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Feature: Optionally propagate SMTP errors (#588)

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* forward smtp errors

* lint and formatting

* forward smtp errors in forward-impl
This commit is contained in:
Dennis
2025-11-26 04:17:44 +01:00
committed by GitHub
parent b987006897
commit 0f0a5d942f
6 changed files with 115 additions and 44 deletions
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5
cmd/root.go
View File

@@ -6,6 +6,8 @@ import (
"strconv"
"strings"
"github.com/spf13/cobra"
"github.com/axllent/mailpit/config"
"github.com/axllent/mailpit/internal/auth"
"github.com/axllent/mailpit/internal/logger"
@@ -16,7 +18,6 @@ import (
"github.com/axllent/mailpit/internal/tools"
"github.com/axllent/mailpit/server"
"github.com/axllent/mailpit/server/webhook"
"github.com/spf13/cobra"
)
// rootCmd represents the base command when called without any subcommands
@@ -332,6 +333,7 @@ func initConfigFromEnv() {
config.SMTPRelayConfig.AllowedRecipients = os.Getenv("MP_SMTP_RELAY_ALLOWED_RECIPIENTS")
config.SMTPRelayConfig.BlockedRecipients = os.Getenv("MP_SMTP_RELAY_BLOCKED_RECIPIENTS")
config.SMTPRelayConfig.PreserveMessageIDs = getEnabledFromEnv("MP_SMTP_RELAY_PRESERVE_MESSAGE_IDS")
config.SMTPRelayConfig.ForwardSMTPErrors = getEnabledFromEnv("MP_SMTP_RELAY_FWD_SMTP_ERRORS")
// SMTP forwarding
config.SMTPForwardConfigFile = os.Getenv("MP_SMTP_FORWARD_CONFIG")
@@ -350,6 +352,7 @@ func initConfigFromEnv() {
config.SMTPForwardConfig.ReturnPath = os.Getenv("MP_SMTP_FORWARD_RETURN_PATH")
config.SMTPForwardConfig.OverrideFrom = os.Getenv("MP_SMTP_FORWARD_OVERRIDE_FROM")
config.SMTPForwardConfig.To = os.Getenv("MP_SMTP_FORWARD_TO")
config.SMTPForwardConfig.ForwardSMTPErrors = getEnabledFromEnv("MP_SMTP_FORWARD_FWD_SMTP_ERRORS")
// Chaos
chaos.Enabled = getEnabledFromEnv("MP_ENABLE_CHAOS")

36
config/config.go
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@@ -12,6 +12,7 @@ import (
"strings"
"github.com/axllent/ghru/v2"
"github.com/axllent/mailpit/internal/auth"
"github.com/axllent/mailpit/internal/logger"
"github.com/axllent/mailpit/internal/smtpd/chaos"
@@ -252,6 +253,7 @@ type SMTPRelayConfigStruct struct {
BlockedRecipients string `yaml:"blocked-recipients"` // regex, if set prevents relating to these addresses
BlockedRecipientsRegexp *regexp.Regexp // compiled regexp using BlockedRecipients
PreserveMessageIDs bool `yaml:"preserve-message-ids"` // preserve the original Message-ID when relaying
ForwardSMTPErrors bool `yaml:"forward-smtp-errors"` // whether to log smtp-errors or forward them to upstream-client
// DEPRECATED 2024/03/12
RecipientAllowlist string `yaml:"recipient-allowlist"`
@@ -259,18 +261,19 @@ type SMTPRelayConfigStruct struct {
// SMTPForwardConfigStruct struct for parsing yaml & storing variables
type SMTPForwardConfigStruct struct {
To string `yaml:"to"` // comma-separated list of email addresses
Host string `yaml:"host"` // SMTP host
Port int `yaml:"port"` // SMTP port
STARTTLS bool `yaml:"starttls"` // whether to use STARTTLS
TLS bool `yaml:"tls"` // whether to use TLS
AllowInsecure bool `yaml:"allow-insecure"` // allow insecure authentication, ignore TLS validation
Auth string `yaml:"auth"` // none, plain, login, cram-md5
Username string `yaml:"username"` // plain & cram-md5
Password string `yaml:"password"` // plain
Secret string `yaml:"secret"` // cram-md5
ReturnPath string `yaml:"return-path"` // allow overriding the bounce address
OverrideFrom string `yaml:"override-from"` // allow overriding of the from address
To string `yaml:"to"` // comma-separated list of email addresses
Host string `yaml:"host"` // SMTP host
Port int `yaml:"port"` // SMTP port
STARTTLS bool `yaml:"starttls"` // whether to use STARTTLS
TLS bool `yaml:"tls"` // whether to use TLS
AllowInsecure bool `yaml:"allow-insecure"` // allow insecure authentication, ignore TLS validation
Auth string `yaml:"auth"` // none, plain, login, cram-md5
Username string `yaml:"username"` // plain & cram-md5
Password string `yaml:"password"` // plain
Secret string `yaml:"secret"` // cram-md5
ReturnPath string `yaml:"return-path"` // allow overriding the bounce address
OverrideFrom string `yaml:"override-from"` // allow overriding of the from address
ForwardSMTPErrors bool `yaml:"forward-smtp-errors"` // whether to log smtp-errors or forward them to upstream-client
}
// VerifyConfig wil do some basic checking
@@ -283,7 +286,8 @@ func VerifyConfig() error {
// The default Content Security Policy is updates on every application page load to replace script-src 'self'
// with a random nonce ID to prevent XSS. This applies to the Mailpit app & API.
// See server.middleWareFunc()
ContentSecurityPolicy = fmt.Sprintf("default-src 'self'; script-src 'self'; style-src %s 'unsafe-inline'; frame-src 'self'; img-src * data: blob:; font-src %s data:; media-src 'self'; connect-src 'self' ws: wss:; object-src 'none'; base-uri 'self';",
ContentSecurityPolicy = fmt.Sprintf(
"default-src 'self'; script-src 'self'; style-src %s 'unsafe-inline'; frame-src 'self'; img-src * data: blob:; font-src %s data:; media-src 'self'; connect-src 'self' ws: wss:; object-src 'none'; base-uri 'self';",
cssFontRestriction, cssFontRestriction,
)
@@ -615,8 +619,10 @@ func VerifyConfig() error {
}
SMTPRelayMatchingRegexp = re
logger.Log().Infof("[relay] auto-relaying new messages to recipients matching \"%s\" via %s:%d",
SMTPRelayMatching, SMTPRelayConfig.Host, SMTPRelayConfig.Port)
logger.Log().Infof(
"[relay] auto-relaying new messages to recipients matching \"%s\" via %s:%d",
SMTPRelayMatching, SMTPRelayConfig.Host, SMTPRelayConfig.Port,
)
}
}

2
go.mod
View File

@@ -17,6 +17,7 @@ require (
github.com/leporo/sqlf v1.4.0
github.com/lithammer/shortuuid/v4 v4.2.0
github.com/mneis/go-telnet v0.0.0-20221017141824-6f643e477c62
github.com/pkg/errors v0.9.1
github.com/prometheus/client_golang v1.23.2
github.com/rqlite/gorqlite v0.0.0-20250609141355-ac86a4a1c9a8
github.com/sirupsen/logrus v1.9.3
@@ -58,7 +59,6 @@ require (
github.com/olekukonko/errors v1.1.0 // indirect
github.com/olekukonko/ll v0.1.2 // indirect
github.com/olekukonko/tablewriter v1.1.0 // indirect
github.com/pkg/errors v0.9.1 // indirect
github.com/prometheus/client_model v0.6.2 // indirect
github.com/prometheus/common v0.67.2 // indirect
github.com/prometheus/procfs v0.19.2 // indirect

21
internal/smtpd/forward.go
View File

@@ -7,23 +7,29 @@ import (
"os"
"strings"
"github.com/pkg/errors"
"github.com/axllent/mailpit/config"
"github.com/axllent/mailpit/internal/logger"
"github.com/axllent/mailpit/internal/tools"
)
// Wrapper to forward messages if configured
func autoForwardMessage(from string, data *[]byte) {
func autoForwardMessage(from string, data *[]byte) error {
if config.SMTPForwardConfig.Host == "" {
return
return nil
}
if err := forward(from, *data); err != nil {
logger.Log().Errorf("[forward] error: %s", err.Error())
} else {
logger.Log().Debugf("[forward] message from %s to %s via %s:%d",
from, config.SMTPForwardConfig.To, config.SMTPForwardConfig.Host, config.SMTPForwardConfig.Port)
return errors.WithMessage(err, "[forward] error: %s")
}
logger.Log().Debugf(
"[forward] message from %s to %s via %s:%d",
from, config.SMTPForwardConfig.To, config.SMTPForwardConfig.Host, config.SMTPForwardConfig.Port,
)
return nil
}
func createForwardingSMTPClient(config config.SMTPForwardConfigStruct, addr string) (*smtp.Client, error) {
@@ -108,6 +114,9 @@ func forward(from string, msg []byte) error {
for _, addr := range to {
if err = c.Rcpt(addr); err != nil {
logger.Log().Warnf("error response to RCPT command for %s: %s", addr, err.Error())
if config.SMTPForwardConfig.ForwardSMTPErrors {
return errors.WithMessagef(err, "error response to RCPT command for %s", addr)
}
}
}

52
internal/smtpd/main.go
View File

@@ -9,6 +9,9 @@ import (
"regexp"
"strings"
"github.com/lithammer/shortuuid/v4"
"github.com/pkg/errors"
"github.com/axllent/mailpit/config"
"github.com/axllent/mailpit/internal/auth"
"github.com/axllent/mailpit/internal/logger"
@@ -16,7 +19,6 @@ import (
"github.com/axllent/mailpit/internal/storage"
"github.com/axllent/mailpit/internal/tools"
"github.com/axllent/mailpit/server/websockets"
"github.com/lithammer/shortuuid/v4"
)
var (
@@ -73,10 +75,36 @@ func SaveToDatabase(origin net.Addr, from string, to []string, data []byte, smtp
}
// if enabled, this may conditionally relay the email through to the preconfigured smtp server
autoRelayMessage(from, to, &data)
if relayErr := autoRelayMessage(from, to, &data); relayErr != nil {
logger.Log().Errorf("%s", relayErr.Error())
if config.SMTPRelayConfig.ForwardSMTPErrors {
for {
unwrappedErr := errors.Unwrap(relayErr)
if unwrappedErr == nil {
break
}
relayErr = unwrappedErr
}
return "", relayErr
}
}
// if enabled, this will forward a copy to preconfigured addresses
autoForwardMessage(from, &data)
if forwardErr := autoForwardMessage(from, &data); forwardErr != nil {
logger.Log().Errorf("%s", forwardErr.Error())
if config.SMTPForwardConfig.ForwardSMTPErrors {
for {
unwrappedErr := errors.Unwrap(forwardErr)
if unwrappedErr == nil {
break
}
forwardErr = unwrappedErr
}
return "", forwardErr
}
}
// build array of all addresses in the header to compare to the []to array
emails, hasBccHeader := scanAddressesInHeader(msg.Header)
@@ -225,15 +253,27 @@ func listenAndServe(addr string, handler MsgIDHandler, authHandler AuthHandler)
}
if config.SMTPAuthAllowInsecure {
srv.AuthMechs = map[string]bool{"CRAM-MD5": false, "PLAIN": true, "LOGIN": true}
srv.AuthMechs = map[string]bool{
"CRAM-MD5": false,
"PLAIN": true,
"LOGIN": true,
}
}
if auth.SMTPCredentials != nil {
srv.AuthMechs = map[string]bool{"CRAM-MD5": false, "PLAIN": true, "LOGIN": true}
srv.AuthMechs = map[string]bool{
"CRAM-MD5": false,
"PLAIN": true,
"LOGIN": true,
}
srv.AuthHandler = authHandler
srv.AuthRequired = true
} else if config.SMTPAuthAcceptAny {
srv.AuthMechs = map[string]bool{"CRAM-MD5": false, "PLAIN": true, "LOGIN": true}
srv.AuthMechs = map[string]bool{
"CRAM-MD5": false,
"PLAIN": true,
"LOGIN": true,
}
srv.AuthHandler = authHandlerAny
}

43
internal/smtpd/relay.go
View File

@@ -2,19 +2,20 @@ package smtpd
import (
"crypto/tls"
"errors"
"fmt"
"net/smtp"
"os"
"strings"
"github.com/pkg/errors"
"github.com/axllent/mailpit/config"
"github.com/axllent/mailpit/internal/logger"
"github.com/axllent/mailpit/internal/tools"
)
// Wrapper to auto relay messages if configured
func autoRelayMessage(from string, to []string, data *[]byte) {
func autoRelayMessage(from string, to []string, data *[]byte) error {
if config.SMTPRelayConfig.BlockedRecipientsRegexp != nil {
filteredTo := []string{}
for _, address := range to {
@@ -29,15 +30,17 @@ func autoRelayMessage(from string, to []string, data *[]byte) {
}
if len(to) == 0 {
return
return nil
}
if config.SMTPRelayAll {
if err := Relay(from, to, *data); err != nil {
logger.Log().Errorf("[relay] error: %s", err.Error())
return errors.WithMessage(err, "[relay] error")
} else {
logger.Log().Debugf("[relay] sent message to %s from %s via %s:%d",
strings.Join(to, ", "), from, config.SMTPRelayConfig.Host, config.SMTPRelayConfig.Port)
logger.Log().Debugf(
"[relay] sent message to %s from %s via %s:%d",
strings.Join(to, ", "), from, config.SMTPRelayConfig.Host, config.SMTPRelayConfig.Port,
)
}
} else if config.SMTPRelayMatchingRegexp != nil {
filtered := []string{}
@@ -48,16 +51,20 @@ func autoRelayMessage(from string, to []string, data *[]byte) {
}
if len(filtered) == 0 {
return
return nil
}
if err := Relay(from, filtered, *data); err != nil {
logger.Log().Errorf("[relay] error: %s", err.Error())
return errors.WithMessage(err, "[relay] error")
} else {
logger.Log().Debugf("[relay] auto-relay message to %s from %s via %s:%d",
strings.Join(filtered, ", "), from, config.SMTPRelayConfig.Host, config.SMTPRelayConfig.Port)
logger.Log().Debugf(
"[relay] auto-relay message to %s from %s via %s:%d",
strings.Join(filtered, ", "), from, config.SMTPRelayConfig.Host, config.SMTPRelayConfig.Port,
)
}
}
return nil
}
func createRelaySMTPClient(config config.SMTPRelayConfigStruct, addr string) (*smtp.Client, error) {
@@ -134,26 +141,29 @@ func Relay(from string, to []string, msg []byte) error {
}
if err = c.Mail(from); err != nil {
return fmt.Errorf("error response to MAIL command: %s", err.Error())
return errors.WithMessage(err, "error sending MAIL command")
}
for _, addr := range to {
if err = c.Rcpt(addr); err != nil {
logger.Log().Warnf("error response to RCPT command for %s: %s", addr, err.Error())
if config.SMTPRelayConfig.ForwardSMTPErrors {
return errors.WithMessagef(err, "error response to RCPT command for %s", addr)
}
}
}
w, err := c.Data()
if err != nil {
return fmt.Errorf("error response to DATA command: %s", err.Error())
return errors.WithMessage(err, "error response to DATA command")
}
if _, err := w.Write(msg); err != nil {
return fmt.Errorf("error sending message: %s", err.Error())
return errors.WithMessage(err, "error sending message")
}
if err := w.Close(); err != nil {
return fmt.Errorf("error closing connection: %s", err.Error())
return errors.WithMessage(err, "error closing connection")
}
return c.Quit()
@@ -186,7 +196,10 @@ type loginAuth struct {
// LoginAuth authentication
func LoginAuth(username, password string) smtp.Auth {
return &loginAuth{username, password}
return &loginAuth{
username,
password,
}
}
func (a *loginAuth) Start(_ *smtp.ServerInfo) (string, []byte, error) {