login.defs: Add LASTLOG_UID_MAX variable to limit lastlog to small uids.

As the large uids are usually provided by remote user identity and
authentication service, which also provide user login tracking,
there is no need to create a huge sparse file for them on every local
machine.

fixup! login.defs: Add LASTLOG_UID_MAX variable to limit lastlog to small uids.

lib/getdef.c

@@ -92,6 +92,7 @@ static struct itemdef def_table[] = {
 	{"GID_MIN", NULL},
 	{"HUSHLOGIN_FILE", NULL},
 	{"KILLCHAR", NULL},
+	{"LASTLOG_UID_MAX", NULL},
 	{"LOGIN_RETRIES", NULL},
 	{"LOGIN_TIMEOUT", NULL},
 	{"LOG_OK_LOGINS", NULL},

man/Makefile.am

@@ -137,6 +137,7 @@ login_defs_v = \
 	ISSUE_FILE.xml \
 	KILLCHAR.xml \
 	LASTLOG_ENAB.xml \
+	LASTLOG_UID_MAX.xml \
 	LOGIN_RETRIES.xml \
 	LOGIN_STRING.xml \
 	LOGIN_TIMEOUT.xml \

man/lastlog.8.xml

@@ -31,6 +31,7 @@
 -->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
+<!ENTITY LASTLOG_UID_MAX       SYSTEM "login.defs.d/LASTLOG_UID_MAX.xml">
 <!-- SHADOW-CONFIG-HERE -->
 ]>
 <refentry id='lastlog.8'>
@@ -200,6 +201,18 @@
     </para>
   </refsect1>
 
+  <refsect1 id='configuration'>
+    <title>CONFIGURATION</title>
+    <para>
+      The following configuration variables in
+      <filename>/etc/login.defs</filename> change the behavior of this
+      tool:
+    </para>
+    <variablelist>
+      &LASTLOG_UID_MAX;
+    </variablelist>
+  </refsect1>
+
   <refsect1 id='files'>
     <title>FILES</title>
     <variablelist>

man/login.defs.5.xml

@@ -54,6 +54,7 @@
 <!ENTITY ISSUE_FILE            SYSTEM "login.defs.d/ISSUE_FILE.xml">
 <!ENTITY KILLCHAR              SYSTEM "login.defs.d/KILLCHAR.xml">
 <!ENTITY LASTLOG_ENAB          SYSTEM "login.defs.d/LASTLOG_ENAB.xml">
+<!ENTITY LASTLOG_UID_MAX       SYSTEM "login.defs.d/LASTLOG_UID_MAX.xml">
 <!ENTITY LOG_OK_LOGINS         SYSTEM "login.defs.d/LOG_OK_LOGINS.xml">
 <!ENTITY LOG_UNKFAIL_ENAB      SYSTEM "login.defs.d/LOG_UNKFAIL_ENAB.xml">
 <!ENTITY LOGIN_RETRIES         SYSTEM "login.defs.d/LOGIN_RETRIES.xml">
@@ -188,6 +189,7 @@
       &ISSUE_FILE;
       &KILLCHAR;
       &LASTLOG_ENAB;
+      &LASTLOG_UID_MAX;
       &LOG_OK_LOGINS;
       &LOG_UNKFAIL_ENAB;
       &LOGIN_RETRIES;
@@ -349,7 +351,12 @@
 	</listitem>
       </varlistentry>
       <!-- id: no variables -->
-      <!-- lastlog: no variables -->
+      <varlistentry>
+	<term>lastlog</term>
+	<listitem>
+	  <para>LASTLOG_UID_MAX</para>
+	</listitem>
+      </varlistentry>
       <varlistentry>
 	<term>login</term>
 	<listitem>
@@ -365,7 +372,7 @@
 	    HUSHLOGIN_FILE
 	    <phrase condition="no_pam">ISSUE_FILE</phrase>
 	    KILLCHAR
-	    <phrase condition="no_pam">LASTLOG_ENAB</phrase>
+	    <phrase condition="no_pam">LASTLOG_ENAB LASTLOG_UID_MAX</phrase>
 	    LOGIN_RETRIES
 	    <phrase condition="no_pam">LOGIN_STRING</phrase>
 	    LOGIN_TIMEOUT LOG_OK_LOGINS LOG_UNKFAIL_ENAB
@@ -474,6 +481,7 @@
 	  <para>
 	    CREATE_HOME
 	    GID_MAX GID_MIN
+	    LASTLOG_UID_MAX
 	    MAIL_DIR MAX_MEMBERS_PER_GROUP
 	    PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE
 	    SUB_GID_COUNT SUB_GID_MAX SUB_GID_MIN
@@ -498,6 +506,7 @@
 	<term>usermod</term>
 	<listitem>
 	  <para>
+	    LASTLOG_UID_MAX
 	    MAIL_DIR MAIL_FILE MAX_MEMBERS_PER_GROUP
 	    <phrase condition="tcb">TCB_SYMLINKS USE_TCB</phrase>
 	  </para>

man/login.defs.d/LASTLOG_UID_MAX.xml

@@ -0,0 +1,46 @@
+<!--
+   Copyright (c) 1991 - 1993, Julianne Frances Haugh
+   Copyright (c) 1991 - 1993, Chip Rosenthal
+   Copyright (c) 2007 - 2008, Nicolas François
+   Copyright (c) 2018, Red Hat, inc.
+   All rights reserved.
+
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions
+   are met:
+   1. Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+   2. Redistributions in binary form must reproduce the above copyright
+      notice, this list of conditions and the following disclaimer in the
+      documentation and/or other materials provided with the distribution.
+   3. The name of the copyright holders or contributors may not be used to
+      endorse or promote products derived from this software without
+      specific prior written permission.
+  
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+   ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+   PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
+   HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+-->
+<varlistentry>
+  <term><option>LASTLOG_UID_MAX</option> (number)</term>
+  <listitem>
+    <para>
+      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.
+    </para>
+    <para>
+      No <option>LASTLOG_UID_MAX</option> option present in the configuration
+      means that there is no user ID limit for writing lastlog entries.
+    </para>
+  </listitem>
+</varlistentry>

man/useradd.8.xml

@@ -32,6 +32,7 @@
   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
 <!ENTITY CREATE_HOME           SYSTEM "login.defs.d/CREATE_HOME.xml">
 <!ENTITY GID_MAX               SYSTEM "login.defs.d/GID_MAX.xml">
+<!ENTITY LASTLOG_UID_MAX       SYSTEM "login.defs.d/LASTLOG_UID_MAX.xml">
 <!ENTITY MAIL_DIR              SYSTEM "login.defs.d/MAIL_DIR.xml">
 <!ENTITY MAX_MEMBERS_PER_GROUP SYSTEM "login.defs.d/MAX_MEMBERS_PER_GROUP.xml">
 <!ENTITY PASS_MAX_DAYS         SYSTEM "login.defs.d/PASS_MAX_DAYS.xml">
@@ -670,6 +671,7 @@
     <variablelist>
       &CREATE_HOME;
       &GID_MAX; <!-- documents also GID_MIN -->
+      &LASTLOG_UID_MAX;
       &MAIL_DIR;
       &MAX_MEMBERS_PER_GROUP;
       &PASS_MAX_DAYS;

man/usermod.8.xml

@@ -30,6 +30,7 @@
 -->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
+<!ENTITY LASTLOG_UID_MAX       SYSTEM "login.defs.d/LASTLOG_UID_MAX.xml">
 <!ENTITY MAIL_DIR              SYSTEM "login.defs.d/MAIL_DIR.xml">
 <!ENTITY MAX_MEMBERS_PER_GROUP SYSTEM "login.defs.d/MAX_MEMBERS_PER_GROUP.xml">
 <!ENTITY SUB_GID_COUNT         SYSTEM "login.defs.d/SUB_GID_COUNT.xml">
@@ -517,6 +518,7 @@
       tool:
     </para>
     <variablelist>
+      &LASTLOG_UID_MAX;
       &MAIL_DIR; <!-- documents also MAIL_FILE -->
       &MAX_MEMBERS_PER_GROUP;
       &SUB_GID_COUNT; <!-- documents also SUB_GID_MAX and SUB_GID_MIN -->

src/lastlog.c

@@ -44,6 +44,7 @@
 #include <assert.h>
 #include "defines.h"
 #include "prototypes.h"
+#include "getdef.h"
 /*@-exitarg@*/
 #include "exitcodes.h"
 
@@ -182,6 +183,15 @@ static void print_one (/*@null@*/const struct passwd *pw)
 static void print (void)
 {
 	const struct passwd *pwent;
+	unsigned long lastlog_uid_max;
+
+	lastlog_uid_max = getdef_ulong ("LASTLOG_UID_MAX", 0xFFFFFFFFUL);
+	if (   (has_umin && umin > lastlog_uid_max)
+	    || (has_umax && umax > lastlog_uid_max)) {
+		fprintf (stderr, _("%s: Selected uid(s) are higher than LASTLOG_UID_MAX (%lu),\n"
+				   "\tthe output might be incorrect.\n"), Prog, lastlog_uid_max);
+	}
+
 	if (uflg && has_umin && has_umax && (umin == umax)) {
 		print_one (getpwuid ((uid_t)umin));
 	} else {
@@ -191,6 +201,8 @@ static void print (void)
 			    && (   (has_umin && (pwent->pw_uid < (uid_t)umin))
 			        || (has_umax && (pwent->pw_uid > (uid_t)umax)))) {
 				continue;
+			} else if ( !uflg && pwent->pw_uid > (uid_t) lastlog_uid_max) {
+				continue;
 			}
 			print_one (pwent);
 		}
@@ -246,10 +258,19 @@ static void update_one (/*@null@*/const struct passwd *pw)
 static void update (void)
 {
 	const struct passwd *pwent;
+	unsigned long lastlog_uid_max;
 
 	if (!uflg) /* safety measure */
 		return;
 
+	lastlog_uid_max = getdef_ulong ("LASTLOG_UID_MAX", 0xFFFFFFFFUL);
+	if (   (has_umin && umin > lastlog_uid_max)
+	    || (has_umax && umax > lastlog_uid_max)) {
+		fprintf (stderr, _("%s: Selected uid(s) are higher than LASTLOG_UID_MAX (%lu),\n"
+				   "\tthey will not be updated.\n"), Prog, lastlog_uid_max);
+		return;
+	}
+
 	if (has_umin && has_umax && (umin == umax)) {
 		update_one (getpwuid ((uid_t)umin));
 	} else {

src/login.c

@@ -1162,7 +1162,9 @@ int main (int argc, char **argv)
 #endif				/* WITH_AUDIT */
 
 #ifndef USE_PAM			/* pam_lastlog handles this */
-	if (getdef_bool ("LASTLOG_ENAB")) {	/* give last login and log this one */
+	if (   getdef_bool ("LASTLOG_ENAB")
+	    && pwd->pw_uid <= (uid_t) getdef_ulong ("LASTLOG_UID_MAX", 0xFFFFFFFFUL)) {
+		/* give last login and log this one */
 		dolastlog (&ll, pwd, tty, hostname);
 	}
 #endif
@@ -1298,6 +1300,7 @@ int main (int argc, char **argv)
 			}
 		}
 		if (   getdef_bool ("LASTLOG_ENAB")
+		    && pwd->pw_uid <= (uid_t) getdef_ulong ("LASTLOG_UID_MAX", 0xFFFFFFFFUL)
 		    && (ll.ll_time != 0)) {
 			time_t ll_time = ll.ll_time;
 

src/useradd.c

@@ -1863,11 +1863,18 @@ static void lastlog_reset (uid_t uid)
 	struct lastlog ll;
 	int fd;
 	off_t offset_uid = (off_t) (sizeof ll) * uid;
+	uid_t max_uid;
 
 	if (access (LASTLOG_FILE, F_OK) != 0) {
 		return;
 	}
 
+	max_uid = (uid_t) getdef_ulong ("LASTLOG_UID_MAX", 0xFFFFFFFFUL);
+	if (uid > max_uid) {
+		/* do not touch lastlog for large uids */
+		return;
+	}
+
 	memzero (&ll, sizeof (ll));
 
 	fd = open (LASTLOG_FILE, O_RDWR);

src/usermod.c

@@ -1864,11 +1864,18 @@ static void update_lastlog (void)
 	int fd;
 	off_t off_uid = (off_t) user_id * sizeof ll;
 	off_t off_newuid = (off_t) user_newid * sizeof ll;
+	uid_t max_uid;
 
 	if (access (LASTLOG_FILE, F_OK) != 0) {
 		return;
 	}
 
+	max_uid = (uid_t) getdef_ulong ("LASTLOG_MAX_UID", 0xFFFFFFFFUL);
+	if (user_newid > max_uid) {
+		/* do not touch lastlog for large uids */
+		return;
+	}
+
 	fd = open (LASTLOG_FILE, O_RDWR);
 
 	if (-1 == fd) {