From 862749f8639e03ffd97b2527a9780602a9f2f838 Mon Sep 17 00:00:00 2001
From: Winni Neessen <wn@neessen.net>
Date: Sat, 7 Jan 2023 11:31:46 +0100
Subject: [PATCH] Fix SMTP AUTH LOGIN method for servers with uncommon success
 messages

This fixes #94 and basically reverts d0f0435. As James points out correctly in #94, we should not assume specific responses from the server. As long as the spec is followed and the server returns the correct SMTP code, we should not do our own magic.

I've also extended the `getTestConnection` method in client_test.go, so that we can specify more test environment options like `TEST_PORT` and `TEST_TLS_SKIP_VERIFY`. This was needed for testing with the ProtonMail Bridge which listens on a different port and has non-trusted certificates.
---
 auth/login.go  | 12 +++---------
 client_test.go | 15 ++++++++++++++-
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/auth/login.go b/auth/login.go
index 50cbc4f..51f9179 100644
--- a/auth/login.go
+++ b/auth/login.go
@@ -9,7 +9,6 @@ import (
 	"errors"
 	"fmt"
 	"net/smtp"
-	"strings"
 )
 
 type loginAuth struct {
@@ -23,10 +22,6 @@ const (
 
 	// ServerRespPassword represents the "Password:" response by the SMTP server
 	ServerRespPassword = "Password:"
-
-	// ServerRespAuthSuccess represents the "Authentication successful:" response that is
-	// by sent by some SMTP servers
-	ServerRespAuthSuccess = "Authentication successful"
 )
 
 // LoginAuth returns an Auth that implements the LOGIN authentication
@@ -70,10 +65,9 @@ func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
 			return []byte(a.username), nil
 		case ServerRespPassword:
 			return []byte(a.password), nil
+		default:
+			return nil, fmt.Errorf("unexpected server response: %s", string(fromServer))
 		}
 	}
-	if strings.HasSuffix(string(fromServer), ServerRespAuthSuccess) {
-		return nil, nil
-	}
-	return nil, fmt.Errorf("unexpected server response: %s", string(fromServer))
+	return nil, nil
 }
diff --git a/client_test.go b/client_test.go
index d7ef11c..b3bed52 100644
--- a/client_test.go
+++ b/client_test.go
@@ -11,6 +11,7 @@ import (
 	"fmt"
 	"net/smtp"
 	"os"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -1087,10 +1088,22 @@ func getTestConnection(auth bool) (*Client, error) {
 	if th == "" {
 		return nil, fmt.Errorf("no TEST_HOST set")
 	}
-	c, err := NewClient(th)
+	tp := 25
+	if tps := os.Getenv("TEST_PORT"); tps != "" {
+		tpi, err := strconv.Atoi(tps)
+		if err == nil {
+			tp = tpi
+		}
+	}
+	sv := false
+	if sve := os.Getenv("TEST_TLS_SKIP_VERIFY"); sve != "" {
+		sv = true
+	}
+	c, err := NewClient(th, WithPort(tp))
 	if err != nil {
 		return c, err
 	}
+	c.tlsconfig.InsecureSkipVerify = sv
 	if auth {
 		st := os.Getenv("TEST_SMTPAUTH_TYPE")
 		if st != "" {