Miscellanous tidying and security fixes. Lots of thanks due to Clive

[shells] / banned.c

/* -*-c-*-
 *
 * $Id: banned.c,v 1.2 1999/04/21 09:07:55 mdw Exp $
 *
 * Ban a user from logging in
 *
 * (c) 1999 Mark Wooding
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: banned.c,v $
 * Revision 1.2  1999/04/21 09:07:55  mdw
 * Fiddle with copyright messages so that they're correct.
 *
 * Revision 1.1.1.1  1999/04/20 00:19:04  mdw
 * Initial versions.
 *
 */

/*----- Header files ------------------------------------------------------*/

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <pwd.h>
#include <unistd.h>
#include <fcntl.h>
#include <syslog.h>

/*----- Main code ---------------------------------------------------------*/

static const char *quis = "banned";

int main(int argc, char *argv[])
{
  struct passwd *pw;
  int fd;
  char buf[BUFSIZ];
  int r;

  /* --- Resolve the program name --- */

  {
    char *p, *q;
    p = argv[0];
    for (q = argv[0]; *q; q++) {
      if (*q == '/')
	p = q + 1;
    }
    quis = p;
  }

  /* --- Read the user's name --- */

  pw = getpwuid(getuid());
  if (!pw) {
    fprintf(stderr, "%s: you don't exist.  Go away.\n", quis);
    exit(EXIT_FAILURE);
  }

  /* --- Open the log file --- */

  openlog(quis, 0, LOG_AUTH);
  syslog(LOG_CRIT, "banned user `%s' attempted to log in", pw->pw_name);

  /* --- Change directory to the user's home --- */

  if (chdir(pw->pw_dir) < 0) {
    fprintf(stderr, "%s: couldn't change directory: %s\n",
	    quis, strerror(errno));
    exit(EXIT_FAILURE);
  }

  /* --- Open the reason file --- */

  if ((fd = open(".banned", O_RDONLY)) < 0) {
    fprintf(stderr, "%s: couldn't open `.banned' file: %s\n",
	    quis, strerror(errno));
    exit(EXIT_FAILURE);
  }

  /* --- Dump the reason information out --- */

  for (;;) {
    r = read(fd, buf, sizeof(buf));
    if (r == 0)
      break;
    else if (r < 0) {
      fprintf(stderr, "%s: couldn't read: %s\n", quis, strerror(errno));
      exit(EXIT_FAILURE);
    }
    write(STDOUT_FILENO, buf, r);
  }

  /* --- Done --- */

  close(fd);
  return (EXIT_FAILURE);
}

/*----- That's all, folks -------------------------------------------------*/