feat: Rewrite client and server to be more compatible with libmilter/…

…sendmail/postfix

BREAKING CHANGE: Signature changes in Client and Milter. Enhanced state enforcement and error detection can break existing (wrong) code.

.github/workflows/go.yml

@@ -14,15 +14,15 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+      - uses: actions/checkout@v3
 
-    - name: Set up Go
-      uses: actions/setup-go@v3
-      with:
-        go-version: 1.19
+      - name: Set up Go
+        uses: actions/setup-go@v3
+        with:
+          go-version: 1.19
 
-    - name: Build
-      run: go build -v ./...
+      - name: Build
+        run: go build -v ./...
 
-    - name: Test
-      run: go test -v ./...
+      - name: Test
+        run: go test -v ./...

.gitignore

@@ -22,3 +22,5 @@ _testmain.go
 *.exe
 *.test
 *.prof
+
+/.idea

LICENSE

@@ -1,6 +1,8 @@
 BSD 2-Clause License
 
 Copyright (c) 2017 Bozhin Zafirov
+Copyright (c) 2019 Simon Ser
+Copyright (c) 2023 Daniel Jagszent
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without

README.md

@@ -1,10 +1,90 @@
 # go-milter
 
-[![GoDoc](https://godoc.org/github.com/emersion/go-milter?status.svg)](https://godoc.org/github.com/emersion/go-milter)
-[![builds.sr.ht status](https://builds.sr.ht/~emersion/go-milter/commits.svg)](https://builds.sr.ht/~emersion/go-milter/commits?)
+[![GoDoc](https://godoc.org/github.com/d--j/go-milter?status.svg)](https://godoc.org/github.com/d--j/go-milter)
+![Build status](https://github.com/d--j/go-milter/actions/workflows/go.yml/badge.svg?branch=main)
 
 A Go library to write mail filters.
 
+With this library you can write both the client (MTA/SMTP-Server) and server (milter filter)
+in pure Go without sendmail's libmilter.
+
+## Features
+
+* Client & Server support milter protocol version 6 with all features. E.g.:
+  * all milter events including DATA, UNKNOWN, ABORT and QUIT NEW CONNECTION
+  * milter can skip e.g. body chunks when it does not need all chunks
+  * milter can send progress notifications when response can take some time 
+  * milter can automatically instruct the MTA which macros it needs.
+* UTF-8 support
+
+## Usage
+
+```go
+package main
+
+import (
+	"log"
+	"net"
+	"sync"
+
+	"github.com/d--j/go-milter"
+)
+
+type ExampleBackend struct {
+	milter.NoOpMilter
+}
+
+func (b *ExampleBackend) RcptTo(rcptTo string, esmtpArgs string, m *milter.Modifier) (*milter.Response, error) {
+	// reject the mail when it goes to [email protected] and is a local delivery
+	if rcptTo == "[email protected]" && m.Macros.Get(milter.MacroRcptMailer) == "local" {
+		return milter.RejectWithCodeAndReason(550, "We do not like you\r\nvery much, please go away")
+	}
+	return milter.RespContinue, nil
+}
+
+func main() {
+	// create socket to listen on
+	socket, err := net.Listen("tcp4", "127.0.0.1:6785")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer socket.Close()
+
+	// define the backend, required actions, protocol options and macros we want
+	server := milter.NewServer(
+		milter.WithMilter(func() milter.Milter {
+			return &ExampleBackend{}
+		}),
+		milter.WithProtocol(milter.OptNoConnect|milter.OptNoHelo|milter.OptNoMailFrom|milter.OptNoBody|milter.OptNoHeaders|milter.OptNoEOH|milter.OptNoUnknown|milter.OptNoData),
+		milter.WithAction(milter.OptChangeFrom|milter.OptAddRcpt|milter.OptRemoveRcpt),
+		milter.WithMaroRequest(milter.StageRcpt, []milter.MacroName{milter.MacroRcptMailer}),
+	)
+	defer server.Close()
+
+	// start the milter
+	var wgDone sync.WaitGroup
+	wgDone.Add(1)
+	go func(socket net.Listener) {
+		if err := server.Serve(socket); err != nil {
+			log.Fatal(err)
+		}
+		wgDone.Done()
+	}(socket)
+
+	log.Printf("Started milter on %s:%s", socket.Addr().Network(), socket.Addr().String())
+
+	// quit when milter quits
+	wgDone.Wait()
+}
+```
+
+See [![GoDoc](https://godoc.org/github.com/d--j/go-milter?status.svg)](https://godoc.org/github.com/d--j/go-milter) for more documentation and an example for a milter client. 
+
 ## License
 
 BSD 2-Clause
+
+## Credits
+
+Based on https://github.com/emersion/go-milter by [Simon Ser](https://github.com/emersion) which is based on https://github.com/phalaaxx/milter by
+[Bozhin Zafirov](https://github.com/phalaaxx). [Max Mazurov](https://github.com/foxcpp) made major contributions to this code as well.