Hi, (I hope this is the correct list to be asking this, apologies if not) I am trying to write an application which amongst other things uses the blowfish implementation (blowfish.h) to transport files over a simple server/client pair.
However, whilst some files are encrypted, transported, received and decrypted correctly, some end up being corrupted, after the final decryption stage. This leads me to think that the encryption routines are not being called correctly (since I have also tried with equivalent DES library calls, with the same 'intermittent corruption' results). The relevant code is pasted below and further mirrored at http://pastebin.com/d4d166d12. So it starts with the function send_file (called by a connected client). This splits the file into chunks. Each 1024 byte chunk is encrypted separately and then sent. Each chunk is then received by the server in the receive_file function, decrypted and saved to disc. Any idea what the problem could be? Cheers, Ben. inline void blowfish(unsigned char *data, int data_len, char* key, int enc) { BF_KEY bfkey; BF_set_key(&bfkey, strlen(key)+1, (const unsigned char*)key); unsigned char ivec[8]; memset(ivec, 0, 8); unsigned char *out = (unsigned char*) malloc(1024); bzero(out,1024); int num = 0; BF_cfb64_encrypt(data, out, data_len, &bfkey, ivec, &num, enc); memcpy(data, out, data_len); free(out); } void MyFrame::encryptHelper(const char* orig, int inlength) { char *pb=(char*)(std::string((passInput->GetValue()).mb_str()).c_str()); blowfish((unsigned char*)orig, inlength, pb, BF_ENCRYPT); } void MyFrame::decryptHelper(const char* orig, int inlength) { char *pb=(char*)(std::string((passInput->GetValue()).mb_str()).c_str()); blowfish((unsigned char*)orig, inlength, pb, BF_DECRYPT); } int MyFrame::send_file(int fd) { // Note file size and name of file which the receiver is expecting have been sent // in a function prior to the call of this one char rec[10]; struct stat stat_buf; fstat (fd, &stat_buf); int size=stat_buf.st_size; while(size > 0) { char buffer[1030]; bzero(buffer,1030); bzero(rec,10); int n; if(size>=1024) { n=read(fd, buffer, 1024); // encrypt is necessary if(encButtonOn->GetValue()) encryptHelper(buffer,1024); // Send a chunk of data n=send(sockFile_, buffer, 1024, 0 ); // Wait for an acknowledgement n = recv(sockFile_, rec, 10, 0 ); } else // reamining file bytes { n=read(fd, buffer, size); if(encButtonOn->GetValue()) encryptHelper(buffer,size); buffer[size]='\0'; n=send(sockFile_,buffer, size, 0 ); n=recv(sockFile_, rec, 10, 0 ); } } // Send a 'completion' string int n = send(sockFile_, "COMP",strlen("COMP"), 0 ); // Receive an acknowledgemnt char buf[10]; bzero(buf,10); n = recv(sockFile_, buf, 10, 0 ); return(0); } int MyFrame::receive_file() { // receive file size and send ack char sizeBuffer[50]; bzero(sizeBuffer,50); int n; n=read(sockFile_, sizeBuffer, 50); n=send(sockFile_,"OK", strlen("OK"), 0 ); int size = atoi(sizeBuffer); //std::cout<<size<<std::endl; // receive file name and send ack char saveName[256]; bzero(saveName,256); n=read(sockFile_, saveName, 256); n=send(sockFile_,"OK",strlen("OK"), 0 ); //std::cout<<saveName_<<std::endl; // start file writing process to local disk // decrypt first if necessary if(encButtonOn->GetValue()) decryptHelper(saveName,strlen(saveName)); ofstream outFile(saveName,ios::out|ios::binary|ios::app); while(size > 0) { // buffer for storing incoming data char buf[1030]; bzero(buf,1030); if(size>=1024) { // receive chunk of data n=recv(sockFile_, buf, 1024, 0 ); // decrypt if necessary if(encButtonOn->GetValue()) decryptHelper(buf,1024); // write chunk of data to disk outFile.write(buf,1024); // send acknowledgement n = send(sockFile_, "OK", strlen("OK"), 0 ); } else { n=recv(sockFile_, buf, size, 0 ); if(encButtonOn->GetValue()) decryptHelper(buf,size); buf[size]='\0'; outFile.write(buf,size); n = send(sockFile_, "OK", strlen("OK"), 0 ); } size -= 1024; } outFile.close(); // Receive 'COMP' and send acknowledgement // --------------------------------------- char buf[10]; bzero(buf,10); n = recv(sockFile_, buf, 10, 0 ); n = send(sockFile_, "OK", strlen("OK"), 0 ); std::cout<<"File received..."<<std::endl; return(0); }
