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68 lines
2.1 KiB
Go
68 lines
2.1 KiB
Go
// SPDX-FileCopyrightText: 2022-2023 The go-mail Authors
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//
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// SPDX-License-Identifier: MIT
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package smtp
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import (
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"errors"
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"fmt"
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)
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// loginAuth is the type that satisfies the Auth interface for the "SMTP LOGIN" auth
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type loginAuth struct {
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username, password string
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host string
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}
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const (
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// ServerRespUsername represents the "Username:" response by the SMTP server
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ServerRespUsername = "Username:"
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// ServerRespPassword represents the "Password:" response by the SMTP server
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ServerRespPassword = "Password:"
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)
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// LoginAuth returns an Auth that implements the LOGIN authentication
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// mechanism as it is used by MS Outlook. The Auth works similar to PLAIN
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// but instead of sending all in one response, the login is handled within
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// 3 steps:
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// - Sending AUTH LOGIN (server responds with "Username:")
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// - Sending the username (server responds with "Password:")
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// - Sending the password (server authenticates)
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//
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// LoginAuth will only send the credentials if the connection is using TLS
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// or is connected to localhost. Otherwise authentication will fail with an
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// error, without sending the credentials.
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func LoginAuth(username, password, host string) Auth {
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return &loginAuth{username, password, host}
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}
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func (a *loginAuth) Start(server *ServerInfo) (string, []byte, error) {
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// Must have TLS, or else localhost server.
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// Note: If TLS is not true, then we can't trust ANYTHING in ServerInfo.
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// In particular, it doesn't matter if the server advertises LOGIN auth.
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// That might just be the attacker saying
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// "it's ok, you can trust me with your password."
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if !server.TLS && !isLocalhost(server.Name) {
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return "", nil, errors.New("unencrypted connection")
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}
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if server.Name != a.host {
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return "", nil, errors.New("wrong host name")
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}
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return "LOGIN", nil, nil
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}
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func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
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if more {
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switch string(fromServer) {
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case ServerRespUsername:
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return []byte(a.username), nil
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case ServerRespPassword:
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return []byte(a.password), nil
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default:
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return nil, fmt.Errorf("unexpected server response: %s", string(fromServer))
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}
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}
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return nil, nil
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}
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