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+// Copyright 2010 The Go Authors. All rights reserved.
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+// Use of this source code is governed by a BSD-style
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+// license that can be found in the LICENSE file.
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+
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+// Package smtp implements the Simple Mail Transfer Protocol as defined in RFC 5321.
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+// It also implements the following extensions:
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+// 8BITMIME RFC 1652
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+// AUTH RFC 2554
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+// STARTTLS RFC 3207
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+// Additional extensions may be handled by clients.
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+//
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+// The smtp package is frozen and is not accepting new features.
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+// Some external packages provide more functionality. See:
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+//
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+// https://godoc.org/?q=smtp
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+package smtp
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+
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+import (
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+ "crypto/tls"
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+ "encoding/base64"
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+ "errors"
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+ "fmt"
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+ "io"
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+ "net"
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+ "net/textproto"
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+ "strings"
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+)
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+
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+// A Client represents a client connection to an SMTP server.
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+type Client struct {
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+ // Text is the textproto.Conn used by the Client. It is exported to allow for
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+ // clients to add extensions.
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+ Text *textproto.Conn
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+ // keep a reference to the connection so it can be used to create a TLS
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+ // connection later
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+ conn net.Conn
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+ // whether the Client is using TLS
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+ tls bool
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+ serverName string
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+ // map of supported extensions
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+ ext map[string]string
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+ // supported auth mechanisms
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+ auth []string
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+ localName string // the name to use in HELO/EHLO
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+ didHello bool // whether we've said HELO/EHLO
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+ helloError error // the error from the hello
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+}
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+
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+// Dial returns a new Client connected to an SMTP server at addr.
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+// The addr must include a port, as in "mail.example.com:smtp".
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+func Dial(addr string) (*Client, error) {
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+ conn, err := net.Dial("tcp", addr)
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+ if err != nil {
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+ return nil, err
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+ }
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+ host, _, _ := net.SplitHostPort(addr)
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+ return NewClient(conn, host)
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+}
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+
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+// NewClient returns a new Client using an existing connection and host as a
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+// server name to be used when authenticating.
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+func NewClient(conn net.Conn, host string) (*Client, error) {
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+ text := textproto.NewConn(conn)
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+ _, _, err := text.ReadResponse(220)
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+ if err != nil {
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+ text.Close()
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+ return nil, err
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+ }
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+ c := &Client{Text: text, conn: conn, serverName: host, localName: "localhost"}
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+ _, c.tls = conn.(*tls.Conn)
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+ return c, nil
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+}
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+
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+// Close closes the connection.
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+func (c *Client) Close() error {
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+ return c.Text.Close()
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+}
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+
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+// hello runs a hello exchange if needed.
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+func (c *Client) hello() error {
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+ if !c.didHello {
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+ c.didHello = true
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+ err := c.ehlo()
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+ if err != nil {
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+ c.helloError = c.helo()
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+ }
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+ }
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+ return c.helloError
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+}
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+
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+// Hello sends a HELO or EHLO to the server as the given host name.
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+// Calling this method is only necessary if the client needs control
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+// over the host name used. The client will introduce itself as "localhost"
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+// automatically otherwise. If Hello is called, it must be called before
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+// any of the other methods.
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+func (c *Client) Hello(localName string) error {
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+ if err := validateLine(localName); err != nil {
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+ return err
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+ }
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+ if c.didHello {
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+ return errors.New("smtp: Hello called after other methods")
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+ }
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+ c.localName = localName
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+ return c.hello()
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+}
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+
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+// cmd is a convenience function that sends a command and returns the response
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+func (c *Client) cmd(expectCode int, format string, args ...interface{}) (int, string, error) {
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+ id, err := c.Text.Cmd(format, args...)
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+ if err != nil {
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+ return 0, "", err
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+ }
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+ c.Text.StartResponse(id)
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+ defer c.Text.EndResponse(id)
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+ code, msg, err := c.Text.ReadResponse(expectCode)
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+ return code, msg, err
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+}
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+
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+// helo sends the HELO greeting to the server. It should be used only when the
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+// server does not support ehlo.
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+func (c *Client) helo() error {
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+ c.ext = nil
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+ _, _, err := c.cmd(250, "HELO %s", c.localName)
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+ return err
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+}
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+
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+// ehlo sends the EHLO (extended hello) greeting to the server. It
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+// should be the preferred greeting for servers that support it.
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+func (c *Client) ehlo() error {
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+ _, msg, err := c.cmd(250, "EHLO %s", c.localName)
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+ if err != nil {
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+ return err
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+ }
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+ ext := make(map[string]string)
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+ extList := strings.Split(msg, "\n")
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+ if len(extList) > 1 {
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+ extList = extList[1:]
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+ for _, line := range extList {
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+ args := strings.SplitN(line, " ", 2)
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+ if len(args) > 1 {
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+ ext[args[0]] = args[1]
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+ } else {
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+ ext[args[0]] = ""
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+ }
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+ }
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+ }
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+ if mechs, ok := ext["AUTH"]; ok {
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+ c.auth = strings.Split(mechs, " ")
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+ }
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+ c.ext = ext
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+ return err
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+}
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+
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+// StartTLS sends the STARTTLS command and encrypts all further communication.
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+// Only servers that advertise the STARTTLS extension support this function.
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+func (c *Client) StartTLS(config *tls.Config) error {
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+ if err := c.hello(); err != nil {
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+ return err
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+ }
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+ _, _, err := c.cmd(220, "STARTTLS")
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+ if err != nil {
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+ return err
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+ }
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+ c.conn = tls.Client(c.conn, config)
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+ c.Text = textproto.NewConn(c.conn)
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+ c.tls = true
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+ return c.ehlo()
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+}
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+
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+// TLSConnectionState returns the client's TLS connection state.
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+// The return values are their zero values if StartTLS did
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+// not succeed.
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+func (c *Client) TLSConnectionState() (state tls.ConnectionState, ok bool) {
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+ tc, ok := c.conn.(*tls.Conn)
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+ if !ok {
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+ return
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+ }
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+ return tc.ConnectionState(), true
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+}
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+
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+// Verify checks the validity of an email address on the server.
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+// If Verify returns nil, the address is valid. A non-nil return
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+// does not necessarily indicate an invalid address. Many servers
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+// will not verify addresses for security reasons.
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+func (c *Client) Verify(addr string) error {
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+ if err := validateLine(addr); err != nil {
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+ return err
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+ }
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+ if err := c.hello(); err != nil {
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+ return err
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+ }
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+ _, _, err := c.cmd(250, "VRFY %s", addr)
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+ return err
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+}
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+
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+// Auth authenticates a client using the provided authentication mechanism.
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+// A failed authentication closes the connection.
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+// Only servers that advertise the AUTH extension support this function.
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+func (c *Client) Auth(a Auth) error {
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+ if err := c.hello(); err != nil {
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+ return err
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+ }
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+ encoding := base64.StdEncoding
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+ mech, resp, err := a.Start(&ServerInfo{c.serverName, c.tls, c.auth})
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+ if err != nil {
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+ c.Quit()
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+ return err
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+ }
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+ resp64 := make([]byte, encoding.EncodedLen(len(resp)))
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+ encoding.Encode(resp64, resp)
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+ code, msg64, err := c.cmd(0, strings.TrimSpace(fmt.Sprintf("AUTH %s %s", mech, resp64)))
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+ for err == nil {
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+ var msg []byte
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+ switch code {
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+ case 334:
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+ msg, err = encoding.DecodeString(msg64)
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+ case 235:
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+ // the last message isn't base64 because it isn't a challenge
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+ msg = []byte(msg64)
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+ default:
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+ err = &textproto.Error{Code: code, Msg: msg64}
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+ }
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+ if err == nil {
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+ resp, err = a.Next(msg, code == 334)
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+ }
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+ if err != nil {
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+ // abort the AUTH
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+ c.cmd(501, "*")
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+ c.Quit()
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+ break
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+ }
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+ if resp == nil {
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+ break
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+ }
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+ resp64 = make([]byte, encoding.EncodedLen(len(resp)))
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+ encoding.Encode(resp64, resp)
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+ code, msg64, err = c.cmd(0, string(resp64))
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+ }
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+ return err
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+}
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+
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+// Mail issues a MAIL command to the server using the provided email address.
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+// If the server supports the 8BITMIME extension, Mail adds the BODY=8BITMIME
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+// parameter.
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+// This initiates a mail transaction and is followed by one or more Rcpt calls.
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+func (c *Client) Mail(from string) error {
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+ if err := validateLine(from); err != nil {
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+ return err
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+ }
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+ if err := c.hello(); err != nil {
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+ return err
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+ }
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+ cmdStr := "MAIL FROM:<%s>"
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+ if c.ext != nil {
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+ if _, ok := c.ext["8BITMIME"]; ok {
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+ cmdStr += " BODY=8BITMIME"
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+ }
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+ }
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+ _, _, err := c.cmd(250, cmdStr, from)
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+ return err
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+}
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+
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+// Rcpt issues a RCPT command to the server using the provided email address.
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+// A call to Rcpt must be preceded by a call to Mail and may be followed by
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+// a Data call or another Rcpt call.
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+func (c *Client) Rcpt(to string) error {
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+ if err := validateLine(to); err != nil {
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+ return err
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+ }
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+ _, _, err := c.cmd(25, "RCPT TO:<%s>", to)
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+ return err
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+}
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+
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+type dataCloser struct {
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+ c *Client
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+ io.WriteCloser
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+}
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+
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+func (d *dataCloser) Close() error {
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+ d.WriteCloser.Close()
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+ _, _, err := d.c.Text.ReadResponse(250)
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+ return err
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+}
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+
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+// Data issues a DATA command to the server and returns a writer that
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+// can be used to write the mail headers and body. The caller should
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+// close the writer before calling any more methods on c. A call to
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+// Data must be preceded by one or more calls to Rcpt.
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+func (c *Client) Data() (io.WriteCloser, error) {
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+ _, _, err := c.cmd(354, "DATA")
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+ if err != nil {
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+ return nil, err
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+ }
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+ return &dataCloser{c, c.Text.DotWriter()}, nil
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+}
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+
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+var testHookStartTLS func(*tls.Config) // nil, except for tests
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+
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+// SendMail connects to the server at addr, switches to TLS if
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+// possible, authenticates with the optional mechanism a if possible,
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+// and then sends an email from address from, to addresses to, with
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+// message msg.
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+// The addr must include a port, as in "mail.example.com:smtp".
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+//
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+// The addresses in the to parameter are the SMTP RCPT addresses.
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+//
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+// The msg parameter should be an RFC 822-style email with headers
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+// first, a blank line, and then the message body. The lines of msg
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+// should be CRLF terminated. The msg headers should usually include
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+// fields such as "From", "To", "Subject", and "Cc". Sending "Bcc"
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+// messages is accomplished by including an email address in the to
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+// parameter but not including it in the msg headers.
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+//
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+// The SendMail function and the net/smtp package are low-level
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+// mechanisms and provide no support for DKIM signing, MIME
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+// attachments (see the mime/multipart package), or other mail
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+// functionality. Higher-level packages exist outside of the standard
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+// library.
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+func SendMail(addr string, a Auth, from string, to []string, msg []byte) error {
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+ if err := validateLine(from); err != nil {
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+ return err
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+ }
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+ for _, recp := range to {
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+ if err := validateLine(recp); err != nil {
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+ return err
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+ }
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+ }
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+ c, err := Dial(addr)
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+ if err != nil {
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+ return err
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+ }
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+ defer c.Close()
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+ if err = c.hello(); err != nil {
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+ return err
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+ }
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+ if ok, _ := c.Extension("STARTTLS"); ok {
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+ config := &tls.Config{ServerName: c.serverName}
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+ if testHookStartTLS != nil {
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+ testHookStartTLS(config)
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+ }
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+ if err = c.StartTLS(config); err != nil {
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+ return err
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+ }
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+ }
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+ if a != nil && c.ext != nil {
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+ if _, ok := c.ext["AUTH"]; !ok {
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+ return errors.New("smtp: server doesn't support AUTH")
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+ }
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349
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+ if err = c.Auth(a); err != nil {
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+ return err
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+ }
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+ }
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+ if err = c.Mail(from); err != nil {
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+ return err
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+ }
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+ for _, addr := range to {
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+ if err = c.Rcpt(addr); err != nil {
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+ return err
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+ }
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+ }
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+ w, err := c.Data()
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+ if err != nil {
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+ return err
|
|
364
|
+ }
|
|
365
|
+ _, err = w.Write(msg)
|
|
366
|
+ if err != nil {
|
|
367
|
+ return err
|
|
368
|
+ }
|
|
369
|
+ err = w.Close()
|
|
370
|
+ if err != nil {
|
|
371
|
+ return err
|
|
372
|
+ }
|
|
373
|
+ return c.Quit()
|
|
374
|
+}
|
|
375
|
+
|
|
376
|
+// Extension reports whether an extension is support by the server.
|
|
377
|
+// The extension name is case-insensitive. If the extension is supported,
|
|
378
|
+// Extension also returns a string that contains any parameters the
|
|
379
|
+// server specifies for the extension.
|
|
380
|
+func (c *Client) Extension(ext string) (bool, string) {
|
|
381
|
+ if err := c.hello(); err != nil {
|
|
382
|
+ return false, ""
|
|
383
|
+ }
|
|
384
|
+ if c.ext == nil {
|
|
385
|
+ return false, ""
|
|
386
|
+ }
|
|
387
|
+ ext = strings.ToUpper(ext)
|
|
388
|
+ param, ok := c.ext[ext]
|
|
389
|
+ return ok, param
|
|
390
|
+}
|
|
391
|
+
|
|
392
|
+// Reset sends the RSET command to the server, aborting the current mail
|
|
393
|
+// transaction.
|
|
394
|
+func (c *Client) Reset() error {
|
|
395
|
+ if err := c.hello(); err != nil {
|
|
396
|
+ return err
|
|
397
|
+ }
|
|
398
|
+ _, _, err := c.cmd(250, "RSET")
|
|
399
|
+ return err
|
|
400
|
+}
|
|
401
|
+
|
|
402
|
+// Noop sends the NOOP command to the server. It does nothing but check
|
|
403
|
+// that the connection to the server is okay.
|
|
404
|
+func (c *Client) Noop() error {
|
|
405
|
+ if err := c.hello(); err != nil {
|
|
406
|
+ return err
|
|
407
|
+ }
|
|
408
|
+ _, _, err := c.cmd(250, "NOOP")
|
|
409
|
+ return err
|
|
410
|
+}
|
|
411
|
+
|
|
412
|
+// Quit sends the QUIT command and closes the connection to the server.
|
|
413
|
+func (c *Client) Quit() error {
|
|
414
|
+ if err := c.hello(); err != nil {
|
|
415
|
+ return err
|
|
416
|
+ }
|
|
417
|
+ _, _, err := c.cmd(221, "QUIT")
|
|
418
|
+ if err != nil {
|
|
419
|
+ return err
|
|
420
|
+ }
|
|
421
|
+ return c.Text.Close()
|
|
422
|
+}
|
|
423
|
+
|
|
424
|
+// validateLine checks to see if a line has CR or LF as per RFC 5321
|
|
425
|
+func validateLine(line string) error {
|
|
426
|
+ if strings.ContainsAny(line, "\n\r") {
|
|
427
|
+ return errors.New("smtp: A line must not contain CR or LF")
|
|
428
|
+ }
|
|
429
|
+ return nil
|
|
430
|
+}
|