diff options
Diffstat (limited to 'utils/chroot_realpath.c')
| -rw-r--r-- | utils/chroot_realpath.c | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/utils/chroot_realpath.c b/utils/chroot_realpath.c new file mode 100644 index 000000000..43ce9a528 --- /dev/null +++ b/utils/chroot_realpath.c @@ -0,0 +1,163 @@ +/* + * chroot_realpath.c -- reslove pathname as if inside chroot + * Based on realpath.c 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. + * + * 2005/09/12: Dan Howell (modified from realpath.c to emulate chroot) + */ + +#ifdef HAVE_CONFIG_H +#include <config.h> +#endif + +#include <sys/types.h> +#include <unistd.h> +#include <stdio.h> +#include <string.h> +#include <strings.h> +#include <limits.h> /* for PATH_MAX */ +#include <sys/param.h> /* for MAXPATHLEN */ +#include <errno.h> +#ifndef __set_errno +#define __set_errno(val) ((errno) = (val)) +#endif + +#include <sys/stat.h> /* for S_IFLNK */ + +#ifndef PATH_MAX +#define PATH_MAX _POSIX_PATH_MAX +#endif + +#define MAX_READLINKS 32 + +char *chroot_realpath(const char *chroot, const char *path, char resolved_path[]) +{ + char copy_path[PATH_MAX]; + char link_path[PATH_MAX]; + char got_path[PATH_MAX]; + char *got_path_root = got_path; + char *new_path = got_path; + char *max_path; + int readlinks = 0; + int n; + int chroot_len; + + /* Trivial case. */ + if (chroot == NULL || *chroot == '\0' || + (*chroot == '/' && chroot[1] == '\0')) { + strcpy(resolved_path, path); + return resolved_path; + } + + chroot_len = strlen(chroot); + + if (chroot_len + strlen(path) >= PATH_MAX - 3) { + __set_errno(ENAMETOOLONG); + return NULL; + } + + /* Make a copy of the source path since we may need to modify it. */ + strcpy(copy_path, path); + path = copy_path; + max_path = copy_path + PATH_MAX - chroot_len - 3; + + /* Start with the chroot path. */ + strcpy(new_path, chroot); + new_path += chroot_len; + while (*new_path == '/' && new_path > got_path) + new_path--; + got_path_root = new_path; + *new_path++ = '/'; + + /* Expand each slash-separated pathname component. */ + while (*path != '\0') { + /* Ignore stray "/". */ + if (*path == '/') { + path++; + continue; + } + if (*path == '.') { + /* Ignore ".". */ + if (path[1] == '\0' || path[1] == '/') { + path++; + continue; + } + if (path[1] == '.') { + if (path[2] == '\0' || path[2] == '/') { + path += 2; + /* Ignore ".." at root. */ + if (new_path == got_path_root + 1) + continue; + /* Handle ".." by backing up. */ + while ((--new_path)[-1] != '/'); + continue; + } + } + } + /* Safely copy the next pathname component. */ + while (*path != '\0' && *path != '/') { + if (path > max_path) { + __set_errno(ENAMETOOLONG); + return NULL; + } + *new_path++ = *path++; + } + if (*path == '\0') + /* Don't follow symlink for last pathname component. */ + break; +#ifdef S_IFLNK + /* Protect against infinite loops. */ + if (readlinks++ > MAX_READLINKS) { + __set_errno(ELOOP); + return NULL; + } + /* See if latest pathname component is a symlink. */ + *new_path = '\0'; + n = readlink(got_path, link_path, PATH_MAX - 1); + if (n < 0) { + /* EINVAL means the file exists but isn't a symlink. */ + if (errno != EINVAL) { + /* Make sure it's null terminated. */ + *new_path = '\0'; + strcpy(resolved_path, got_path); + return NULL; + } + } else { + /* Note: readlink doesn't add the null byte. */ + link_path[n] = '\0'; + if (*link_path == '/') + /* Start over for an absolute symlink. */ + new_path = got_path_root; + else + /* Otherwise back up over this component. */ + while (*(--new_path) != '/'); + /* Safe sex check. */ + if (strlen(path) + n >= PATH_MAX - 2) { + __set_errno(ENAMETOOLONG); + return NULL; + } + /* Insert symlink contents into path. */ + strcat(link_path, path); + strcpy(copy_path, link_path); + path = copy_path; + } +#endif /* S_IFLNK */ + *new_path++ = '/'; + } + /* Delete trailing slash but don't whomp a lone slash. */ + if (new_path != got_path + 1 && new_path[-1] == '/') + new_path--; + /* Make sure it's null terminated. */ + *new_path = '\0'; + strcpy(resolved_path, got_path); + return resolved_path; +} |