C++ Socket retrieve and send encrypted Data - c++

Question

I got a small problem.. Currently im writing a small tool which connects to a Server, downloads some blowfish encrypted Data into a char Array (char buffer[512]) and saves that Array into a file (fstream ios::binary).
Then later i reopen that file (ifstream ios::binary) and send it back. This time i read it into a std::string and not a char[].
My Problem now is that the Data is corrupted after i send them back.
What would be the best way to acomblish this? Is it safe to use char[] and std::string? Or does that somehow corrupt the data? (i guess so).
If you need some code examples i can provide them.
Thanks!
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Okay a quick update to give you more details.
Im writing a Tool for a game (on OS X), its seperated in two parts:
Retrieve the encrypted Data from Game Servers and save them.
Send the saved encrypted Data back to the local Game
Problem: When the saved Data arrives the local Game, the Game just spits out that the Data cant be decrypted => data corruption.
Here's the code for 1. (Its just poc for selftesting purpose):
mode == 0 => no gameDataChunk there
mode == 1 => gameDataChunk there, need to write
mode == 2 => keyFrame there
*/
std::string socketRead(int socket, int mode, std::string num_chunk, std::string num_key, std::string game_id){
std::string response = "";
char buffer[512];
int bytes;
while((bytes = read(socket, buffer, 511)) > 0){
std::string temp(buffer, bytes);
//std::cout << temp;
response = response + temp;
if(!(temp.find("HTTP/1.1 200")<1800000)){
if(temp.find("HTTP/1.1")<1800000){
std::cout << std::endl << std::endl << "GOT NOT A 200 !!!" << std::endl << std::endl;
std::cout << temp << std::endl << std::endl;
return "EXIT";
}
}
if(mode == 1){
if(temp.find("\r\n\r\n")<1800000){
write_gameDataChunk(buffer, 1, temp.find("\r\n\r\n")+4, num_chunk, game_id);
}
else{
write_gameDataChunk(buffer, 0, 0, num_chunk, game_id);
}
}
else if(mode == 2){
if(temp.find("\r\n\r\n")<1800000){
write_keyFrame(buffer, 1, temp.find("\r\n\r\n")+4, num_key, game_id);
}
else{
write_keyFrame(buffer, 0,0, num_key, game_id);
}
}
bzero(buffer, 512);
}
return response;
}
void write_gameDataChunk(char buffer[], int mode, int index, std::string num, std::string game_id){
std::fstream write;
char local_buffer[512];
if(mode == 0){
//complete bin data
write.open("/tmp/" + game_id + "/" + num + "/game_dataChunk.bin", std::ios::out | std::ios::binary | std::ios::app);
write << buffer;
}
else if(mode == 1){
//partial bin data
std::string command = "mkdir /tmp/" + game_id + "/" + num;
std::system(command.c_str());
write.open("/tmp/" + game_id + "/" + num + "/game_dataChunk.bin", std::ios::out | std::ios::binary);
strcpy(local_buffer, buffer+index);
write << local_buffer;
}
write.close();
}
Here is the code for 2.:
std::string get_DataChunk(std::string game_id, int chunkId){
std::ifstream read;
std::string dummy;
std::string command;
std::string result = "";
command = "/tmp/" + game_id + "/" + std::to_string(chunkId) + "/game_dataChunk.bin";
read.open(command.c_str(), std::ios::in | std::ios::binary);
while(getline(read,dummy)){
result = result + dummy;
}
read.close();
return result;
}
This is all testing code for myself and not finished, so its kinda ugly... but i hope you will understand what i mean. I did not often had to deal with binary Data send over Sockets..

Answer 1

std::string is not meant to deal with binary. It is meant to deal with strings.
What you want is a std::vector<char> which doesn't care about what values you are storing.

Answer 2

Any '\0' in your binary data will stop construct the std::string. So the std::string().size() only count to the character before 1st '\0'. Use std::vector<unsigned char> instead.
By the way, what does 1800000 mean? I know that HTTP/1.1 200 is the characters you received at the earliest.(poor english)