Bump version to 1.3.0

It represents the e-mail address used while sending message to the outgoing SMTP server.

.drone.yml

@@ -0,0 +1,8 @@
+kind: pipeline
+name: default
+
+steps:
+- name: build
+  image: golang
+  commands:
+  - go build

README.md

@@ -1,4 +1,4 @@
-# smtp-proxy
+# smtprelay
 
 Simple Golang based SMTP relay/proxy server that accepts mail via SMTP
 and forwards it directly to another SMTP server.
@@ -25,5 +25,5 @@ produces mail.
 * Authentication support with file (LOGIN, PLAIN)
 * Enforce encryption for authentication
 * Forwards all mail to a smarthost (GMail, MailGun or any other SMTP server)
-* Small codebase (smtp-proxy ~250 LoC, chrj/smtpd ~1200 LoC)
+* Small codebase
 * IPv6 support

auth.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"os"
+	"strings"
+
+	"golang.org/x/crypto/bcrypt"
+)
+
+var (
+	filename string
+)
+
+func AuthLoadFile(file string) error {
+	f, err := os.Open(file)
+	if err != nil {
+		return err
+	}
+	f.Close()
+
+	filename = file
+	return nil
+}
+
+func AuthReady() bool {
+	return (filename != "")
+}
+
+func AuthFetch(username string) (string, string, error) {
+	if !AuthReady() {
+		return "", "", errors.New("Authentication file not specified. Call LoadFile() first")
+	}
+
+	file, err := os.Open(filename)
+	if err != nil {
+		return "", "", err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		parts := strings.Fields(scanner.Text())
+
+		if len(parts) != 3 {
+			continue
+		}
+
+		if strings.ToLower(username) == strings.ToLower(parts[0]) {
+			return parts[1], parts[2], nil
+		}
+	}
+
+	return "", "", errors.New("User not found")
+}
+
+func AuthCheckPassword(username string, secret string) error {
+	hash, _, err := AuthFetch(username)
+	if err != nil {
+		return err
+	}
+	if bcrypt.CompareHashAndPassword([]byte(hash), []byte(secret)) == nil {
+		return nil
+	}
+	return errors.New("Password invalid")
+}

config.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"flag"
+
+	"github.com/vharitonsky/iniflags"
+)
+
+const (
+	VERSION = "1.3.0"
+)
+
+var (
+	logFile           = flag.String("logfile", "/var/log/smtprelay.log", "Path to logfile")
+	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")
+	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)")
+	allowedNets       = flag.String("allowed_nets", "127.0.0.1/8 ::1/128", "Networks allowed to send mails")
+	allowedSender     = flag.String("allowed_sender", "", "Regular expression for valid FROM EMail adresses")
+	allowedRecipients = flag.String("allowed_recipients", "", "Regular expression for valid TO EMail adresses")
+	allowedUsers      = flag.String("allowed_users", "", "Path to file with valid users/passwords")
+	remoteHost        = flag.String("remote_host", "smtp.gmail.com:587", "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")
+	remoteSender      = flag.String("remote_sender", "", "Sender e-mail address on outgoing SMTP server")
+	versionInfo       = flag.Bool("version", false, "Show version information")
+)
+
+func ConfigLoad() {
+	iniflags.Parse()
+}

go.mod

@@ -1,6 +1,9 @@
-module code.bluelife.at/decke/smtp-proxy
+module code.bluelife.at/decke/smtprelay
 
 require (
 	github.com/chrj/smtpd v0.1.2
 	github.com/vharitonsky/iniflags v0.0.0-20180513140207-a33cd0b5f3de
+	golang.org/x/crypto v0.0.0-20190829043050-9756ffdc2472
 )
+
+go 1.13

go.sum

@@ -3,3 +3,10 @@ github.com/chrj/smtpd v0.1.2/go.mod h1:jt4ydELuZmqhn9hn3YpEPV1dY00aOB+Q1nWXnBDFK
 github.com/eaigner/dkim v0.0.0-20150301120808-6fe4a7ee9cfb/go.mod h1:FSCIHbrqk7D01Mj8y/jW+NS1uoCerr+ad+IckTHTFf4=
 github.com/vharitonsky/iniflags v0.0.0-20180513140207-a33cd0b5f3de h1:fkw+7JkxF3U1GzQoX9h69Wvtvxajo5Rbzy6+YMMzPIg=
 github.com/vharitonsky/iniflags v0.0.0-20180513140207-a33cd0b5f3de/go.mod h1:irMhzlTz8+fVFj6CH2AN2i+WI5S6wWFtK3MBCIxIpyI=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20190829043050-9756ffdc2472 h1:Gv7RPwsi3eZ2Fgewe3CBsuOebPwO27PoXzRpJPsvSSM=
+golang.org/x/crypto v0.0.0-20190829043050-9756ffdc2472/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

main.go

@@ -1,9 +1,7 @@
 package main
 
 import (
-	"bufio"
 	"crypto/tls"
-	"flag"
 	"fmt"
 	"io"
 	"log"
@@ -15,29 +13,6 @@ import (
 	"time"
 
 	"github.com/chrj/smtpd"
-	"github.com/vharitonsky/iniflags"
-)
-
-const (
-	VERSION = "1.1.0"
-)
-
-var (
-	logFile    = flag.String("logfile", "/var/log/smtpd-proxy.log", "Path to logfile")
-	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")
-	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)")
-	allowedNets = flag.String("allowed_nets", "127.0.0.1/8 ::1/128", "Networks allowed to send mails")
-	allowedSender = flag.String("allowed_sender", "", "Regular expression for valid FROM EMail adresses")
-	allowedRecipients = flag.String("allowed_recipients", "", "Regular expression for valid TO EMail adresses")
-	allowedUsers = flag.String("allowed_users", "", "Path to file with valid users/passwords")
-	remoteHost = flag.String("remote_host", "smtp.gmail.com:587", "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")
-	versionInfo= flag.Bool("version", false, "Show version information")
 )
 
 func connectionChecker(peer smtpd.Peer) error {
@@ -50,7 +25,7 @@ func connectionChecker(peer smtpd.Peer) error {
 
 	nets := strings.Split(*allowedNets, " ")
 
-	for i := range(nets) {
+	for i := range nets {
 		_, allowedNet, _ := net.ParseCIDR(nets[i])
 
 		if allowedNet.Contains(peerIP) {
@@ -62,6 +37,18 @@ func connectionChecker(peer smtpd.Peer) error {
 }
 
 func senderChecker(peer smtpd.Peer, addr string) error {
+	// check sender address from auth file if user is authenticated
+	if *allowedUsers != "" && peer.Username != "" {
+		_, email, err := AuthFetch(peer.Username)
+		if err != nil {
+			return smtpd.Error{Code: 451, Message: "Bad sender address"}
+		}
+
+		if strings.ToLower(addr) != strings.ToLower(email) {
+			return smtpd.Error{Code: 451, Message: "Bad sender address"}
+		}
+	}
+
 	if *allowedSender == "" {
 		return nil
 	}
@@ -98,27 +85,12 @@ func recipientChecker(peer smtpd.Peer, addr string) error {
 }
 
 func authChecker(peer smtpd.Peer, username string, password string) error {
-	file, err := os.Open(*allowedUsers)
+	err := AuthCheckPassword(username, password)
 	if err != nil {
-		log.Printf("User file not found %v", err)
+		log.Printf("Auth error: %v\n", err)
 		return smtpd.Error{Code: 535, Message: "Authentication credentials invalid"}
 	}
-	defer file.Close()
-
-	scanner := bufio.NewScanner(file)
-	for scanner.Scan() {
-		parts := strings.Fields(scanner.Text())
-
-		if len(parts) != 2 {
-			continue
-		}
-
-		if username == parts[0] && password == parts[1] {
-			return nil
-		}
-	}
-
-	return smtpd.Error{Code: 535, Message: "Authentication credentials invalid"}
+	return nil
 }
 
 func mailHandler(peer smtpd.Peer, env smtpd.Envelope) error {
@@ -145,15 +117,23 @@ func mailHandler(peer smtpd.Peer, env smtpd.Envelope) error {
 
 	log.Printf("delivering using smarthost %s\n", *remoteHost)
 
+	var sender string
+
+	if *remoteSender == "" {
+		sender = env.Sender
+	} else {
+		sender = *remoteSender
+	}
+
 	err := SendMail(
 		*remoteHost,
 		auth,
-		env.Sender,
+		sender,
 		env.Recipients,
 		env.Data,
 	)
 	if err != nil {
-		log.Printf("delivery failed: %v\n", err);
+		log.Printf("delivery failed: %v\n", err)
 		return smtpd.Error{Code: 554, Message: "Forwarding failed"}
 	}
 
@@ -164,15 +144,15 @@ func mailHandler(peer smtpd.Peer, env smtpd.Envelope) error {
 
 func main() {
 
-	iniflags.Parse()
+	ConfigLoad()
 
 	if *versionInfo {
-		fmt.Printf("smtpd-proxy/%s\n", VERSION)
+		fmt.Printf("smtprelay/%s\n", VERSION)
 		os.Exit(0)
 	}
 
 	if *logFile != "" {
-		f, err := os.OpenFile(*logFile, os.O_WRONLY | os.O_CREATE | os.O_APPEND, 0600)
+		f, err := os.OpenFile(*logFile, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0600)
 		if err != nil {
 			log.Fatalf("Error opening logfile: %v", err)
 		}
@@ -183,7 +163,7 @@ func main() {
 
 	listeners := strings.Split(*listen, " ")
 
-	for i := range(listeners) {
+	for i := range listeners {
 		listener := listeners[i]
 
 		server := &smtpd.Server{
@@ -196,6 +176,11 @@ func main() {
 		}
 
 		if *allowedUsers != "" {
+			err := AuthLoadFile(*allowedUsers)
+			if err != nil {
+				log.Fatalf("Authentication file: %s\n", err)
+			}
+
 			server.Authenticator = authChecker
 		}
 
@@ -214,13 +199,40 @@ func main() {
 				log.Fatal(err)
 			}
 
-			server.TLSConfig = &tls.Config {
-				Certificates: [] tls.Certificate{cert},
+			server.TLSConfig = &tls.Config{
+				PreferServerCipherSuites: true,
+				MinVersion:               tls.VersionTLS11,
+
+				// Ciphersuites as defined in stock Go but without 3DES
+				// https://golang.org/src/crypto/tls/cipher_suites.go
+				CipherSuites: []uint16{
+					tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
+					tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
+					tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
+					tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
+					tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
+					tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
+					tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
+					tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
+					tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
+					tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
+					tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
+					tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
+					tls.TLS_RSA_WITH_AES_128_GCM_SHA256, // does not provide PFS
+					tls.TLS_RSA_WITH_AES_256_GCM_SHA384, // does not provide PFS
+					tls.TLS_RSA_WITH_AES_128_CBC_SHA256,
+					tls.TLS_RSA_WITH_AES_128_CBC_SHA,
+					tls.TLS_RSA_WITH_AES_256_CBC_SHA,
+				},
+				Certificates: []tls.Certificate{cert},
 			}
 			server.ForceTLS = *localForceTLS
 
 			log.Printf("Listen on %s (STARTSSL) ...\n", listener)
 			lsnr, err := net.Listen("tcp", listener)
+			if err != nil {
+				log.Fatal(err)
+			}
 			defer lsnr.Close()
 
 			go server.Serve(lsnr)
@@ -237,12 +249,39 @@ func main() {
 				log.Fatal(err)
 			}
 
-			server.TLSConfig = &tls.Config {
-				Certificates: [] tls.Certificate{cert},
+			server.TLSConfig = &tls.Config{
+				PreferServerCipherSuites: true,
+				MinVersion:               tls.VersionTLS11,
+
+				// Ciphersuites as defined in stock Go but without 3DES
+				// https://golang.org/src/crypto/tls/cipher_suites.go
+				CipherSuites: []uint16{
+					tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
+					tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
+					tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
+					tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
+					tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
+					tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
+					tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
+					tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
+					tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
+					tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
+					tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
+					tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
+					tls.TLS_RSA_WITH_AES_128_GCM_SHA256, // does not provide PFS
+					tls.TLS_RSA_WITH_AES_256_GCM_SHA384, // does not provide PFS
+					tls.TLS_RSA_WITH_AES_128_CBC_SHA256,
+					tls.TLS_RSA_WITH_AES_128_CBC_SHA,
+					tls.TLS_RSA_WITH_AES_256_CBC_SHA,
+				},
+				Certificates: []tls.Certificate{cert},
 			}
 
 			log.Printf("Listen on %s (TLS) ...\n", listener)
 			lsnr, err := tls.Listen("tcp", listener, server.TLSConfig)
+			if err != nil {
+				log.Fatal(err)
+			}
 			defer lsnr.Close()
 
 			go server.Serve(lsnr)

smtp.go

@@ -67,7 +67,7 @@ func NewClient(conn net.Conn, host string) (*Client, error) {
 		text.Close()
 		return nil, err
 	}
-	c := &Client{Text: text, conn: conn, serverName: host, localName: "localhost"}
+	c := &Client{Text: text, conn: conn, serverName: host, localName: *hostName}
 	_, c.tls = conn.(*tls.Conn)
 	return c, nil
 }

smtprelay.ini

@@ -1,7 +1,7 @@
-; smtp-proxy configuration
+; smtprelay configuration
 
 ; Logfile
-;logfile = /var/log/smtpd-proxy.log
+;logfile = /var/log/smtprelay.log
 
 ; Hostname for this SMTP server
 ;hostname = "localhost.localdomain"
@@ -37,7 +37,7 @@
 
 ; File which contains username and password used for
 ; authentication before they can send mail.
-; File format: username password
+; File format: username bcrypt-hash email
 ;allowed_users =
 
 ; Relay all mails to this SMTP server
@@ -54,3 +54,6 @@
 ; Authentication credentials on outgoing SMTP server
 ;remote_user =
 ;remote_pass =
+
+; Sender e-mail address on outgoing SMTP server
+;remote_sender =