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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -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 | ||
| } |
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