CODEWITHSUNDEEP
javaiossocketssafariwebsocket
Matt MacLean
Matt MacLean

Reputation: 19648

Safari 5 / iOS, WebSocket handshake only works sometimes

I have made a class in java that allows me to wrap an existing socket with the WebSocket protocols. I have everything working for the RFC6445 protocol working and everything works in chrome and FF. However Safari and iOS is using the hixie76 / HyBi00 protocol (according to Wikipedia).

I have everything working and Safari and iOS correctly handshake and start sending/receiving messages... well, at least most of the time.

About 20-30% of the time, the handshake fails and Safari closes the connection. (Java reads a -1 byte upon trying to read first frame). Safari does not report any errors in the console, but just calls the onclose event handler.

Why would the handshakes only work part of the time?

Here is my handshake code:

Note: No exceptions are thrown and the "Handshake Complete" is written to the console. But then upon trying to read the first frame the connection is closed. (Java returns -1 on inst.read())

// Headers are read in a previous method which wraps the socket using RFC6445
// protocol. If it detects 2 keys it will call this and pass in the headers.
public static MessagingWebSocket wrapOldProtocol(HashMap<String, String> headers, PushbackInputStream pin, Socket sock) throws IOException, NoSuchAlgorithmException {
    // SPEC
    // https://datatracker.ietf.org/doc/html/draft-hixie-thewebsocketprotocol-76#page-32
    
    // Read the "key3" value. This is 8 random bytes after the headers.
    byte[] key3 = new byte[8];
    for ( int i=0; i<key3.length; i++ ) {
        key3[i] = (byte)pin.read();
    }
    
    // Grab the two keys we need to use for the handshake
    String key1 = headers.get("Sec-WebSocket-Key1");
    String key2 = headers.get("Sec-WebSocket-Key2");
    
    // Count the spaces in both keys
    // Abort the connection is either key has 0 spaces
    int spaces1 = StringUtils.countMatches(key1, " ");
    int spaces2 = StringUtils.countMatches(key2, " ");
    if ( spaces1 == 0 || spaces2 == 0 ) {
        throw new IOException("Bad Handshake Request, Possible Cross-protocol attack");
    }
    
    // Strip all non-digit characters from each key
    // Use the remaining value as a base-10 integer.
    // Abort if either number is not a multiple of it's #spaces counterpart
    // Need to use long because the values are unsigned
    long num1 = Long.parseLong( key1.replaceAll("\\D", "") );
    long num2 = Long.parseLong( key2.replaceAll("\\D", "") );
    if ( !(num1 % spaces1 == 0) || !(num2 % spaces2 == 0) ) {
        throw new IOException("Bad Handshake Request. Possible non-conforming client");
    }

    // Part1/2 is key num divided by the # of spaces
    int part1 = (int)(num1 / spaces1);
    int part2 = (int)(num2 / spaces2);
    
    // Now calculate the challenge response
    // MD5( num1 + num2 + key3 )  ... concat, not add
    MessageDigest md = MessageDigest.getInstance("MD5");
    md.update(ByteBuffer.allocate(4).putInt(part1));
    md.update(ByteBuffer.allocate(4).putInt(part2));
    md.update(key3);
    byte[] response = md.digest();
    
    // Now build the server handshake response
    // Ignore Sec-WebSocket-Protocol (we don't use this)
    String origin = headers.get("Origin");
    String location = "ws://" + headers.get("Host") + "/";
    
    StringBuilder sb = new StringBuilder();
    sb.append("HTTP/1.1 101 WebSocket Protocol Handshake").append("\r\n");
    sb.append("Upgrade: websocket").append("\r\n");
    sb.append("Connection: Upgrade").append("\r\n");
    sb.append("Sec-WebSocket-Origin: ").append(origin).append("\r\n");
    sb.append("Sec-WebSocket-Location: ").append(location).append("\r\n");
    sb.append("\r\n");
    
    // Anything left in the buffer?
    if ( pin.available() > 0 ) {
        throw new IOException("Unexpected bytes after handshake!");
    }
    
    // Send the handshake & challenge response
    OutputStream out = sock.getOutputStream();
    out.write(sb.toString().getBytes());
    out.write(response);
    out.flush();
    
    System.out.println("[MessagingWebSocket] Handshake Complete.");
    
    // Return the wrapper socket class.
    MessagingWebSocket ws = new MessagingWebSocket(sock);
    ws.oldProtocol = true;
    return ws;
}

Thanks!

Note: I am not looking for third-party alternatives for WebSockets such at jWebSocket, Jetty and Socket.IO. I already know about many of these.

Upvotes: 1

Views: 1283

Answers (1)

Liu Hao
Liu Hao

Reputation: 36

Your MD5 digest method has a bug: protocol described as below: https://datatracker.ietf.org/doc/html/draft-hixie-thewebsocketprotocol-76#section-5.2

byte[] bytes = new byte[16];    
BytesUtil.fillBytesWithArray(bytes, 0, 3, BytesUtil.intTobyteArray(part1));
BytesUtil.fillBytesWithArray(bytes, 4, 7, BytesUtil.intTobyteArray(part2));
BytesUtil.fillBytesWithArray(bytes, 8, 15, key3);

I think your problem is caused by Little Endian and Big Endian.

Upvotes: 1

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