feat: dynamic reread of aliases

aliases.go

@@ -5,10 +5,15 @@ import (
 	"fmt"
 	"os"
 	"strings"
+	"sync"
 )
 
 type AliasMap map[string]string
 
+var (
+	aliasesMutex sync.RWMutex
+)
+
 func AliasLoadFile(file string) (AliasMap, error) {
 	aliasMap := make(AliasMap)
 	count := 0
@@ -50,3 +55,18 @@ func AliasLoadFile(file string) (AliasMap, error) {
 	}
 	return aliasMap, nil
 }
+
+func LoadAliases(filename string) error {
+	newAliases, err := AliasLoadFile(filename)
+	if err != nil {
+		return err
+	}
+
+	aliasesMutex.Lock()
+	defer aliasesMutex.Unlock()
+
+	// Update the aliases map
+	aliasesList = newAliases
+
+	return nil
+}

config.go

@@ -42,7 +42,7 @@ var (
 	allowedSenderStr = flagset.String("allowed_sender", "", "Regular expression for valid FROM EMail addresses")
 	allowedRecipStr  = flagset.String("allowed_recipients", "", "Regular expression for valid TO EMail addresses")
 	allowedUsers     = flagset.String("allowed_users", "", "Path to file with valid users/passwords")
-	aliasesFile      = flagset.String("aliases_file", "", "Path to aliases file")
+	aliasFile        = flagset.String("aliases_file", "", "Path to aliases file")
 	command          = flagset.String("command", "", "Path to pipe command")
 	remotesStr       = flagset.String("remotes", "", "Outgoing SMTP servers")
 	strictSender     = flagset.Bool("strict_sender", false, "Use only SMTP servers with Sender matches to From")
@@ -68,12 +68,12 @@ func localAuthRequired() bool {
 }
 
 func setupAliases() {
-	if *aliasesFile != "" {
+	if *aliasFile != "" {
 		aliases := make(AliasMap)
-		aliases, err := AliasLoadFile(*aliasesFile)
+		aliases, err := AliasLoadFile(*aliasFile)
 		if err != nil {
 			log.Fatal().
-				Str("file", *aliasesFile).
+				Str("file", *aliasFile).
 				Err(err).
 				Msg("cannot load aliases file")
 		}

go.mod

@@ -3,6 +3,7 @@ module github.com/decke/smtprelay
 require (
 	github.com/DeRuina/timberjack v1.3.9
 	github.com/chrj/smtpd v0.3.1
+	github.com/fsnotify/fsnotify v1.9.0
 	github.com/google/uuid v1.6.0
 	github.com/peterbourgon/ff/v3 v3.4.0
 	github.com/rs/zerolog v1.34.0

go.sum

@@ -7,6 +7,8 @@ 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/fortytw2/leaktest v1.3.0 h1:u8491cBMTQ8ft8aeV+adlcytMZylmA5nnwwkRZjI8vw=
 github.com/fortytw2/leaktest v1.3.0/go.mod h1:jDsjWgpAGjm2CA7WthBh/CdZYEPF31XHquHwclZch5g=
+github.com/fsnotify/fsnotify v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
+github.com/fsnotify/fsnotify v1.9.0/go.mod h1:8jBTzvmWwFyi3Pb8djgCCO5IBqzKJ/Jwo8TRcHyHii0=
 github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=

main.go

@@ -13,6 +13,7 @@ import (
 	"syscall"
 
 	"github.com/chrj/smtpd"
+	"github.com/fsnotify/fsnotify"
 	"github.com/google/uuid"
 )
 
@@ -160,6 +161,7 @@ func mailHandler(peer smtpd.Peer, env smtpd.Envelope) error {
 	}
 
 	// Check for aliases
+	aliasesMutex.RLock()
 	for i, recipient := range env.Recipients {
 		if alias, exists := aliasesList[recipient]; exists {
 			env.Recipients[i] = alias
@@ -169,6 +171,7 @@ func mailHandler(peer smtpd.Peer, env smtpd.Envelope) error {
 				Msg("Recipient address aliased")
 		}
 	}
+	aliasesMutex.RUnlock()
 
 	logger := log.With().
 		Str("from", env.Sender).
@@ -297,6 +300,71 @@ func getTLSConfig() *tls.Config {
 	}
 }
 
+func watchAliasFile() {
+	if *aliasFile == "" {
+		return
+	}
+
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		log.Error().
+			Err(err).
+			Msg("failed to create file watcher for alias file")
+		return
+	}
+
+	go func() {
+		defer watcher.Close()
+
+		for {
+			select {
+			case event, ok := <-watcher.Events:
+				if !ok {
+					return
+				}
+
+				if event.Has(fsnotify.Write) || event.Has(fsnotify.Create) {
+					log.Info().
+						Str("file", event.Name).
+						Msg("alias file changed, reloading")
+
+					err := LoadAliases(*aliasFile)
+					if err != nil {
+						log.Error().
+							Str("file", *aliasFile).
+							Err(err).
+							Msg("failed to reload alias file")
+					} else {
+						log.Info().
+							Int("count", len(aliasesList)).
+							Msg("alias file reloaded successfully")
+					}
+				}
+
+			case err, ok := <-watcher.Errors:
+				if !ok {
+					return
+				}
+				log.Error().
+					Err(err).
+					Msg("file watcher error")
+			}
+		}
+	}()
+
+	err = watcher.Add(*aliasFile)
+	if err != nil {
+		log.Error().
+			Str("file", *aliasFile).
+			Err(err).
+			Msg("failed to watch alias file")
+	} else {
+		log.Info().
+			Str("file", *aliasFile).
+			Msg("watching alias file for changes")
+	}
+}
+
 func main() {
 	ConfigLoad()
 
@@ -315,6 +383,9 @@ func main() {
 		}
 	}
 
+	// Start watching alias file for changes
+	watchAliasFile()
+
 	var servers []*smtpd.Server
 
 	// Create a server for each desired listen address