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434 lines (361 loc) · 9.75 KB
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// Package pop3 is a simple POP3 e-mail client library.
package pop3
import (
"bufio"
"bytes"
"crypto/tls"
"errors"
"fmt"
"net"
"strconv"
"strings"
"time"
"github.com/emersion/go-message"
)
// Client implements a Client e-mail client.
type Client struct {
opt Opt
}
// Conn is a stateful connection with the POP3 server/
type Conn struct {
conn net.Conn
r *bufio.Reader
w *bufio.Writer
}
// Opt represents the client configuration.
type Opt struct {
Host string `json:"host"`
Port int `json:"port"`
// Default is 3 seconds.
DialTimeout time.Duration `json:"dial_timeout"`
TLSEnabled bool `json:"tls_enabled"`
TLSSkipVerify bool `json:"tls_skip_verify"`
}
// MessageID contains the ID and size of an individual message.
type MessageID struct {
// ID is the numerical index (non-unique) of the message.
ID int
Size int
// UID is only present if the response is to the UIDL command.
UID string
}
var (
lineBreak = []byte("\r\n")
respOK = []byte("+OK") // `+OK` without additional info
respOKInfo = []byte("+OK ") // `+OK <info>`
respErr = []byte("-ERR") // `-ERR` without additional info
respErrInfo = []byte("-ERR ") // `-ERR <info>`
)
// New returns a new client object using an existing connection.
func New(opt Opt) *Client {
if opt.DialTimeout < time.Millisecond {
opt.DialTimeout = time.Second * 3
}
return &Client{
opt: opt,
}
}
// NewConn creates and returns live POP3 server connection.
func (c *Client) NewConn() (*Conn, error) {
var (
addr = fmt.Sprintf("%s:%d", c.opt.Host, c.opt.Port)
)
conn, err := net.DialTimeout("tcp", addr, c.opt.DialTimeout)
if err != nil {
return nil, err
}
// No TLS.
if c.opt.TLSEnabled {
// Skip TLS host verification.
tlsCfg := tls.Config{}
if c.opt.TLSSkipVerify {
tlsCfg.InsecureSkipVerify = c.opt.TLSSkipVerify
} else {
tlsCfg.ServerName = c.opt.Host
}
conn = tls.Client(conn, &tlsCfg)
}
pCon := &Conn{
conn: conn,
r: bufio.NewReader(conn),
w: bufio.NewWriter(conn),
}
// Verify the connection by reading the welcome +OK greeting.
if _, err := pCon.ReadOne(); err != nil {
return nil, err
}
return pCon, nil
}
// Send sends a POP3 command to the server. The given comand is suffixed with "\r\n".
func (c *Conn) Send(b string) error {
if _, err := c.w.WriteString(b + "\r\n"); err != nil {
return err
}
return c.w.Flush()
}
// Cmd sends a command to the server. POP3 responses are either single line or multi-line.
// The first line always with -ERR in case of an error or +OK in case of a successful operation.
// OK+ is always followed by a response on the same line which is either the actual response data
// in case of single line responses, or a help message followed by multiple lines of actual response
// data in case of multiline responses.
// See https://www.shellhacks.com/retrieve-email-pop3-server-command-line/ for examples.
func (c *Conn) Cmd(cmd string, isMulti bool, args ...interface{}) (*bytes.Buffer, error) {
var cmdLine string
// Repeat a %v to format each arg.
if len(args) > 0 {
format := " " + strings.TrimRight(strings.Repeat("%v ", len(args)), " ")
// CMD arg1 argn ...\r\n
cmdLine = fmt.Sprintf(cmd+format, args...)
} else {
cmdLine = cmd
}
if err := c.Send(cmdLine); err != nil {
return nil, err
}
// Read the first line of response to get the +OK/-ERR status.
b, err := c.ReadOne()
if err != nil {
return nil, err
}
// Single line response.
if !isMulti {
return bytes.NewBuffer(b), err
}
buf, err := c.ReadAll()
return buf, err
}
// ReadOne reads a single line response from the conn.
func (c *Conn) ReadOne() ([]byte, error) {
b, _, err := c.r.ReadLine()
if err != nil {
return nil, err
}
r, err := parseResp(b)
return r, err
}
// ReadAll reads all lines from the connection until the POP3 multiline terminator "." is encountered
// and returns a bytes.Buffer of all the read lines.
func (c *Conn) ReadAll() (*bytes.Buffer, error) {
buf := &bytes.Buffer{}
for {
b, _, err := c.r.ReadLine()
if err != nil {
return nil, err
}
// "." indicates the end of a multi-line response.
if bytes.Equal(b, []byte(".")) {
break
}
if _, err := buf.Write(b); err != nil {
return nil, err
}
if _, err := buf.Write(lineBreak); err != nil {
return nil, err
}
}
return buf, nil
}
// Auth authenticates the given credentials with the server.
func (c *Conn) Auth(user, password string) error {
if err := c.User(user); err != nil {
return err
}
if err := c.Pass(password); err != nil {
return err
}
// Issue a NOOP to force the server to respond to the auth.
// Couresy: github.com/TheCreeper/go-pop3
return c.Noop()
}
// User sends the username to the server.
func (c *Conn) User(s string) error {
_, err := c.Cmd("USER", false, s)
return err
}
// Pass sends the password to the server.
func (c *Conn) Pass(s string) error {
_, err := c.Cmd("PASS", false, s)
return err
}
// Stat returns the number of messages and their total size in bytes in the inbox.
func (c *Conn) Stat() (int, int, error) {
b, err := c.Cmd("STAT", false)
if err != nil {
return 0, 0, err
}
// count size
f := bytes.Fields(b.Bytes())
// Total number of messages.
count, err := strconv.Atoi(string(f[0]))
if err != nil {
return 0, 0, err
}
if count == 0 {
return 0, 0, nil
}
// Total size of all messages in bytes.
size, err := strconv.Atoi(string(f[1]))
if err != nil {
return 0, 0, err
}
return count, size, nil
}
// List returns a list of (message ID, message Size) pairs.
// If the optional msgID > 0, then only that particular message is listed.
// The message IDs are sequential, 1 to N.
func (c *Conn) List(msgID int) ([]MessageID, error) {
var (
buf *bytes.Buffer
err error
)
if msgID <= 0 {
// Multiline response listing all messages.
buf, err = c.Cmd("LIST", true)
} else {
// Single line response listing one message.
buf, err = c.Cmd("LIST", false, msgID)
}
if err != nil {
return nil, err
}
var (
out []MessageID
lines = bytes.Split(buf.Bytes(), lineBreak)
)
for _, l := range lines {
// id size
f := bytes.Fields(l)
if len(f) == 0 {
break
}
id, err := strconv.Atoi(string(f[0]))
if err != nil {
return nil, err
}
size, err := strconv.Atoi(string(f[1]))
if err != nil {
return nil, err
}
out = append(out, MessageID{ID: id, Size: size})
}
return out, nil
}
// Uidl returns a list of (message ID, message UID) pairs. If the optional msgID
// is > 0, then only that particular message is listed. It works like Top() but only works on
// servers that support the UIDL command. Messages size field is not available in the UIDL response.
func (c *Conn) Uidl(msgID int) ([]MessageID, error) {
var (
buf *bytes.Buffer
err error
)
if msgID <= 0 {
// Multiline response listing all messages.
buf, err = c.Cmd("UIDL", true)
} else {
// Single line response listing one message.
buf, err = c.Cmd("UIDL", false, msgID)
}
if err != nil {
return nil, err
}
var (
out []MessageID
lines = bytes.Split(buf.Bytes(), lineBreak)
)
for _, l := range lines {
// id size
f := bytes.Fields(l)
if len(f) == 0 {
break
}
id, err := strconv.Atoi(string(f[0]))
if err != nil {
return nil, err
}
out = append(out, MessageID{ID: id, UID: string(f[1])})
}
return out, nil
}
// Retr downloads a message by the given msgID, parses it and returns it as a
// emersion/go-message.message.Entity object.
func (c *Conn) Retr(msgID int) (*message.Entity, error) {
b, err := c.Cmd("RETR", true, msgID)
if err != nil {
return nil, err
}
m, err := message.Read(b)
if err != nil {
if !message.IsUnknownCharset(err) {
return nil, err
}
}
return m, nil
}
// RetrRaw downloads a message by the given msgID and returns the raw []byte
// of the entire message.
func (c *Conn) RetrRaw(msgID int) (*bytes.Buffer, error) {
b, err := c.Cmd("RETR", true, msgID)
return b, err
}
// Top retrieves a message by its ID with full headers and numLines lines of the body.
func (c *Conn) Top(msgID int, numLines int) (*message.Entity, error) {
b, err := c.Cmd("TOP", true, msgID, numLines)
if err != nil {
return nil, err
}
m, err := message.Read(b)
if err != nil {
return nil, err
}
return m, nil
}
// Dele deletes one or more messages. The server only executes the
// deletions after a successful Quit().
func (c *Conn) Dele(msgID ...int) error {
for _, id := range msgID {
_, err := c.Cmd("DELE", false, id)
if err != nil {
return err
}
}
return nil
}
// Rset clears the messages marked for deletion in the current session.
func (c *Conn) Rset() error {
_, err := c.Cmd("RSET", false)
return err
}
// Noop issues a do-nothing NOOP command to the server. This is useful for
// prolonging open connections.
func (c *Conn) Noop() error {
_, err := c.Cmd("NOOP", false)
return err
}
// Quit sends the QUIT command to server and gracefully closes the connection.
// Message deletions (DELE command) are only excuted by the server on a graceful
// quit and close.
func (c *Conn) Quit() error {
if _, err := c.Cmd("QUIT", false); err != nil {
return err
}
return c.conn.Close()
}
// parseResp checks if the response is an error that starts with `-ERR`
// and returns an error with the message that succeeds the error indicator.
// For success `+OK` messages, it returns the remaining response bytes.
func parseResp(b []byte) ([]byte, error) {
if len(b) == 0 {
return nil, nil
}
if bytes.Equal(b, respOK) {
return nil, nil
} else if bytes.HasPrefix(b, respOKInfo) {
return bytes.TrimPrefix(b, respOKInfo), nil
} else if bytes.Equal(b, respErr) {
return nil, errors.New("unknown error (no info specified in response)")
} else if bytes.HasPrefix(b, respErrInfo) {
return nil, errors.New(string(bytes.TrimPrefix(b, respErrInfo)))
} else {
return nil, fmt.Errorf("unknown response: %s. Neither -ERR, nor +OK", string(b))
}
}