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extension-release: search for other files if expected name not found

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In some cases image names are unpredictable - some orchestrators/deployment
tools like to mangle names to suit their internal formats. In these cases,
the requirement that the extension-release file matches exactly the image
name where it's contained cannot work.

Allow falling back to loading the first regular file which name starts with
'extension-release' located in /usr/lib/extension-release.d/ and tagged with
a user.extension-release.strict extended attribute with a true value, if the
one with the expected name cannot be found.
This commit is contained in:
Luca Boccassi
2021-08-17 13:04:44 +01:00
parent 5ce46344fd
commit 9a4b883be2
5 changed files with 138 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/basic/os-util.c
+91 -2
View File
@@ -1,6 +1,7 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "alloc-util.h"
#include "dirent-util.h"
#include "env-file.h"
#include "env-util.h"
#include "fd-util.h"
@@ -8,10 +9,13 @@
#include "fs-util.h"
#include "macro.h"
#include "os-util.h"
#include "parse-util.h"
#include "path-util.h"
#include "stat-util.h"
#include "string-util.h"
#include "strv.h"
#include "utf8.h"
#include "xattr-util.h"
bool image_name_is_valid(const char *s) {
if (!filename_is_valid(s))
@@ -41,8 +45,8 @@ int path_is_extension_tree(const char *path, const char *extension) {
if (laccess(path, F_OK) < 0)
return -errno;
/* We use /usr/lib/extension-release.d/extension-release.NAME as flag file if something is a system extension,
* and {/etc|/usr/lib}/os-release as flag file if something is an OS (in case extension == NULL) */
/* We use /usr/lib/extension-release.d/extension-release[.NAME] as flag for something being a system extension,
* and {/etc|/usr/lib}/os-release as a flag for something being an OS (when not an extension). */
r = open_extension_release(path, extension, NULL, NULL);
if (r == -ENOENT) /* We got nothing */
return 0;
@@ -67,6 +71,91 @@ int open_extension_release(const char *root, const char *extension, char **ret_p
r = chase_symlinks(extension_full_path, root, CHASE_PREFIX_ROOT,
ret_path ? &q : NULL,
ret_fd ? &fd : NULL);
/* Cannot find the expected extension-release file? The image filename might have been
* mangled on deployment, so fallback to checking for any file in the extension-release.d
* directory, and return the first one with a user.extension-release xattr instead.
* The user.extension-release.strict xattr is checked to ensure the author of the image
* considers it OK if names do not match. */
if (r == -ENOENT) {
_cleanup_free_ char *extension_release_dir_path = NULL;
_cleanup_closedir_ DIR *extension_release_dir = NULL;
r = chase_symlinks_and_opendir("/usr/lib/extension-release.d/", root, CHASE_PREFIX_ROOT,
&extension_release_dir_path, &extension_release_dir);
if (r < 0)
return r;
r = -ENOENT;
struct dirent *de;
FOREACH_DIRENT(de, extension_release_dir, return -errno) {
int k;
if (!IN_SET(de->d_type, DT_REG, DT_UNKNOWN))
continue;
const char *image_name = startswith(de->d_name, "extension-release.");
if (!image_name)
continue;
if (!image_name_is_valid(image_name))
continue;
/* We already chased the directory, and checked that
* this is a real file, so we shouldn't fail to open it. */
_cleanup_close_ int extension_release_fd = openat(dirfd(extension_release_dir),
de->d_name,
O_PATH|O_CLOEXEC|O_NOFOLLOW);
if (extension_release_fd < 0)
return log_debug_errno(errno,
"Failed to open extension-release file %s/%s: %m",
extension_release_dir_path,
de->d_name);
/* Really ensure it is a regular file after we open it. */
if (fd_verify_regular(extension_release_fd) < 0)
continue;
/* No xattr or cannot parse it? Then skip this. */
_cleanup_free_ char *extension_release_xattr = NULL;
k = fgetxattrat_fake_malloc(extension_release_fd, NULL, "user.extension-release.strict", AT_EMPTY_PATH, &extension_release_xattr);
if (k < 0 && !ERRNO_IS_NOT_SUPPORTED(k) && k != -ENODATA)
log_debug_errno(k,
"Failed to read 'user.extension-release.strict' extended attribute from extension-release file %s/%s: %m",
extension_release_dir_path,
de->d_name);
if (k < 0)
continue;
/* Explicitly set to request strict matching? Skip it. */
k = parse_boolean(extension_release_xattr);
if (k < 0)
log_debug_errno(k,
"Failed to parse 'user.extension-release.strict' extended attribute value from extension-release file %s/%s: %m",
extension_release_dir_path,
de->d_name);
if (k < 0 || k > 0)
continue;
/* We already found what we were looking for, but there's another candidate?
* We treat this as an error, as we want to enforce that there are no ambiguities
* in case we are in the fallback path.*/
if (r == 0) {
r = -ENOTUNIQ;
break;
}
r = 0; /* Found it! */
if (ret_fd)
fd = TAKE_FD(extension_release_fd);
if (ret_path) {
q = path_join(extension_release_dir_path, de->d_name);
if (!q)
return -ENOMEM;
}
}
}
} else {
const char *p;
src/shared/dissect-image.c
+23 -20
View File
@@ -2538,13 +2538,13 @@ int dissected_image_acquire_metadata(DissectedImage *m) {
_META_MAX,
};
static const char *paths[_META_MAX] = {
static const char *const paths[_META_MAX] = {
[META_HOSTNAME] = "/etc/hostname\0",
[META_MACHINE_ID] = "/etc/machine-id\0",
[META_MACHINE_INFO] = "/etc/machine-info\0",
[META_OS_RELEASE] = "/etc/os-release\0"
"/usr/lib/os-release\0",
[META_EXTENSION_RELEASE] = NULL,
[META_OS_RELEASE] = ("/etc/os-release\0"
"/usr/lib/os-release\0"),
[META_EXTENSION_RELEASE] = "extension-release\0", /* Used only for logging. */
};
_cleanup_strv_free_ char **machine_info = NULL, **os_release = NULL, **extension_release = NULL;
@@ -2561,17 +2561,6 @@ int dissected_image_acquire_metadata(DissectedImage *m) {
assert(m);
/* As per the os-release spec, if the image is an extension it will have a file
* named after the image name in extension-release.d/ */
if (m->image_name) {
char *ext;
ext = strjoina("/usr/lib/extension-release.d/extension-release.", m->image_name, "0");
ext[strlen(ext) - 1] = '\0'; /* Extra \0 for NULSTR_FOREACH using placeholder from above */
paths[META_EXTENSION_RELEASE] = ext;
} else
log_debug("No image name available, will skip extension-release metadata");
for (; n_meta_initialized < _META_MAX; n_meta_initialized ++) {
if (!paths[n_meta_initialized]) {
fds[2*n_meta_initialized] = fds[2*n_meta_initialized+1] = -1;
@@ -2625,11 +2614,25 @@ int dissected_image_acquire_metadata(DissectedImage *m) {
fds[2*k] = safe_close(fds[2*k]);
NULSTR_FOREACH(p, paths[k]) {
fd = chase_symlinks_and_open(p, t, CHASE_PREFIX_ROOT, O_RDONLY|O_CLOEXEC|O_NOCTTY, NULL);
if (fd >= 0)
break;
}
if (k == META_EXTENSION_RELEASE) {
/* As per the os-release spec, if the image is an extension it will have a file
* named after the image name in extension-release.d/ - we use the image name
* and try to resolve it with the extension-release helpers, as sometimes
* the image names are mangled on deployment and do not match anymore.
* Unlike other paths this is not fixed, and the image name
* can be mangled on deployment, so by calling into the helper
* we allow a fallback that matches on the first extension-release
* file found in the directory, if one named after the image cannot
* be found first. */
r = open_extension_release(t, m->image_name, NULL, &fd);
if (r < 0)
fd = r; /* Propagate the error. */
} else
NULSTR_FOREACH(p, paths[k]) {
fd = chase_symlinks_and_open(p, t, CHASE_PREFIX_ROOT, O_RDONLY|O_CLOEXEC|O_NOCTTY, NULL);
if (fd >= 0)
break;
}
if (fd < 0) {
log_debug_errno(fd, "Failed to read %s file of image, ignoring: %m", paths[k]);
fds[2*k+1] = safe_close(fds[2*k+1]);