Refactor TLS record reading logic in probe.go to replace readOneTLSApplicationRecord with readNextTLS17Payload. The new function handles TLS 1.2-style records, improving error handling and skipping non-application data records. This change enhances the robustness of MTProxy decryption.

internal/tgquick/probe.go

@@ -154,7 +154,7 @@ func VerifyResPQ(ctx context.Context, conn net.Conn, enc, dec cipher.Stream, eeT
 		var chunk []byte
 		var rerr error
 		if eeTLS {
-			chunk, rerr = readOneTLSApplicationRecord(br)
+			chunk, rerr = readNextTLS17Payload(br)
 		} else {
 			chunk, rerr = readAtMost(conn, 65536)
 		}
@@ -193,23 +193,41 @@ func VerifyResPQ(ctx context.Context, conn net.Conn, enc, dec cipher.Stream, eeT
 	return ErrNoResPQ
 }
 
-func readOneTLSApplicationRecord(br *bufio.Reader) ([]byte, error) {
-	h := make([]byte, 5)
-	if _, err := io.ReadFull(br, h); err != nil {
-		return nil, err
+// readNextTLS17Payload reads TLS 1.2-style records from the wire (plaintext record headers).
+// Handshake (0x16) and ChangeCipherSpec (0x15) payloads are not MTProxy-CTR ciphertext — skip them.
+// Only application data (0x17) inner bytes are passed through the MTProxy decrypt stream (caller XORs).
+// Some proxies send extra handshake records after the fake ServerHello; clients skip them before MTProto.
+func readNextTLS17Payload(br *bufio.Reader) ([]byte, error) {
+	const maxSkips = 128
+	for range maxSkips {
+		h := make([]byte, 5)
+		if _, err := io.ReadFull(br, h); err != nil {
+			return nil, err
+		}
+		ver := binary.BigEndian.Uint16(h[1:3])
+		if ver != 0x0303 && ver != 0x0301 {
+			return nil, fmt.Errorf("unexpected tls record version 0x%04x (type 0x%02x); if type is 0x48 ('H') the peer may be speaking HTTP on this socket", ver, h[0])
+		}
+		n := int(binary.BigEndian.Uint16(h[3:5]))
+		if n <= 0 || n > 1<<20 {
+			return nil, fmt.Errorf("invalid tls record length %d", n)
+		}
+		payload := make([]byte, n)
+		if _, err := io.ReadFull(br, payload); err != nil {
+			return nil, err
+		}
+		switch h[0] {
+		case 0x17: // application data — inner bytes are MTProxy-obfuscated
+			return payload, nil
+		case 0x16, 0x15: // more handshake / CCS after ServerHello — plaintext, do not advance CTR interpretation here
+			continue
+		case 0x14: // alert
+			return nil, fmt.Errorf("tls alert record from proxy (len=%d)", n)
+		default:
+			return nil, fmt.Errorf("unexpected tls record type 0x%02x (len=%d); 0x48 often means cleartext HTTP if the stream is misaligned", h[0], n)
+		}
 	}
-	if h[0] != 0x17 {
-		return nil, fmt.Errorf("unexpected tls record type 0x%02x", h[0])
-	}
-	n := int(binary.BigEndian.Uint16(h[3:5]))
-	if n <= 0 || n > 1<<20 {
-		return nil, fmt.Errorf("invalid tls app length %d", n)
-	}
-	p := make([]byte, n)
-	if _, err := io.ReadFull(br, p); err != nil {
-		return nil, err
-	}
-	return p, nil
+	return nil, fmt.Errorf("too many non-application tls records before 0x17")
 }
 
 func readAtMost(conn net.Conn, max int) ([]byte, error) {