Add SCRAM authentication

2019-04-16 20:46:23 -05:00
parent 5c9679850f
commit 5044e8473a
6 changed files with 439 additions and 0 deletions
@@ -0,0 +1,255 @@
+// SCRAM-SHA-256 authentication
+//
+// Resources:
+//   https://tools.ietf.org/html/rfc5802
+//   https://tools.ietf.org/html/rfc8265
+//   https://www.postgresql.org/docs/current/sasl-authentication.html
+//
+// Inspiration drawn from other implementations:
+//   https://github.com/lib/pq/pull/608
+//   https://github.com/lib/pq/pull/788
+//   https://github.com/lib/pq/pull/833
+package pgx
+
+import (
+	"bytes"
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strconv"
+
+	"github.com/jackc/pgx/pgproto3"
+	"golang.org/x/crypto/pbkdf2"
+	"golang.org/x/text/secure/precis"
+)
+
+const clientNonceLen = 18
+
+// Perform SCRAM authentication.
+func (c *Conn) scramAuth(serverAuthMechanisms []string) error {
+	sc, err := newScramClient(serverAuthMechanisms, c.config.Password)
+	if err != nil {
+		return err
+	}
+
+	// Send client-first-message in a SASLInitialResponse
+	saslInitialResponse := &pgproto3.SASLInitialResponse{
+		AuthMechanism: "SCRAM-SHA-256",
+		Data:          sc.clientFirstMessage(),
+	}
+	_, err = c.conn.Write(saslInitialResponse.Encode(nil))
+	if err != nil {
+		return err
+	}
+
+	// Receive server-first-message payload in a AuthenticationSASLContinue.
+	authMsg, err := c.rxAuthMsg(pgproto3.AuthTypeSASLContinue)
+	if err != nil {
+		return err
+	}
+	err = sc.recvServerFirstMessage(authMsg.SASLData)
+	if err != nil {
+		return err
+	}
+
+	// Send client-final-message in a SASLResponse
+	saslResponse := &pgproto3.SASLResponse{
+		Data: []byte(sc.clientFinalMessage()),
+	}
+	_, err = c.conn.Write(saslResponse.Encode(nil))
+	if err != nil {
+		return err
+	}
+
+	// Receive server-final-message payload in a AuthenticationSASLFinal.
+	authMsg, err = c.rxAuthMsg(pgproto3.AuthTypeSASLFinal)
+	if err != nil {
+		return err
+	}
+	return sc.recvServerFinalMessage(authMsg.SASLData)
+}
+
+func (c *Conn) rxAuthMsg(typ uint32) (*pgproto3.Authentication, error) {
+	msg, err := c.rxMsg()
+	if err != nil {
+		return nil, err
+	}
+	authMsg, ok := msg.(*pgproto3.Authentication)
+	if !ok {
+		return nil, errors.New("unexpected message type")
+	}
+	if authMsg.Type != typ {
+		return nil, errors.New("unexpected auth type")
+	}
+
+	return authMsg, nil
+}
+
+type scramClient struct {
+	serverAuthMechanisms []string
+	password             []byte
+	clientNonce          []byte
+
+	clientFirstMessageBare []byte
+
+	serverFirstMessage   []byte
+	clientAndServerNonce []byte
+	salt                 []byte
+	iterations           int
+
+	saltedPassword []byte
+	authMessage    []byte
+}
+
+func newScramClient(serverAuthMechanisms []string, password string) (*scramClient, error) {
+	sc := &scramClient{
+		serverAuthMechanisms: serverAuthMechanisms,
+	}
+
+	// Ensure server supports SCRAM-SHA-256
+	hasScramSHA256 := false
+	for _, mech := range sc.serverAuthMechanisms {
+		if mech == "SCRAM-SHA-256" {
+			hasScramSHA256 = true
+			break
+		}
+	}
+	if !hasScramSHA256 {
+		return nil, errors.New("server does not support SCRAM-SHA-256")
+	}
+
+	// precis.OpaqueString is equivalent to SASLprep for password.
+	var err error
+	sc.password, err = precis.OpaqueString.Bytes([]byte(password))
+	if err != nil {
+		// PostgreSQL allows passwords invalid according to SCRAM / SASLprep.
+		sc.password = []byte(password)
+	}
+
+	buf := make([]byte, clientNonceLen)
+	_, err = rand.Read(buf)
+	if err != nil {
+		return nil, err
+	}
+	sc.clientNonce = make([]byte, base64.RawStdEncoding.EncodedLen(len(buf)))
+	base64.RawStdEncoding.Encode(sc.clientNonce, buf)
+
+	return sc, nil
+}
+
+func (sc *scramClient) clientFirstMessage() []byte {
+	sc.clientFirstMessageBare = []byte(fmt.Sprintf("n=,r=%s", sc.clientNonce))
+	return []byte(fmt.Sprintf("n,,%s", sc.clientFirstMessageBare))
+}
+
+func (sc *scramClient) recvServerFirstMessage(serverFirstMessage []byte) error {
+	sc.serverFirstMessage = serverFirstMessage
+	buf := serverFirstMessage
+	if !bytes.HasPrefix(buf, []byte("r=")) {
+		return errors.New("invalid SCRAM server-first-message received from server: did not include r=")
+	}
+	buf = buf[2:]
+
+	idx := bytes.IndexByte(buf, ',')
+	if idx == -1 {
+		return errors.New("invalid SCRAM server-first-message received from server: did not include s=")
+	}
+	sc.clientAndServerNonce = buf[:idx]
+	buf = buf[idx+1:]
+
+	if !bytes.HasPrefix(buf, []byte("s=")) {
+		return errors.New("invalid SCRAM server-first-message received from server: did not include s=")
+	}
+	buf = buf[2:]
+
+	idx = bytes.IndexByte(buf, ',')
+	if idx == -1 {
+		return errors.New("invalid SCRAM server-first-message received from server: did not include i=")
+	}
+	saltStr := buf[:idx]
+	buf = buf[idx+1:]
+
+	if !bytes.HasPrefix(buf, []byte("i=")) {
+		return errors.New("invalid SCRAM server-first-message received from server: did not include i=")
+	}
+	buf = buf[2:]
+	iterationsStr := buf
+
+	var err error
+	sc.salt, err = base64.StdEncoding.DecodeString(string(saltStr))
+	if err != nil {
+		return fmt.Errorf("invalid SCRAM salt received from server: %v", err)
+	}
+
+	sc.iterations, err = strconv.Atoi(string(iterationsStr))
+	if err != nil || sc.iterations <= 0 {
+		return fmt.Errorf("invalid SCRAM iteration count received from server: %s", iterationsStr)
+	}
+
+	if !bytes.HasPrefix(sc.clientAndServerNonce, sc.clientNonce) {
+		return errors.New("invalid SCRAM nonce: did not start with client nonce")
+	}
+
+	if len(sc.clientAndServerNonce) <= len(sc.clientNonce) {
+		return errors.New("invalid SCRAM nonce: did not include server nonce")
+	}
+
+	return nil
+}
+
+func (sc *scramClient) clientFinalMessage() string {
+	clientFinalMessageWithoutProof := []byte(fmt.Sprintf("c=biws,r=%s", sc.clientAndServerNonce))
+
+	sc.saltedPassword = pbkdf2.Key([]byte(sc.password), sc.salt, sc.iterations, 32, sha256.New)
+	sc.authMessage = bytes.Join([][]byte{sc.clientFirstMessageBare, sc.serverFirstMessage, clientFinalMessageWithoutProof}, []byte(","))
+
+	clientProof := computeClientProof(sc.saltedPassword, sc.authMessage)
+
+	return fmt.Sprintf("%s,p=%s", clientFinalMessageWithoutProof, clientProof)
+}
+
+func (sc *scramClient) recvServerFinalMessage(serverFinalMessage []byte) error {
+	if !bytes.HasPrefix(serverFinalMessage, []byte("v=")) {
+		return errors.New("invalid SCRAM server-final-message received from server")
+	}
+
+	serverSignature := serverFinalMessage[2:]
+
+	if !hmac.Equal(serverSignature, computeServerSignature(sc.saltedPassword, sc.authMessage)) {
+		return errors.New("invalid SCRAM ServerSignature received from server")
+	}
+
+	return nil
+}
+
+func computeHMAC(key, msg []byte) []byte {
+	mac := hmac.New(sha256.New, key)
+	mac.Write(msg)
+	return mac.Sum(nil)
+}
+
+func computeClientProof(saltedPassword, authMessage []byte) []byte {
+	clientKey := computeHMAC(saltedPassword, []byte("Client Key"))
+	storedKey := sha256.Sum256(clientKey)
+	clientSignature := computeHMAC(storedKey[:], authMessage)
+
+	clientProof := make([]byte, len(clientSignature))
+	for i := 0; i < len(clientSignature); i++ {
+		clientProof[i] = clientKey[i] ^ clientSignature[i]
+	}
+
+	buf := make([]byte, base64.StdEncoding.EncodedLen(len(clientProof)))
+	base64.StdEncoding.Encode(buf, clientProof)
+	return buf
+}
+
+func computeServerSignature(saltedPassword []byte, authMessage []byte) []byte {
+	serverKey := computeHMAC(saltedPassword, []byte("Server Key"))
+	serverSignature := computeHMAC(serverKey[:], authMessage)
+	buf := make([]byte, base64.StdEncoding.EncodedLen(len(serverSignature)))
+	base64.StdEncoding.Encode(buf, serverSignature)
+	return buf
+}
@@ -1425,6 +1425,8 @@ func (c *Conn) rxAuthenticationX(msg *pgproto3.Authentication) (err error) {
 	case pgproto3.AuthTypeMD5Password:
 		digestedPassword := "md5" + hexMD5(hexMD5(c.config.Password+c.config.User)+string(msg.Salt[:]))
 		err = c.txPasswordMessage(digestedPassword)
+	case pgproto3.AuthTypeSASL:
+		err = c.scramAuth(msg.SASLAuthMechanisms)
 	default:
 		err = errors.New("Received unknown authentication message")
 	}
@@ -212,6 +212,56 @@ func TestConnectWithMD5Password(t *testing.T) {
 	}
 }

+func TestConnectWithSCRAMPassword(t *testing.T) {
+	t.Parallel()
+
+	connString := os.Getenv("PGX_TEST_SCRAM_PASSWORD_CONN_STRING")
+	if connString == "" {
+		t.Skip("Skipping due to missing PGX_TEST_SCRAM_PASSWORD_CONN_STRING env var")
+	}
+
+	connConfig, err := pgx.ParseConnectionString(connString)
+	if err != nil {
+		t.Fatalf("Unable to parse config: %v", err)
+	}
+
+	conn, err := pgx.Connect(connConfig)
+	if err != nil {
+		t.Fatalf("Unable to establish connection: %v", err)
+	}
+
+	if _, present := conn.RuntimeParams["server_version"]; !present {
+		t.Error("Runtime parameters not stored")
+	}
+
+	if conn.PID() == 0 {
+		t.Error("Backend PID not stored")
+	}
+
+	var currentDB string
+	err = conn.QueryRow("select current_database()").Scan(&currentDB)
+	if err != nil {
+		t.Fatalf("QueryRow Scan unexpectedly failed: %v", err)
+	}
+	if currentDB != defaultConnConfig.Database {
+		t.Errorf("Did not connect to specified database (%v)", defaultConnConfig.Database)
+	}
+
+	var user string
+	err = conn.QueryRow("select current_user").Scan(&user)
+	if err != nil {
+		t.Fatalf("QueryRow Scan unexpectedly failed: %v", err)
+	}
+	if user != defaultConnConfig.User {
+		t.Errorf("Did not connect as specified user (%v)", defaultConnConfig.User)
+	}
+
+	err = conn.Close()
+	if err != nil {
+		t.Fatal("Unable to close connection")
+	}
+}
+
 func TestConnectWithTLSFallback(t *testing.T) {
 	t.Parallel()

@@ -1,6 +1,7 @@
 package pgproto3

 import (
+	"bytes"
 	"encoding/binary"

 	"github.com/jackc/pgx/pgio"
@@ -11,6 +12,9 @@ const (
 	AuthTypeOk                = 0
 	AuthTypeCleartextPassword = 3
 	AuthTypeMD5Password       = 5
+	AuthTypeSASL              = 10
+	AuthTypeSASLContinue      = 11
+	AuthTypeSASLFinal         = 12
 )

 type Authentication struct {
@@ -18,6 +22,12 @@ type Authentication struct {

 	// MD5Password fields
 	Salt [4]byte
+
+	// SASL fields
+	SASLAuthMechanisms []string
+
+	// SASLContinue and SASLFinal data
+	SASLData []byte
 }

 func (*Authentication) Backend() {}
@@ -30,6 +40,17 @@ func (dst *Authentication) Decode(src []byte) error {
 	case AuthTypeCleartextPassword:
 	case AuthTypeMD5Password:
 		copy(dst.Salt[:], src[4:8])
+	case AuthTypeSASL:
+		authMechanisms := src[4:]
+		for len(authMechanisms) > 1 {
+			idx := bytes.IndexByte(authMechanisms, 0)
+			if idx > 0 {
+				dst.SASLAuthMechanisms = append(dst.SASLAuthMechanisms, string(authMechanisms[:idx]))
+				authMechanisms = authMechanisms[idx+1:]
+			}
+		}
+	case AuthTypeSASLContinue, AuthTypeSASLFinal:
+		dst.SASLData = src[4:]
 	default:
 		return errors.Errorf("unknown authentication type: %d", dst.Type)
 	}
@@ -46,6 +67,15 @@ func (src *Authentication) Encode(dst []byte) []byte {
 	switch src.Type {
 	case AuthTypeMD5Password:
 		dst = append(dst, src.Salt[:]...)
+	case AuthTypeSASL:
+		for _, s := range src.SASLAuthMechanisms {
+			dst = append(dst, []byte(s)...)
+			dst = append(dst, 0)
+		}
+		dst = append(dst, 0)
+	case AuthTypeSASLContinue:
+		dst = pgio.AppendInt32(dst, int32(len(src.SASLData)))
+		dst = append(dst, src.SASLData...)
 	}

 	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
@@ -0,0 +1,64 @@
+package pgproto3
+
+import (
+	"bytes"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+
+	"github.com/jackc/pgx/pgio"
+)
+
+type SASLInitialResponse struct {
+	AuthMechanism string
+	Data          []byte
+}
+
+func (*SASLInitialResponse) Frontend() {}
+
+func (dst *SASLInitialResponse) Decode(src []byte) error {
+	*dst = SASLInitialResponse{}
+
+	rp := 0
+
+	idx := bytes.IndexByte(src, 0)
+	if idx < 0 {
+		return errors.New("invalid SASLInitialResponse")
+	}
+
+	dst.AuthMechanism = string(src[rp:idx])
+	rp = idx + 1
+
+	rp += 4 // The rest of the message is data so we can just skip the size
+	dst.Data = src[rp:]
+
+	return nil
+}
+
+func (src *SASLInitialResponse) Encode(dst []byte) []byte {
+	dst = append(dst, 'p')
+	sp := len(dst)
+	dst = pgio.AppendInt32(dst, -1)
+
+	dst = append(dst, []byte(src.AuthMechanism)...)
+	dst = append(dst, 0)
+
+	dst = pgio.AppendInt32(dst, int32(len(src.Data)))
+	dst = append(dst, src.Data...)
+
+	pgio.SetInt32(dst[sp:], int32(len(dst[sp:])))
+
+	return dst
+}
+
+func (src *SASLInitialResponse) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Type          string
+		AuthMechanism string
+		Data          string
+	}{
+		Type:          "SASLInitialResponse",
+		AuthMechanism: src.AuthMechanism,
+		Data:          hex.EncodeToString(src.Data),
+	})
+}
@@ -0,0 +1,38 @@
+package pgproto3
+
+import (
+	"encoding/hex"
+	"encoding/json"
+
+	"github.com/jackc/pgx/pgio"
+)
+
+type SASLResponse struct {
+	Data []byte
+}
+
+func (*SASLResponse) Frontend() {}
+
+func (dst *SASLResponse) Decode(src []byte) error {
+	*dst = SASLResponse{Data: src}
+	return nil
+}
+
+func (src *SASLResponse) Encode(dst []byte) []byte {
+	dst = append(dst, 'p')
+	dst = pgio.AppendInt32(dst, int32(4+len(src.Data)))
+
+	dst = append(dst, src.Data...)
+
+	return dst
+}
+
+func (src *SASLResponse) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Type string
+		Data string
+	}{
+		Type: "SASLResponse",
+		Data: hex.EncodeToString(src.Data),
+	})
+}