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util-lib: add a comment explaining the user name rules we enforce

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This commit is contained in:
Lennart Poettering 2016-12-27 17:59:21 +01:00
parent 27e2e3231f
commit 1429dfe5f8
1 changed files with 11 additions and 1 deletions
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12
src/basic/user-util.c
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@ -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;