feat(cdc): Add support for SCRAM SASL mechanism (#7765)

We used to support only the PLAIN mechanism for SASL in CDC-Kafka.
This commit adds support for SCRAM-SHA-256 and SCRAM-SHA-512.

dgraph/cmd/alpha/run.go

@@ -233,6 +233,8 @@ they form a Raft group and provide synchronous replication.
 			"The SASL username for Kafka.").
 		Flag("sasl-password",
 			"The SASL password for Kafka.").
+		Flag("sasl-mechanism",
+			"The SASL mechanism for Kafka (PLAIN, SCRAM-SHA-256 or SCRAM-SHA-512)").
 		Flag("ca-cert",
 			"The path to CA cert file for TLS encryption.").
 		Flag("client-cert",

go.mod

@@ -65,6 +65,7 @@ require (
 	github.com/stretchr/testify v1.6.1
 	github.com/tinylib/msgp v1.1.5 // indirect
 	github.com/twpayne/go-geom v1.0.5
+	github.com/xdg/scram v0.0.0-20180814205039-7eeb5667e42c
 	go.etcd.io/etcd v0.0.0-20190228193606-a943ad0ee4c9
 	go.opencensus.io v0.22.5
 	go.uber.org/zap v1.16.0

go.sum

@@ -605,7 +605,9 @@ github.com/vektah/dataloaden v0.2.1-0.20190515034641-a19b9a6e7c9e/go.mod h1:/HUd
 github.com/vektah/gqlparser/v2 v2.1.0/go.mod h1:SyUiHgLATUR8BiYURfTirrTcGpcE+4XkV2se04Px1Ms=
 github.com/willf/bitset v1.1.10 h1:NotGKqX0KwQ72NUzqrjZq5ipPNDQex9lo3WpaS8L2sc=
 github.com/willf/bitset v1.1.10/go.mod h1:RjeCKbqT1RxIR/KWY6phxZiaY1IyutSBfGjNPySAYV4=
+github.com/xdg/scram v0.0.0-20180814205039-7eeb5667e42c h1:u40Z8hqBAAQyv+vATcGgV0YCnDjqSL7/q/JyPhhJSPk=
 github.com/xdg/scram v0.0.0-20180814205039-7eeb5667e42c/go.mod h1:lB8K/P019DLNhemzwFU4jHLhdvlE6uDZjXFejJXr49I=
+github.com/xdg/stringprep v1.0.0 h1:d9X0esnoa3dFsV0FG35rAT0RIhYFlPq7MiP+DW89La0=
 github.com/xdg/stringprep v1.0.0/go.mod h1:Jhud4/sHMO4oL310DaZAKk9ZaJ08SJfe+sJh0HrGL1Y=
 github.com/xeipuuv/gojsonpointer v0.0.0-20180127040702-4e3ac2762d5f/go.mod h1:N2zxlSyiKSe5eX1tZViRH5QA0qijqEDrYZiPEAiq3wU=
 github.com/xeipuuv/gojsonreference v0.0.0-20180127040603-bd5ef7bd5415/go.mod h1:GwrjFmJcFw6At/Gs6z4yjiIwzuJ1/+UwLxMQDVQXShQ=

worker/server_state.go

@@ -44,7 +44,7 @@ const (
 		`snapshot-after-duration=30m; pending-proposals=256; idx=; group=;`
 	SecurityDefaults = `token=; whitelist=;`
 	CDCDefaults      = `file=; kafka=; sasl_user=; sasl_password=; ca_cert=; client_cert=; ` +
-		`client_key=;`
+		`client_key=; sasl-mechanism=PLAIN;`
 	LimitDefaults = `mutations=allow; query-edge=1000000; normalize-node=10000; ` +
 		`mutations-nquad=1000000; disallow-drop=false; query-timeout=0ms; txn-abort-after=5m;` +
 		`max-pending-queries=10000;  max-retries=-1;`

worker/sink_handler.go

@@ -17,6 +17,8 @@
 package worker
 
 import (
+	"crypto/sha256"
+	"crypto/sha512"
 	"crypto/tls"
 	"crypto/x509"
 	"encoding/binary"
@@ -27,6 +29,7 @@ import (
 	"strings"
 
 	"github.com/pkg/errors"
+	"github.com/xdg/scram"
 
 	"github.com/Shopify/sarama"
 
@@ -116,6 +119,27 @@ func newKafkaSink(config *z.SuperFlag) (Sink, error) {
 		saramaConf.Net.SASL.User = config.GetString("sasl-user")
 		saramaConf.Net.SASL.Password = config.GetString("sasl-password")
 	}
+	mechanism := config.GetString("sasl-mechanism")
+	if mechanism != "" {
+		switch mechanism {
+		case sarama.SASLTypeSCRAMSHA256:
+			saramaConf.Net.SASL.Mechanism = sarama.SASLTypeSCRAMSHA256
+			saramaConf.Net.SASL.SCRAMClientGeneratorFunc = func() sarama.SCRAMClient {
+				return &scramClient{HashGeneratorFcn: sha256.New}
+			}
+		case sarama.SASLTypeSCRAMSHA512:
+			saramaConf.Net.SASL.Mechanism = sarama.SASLTypeSCRAMSHA512
+			saramaConf.Net.SASL.SCRAMClientGeneratorFunc = func() sarama.SCRAMClient {
+				return &scramClient{HashGeneratorFcn: sha512.New}
+			}
+		case sarama.SASLTypePlaintext:
+			saramaConf.Net.SASL.Mechanism = sarama.SASLTypePlaintext
+		default:
+			return nil, errors.Errorf("Invalid SASL mechanism. Valid mechanisms are: %s, %s and %s",
+				sarama.SASLTypePlaintext, sarama.SASLTypeSCRAMSHA256, sarama.SASLTypeSCRAMSHA512)
+		}
+	}
+
 	brokers := strings.Split(config.GetString("kafka"), ",")
 	client, err := sarama.NewClient(brokers, saramaConf)
 	if err != nil {
@@ -197,3 +221,27 @@ func newFileSink(path *z.SuperFlag) (Sink, error) {
 		fileWriter: w,
 	}, nil
 }
+
+type scramClient struct {
+	*scram.Client
+	*scram.ClientConversation
+	scram.HashGeneratorFcn
+}
+
+func (sc *scramClient) Begin(userName, password, authzID string) (err error) {
+	sc.Client, err = sc.HashGeneratorFcn.NewClient(userName, password, authzID)
+	if err != nil {
+		return err
+	}
+	sc.ClientConversation = sc.Client.NewConversation()
+	return nil
+}
+
+func (sc *scramClient) Step(challenge string) (response string, err error) {
+	response, err = sc.ClientConversation.Step(challenge)
+	return
+}
+
+func (sc *scramClient) Done() bool {
+	return sc.ClientConversation.Done()
+}