Implement sendmail (#355)

* Implemented sendmail. This piggybacks on existing configuration to keep the change simple

* Changed privicy of new sendSMTP and sendSendmail functions

* Fixed Lint errors

* Seperated SMTP and sendmail into their own senders

* Making new structs private as they should not be used externally now

* Added sendmail setting to ini file

* Minor code cleanup

4 files changed, 73 insertions, 10 deletions

diff --git a/conf/app.ini b/conf/app.ini
index c46d52f2d5..cef7ae6d5b 100644
--- a/conf/app.ini
+++ b/conf/app.ini
@@ -226,6 +226,10 @@ USER =
 PASSWD =
 ; Use text/html as alternative format of content
 ENABLE_HTML_ALTERNATIVE = false
+; Enable sendmail (override SMTP)
+USE_SENDMAIL = false
+; Specifiy an alternative sendmail binary
+SENDMAIL_PATH = sendmail
 
 [cache]
 ; Either "memory", "redis", or "memcache", default is "memory"
diff --git a/models/mail.go b/models/mail.go
index 8f54d6651f..e66e316ba0 100644
--- a/models/mail.go
+++ b/models/mail.go
@@ -40,7 +40,7 @@ func InitMailRender(tmpls *template.Template) {
 
 // SendTestMail sends a test mail
 func SendTestMail(email string) error {
-	return gomail.Send(&mailer.Sender{}, mailer.NewMessage([]string{email}, "Gitea Test Email!", "Gitea Test Email!").Message)
+	return gomail.Send(mailer.Sender, mailer.NewMessage([]string{email}, "Gitea Test Email!", "Gitea Test Email!").Message)
 }
 
 // SendUserMail sends a mail to the user
diff --git a/modules/mailer/mailer.go b/modules/mailer/mailer.go
index 3dc2c4e531..3201075f3f 100644
--- a/modules/mailer/mailer.go
+++ b/modules/mailer/mailer.go
@@ -11,6 +11,7 @@ import (
 	"net"
 	"net/smtp"
 	"os"
+	"os/exec"
 	"strings"
 	"time"
 
@@ -87,12 +88,12 @@ func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
 	return nil, nil
 }
 
-// Sender mail sender
-type Sender struct {
+// Sender SMTP mail sender
+type smtpSender struct {
 }
 
 // Send send email
-func (s *Sender) Send(from string, to []string, msg io.WriterTo) error {
+func (s *smtpSender) Send(from string, to []string, msg io.WriterTo) error {
 	opts := setting.MailService
 
 	host, port, err := net.SplitHostPort(opts.Host)
@@ -195,14 +196,51 @@ func (s *Sender) Send(from string, to []string, msg io.WriterTo) error {
 	return client.Quit()
 }
 
-func processMailQueue() {
-	sender := &Sender{}
+// Sender sendmail mail sender
+type sendmailSender struct {
+}
+
+// Send send email
+func (s *sendmailSender) Send(from string, to []string, msg io.WriterTo) error {
+	var err error
+	var closeError error
+	var waitError error
+
+	args := []string{"-F", from, "-i"}
+	args = append(args, to...)
+	log.Trace("Sending with: %s %v", setting.MailService.SendmailPath, args)
+	cmd := exec.Command(setting.MailService.SendmailPath, args...)
+	pipe, err := cmd.StdinPipe()
+
+	if err != nil {
+		return err
+	}
+
+	if err = cmd.Start(); err != nil {
+		return err
+	}
+
+	_,err = msg.WriteTo(pipe)
 
+	// we MUST close the pipe or sendmail will hang waiting for more of the message
+	// Also we should wait on our sendmail command even if something fails
+	closeError = pipe.Close()
+	waitError =  cmd.Wait()
+	if err != nil {
+		return err
+	} else if closeError != nil {
+		return closeError
+	} else {
+		return waitError
+	}
+}
+
+func processMailQueue() {
 	for {
 		select {
 		case msg := <-mailQueue:
 			log.Trace("New e-mail sending request %s: %s", msg.GetHeader("To"), msg.Info)
-			if err := gomail.Send(sender, msg.Message); err != nil {
+			if err := gomail.Send(Sender, msg.Message); err != nil {
 				log.Error(3, "Fail to send emails %s: %s - %v", msg.GetHeader("To"), msg.Info, err)
 			} else {
 				log.Trace("E-mails sent %s: %s", msg.GetHeader("To"), msg.Info)
@@ -213,6 +251,9 @@ func processMailQueue() {
 
 var mailQueue chan *Message
 
+// Sender sender for sending mail synchronously
+var Sender gomail.Sender
+
 // NewContext start mail queue service
 func NewContext() {
 	// Need to check if mailQueue is nil because in during reinstall (user had installed
@@ -222,6 +263,13 @@ func NewContext() {
 		return
 	}
 
+
+	if setting.MailService.UseSendmail {
+		Sender = &sendmailSender{}
+	} else {
+		Sender = &smtpSender{}
+	}
+
 	mailQueue = make(chan *Message, setting.MailService.QueueLength)
 	go processMailQueue()
 }
diff --git a/modules/setting/setting.go b/modules/setting/setting.go
index fad884ae1e..81fcb4b150 100644
--- a/modules/setting/setting.go
+++ b/modules/setting/setting.go
@@ -858,18 +858,25 @@ func newSessionService() {
 
 // Mailer represents mail service.
 type Mailer struct {
+    // Mailer
 	QueueLength           int
 	Name                  string
-	Host                  string
 	From                  string
 	FromEmail             string
+	EnableHTMLAlternative bool
+
+	// SMTP sender
+	Host                  string
 	User, Passwd          string
 	DisableHelo           bool
 	HeloHostname          string
 	SkipVerify            bool
 	UseCertificate        bool
 	CertFile, KeyFile     string
-	EnableHTMLAlternative bool
+
+	// Sendmail sender
+	UseSendmail           bool
+	SendmailPath          string
 }
 
 var (
@@ -887,6 +894,8 @@ func newMailService() {
 	MailService = &Mailer{
 		QueueLength:           sec.Key("SEND_BUFFER_LEN").MustInt(100),
 		Name:                  sec.Key("NAME").MustString(AppName),
+		EnableHTMLAlternative: sec.Key("ENABLE_HTML_ALTERNATIVE").MustBool(),
+
 		Host:                  sec.Key("HOST").String(),
 		User:                  sec.Key("USER").String(),
 		Passwd:                sec.Key("PASSWD").String(),
@@ -896,7 +905,9 @@ func newMailService() {
 		UseCertificate:        sec.Key("USE_CERTIFICATE").MustBool(),
 		CertFile:              sec.Key("CERT_FILE").String(),
 		KeyFile:               sec.Key("KEY_FILE").String(),
-		EnableHTMLAlternative: sec.Key("ENABLE_HTML_ALTERNATIVE").MustBool(),
+
+		UseSendmail:           sec.Key("USE_SENDMAIL").MustBool(),
+		SendmailPath:          sec.Key("SENDMAIL_PATH").MustString("sendmail"),
 	}
 	MailService.From = sec.Key("FROM").MustString(MailService.User)