/*

 * canonicalize.c -- canonicalize pathname by removing symlinks

 *

 * This file may be distributed under the terms of the

 * GNU Lesser General Public License.

 *

 * Copyright (C) 2009-2013 Karel Zak <kzak@redhat.com>

 */

#include <stdio.h>

#include <string.h>

#include <ctype.h>

#include <unistd.h>

#include <errno.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/stat.h>

#include "canonicalize.h"

#include "pathnames.h"

#include "all-io.h"

#include "strutils.h"

#include "fileutils.h"

/*

 * Converts private "dm-N" names to "/dev/mapper/<name>"

 *

 * Since 2.6.29 (patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128) kernel sysfs

 * provides the real DM device names in /sys/block/<ptname>/dm/name

 *

 * The @prefix allows /sys to be mounted or stored outside the system root

 * (/prefix/sys/...).

 */

char *ul_canonicalize_dm_name_prefixed(const char *prefix, const char *ptname)

{

  FILE  *f;

  size_t  sz;

  char  path[256], name[sizeof(path) - sizeof(_PATH_DEV_MAPPER)], *res = NULL;

  if (!ptname || !*ptname)

    return NULL;

  if (!prefix)

    prefix = "";

  snprintf(path, sizeof(path), "%s/sys/block/%s/dm/name", prefix, ptname);

  if (!(f = fopen(path, "r" UL_CLOEXECSTR)))

    return NULL;

  /* read "<name>\n" from sysfs */

  if (fgets(name, sizeof(name), f) && (sz = strlen(name)) > 1) {

    name[sz - 1] = '\0';

    snprintf(path, sizeof(path), _PATH_DEV_MAPPER "/%s", name);

    if ((prefix && *prefix) || access(path, F_OK) == 0)

      res = strdup(path);

  }

  fclose(f);

  return res;

}

char *ul_canonicalize_dm_name(const char *ptname)

{

  return ul_canonicalize_dm_name_prefixed(NULL, ptname);

}

static int is_dm_devname(char *canonical, char **name)

{

  struct stat sb;

  char *p = strrchr(canonical, '/');

  *name = NULL;

  if (!p

      || strncmp(p, "/dm-", 4) != 0

      || !isdigit(*(p + 4))

      || stat(canonical, &sb) != 0

      || !S_ISBLK(sb.st_mode))

    return 0;

  *name = p + 1;

  return 1;

}

/*

 * This function does not canonicalize the path! It just prepends CWD before a

 * relative path. If the path is no relative than returns NULL. The path does

 * not have to exist.

 */

char *ul_absolute_path(const char *path)

{

  char cwd[PATH_MAX], *res, *p;

  size_t psz, csz;

  if (!ul_is_relative_path(path)) {

    errno = EINVAL;

    return NULL;

  }

  if (!getcwd(cwd, sizeof(cwd)))

    return NULL;

  /* simple clean up */

  if (ul_startswith(path, "./"))

    path += 2;

  else if (strcmp(path, ".") == 0)

    path = NULL;

  if (!path || !*path)

    return strdup(cwd);

  csz = strlen(cwd);

  psz = strlen(path);

  p = res = malloc(csz + 1 + psz + 1);

  if (!res)

    return NULL;

  p = mempcpy(p, cwd, csz);

  *p++ = '/';

  memcpy(p, path, psz + 1);

  return res;

}

/*

 * Returns: <0 on error, 1 is cannot be canonicalized (errno is set); 0 on success

 */

static int __attribute__((nonnull(2)))

do_canonicalize(const char *path, char **result,

    void *data __attribute__((__unused__)))

{

  char *canonical, *dmname;

  *result = NULL;

  if (!path || !*path) {

    errno = EINVAL;

    return -errno;

  }

  errno = 0;

  canonical = realpath(path, NULL);

  if (!canonical)

    return 1;

  if (is_dm_devname(canonical, &dmname)) {

    char *dm = ul_canonicalize_dm_name(dmname);

    if (dm) {

      free(canonical);

      canonical = dm;

    }

  }

  if (canonical)

    *result = canonical;

  return 0;

}

/*

 * Always returns a newly allocated string or NULL in case of an error. An

 * unreachable path is not an error (!), and in this case, it just duplicates

 * @path.

 */

char *ul_canonicalize_path(const char *path)

{

  char *canonical = NULL;

  if (do_canonicalize(path, &canonical, NULL) == 1)

    return strdup(path);

  return canonical;

}

/*

 * Drop permissions (e.g., suid) and canonicalize the path. If the path is

 * unreadable (for example, due to missing permissions), it returns NULL.

 */

char *ul_canonicalize_path_restricted(const char *path)

{

  return ul_restricted_path_oper(path, do_canonicalize, NULL);

}

#ifdef TEST_PROGRAM_CANONICALIZE

int main(int argc, char **argv)

{

  char *p;

  if (argc < 2) {

    fprintf(stderr, "usage: %s <device>\n", argv[0]);

    exit(EXIT_FAILURE);

  }

  fprintf(stdout, "orig:            %s\n", argv[1]);

  p = ul_canonicalize_path(argv[1]);

  fprintf(stdout, "real:            %s\n", p);

  free(p);

  p = ul_canonicalize_path_restricted(argv[1]);

  fprintf(stdout, "real-restricted: %s\n", p);

  free(p);

  exit(EXIT_SUCCESS);

}

#endif