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basic/unit-file: split out the subroutine for symlink verification

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The old logs used __func__, but this doesn't make sense now, because the
low-level function will be used in other places. So those are adjusted to be
more generic.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2022-03-02 16:53:54 +01:00
parent 43a5fd98a5
commit 9825181143
1 changed files with 98 additions and 65 deletions
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163
src/basic/unit-file.c
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@ -259,6 +259,83 @@ static int directory_name_is_valid(const char *name) {
return false;
}
static int unit_file_resolve_symlink(
const char *root_dir,
char **search_path,
const char *dir,
int dirfd,
const char *filename,
char **ret_destination) {
_cleanup_free_ char *target = NULL, *simplified = NULL, *dst = NULL;
int r;
assert(dir);
assert(dirfd >= 0);
assert(filename);
assert(ret_destination);
r = readlinkat_malloc(dirfd, filename, &target);
if (r < 0)
return log_warning_errno(r, "Failed to read symlink %s%s%s: %m",
dir, dir ? "/" : "", filename);
bool is_abs = path_is_absolute(target);
if (root_dir || !is_abs) {
char *target_abs = path_join(is_abs ? root_dir : dir, target);
if (!target_abs)
return log_oom();
free_and_replace(target, target_abs);
}
/* Get rid of "." and ".." components in target path */
r = chase_symlinks(target, root_dir, CHASE_NOFOLLOW | CHASE_NONEXISTENT, &simplified, NULL);
if (r < 0)
return log_warning_errno(r, "Failed to resolve symlink %s/%s pointing to %s: %m",
dir, filename, target);
/* Check if the symlink goes outside of our search path.
* If yes, it's a linked unit file or mask, and we don't care about the target name.
* Let's just store the link source directly.
* If not, let's verify that it's a good symlink. */
const char *tail = path_startswith_strv(simplified, search_path);
if (!tail) {
log_debug("Linked unit file: %s/%s → %s", dir, filename, simplified);
dst = path_join(dir, filename);
if (!dst)
return log_oom();
} else {
r = path_extract_filename(simplified, &dst);
if (r < 0)
return r;
bool self_alias = streq(dst, filename);
if (is_path(tail))
log_full(self_alias ? LOG_DEBUG : LOG_WARNING,
"Suspicious symlink %s/%s→%s, treating as alias.",
dir, filename, simplified);
r = unit_validate_alias_symlink_and_warn(filename, simplified);
if (r < 0)
return r;
if (self_alias)
/* A self-alias that has no effect */
return log_debug_errno(SYNTHETIC_ERRNO(ELOOP),
"Unit file self-alias: %s/%s → %s, ignoring.",
dir, filename, dst);
log_debug("Unit file alias: %s/%s → %s", dir, filename, dst);
}
*ret_destination = TAKE_PTR(dst);
return 0;
}
int unit_file_build_name_map(
const LookupPaths *lp,
uint64_t *cache_timestamp_hash,
@ -308,10 +385,9 @@ int unit_file_build_name_map(
FOREACH_DIRENT_ALL(de, d, log_warning_errno(errno, "Failed to read \"%s\", ignoring: %m", *dir)) {
_unused_ _cleanup_free_ char *_filename_free = NULL;
_cleanup_free_ char *simplified = NULL;
bool symlink_to_dir = false;
const char *dst = NULL;
char *filename;
_cleanup_free_ char *dst = NULL;
bool symlink_to_dir = false;
/* We only care about valid units and dirs with certain suffixes, let's ignore the
* rest. */
@ -395,77 +471,34 @@ int unit_file_build_name_map(
/* We don't explicitly check for alias loops here. unit_ids_map_get() which
* limits the number of hops should be used to access the map. */
_cleanup_free_ char *target = NULL;
r = readlinkat_malloc(dirfd(d), de->d_name, &target);
if (r < 0) {
log_warning_errno(r, "Failed to read symlink %s/%s, ignoring: %m",
*dir, de->d_name);
r = unit_file_resolve_symlink(lp->root_dir, lp->search_path,
*dir, dirfd(d), de->d_name,
&dst);
if (r == -ENOMEM)
return r;
if (r < 0) /* we ignore other errors here */
continue;
}
const bool is_abs = path_is_absolute(target);
if (lp->root_dir || !is_abs) {
char *target_abs = path_join(is_abs ? lp->root_dir : *dir, target);
if (!target_abs)
return log_oom();
free_and_replace(target, target_abs);
}
/* Get rid of "." and ".." components in target path */
r = chase_symlinks(target, lp->root_dir, CHASE_NOFOLLOW | CHASE_NONEXISTENT, &simplified, NULL);
if (r < 0) {
log_warning_errno(r, "Failed to resolve symlink %s pointing to %s, ignoring: %m",
filename, target);
continue;
}
/* Check if the symlink goes outside of our search path.
* If yes, it's a linked unit file or mask, and we don't care about the target name.
* Let's just store the link source directly.
* If not, let's verify that it's a good symlink. */
char *tail = path_startswith_strv(simplified, lp->search_path);
if (!tail) {
log_debug("%s: linked unit file: %s → %s",
__func__, filename, simplified);
dst = filename;
} else {
bool self_alias;
dst = basename(simplified);
self_alias = streq(dst, de->d_name);
if (is_path(tail))
log_full(self_alias ? LOG_DEBUG : LOG_WARNING,
"Suspicious symlink %s→%s, treating as alias.",
filename, simplified);
r = unit_validate_alias_symlink_and_warn(filename, simplified);
if (r < 0)
continue;
if (self_alias) {
/* A self-alias that has no effect */
log_debug("%s: self-alias: %s/%s → %s, ignoring.",
__func__, *dir, de->d_name, dst);
continue;
}
log_debug("%s: alias: %s/%s → %s", __func__, *dir, de->d_name, dst);
}
} else {
dst = filename;
dst = TAKE_PTR(_filename_free); /* Grab the copy we made previously, if available. */
if (!dst) {
dst = strdup(filename);
if (!dst)
return log_oom();
}
log_debug("%s: normal unit file: %s", __func__, dst);
}
r = hashmap_put_strdup(&ids, de->d_name, dst);
_cleanup_free_ char *key = strdup(de->d_name);
if (!key)
return log_oom();
r = hashmap_ensure_put(&ids, &string_hash_ops_free_free, key, dst);
if (r < 0)
return log_warning_errno(r, "Failed to add entry to hashmap (%s→%s): %m",
de->d_name, dst);
key = dst = NULL;
}
}