1 files changed, 106 insertions, 0 deletions
diff --git a/services/auth/source/smtp/auth.go b/services/auth/source/smtp/auth.go
new file mode 100644
index 0000000..6446fcd
--- /dev/null
+++ b/services/auth/source/smtp/auth.go
@@ -0,0 +1,106 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package smtp
+
+import (
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"net"
+	"net/smtp"
+	"os"
+	"strconv"
+)
+
+//   _________   __________________________
+//  /   _____/  /     \__    ___/\______   \
+//  \_____  \  /  \ /  \|    |    |     ___/
+//  /        \/    Y    \    |    |    |
+// /_______  /\____|__  /____|    |____|
+//         \/         \/
+
+type loginAuthenticator struct {
+	username, password string
+}
+
+func (auth *loginAuthenticator) Start(server *smtp.ServerInfo) (string, []byte, error) {
+	return "LOGIN", []byte(auth.username), nil
+}
+
+func (auth *loginAuthenticator) Next(fromServer []byte, more bool) ([]byte, error) {
+	if more {
+		switch string(fromServer) {
+		case "Username:":
+			return []byte(auth.username), nil
+		case "Password:":
+			return []byte(auth.password), nil
+		}
+	}
+	return nil, nil
+}
+
+// SMTP authentication type names.
+const (
+	PlainAuthentication   = "PLAIN"
+	LoginAuthentication   = "LOGIN"
+	CRAMMD5Authentication = "CRAM-MD5"
+)
+
+// Authenticators contains available SMTP authentication type names.
+var Authenticators = []string{PlainAuthentication, LoginAuthentication, CRAMMD5Authentication}
+
+// ErrUnsupportedLoginType login source is unknown error
+var ErrUnsupportedLoginType = errors.New("Login source is unknown")
+
+// Authenticate performs an SMTP authentication.
+func Authenticate(a smtp.Auth, source *Source) error {
+	tlsConfig := &tls.Config{
+		InsecureSkipVerify: source.SkipVerify,
+		ServerName:         source.Host,
+	}
+
+	conn, err := net.Dial("tcp", net.JoinHostPort(source.Host, strconv.Itoa(source.Port)))
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+
+	if source.UseTLS() {
+		conn = tls.Client(conn, tlsConfig)
+	}
+
+	client, err := smtp.NewClient(conn, source.Host)
+	if err != nil {
+		return fmt.Errorf("failed to create NewClient: %w", err)
+	}
+	defer client.Close()
+
+	if !source.DisableHelo {
+		hostname := source.HeloHostname
+		if len(hostname) == 0 {
+			hostname, err = os.Hostname()
+			if err != nil {
+				return fmt.Errorf("failed to find Hostname: %w", err)
+			}
+		}
+
+		if err = client.Hello(hostname); err != nil {
+			return fmt.Errorf("failed to send Helo: %w", err)
+		}
+	}
+
+	// If not using SMTPS, always use STARTTLS if available
+	hasStartTLS, _ := client.Extension("STARTTLS")
+	if !source.UseTLS() && hasStartTLS {
+		if err = client.StartTLS(tlsConfig); err != nil {
+			return fmt.Errorf("failed to start StartTLS: %w", err)
+		}
+	}
+
+	if ok, _ := client.Extension("AUTH"); ok {
+		return client.Auth(a)
+	}
+
+	return ErrUnsupportedLoginType
+}