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authorLennart Poettering <lennart@poettering.net>2016-12-27 17:59:21 +0100
committerLennart Poettering <lennart@poettering.net>2016-12-27 18:09:58 +0100
commit1429dfe5f8d0e4d2dcc73d1702510697880a46de (patch)
tree3c0d87718c99cebce33bd52e035002e13e30ad48
parent27e2e3231fc1edbbaa9f73be363900701ab4598d (diff)
util-lib: add a comment explaining the user name rules we enforce
-rw-r--r--src/basic/user-util.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/src/basic/user-util.c b/src/basic/user-util.c
index 938533d2e7..c619dad527 100644
--- a/src/basic/user-util.c
+++ b/src/basic/user-util.c
@@ -46,6 +46,8 @@
bool uid_is_valid(uid_t uid) {
+ /* Also see POSIX IEEE Std 1003.1-2008, 2016 Edition, 3.436. */
+
/* Some libc APIs use UID_INVALID as special placeholder */
if (uid == (uid_t) UINT32_C(0xFFFFFFFF))
return false;
@@ -519,7 +521,15 @@ bool valid_user_group_name(const char *u) {
const char *i;
long sz;
- /* Checks if the specified name is a valid user/group name. */
+ /* Checks if the specified name is a valid user/group name. Also see POSIX IEEE Std 1003.1-2008, 2016 Edition,
+ * 3.437. We are a bit stricter here however. Specifically we deviate from POSIX rules:
+ *
+ * - We don't allow any dots (this would break chown syntax which permits dots as user/group name separator)
+ * - We require that names fit into the appropriate utmp field
+ * - We don't allow empty user names
+ *
+ * Note that other systems are even more restrictive, and don't permit underscores or uppercase characters.
+ */
if (isempty(u))
return false;