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-rw-r--r--src/shared/uid-alloc-range.c124
1 files changed, 124 insertions, 0 deletions
diff --git a/src/shared/uid-alloc-range.c b/src/shared/uid-alloc-range.c
new file mode 100644
index 0000000..1953119
--- /dev/null
+++ b/src/shared/uid-alloc-range.c
@@ -0,0 +1,124 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "chase-symlinks.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "missing_threads.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;
+}