Usenet 1994 October/usenetsourcesnewsgroupsinfomagicoctober1994disk2.iso/misc/volume36/port-lpr/part03/unix-tcp.c

C/C++ Source or Header | 1993-03-11 | 5KB | 197 lines

/*
 * lpr interface for UNIX (i.e. BSD-ish) tcp
 */

#include "common.h"
#include <stdio.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pwd.h>
#include <netdb.h>
#include <sys/socket.h>
#include <errno.h>
#include <netinet/in.h>

#ifndef MAKE_EMAIL_ADDRESS
#define MAKE_EMAIL_ADDRESS(buf,user,dom) sprintf (buf, "%s@%s", user, dom)
#endif


struct hostent *
gethostbynameoraddr (hostname)
char *hostname;
{
    if (isdigit (*hostname)) {
    static struct hostent x;
    static char *alias_list[1];
    static unsigned long *addr_list[2];
    static unsigned long ip_address;

    ip_address = inet_addr (hostname);

    addr_list[0] = &ip_address;
    addr_list[1] = NULL;
    alias_list[0] = NULL;

    x.h_name = hostname;
    x.h_aliases = alias_list;
    x.h_addrtype = AF_INET;
    x.h_length = sizeof (unsigned long);
    x.h_addr_list = (char **) addr_list;
    return &x;
    }
    return gethostbyname (hostname);
}

void sysdep()
{
    struct passwd *pwd;
    char *p;
    struct hostent *hp;
    char *getenv ();

    gethostname (hostname, sizeof hostname);

    if (pwd = getpwuid (getuid ()))
    strcpy (username, pwd->pw_name);
    else {
    fprintf (stderr, "lpr: system problem: can't get your username!\n");
    exit (1);
    }
    endpwent ();

    hp = gethostbyname (hostname);
    MAKE_EMAIL_ADDRESS(email_address, username, hp ? hp->h_name : hostname);
}


/*
 * Allocate a socket and bind it to a local privileged port
 * We have to be running set-uid to root to do this.
 */

int
get_priv_tcp_socket ()
{
    int fd;
    int port;
    struct sockaddr_in s;

    if ((fd = socket (AF_INET, SOCK_STREAM, 0)) == EOF) {
    perror ("socket");
    return EOF;
    }
    for (port = IPPORT_RESERVED-1; port > IPPORT_RESERVED / 2; port--) {
    extern int errno;
    s.sin_family = AF_INET;
    s.sin_addr.s_addr = INADDR_ANY;
    s.sin_port = htons (port);
    if (bind (fd, (struct sockaddr *) &s, sizeof (s)) == 0)
        return fd;
    if (errno == EACCES) {
        fprintf (stderr, "lpr warning: bind: cannot bind to privileged port\n");
        return fd;
    }
    }
    close (fd);
    return EOF;
}

/*
 * Open a TCP connection to an lpd-server.
 * This requires that this program be run set-uid to root in order to be able
 * to bind a socket to a privileged port.
 */

int
open_lpd (server)
char *server;
{
    int fd;
    int i;
    int last_connect_failed;
    struct hostent *hp;
    struct servent *sp;
    struct sockaddr_in s;

    if (server == NULL || *server == '\0') {
    fprintf (stderr, "lpr: no server host was specified.\n");
    fprintf (stderr, "     Supply one with the -S option, or\n");
    fprintf (stderr, "     by setting the LPD_SERVER environment variable\n");
    return EOF;
    }
    if ((hp = gethostbynameoraddr (server)) == NULL) {
    fprintf (stderr, "lpr: can't find network address for %s\n",
         server);
    fflush (stderr);
    return EOF;
    }

    s.sin_family = AF_INET;
    if ((sp = getservbyname ("printer", "tcp")) == NULL)
    s.sin_port = htons (515);
    else
    s.sin_port = sp->s_port;

    /*
     * On some systems h_addr is a macro that is defined to be h_addr_list[0]
     * On other (ancient) systems, h_addr is a member of the hostent structure.
     * So if h_addr is defined as a macro, then we must have the list...
     */

#ifdef h_addr
    for (i = 0; hp->h_addr_list[i] ; ++i) {
    fd = get_priv_tcp_socket ();
    disable_special_privileges ();
    if (fd < 0)
        return EOF;
    bcopy (hp->h_addr_list[i], &s.sin_addr, sizeof (s.sin_addr));
    if (debug)
        fprintf (stderr, "Trying %s...", inet_ntoa (s.sin_addr));
    last_connect_failed = 0; /* "I'm ashamed of this." - SMK */
    if (connect (fd, &s, sizeof s) == 0) {
        if (debug)
        fprintf (stderr, "open\n");
        break;
    }
    else {
        close (fd);        /* reuse fd */
        if (debug)
        perror ("");
        last_connect_failed = 1;
    }
    }
    if (last_connect_failed) {
    perror ("connect");
    return EOF;
    }
#else
    fd = get_priv_tcp_socket ();
    disable_special_privileges ();
    if (fd < 0)
    return EOF;
    bcopy (hp->h_addr, (char *) &s.sin_addr, sizeof(s.sin_addr));
    if (connect (fd, &s, sizeof s) < 0) {
    perror ("connect");
    close (fd);
    return EOF;
    }
#endif

    max_net_read = max_net_write = 32767;
    return fd;
}

/*
 * Turn off set-uid privileges.
 * We have to be running set-uid to root in order to bind to a privileged
 * port.  In order to minimize the security risk, this function is called
 * from open_job() immediately after open_lpd() returns.
 */

disable_special_privileges ()
{
    setuid (getuid ());
}