Feature: Add option to disable SMTP reverse DNS (rDNS) lookup (#230)

axllent · Jan 20, 2024 · 6725db4 · 6725db4
1 parent 3f98ac5
commit 6725db4
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Showing 4 changed files with 21 additions and 11 deletions.
diff --git a/cmd/root.go b/cmd/root.go
@@ -105,6 +105,7 @@ func init() {
 	rootCmd.Flags().BoolVar(&config.SMTPStrictRFCHeaders, "smtp-strict-rfc-headers", config.SMTPStrictRFCHeaders, "Return SMTP error if message headers contain <CR><CR><LF>")
 	rootCmd.Flags().IntVar(&config.SMTPMaxRecipients, "smtp-max-recipients", config.SMTPMaxRecipients, "Maximum SMTP recipients allowed")
 	rootCmd.Flags().StringVar(&config.SMTPAllowedRecipients, "smtp-allowed-recipients", config.SMTPAllowedRecipients, "Only allow SMTP recipients matching a regular expression (default allow all)")
+	rootCmd.Flags().BoolVar(&smtpd.DisableReverseDNS, "smtp-disable-rdns", smtpd.DisableReverseDNS, "Disable SMTP reverse DNS lookups")
 
 	rootCmd.Flags().StringVar(&config.SMTPRelayConfigFile, "smtp-relay-config", config.SMTPRelayConfigFile, "SMTP configuration file to allow releasing messages")
 	rootCmd.Flags().BoolVar(&config.SMTPRelayAllIncoming, "smtp-relay-all", config.SMTPRelayAllIncoming, "Relay all incoming messages via external SMTP server (caution!)")
@@ -175,6 +176,9 @@ func initConfigFromEnv() {
 	if len(os.Getenv("MP_SMTP_ALLOWED_RECIPIENTS")) > 0 {
 		config.SMTPAllowedRecipients = os.Getenv("MP_SMTP_ALLOWED_RECIPIENTS")
 	}
+	if getEnabledFromEnv("MP_SMTP_DISABLE_RDNS") {
+		smtpd.DisableReverseDNS = true
+	}
 
 	// Relay server config
 	config.SMTPRelayConfigFile = os.Getenv("MP_SMTP_RELAY_CONFIG")

diff --git a/go.mod b/go.mod
@@ -14,7 +14,7 @@ require (
 	github.com/jhillyerd/enmime v1.1.0
 	github.com/klauspost/compress v1.17.4
 	github.com/leporo/sqlf v1.4.0
-	github.com/mhale/smtpd v0.8.1
+	github.com/mhale/smtpd v0.8.2
 	github.com/reiver/go-telnet v0.0.0-20180421082511-9ff0b2ab096e
 	github.com/sirupsen/logrus v1.9.3
 	github.com/spf13/cobra v1.8.0

diff --git a/go.sum b/go.sum
@@ -90,8 +90,8 @@ github.com/mattn/go-runewidth v0.0.15 h1:UNAjwbU9l54TA3KzvqLGxwWjHmMgBUVhBiTjelZ
 github.com/mattn/go-runewidth v0.0.15/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
 github.com/mattn/go-sqlite3 v1.14.16 h1:yOQRA0RpS5PFz/oikGwBEqvAWhWg5ufRz4ETLjwpU1Y=
 github.com/mattn/go-sqlite3 v1.14.16/go.mod h1:2eHXhiwb8IkHr+BDWZGa96P6+rkvnG63S2DGjv9HUNg=
-github.com/mhale/smtpd v0.8.1 h1:O02u8O3eYAGxZCGf4E98WjyB+rA3DVFZtchEialjX4s=
-github.com/mhale/smtpd v0.8.1/go.mod h1:MQl+y2hwIEQCXtNhe5+55n0GZOjSmeqORDIXbqUL3x4=
+github.com/mhale/smtpd v0.8.2 h1:rHKOMHeFoDvcq8Na9ErCbNcjlWTSyGtznOmJpWsOzuc=
+github.com/mhale/smtpd v0.8.2/go.mod h1:MQl+y2hwIEQCXtNhe5+55n0GZOjSmeqORDIXbqUL3x4=
 github.com/olekukonko/tablewriter v0.0.5 h1:P2Ga83D34wi1o9J6Wh1mRuqd4mF/x/lgBS7N7AbDhec=
 github.com/olekukonko/tablewriter v0.0.5/go.mod h1:hPp6KlRPjbx+hW8ykQs1w3UBbZlj6HuIJcUGPhkA7kY=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=

diff --git a/server/smtpd/smtpd.go b/server/smtpd/smtpd.go
@@ -18,6 +18,11 @@ import (
 	"github.com/mhale/smtpd"
 )
 
+var (
+	// DisableReverseDNS allows rDNS to be disabled
+	DisableReverseDNS bool
+)
+
 func mailHandler(origin net.Addr, from string, to []string, data []byte) error {
 	if !config.SMTPStrictRFCHeaders {
 		// replace all <CR><CR><LF> (\r\r\n) with <CR><LF> (\r\n)
@@ -191,14 +196,15 @@ func Listen() error {
 
 func listenAndServe(addr string, handler smtpd.Handler, authHandler smtpd.AuthHandler) error {
 	srv := &smtpd.Server{
-		Addr:          addr,
-		Handler:       handler,
-		HandlerRcpt:   handlerRcpt,
-		Appname:       "Mailpit",
-		Hostname:      "",
-		AuthHandler:   nil,
-		AuthRequired:  false,
-		MaxRecipients: config.SMTPMaxRecipients,
+		Addr:              addr,
+		Handler:           handler,
+		HandlerRcpt:       handlerRcpt,
+		Appname:           "Mailpit",
+		Hostname:          "",
+		AuthHandler:       nil,
+		AuthRequired:      false,
+		MaxRecipients:     config.SMTPMaxRecipients,
+		DisableReverseDNS: DisableReverseDNS,
 	}
 
 	if config.SMTPAuthAllowInsecure {