OpenPAM/lib/openpam_dynamic.c

/*-
 * 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.
 *
 * $Id$
 */

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

#include <sys/types.h>
#include <sys/stat.h>

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

#include <security/pam_appl.h>

#include "openpam_impl.h"

#ifndef RTLD_NOW
#define RTLD_NOW RTLD_LAZY
#endif

/*
 * OpenPAM internal
 *
 * Verify that a file or directory is owned by either root or the
 * arbitrator and that it is not writable by group or other.
 */

static int
check_owner_perms(const char *path)
{
	struct stat sb;

	if (stat(path, &sb) != 0)
		return (-1);
	if ((sb.st_uid != 0 && sb.st_uid != geteuid()) ||
	    (sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) {
		openpam_log(PAM_LOG_ERROR,
		    "%s: insecure ownership or permissions", path);
		errno = EPERM;
		return (-1);
	}
	return (0);
}

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

static void *
try_dlopen(const char *modfn)
{
	char *moddn;
	int ok, serrno;

	/*
	 * BSD dirname(3) returns a pointer to a static buffer, while GNU
	 * dirname(3) modifies the input string.  Use a copy of the string
	 * so both cases work.
	 */
	if ((moddn = strdup(modfn)) == NULL)
		return (NULL);
	ok = (check_owner_perms(dirname(moddn)) == 0 &&
	    check_owner_perms(modfn) == 0);
	serrno = errno;
	FREE(moddn);
	errno = serrno;
	return (ok ? dlopen(modfn, RTLD_NOW) : NULL);
}
    
/*
 * OpenPAM internal
 *
 * Locate a dynamically linked module
 */

pam_module_t *
openpam_dynamic(const char *path)
{
	const pam_module_t *dlmodule;
	pam_module_t *module;
	const char *prefix;
	char *vpath;
	void *dlh;
	int i, serrno;

	dlh = NULL;

	/* Prepend the standard prefix if not an absolute pathname. */
	if (path[0] != '/')
		prefix = OPENPAM_MODULES_DIR;
	else
		prefix = "";

	/* try versioned module first, then unversioned module */
	if (asprintf(&vpath, "%s%s.%d", prefix, path, LIB_MAJ) < 0)
		goto err;
	if ((dlh = try_dlopen(vpath)) == NULL && errno == ENOENT) {
		*strrchr(vpath, '.') = '\0';
		dlh = try_dlopen(vpath);
	}
	serrno = errno;
	FREE(vpath);
	errno = serrno;
	if (dlh == NULL)
		goto err;
	if ((module = calloc(1, sizeof *module)) == NULL)
		goto buf_err;
	if ((module->path = strdup(path)) == NULL)
		goto buf_err;
	module->dlh = dlh;
	dlmodule = dlsym(dlh, "_pam_module");
	for (i = 0; i < PAM_NUM_PRIMITIVES; ++i) {
		module->func[i] = dlmodule ? dlmodule->func[i] :
		    (pam_func_t)dlsym(dlh, pam_sm_func_name[i]);
		if (module->func[i] == NULL)
			openpam_log(PAM_LOG_DEBUG, "%s: %s(): %s",
			    path, pam_sm_func_name[i], dlerror());
	}
	return (module);
buf_err:
	if (dlh != NULL)
		dlclose(dlh);
	FREE(module);
err:
	openpam_log(PAM_LOG_ERROR, "%m");
	return (NULL);
}

/*
 * NOPARSE
 */