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linux: resolve symlinks for bind mounts
resolve symlinks in the target. It solves an issue when running Kubernetes as secrets are mounted to /var/run, but it is a symlink to /run. Signed-off-by: Giuseppe Scrivano <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,168 @@ | ||
| /* | ||
| * chroot_realpath.c -- reslove pathname as if inside chroot | ||
| * Based on realpath.c Copyright (C) 1993 Rick Sladkey <[email protected]> | ||
| * | ||
| * This program is free software; you can redistribute it and/or | ||
| * modify it under the terms of the GNU Lesser General Public | ||
| * License as published by the Free Software Foundation; either | ||
| * version 2.1 of the License, or (at your option) any later version. | ||
| * | ||
| * This library 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 | ||
| * Lesser General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU Lesser General Public | ||
| * License along with this library; see the file COPYING.LIB. If not, | ||
| * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, | ||
| * Boston, MA 02111-1307, USA. | ||
| * | ||
| * 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; | ||
| } |
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