source: openpam/trunk/lib/libpam/openpam_dynamic.c @ 674

/*-
 * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
 * Copyright (c) 2004-2011 Dag-Erling Smørgrav
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project by ThinkSec AS and
 * Network Associates Laboratories, the Security Research Division of
 * Network Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
 * ("CBOSS"), as part of the DARPA CHATS research program.
 *
 * 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 author may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 *
 * $Id: openpam_dynamic.c 674 2013-03-17 20:04:24Z des $
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <sys/param.h>

#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <security/pam_appl.h>

#include "openpam_impl.h"
#include "openpam_asprintf.h"
#include "openpam_ctype.h"
#include "openpam_dlfunc.h"

#ifndef RTLD_NOW
#define RTLD_NOW RTLD_LAZY
#endif

/*
 * OpenPAM internal
 *
 * Perform sanity checks and attempt to load a module
 */

#ifdef HAVE_FDLOPEN
static void *
try_dlopen(const char *modfn)
{
        void *dlh;
        int fd;

        openpam_log(PAM_LOG_LIBDEBUG, "dlopen(%s)", modfn);
        if ((fd = open(modfn, O_RDONLY)) < 0)
                return (NULL);
        if (OPENPAM_FEATURE(VERIFY_MODULE_FILE) &&
            openpam_check_desc_owner_perms(modfn, fd) != 0) {
                close(fd);
                return (NULL);
        }
        if ((dlh = fdlopen(fd, RTLD_NOW)) == NULL) {
                openpam_log(PAM_LOG_ERROR, "%s: %s", modfn, dlerror());
                close(fd);
                errno = 0;
                return (NULL);
        }
        close(fd);
        return (dlh);
}
#else
static void *
try_dlopen(const char *modfn)
{
        int check_module_file;
        void *dlh;

        openpam_log(PAM_LOG_LIBDEBUG, "dlopen(%s)", modfn);
        openpam_get_feature(OPENPAM_VERIFY_MODULE_FILE,
            &check_module_file);
        if (check_module_file &&
            openpam_check_path_owner_perms(modfn) != 0)
                return (NULL);
        if ((dlh = dlopen(modfn, RTLD_NOW)) == NULL) {
                openpam_log(PAM_LOG_ERROR, "%s: %s", modfn, dlerror());
                errno = 0;
                return (NULL);
        }
        return (dlh);
}
#endif

/*
 * Try to load a module from the suggested location.
 */
static pam_module_t *
try_module(const char *modpath)
{
        const pam_module_t *dlmodule;
        pam_module_t *module;
        int i, serrno;

        if ((module = calloc(1, sizeof *module)) == NULL ||
            (module->path = strdup(modpath)) == NULL ||
            (module->dlh = try_dlopen(modpath)) == NULL)
                goto err;
        dlmodule = dlsym(module->dlh, "_pam_module");
        for (i = 0; i < PAM_NUM_PRIMITIVES; ++i) {
                if (dlmodule) {
                        module->func[i] = dlmodule->func[i];
                } else {
                        module->func[i] = (pam_func_t)dlfunc(module->dlh,
                            pam_sm_func_name[i]);
                        /*
                         * This openpam_log() call is a major source of
                         * log spam, and the cases that matter are caught
                         * and logged in openpam_dispatch().  This would
                         * be less problematic if dlerror() returned an
                         * error code so we could log an error only when
                         * dlfunc() failed for a reason other than "no
                         * such symbol".
                         */
#if 0
                        if (module->func[i] == NULL)
                                openpam_log(PAM_LOG_LIBDEBUG, "%s: %s(): %s",
                                    modpath, pam_sm_func_name[i], dlerror());
#endif
                }
        }
        return (module);
err:
        serrno = errno;
        if (module != NULL) {
                if (module->dlh != NULL)
                        dlclose(module->dlh);
                if (module->path != NULL)
                        FREE(module->path);
                FREE(module);
        }
        errno = serrno;
        if (serrno != 0 && serrno != ENOENT)
                openpam_log(PAM_LOG_ERROR, "%s: %m", modpath);
        errno = serrno;
        return (NULL);
}

/*
 * OpenPAM internal
 *
 * Locate a dynamically linked module
 */

pam_module_t *
openpam_dynamic(const char *modname)
{
        pam_module_t *module;
        char modpath[PATH_MAX];
        const char **path, *p;
        int has_so, has_ver;
        int dot, len;

        /*
         * Simple case: module name contains path separator(s)
         */
        if (strchr(modname, '/') != NULL) {
                /*
                 * Absolute paths are not allowed if RESTRICT_MODULE_NAME
                 * is in effect (default off).  Relative paths are never
                 * allowed.
                 */
                if (OPENPAM_FEATURE(RESTRICT_MODULE_NAME) ||
                    modname[0] != '/') {
                        openpam_log(PAM_LOG_ERROR,
                            "invalid module name: %s", modname);
                        return (NULL);
                }
                return (try_module(modname));
        }

        /*
         * Check for .so and version sufixes
         */
        p = strchr(modname, '\0');
        has_ver = has_so = 1;
        while (is_digit(*p))
                --p;
        if (*p == '.' && *++p != '\0') {
                /* found a numeric suffix */
                has_ver = 1;
                /* assume that .so is either present or unneeded */
                has_so = 1;
        } else if (*p == '\0' && p >= modname + sizeof PAM_SOEXT &&
            strcmp(p - sizeof PAM_SOEXT + 1, PAM_SOEXT) == 0) {
                /* found .so suffix */
                has_so = 1;
        }

        /*
         * Complicated case: search for the module in the usual places.
         */
        for (path = openpam_module_path; *path != NULL; ++path) {
                /*
                 * Assemble the full path, including the version suffix.  Take
                 * note of where the suffix begins so we can cut it off later.
                 */
                if (has_ver)
                        len = snprintf(modpath, sizeof modpath, "%s/%s%n",
                            *path, modname, &dot);
                else if (has_so)
                        len = snprintf(modpath, sizeof modpath, "%s/%s%n.%d",
                            *path, modname, &dot, LIB_MAJ);
                else
                        len = snprintf(modpath, sizeof modpath, "%s/%s%s%n.%d",
                            *path, modname, PAM_SOEXT, &dot, LIB_MAJ);
                /* check for overflow */
                if (len < 0 || (unsigned int)len >= sizeof modpath) {
                        errno = ENOENT;
                        continue;
                }
                /* try the versioned path */
                if ((module = try_module(modpath)) != NULL)
                        return (module);
                if (errno == ENOENT && modpath[dot] != '\0') {
                        /* no luck, try the unversioned path */
                        modpath[dot] = '\0';
                        if ((module = try_module(modpath)) != NULL)
                                return (module);
                }
        }

        /* :( */
        return (NULL);
}

/*
 * NOPARSE
 */