unixd.c   [plain text]

/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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;
    }

    if (NULL != unixd_config.chroot_dir) {
        if (geteuid()) {
            ap_log_error(APLOG_MARK, APLOG_ALERT, errno, NULL,
                         "Cannot chroot when not started as root");
            return -1;
        }
        if (chdir(unixd_config.chroot_dir) != 0) {
            ap_log_error(APLOG_MARK, APLOG_ALERT, errno, NULL,
                         "Can't chdir to %s", unixd_config.chroot_dir);
            return -1;
        }
        if (chroot(unixd_config.chroot_dir) != 0) {
            ap_log_error(APLOG_MARK, APLOG_ALERT, errno, NULL,
                         "Can't chroot to %s", unixd_config.chroot_dir);
            return -1;
        }
        if (chdir("/") != 0) {
            ap_log_error(APLOG_MARK, APLOG_ALERT, errno, NULL,
                         "Can't chdir to new root");
            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(const char *) unixd_set_chroot_dir(cmd_parms *cmd, void *dummy,
                                              const char *arg)
{
    const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
    if (err != NULL) {
        return err;
    }
    if (!ap_is_directory(cmd->pool, arg)) {
        return "ChrootDir must be a valid directory";
    }

    unixd_config.chroot_dir = arg;
    return NULL;
}

AP_DECLARE(const char *) unixd_set_suexec(cmd_parms *cmd, void *dummy,
                                          int arg)
{
    const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
    if (err != NULL) {
        return err;
    }

    if (!unixd_config.suexec_enabled && arg) {
        return "suEXEC isn't supported; check existence, owner, and "
               "file mode of " SUEXEC_BIN;
    }

    unixd_config.suexec_enabled = 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);
    
    unixd_config.chroot_dir = NULL; /* none */

    /* Check for suexec */
    unixd_config.suexec_enabled = 0;
    if ((apr_stat(&wrapper, SUEXEC_BIN,
                  APR_FINFO_NORM, ptemp)) != APR_SUCCESS) {
        return;
    }

    if ((wrapper.protection & APR_USETID) && 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;
#ifdef _OSD_POSIX
    int sockdes;
#endif

    *accepted = NULL;
    status = apr_socket_accept(&csd, lr->sd, ptrans);
    if (status == APR_SUCCESS) {
        *accepted = csd;
#ifdef _OSD_POSIX
        apr_os_sock_get(&sockdes, csd);
        if (sockdes >= FD_SETSIZE) {
            ap_log_error(APLOG_MARK, APLOG_WARNING, 0, NULL,
                         "new file descriptor %d is too large; you probably need "
                         "to rebuild Apache with a larger FD_SETSIZE "
                         "(currently %d)",
                         sockdes, FD_SETSIZE);
            apr_socket_close(csd);
            return APR_EINTR;
        }
#endif
        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;
}


#ifdef _OSD_POSIX

#include "apr_lib.h"

#define USER_LEN 8

typedef enum
{
    bs2_unknown,     /* not initialized yet. */
    bs2_noFORK,      /* no fork() because -X flag was specified */
    bs2_FORK,        /* only fork() because uid != 0 */
    bs2_UFORK        /* Normally, ufork() is used to switch identities. */
} bs2_ForkType;

static bs2_ForkType forktype = bs2_unknown;


static void ap_str_toupper(char *str)
{
    while (*str) {
        *str = apr_toupper(*str);
        ++str;
    }
}

/* Determine the method for forking off a child in such a way as to
 * set both the POSIX and BS2000 user id's to the unprivileged user.
 */
static bs2_ForkType os_forktype(int one_process)
{
    /* have we checked the OS version before? If yes return the previous
     * result - the OS release isn't going to change suddenly!
     */
    if (forktype == bs2_unknown) {
        /* not initialized yet */

        /* No fork if the one_process option was set */
        if (one_process) {
            forktype = bs2_noFORK;
        }
        /* If the user is unprivileged, use the normal fork() only. */
        else if (getuid() != 0) {
            forktype = bs2_FORK;
        }
        else
            forktype = bs2_UFORK;
    }
    return forktype;
}



/* This routine complements the setuid() call: it causes the BS2000 job
 * environment to be switched to the target user's user id.
 * That is important if CGI scripts try to execute native BS2000 commands.
 */
int os_init_job_environment(server_rec *server, const char *user_name, int one_process)
{
    bs2_ForkType            type = os_forktype(one_process);

    /* We can be sure that no change to uid==0 is possible because of
     * the checks in http_core.c:set_user()
     */

    if (one_process) {

        type = forktype = bs2_noFORK;

        ap_log_error(APLOG_MARK, APLOG_ERR, 0, server,
                     "The debug mode of Apache should only "
                     "be started by an unprivileged user!");
        return 0;
    }

    return 0;
}

/* BS2000 requires a "special" version of fork() before a setuid() call */
pid_t os_fork(const char *user)
{
    pid_t pid;
    char  username[USER_LEN+1];

    switch (os_forktype(0)) {

      case bs2_FORK:
        pid = fork();
        break;

      case bs2_UFORK:
        apr_cpystrn(username, user, sizeof username);

        /* Make user name all upper case - for some versions of ufork() */
        ap_str_toupper(username);

        pid = ufork(username);
        if (pid == -1 && errno == EPERM) {
            ap_log_error(APLOG_MARK, APLOG_EMERG, errno,
                         NULL, "ufork: Possible mis-configuration "
                         "for user %s - Aborting.", user);
            exit(1);
        }
        break;

      default:
        pid = 0;
        break;
    }

    return pid;
}

#endif /* _OSD_POSIX */