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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "chase-symlinks.h"
#include "fd-util.h"
#include "fileio.h"
#include "string-util.h"
#include "uid-alloc-range.h"
#include "user-util.h"
static const UGIDAllocationRange default_ugid_allocation_range = {
.system_alloc_uid_min = SYSTEM_ALLOC_UID_MIN,
.system_uid_max = SYSTEM_UID_MAX,
.system_alloc_gid_min = SYSTEM_ALLOC_GID_MIN,
.system_gid_max = SYSTEM_GID_MAX,
};
#if ENABLE_COMPAT_MUTABLE_UID_BOUNDARIES
static int parse_alloc_uid(const char *path, const char *name, const char *t, uid_t *ret_uid) {
uid_t uid;
int r;
r = parse_uid(t, &uid);
if (r < 0)
return log_debug_errno(r, "%s: failed to parse %s %s, ignoring: %m", path, name, t);
if (uid == 0)
uid = 1;
*ret_uid = uid;
return 0;
}
#endif
int read_login_defs(UGIDAllocationRange *ret_defs, const char *path, const char *root) {
#if ENABLE_COMPAT_MUTABLE_UID_BOUNDARIES
_cleanup_fclose_ FILE *f = NULL;
UGIDAllocationRange defs;
int r;
if (!path)
path = "/etc/login.defs";
r = chase_symlinks_and_fopen_unlocked(path, root, CHASE_PREFIX_ROOT, "re", NULL, &f);
if (r == -ENOENT)
goto defaults;
if (r < 0)
return log_debug_errno(r, "Failed to open %s: %m", path);
defs = default_ugid_allocation_range;
for (;;) {
_cleanup_free_ char *line = NULL;
char *t;
r = read_line(f, LINE_MAX, &line);
if (r < 0)
return log_debug_errno(r, "Failed to read %s: %m", path);
if (r == 0)
break;
if ((t = first_word(line, "SYS_UID_MIN")))
(void) parse_alloc_uid(path, "SYS_UID_MIN", t, &defs.system_alloc_uid_min);
else if ((t = first_word(line, "SYS_UID_MAX")))
(void) parse_alloc_uid(path, "SYS_UID_MAX", t, &defs.system_uid_max);
else if ((t = first_word(line, "SYS_GID_MIN")))
(void) parse_alloc_uid(path, "SYS_GID_MIN", t, &defs.system_alloc_gid_min);
else if ((t = first_word(line, "SYS_GID_MAX")))
(void) parse_alloc_uid(path, "SYS_GID_MAX", t, &defs.system_gid_max);
}
if (defs.system_alloc_uid_min > defs.system_uid_max) {
log_debug("%s: SYS_UID_MIN > SYS_UID_MAX, resetting.", path);
defs.system_alloc_uid_min = MIN(defs.system_uid_max - 1, (uid_t) SYSTEM_ALLOC_UID_MIN);
/* Look at sys_uid_max to make sure sys_uid_min..sys_uid_max remains a valid range. */
}
if (defs.system_alloc_gid_min > defs.system_gid_max) {
log_debug("%s: SYS_GID_MIN > SYS_GID_MAX, resetting.", path);
defs.system_alloc_gid_min = MIN(defs.system_gid_max - 1, (gid_t) SYSTEM_ALLOC_GID_MIN);
/* Look at sys_gid_max to make sure sys_gid_min..sys_gid_max remains a valid range. */
}
*ret_defs = defs;
return 1;
defaults:
#endif
*ret_defs = default_ugid_allocation_range;
return 0;
}
const UGIDAllocationRange *acquire_ugid_allocation_range(void) {
#if ENABLE_COMPAT_MUTABLE_UID_BOUNDARIES
static thread_local UGIDAllocationRange defs;
static thread_local int initialized = 0; /* == 0 → not initialized yet
* < 0 → failure
* > 0 → success */
/* This function will ignore failure to read the file, so it should only be called from places where
* we don't crucially depend on the answer. In other words, it's appropriate for journald, but
* probably not for sysusers. */
if (initialized == 0)
initialized = read_login_defs(&defs, NULL, NULL) < 0 ? -1 : 1;
if (initialized < 0)
return &default_ugid_allocation_range;
return &defs;
#endif
return &default_ugid_allocation_range;
}
bool uid_is_system(uid_t uid) {
const UGIDAllocationRange *defs;
assert_se(defs = acquire_ugid_allocation_range());
return uid <= defs->system_uid_max;
}
bool gid_is_system(gid_t gid) {
const UGIDAllocationRange *defs;
assert_se(defs = acquire_ugid_allocation_range());
return gid <= defs->system_gid_max;
}
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