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shadow/libmisc/limits.c

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C
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/*
* SPDX-FileCopyrightText: 1989 - 1994, Julianne Frances Haugh
* SPDX-FileCopyrightText: 1996 - 1999, Marek Michałkiewicz
* SPDX-FileCopyrightText: 2003 - 2006, Tomasz Kłoczko
* SPDX-FileCopyrightText: 2007 - 2010, Nicolas François
*
* SPDX-License-Identifier: BSD-3-Clause
*/
/*
* Separated from setup.c. --marekm
* Resource limits thanks to Cristian Gafton.
* Enhancements of resource limit code by Thomas Orgis <thomas@orgis.org>
*/
#include <config.h>
#ifndef USE_PAM
#ident "$Id$"
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <ctype.h>
#include "prototypes.h"
#include "defines.h"
#include <pwd.h>
#include "getdef.h"
#ifdef HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#define LIMITS
#endif
#ifdef LIMITS
#ifndef LIMITS_FILE
#define LIMITS_FILE "/etc/limits"
#endif
#define LOGIN_ERROR_RLIMIT 1
#define LOGIN_ERROR_LOGIN 2
/* Set a limit on a resource */
/*
* rlimit - RLIMIT_XXXX
* value - string value to be read
* multiplier - value*multiplier is the actual limit
*/
static int setrlimit_value (unsigned int resource,
const char *value,
unsigned int multiplier)
{
struct rlimit rlim;
rlim_t limit;
/* The "-" is special, not belonging to a strange negative limit.
* It is infinity, in a controlled way.
*/
if ('-' == value[0]) {
limit = RLIM_INFINITY;
}
else {
/* We cannot use getlong here because it fails when there
* is more to the value than just this number!
* Also, we are limited to base 10 here (hex numbers will not
* work with the limit string parser as is anyway)
*/
char *endptr;
long longlimit = strtol (value, &endptr, 10);
if ((0 == longlimit) && (value == endptr)) {
/* No argument at all. No-op.
* FIXME: We could instead throw an error, though.
*/
return 0;
}
longlimit *= multiplier;
limit = (rlim_t)longlimit;
if (longlimit != limit)
{
/* FIXME: Again, silent error handling...
* Wouldn't screaming make more sense?
*/
return 0;
}
}
rlim.rlim_cur = limit;
rlim.rlim_max = limit;
if (setrlimit (resource, &rlim) != 0) {
return LOGIN_ERROR_RLIMIT;
}
return 0;
}
static int set_prio (const char *value)
{
long prio;
if ( (getlong (value, &prio) == 0)
|| (prio != (int) prio)) {
return 0;
}
if (setpriority (PRIO_PROCESS, 0, (int) prio) != 0) {
return LOGIN_ERROR_RLIMIT;
}
return 0;
}
static int set_umask (const char *value)
{
unsigned long int mask;
if ( (getulong (value, &mask) == 0)
|| (mask != (mode_t) mask)) {
return 0;
}
(void) umask ((mode_t) mask);
return 0;
}
/* Counts the number of user logins and check against the limit */
static int check_logins (const char *name, const char *maxlogins)
{
#ifdef USE_UTMPX
struct utmpx *ut;
#else /* !USE_UTMPX */
struct utmp *ut;
#endif /* !USE_UTMPX */
unsigned long limit, count;
if (getulong (maxlogins, &limit) == 0) {
return 0;
}
if (0 == limit) { /* maximum 0 logins ? */
SYSLOG ((LOG_WARN, "No logins allowed for `%s'\n", name));
return LOGIN_ERROR_LOGIN;
}
count = 0;
#ifdef USE_UTMPX
setutxent ();
while ((ut = getutxent ()))
#else /* !USE_UTMPX */
setutent ();
while ((ut = getutent ()))
#endif /* !USE_UTMPX */
{
if (USER_PROCESS != ut->ut_type) {
continue;
}
if ('\0' == ut->ut_user[0]) {
continue;
}
if (strncmp (name, ut->ut_user, sizeof (ut->ut_user)) != 0) {
continue;
}
count++;
if (count > limit) {
break;
}
}
#ifdef USE_UTMPX
endutxent ();
#else /* !USE_UTMPX */
endutent ();
#endif /* !USE_UTMPX */
/*
* This is called after setutmp(), so the number of logins counted
* includes the user who is currently trying to log in.
*/
if (count > limit) {
SYSLOG ((LOG_WARN,
"Too many logins (max %lu) for %s\n",
limit, name));
return LOGIN_ERROR_LOGIN;
}
return 0;
}
/* Function setup_user_limits - checks/set limits for the current login
* Original idea from Joel Katz's lshell. Ported to shadow-login
* by Cristian Gafton - gafton@sorosis.ro
*
* We are passed a string of the form ('BASH' constants for ulimit)
* [Aa][Cc][Dd][Ff][Mm][Nn][Rr][Ss][Tt][Uu][Ll][Pp][Ii][Oo]
* (eg. 'C2F256D2048N5' or 'C2 F256 D2048 N5')
* where:
* [Aa]: a = RLIMIT_AS max address space (KB)
* [Cc]: c = RLIMIT_CORE max core file size (KB)
* [Dd]: d = RLIMIT_DATA max data size (KB)
* [Ff]: f = RLIMIT_FSIZE max file size (KB)
* [Ii]: i = RLIMIT_NICE max nice value (0..39 translates to 20..-19)
* [Kk]: k = file creation masK (umask)
* [Ll]: l = max number of logins for this user
* [Mm]: m = RLIMIT_MEMLOCK max locked-in-memory address space (KB)
* [Nn]: n = RLIMIT_NOFILE max number of open files
* [Oo]: o = RLIMIT_RTPRIO max real time priority (linux/sched.h 0..MAX_RT_PRIO)
* [Pp]: p = process priority -20..20 (negative = high, positive = low)
* [Rr]: r = RLIMIT_RSS max resident set size (KB)
* [Ss]: s = RLIMIT_STACK max stack size (KB)
* [Tt]: t = RLIMIT_CPU max CPU time (MIN)
* [Uu]: u = RLIMIT_NPROC max number of processes
*
* NOTE: Remember to extend the "no-limits" string below when adding a new
* limit...
*
* Return value:
* 0 = okay, of course
* LOGIN_ERROR_RLIMIT = error setting some RLIMIT
* LOGIN_ERROR_LOGIN = error - too many logins for this user
*
* buf - the limits string
* name - the username
*/
static int do_user_limits (const char *buf, const char *name)
{
const char *pp;
int retval = 0;
bool reported = false;
pp = buf;
/* Skip leading whitespace. */
while ((' ' == *pp) || ('\t' == *pp)) {
pp++;
}
/* The special limit string "-" results in no limit for all known
* limits.
* We achieve that by parsing a full limit string, parts of it
* being ignored if a limit type is not known to the system.
* Though, there will be complaining for unknown limit types.
*/
if (strcmp (pp, "-") == 0) {
/* Remember to extend this, too, when adding new limits!
* Oh... but "unlimited" does not make sense for umask,
* or does it? (K-)
*/
pp = "A- C- D- F- I- L- M- N- O- P- R- S- T- U-";
}
while ('\0' != *pp) {
switch (*pp++) {
#ifdef RLIMIT_AS
case 'a':
case 'A':
/* RLIMIT_AS - max address space (KB) */
retval |= setrlimit_value (RLIMIT_AS, pp, 1024);
break;
#endif
#ifdef RLIMIT_CORE
case 'c':
case 'C':
/* RLIMIT_CORE - max core file size (KB) */
retval |= setrlimit_value (RLIMIT_CORE, pp, 1024);
break;
#endif
#ifdef RLIMIT_DATA
case 'd':
case 'D':
/* RLIMIT_DATA - max data size (KB) */
retval |= setrlimit_value (RLIMIT_DATA, pp, 1024);
break;
#endif
#ifdef RLIMIT_FSIZE
case 'f':
case 'F':
/* RLIMIT_FSIZE - Maximum filesize (KB) */
retval |= setrlimit_value (RLIMIT_FSIZE, pp, 1024);
break;
#endif
#ifdef RLIMIT_NICE
case 'i':
case 'I':
/* RLIMIT_NICE - max scheduling priority (0..39) */
retval |= setrlimit_value (RLIMIT_NICE, pp, 1);
break;
#endif
case 'k':
case 'K':
retval |= set_umask (pp);
break;
case 'l':
case 'L':
/* LIMIT the number of concurrent logins */
retval |= check_logins (name, pp);
break;
#ifdef RLIMIT_MEMLOCK
case 'm':
case 'M':
/* RLIMIT_MEMLOCK - max locked-in-memory address space (KB) */
retval |= setrlimit_value (RLIMIT_MEMLOCK, pp, 1024);
break;
#endif
#ifdef RLIMIT_NOFILE
case 'n':
case 'N':
/* RLIMIT_NOFILE - max number of open files */
retval |= setrlimit_value (RLIMIT_NOFILE, pp, 1);
break;
#endif
#ifdef RLIMIT_RTPRIO
case 'o':
case 'O':
/* RLIMIT_RTPRIO - max real time priority (0..MAX_RT_PRIO) */
retval |= setrlimit_value (RLIMIT_RTPRIO, pp, 1);
break;
#endif
case 'p':
case 'P':
retval |= set_prio (pp);
break;
#ifdef RLIMIT_RSS
case 'r':
case 'R':
/* RLIMIT_RSS - max resident set size (KB) */
retval |= setrlimit_value (RLIMIT_RSS, pp, 1024);
break;
#endif
#ifdef RLIMIT_STACK
case 's':
case 'S':
/* RLIMIT_STACK - max stack size (KB) */
retval |= setrlimit_value (RLIMIT_STACK, pp, 1024);
break;
#endif
#ifdef RLIMIT_CPU
case 't':
case 'T':
/* RLIMIT_CPU - max CPU time (MIN) */
retval |= setrlimit_value (RLIMIT_CPU, pp, 60);
break;
#endif
#ifdef RLIMIT_NPROC
case 'u':
case 'U':
/* RLIMIT_NPROC - max number of processes */
retval |= setrlimit_value (RLIMIT_NPROC, pp, 1);
break;
#endif
default:
/* Only report invalid strings once */
/* Note: A string can be invalid just because a
* specific (theoretically valid) setting is not
* supported by this build.
* It is just a warning in syslog anyway. The line
* is still processed
*/
if (!reported) {
SYSLOG ((LOG_WARN,
"Invalid limit string: '%s'",
pp-1));
reported = true;
retval |= LOGIN_ERROR_RLIMIT;
}
}
/* After parsing one limit setting (or just complaining
* about it), one still needs to skip its argument to
* prevent a bogus warning on trying to parse that as
* limit specification.
* So, let's skip all digits, "-" and our limited set of
* whitespace.
*/
while ( isdigit (*pp)
|| ('-' == *pp)
|| (' ' == *pp)
|| ('\t' ==*pp)) {
pp++;
}
}
return retval;
}
/* Check if user uname is in the group gname.
* Can I be sure that gr_mem contains no UID as string?
* Returns true when user is in the group, false when not.
* Any error is treated as false.
*/
static bool user_in_group (const char *uname, const char *gname)
{
struct group *groupdata;
if (uname == NULL || gname == NULL) {
return false;
}
/* We are not claiming to be re-entrant!
* In case of paranoia or a multithreaded login program,
* one needs to add some mess for getgrnam_r. */
groupdata = getgrnam (gname);
if (NULL == groupdata) {
SYSLOG ((LOG_WARN, "Nonexisting group `%s' in limits file.",
gname));
return false;
}
return is_on_list (groupdata->gr_mem, uname);
}
static int setup_user_limits (const char *uname)
{
FILE *fil;
char buf[1024];
char name[1024];
char limits[1024];
char deflimits[1024];
char tempbuf[1024];
/* init things */
memzero (buf, sizeof (buf));
memzero (name, sizeof (name));
memzero (limits, sizeof (limits));
memzero (deflimits, sizeof (deflimits));
memzero (tempbuf, sizeof (tempbuf));
/* start the checks */
fil = fopen (LIMITS_FILE, "r");
if (fil == NULL) {
return 0;
}
/* The limits file have the following format:
* - '#' (comment) chars only as first chars on a line;
* - username must start on first column (or *, or @group)
*
* FIXME: A better (smarter) checking should be done
*/
while (fgets (buf, 1024, fil) != NULL) {
if (('#' == buf[0]) || ('\n' == buf[0])) {
continue;
}
memzero (tempbuf, sizeof (tempbuf));
/* a valid line should have a username, then spaces,
* then limits
* we allow the format:
* username L2 D2048 R4096
* where spaces={' ',\t}. Also, we reject invalid limits.
* Imposing a limit should be done with care, so a wrong
* entry means no care anyway :-).
*
* A '-' as a limits strings means no limits
*
* The username can also be:
* '*': the default limits (only the last is taken into
* account)
* @group: the limit applies to the members of the group
*
* To clarify: The first entry with matching user name rules,
* everything after it is ignored. If there is no user entry,
* the last encountered entry for a matching group rules.
* If there is no matching group entry, the default limits rule.
*/
if (sscanf (buf, "%s%[ACDFIKLMNOPRSTUacdfiklmnoprstu0-9 \t-]",
name, tempbuf) == 2) {
if (strcmp (name, uname) == 0) {
strcpy (limits, tempbuf);
break;
} else if (strcmp (name, "*") == 0) {
strcpy (deflimits, tempbuf);
} else if (name[0] == '@') {
/* If the user is in the group, the group
* limits apply unless later a line for
* the specific user is found.
*/
if (user_in_group (uname, name+1)) {
strcpy (limits, tempbuf);
}
}
}
}
(void) fclose (fil);
if (limits[0] == '\0') {
/* no user specific limits */
if (deflimits[0] == '\0') { /* no default limits */
return 0;
}
strcpy (limits, deflimits); /* use the default limits */
}
return do_user_limits (limits, uname);
}
#endif /* LIMITS */
static void setup_usergroups (const struct passwd *info)
{
const struct group *grp;
/*
* if not root, and UID == GID, and username is the same as primary
* group name, set umask group bits to be the same as owner bits
* (examples: 022 -> 002, 077 -> 007).
*/
if ((0 != info->pw_uid) && (info->pw_uid == info->pw_gid)) {
/* local, no need for xgetgrgid */
grp = getgrgid (info->pw_gid);
if ( (NULL != grp)
&& (strcmp (info->pw_name, grp->gr_name) == 0)) {
mode_t tmpmask;
tmpmask = umask (0777);
tmpmask = (tmpmask & ~070) | ((tmpmask >> 3) & 070);
(void) umask (tmpmask);
}
}
}
/*
* set the process nice, ulimit, and umask from the password file entry
*/
void setup_limits (const struct passwd *info)
{
char *cp;
if (getdef_bool ("USERGROUPS_ENAB")) {
setup_usergroups (info);
}
/*
* See if the GECOS field contains values for NICE, UMASK or ULIMIT.
* If this feature is enabled in /etc/login.defs, we make those
* values the defaults for this login session.
*/
if (getdef_bool ("QUOTAS_ENAB")) {
#ifdef LIMITS
if (info->pw_uid != 0) {
if ((setup_user_limits (info->pw_name) & LOGIN_ERROR_LOGIN) != 0) {
(void) fputs (_("Too many logins.\n"), shadow_logfd);
(void) sleep (2); /* XXX: Should be FAIL_DELAY */
exit (EXIT_FAILURE);
}
}
#endif
for (cp = info->pw_gecos; cp != NULL; cp = strchr (cp, ',')) {
if (',' == *cp) {
cp++;
}
if (strncmp (cp, "pri=", 4) == 0) {
long int inc;
if ( (getlong (cp + 4, &inc) == 1)
&& (inc >= -20) && (inc <= 20)) {
errno = 0;
if ( (nice ((int) inc) != -1)
|| (0 != errno)) {
continue;
}
}
/* Failed to parse or failed to nice() */
SYSLOG ((LOG_WARN,
"Can't set the nice value for user %s",
info->pw_name));
continue;
}
if (strncmp (cp, "ulimit=", 7) == 0) {
long int blocks;
if ( (getlong (cp + 7, &blocks) == 0)
|| (blocks != (int) blocks)
|| (set_filesize_limit ((int) blocks) != 0)) {
SYSLOG ((LOG_WARN,
"Can't set the ulimit for user %s",
info->pw_name));
}
continue;
}
if (strncmp (cp, "umask=", 6) == 0) {
unsigned long int mask;
if ( (getulong (cp + 6, &mask) == 0)
|| (mask != (mode_t) mask)) {
SYSLOG ((LOG_WARN,
"Can't set umask value for user %s",
info->pw_name));
} else {
(void) umask ((mode_t) mask);
}
continue;
}
}
}
}
#else /* !USE_PAM */
extern int errno; /* warning: ANSI C forbids an empty source file */
#endif /* !USE_PAM */
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