...
Run Format

Source file src/net/smtp/smtp.go

Documentation: net/smtp

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

View as plain text