mdw@git.distorted.org.uk Git - shells/blob - chrootsh.c

   1 /* -*-c-*-
   2  *
   3  * $Id: chrootsh.c,v 1.1 1999/04/20 00:19:04 mdw Exp $
   4  *
   5  * Chroot gaol shell
   6  *
   7  * (c) 1999 EBI
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Chroot shell.
  13  *
  14  * chrootsh is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU General Public License as published by
  16  * the Free Software Foundation; either version 2 of the License, or
  17  * (at your option) any later version.
  18  *
  19  * chrootsh is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with chrootsh; if not, write to the Free Software Foundation,
  26  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  27  */
  28
  29 /*----- Revision history --------------------------------------------------*
  30  *
  31  * $Log: chrootsh.c,v $
  32  * Revision 1.1  1999/04/20 00:19:04  mdw
  33  * Initial revision
  34  *
  35  */
  36
  37 /*----- Header files ------------------------------------------------------*/
  38
  39 #include <errno.h>
  40 #include <stdio.h>
  41 #include <stdlib.h>
  42 #include <string.h>
  43
  44 #include <sys/types.h>
  45 #include <unistd.h>
  46 #include <pwd.h>
  47
  48 extern char **environ;
  49
  50 /*----- Main code ---------------------------------------------------------*/
  51
  52 #ifndef CHROOTSH_PATH
  53 #  define CHROOTSH_PATH "/usr/bin/chrootsh"
  54 #endif
  55
  56 static const char *quis = "chrootsh";
  57
  58 static void *xmalloc(size_t sz)
  59 {
  60   void *p = malloc(sz);
  61   if (!p) {
  62     fprintf(stderr, "%s: not enough memory\n", quis);
  63     exit(EXIT_FAILURE);
  64   }
  65   return (p);
  66 }
  67
  68 static char *xstrdup(const char *p)
  69 {
  70   size_t sz = strlen(p) + 1;
  71   char *q = xmalloc(sz);
  72   memcpy(q, p, sz);
  73   return (q);
  74 }
  75
  76 int main(int argc, char *argv[])
  77 {
  78   struct passwd *pw;
  79   uid_t me = getuid();
  80   char **env;
  81   char **av;
  82
  83   /* --- Resolve the program name --- */
  84
  85   {
  86     char *p, *q;
  87     p = argv[0];
  88     for (q = argv[0]; *q; q++) {
  89       if (*q == '/')
  90         p = q + 1;
  91     }
  92     quis = p;
  93   }
  94
  95   /* --- Check the user is meant to be chrooted --- */
  96
  97   pw = getpwuid(me);
  98   if (!pw) {
  99     fprintf(stderr, "%s: you don't exist.  Go away.\n", quis);
 100     exit(EXIT_FAILURE);
 101   }
 102   if (strcmp(pw->pw_shell, CHROOTSH_PATH) != 0) {
 103     fprintf(stderr, "%s: you aren't a chrooted user\n", quis);
 104     exit(EXIT_FAILURE);
 105   }
 106   endpwent();
 107
 108   /* --- Chroot the user --- */
 109
 110   {
 111     char *p = xstrdup(pw->pw_dir);
 112     char *q = strstr(p, "/./");
 113     if (q)
 114       *q = 0;
 115
 116     if (chdir(p) || chroot(p)) {
 117       fprintf(stderr, "%s: couldn't call chroot: %s", quis, strerror(errno));
 118       exit(EXIT_FAILURE);
 119     }
 120     setuid(me);
 121     free(p);
 122   }
 123
 124   /* --- Read the new password block --- */
 125
 126   {
 127     char *p = xstrdup(pw->pw_name);
 128     pw = getpwnam(p);
 129     free(p);
 130     if (!pw) {
 131       fprintf(stderr, "%s: you don't exist in the gaol\n", quis);
 132       exit(EXIT_FAILURE);
 133     }
 134     endpwent();
 135   }
 136
 137   /* --- Now fiddle with environment strings and suchlike --- */
 138
 139   {
 140     size_t n;
 141     for (n = 0; environ[n]; n++)
 142       ;
 143     env = xmalloc((n + 1) * sizeof(char *));
 144
 145     for (n = 0; environ[n]; n++) {
 146       if (strncmp(environ[n], "HOME=", 5) == 0) {
 147         char *p = xmalloc(6 + strlen(pw->pw_dir));
 148         sprintf(p, "HOME=%s", pw->pw_dir);
 149         env[n] = p;
 150       } else if (strncmp(environ[n], "SHELL=", 6) == 0) {
 151         char *p = xmalloc(7 + strlen(pw->pw_shell));
 152         sprintf(p, "SHELL=%s", pw->pw_shell);
 153         env[n] = p;
 154       } else
 155         env[n] = environ[n];
 156     }
 157     env[n] = 0;
 158   }
 159
 160   /* --- Finally, sort the argument list --- */
 161
 162   {
 163     char *p, *q;
 164     int i;
 165
 166     av = xmalloc((argc + 1) * sizeof(char *));
 167     p = pw->pw_shell;
 168     for (q = p; *q; q++) {
 169       if (*q == '/')
 170         p = q + 1;
 171     }
 172     if (argv[0][0] == '-') {
 173       q = xmalloc(2 + strlen(p));
 174       *q = '-';
 175       strcpy(q + 1, p);
 176       av[0] = q;
 177     } else
 178       av[0] = p;
 179
 180     for (i = 1; i <= argc; i++)
 181       av[i] = argv[i];
 182   }
 183
 184   /* --- Change directory (again) --- */
 185
 186   if (chdir(pw->pw_dir))
 187     fprintf(stderr, "No directory, logging in with HOME=/\n");
 188
 189   /* --- Run the real shell --- */
 190
 191   execve(pw->pw_shell, av, env);
 192   fprintf(stderr, "%s: couldn't exec `%s': %s",
 193           quis, pw->pw_shell, strerror(errno));
 194   return (EXIT_FAILURE);
 195 }
 196
 197 /*----- That's all, folks -------------------------------------------------*/