Initial commit

vendor/github.com/emersion/go-imap/server/conn.go

@@ -0,0 +1,383 @@
+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() 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
+}
+
+type conn struct {
+	*imap.Conn
+
+	s         *Server
+	ctx       *Context
+	l         sync.Locker
+	tlsConn   *tls.Conn
+	continues chan bool
+	responses chan imap.WriterTo
+	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)
+
+	tlsConn, _ := c.(*tls.Conn)
+
+	conn := &conn{
+		Conn: imap.NewConn(c, r, w),
+
+		s: s,
+		l: &sync.Mutex{},
+		ctx: &Context{
+			State:     imap.ConnectingState,
+			Responses: responses,
+		},
+		tlsConn:   tlsConn,
+		continues: continues,
+		responses: responses,
+	}
+
+	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()
+	}
+
+	if err := c.Conn.Close(); err != nil {
+		return err
+	}
+
+	close(c.continues)
+
+	c.ctx.State = imap.LogoutState
+	return nil
+}
+
+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 {
+			res := &imap.ContinuationResp{Info: "send literal"}
+			if err := res.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
+		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()
+	}
+}
+
+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.StatusOk,
+		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() error {
+	// 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.StatusBad,
+					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.StatusBad,
+					Info: err.Error(),
+				}
+			} else {
+				var err error
+				res, up, err = c.handleCommand(cmd)
+				if err != nil {
+					res = &imap.StatusResp{
+						Tag:  cmd.Tag,
+						Type: imap.StatusBad,
+						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.StatusOk {
+				if err := up.Upgrade(c); 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)
+	if statusErr, ok := hdlrErr.(*errStatusResp); ok {
+		res = statusErr.resp
+	} else if hdlrErr != nil {
+		res = &imap.StatusResp{
+			Type: imap.StatusNo,
+			Info: hdlrErr.Error(),
+		}
+	} else {
+		res = &imap.StatusResp{
+			Type: imap.StatusOk,
+		}
+	}
+
+	if res != nil {
+		res.Tag = cmd.Tag
+
+		if res.Type == imap.StatusOk && res.Info == "" {
+			res.Info = cmd.Name + " completed"
+		}
+	}
+
+	up, _ = hdlr.(Upgrader)
+	return
+}