www/apache
www/apache
1
0
Fork 0
mirror of https://github.com/apache/httpd.git synced 2025-06-04 21:42:15 +03:00
Code
apache/os/unix/unixd.c
Jeff Trawick 4d8f4c26d6 *) SECURITY: CAN-2004-0174 (cve.mitre.org) 
Fix starvation issue on listening sockets where a short-lived
     connection on a rarely-accessed listening socket will cause a
     child to hold the accept mutex and block out new connections until
     another connection arrives on that rarely-accessed listening socket.
     With Apache 2.x there is no performance concern about enabling the
     logic for platforms which don't need it, so it is enabled everywhere
     except for Win32.  [Jeff Trawick]

(already in 2.0.49, propagating to mirrors now)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@103029 13f79535-47bb-0310-9956-ffa450edef68
2004-03-19 11:16:03 +00:00

589 lines
17 KiB
C
Raw Blame History

/* Copyright 1999-2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "ap_config.h"
#define CORE_PRIVATE
#include "httpd.h"
#include "http_config.h"
#include "http_main.h"
#include "http_log.h"
#include "unixd.h"
#include "mpm_common.h"
#include "os.h"
#include "ap_mpm.h"
#include "apr_thread_proc.h"
#include "apr_strings.h"
#include "apr_portable.h"
#ifdef HAVE_PWD_H
#include <pwd.h>
#endif
#ifdef HAVE_SYS_RESOURCE_H
#include <sys/resource.h>
#endif
/* XXX */
#include <sys/stat.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_GRP_H
#include <grp.h>
#endif
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#ifdef HAVE_SYS_SEM_H
#include <sys/sem.h>
#endif
#ifdef HAVE_SYS_PRCTL_H
#include <sys/prctl.h>
#endif
unixd_config_rec unixd_config;
/* Set group privileges.
*
* Note that we use the username as set in the config files, rather than
* the lookup of to uid --- the same uid may have multiple passwd entries,
* with different sets of groups for each.
*/
static int set_group_privs(void)
{
if (!geteuid()) {
const char *name;
/* Get username if passed as a uid */
if (unixd_config.user_name[0] == '#') {
struct passwd *ent;
uid_t uid = atoi(&unixd_config.user_name[1]);
if ((ent = getpwuid(uid)) == NULL) {
ap_log_error(APLOG_MARK, APLOG_ALERT, errno, NULL,
"getpwuid: couldn't determine user name from uid %u, "
"you probably need to modify the User directive",
(unsigned)uid);
return -1;
}
name = ent->pw_name;
}
else
name = unixd_config.user_name;
#if !defined(OS2) && !defined(TPF)
/* OS/2 and TPF don't support groups. */
/*
* Set the GID before initgroups(), since on some platforms
* setgid() is known to zap the group list.
*/
if (setgid(unixd_config.group_id) == -1) {
ap_log_error(APLOG_MARK, APLOG_ALERT, errno, NULL,
"setgid: unable to set group id to Group %u",
(unsigned)unixd_config.group_id);
return -1;
}
/* Reset `groups' attributes. */
if (initgroups(name, unixd_config.group_id) == -1) {
ap_log_error(APLOG_MARK, APLOG_ALERT, errno, NULL,
"initgroups: unable to set groups for User %s "
"and Group %u", name, (unsigned)unixd_config.group_id);
return -1;
}
#endif /* !defined(OS2) && !defined(TPF) */
}
return 0;
}
AP_DECLARE(int) unixd_setup_child(void)
{
if (set_group_privs()) {
return -1;
}
#ifdef MPE
/* Only try to switch if we're running as MANAGER.SYS */
if (geteuid() == 1 && unixd_config.user_id > 1) {
GETPRIVMODE();
if (setuid(unixd_config.user_id) == -1) {
GETUSERMODE();
ap_log_error(APLOG_MARK, APLOG_ALERT, errno, NULL,
"setuid: unable to change to uid: %ld",
(long) unixd_config.user_id);
exit(1);
}
GETUSERMODE();
}
#else
/* Only try to switch if we're running as root */
if (!geteuid() && (
#ifdef _OSD_POSIX
os_init_job_environment(NULL, unixd_config.user_name, ap_exists_config_define("DEBUG")) != 0 ||
#endif
setuid(unixd_config.user_id) == -1)) {
ap_log_error(APLOG_MARK, APLOG_ALERT, errno, NULL,
"setuid: unable to change to uid: %ld",
(long) unixd_config.user_id);
return -1;
}
#if defined(HAVE_PRCTL) && defined(PR_SET_DUMPABLE)
/* this applies to Linux 2.4+ */
#ifdef AP_MPM_WANT_SET_COREDUMPDIR
if (ap_coredumpdir_configured) {
if (prctl(PR_SET_DUMPABLE, 1)) {
ap_log_error(APLOG_MARK, APLOG_ALERT, errno, NULL,
"set dumpable failed - this child will not coredump"
" after software errors");
}
}
#endif
#endif
#endif
return 0;
}
AP_DECLARE(const char *) unixd_set_user(cmd_parms *cmd, void *dummy,
const char *arg)
{
const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
if (err != NULL) {
return err;
}
unixd_config.user_name = arg;
unixd_config.user_id = ap_uname2id(arg);
#if !defined (BIG_SECURITY_HOLE) && !defined (OS2)
if (unixd_config.user_id == 0) {
return "Error:\tApache has not been designed to serve pages while\n"
"\trunning as root. There are known race conditions that\n"
"\twill allow any local user to read any file on the system.\n"
"\tIf you still desire to serve pages as root then\n"
"\tadd -DBIG_SECURITY_HOLE to the CFLAGS env variable\n"
"\tand then rebuild the server.\n"
"\tIt is strongly suggested that you instead modify the User\n"
"\tdirective in your httpd.conf file to list a non-root\n"
"\tuser.\n";
}
#endif
return NULL;
}
AP_DECLARE(const char *) unixd_set_group(cmd_parms *cmd, void *dummy,
const char *arg)
{
const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
if (err != NULL) {
return err;
}
unixd_config.group_id = ap_gname2id(arg);
return NULL;
}
AP_DECLARE(void) unixd_pre_config(apr_pool_t *ptemp)
{
apr_finfo_t wrapper;
unixd_config.user_name = DEFAULT_USER;
unixd_config.user_id = ap_uname2id(DEFAULT_USER);
unixd_config.group_id = ap_gname2id(DEFAULT_GROUP);
/* Check for suexec */
unixd_config.suexec_enabled = 0;
if ((apr_stat(&wrapper, SUEXEC_BIN,
APR_FINFO_NORM, ptemp)) != APR_SUCCESS) {
return;
}
/* XXX - apr_stat is incapable of checking suid bits (grumble) */
/* if ((wrapper.filetype & S_ISUID) && wrapper.user == 0) { */
unixd_config.suexec_enabled = 1;
/* } */
}
AP_DECLARE(void) unixd_set_rlimit(cmd_parms *cmd, struct rlimit **plimit,
const char *arg, const char * arg2, int type)
{
#if (defined(RLIMIT_CPU) || defined(RLIMIT_DATA) || defined(RLIMIT_VMEM) || defined(RLIMIT_NPROC) || defined(RLIMIT_AS)) && APR_HAVE_STRUCT_RLIMIT && APR_HAVE_GETRLIMIT
char *str;
struct rlimit *limit;
/* If your platform doesn't define rlim_t then typedef it in ap_config.h */
rlim_t cur = 0;
rlim_t max = 0;
*plimit = (struct rlimit *)apr_pcalloc(cmd->pool, sizeof(**plimit));
limit = *plimit;
if ((getrlimit(type, limit)) != 0) {
*plimit = NULL;
ap_log_error(APLOG_MARK, APLOG_ERR, errno, cmd->server,
"%s: getrlimit failed", cmd->cmd->name);
return;
}
if ((str = ap_getword_conf(cmd->pool, &arg))) {
if (!strcasecmp(str, "max")) {
cur = limit->rlim_max;
}
else {
cur = atol(str);
}
}
else {
ap_log_error(APLOG_MARK, APLOG_ERR, 0, cmd->server,
"Invalid parameters for %s", cmd->cmd->name);
return;
}
if (arg2 && (str = ap_getword_conf(cmd->pool, &arg2))) {
max = atol(str);
}
/* if we aren't running as root, cannot increase max */
if (geteuid()) {
limit->rlim_cur = cur;
if (max) {
ap_log_error(APLOG_MARK, APLOG_ERR, 0, cmd->server,
"Must be uid 0 to raise maximum %s", cmd->cmd->name);
}
}
else {
if (cur) {
limit->rlim_cur = cur;
}
if (max) {
limit->rlim_max = max;
}
}
#else
ap_log_error(APLOG_MARK, APLOG_ERR, 0, cmd->server,
"Platform does not support rlimit for %s", cmd->cmd->name);
#endif
}
APR_HOOK_STRUCT(
APR_HOOK_LINK(get_suexec_identity)
)
AP_IMPLEMENT_HOOK_RUN_FIRST(ap_unix_identity_t *, get_suexec_identity,
(const request_rec *r), (r), NULL)
static apr_status_t ap_unix_create_privileged_process(
apr_proc_t *newproc, const char *progname,
const char * const *args,
const char * const *env,
apr_procattr_t *attr, ap_unix_identity_t *ugid,
apr_pool_t *p)
{
int i = 0;
const char **newargs;
char *newprogname;
char *execuser, *execgroup;
const char *argv0;
if (!unixd_config.suexec_enabled) {
return apr_proc_create(newproc, progname, args, env, attr, p);
}
argv0 = ap_strrchr_c(progname, '/');
/* Allow suexec's "/" check to succeed */
if (argv0 != NULL) {
argv0++;
}
else {
argv0 = progname;
}
if (ugid->userdir) {
execuser = apr_psprintf(p, "~%ld", (long) ugid->uid);
}
else {
execuser = apr_psprintf(p, "%ld", (long) ugid->uid);
}
execgroup = apr_psprintf(p, "%ld", (long) ugid->gid);
if (!execuser || !execgroup) {
return APR_ENOMEM;
}
i = 0;
if (args) {
while (args[i]) {
i++;
}
}
/* allocate space for 4 new args, the input args, and a null terminator */
newargs = apr_palloc(p, sizeof(char *) * (i + 4));
newprogname = SUEXEC_BIN;
newargs[0] = SUEXEC_BIN;
newargs[1] = execuser;
newargs[2] = execgroup;
newargs[3] = apr_pstrdup(p, argv0);
/*
** using a shell to execute suexec makes no sense thus
** we force everything to be APR_PROGRAM, and never
** APR_SHELLCMD
*/
if(apr_procattr_cmdtype_set(attr, APR_PROGRAM) != APR_SUCCESS) {
return APR_EGENERAL;
}
i = 1;
do {
newargs[i + 3] = args[i];
} while (args[i++]);
return apr_proc_create(newproc, newprogname, newargs, env, attr, p);
}
AP_DECLARE(apr_status_t) ap_os_create_privileged_process(
const request_rec *r,
apr_proc_t *newproc, const char *progname,
const char * const *args,
const char * const *env,
apr_procattr_t *attr, apr_pool_t *p)
{
ap_unix_identity_t *ugid = ap_run_get_suexec_identity(r);
if (ugid == NULL) {
return apr_proc_create(newproc, progname, args, env, attr, p);
}
return ap_unix_create_privileged_process(newproc, progname, args, env,
attr, ugid, p);
}
/* XXX move to APR and externalize (but implement differently :) ) */
static apr_lockmech_e proc_mutex_mech(apr_proc_mutex_t *pmutex)
{
const char *mechname = apr_proc_mutex_name(pmutex);
if (!strcmp(mechname, "sysvsem")) {
return APR_LOCK_SYSVSEM;
}
else if (!strcmp(mechname, "flock")) {
return APR_LOCK_FLOCK;
}
return APR_LOCK_DEFAULT;
}
AP_DECLARE(apr_status_t) unixd_set_proc_mutex_perms(apr_proc_mutex_t *pmutex)
{
if (!geteuid()) {
apr_lockmech_e mech = proc_mutex_mech(pmutex);
switch(mech) {
#if APR_HAS_SYSVSEM_SERIALIZE
case APR_LOCK_SYSVSEM:
{
apr_os_proc_mutex_t ospmutex;
#if !APR_HAVE_UNION_SEMUN
union semun {
long val;
struct semid_ds *buf;
unsigned short *array;
};
#endif
union semun ick;
struct semid_ds buf;
apr_os_proc_mutex_get(&ospmutex, pmutex);
buf.sem_perm.uid = unixd_config.user_id;
buf.sem_perm.gid = unixd_config.group_id;
buf.sem_perm.mode = 0600;
ick.buf = &buf;
if (semctl(ospmutex.crossproc, 0, IPC_SET, ick) < 0) {
return errno;
}
}
break;
#endif
#if APR_HAS_FLOCK_SERIALIZE
case APR_LOCK_FLOCK:
{
const char *lockfile = apr_proc_mutex_lockfile(pmutex);
if (lockfile) {
if (chown(lockfile, unixd_config.user_id,
-1 /* no gid change */) < 0) {
return errno;
}
}
}
break;
#endif
default:
/* do nothing */
break;
}
}
return APR_SUCCESS;
}
AP_DECLARE(apr_status_t) unixd_set_global_mutex_perms(apr_global_mutex_t *gmutex)
{
#if !APR_PROC_MUTEX_IS_GLOBAL
apr_os_global_mutex_t osgmutex;
apr_os_global_mutex_get(&osgmutex, gmutex);
return unixd_set_proc_mutex_perms(osgmutex.proc_mutex);
#else /* APR_PROC_MUTEX_IS_GLOBAL */
/* In this case, apr_proc_mutex_t and apr_global_mutex_t are the same. */
return unixd_set_proc_mutex_perms(gmutex);
#endif /* APR_PROC_MUTEX_IS_GLOBAL */
}
AP_DECLARE(apr_status_t) unixd_accept(void **accepted, ap_listen_rec *lr,
apr_pool_t *ptrans)
{
apr_socket_t *csd;
apr_status_t status;
*accepted = NULL;
status = apr_socket_accept(&csd, lr->sd, ptrans);
if (status == APR_SUCCESS) {
*accepted = csd;
return APR_SUCCESS;
}
if (APR_STATUS_IS_EINTR(status)) {
return status;
}
/* Our old behaviour here was to continue after accept()
* errors. But this leads us into lots of troubles
* because most of the errors are quite fatal. For
* example, EMFILE can be caused by slow descriptor
* leaks (say in a 3rd party module, or libc). It's
* foolish for us to continue after an EMFILE. We also
* seem to tickle kernel bugs on some platforms which
* lead to never-ending loops here. So it seems best
* to just exit in most cases.
*/
switch (status) {
#if defined(HPUX11) && defined(ENOBUFS)
/* On HPUX 11.x, the 'ENOBUFS, No buffer space available'
* error occurs because the accept() cannot complete.
* You will not see ENOBUFS with 10.20 because the kernel
* hides any occurrence from being returned to user space.
* ENOBUFS with 11.x's TCP/IP stack is possible, and could
* occur intermittently. As a work-around, we are going to
* ignore ENOBUFS.
*/
case ENOBUFS:
#endif
#ifdef EPROTO
/* EPROTO on certain older kernels really means
* ECONNABORTED, so we need to ignore it for them.
* See discussion in new-httpd archives nh.9701
* search for EPROTO.
*
* Also see nh.9603, search for EPROTO:
* There is potentially a bug in Solaris 2.x x<6,
* and other boxes that implement tcp sockets in
* userland (i.e. on top of STREAMS). On these
* systems, EPROTO can actually result in a fatal
* loop. See PR#981 for example. It's hard to
* handle both uses of EPROTO.
*/
case EPROTO:
#endif
#ifdef ECONNABORTED
case ECONNABORTED:
#endif
/* Linux generates the rest of these, other tcp
* stacks (i.e. bsd) tend to hide them behind
* getsockopt() interfaces. They occur when
* the net goes sour or the client disconnects
* after the three-way handshake has been done
* in the kernel but before userland has picked
* up the socket.
*/
#ifdef ECONNRESET
case ECONNRESET:
#endif
#ifdef ETIMEDOUT
case ETIMEDOUT:
#endif
#ifdef EHOSTUNREACH
case EHOSTUNREACH:
#endif
#ifdef ENETUNREACH
case ENETUNREACH:
#endif
/* EAGAIN/EWOULDBLOCK can be returned on BSD-derived
* TCP stacks when the connection is aborted before
* we call connect, but only because our listener
* sockets are non-blocking (AP_NONBLOCK_WHEN_MULTI_LISTEN)
*/
#ifdef EAGAIN
case EAGAIN:
#endif
#ifdef EWOULDBLOCK
#if !defined(EAGAIN) || EAGAIN != EWOULDBLOCK
case EWOULDBLOCK:
#endif
#endif
break;
#ifdef ENETDOWN
case ENETDOWN:
/*
* When the network layer has been shut down, there
* is not much use in simply exiting: the parent
* would simply re-create us (and we'd fail again).
* Use the CHILDFATAL code to tear the server down.
* @@@ Martin's idea for possible improvement:
* A different approach would be to define
* a new APEXIT_NETDOWN exit code, the reception
* of which would make the parent shutdown all
* children, then idle-loop until it detected that
* the network is up again, and restart the children.
* Ben Hyde noted that temporary ENETDOWN situations
* occur in mobile IP.
*/
ap_log_error(APLOG_MARK, APLOG_EMERG, status, ap_server_conf,
"apr_socket_accept: giving up.");
return APR_EGENERAL;
#endif /*ENETDOWN*/
#ifdef TPF
case EINACT:
ap_log_error(APLOG_MARK, APLOG_EMERG, status, ap_server_conf,
"offload device inactive");
return APR_EGENERAL;
break;
default:
ap_log_error(APLOG_MARK, APLOG_ERR, 0, ap_server_conf,
"select/accept error (%d)", status);
return APR_EGENERAL;
#else
default:
ap_log_error(APLOG_MARK, APLOG_ERR, status, ap_server_conf,
"apr_socket_accept: (client socket)");
return APR_EGENERAL;
#endif
}
return status;
}
View Git Blame Copy Permalink