From 51eec742067496067b368bc752ce17b68fee927f Mon Sep 17 00:00:00 2001
From: nimjor <76883392+nimjor@users.noreply.github.com>
Date: Thu, 5 Oct 2023 10:46:06 -0500
Subject: [PATCH] Smtp logger (#3339)

* allow passing Logger instance in config

* pass main app logger to smtp config

* implement smtp.Logger in smtpsrv to make logs go through app.cfg.Logger https://github.com/target/goalert/issues/3335

* filter out TCP ECONNRESET error messages

* early return instead of negation; add TODO

---------

Co-authored-by: Jordan Nimlos <jordan.nimlos@bestbuy.com>
---
 app/initsmtpsrv.go |  1 +
 smtpsrv/config.go  |  2 ++
 smtpsrv/server.go  | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/app/initsmtpsrv.go b/app/initsmtpsrv.go
index dc92a57f86..b8f02fb741 100644
--- a/app/initsmtpsrv.go
+++ b/app/initsmtpsrv.go
@@ -24,6 +24,7 @@ func (app *App) initSMTPServer(ctx context.Context) error {
 		TLSConfig:         app.cfg.TLSConfigSMTP,
 		MaxRecipients:     app.cfg.SMTPMaxRecipients,
 		BackgroundContext: app.LogBackgroundContext,
+		Logger:            app.cfg.Logger,
 		AuthorizeFunc: func(ctx context.Context, id string) (context.Context, error) {
 			tok, _, err := authtoken.Parse(id, nil)
 			if err != nil {
diff --git a/smtpsrv/config.go b/smtpsrv/config.go
index d9a7f74998..de425c37d9 100644
--- a/smtpsrv/config.go
+++ b/smtpsrv/config.go
@@ -5,6 +5,7 @@ import (
 	"crypto/tls"
 
 	"github.com/target/goalert/alert"
+	"github.com/target/goalert/util/log"
 )
 
 // Config is used to configure the SMTP server.
@@ -15,6 +16,7 @@ type Config struct {
 	MaxRecipients  int
 
 	BackgroundContext func() context.Context
+	Logger            *log.Logger
 
 	AuthorizeFunc   func(ctx context.Context, id string) (context.Context, error)
 	CreateAlertFunc func(ctx context.Context, a *alert.Alert) error
diff --git a/smtpsrv/server.go b/smtpsrv/server.go
index b5267e633b..411bfa66e6 100644
--- a/smtpsrv/server.go
+++ b/smtpsrv/server.go
@@ -2,12 +2,43 @@ package smtpsrv
 
 import (
 	"context"
+	"errors"
+	"fmt"
 	"net"
+	"strings"
 	"time"
 
 	"github.com/emersion/go-smtp"
+	"github.com/target/goalert/util/log"
 )
 
+// SMTPLogger implements the smtp.Logger interface using the main app Logger.
+type SMTPLogger struct {
+	logger *log.Logger
+}
+
+// Printf adheres to smtp.Server's Logger interface.
+func (l *SMTPLogger) Printf(format string, v ...interface{}) {
+	s := fmt.Sprintf(format, v...)
+	// TODO: Uses string compare to filter out errors caused by TCP health checks,
+	// remove once https://github.com/emersion/go-smtp/issues/236 has been fixed.
+	if strings.Contains(s, "read: connection reset by peer") {
+		return
+	}
+	l.logger.Error(context.Background(), errors.New(s))
+}
+
+// Print adheres to smtp.Server's Logger interface.
+func (l *SMTPLogger) Println(v ...interface{}) {
+	s := fmt.Sprint(v...)
+	// TODO: Uses string compare to filter out errors caused by TCP health checks,
+	// remove once https://github.com/emersion/go-smtp/issues/236 has been fixed.
+	if strings.Contains(s, "read: connection reset by peer") {
+		return
+	}
+	l.logger.Error(context.Background(), errors.New(s))
+}
+
 // Server implements an SMTP server that creates alerts.
 type Server struct {
 	cfg Config
@@ -19,6 +50,7 @@ func NewServer(cfg Config) *Server {
 	s := &Server{cfg: cfg}
 
 	srv := smtp.NewServer(s)
+	srv.ErrorLog = &SMTPLogger{logger: cfg.Logger}
 	srv.Domain = cfg.Domain
 	srv.ReadTimeout = 10 * time.Second
 	srv.WriteTimeout = 10 * time.Second