Add SCRAM authentication
This commit is contained in:
Jack Christensen
+255
@@ -0,0 +1,255 @@
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// SCRAM-SHA-256 authentication
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//
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// Resources:
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// https://tools.ietf.org/html/rfc5802
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// https://tools.ietf.org/html/rfc8265
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// https://www.postgresql.org/docs/current/sasl-authentication.html
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//
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// Inspiration drawn from other implementations:
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// https://github.com/lib/pq/pull/608
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// https://github.com/lib/pq/pull/788
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// https://github.com/lib/pq/pull/833
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package pgconn
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import (
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"bytes"
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"crypto/hmac"
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"crypto/rand"
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"crypto/sha256"
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"encoding/base64"
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"errors"
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"fmt"
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"strconv"
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"github.com/jackc/pgproto3"
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"golang.org/x/crypto/pbkdf2"
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"golang.org/x/text/secure/precis"
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)
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const clientNonceLen = 18
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// Perform SCRAM authentication.
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func (c *PgConn) scramAuth(serverAuthMechanisms []string) error {
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sc, err := newScramClient(serverAuthMechanisms, c.Config.Password)
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if err != nil {
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return err
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}
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// Send client-first-message in a SASLInitialResponse
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saslInitialResponse := &pgproto3.SASLInitialResponse{
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AuthMechanism: "SCRAM-SHA-256",
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Data: sc.clientFirstMessage(),
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}
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_, err = c.conn.Write(saslInitialResponse.Encode(nil))
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if err != nil {
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return err
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}
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// Receive server-first-message payload in a AuthenticationSASLContinue.
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authMsg, err := c.rxAuthMsg(pgproto3.AuthTypeSASLContinue)
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if err != nil {
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return err
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}
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err = sc.recvServerFirstMessage(authMsg.SASLData)
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if err != nil {
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return err
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}
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// Send client-final-message in a SASLResponse
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saslResponse := &pgproto3.SASLResponse{
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Data: []byte(sc.clientFinalMessage()),
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}
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_, err = c.conn.Write(saslResponse.Encode(nil))
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if err != nil {
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return err
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}
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// Receive server-final-message payload in a AuthenticationSASLFinal.
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authMsg, err = c.rxAuthMsg(pgproto3.AuthTypeSASLFinal)
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if err != nil {
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return err
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}
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return sc.recvServerFinalMessage(authMsg.SASLData)
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}
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func (c *PgConn) rxAuthMsg(typ uint32) (*pgproto3.Authentication, error) {
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msg, err := c.ReceiveMessage()
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if err != nil {
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return nil, err
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}
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authMsg, ok := msg.(*pgproto3.Authentication)
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if !ok {
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return nil, errors.New("unexpected message type")
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}
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if authMsg.Type != typ {
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return nil, errors.New("unexpected auth type")
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}
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return authMsg, nil
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}
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type scramClient struct {
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serverAuthMechanisms []string
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password []byte
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clientNonce []byte
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clientFirstMessageBare []byte
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serverFirstMessage []byte
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clientAndServerNonce []byte
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salt []byte
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iterations int
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saltedPassword []byte
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authMessage []byte
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}
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func newScramClient(serverAuthMechanisms []string, password string) (*scramClient, error) {
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sc := &scramClient{
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serverAuthMechanisms: serverAuthMechanisms,
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}
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// Ensure server supports SCRAM-SHA-256
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hasScramSHA256 := false
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for _, mech := range sc.serverAuthMechanisms {
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if mech == "SCRAM-SHA-256" {
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hasScramSHA256 = true
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break
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}
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}
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if !hasScramSHA256 {
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return nil, errors.New("server does not support SCRAM-SHA-256")
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}
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// precis.OpaqueString is equivalent to SASLprep for password.
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var err error
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sc.password, err = precis.OpaqueString.Bytes([]byte(password))
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if err != nil {
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// PostgreSQL allows passwords invalid according to SCRAM / SASLprep.
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sc.password = []byte(password)
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}
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buf := make([]byte, clientNonceLen)
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_, err = rand.Read(buf)
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if err != nil {
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return nil, err
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}
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sc.clientNonce = make([]byte, base64.RawStdEncoding.EncodedLen(len(buf)))
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base64.RawStdEncoding.Encode(sc.clientNonce, buf)
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return sc, nil
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}
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func (sc *scramClient) clientFirstMessage() []byte {
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sc.clientFirstMessageBare = []byte(fmt.Sprintf("n=,r=%s", sc.clientNonce))
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return []byte(fmt.Sprintf("n,,%s", sc.clientFirstMessageBare))
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}
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func (sc *scramClient) recvServerFirstMessage(serverFirstMessage []byte) error {
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sc.serverFirstMessage = serverFirstMessage
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buf := serverFirstMessage
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if !bytes.HasPrefix(buf, []byte("r=")) {
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return errors.New("invalid SCRAM server-first-message received from server: did not include r=")
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}
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buf = buf[2:]
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idx := bytes.IndexByte(buf, ',')
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if idx == -1 {
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return errors.New("invalid SCRAM server-first-message received from server: did not include s=")
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}
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sc.clientAndServerNonce = buf[:idx]
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buf = buf[idx+1:]
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if !bytes.HasPrefix(buf, []byte("s=")) {
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return errors.New("invalid SCRAM server-first-message received from server: did not include s=")
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}
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buf = buf[2:]
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idx = bytes.IndexByte(buf, ',')
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if idx == -1 {
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return errors.New("invalid SCRAM server-first-message received from server: did not include i=")
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}
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saltStr := buf[:idx]
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buf = buf[idx+1:]
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if !bytes.HasPrefix(buf, []byte("i=")) {
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return errors.New("invalid SCRAM server-first-message received from server: did not include i=")
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}
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buf = buf[2:]
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iterationsStr := buf
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var err error
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sc.salt, err = base64.StdEncoding.DecodeString(string(saltStr))
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if err != nil {
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return fmt.Errorf("invalid SCRAM salt received from server: %v", err)
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}
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sc.iterations, err = strconv.Atoi(string(iterationsStr))
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if err != nil || sc.iterations <= 0 {
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return fmt.Errorf("invalid SCRAM iteration count received from server: %s", iterationsStr)
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}
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if !bytes.HasPrefix(sc.clientAndServerNonce, sc.clientNonce) {
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return errors.New("invalid SCRAM nonce: did not start with client nonce")
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}
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if len(sc.clientAndServerNonce) <= len(sc.clientNonce) {
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return errors.New("invalid SCRAM nonce: did not include server nonce")
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}
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return nil
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}
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func (sc *scramClient) clientFinalMessage() string {
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clientFinalMessageWithoutProof := []byte(fmt.Sprintf("c=biws,r=%s", sc.clientAndServerNonce))
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sc.saltedPassword = pbkdf2.Key([]byte(sc.password), sc.salt, sc.iterations, 32, sha256.New)
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sc.authMessage = bytes.Join([][]byte{sc.clientFirstMessageBare, sc.serverFirstMessage, clientFinalMessageWithoutProof}, []byte(","))
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clientProof := computeClientProof(sc.saltedPassword, sc.authMessage)
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return fmt.Sprintf("%s,p=%s", clientFinalMessageWithoutProof, clientProof)
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}
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func (sc *scramClient) recvServerFinalMessage(serverFinalMessage []byte) error {
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if !bytes.HasPrefix(serverFinalMessage, []byte("v=")) {
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return errors.New("invalid SCRAM server-final-message received from server")
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}
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serverSignature := serverFinalMessage[2:]
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if !hmac.Equal(serverSignature, computeServerSignature(sc.saltedPassword, sc.authMessage)) {
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return errors.New("invalid SCRAM ServerSignature received from server")
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}
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return nil
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}
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func computeHMAC(key, msg []byte) []byte {
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mac := hmac.New(sha256.New, key)
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mac.Write(msg)
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return mac.Sum(nil)
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}
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func computeClientProof(saltedPassword, authMessage []byte) []byte {
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clientKey := computeHMAC(saltedPassword, []byte("Client Key"))
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storedKey := sha256.Sum256(clientKey)
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clientSignature := computeHMAC(storedKey[:], authMessage)
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clientProof := make([]byte, len(clientSignature))
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for i := 0; i < len(clientSignature); i++ {
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clientProof[i] = clientKey[i] ^ clientSignature[i]
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}
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buf := make([]byte, base64.StdEncoding.EncodedLen(len(clientProof)))
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base64.StdEncoding.Encode(buf, clientProof)
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return buf
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}
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func computeServerSignature(saltedPassword []byte, authMessage []byte) []byte {
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serverKey := computeHMAC(saltedPassword, []byte("Server Key"))
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serverSignature := computeHMAC(serverKey[:], authMessage)
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buf := make([]byte, base64.StdEncoding.EncodedLen(len(serverSignature)))
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base64.StdEncoding.Encode(buf, serverSignature)
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return buf
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}
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@@ -5,7 +5,9 @@ go 1.12
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require (
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github.com/jackc/pgio v1.0.0
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github.com/jackc/pgpassfile v1.0.0
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github.com/jackc/pgproto3 v1.0.0
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github.com/jackc/pgproto3 v1.1.0
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github.com/pkg/errors v0.8.1
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github.com/stretchr/testify v1.3.0
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golang.org/x/crypto v0.0.0-20190411191339-88737f569e3a
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golang.org/x/text v0.3.0
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)
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@@ -6,10 +6,8 @@ github.com/jackc/pgio v1.0.0 h1:g12B9UwVnzGhueNavwioyEEpAmqMe1E/BN9ES+8ovkE=
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github.com/jackc/pgio v1.0.0/go.mod h1:oP+2QK2wFfUWgr+gxjoBH9KGBb31Eio69xUb0w5bYf8=
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github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
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github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
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github.com/jackc/pgproto3 v0.0.0-20190330174656-bb06e6b3ff87 h1:xueDi0R+HxuFmuOA1xyFbbF+2LSXqWQJZSPWmmMFB0A=
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github.com/jackc/pgproto3 v0.0.0-20190330174656-bb06e6b3ff87/go.mod h1:eR5FA3leWg7p9aeAqi37XOTgTIbkABlvcPB3E5rlc78=
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github.com/jackc/pgproto3 v1.0.0 h1:25tUmlES7eyD96oYaUHc1dLOFbgcJtFzCdnOOoqmA1I=
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github.com/jackc/pgproto3 v1.0.0/go.mod h1:eR5FA3leWg7p9aeAqi37XOTgTIbkABlvcPB3E5rlc78=
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github.com/jackc/pgproto3 v1.1.0 h1:FYYE4yRw+AgI8wXIinMlNjBbp/UitDJwfj5LqqewP1A=
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github.com/jackc/pgproto3 v1.1.0/go.mod h1:eR5FA3leWg7p9aeAqi37XOTgTIbkABlvcPB3E5rlc78=
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github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
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github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
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github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
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@@ -17,3 +15,8 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
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github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
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github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
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github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
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golang.org/x/crypto v0.0.0-20190411191339-88737f569e3a h1:Igim7XhdOpBnWPuYJ70XcNpq8q3BCACtVgNfoJxOV7g=
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golang.org/x/crypto v0.0.0-20190411191339-88737f569e3a/go.mod h1:WFFai1msRO1wXaEeE5yQxYXgSfI8pQAWXbQop6sCtWE=
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golang.org/x/sys v0.0.0-20190403152447-81d4e9dc473e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
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golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
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golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
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@@ -260,6 +260,8 @@ func (c *PgConn) rxAuthenticationX(msg *pgproto3.Authentication) (err error) {
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case pgproto3.AuthTypeMD5Password:
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digestedPassword := "md5" + hexMD5(hexMD5(c.Config.Password+c.Config.User)+string(msg.Salt[:]))
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err = c.txPasswordMessage(digestedPassword)
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case pgproto3.AuthTypeSASL:
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err = c.scramAuth(msg.SASLAuthMechanisms)
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default:
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err = errors.New("Received unknown authentication message")
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}
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+1
-2
@@ -33,12 +33,11 @@ func TestConnect(t *testing.T) {
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{"TCP", "PGX_TEST_TCP_CONN_STRING"},
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{"Plain password", "PGX_TEST_PLAIN_PASSWORD_CONN_STRING"},
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{"MD5 password", "PGX_TEST_MD5_PASSWORD_CONN_STRING"},
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{"SCRAM password", "PGX_TEST_SCRAM_PASSWORD_CONN_STRING"},
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}
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for _, tt := range tests {
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t.Run(tt.name, func(t *testing.T) {
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t.Parallel()
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connString := os.Getenv(tt.env)
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if connString == "" {
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t.Skipf("Skipping due to missing environment variable %v", tt.env)
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