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60 lines
2.1 KiB
Go
60 lines
2.1 KiB
Go
// SPDX-FileCopyrightText: Copyright 2010 The Go Authors. All rights reserved.
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// SPDX-FileCopyrightText: Copyright (c) 2022-2023 The go-mail Authors
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//
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// Original net/smtp code from the Go stdlib by the Go Authors.
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// Use of this source code is governed by a BSD-style
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// LICENSE file that can be found in this directory.
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//
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// go-mail specific modifications by the go-mail Authors.
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// Licensed under the MIT License.
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// See [PROJECT ROOT]/LICENSES directory for more information.
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//
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// SPDX-License-Identifier: BSD-3-Clause AND MIT
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package smtp
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import (
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"errors"
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)
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// plainAuth is the type that satisfies the Auth interface for the "SMTP PLAIN" auth
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type plainAuth struct {
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identity, username, password string
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host string
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}
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// PlainAuth returns an Auth that implements the PLAIN authentication
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// mechanism as defined in RFC 4616. The returned Auth uses the given
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// username and password to authenticate to host and act as identity.
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// Usually identity should be the empty string, to act as username.
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//
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// PlainAuth 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 PlainAuth(identity, username, password, host string) Auth {
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return &plainAuth{identity, username, password, host}
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}
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func (a *plainAuth) 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 PLAIN 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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resp := []byte(a.identity + "\x00" + a.username + "\x00" + a.password)
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return "PLAIN", resp, nil
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}
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func (a *plainAuth) Next(_ []byte, more bool) ([]byte, error) {
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if more {
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// We've already sent everything.
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return nil, errors.New("unexpected server challenge")
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}
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return nil, nil
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}
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