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login: add support for login.defs(5) LASTLOG_UID_MAX 

This new variable allows to keep lastlog file small and filter out
things like huge nfsnobody UIDs.

The variable is also supported by shadow-utils (adduser, etc.).

Addresses: https://github.com/shadow-maint/shadow/pull/142/
Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2019-01-11 12:16:00 +01:00
parent 623427456e
commit 1a83c00d88
2 changed files with 14 additions and 0 deletions
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11
login-utils/login.1
View File

@ -256,6 +256,17 @@ to change directory to her home. The default value is
.IR yes .
.RE
.PP
.B LASTLOG_UID_MAX
(unsigned number)
.RS 4
Highest user ID number for which the lastlog entries should be
updated. As higher user IDs are usually tracked by remote user
identity and authentication services there is no need to create
a huge sparse lastlog file for them. No LASTLOG_UID_MAX option
present in the configuration means that there is no user ID limit
for writing lastlog entries.
.RE
.PP
.B LOG_UNKFAIL_ENAB
(boolean)
.RS 4

3
login-utils/login.c
View File

@ -503,6 +503,9 @@ static void log_lastlog(struct login_context *cxt)
if (!cxt->pwd)
return;
if (cxt->pwd->pw_uid > (uid_t) getlogindefs_num("LASTLOG_UID_MAX", ULONG_MAX))
return;
/* lastlog is huge on systems with large UIDs, ignore SIGXFSZ */
memset(&sa, 0, sizeof(sa));
sa.sa_handler = SIG_IGN;