Initial server setup and performs initial greeting and hello

cmd/server/main.go

@@ -0,0 +1,32 @@
+/* diodemail - send-only smtp server
+ * Copyright (c) 2024 Gnarwhal
+ *
+ * This file is part of SSHare.
+ *
+ * SSHare is free software: you can redistribute it and/or modify it under the terms of
+ * the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * SSHare is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * SSHare. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package main
+
+import (
+	"log"
+	
+	"forge.monodon.me/Gnarwhal/diodemail/smtp"
+)
+
+func main() {
+	err := smtp.Run(":4650", false)
+	if err != nil {
+		log.Fatal(err)
+	}
+}

go.mod

@@ -1,3 +1,11 @@
 module forge.monodon.me/Gnarwhal/diodemail
 
 go 1.23.1
+
+require github.com/rs/zerolog v1.33.0
+
+require (
+	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mattn/go-isatty v0.0.19 // indirect
+	golang.org/x/sys v0.12.0 // indirect
+)

go.sum

@@ -0,0 +1,15 @@
+github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
+github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
+github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
+github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
+github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
+github.com/mattn/go-isatty v0.0.19 h1:JITubQf0MOLdlGRuRq+jtsDlekdYPia9ZFsB8h/APPA=
+github.com/mattn/go-isatty v0.0.19/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/rs/xid v1.5.0/go.mod h1:trrq9SKmegXys3aeAKXMUTdJsYXVwGY3RLcfgqegfbg=
+github.com/rs/zerolog v1.33.0 h1:1cU2KZkvPxNyfgEmhHAz/1A9Bz+llsdYzklWFzgp0r8=
+github.com/rs/zerolog v1.33.0/go.mod h1:/7mN4D5sKwJLZQ2b/znpjC3/GQWY/xaDXUM0kKWRHss=
+golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.12.0 h1:CM0HF96J0hcLAwsHPJZjfdNzs0gftsLfgKt57wWHJ0o=
+golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=

smtp/connection.go

@@ -0,0 +1,57 @@
+/* diodemail - send-only smtp server
+ * Copyright (c) 2024 Gnarwhal
+ *
+ * This file is part of SSHare.
+ *
+ * SSHare is free software: you can redistribute it and/or modify it under the terms of
+ * the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * SSHare is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * SSHare. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package smtp
+
+import (
+	"net"
+
+	"github.com/rs/zerolog/log"
+)
+
+type Connection struct {
+	connection net.Conn
+}
+
+func (self Connection) Read() (string, error) {
+	buffer := [64]byte{}
+	read, err := self.connection.Read(buffer[:])
+	if err != nil {
+		return "", err
+	}
+
+	message := string(buffer[:read - 2])
+
+	log.Trace().Msgf("%v  -> %v", self.RemoteAddr(), message)
+
+	return message, nil
+}
+
+func (self Connection) Write(message string) error {
+	log.Trace().Msgf("%v <-  %v", self.RemoteAddr(), message[:len(message) - 1])
+	_, err := self.connection.Write([]byte(message))
+	return err
+}
+
+func (self Connection) Close() {
+	self.connection.Close()
+}
+
+func (self Connection) RemoteAddr() net.Addr {
+	return self.connection.RemoteAddr()
+}

smtp/handlers.go

@@ -0,0 +1,103 @@
+/* diodemail - send-only smtp server
+ * Copyright (c) 2024 Gnarwhal
+ *
+ * This file is part of SSHare.
+ *
+ * SSHare is free software: you can redistribute it and/or modify it under the terms of
+ * the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * SSHare is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * SSHare. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package smtp
+
+import (
+	"fmt"
+	"strings"
+)
+
+type Command struct {
+	name string
+	Exec func(Connection)([]Command, error)
+}
+
+func (self Command) Name() string {
+	return self.name
+}
+
+func (self Command) Check(message string) bool {
+	return strings.HasPrefix(message, self.name)
+}
+
+func (self Connection) Chain() error {
+	commands, err := Greet(self)
+	if err != nil {
+		return err
+	}
+	for {
+		message, err := self.Read()
+		if err != nil {
+			return err
+		}
+
+		command_found := false
+		for _, command := range commands {
+			if command.Check(message) {
+				commands, err = command.Exec(self)
+				if err != nil {
+					return err
+				}
+				command_found = true
+				break
+			}
+		}
+		if !command_found {
+			expected := make([]string, len(commands))
+			for index, command := range commands {
+				expected[index] = command.Name()
+			}
+			return fmt.Errorf("Expected one of %v, but got: %v", expected, message)
+		}
+
+		if len(commands) == 0 {
+			break
+		}
+	}
+	return nil
+}
+
+/* --- GREETING RESPONSE --- */
+
+func Greet(connection Connection) ([]Command, error) {
+	err := connection.Write(
+		"220 localhost ESMTP diodemail -- Service ready" + "\n",
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return []Command{
+		Command{ "HELO", Hello },
+		Command{ "EHLO", Hello },
+	}, nil
+}
+
+/* --- HELO/EHLO RESPONSE --- */
+
+func Hello(connection Connection) ([]Command, error) {
+	err := connection.Write(
+		fmt.Sprintf("250 %v is shy", connection.connection.LocalAddr()) + "\n",
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return []Command{}, nil
+}

smtp/server.go

@@ -0,0 +1,69 @@
+/* diodemail - send-only smtp server
+ * Copyright (c) 2024 Gnarwhal
+ *
+ * This file is part of SSHare.
+ *
+ * SSHare is free software: you can redistribute it and/or modify it under the terms of
+ * the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * SSHare is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * SSHare. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package smtp
+
+import (
+	"net"
+	"os"
+
+	"github.com/rs/zerolog"
+	"github.com/rs/zerolog/log"
+)
+
+type PlainListener struct {
+	listener net.Listener
+}
+
+func handle(connection Connection) {
+	log.Info().Msgf("New connection %v", connection.RemoteAddr())
+	defer connection.Close()
+	err := connection.Chain()
+	if err != nil {
+		log.Error().Msgf("Failed to serve %v: %v", connection.RemoteAddr(), err)
+	} else {
+		log.Info().Msgf("Successfully served %v", connection.RemoteAddr())
+	}
+}
+
+func Run(host string, implicit_tls bool) error {
+	log.Logger = zerolog.
+		New(zerolog.ConsoleWriter{Out: os.Stderr}).
+		With().
+		Timestamp().
+		Logger().
+		Level(zerolog.TraceLevel)
+	
+	listener, err := net.Listen("tcp", host)
+	if err != nil {
+		return err
+	}
+
+	for {
+		connection, err := listener.Accept()
+		if err != nil {
+			return err
+		}
+
+		go handle(Connection{connection})
+	}
+}
+
+func (self PlainListener) Close() error {
+	return self.listener.Close()
+}