1 files changed, 35 insertions, 17 deletions

diff --git a/vendor/gopkg.in/gomail.v2/auth.go b/vendor/gopkg.in/gomail.v2/auth.go
index d28b83ab7..4bcdd0620 100644
--- a/vendor/gopkg.in/gomail.v2/auth.go
+++ b/vendor/gopkg.in/gomail.v2/auth.go
@@ -7,33 +7,51 @@ import (
 	"net/smtp"
 )
 
-// loginAuth is an smtp.Auth that implements the LOGIN authentication mechanism.
-type loginAuth struct {
+// plainAuth is an smtp.Auth that implements the PLAIN authentication mechanism.
+// It fallbacks to the LOGIN mechanism if it is the only mechanism advertised
+// by the server.
+type plainAuth struct {
 	username string
 	password string
 	host     string
+	login    bool
 }
 
-func (a *loginAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
-	if !server.TLS {
-		advertised := false
-		for _, mechanism := range server.Auth {
-			if mechanism == "LOGIN" {
-				advertised = true
-				break
-			}
-		}
-		if !advertised {
-			return "", nil, errors.New("gomail: unencrypted connection")
-		}
-	}
+func (a *plainAuth) Start(server *smtp.ServerInfo) (string, []byte, error) {
 	if server.Name != a.host {
 		return "", nil, errors.New("gomail: wrong host name")
 	}
-	return "LOGIN", nil, nil
+
+	var plain, login bool
+	for _, a := range server.Auth {
+		switch a {
+		case "PLAIN":
+			plain = true
+		case "LOGIN":
+			login = true
+		}
+	}
+
+	if !server.TLS && !plain && !login {
+		return "", nil, errors.New("gomail: unencrypted connection")
+	}
+
+	if !plain && login {
+		a.login = true
+		return "LOGIN", nil, nil
+	}
+
+	return "PLAIN", []byte("\x00" + a.username + "\x00" + a.password), nil
 }
 
-func (a *loginAuth) Next(fromServer []byte, more bool) ([]byte, error) {
+func (a *plainAuth) Next(fromServer []byte, more bool) ([]byte, error) {
+	if !a.login {
+		if more {
+			return nil, errors.New("gomail: unexpected server challenge")
+		}
+		return nil, nil
+	}
+
 	if !more {
 		return nil, nil
 	}