| /* |
| * realpath.c -- canonicalize pathname by removing symlinks |
| * Copyright (C) 1993 Rick Sladkey <jrs@world.std.com> |
| * |
| * 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. |
| */ |
| |
| #undef resolve_symlinks |
| |
| /* |
| * This routine is part of libc. We include it nevertheless, |
| * since the libc version has some security flaws. |
| */ |
| |
| #include <limits.h> /* for PATH_MAX */ |
| #ifndef PATH_MAX |
| #define PATH_MAX 8192 |
| #endif |
| #include <unistd.h> |
| #include <string.h> |
| #include <errno.h> |
| #include "realpath.h" |
| #include "sundries.h" /* for xstrdup */ |
| |
| #define MAX_READLINKS 32 |
| |
| /* this leaks some memory - unimportant for mount */ |
| char * |
| myrealpath(const char *path, char *resolved_path, int maxreslth) { |
| int readlinks = 0; |
| char *npath; |
| char link_path[PATH_MAX+1]; |
| int n; |
| #ifdef resolve_symlinks |
| char *buf; |
| int m; |
| #endif |
| |
| 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; |
| return NULL; |
| } |
| *npath++ = *path++; |
| } |
| |
| /* Protect against infinite loops. */ |
| if (readlinks++ > MAX_READLINKS) { |
| errno = ELOOP; |
| return NULL; |
| } |
| |
| /* 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) |
| return NULL; |
| } else { |
| #ifdef resolve_symlinks /* Richard Gooch dislikes sl resolution */ |
| /* 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); |
| buf = xmalloc(m + n + 1); |
| memcpy(buf, link_path, n); |
| memcpy(buf + n, path, m + 1); |
| path = buf; |
| #endif |
| } |
| *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'; |
| return resolved_path; |
| } |