Initial commit

vendor/github.com/jackc/pgconn/auth_scram.go

@@ -0,0 +1,266 @@
+// 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 pgconn
+
+import (
+	"bytes"
+	"crypto/hmac"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strconv"
+
+	"github.com/jackc/pgproto3/v2"
+	"golang.org/x/crypto/pbkdf2"
+	"golang.org/x/text/secure/precis"
+)
+
+const clientNonceLen = 18
+
+// Perform SCRAM authentication.
+func (c *PgConn) 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.
+	saslContinue, err := c.rxSASLContinue()
+	if err != nil {
+		return err
+	}
+	err = sc.recvServerFirstMessage(saslContinue.Data)
+	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.
+	saslFinal, err := c.rxSASLFinal()
+	if err != nil {
+		return err
+	}
+	return sc.recvServerFinalMessage(saslFinal.Data)
+}
+
+func (c *PgConn) rxSASLContinue() (*pgproto3.AuthenticationSASLContinue, error) {
+	msg, err := c.receiveMessage()
+	if err != nil {
+		return nil, err
+	}
+	saslContinue, ok := msg.(*pgproto3.AuthenticationSASLContinue)
+	if ok {
+		return saslContinue, nil
+	}
+
+	return nil, errors.New("expected AuthenticationSASLContinue message but received unexpected message")
+}
+
+func (c *PgConn) rxSASLFinal() (*pgproto3.AuthenticationSASLFinal, error) {
+	msg, err := c.receiveMessage()
+	if err != nil {
+		return nil, err
+	}
+	saslFinal, ok := msg.(*pgproto3.AuthenticationSASLFinal)
+	if ok {
+		return saslFinal, nil
+	}
+
+	return nil, errors.New("expected AuthenticationSASLFinal message but received unexpected message")
+}
+
+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: %w", err)
+	}
+
+	sc.iterations, err = strconv.Atoi(string(iterationsStr))
+	if err != nil || sc.iterations <= 0 {
+		return fmt.Errorf("invalid SCRAM iteration count received from server: %w", err)
+	}
+
+	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
+}