Bump used Go versions to 1.17

Bump chrj/smtpd from 0.3.0 to 0.3.1

.github/workflows/codeql-analysis.yml

@@ -25,7 +25,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v2
+      uses: actions/checkout@v2.4.0
       with:
         # We must fetch at least the immediate parents so that if this is
         # a pull request then we can checkout the head.

.github/workflows/go.yml

@@ -7,14 +7,14 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - name: Set up Go 1.15
-      uses: actions/setup-go@v2.1.3
+    - name: Set up Go 1.17
+      uses: actions/setup-go@v2.1.4
       with:
-        go-version: 1.15
+        go-version: 1.17
       id: go
 
     - name: Check out code into the Go module directory
-      uses: actions/checkout@v1
+      uses: actions/checkout@v2.4.0
 
     - name: Get dependencies
       run: |

.github/workflows/release.yaml

@@ -13,18 +13,18 @@ jobs:
         goos: [freebsd, linux, windows]
         goarch: ["386", amd64]
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v2.4.0
     
     - name: Set APP_VERSION env
       run: echo APP_VERSION=$(echo ${GITHUB_REF} | rev | cut -d'/' -f 1 | rev ) >> ${GITHUB_ENV}
     - name: Set BUILD_TIME env
       run: echo BUILD_TIME=$(date) >> ${GITHUB_ENV}
       
-    - uses: wangyoucao577/go-release-action@v1.15
+    - uses: wangyoucao577/go-release-action@v1.21
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
         goos: ${{ matrix.goos }}
         goarch: ${{ matrix.goarch }}
-        goversion: "https://golang.org/dl/go1.15.8.linux-amd64.tar.gz"
+        goversion: "https://golang.org/dl/go1.17.3.linux-amd64.tar.gz"
         extra_files: LICENSE README.md smtprelay.ini
         ldflags: -s -w -X "main.appVersion=${{ env.APP_VERSION }}" -X "main.buildTime=${{ env.BUILD_TIME }}"

config.go

@@ -3,11 +3,12 @@ package main
 import (
 	"flag"
 	"net"
-	"regexp"
 	"net/smtp"
+	"regexp"
+	"strings"
 
-	"github.com/vharitonsky/iniflags"
 	"github.com/sirupsen/logrus"
+	"github.com/vharitonsky/iniflags"
 )
 
 var (
@@ -21,7 +22,8 @@ var (
 	logLevel          = flag.String("log_level", "info", "Minimum log level to output")
 	hostName          = flag.String("hostname", "localhost.localdomain", "Server hostname")
 	welcomeMsg        = flag.String("welcome_msg", "", "Welcome message for SMTP session")
-	listen            = flag.String("listen", "127.0.0.1:25 [::1]:25", "Address and port to listen for incoming SMTP")
+	listenStr         = flag.String("listen", "127.0.0.1:25 [::1]:25", "Address and port to listen for incoming SMTP")
+	listenAddrs       = []protoAddr{}
 	localCert         = flag.String("local_cert", "", "SSL certificate for STARTTLS/TLS")
 	localKey          = flag.String("local_key", "", "SSL private key for STARTTLS/TLS")
 	localForceTLS     = flag.Bool("local_forcetls", false, "Force STARTTLS (needs local_cert and local_key)")
@@ -32,6 +34,7 @@ var (
 	allowedRecipStr   = flag.String("allowed_recipients", "", "Regular expression for valid TO EMail addresses")
 	allowedRecipients *regexp.Regexp
 	allowedUsers      = flag.String("allowed_users", "", "Path to file with valid users/passwords")
+	command           = flag.String("command", "", "Path to pipe command")
 	remoteHost        = flag.String("remote_host", "", "Outgoing SMTP server")
 	remoteUser        = flag.String("remote_user", "", "Username for authentication on outgoing SMTP server")
 	remotePass        = flag.String("remote_pass", "", "Password for authentication on outgoing SMTP server")
@@ -41,6 +44,9 @@ var (
 	versionInfo       = flag.Bool("version", false, "Show version information")
 )
 
+func localAuthRequired() bool {
+	return *allowedUsers != ""
+}
 
 func setupAllowedNetworks() {
 	for _, netstr := range splitstr(*allowedNetsStr, ' ') {
@@ -55,7 +61,7 @@ func setupAllowedNetworks() {
 		// meaning the address refers to a host and not a network.
 		if !allowedNet.IP.Equal(baseIP) {
 			log.WithFields(logrus.Fields{
-				"given_net": netstr,
+				"given_net":  netstr,
 				"proper_net": allowedNet,
 			}).Fatal("Invalid network in allowed_nets (host bits set)")
 		}
@@ -67,7 +73,7 @@ func setupAllowedNetworks() {
 func setupAllowedPatterns() {
 	var err error
 
-	if (*allowedSenderStr != "") {
+	if *allowedSenderStr != "" {
 		allowedSender, err = regexp.Compile(*allowedSenderStr)
 		if err != nil {
 			log.WithField("allowed_sender", *allowedSenderStr).
@@ -76,7 +82,7 @@ func setupAllowedPatterns() {
 		}
 	}
 
-	if (*allowedRecipStr != "") {
+	if *allowedRecipStr != "" {
 		allowedRecipients, err = regexp.Compile(*allowedRecipStr)
 		if err != nil {
 			log.WithField("allowed_recipients", *allowedRecipStr).
@@ -86,7 +92,6 @@ func setupAllowedPatterns() {
 	}
 }
 
-
 func setupRemoteAuth() {
 	logger := log.WithField("remote_auth", *remoteAuthStr)
 
@@ -117,7 +122,7 @@ func setupRemoteAuth() {
 	host, _, err := net.SplitHostPort(*remoteHost)
 	if err != nil {
 		logger.WithField("remote_host", *remoteHost).
-			   Fatal("Invalid remote_host")
+			Fatal("Invalid remote_host")
 	}
 
 	switch *remoteAuthStr {
@@ -130,17 +135,50 @@ func setupRemoteAuth() {
 	}
 }
 
+type protoAddr struct {
+	protocol string
+	address  string
+}
+
+func splitProto(s string) protoAddr {
+	idx := strings.Index(s, "://")
+	if idx == -1 {
+		return protoAddr{
+			address: s,
+		}
+	}
+	return protoAddr{
+		protocol: s[0:idx],
+		address:  s[idx+3:],
+	}
+}
+
+func setupListeners() {
+	for _, listenAddr := range strings.Split(*listenStr, " ") {
+		pa := splitProto(listenAddr)
+
+		if localAuthRequired() && pa.protocol == "" {
+			log.WithField("address", pa.address).
+				Fatal("Local authentication (via allowed_users file) " +
+					"not allowed with non-TLS listener")
+		}
+
+		listenAddrs = append(listenAddrs, pa)
+	}
+}
+
 func ConfigLoad() {
 	iniflags.Parse()
 
 	// Set up logging as soon as possible
 	setupLogger()
 
-	if (*remoteHost == "") {
-		log.Warn("remote_host not set; mail will not be forwarded!")
+	if *remoteHost == "" && *command == "" {
+		log.Warn("no remote_host or command set; mail will not be forwarded!")
 	}
 
 	setupAllowedNetworks()
 	setupAllowedPatterns()
 	setupRemoteAuth()
+	setupListeners()
 }

config_test.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestSplitProto(t *testing.T) {
+	var tests = []struct {
+		input string
+		proto string
+		addr  string
+	}{
+		{
+			input: "localhost",
+			proto: "",
+			addr:  "localhost",
+		},
+		{
+			input: "tls://my.local.domain",
+			proto: "tls",
+			addr:  "my.local.domain",
+		},
+		{
+			input: "starttls://my.local.domain",
+			proto: "starttls",
+			addr:  "my.local.domain",
+		},
+	}
+
+	for i, test := range tests {
+		testName := test.input
+		t.Run(testName, func(t *testing.T) {
+			pa := splitProto(test.input)
+			if pa.protocol != test.proto {
+				t.Errorf("Testcase %d: Incorrect proto: expected %v, got %v",
+					i, test.proto, pa.protocol)
+			}
+			if pa.address != test.addr {
+				t.Errorf("Testcase %d: Incorrect addr: expected %v, got %v",
+					i, test.addr, pa.address)
+			}
+		})
+	}
+}

go.mod

@@ -1,8 +1,8 @@
 module github.com/decke/smtprelay
 
 require (
-	github.com/chrj/smtpd v0.3.0
-	github.com/google/uuid v1.2.0
+	github.com/chrj/smtpd v0.3.1
+	github.com/google/uuid v1.3.0
 	github.com/sirupsen/logrus v1.8.1
 	github.com/vharitonsky/iniflags v0.0.0-20180513140207-a33cd0b5f3de
 	golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad

go.sum

@@ -1,10 +1,9 @@
-github.com/chrj/smtpd v0.3.0 h1:cw1LSHDOz7N3XbkcZSF/bue9dh7ATKk5ZksfBztV6b0=
-github.com/chrj/smtpd v0.3.0/go.mod h1:1hmG9KbrE10JG1SmvG79Krh4F6713oUrw2+gRp1oSYk=
+github.com/chrj/smtpd v0.3.1 h1:kogHFkbFdKaoH3bgZkqNC9uVtKYOFfM3uV3rroBdooE=
+github.com/chrj/smtpd v0.3.1/go.mod h1:JtABvV/LzvLmEIzy0NyDnrfMGOMd8wy5frAokwf6J9Q=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/eaigner/dkim v0.0.0-20150301120808-6fe4a7ee9cfb/go.mod h1:FSCIHbrqk7D01Mj8y/jW+NS1uoCerr+ad+IckTHTFf4=
-github.com/google/uuid v1.2.0 h1:qJYtXnJRWmpe7m/3XlyhrsLrEURqHRM2kxzoxXqyUDs=
-github.com/google/uuid v1.2.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/google/uuid v1.3.0 h1:t6JiXgmwXMjEs8VusXIJk2BXHsn+wx8BZdTaoZ5fu7I=
+github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/sirupsen/logrus v1.8.1 h1:dJKuHgqk1NNQlqoA6BTlM1Wf9DOH3NBjQyu0h9+AZZE=

logger.go

@@ -16,7 +16,7 @@ func setupLogger() {
 	log = logrus.New()
 
 	// Handle logfile
-	if (*logFile == "") {
+	if *logFile == "" {
 		log.SetOutput(os.Stderr)
 	} else {
 		writer, err := os.OpenFile(*logFile, os.O_CREATE|os.O_RDWR|os.O_APPEND, 0600)

main.go

@@ -1,11 +1,13 @@
 package main
 
 import (
+	"bytes"
 	"crypto/tls"
 	"fmt"
 	"net"
 	"net/textproto"
 	"os"
+	"os/exec"
 	"os/signal"
 	"strings"
 	"syscall"
@@ -81,12 +83,12 @@ func addrAllowed(addr string, allowedAddrs []string) bool {
 
 func senderChecker(peer smtpd.Peer, addr string) error {
 	// check sender address from auth file if user is authenticated
-	if *allowedUsers != "" && peer.Username != "" {
+	if localAuthRequired() && peer.Username != "" {
 		user, err := AuthFetch(peer.Username)
 		if err != nil {
 			// Shouldn't happen: authChecker already validated username+password
 			log.WithFields(logrus.Fields{
-				"peer": peer.Addr,
+				"peer":     peer.Addr,
 				"username": peer.Username,
 			}).WithError(err).Warn("could not fetch auth user")
 			return smtpd.Error{Code: 451, Message: "Bad sender address"}
@@ -94,8 +96,8 @@ func senderChecker(peer smtpd.Peer, addr string) error {
 
 		if !addrAllowed(addr, user.allowedAddresses) {
 			log.WithFields(logrus.Fields{
-				"peer": peer.Addr,
-				"username": peer.Username,
+				"peer":           peer.Addr,
+				"username":       peer.Username,
 				"sender_address": addr,
 			}).Warn("sender address not allowed for authenticated user")
 			return smtpd.Error{Code: 451, Message: "Bad sender address"}
@@ -114,7 +116,7 @@ func senderChecker(peer smtpd.Peer, addr string) error {
 
 	log.WithFields(logrus.Fields{
 		"sender_address": addr,
-		"peer": peer.Addr,
+		"peer":           peer.Addr,
 	}).Warn("sender address not allowed by allowed_sender pattern")
 	return smtpd.Error{Code: 451, Message: "Bad sender address"}
 }
@@ -131,7 +133,7 @@ func recipientChecker(peer smtpd.Peer, addr string) error {
 	}
 
 	log.WithFields(logrus.Fields{
-		"peer": peer.Addr,
+		"peer":              peer.Addr,
 		"recipient_address": addr,
 	}).Warn("recipient address not allowed by allowed_recipients pattern")
 	return smtpd.Error{Code: 451, Message: "Bad recipient address"}
@@ -141,7 +143,7 @@ func authChecker(peer smtpd.Peer, username string, password string) error {
 	err := AuthCheckPassword(username, password)
 	if err != nil {
 		log.WithFields(logrus.Fields{
-			"peer": peer.Addr,
+			"peer":     peer.Addr,
 			"username": username,
 		}).WithError(err).Warn("auth error")
 		return smtpd.Error{Code: 535, Message: "Authentication credentials invalid"}
@@ -157,21 +159,45 @@ func mailHandler(peer smtpd.Peer, env smtpd.Envelope) error {
 
 	logger := log.WithFields(logrus.Fields{
 		"from": env.Sender,
-		"to": env.Recipients,
+		"to":   env.Recipients,
 		"peer": peerIP,
 		"host": *remoteHost,
 		"uuid": generateUUID(),
 	})
 
-	if (*remoteHost == "") {
-		logger.Warning("remote_host not set; discarding mail")
+	if *remoteHost == "" && *command == "" {
+		logger.Warning("no remote_host or command set; discarding mail")
+		return nil
+	}
+
+	env.AddReceivedLine(peer)
+
+	if *command != "" {
+		cmdLogger := logger.WithField("command", *command)
+
+		var stdout bytes.Buffer
+		var stderr bytes.Buffer
+
+		cmd := exec.Command(*command)
+		cmd.Stdin = bytes.NewReader(env.Data)
+		cmd.Stdout = &stdout
+		cmd.Stderr = &stderr
+
+		err := cmd.Run()
+		if err != nil {
+			cmdLogger.WithError(err).Error(stderr.String())
+			return nil
+		}
+
+		cmdLogger.Info("pipe command successful: " + stdout.String())
+	}
+
+	if *remoteHost == "" {
 		return nil
 	}
 
 	logger.Info("delivering mail from peer using smarthost")
 
-	env.AddReceivedLine(peer)
-
 	var sender string
 
 	if *remoteSender == "" {
@@ -197,7 +223,7 @@ func mailHandler(peer smtpd.Peer, env smtpd.Envelope) error {
 
 			logger.WithFields(logrus.Fields{
 				"err_code": err.Code,
-				"err_msg": err.Msg,
+				"err_msg":  err.Msg,
 			}).Error("delivery failed")
 		default:
 			smtpError = smtpd.Error{Code: 554, Message: "Forwarding failed"}
@@ -246,7 +272,7 @@ func getTLSConfig() *tls.Config {
 	if *localCert == "" || *localKey == "" {
 		log.WithFields(logrus.Fields{
 			"cert_file": *localCert,
-			"key_file": *localKey,
+			"key_file":  *localKey,
 		}).Fatal("TLS certificate/key file not defined in config")
 	}
 
@@ -276,7 +302,7 @@ func main() {
 		Debug("starting smtprelay")
 
 	// Load allowed users file
-	if *allowedUsers != "" {
+	if localAuthRequired() {
 		err := AuthLoadFile(*allowedUsers)
 		if err != nil {
 			log.WithField("file", *allowedUsers).
@@ -288,7 +314,9 @@ func main() {
 	var servers []*smtpd.Server
 
 	// Create a server for each desired listen address
-	for _, listenAddr := range strings.Split(*listen, " ") {
+	for _, listen := range listenAddrs {
+		logger := log.WithField("address", listen.address)
+
 		server := &smtpd.Server{
 			Hostname:          *hostName,
 			WelcomeMessage:    *welcomeMsg,
@@ -298,44 +326,38 @@ func main() {
 			Handler:           mailHandler,
 		}
 
-		if *allowedUsers != "" {
+		if localAuthRequired() {
 			server.Authenticator = authChecker
 		}
 
 		var lsnr net.Listener
 		var err error
 
-		if strings.Index(listenAddr, "://") == -1 {
-			log.WithField("address", listenAddr).
-				Info("listening on address")
-
-			lsnr, err = net.Listen("tcp", listenAddr)
-		} else if strings.HasPrefix(listenAddr, "starttls://") {
-			listenAddr = strings.TrimPrefix(listenAddr, "starttls://")
+		switch listen.protocol {
+		case "":
+			logger.Info("listening on address")
+			lsnr, err = net.Listen("tcp", listen.address)
 
+		case "starttls":
 			server.TLSConfig = getTLSConfig()
 			server.ForceTLS = *localForceTLS
 
-			log.WithField("address", listenAddr).
-				Info("listening on address (STARTTLS)")
-			lsnr, err = net.Listen("tcp", listenAddr)
-		} else if strings.HasPrefix(listenAddr, "tls://") {
-			listenAddr = strings.TrimPrefix(listenAddr, "tls://")
+			logger.Info("listening on address (STARTTLS)")
+			lsnr, err = net.Listen("tcp", listen.address)
 
+		case "tls":
 			server.TLSConfig = getTLSConfig()
 
-			log.WithField("address", listenAddr).
-				Info("listening on address (TLS)")
-			lsnr, err = tls.Listen("tcp", listenAddr, server.TLSConfig)
-		} else {
-			log.WithField("address", listenAddr).
+			logger.Info("listening on address (TLS)")
+			lsnr, err = tls.Listen("tcp", listen.address, server.TLSConfig)
+
+		default:
+			logger.WithField("protocol", listen.protocol).
 				Fatal("unknown protocol in listen address")
 		}
 
 		if err != nil {
-			log.WithFields(logrus.Fields{
-				"address": listenAddr,
-			}).WithError(err).Fatal("error starting listener")
+			logger.WithError(err).Fatal("error starting listener")
 		}
 		servers = append(servers, server)
 

smtprelay.ini

@@ -78,3 +78,6 @@
 
 ; Sender e-mail address on outgoing SMTP server
 ;remote_sender = 
+
+; Pipe messages to external command
+;command = /usr/local/bin/script