runas.c

//## hyphop ##

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#define NAME "runas"

struct stat sb;


int main(int argc, char *argv[], char **envp) {

  int uid = 0;

  if (argc < 2) {
    fprintf(stderr, "USAGE: runasg [ progname ] [@args]\n");
    exit(1);
  }

  if (stat(argv[1], &sb) == 0 && sb.st_mode & S_IXUSR) {
    ;
  } else {

    fprintf(stderr, "[i] %s `%s` - is not exec - try: `%s $(which %s)`\n", NAME,
            argv[1], NAME, argv[1]);
    exit(1);
  }

  char *gs;
  char *us;

  int gid = 0;

  gs = getenv("GID");
  us = getenv("UID");

  if (us) {
    uid = atoi(us);
  }

  if (gs) {
    gid = atoi(gs);
  }

  setuid(uid);
  setgid(gid);

  fprintf(stderr, "%s UID: %d, GID: %d CMD: ", "runas", uid, gid);
  for (int i = 1; i < argc; i++) {
    fprintf(stderr, "%s ", argv[i]);
  }
  fprintf(stderr, "\n");

  argv++;
  execve(argv[0], argv, envp);
  perror("execve"); /* execve() returns only on error */
  exit(EXIT_FAILURE);
  return 0;
}