localhost"}
+	_, c.tls = conn.(*tls.Conn)
 	return c, nil
 }
 

src/net/smtp/smtp_test.go

@@ -364,6 +364,53 @@ HELO localhost
 QUIT
 `
 
+func TestNewClientWithTLS(t *testing.T) {
+	cert, err := tls.X509KeyPair(localhostCert, localhostKey)
+	if err != nil {
+		t.Fatalf("loadcert: %v", err)
+	}
+
+	config := tls.Config{Certificates: []tls.Certificate{cert}}
+
+	ln, err := tls.Listen("tcp", "127.0.0.1:0", &config)
+	if err != nil {
+		ln, err = tls.Listen("tcp", "[::1]:0", &config)
+		if err != nil {
+			t.Fatalf("server: listen: %s", err)
+		}
+	}
+
+	go func() {
+		conn, err := ln.Accept()
+		if err != nil {
+			t.Fatalf("server: accept: %s", err)
+			return
+		}
+		defer conn.Close()
+
+		_, err = conn.Write([]byte("220 SIGNS\r\n"))
+		if err != nil {
+			t.Fatalf("server: write: %s", err)
+			return
+		}
+	}()
+
+	config.InsecureSkipVerify = true
+	conn, err := tls.Dial("tcp", ln.Addr().String(), &config)
+	if err != nil {
+		t.Fatalf("client: dial: %s", err)
+	}
+	defer conn.Close()
+
+	client, err := NewClient(conn, ln.Addr().String())
+	if err != nil {
+		t.Fatalf("smtp: newclient: %s", err)
+	}
+	if !client.tls {
+		t.Errorf("client.tls Got: %t Expected: %t", client.tls, true)
+	}
+}
+
 func TestHello(t *testing.T) {
 
 	if len(helloServer) != len(helloClient) {