/**************************************************************/
/* naughty.c 1.0.0 (1999-Sep-18-Sat)                          */
/* Adam M. Costello <amc@cs.berkeley.edu>                     */
/*                                                            */
/* naughty [ -n <increment> ] <command> [<arg>]...            */
/*                                                            */
/* Opposite of nice.  This command is just like the nice      */
/* command, except that it doesn't support the obsolete       */
/* -increment option, and the default increment is negative   */
/* instead of positive (meaning the command will get more     */
/* CPU).                                                      */
/*                                                            */
/* This command is intended to be setuid root.  After it sets */
/* the priority, it gives up its root priviledges, becoming   */
/* the original user again.  This command should probably not */
/* be executable by everyone, but only by a particular group, */
/* perhaps group "naughty".                                   */
/**************************************************************/

/* This is ANSI C plus Single UNIX v2 code */


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

#include <sys/resource.h>
#include <sys/types.h>
#include <unistd.h>


/* Single UNIX v2 says NZERO should be defined */
/* by sys/resource.h, but in case it's not...  */

#ifndef NZERO
#define NZERO 20
#endif


static void usage(const char *progname)
{
  fprintf(stderr,
          "usage:\n"
          "%s [ -n <increment> ] command [<arg>]...\n",
          progname);
  exit(EXIT_FAILURE);
}


int main(int argc, char **argv)
{
  int current, increment = -(NZERO / 2), r;
  char * const *execargs = argv + 1;
  const char *progname = argv[0];
  uid_t uid;

  errno = 0;
  current = getpriority(PRIO_PROCESS,0);

  if (errno != 0) {
    perror("getpriority(PRIO_PROCESS,0)");
    return EXIT_FAILURE;
  }

  if (argc < 2) usage(progname);

  if (argv[1][0] == '-') {
    if (strcmp(argv[1], "-n"))
      usage(progname);
    else {
      if (argc < 4) usage(progname);
      increment = atoi(argv[2]);
      execargs = argv + 3;
    }
  }

  r = setpriority(PRIO_PROCESS, 0, current + increment);

  if (r == -1) {
    fprintf(stderr,
            "setpriority(PRIO_PROCESS, 0, %d + %d): %s\n",
            current, increment, strerror(errno));
  }

  uid = getuid();
  r = setuid(uid);

  if (r == -1) {
    fprintf(stderr,
            "setuid(%d): %s\n",
            (int) uid, strerror(errno));
    return EXIT_FAILURE;
  }

  execvp(execargs[0], execargs);

  fprintf(stderr, "execvp(%s, ...): %s\n", execargs[0], strerror(errno));
  return EXIT_FAILURE;
}