/* * canonicalize.c -- canonicalize pathname by removing symlinks * Copyright (C) 1993 Rick Sladkey * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU Library Public License as published by * the Free Software Foundation; either version 2, 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 Library Public License for more details. * */ /* * This routine is part of libc. We include it nevertheless, * since the libc version has some security flaws. * * TODO: use canonicalize_file_name() when exist in glibc */ #include #include #include #include #include #include #include "canonicalize.h" #ifndef MAXSYMLINKS # define MAXSYMLINKS 256 #endif static char * myrealpath(const char *path, char *resolved_path, int maxreslth) { int readlinks = 0; char *npath; char link_path[PATH_MAX+1]; int n; char *buf = NULL; npath = resolved_path; /* If it's a relative pathname use getcwd for starters. */ if (*path != '/') { if (!getcwd(npath, maxreslth-2)) return NULL; npath += strlen(npath); if (npath[-1] != '/') *npath++ = '/'; } else { *npath++ = '/'; path++; } /* Expand each slash-separated pathname component. */ while (*path != '\0') { /* Ignore stray "/" */ if (*path == '/') { path++; continue; } if (*path == '.' && (path[1] == '\0' || path[1] == '/')) { /* Ignore "." */ path++; continue; } if (*path == '.' && path[1] == '.' && (path[2] == '\0' || path[2] == '/')) { /* Backup for ".." */ path += 2; while (npath > resolved_path+1 && (--npath)[-1] != '/') ; continue; } /* Safely copy the next pathname component. */ while (*path != '\0' && *path != '/') { if (npath-resolved_path > maxreslth-2) { errno = ENAMETOOLONG; goto err; } *npath++ = *path++; } /* Protect against infinite loops. */ if (readlinks++ > MAXSYMLINKS) { errno = ELOOP; goto err; } /* See if last pathname component is a symlink. */ *npath = '\0'; n = readlink(resolved_path, link_path, PATH_MAX); if (n < 0) { /* EINVAL means the file exists but isn't a symlink. */ if (errno != EINVAL) goto err; } else { int m; char *newbuf; /* Note: readlink doesn't add the null byte. */ link_path[n] = '\0'; if (*link_path == '/') /* Start over for an absolute symlink. */ npath = resolved_path; else /* Otherwise back up over this component. */ while (*(--npath) != '/') ; /* Insert symlink contents into path. */ m = strlen(path); newbuf = malloc(m + n + 1); if (!newbuf) goto err; memcpy(newbuf, link_path, n); memcpy(newbuf + n, path, m + 1); free(buf); path = buf = newbuf; } *npath++ = '/'; } /* Delete trailing slash but don't whomp a lone slash. */ if (npath != resolved_path+1 && npath[-1] == '/') npath--; /* Make sure it's null terminated. */ *npath = '\0'; free(buf); return resolved_path; err: free(buf); return NULL; } /* * Converts private "dm-N" names to "/dev/mapper/" * * Since 2.6.29 (patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128) kernel sysfs * provides the real DM device names in /sys/block//dm/name */ char * canonicalize_dm_name(const char *ptname) { FILE *f; size_t sz; char path[256], name[256], *res = NULL; snprintf(path, sizeof(path), "/sys/block/%s/dm/name", ptname); if (!(f = fopen(path, "r"))) return NULL; /* read "\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); res = strdup(path); } fclose(f); return res; } char * canonicalize_path(const char *path) { char canonical[PATH_MAX+2]; char *p; if (path == NULL) return NULL; if (!myrealpath(path, canonical, PATH_MAX+1)) return strdup(path); p = strrchr(canonical, '/'); if (p && strncmp(p, "/dm-", 4) == 0 && isdigit(*(p + 4))) { p = canonicalize_dm_name(p+1); if (p) return p; } return strdup(canonical); } #ifdef TEST_PROGRAM int main(int argc, char **argv) { if (argc < 2) { fprintf(stderr, "usage: %s \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