| /* |
| * 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" |
| |
| /* |
| * 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 |
| */ |
| char *canonicalize_dm_name(const char *ptname) |
| { |
| FILE *f; |
| size_t sz; |
| char path[256], name[256], *res = NULL; |
| |
| if (!ptname || !*ptname) |
| return NULL; |
| |
| snprintf(path, sizeof(path), "/sys/block/%s/dm/name", 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), "/dev/mapper/%s", name); |
| |
| if (access(path, F_OK) == 0) |
| res = strdup(path); |
| } |
| fclose(f); |
| return res; |
| } |
| |
| 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 *absolute_path(const char *path) |
| { |
| char cwd[PATH_MAX], *res, *p; |
| size_t psz, csz; |
| |
| if (!is_relative_path(path)) { |
| errno = EINVAL; |
| return NULL; |
| } |
| if (!getcwd(cwd, sizeof(cwd))) |
| return NULL; |
| |
| /* simple clean up */ |
| if (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; |
| |
| memcpy(p, cwd, csz); |
| p += csz; |
| *p++ = '/'; |
| memcpy(p, path, psz + 1); |
| |
| return res; |
| } |
| |
| char *canonicalize_path(const char *path) |
| { |
| char *canonical, *dmname; |
| |
| if (!path || !*path) |
| return NULL; |
| |
| canonical = realpath(path, NULL); |
| if (!canonical) |
| return strdup(path); |
| |
| if (is_dm_devname(canonical, &dmname)) { |
| char *dm = canonicalize_dm_name(dmname); |
| if (dm) { |
| free(canonical); |
| return dm; |
| } |
| } |
| |
| return canonical; |
| } |
| |
| char *canonicalize_path_restricted(const char *path) |
| { |
| char *canonical, *dmname; |
| int errsv; |
| uid_t euid; |
| gid_t egid; |
| |
| if (!path || !*path) |
| return NULL; |
| |
| euid = geteuid(); |
| egid = getegid(); |
| |
| /* drop permissions */ |
| if (setegid(getgid()) < 0 || seteuid(getuid()) < 0) |
| return NULL; |
| |
| errsv = errno = 0; |
| |
| canonical = realpath(path, NULL); |
| if (!canonical) |
| errsv = errno; |
| else if (is_dm_devname(canonical, &dmname)) { |
| char *dm = canonicalize_dm_name(dmname); |
| if (dm) { |
| free(canonical); |
| canonical = dm; |
| } |
| } |
| |
| /* restore */ |
| if (setegid(egid) < 0 || seteuid(euid) < 0) { |
| free(canonical); |
| return NULL; |
| } |
| |
| errno = errsv; |
| return canonical; |
| } |
| |
| |
| #ifdef TEST_PROGRAM_CANONICALIZE |
| int main(int argc, char **argv) |
| { |
| if (argc < 2) { |
| fprintf(stderr, "usage: %s <device>\n", argv[0]); |
| exit(EXIT_FAILURE); |
| } |
| |
| fprintf(stdout, "orig: %s\n", argv[1]); |
| fprintf(stdout, "real: %s\n", canonicalize_path(argv[1])); |
| exit(EXIT_SUCCESS); |
| } |
| #endif |