use precise mask to fix bug for part parse lead frame message error

[gubaojian]

use precise mask to fix bug for part parse lead frame message error.
here is the test code, you can use the code and the data in zip file to Reproduce the bug :
one_frame.dat.zip

`

int main() {
   std::string framedata =   FileUtils::readFile("/Users/baojian/code/ServerTechTest/jwt/cplus/MaskTest/CopyTest/one_frame.dat", true);

std::string two;
two.append(framedata);
two.append(framedata);

uWS::WebSocketProtocol<true, Impl> protocol;
uWS::WebSocketState<true> state;

char* src = (char*)framedata.data();


//part parse
protocol.consume(src, 20, &state, nullptr);
protocol.consume(src + 20, 20, &state, nullptr);
protocol.consume(src + 40, framedata.size() - 40, &state, nullptr);


//parse two message
protocol.consume(two.data(), two.size(), &state, nullptr);

}

`

[gubaojian]

`

     unmaskImprecise8<0>(src + MESSAGE_HEADER, mask, length); 

    unmaskInplace(src, src + ((length >> 2) + 1) * 4, wState->mask);

`
above the line code may lead to overflow visit of the src buffer.

[uNetworkingAB]

std::string two;
two.append(framedata);
two.append(framedata);

You need to pre-pad, post-pad your buffer with at least 32 bytes. All parsers in uWS build on relaxed boundary cehcks due to how all buffers are pre and post padded.

[gubaojian]

std::string two; two.append(framedata); two.append(framedata);

You need to pre-pad, post-pad your buffer with at least 32 bytes. All parsers in uWS build on relaxed boundary cehcks due to how all buffers are pre and post padded.

thanks for your reply, seems it works well