1 files changed, 67 insertions, 0 deletions
diff --git a/libgo/go/net/smtp/auth.go b/libgo/go/net/smtp/auth.go
new file mode 100644
index 00000000000..10a757fc643
--- /dev/null
+++ b/libgo/go/net/smtp/auth.go
@@ -0,0 +1,67 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package smtp
+
+import "errors"
+
+// Auth is implemented by an SMTP authentication mechanism.
+type Auth interface {
+	// Start begins an authentication with a server.
+	// It returns the name of the authentication protocol
+	// and optionally data to include in the initial AUTH message
+	// sent to the server. It can return proto == "" to indicate
+	// that the authentication should be skipped.
+	// If it returns a non-nil error, the SMTP client aborts
+	// the authentication attempt and closes the connection.
+	Start(server *ServerInfo) (proto string, toServer []byte, err error)
+
+	// Next continues the authentication. The server has just sent
+	// the fromServer data. If more is true, the server expects a
+	// response, which Next should return as toServer; otherwise
+	// Next should return toServer == nil.
+	// If Next returns a non-nil error, the SMTP client aborts
+	// the authentication attempt and closes the connection.
+	Next(fromServer []byte, more bool) (toServer []byte, err error)
+}
+
+// ServerInfo records information about an SMTP server.
+type ServerInfo struct {
+	Name string   // SMTP server name
+	TLS  bool     // using TLS, with valid certificate for Name
+	Auth []string // advertised authentication mechanisms
+}
+
+type plainAuth struct {
+	identity, username, password string
+	host                         string
+}
+
+// PlainAuth returns an Auth that implements the PLAIN authentication
+// mechanism as defined in RFC 4616.
+// The returned Auth uses the given username and password to authenticate
+// on TLS connections to host and act as identity. Usually identity will be
+// left blank to act as username.
+func PlainAuth(identity, username, password, host string) Auth {
+	return &plainAuth{identity, username, password, host}
+}
+
+func (a *plainAuth) Start(server *ServerInfo) (string, []byte, error) {
+	if !server.TLS {
+		return "", nil, errors.New("unencrypted connection")
+	}
+	if server.Name != a.host {
+		return "", nil, errors.New("wrong host name")
+	}
+	resp := []byte(a.identity + "\x00" + a.username + "\x00" + a.password)
+	return "PLAIN", resp, nil
+}
+
+func (a *plainAuth) Next(fromServer []byte, more bool) ([]byte, error) {
+	if more {
+		// We've already sent everything.
+		return nil, errors.New("unexpected server challenge")
+	}
+	return nil, nil
+}