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/*
* 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
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