Add support for SASL plain text authentication

broker.go

@@ -2,6 +2,7 @@ package sarama
 
 import (
 	"crypto/tls"
+	"encoding/binary"
 	"fmt"
 	"io"
 	"net"
@@ -82,6 +83,18 @@ func (b *Broker) Open(conf *Config) error {
 		b.conn = newBufConn(b.conn)
 
 		b.conf = conf
+
+		if conf.Net.SASL.Enable {
+			err = b.doSASLPlainAuth()
+			if err != nil {
+				Logger.Printf("SASL authentication with broker %s failed\n", b.addr)
+				_ = b.Close()
+				return
+			} else {
+				Logger.Printf("SASL authentication with broker %s succeeded\n", b.addr)
+			}
+		}
+
 		b.done = make(chan bool)
 		b.responses = make(chan responsePromise, b.conf.Net.MaxOpenRequests-1)
 
@@ -454,3 +467,52 @@ func (b *Broker) responseReceiver() {
 	}
 	close(b.done)
 }
+
+// Kafka 0.10.0 plans to support SASL Plain and Kerberos as per PR #812 (KIP-43)/(JIRA KAFKA-3149)
+// Some hosted kafka services such as IBM Message Hub already offer SASL/PLAIN auth with Kafka 0.9
+//
+// In SASL Plain, Kafka expects the auth header to be in the following format
+// Message format (from https://tools.ietf.org/html/rfc4616):
+//
+//   message   = [authzid] UTF8NUL authcid UTF8NUL passwd
+//   authcid   = 1*SAFE ; MUST accept up to 255 octets
+//   authzid   = 1*SAFE ; MUST accept up to 255 octets
+//   passwd    = 1*SAFE ; MUST accept up to 255 octets
+//   UTF8NUL   = %x00 ; UTF-8 encoded NUL character
+//
+//   SAFE      = UTF1 / UTF2 / UTF3 / UTF4
+//                  ;; any UTF-8 encoded Unicode character except NUL
+//
+// When credentials are valid, Kafka returns a 4 byte array of null characters.
+// When credentials are invalid, Kafka closes the connection. This does not seem to be the ideal way
+// of responding to bad credentials but thats how its being done today.
+func (b *Broker) doSASLPlainAuth() error {
+	length := 1 + len(b.conf.Net.SASL.User) + 1 + len(b.conf.Net.SASL.Password)
+	authBytes := make([]byte, length+4) //4 byte length header + auth data
+	binary.BigEndian.PutUint32(authBytes, uint32(length))
+	copy(authBytes[4:], []byte("\x00"+b.conf.Net.SASL.User+"\x00"+b.conf.Net.SASL.Password))
+
+	err := b.conn.SetWriteDeadline(time.Now().Add(b.conf.Net.WriteTimeout))
+	if err != nil {
+		Logger.Printf("Failed to set write deadline when doing SASL auth: %s\n", err.Error())
+		return nil
+	}
+
+	_, err = b.conn.Write(authBytes)
+	if err != nil {
+		Logger.Printf("Failed to write SASL auth header to broker: %s\n", err.Error())
+		return nil
+	}
+
+	header := make([]byte, 4)
+	n, err := io.ReadFull(b.conn, header)
+	// If the credentials are valid, we would get a 4 byte response filled with null characters.
+	// Otherwise, the broker closes the connection and we get an EOF
+	if err != nil {
+		Logger.Printf("Failed to read response while authenticating with SASL: %s\n", err.Error())
+		return err
+	}
+
+	Logger.Printf("SASL authentication successful:%v - %v\n", n, header)
+	return nil
+}

config.go

@@ -33,6 +33,17 @@ type Config struct {
 			Config *tls.Config
 		}
 
+		// SASL based authentication with broker. While there are multiple SASL authentication methods
+		// the current implementation is limited to plaintext (SASL/PLAIN) authentication
+		SASL struct {
+			// Whether or not to use SASL authentication when connecting to the broker
+			// (defaults to false).
+			Enable bool
+			//username and password for SASL/PLAIN authentication
+			User     string
+			Password string
+		}
+
 		// KeepAlive specifies the keep-alive period for an active network connection.
 		// If zero, keep-alives are disabled. (default is 0: disabled).
 		KeepAlive time.Duration
@@ -257,6 +268,14 @@ func (c *Config) Validate() error {
 	if c.Net.TLS.Enable == false && c.Net.TLS.Config != nil {
 		Logger.Println("Net.TLS is disabled but a non-nil configuration was provided.")
 	}
+	if c.Net.SASL.Enable == false {
+		if c.Net.SASL.User != "" {
+			Logger.Println("Net.SASL is disabled but a non-empty username was provided.")
+		}
+		if c.Net.SASL.Password != "" {
+			Logger.Println("Net.SASL is disabled but a non-empty password was provided.")
+		}
+	}
 	if c.Producer.RequiredAcks > 1 {
 		Logger.Println("Producer.RequiredAcks > 1 is deprecated and will raise an exception with kafka >= 0.8.2.0.")
 	}
@@ -294,6 +313,10 @@ func (c *Config) Validate() error {
 		return ConfigurationError("Net.WriteTimeout must be > 0")
 	case c.Net.KeepAlive < 0:
 		return ConfigurationError("Net.KeepAlive must be >= 0")
+	case (c.Net.SASL.Enable == true) && (c.Net.SASL.User == ""):
+		return ConfigurationError("Net.SASL.User must not be empty when SASL is enabled")
+	case (c.Net.SASL.Enable == true) && (c.Net.SASL.Password == ""):
+		return ConfigurationError("Net.SASL.Password must not be empty when SASL is enabled")
 	}
 
 	// validate the Metadata values