Get receiving email a step closer with a modified go-smtp

Gopkg.lock

@@ -40,10 +40,11 @@
   revision = "7e096a0a6197b89989e8cc31016daa67c8c62051"
 
 [[projects]]
-  branch = "master"
+  branch = "8-unauthed-mail"
   name = "github.com/emersion/go-smtp"
   packages = ["."]
-  revision = "a63104657743890cb7c2fd54f15a2725291f6a9f"
+  revision = "b858ceea28e02e5fab171c5f877860ad9080f8b6"
+  source = "https://github.com/lupine/go-smtp"
 
 [[projects]]
   branch = "master"
@@ -52,7 +53,7 @@
     "bcrypt",
     "blowfish"
   ]
-  revision = "91a49db82a88618983a78a06c1cbd4e00ab749ab"
+  revision = "85f98707c97e11569271e4d9b3d397e079c4f4d0"
 
 [[projects]]
   branch = "master"
@@ -81,6 +82,6 @@
 [solve-meta]
   analyzer-name = "dep"
   analyzer-version = 1
-  inputs-digest = "9d6a4c3f6c1568091ba837d3207861ceae7cb7b2d4b5e094d1892ed935bd72cd"
+  inputs-digest = "4f9c6f3cf2ad42694856bc039ddb3a7e78af676f095fc24ef633305fe499c3bf"
   solver-name = "gps-cdcl"
   solver-version = 1

Gopkg.toml

@@ -26,8 +26,9 @@
 
 
 [[constraint]]
-  branch = "master"
+  branch = "8-unauthed-mail"
   name = "github.com/emersion/go-smtp"
+  source = "https://github.com/lupine/go-smtp"
 
 [prune]
   go-tests = true

internal/smtp/server.go

@@ -31,7 +31,7 @@ func NewServer(cancel context.CancelFunc, datastore store.Interface, submission
 	if submission {
 		out.handler = &Sender{}
 		out.server.Addr = ":587"
-		out.allowLogin = true // Only allow login on submission ports
+		out.submission = true // Only allow login on submission ports
 	} else {
 		out.handler = &Receiver{}
 		out.server.Addr = ":25"
@@ -46,7 +46,7 @@ type concrete struct {
 	store      store.Interface
 	server     *smtp.Server
 	handler    Handler
-	allowLogin bool
+	submission bool
 
 	// Session IDs
 	sid uint64
@@ -64,7 +64,7 @@ func (c *concrete) Run() {
 
 // backend implementation for go-smtp
 func (c *concrete) Login(user, pass string) (smtp.User, error) {
-	if !c.allowLogin {
+	if !c.submission {
 		return nil, fmt.Errorf("Login is disabled")
 	}
 
@@ -87,6 +87,23 @@ func (c *concrete) Login(user, pass string) (smtp.User, error) {
 	return session, nil
 }
 
+func (c *concrete) AnonymousLogin() (smtp.User, error) {
+	if c.submission {
+		return nil, smtp.AuthRequiredErr
+	}
+
+	session := &Session{
+		ID:      atomic.AddUint64(&c.sid, uint64(1)),
+		Account: nil,
+		Handler: c.handler,
+	}
+
+	log.Printf("Beginning anonymous %s session %d", c.name, session.ID)
+	// FIXME: TODO: Track ongoing sessions for termination or notifications
+
+	return session, nil
+}
+
 func (c *concrete) Close() error {
 	c.cancel() // FIXME: this doesn't touch the server
 

vendor/github.com/emersion/go-smtp/backend.go

@@ -8,6 +8,10 @@ import (
 type Backend interface {
 	// Authenticate a user.
 	Login(username, password string) (User, error)
+
+	// Called if the client attempts to send mail without logging in first.
+	// Respond with smtp.AuthRequiredErr if you don't want to support this.
+	AnonymousLogin() (User, error)
 }
 
 // An authenticated user.

vendor/github.com/emersion/go-smtp/conn.go

@@ -37,6 +37,10 @@ type Conn struct {
 	locker    sync.Mutex
 }
 
+var (
+	AuthRequiredErr = fmt.Errorf("Please authenticate first.")
+)
+
 func newConn(c net.Conn, s *Server) *Conn {
 	sc := &Conn{
 		server: s,
@@ -64,6 +68,16 @@ func (c *Conn) init() {
 	c.text = textproto.NewConn(rwc)
 }
 
+func (c *Conn) unrecognizedCommand(cmd string) {
+	c.WriteResponse(500, fmt.Sprintf("Syntax error, %v command unrecognized", cmd))
+
+	c.nbrErrors++
+	if c.nbrErrors > 3 {
+		c.WriteResponse(500, "Too many unrecognized commands")
+		c.Close()
+	}
+}
+
 // Commands are dispatched to the appropriate handler functions.
 func (c *Conn) handle(cmd string, arg string) {
 	if cmd == "" {
@@ -94,17 +108,15 @@ func (c *Conn) handle(cmd string, arg string) {
 		c.WriteResponse(221, "Goodnight and good luck")
 		c.Close()
 	case "AUTH":
-		c.handleAuth(arg)
+		if c.server.AuthDisabled {
+			c.unrecognizedCommand(cmd)
+		} else {
+			c.handleAuth(arg)
+		}
 	case "STARTTLS":
 		c.handleStartTLS()
 	default:
-		c.WriteResponse(500, fmt.Sprintf("Syntax error, %v command unrecognized", cmd))
+		c.unrecognizedCommand(cmd)
-
-		c.nbrErrors++
-		if c.nbrErrors > 3 {
-			c.WriteResponse(500, "Too many unrecognized commands")
-			c.Close()
-		}
 	}
 }
 
@@ -118,10 +130,12 @@ func (c *Conn) User() User {
 	return c.user
 }
 
+// Setting the user resets any message beng generated
 func (c *Conn) SetUser(user User) {
 	c.locker.Lock()
 	defer c.locker.Unlock()
 	c.user = user
+	c.msg = &message{}
 }
 
 func (c *Conn) Close() error {
@@ -138,6 +152,11 @@ func (c *Conn) IsTLS() bool {
 	return ok
 }
 
+func (c *Conn) authAllowed() bool {
+	return !c.server.AuthDisabled &&
+		(c.IsTLS() || c.server.AllowInsecureAuth)
+}
+
 // GREET state -> waiting for HELO
 func (c *Conn) handleGreet(enhanced bool, arg string) {
 	if !enhanced {
@@ -163,7 +182,7 @@ func (c *Conn) handleGreet(enhanced bool, arg string) {
 		if c.server.TLSConfig != nil && !c.IsTLS() {
 			caps = append(caps, "STARTTLS")
 		}
-		if c.IsTLS() || c.server.AllowInsecureAuth {
+		if c.authAllowed() {
 			authCap := "AUTH"
 			for name, _ := range c.server.auths {
 				authCap += " " + name
@@ -187,9 +206,15 @@ func (c *Conn) handleMail(arg string) {
 		c.WriteResponse(502, "Please introduce yourself first.")
 		return
 	}
-	if c.msg == nil {
+
-		c.WriteResponse(502, "Please authenticate first.")
+	if c.User() == nil {
-		return
+		user, err := c.server.Backend.AnonymousLogin()
+		if err != nil {
+			c.WriteResponse(502, err.Error())
+			return
+		}
+
+		c.SetUser(user)
 	}
 
 	// Match FROM, while accepting '>' as quoted pair and in double quoted strings
@@ -318,8 +343,6 @@ func (c *Conn) handleAuth(arg string) {
 
 	if c.User() != nil {
 		c.WriteResponse(235, "Authentication succeeded")
-
-		c.msg = &message{}
 	}
 }
 
@@ -421,12 +444,13 @@ func (c *Conn) ReadLine() (string, error) {
 }
 
 func (c *Conn) reset() {
-	if user := c.User(); user != nil {
+	c.locker.Lock()
-		user.Logout()
+	defer c.locker.Unlock()
+
+	if c.user != nil {
+		c.user.Logout()
 	}
 
-	c.locker.Lock()
 	c.user = nil
 	c.msg = nil
-	c.locker.Unlock()
 }

vendor/github.com/emersion/go-smtp/server.go

@@ -27,6 +27,10 @@ type Server struct {
 	AllowInsecureAuth bool
 	Debug             io.Writer
 
+	// If set, the AUTH command will not be advertised and authentication
+	// attempts will be rejected. This setting overrides AllowInsecureAuth.
+	AuthDisabled bool
+
 	// The server backend.
 	Backend Backend