/**
  * Program to allow telnet access to a chrooted home directory.
  * (c) 1998 Semiotek Inc (Justin Wells). All rights reserved.
  *
  * Permission granted to use and redistribute freely, providing 
  * this notice remains intact. By using or distributing this software 
  * you agree that you are using the software at your own risk, and 
  * that Semiotek Inc. is absolved of any liability relating to harm that 
  * may come to you or your business as a result of using this software.
  *
  * USE: This program acts as the users shell according to the real 
  * password file. On login it chroots to the users home directory, 
  * then calls getpwent and grabs a new home directory and shell for
  * the user. It will chdir to this new directory, and exec the shell
  * it identifies. It will fail under a bunch of conditions that are 
  * either unexpected, or a sign that things are not working well.
  * Note that the getpwent after the chroot returns data from the 
  * /etc/passwd file in the chrooted partition.
  *
  * INSTALL: compile this program and install it setuid root. it must
  * be setuid root on most Unix systems in order to perform the chroot.
  * It will set uid back to the user before it execs their shell.
  *
  * BUGS: no log is written out, and the program is easily upset.
  * errors do go to stdout, but these messages are not always available
  * when debugging a problem. No independent security audit has been 
  * performed. In fact, the code had never even been read by anyone else.
  */

#include <unistd.h>
#include <sys/types.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv)
{

   char *home; 
   char *chroothome;
   int rc;
   uid_t uid = getuid();
   struct passwd *pw;

   /* i can't imagine why root would log in chrooted, so prevent it */
   if (0 == uid) {
      printf("FAILED: cannot run as root\n");
      exit(1);
   }

   FILE* log = fopen("/var/log/securelogin.log", "a");
   int i;
   fprintf(log, "uid %d: Args:", uid);
   for (i = 0; i < argc; i++) {
     fprintf(log," '%s'", argv[i]);
   }
   fprintf(log,"\n");
   fclose(log);

   /* get the password info */
   pw  = getpwuid(uid);  
   if (NULL == pw) {
      printf("FAILED: no such user id or cannot get passwd entry\n");
      exit(1);
   }

   /* switch to the secured area, and try to chroot */
   home = pw->pw_dir;
   if (NULL == home) {
      printf("FAILED: could not locate home area\n");
      exit(1);
   }

   if (chdir(home)) {
      printf("FAILED: could not to chdir before chroot to %s (does it exist?)\n", home);
      exit(2);
   }

   if (chroot(home)) {
      printf("FAILED: could not to chroot to %s (are we suid?)\n", home);
      exit(2);
   }

   /* get the inside chroot home */
   pw = getpwuid(uid);
   if (NULL == pw) {
      printf("FAILED: cannot get password info in chroot'd /etc/passwd\n");
      exit(1);
   }

   chroothome = pw->pw_dir;
   if (NULL == chroothome) {
      printf("FAILED: could not locate home area in chroot'd /etc/passwd\n");
      exit(1);
   }

   if (chdir(chroothome)) {
      printf("FAILED: could not to chdir inside chroot to %s (does it exist?)\n", home);
      exit(2);
   }

   /* printf("Root now %s\n", home); */

   /* revert to original user, or abort before we exec! */
   if (0 != setuid(uid)) {
      printf("FAILED: could not reset uid\n");
      exit(3);
   }

   /* read their real home from the password file in the secure area */
   home = NULL;
   pw  = getpwuid(uid);  
   if (NULL == pw) {
      printf("WARNING: password data not available in secure section\n");
   } else {
      home = pw->pw_dir;
   }
   if (NULL == home)
   {
      printf("WARNING: could not locate home directory\n");
   } else {
      if (chdir(home)) {
         printf("WARNING: could not change to home directory\n");
      }
   }


   /* fix the environment */
   setenv("HOME", home, 1);
   setenv("PATH", "/bin:/usr/bin:/usr/local/bin", 1);
   setenv("LD_LIBRARY_PATH", "/usr/lib:/usr/local/lib", 1);
   setenv("SHELL", "/bin/sh", 1);

   /* build argument array to exec cmds
   int j;
   char *nargv[argc+2];
   nargv[0]="-sh";
   nargv[1]="-c";
   for (j=0; j<argc; j++) { nargv[j+2]=argv[j]; }
   */

   /* DEBUG
   printf("argv1: %s\n", argv[1]);
   printf("argv2: %s\n", argv[2]);
   printf("argv3: %s\n", argv[3]); 
   */

   /* start a shell */
   /* rc = execlp("/bin/sh", "-sh", "-c", argv[2], NULL);  */

   argv[0]="-sh";
   rc = execvp("/bin/sh", argv);

   /* printf("%i\n",rc); */

   printf("FAILED: could not start shell\n");
   exit(4); 

}