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conn.go
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conn.go
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package server
import (
"crypto/tls"
"errors"
"io"
"net"
"sync"
"time"
"github.com/emersion/go-imap"
"github.com/emersion/go-imap/backend"
)
// Conn is a connection to a client.
type Conn interface {
io.Reader
// Server returns this connection's server.
Server() *Server
// Context returns this connection's context.
Context() *Context
// Capabilities returns a list of capabilities enabled for this connection.
Capabilities() []string
// WriteResp writes a response to this connection.
WriteResp(res imap.WriterTo) error
// IsTLS returns true if TLS is enabled.
IsTLS() bool
// TLSState returns the TLS connection state if TLS is enabled, nil otherwise.
TLSState() *tls.ConnectionState
// Upgrade upgrades a connection, e.g. wrap an unencrypted connection with an
// encrypted tunnel.
Upgrade(upgrader imap.ConnUpgrader) error
// Close closes this connection.
Close() error
setTLSConn(*tls.Conn)
silent() *bool // TODO: remove this
serve(Conn) error
commandHandler(cmd *imap.Command) (hdlr Handler, err error)
}
// Context stores a connection's metadata.
type Context struct {
// This connection's current state.
State imap.ConnState
// If the client is logged in, the user.
User backend.User
// If the client has selected a mailbox, the mailbox.
Mailbox backend.Mailbox
// True if the currently selected mailbox has been opened in read-only mode.
MailboxReadOnly bool
// Responses to send to the client.
Responses chan<- imap.WriterTo
// Closed when the client is logged out.
LoggedOut <-chan struct{}
}
type conn struct {
*imap.Conn
conn Conn // With extensions overrides
s *Server
ctx *Context
l sync.Locker
tlsConn *tls.Conn
continues chan bool
responses chan imap.WriterTo
loggedOut chan struct{}
silentVal bool
}
func newConn(s *Server, c net.Conn) *conn {
// Create an imap.Reader and an imap.Writer
continues := make(chan bool)
r := imap.NewServerReader(nil, continues)
w := imap.NewWriter(nil)
responses := make(chan imap.WriterTo)
loggedOut := make(chan struct{})
tlsConn, _ := c.(*tls.Conn)
conn := &conn{
Conn: imap.NewConn(c, r, w),
s: s,
l: &sync.Mutex{},
ctx: &Context{
State: imap.ConnectingState,
Responses: responses,
LoggedOut: loggedOut,
},
tlsConn: tlsConn,
continues: continues,
responses: responses,
loggedOut: loggedOut,
}
if s.Debug != nil {
conn.Conn.SetDebug(s.Debug)
}
if s.MaxLiteralSize > 0 {
conn.Conn.MaxLiteralSize = s.MaxLiteralSize
}
conn.l.Lock()
go conn.send()
return conn
}
func (c *conn) Server() *Server {
return c.s
}
func (c *conn) Context() *Context {
return c.ctx
}
type response struct {
response imap.WriterTo
done chan struct{}
}
func (r *response) WriteTo(w *imap.Writer) error {
err := r.response.WriteTo(w)
close(r.done)
return err
}
func (c *conn) setDeadline() {
if c.s.AutoLogout == 0 {
return
}
dur := c.s.AutoLogout
if dur < MinAutoLogout {
dur = MinAutoLogout
}
t := time.Now().Add(dur)
c.Conn.SetDeadline(t)
}
func (c *conn) WriteResp(r imap.WriterTo) error {
done := make(chan struct{})
c.responses <- &response{r, done}
<-done
c.setDeadline()
return nil
}
func (c *conn) Close() error {
if c.ctx.User != nil {
c.ctx.User.Logout()
}
return c.Conn.Close()
}
func (c *conn) Capabilities() []string {
caps := []string{"IMAP4rev1"}
if c.ctx.State == imap.NotAuthenticatedState {
if !c.IsTLS() && c.s.TLSConfig != nil {
caps = append(caps, "STARTTLS")
}
if !c.canAuth() {
caps = append(caps, "LOGINDISABLED")
} else {
for name := range c.s.auths {
caps = append(caps, "AUTH="+name)
}
}
}
for _, ext := range c.s.extensions {
caps = append(caps, ext.Capabilities(c)...)
}
return caps
}
func (c *conn) send() {
// Send continuation requests
go func() {
for range c.continues {
resp := &imap.ContinuationReq{Info: "send literal"}
if err := resp.WriteTo(c.Writer); err != nil {
c.Server().ErrorLog.Println("cannot send continuation request: ", err)
} else if err := c.Writer.Flush(); err != nil {
c.Server().ErrorLog.Println("cannot flush connection: ", err)
}
}
}()
// Send responses
for {
// Get a response that needs to be sent
select {
case res := <-c.responses:
// Request to send the response
c.l.Lock()
// Send the response
if err := res.WriteTo(c.Writer); err != nil {
c.Server().ErrorLog.Println("cannot send response: ", err)
} else if err := c.Writer.Flush(); err != nil {
c.Server().ErrorLog.Println("cannot flush connection: ", err)
}
c.l.Unlock()
case <-c.loggedOut:
return
}
}
}
func (c *conn) greet() error {
c.ctx.State = imap.NotAuthenticatedState
caps := c.Capabilities()
args := make([]interface{}, len(caps))
for i, cap := range caps {
args[i] = cap
}
greeting := &imap.StatusResp{
Type: imap.StatusRespOk,
Code: imap.CodeCapability,
Arguments: args,
Info: "IMAP4rev1 Service Ready",
}
c.l.Unlock()
defer c.l.Lock()
return c.WriteResp(greeting)
}
func (c *conn) setTLSConn(tlsConn *tls.Conn) {
c.tlsConn = tlsConn
}
func (c *conn) IsTLS() bool {
return c.tlsConn != nil
}
func (c *conn) TLSState() *tls.ConnectionState {
if c.tlsConn != nil {
state := c.tlsConn.ConnectionState()
return &state
}
return nil
}
// canAuth checks if the client can use plain text authentication.
func (c *conn) canAuth() bool {
return c.IsTLS() || c.s.AllowInsecureAuth
}
func (c *conn) silent() *bool {
return &c.silentVal
}
func (c *conn) serve(conn Conn) error {
c.conn = conn
defer func() {
c.ctx.State = imap.LogoutState
close(c.continues)
close(c.loggedOut)
}()
// Send greeting
if err := c.greet(); err != nil {
return err
}
for {
if c.ctx.State == imap.LogoutState {
return nil
}
var res *imap.StatusResp
var up Upgrader
c.Wait()
fields, err := c.ReadLine()
if err == io.EOF || c.ctx.State == imap.LogoutState {
return nil
}
c.setDeadline()
if err != nil {
if imap.IsParseError(err) {
res = &imap.StatusResp{
Type: imap.StatusRespBad,
Info: err.Error(),
}
} else {
c.s.ErrorLog.Println("cannot read command:", err)
return err
}
} else {
cmd := &imap.Command{}
if err := cmd.Parse(fields); err != nil {
res = &imap.StatusResp{
Tag: cmd.Tag,
Type: imap.StatusRespBad,
Info: err.Error(),
}
} else {
var err error
res, up, err = c.handleCommand(cmd)
if err != nil {
res = &imap.StatusResp{
Tag: cmd.Tag,
Type: imap.StatusRespBad,
Info: err.Error(),
}
}
}
}
if res != nil {
c.l.Unlock()
if err := c.WriteResp(res); err != nil {
c.s.ErrorLog.Println("cannot write response:", err)
c.l.Lock()
continue
}
if up != nil && res.Type == imap.StatusRespOk {
if err := up.Upgrade(c.conn); err != nil {
c.s.ErrorLog.Println("cannot upgrade connection:", err)
return err
}
}
c.l.Lock()
}
}
}
func (c *conn) commandHandler(cmd *imap.Command) (hdlr Handler, err error) {
newHandler := c.s.Command(cmd.Name)
if newHandler == nil {
err = errors.New("Unknown command")
return
}
hdlr = newHandler()
err = hdlr.Parse(cmd.Arguments)
return
}
func (c *conn) handleCommand(cmd *imap.Command) (res *imap.StatusResp, up Upgrader, err error) {
hdlr, err := c.commandHandler(cmd)
if err != nil {
return
}
c.l.Unlock()
defer c.l.Lock()
hdlrErr := hdlr.Handle(c.conn)
if statusErr, ok := hdlrErr.(*errStatusResp); ok {
res = statusErr.resp
} else if hdlrErr != nil {
res = &imap.StatusResp{
Type: imap.StatusRespNo,
Info: hdlrErr.Error(),
}
} else {
res = &imap.StatusResp{
Type: imap.StatusRespOk,
}
}
if res != nil {
res.Tag = cmd.Tag
if res.Type == imap.StatusRespOk && res.Info == "" {
res.Info = cmd.Name + " completed"
}
}
up, _ = hdlr.(Upgrader)
return
}