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smtp-gotify.go
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smtp-gotify.go
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package main
import (
"errors"
"fmt"
"github.com/flashmob/go-guerrilla"
"github.com/flashmob/go-guerrilla/backends"
"github.com/flashmob/go-guerrilla/log"
"github.com/flashmob/go-guerrilla/mail"
"github.com/jhillyerd/enmime"
"github.com/urfave/cli/v2"
"io/ioutil"
"net/http"
"net/url"
"os"
"os/signal"
"strings"
"syscall"
"time"
)
type SmtpConfig struct {
smtpListen string
smtpPrimaryHost string
}
type GofityConfig struct {
gotifyPriority string
gotifyAPIToken string
gotifyURL string
titleTemplate string
messageTemplate string
}
func GetHostname() string {
hostname, err := os.Hostname()
if err != nil {
panic(fmt.Sprintf("Unable to detect hostname: %s", err))
}
return hostname
}
func main() {
app := cli.NewApp()
app.Name = "smtp-gotify"
app.Usage = "A small program which listens for SMTP and sends " +
"all incoming Email messages to your Gotify server."
app.Version = "UNKNOWN_RELEASE"
app.Action = func(c *cli.Context) error {
// Required flags are not supported, see https://github.com/urfave/cli/issues/85
if !c.IsSet("gotify-url") {
return cli.NewExitError("Gotify URL is missing. See `--help`", 2)
}
if !c.IsSet("gotify-api-token") {
return cli.NewExitError("Gotify API token is missing. See `--help`", 2)
}
smtpConfig := &SmtpConfig{
smtpListen: c.String("smtp-listen"),
smtpPrimaryHost: c.String("smtp-primary-host"),
}
gotifyConfig := &GofityConfig{
gotifyPriority: c.String("gotify-priority"),
gotifyAPIToken: c.String("gotify-api-token"),
gotifyURL: c.String("gotify-url"),
titleTemplate: c.String("title-template"),
messageTemplate: c.String("message-template"),
}
d, err := SmtpStart(smtpConfig, gotifyConfig)
if err != nil {
panic(fmt.Sprintf("start error: %s", err))
}
sigHandler(d)
return nil
}
app.Flags = []cli.Flag{
&cli.StringFlag{
Name: "smtp-listen",
Value: "127.0.0.1:2525",
Usage: "SMTP: TCP address to listen to",
EnvVars: []string{"SG_SMTP_LISTEN"},
},
&cli.StringFlag{
Name: "smtp-primary-host",
Value: GetHostname(),
Usage: "SMTP: primary host",
EnvVars: []string{"SG_SMTP_PRIMARY_HOST"},
},
&cli.StringFlag{
Name: "gotify-priority",
Value: "5",
Usage: "Gotify message priority",
EnvVars: []string{"GOFITY_PRIORITY"},
},
&cli.StringFlag{
Name: "gotify-api-token",
Usage: "Gotify API token",
EnvVars: []string{"GOTIFY_TOKEN"},
},
&cli.StringFlag{
Name: "gotify-url",
Usage: "Gotify server URL",
EnvVars: []string{"GOTIFY_URL"},
},
&cli.StringFlag{
Name: "title-template",
Usage: "Gotify notification title template",
Value: "{subject}",
EnvVars: []string{"GOTIFY_TITLE_TEMPLATE"},
},
&cli.StringFlag{
Name: "message-template",
Usage: "Gotify notification message template",
Value: "{body}",
EnvVars: []string{"GOTIFY_MESSAGE_TEMPLATE"},
},
}
err := app.Run(os.Args)
if err != nil {
os.Exit(1)
}
}
func SmtpStart(
smtpConfig *SmtpConfig, gotifyConfig *GofityConfig) (guerrilla.Daemon, error) {
cfg := &guerrilla.AppConfig{LogFile: log.OutputStdout.String()}
cfg.AllowedHosts = []string{"."}
sc := guerrilla.ServerConfig{
ListenInterface: smtpConfig.smtpListen,
IsEnabled: true,
}
cfg.Servers = append(cfg.Servers, sc)
bcfg := backends.BackendConfig{
"save_workers_size": 3,
"save_process": "HeadersParser|Header|Hasher|GotifyBot",
"log_received_mails": true,
"primary_mail_host": smtpConfig.smtpPrimaryHost,
}
cfg.BackendConfig = bcfg
daemon := guerrilla.Daemon{Config: cfg}
daemon.AddProcessor("GotifyBot", GotifyBotProcessorFactory(gotifyConfig))
err := daemon.Start()
return daemon, err
}
func GotifyBotProcessorFactory(
gotifyConfig *GofityConfig) func() backends.Decorator {
return func() backends.Decorator {
// https://github.com/flashmob/go-guerrilla/wiki/Backends,-configuring-and-extending
return func(p backends.Processor) backends.Processor {
return backends.ProcessWith(
func(e *mail.Envelope, task backends.SelectTask) (backends.Result, error) {
if task == backends.TaskSaveMail {
err := SendEmailToGotify(e, gotifyConfig)
if err != nil {
return backends.NewResult(fmt.Sprintf("554 Error: %s", err)), err
}
return p.Process(e, task)
}
return p.Process(e, task)
},
)
}
}
}
func SendEmailToGotify(e *mail.Envelope,
gotifyConfig *GofityConfig) error {
title, message := FormatEmail(e,
gotifyConfig.titleTemplate, gotifyConfig.messageTemplate)
for _, appToken := range strings.Split(gotifyConfig.gotifyAPIToken, ",") {
// Apparently the native golang's http client supports
// http, https and socks5 proxies via HTTP_PROXY/HTTPS_PROXY env vars
// out of the box.
//
// See: https://golang.org/pkg/net/http/#ProxyFromEnvironment
resp, err := http.PostForm(
fmt.Sprintf(
"%smessage?token=%s",
gotifyConfig.gotifyURL,
appToken,
),
url.Values{
"title": {title},
"message": {message},
"priority": {gotifyConfig.gotifyPriority},
},
)
if err != nil {
return errors.New(SanitizeBotToken(err.Error(), appToken))
}
if resp.StatusCode != 200 {
body, _ := ioutil.ReadAll(resp.Body)
return errors.New(fmt.Sprintf(
"Non-200 response from Gotify Server: (%d) %s",
resp.StatusCode,
SanitizeBotToken(EscapeMultiLine(body), appToken),
))
}
}
return nil
}
func FormatEmail(e *mail.Envelope,
titleTemplate string, messageTemplate string) (string, string) {
reader := e.NewReader()
env, err := enmime.ReadEnvelope(reader)
if err != nil {
return fmt.Sprintf("smtp-gotify: Could not parse email"),
fmt.Sprintf("%s\n\nError occurred during email parsing: %s", e, err)
}
text := env.Text
if text == "" {
text = e.Data.String()
}
r := strings.NewReplacer(
"\\n", "\n",
"{from}", e.MailFrom.String(),
"{to}", MapAddresses(e.RcptTo),
"{subject}", env.GetHeader("subject"),
"{body}", text,
)
return r.Replace(titleTemplate), r.Replace(messageTemplate)
}
func MapAddresses(a []mail.Address) string {
s := []string{}
for _, aa := range a {
s = append(s, aa.String())
}
return strings.Join(s, ", ")
}
func EscapeMultiLine(b []byte) string {
// Apparently errors returned by smtp must not contain newlines,
// otherwise the data after the first newline is not getting
// to the parsed message.
s := string(b)
s = strings.Replace(s, "\r", "\\r", -1)
s = strings.Replace(s, "\n", "\\n", -1)
return s
}
func SanitizeBotToken(s string, botToken string) string {
return strings.Replace(s, botToken, "***", -1)
}
func sigHandler(d guerrilla.Daemon) {
signalChannel := make(chan os.Signal, 1)
signal.Notify(signalChannel,
syscall.SIGTERM,
syscall.SIGQUIT,
syscall.SIGINT,
syscall.SIGKILL,
os.Kill,
)
for range signalChannel {
d.Log().Infof("Shutdown signal caught")
go func() {
select {
// exit if graceful shutdown not finished in 60 sec.
case <-time.After(time.Second * 60):
d.Log().Error("graceful shutdown timed out")
os.Exit(1)
}
}()
d.Shutdown()
d.Log().Infof("Shutdown completed, exiting.")
return
}
}