SRL Archive - C/C++ Help and Tutorials

Run `gcc -g3 test.c aes256.c -o test`.

It's pretty simple. You give it whether you wish to listen or send, a host, a port, and a key. If you're running two instances on the same computer, one instance must be told it is sending only; if they're run on different computers starting the program in listen mode will cause the connection to be bi-directional.

./test l localhost 1337 "This is a key."

./test s localhost 1337 "This is a key."

Main program is here in case you didn't want to download a file.
EDIT: Oh, yeah. The aes256 library isn't mine, but I forgot where I got it. It was on my desktop.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <errno.h>

#include <sys/socket.h>
#include <unistd.h>
#include <fcntl.h>
#include <netdb.h>

#include "aes256.h"
#include "isaac.h"

#define PSIZE 256

void cleanup();
void sig_hndl(int sig);

int sockfd;
struct addrinfo *host;
aes256_ctx aes;

int main(int argc, char *argv[])
{
    atexit(cleanup);
    signal(2, sig_hndl);

    if(getaddrinfo(argv[2], argv[3], NULL, &host))
    { puts("FATAL: Error resolving host.");
      puts("Usage: [l|s] [host] [port] [key]"); exit(0); }

    if((sockfd = socket(PF_INET, SOCK_DGRAM, 0)) == -1)
    { puts("FATAL: Error creating socket."); exit(0); }

    //int on = 1;
    //if((setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(int))) < 0)
    //{ puts("FATAL: Error setting socket options (1)."); exit(0); }

    if((fcntl(sockfd, F_SETFD, O_NONBLOCK)) < 0)
    { puts("FATAL: Error setting socket options (2)."); exit(0); }

    struct sockaddr_in any;
    any.sin_family = AF_INET;
    any.sin_addr.s_addr = htonl(INADDR_ANY);
    any.sin_port = htons(atoi(argv[3]));
    memset(any.sin_zero, 0, sizeof(any.sin_zero));

    if(*argv[1] == 'l')
        if((bind(sockfd, (struct sockaddr *)&any, sizeof(any))) < 0)
        { puts("FATAL: Error binding socket."); exit(0); }

	aes256_init(&aes, argv[4]);

    fd_set infd;
    FD_ZERO(&infd);
    FD_SET(0, &infd);
    FD_SET(sockfd, &infd);

    while(1)
    {
        int rlen;
        char buf[PSIZE + 1];
        memset(buf, 0, PSIZE);

        if((select(sockfd + 1, &infd, NULL, NULL, NULL)) < 0)
        { puts("Error in select()."); }

        if(FD_ISSET(0, &infd))
        {
            rlen = read(0, buf, PSIZE);

            int i, flen = ((rlen - 1) / 16 + 1);
            for(i = 0; i < flen; i++)
                aes256_encrypt(&aes, &buf[i * 16]);

            if((sendto(sockfd, buf, PSIZE, 0, host->ai_addr, host->ai_addrlen)) < 0)
            { puts("Error sending to remote host."); }
        }

        if(FD_ISSET(sockfd, &infd))
        {
            if((rlen = recvfrom(sockfd, buf, PSIZE, 0, host->ai_addr, &host->ai_addrlen)) < 0)
            { puts("Error receiving from remote host."); }

            //printf("%d:%s", rlen, buf);

            int i, flen = ((rlen - 1) / 16 + 1);
            for(i = 0; i < flen; i++)
                aes256_decrypt(&aes, &buf[i * 16]);

            printf("%s", buf);
        }
    }

	cleanup();
}

void sig_hndl(int sig)
{
    puts("");
    exit(0);
}

void cleanup()
{
    aes256_done(&aes);
    close(sockfd);
    freeaddrinfo(host);

    exit(0);
}