tarsnap/libarchive/archive_read_disk_set_standard_lookup.c

/*-
 * Copyright (c) 2003-2007 Tim Kientzle
 * All rights reserved.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``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(S) 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.
 */

#include "archive_platform.h"
__FBSDID("$FreeBSD$");

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#ifdef HAVE_GRP_H
#include <grp.h>
#endif
#ifdef HAVE_PWD_H
#include <pwd.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif

#include "archive.h"

#if defined(_WIN32) && !defined(__CYGWIN__)
int
archive_read_disk_set_standard_lookup(struct archive *a)
{
	archive_set_error(a, -1, "Standard lookups not available on Windows");
	return (ARCHIVE_FATAL);
}
#else /* ! (_WIN32 && !__CYGWIN__) */
#define	name_cache_size 127

static const char * const NO_NAME = "(noname)";

struct name_cache {
	struct archive *archive;
	char   *buff;
	size_t  buff_size;
	int	probes;
	int	hits;
	size_t	size;
	struct {
		id_t id;
		const char *name;
	} cache[name_cache_size];
};

static const char *	lookup_gname(void *, gid_t);
static const char *	lookup_uname(void *, uid_t);
static void	cleanup(void *);
static const char *	lookup_gname_helper(struct name_cache *, id_t gid);
static const char *	lookup_uname_helper(struct name_cache *, id_t uid);

/*
 * Installs functions that use getpwuid()/getgrgid()---along with
 * a simple cache to accelerate such lookups---into the archive_read_disk
 * object.  This is in a separate file because getpwuid()/getgrgid()
 * can pull in a LOT of library code (including NIS/LDAP functions, which
 * pull in DNS resolvers, etc).  This can easily top 500kB, which makes
 * it inappropriate for some space-constrained applications.
 *
 * Applications that are size-sensitive may want to just use the
 * real default functions (defined in archive_read_disk.c) that just
 * use the uid/gid without the lookup.  Or define your own custom functions
 * if you prefer.
 */
int
archive_read_disk_set_standard_lookup(struct archive *a)
{
	struct name_cache *ucache = malloc(sizeof(struct name_cache));
	struct name_cache *gcache = malloc(sizeof(struct name_cache));

	if (ucache == NULL || gcache == NULL) {
		archive_set_error(a, ENOMEM,
		    "Can't allocate uname/gname lookup cache");
		free(ucache);
		free(gcache);
		return (ARCHIVE_FATAL);
	}

	memset(ucache, 0, sizeof(*ucache));
	ucache->archive = a;
	ucache->size = name_cache_size;
	memset(gcache, 0, sizeof(*gcache));
	gcache->archive = a;
	gcache->size = name_cache_size;

	archive_read_disk_set_gname_lookup(a, gcache, lookup_gname, cleanup);
	archive_read_disk_set_uname_lookup(a, ucache, lookup_uname, cleanup);

	return (ARCHIVE_OK);
}

static void
cleanup(void *data)
{
	struct name_cache *cache = (struct name_cache *)data;
	size_t i;

	if (cache != NULL) {
		for (i = 0; i < cache->size; i++) {
			if (cache->cache[i].name != NULL &&
			    cache->cache[i].name != NO_NAME)
				free((void *)(uintptr_t)cache->cache[i].name);
		}
		free(cache->buff);
		free(cache);
	}
}

/*
 * Lookup uid/gid from uname/gname, return NULL if no match.
 */
static const char *
lookup_name(struct name_cache *cache,
    const char * (*lookup_fn)(struct name_cache *, id_t), id_t id)
{
	const char *name;
	int slot;


	cache->probes++;

	slot = id % cache->size;
	if (cache->cache[slot].name != NULL) {
		if (cache->cache[slot].id == id) {
			cache->hits++;
			if (cache->cache[slot].name == NO_NAME)
				return (NULL);
			return (cache->cache[slot].name);
		}
		if (cache->cache[slot].name != NO_NAME)
			free((void *)(uintptr_t)cache->cache[slot].name);
		cache->cache[slot].name = NULL;
	}

	name = (lookup_fn)(cache, id);
	if (name == NULL) {
		/* Cache and return the negative response. */
		cache->cache[slot].name = NO_NAME;
		cache->cache[slot].id = id;
		return (NULL);
	}

	cache->cache[slot].name = name;
	cache->cache[slot].id = id;
	return (cache->cache[slot].name);
}

static const char *
lookup_uname(void *data, uid_t uid)
{
	struct name_cache *uname_cache = (struct name_cache *)data;
	return (lookup_name(uname_cache,
		    &lookup_uname_helper, (id_t)uid));
}

static const char *
lookup_uname_helper(struct name_cache *cache, id_t id)
{
	struct passwd	pwent, *result;
	char * nbuff;
	size_t nbuff_size;
	int r;

	if (cache->buff_size == 0) {
		cache->buff_size = 256;
		cache->buff = malloc(cache->buff_size);
	}
	if (cache->buff == NULL)
		return (NULL);
	for (;;) {
		r = getpwuid_r((uid_t)id, &pwent,
			       cache->buff, cache->buff_size, &result);
		if (r == 0)
			break;
		if (r != ERANGE)
			break;
		/* ERANGE means our buffer was too small, but POSIX
		 * doesn't tell us how big the buffer should be, so
		 * we just double it and try again.  Because the buffer
		 * is kept around in the cache object, we shouldn't
		 * have to do this very often. */
		nbuff_size = cache->buff_size * 2;
		nbuff = realloc(cache->buff, nbuff_size);
		if (nbuff == NULL)
			break;
		cache->buff = nbuff;
		cache->buff_size = nbuff_size;
	}
	if (r != 0) {
		archive_set_error(cache->archive, errno,
		    "Can't lookup user for id %d", (int)id);
		return (NULL);
	}
	if (result == NULL)
		return (NULL);

	return strdup(result->pw_name);
}

static const char *
lookup_gname(void *data, gid_t gid)
{
	struct name_cache *gname_cache = (struct name_cache *)data;
	return (lookup_name(gname_cache,
		    &lookup_gname_helper, (id_t)gid));
}

static const char *
lookup_gname_helper(struct name_cache *cache, id_t id)
{
	struct group	grent, *result;
	char * nbuff;
	size_t nbuff_size;
	int r;

	if (cache->buff_size == 0) {
		cache->buff_size = 256;
		cache->buff = malloc(cache->buff_size);
	}
	if (cache->buff == NULL)
		return (NULL);
	for (;;) {
		r = getgrgid_r((gid_t)id, &grent,
			       cache->buff, cache->buff_size, &result);
		if (r == 0)
			break;
		if (r != ERANGE)
			break;
		/* ERANGE means our buffer was too small, but POSIX
		 * doesn't tell us how big the buffer should be, so
		 * we just double it and try again. */
		nbuff_size = cache->buff_size * 2;
		nbuff = realloc(cache->buff, nbuff_size);
		if (nbuff == NULL)
			break;
		cache->buff = nbuff;
		cache->buff_size = nbuff_size;
	}
	if (r != 0) {
		archive_set_error(cache->archive, errno,
		    "Can't lookup group for id %d", (int)id);
		return (NULL);
	}
	if (result == NULL)
		return (NULL);

	return strdup(result->gr_name);
}
#endif /* ! (_WIN32 && !__CYGWIN__) */