chcon.c

/* chcon -- change security context of files
   Copyright (C) 2005-2020 Free Software Foundation, Inc.

   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 3 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, see <https://www.gnu.org/licenses/>.  */

#include <config.h>
#include <stdio.h>
#include <sys/types.h>
#include <getopt.h>
#include <selinux/selinux.h>

#include "system.h"
#include "dev-ino.h"
#include "die.h"
#include "error.h"
#include "ignore-value.h"
#include "quote.h"
#include "root-dev-ino.h"
#include "selinux-at.h"
#include "xfts.h"

/* The official name of this program (e.g., no 'g' prefix).  */
#define PROGRAM_NAME "chcon"

#define AUTHORS \
  proper_name ("Russell Coker"), \
  proper_name ("Jim Meyering")

/* If nonzero, and the systems has support for it, change the context
   of symbolic links rather than any files they point to.  */
static bool affect_symlink_referent;

/* If true, change the modes of directories recursively. */
static bool recurse;

/* Level of verbosity. */
static bool verbose;

/* Pointer to the device and inode numbers of '/', when --recursive.
   Otherwise NULL.  */
static struct dev_ino *root_dev_ino;

/* The name of the context file is being given. */
static char const *specified_context;

/* Specific components of the context */
static char const *specified_user;
static char const *specified_role;
static char const *specified_range;
static char const *specified_type;

/* For long options that have no equivalent short option, use a
   non-character as a pseudo short option, starting with CHAR_MAX + 1.  */
enum
{
  DEREFERENCE_OPTION = CHAR_MAX + 1,
  NO_PRESERVE_ROOT,
  PRESERVE_ROOT,
  REFERENCE_FILE_OPTION
};

static struct option const long_options[] =
{
  {"recursive", no_argument, NULL, 'R'},
  {"dereference", no_argument, NULL, DEREFERENCE_OPTION},
  {"no-dereference", no_argument, NULL, 'h'},
  {"no-preserve-root", no_argument, NULL, NO_PRESERVE_ROOT},
  {"preserve-root", no_argument, NULL, PRESERVE_ROOT},
  {"reference", required_argument, NULL, REFERENCE_FILE_OPTION},
  {"user", required_argument, NULL, 'u'},
  {"role", required_argument, NULL, 'r'},
  {"type", required_argument, NULL, 't'},
  {"range", required_argument, NULL, 'l'},
  {"verbose", no_argument, NULL, 'v'},
  {GETOPT_HELP_OPTION_DECL},
  {GETOPT_VERSION_OPTION_DECL},
  {NULL, 0, NULL, 0}
};

/* Given a security context, CONTEXT, derive a context_t (*RET),
   setting any portions selected via the global variables, specified_user,
   specified_role, etc.  */
static int
compute_context_from_mask (char const *context, context_t *ret)
{
  bool ok = true;
  context_t new_context = context_new (context);
  if (!new_context)
    {
      error (0, errno, _("failed to create security context: %s"),
             quote (context));
      return 1;
    }

#define SET_COMPONENT(C, comp)						\
   do									\
     {									\
       if (specified_ ## comp						\
           && context_ ## comp ## _set ((C), specified_ ## comp))	\
         {								\
            error (0, errno,						\
                   _("failed to set %s security context component to %s"), \
                   #comp, quote (specified_ ## comp));			\
           ok = false;							\
         }								\
     }									\
   while (0)

  SET_COMPONENT (new_context, user);
  SET_COMPONENT (new_context, range);
  SET_COMPONENT (new_context, role);
  SET_COMPONENT (new_context, type);

  if (!ok)
    {
      int saved_errno = errno;
      context_free (new_context);
      errno = saved_errno;
      return 1;
    }

  *ret = new_context;
  return 0;
}

/* Change the context of FILE, using specified components.
   If it is a directory and -R is given, recurse.
   Return 0 if successful, 1 if errors occurred. */

static int
change_file_context (int fd, char const *file)
{
  char *file_context = NULL;
  context_t context IF_LINT (= 0);
  char const * context_string;
  int errors = 0;

  if (specified_context == NULL)
    {
      int status = (affect_symlink_referent
                    ? getfileconat (fd, file, &file_context)
                    : lgetfileconat (fd, file, &file_context));

      if (status < 0 && errno != ENODATA)
        {
          error (0, errno, _("failed to get security context of %s"),
                 quoteaf (file));
          return 1;
        }

      /* If the file doesn't have a context, and we're not setting all of
         the context components, there isn't really an obvious default.
         Thus, we just give up. */
      if (file_context == NULL)
        {
          error (0, 0, _("can't apply partial context to unlabeled file %s"),
                 quoteaf (file));
          return 1;
        }

      if (compute_context_from_mask (file_context, &context))
        return 1;

      context_string = context_str (context);
    }
  else
    {
      context_string = specified_context;
    }

  if (file_context == NULL || ! STREQ (context_string, file_context))
    {
      int fail = (affect_symlink_referent
                  ?  setfileconat (fd, file, se_const (context_string))
                  : lsetfileconat (fd, file, se_const (context_string)));

      if (fail)
        {
          errors = 1;
          error (0, errno, _("failed to change context of %s to %s"),
                 quoteaf_n (0, file), quote_n (1, context_string));
        }
    }

  if (specified_context == NULL)
    {
      context_free (context);
      freecon (file_context);
    }

  return errors;
}

/* Change the context of FILE.
   Return true if successful.  This function is called
   once for every file system object that fts encounters.  */

static bool
process_file (FTS *fts, FTSENT *ent)
{
  char const *file_full_name = ent->fts_path;
  char const *file = ent->fts_accpath;
  const struct stat *file_stats = ent->fts_statp;
  bool ok = true;

  switch (ent->fts_info)
    {
    case FTS_D:
      if (recurse)
        {
          if (ROOT_DEV_INO_CHECK (root_dev_ino, ent->fts_statp))
            {
              /* This happens e.g., with "chcon -R --preserve-root ... /"
                 and with "chcon -RH --preserve-root ... symlink-to-root".  */
              ROOT_DEV_INO_WARN (file_full_name);
              /* Tell fts not to traverse into this hierarchy.  */
              fts_set (fts, ent, FTS_SKIP);
              /* Ensure that we do not process "/" on the second visit.  */
              ignore_value (fts_read (fts));
              return false;
            }
          return true;
        }
      break;

    case FTS_DP:
      if (! recurse)
        return true;
      break;

    case FTS_NS:
      /* For a top-level file or directory, this FTS_NS (stat failed)
         indicator is determined at the time of the initial fts_open call.
         With programs like chmod, chown, and chgrp, that modify
         permissions, it is possible that the file in question is
         accessible when control reaches this point.  So, if this is
         the first time we've seen the FTS_NS for this file, tell
         fts_read to stat it "again".  */
      if (ent->fts_level == 0 && ent->fts_number == 0)
        {
          ent->fts_number = 1;
          fts_set (fts, ent, FTS_AGAIN);
          return true;
        }
      error (0, ent->fts_errno, _("cannot access %s"),
             quoteaf (file_full_name));
      ok = false;
      break;

    case FTS_ERR:
      error (0, ent->fts_errno, "%s", quotef (file_full_name));
      ok = false;
      break;

    case FTS_DNR:
      error (0, ent->fts_errno, _("cannot read directory %s"),
             quoteaf (file_full_name));
      ok = false;
      break;

    case FTS_DC:		/* directory that causes cycles */
      if (cycle_warning_required (fts, ent))
        {
          emit_cycle_warning (file_full_name);
          return false;
        }
      break;

    default:
      break;
    }

  if (ent->fts_info == FTS_DP
      && ok && ROOT_DEV_INO_CHECK (root_dev_ino, file_stats))
    {
      ROOT_DEV_INO_WARN (file_full_name);
      ok = false;
    }

  if (ok)
    {
      if (verbose)
        printf (_("changing security context of %s\n"),
                quoteaf (file_full_name));

      if (change_file_context (fts->fts_cwd_fd, file) != 0)
        ok = false;
    }

  if ( ! recurse)
    fts_set (fts, ent, FTS_SKIP);

  return ok;
}

/* Recursively operate on the specified FILES (the last entry
   of which is NULL).  BIT_FLAGS controls how fts works.
   Return true if successful.  */

static bool
process_files (char **files, int bit_flags)
{
  bool ok = true;

  FTS *fts = xfts_open (files, bit_flags, NULL);

  while (1)
    {
      FTSENT *ent;

      ent = fts_read (fts);
      if (ent == NULL)
        {
          if (errno != 0)
            {
              /* FIXME: try to give a better message  */
              error (0, errno, _("fts_read failed"));
              ok = false;
            }
          break;
        }

      ok &= process_file (fts, ent);
    }

  if (fts_close (fts) != 0)
    {
      error (0, errno, _("fts_close failed"));
      ok = false;
    }

  return ok;
}

void
usage (int status)
{
  if (status != EXIT_SUCCESS)
    emit_try_help ();
  else
    {
      printf (_("\
Usage: %s [OPTION]... CONTEXT FILE...\n\
  or:  %s [OPTION]... [-u USER] [-r ROLE] [-l RANGE] [-t TYPE] FILE...\n\
  or:  %s [OPTION]... --reference=RFILE FILE...\n\
"),
        program_name, program_name, program_name);
      fputs (_("\
Change the SELinux security context of each FILE to CONTEXT.\n\
With --reference, change the security context of each FILE to that of RFILE.\n\
"), stdout);

      emit_mandatory_arg_note ();

      fputs (_("\
      --dereference      affect the referent of each symbolic link (this is\n\
                         the default), rather than the symbolic link itself\n\
  -h, --no-dereference   affect symbolic links instead of any referenced file\n\
"), stdout);
      fputs (_("\
  -u, --user=USER        set user USER in the target security context\n\
  -r, --role=ROLE        set role ROLE in the target security context\n\
  -t, --type=TYPE        set type TYPE in the target security context\n\
  -l, --range=RANGE      set range RANGE in the target security context\n\
"), stdout);
      fputs (_("\
      --no-preserve-root  do not treat '/' specially (the default)\n\
      --preserve-root    fail to operate recursively on '/'\n\
"), stdout);
      fputs (_("\
      --reference=RFILE  use RFILE's security context rather than specifying\n\
                         a CONTEXT value\n\
"), stdout);
      fputs (_("\
  -R, --recursive        operate on files and directories recursively\n\
"), stdout);
      fputs (_("\
  -v, --verbose          output a diagnostic for every file processed\n\
"), stdout);
      fputs (_("\
\n\
The following options modify how a hierarchy is traversed when the -R\n\
option is also specified.  If more than one is specified, only the final\n\
one takes effect.\n\
\n\
  -H                     if a command line argument is a symbolic link\n\
                         to a directory, traverse it\n\
  -L                     traverse every symbolic link to a directory\n\
                         encountered\n\
  -P                     do not traverse any symbolic links (default)\n\
\n\
"), stdout);
      fputs (HELP_OPTION_DESCRIPTION, stdout);
      fputs (VERSION_OPTION_DESCRIPTION, stdout);
      emit_ancillary_info (PROGRAM_NAME);
    }
  exit (status);
}

int
main (int argc, char **argv)
{
  /* Bit flags that control how fts works.  */
  int bit_flags = FTS_PHYSICAL;

  /* 1 if --dereference, 0 if --no-dereference, -1 if neither has been
     specified.  */
  int dereference = -1;

  bool ok;
  bool preserve_root = false;
  bool component_specified = false;
  char *reference_file = NULL;
  int optc;

  initialize_main (&argc, &argv);
  set_program_name (argv[0]);
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);

  atexit (close_stdout);

  while ((optc = getopt_long (argc, argv, "HLPRhvu:r:t:l:", long_options, NULL))
         != -1)
    {
      switch (optc)
        {
        case 'H': /* Traverse command-line symlinks-to-directories.  */
          bit_flags = FTS_COMFOLLOW | FTS_PHYSICAL;
          break;

        case 'L': /* Traverse all symlinks-to-directories.  */
          bit_flags = FTS_LOGICAL;
          break;

        case 'P': /* Traverse no symlinks-to-directories.  */
          bit_flags = FTS_PHYSICAL;
          break;

        case 'h': /* --no-dereference: affect symlinks */
          dereference = 0;
          break;

        case DEREFERENCE_OPTION: /* --dereference: affect the referent
                                    of each symlink */
          dereference = 1;
          break;

        case NO_PRESERVE_ROOT:
          preserve_root = false;
          break;

        case PRESERVE_ROOT:
          preserve_root = true;
          break;

        case REFERENCE_FILE_OPTION:
          reference_file = optarg;
          break;

        case 'R':
          recurse = true;
          break;

        case 'f':
          /* ignore */
          break;

        case 'v':
          verbose = true;
          break;

        case 'u':
          specified_user = optarg;
          component_specified = true;
          break;

        case 'r':
          specified_role = optarg;
          component_specified = true;
          break;

        case 't':
          specified_type = optarg;
          component_specified = true;
          break;

        case 'l':
          specified_range = optarg;
          component_specified = true;
          break;

        case_GETOPT_HELP_CHAR;
        case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);
        default:
          usage (EXIT_FAILURE);
        }
    }

  if (recurse)
    {
      if (bit_flags == FTS_PHYSICAL)
        {
          if (dereference == 1)
            die (EXIT_FAILURE, 0,
                 _("-R --dereference requires either -H or -L"));
          affect_symlink_referent = false;
        }
      else
        {
          if (dereference == 0)
            die (EXIT_FAILURE, 0, _("-R -h requires -P"));
          affect_symlink_referent = true;
        }
    }
  else
    {
      bit_flags = FTS_PHYSICAL;
      affect_symlink_referent = (dereference != 0);
    }

  if (argc - optind < (reference_file || component_specified ? 1 : 2))
    {
      if (argc <= optind)
        error (0, 0, _("missing operand"));
      else
        error (0, 0, _("missing operand after %s"), quote (argv[argc - 1]));
      usage (EXIT_FAILURE);
    }

  if (reference_file)
    {
      char *ref_context = NULL;

      if (getfilecon (reference_file, &ref_context) < 0)
        die (EXIT_FAILURE, errno, _("failed to get security context of %s"),
             quoteaf (reference_file));

      specified_context = ref_context;
    }
  else if (component_specified)
    {
      /* FIXME: it's already null, so this is a no-op. */
      specified_context = NULL;
    }
  else
    {
      specified_context = argv[optind++];
      if (0 < is_selinux_enabled ()
          && security_check_context (se_const (specified_context)) < 0)
        die (EXIT_FAILURE, errno, _("invalid context: %s"),
             quote (specified_context));
    }

  if (reference_file && component_specified)
    {
      error (0, 0, _("conflicting security context specifiers given"));
      usage (EXIT_FAILURE);
    }

  if (recurse && preserve_root)
    {
      static struct dev_ino dev_ino_buf;
      root_dev_ino = get_root_dev_ino (&dev_ino_buf);
      if (root_dev_ino == NULL)
        die (EXIT_FAILURE, errno, _("failed to get attributes of %s"),
             quoteaf ("/"));
    }
  else
    {
      root_dev_ino = NULL;
    }

  ok = process_files (argv + optind, bit_flags | FTS_NOSTAT);

  return ok ? EXIT_SUCCESS : EXIT_FAILURE;
}