Hello David,
On 12/10/21 23:54, David C. Rankin wrote:
Dear usermod man page maintainers,
There is an error in the description of the option for:
-e, --expiredate EXPIRE_DATE
The man page states:
An empty EXPIRE_DATE argument will disable the expiration of the account.
This is incorrect. The EXPIRE_DATE argument CANNOT be empty or it will take
the LOGIN as the value for the EXPIRE_DATE.
Instead, the correct use is "-e -1" or "--expiredate -1" where "-1" (-one)
is provided as the EXPIRE_DATE value.
See, e.g.: https://stackoverflow.com/a/30769911/3422102
Thanks for the report.
I tried a few combinations that allow to pass an empty argument to the
expiredate option.
From a terminal, I expire the password (and check it) with:
$ sudo usermod -e 1 alx
$ su alx
Password:
Your account has expired; please contact your system administrator.
su: Authentication failure
$
Then from another terminal (logged in as root), I re-enable it, with
either of the following:
# usermod -e '' alx
# usermod --expiredate= alx
And then I can log in correctly:
$ su alx
Password:
$
I commented on the stackoverflow post with this info.
Cheers,
Alex
See some more details below:
===========
https://github.com/shadow-maint/shadow/tree/master
is the source code for the passwd package available in Debian.
Parsing the options and arguments in <src/usermod.c>:
case 'e':
if ('\0' != *optarg) {
user_newexpire = strtoday (optarg);
if (user_newexpire < -1) {
fprintf (stderr,
_("%s: invalid date '%s'\n"),
Prog, optarg);
exit (E_BAD_ARG);
}
user_newexpire *= DAY / SCALE;
} else {
user_newexpire = -1;
}
eflg = true;
break;
So both '' and '-1' are treated in the same way,
but '-1' is undocumented.
I'm wondering what other undocumented formats are accepted,
since I succeeded with a positive number,
which is also undocumented,
so let's see strtoday():
/*
* strtoday() now uses get_date() (borrowed from GNU shellutils)
* which can handle many date formats, for example:
* 1970-09-17 # ISO 8601.
* 70-9-17 # This century assumed by default.
* 70-09-17 # Leading zeros are ignored.
* 9/17/72 # Common U.S. writing.
* 24 September 1972
* 24 Sept 72 # September has a special abbreviation.
* 24 Sep 72 # Three-letter abbreviations always allowed.
* Sep 24, 1972
* 24-sep-72
* 24sep72
*/
long strtoday (const char *str)
{
time_t t;
bool isnum = true;
const char *s = str;
/*
* get_date() interprets an empty string as the current date,
* which is not what we expect, unless you're a BOFH :-).
* (useradd sets sp_expire = current date for new lusers)
*/
if ((NULL == str) || ('\0' == *str)) {
return -1;
}
/* If a numerical value is provided, this is already a number of
* days since EPOCH.
*/
if ('-' == *s) {
s++;
}
while (' ' == *s) {
s++;
}
while (isnum && ('\0' != *s)) {
if (!isdigit (*s)) {
isnum = false;
}
s++;
}
if (isnum) {
long retdate;
if (getlong (str, &retdate) == 0) {
return -2;
}
return retdate;
}
t = get_date (str, NULL);
if ((time_t) - 1 == t) {
return -2;
}
/* convert seconds to days since 1970-01-01 */
return (long) (t + DAY / 2) / DAY;
}
So a simple number is "day since the Epoch".
Other accepted formats are in the comment above the function.
BTW, since this function understands "" as -1,
the parsing in <src/usermod.c> could be simplified
(remove the special case for ""),
so I'll send a patch for that.
static void date_to_str (/*@unique@*//*@out@*/char *buf, size_t maxsize,
long int date)
{
struct tm *tp;
if (date < 0) {
strncpy (buf, "never", maxsize);
} else {
time_t t = (time_t) date;
tp = gmtime (&t);
#ifdef HAVE_STRFTIME
strftime (buf, maxsize, "%Y-%m-%d", tp);
#else
(void) snprintf (buf, maxsize, "%04d-%02d-%02d",
tp->tm_year + 1900,
tp->tm_mon + 1,
tp->tm_mday);
#endif /* HAVE_STRFTIME */
}
buf[maxsize - 1] = '\0';
}
Then, the number is converted back to string,
and '-1' means 'never', as you said.
--
Alejandro Colomar
Linux man-pages comaintainer; http://www.kernel.org/doc/man-pages/
