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/*
* SPDX-License-Identifier: ISC
*
* Copyright (c) 2023 Todd C. Miller <Todd.Miller@sudo.ws>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This is an open source non-commercial project. Dear PVS-Studio, please check it.
* PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
*/
#include <config.h>
#include <sys/stat.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sudoers.h>
#include <redblack.h>
static struct rbtree *canon_cache;
/*
* A cache_item includes storage for both the original path and the
* resolved path. The resolved path is directly embedded into the
* struct so that we can find the start of the struct cache_item
* given the value of resolved. Storage for pathname is embedded
* at the end with resolved.
*/
struct cache_item {
unsigned int refcnt;
char *pathname;
char resolved[];
};
/*
* Compare function for canon_cache.
* v1 is the key to find or data to insert, v2 is in-tree data.
*/
static int
compare(const void *v1, const void *v2)
{
const struct cache_item *ci1 = (const struct cache_item *)v1;
const struct cache_item *ci2 = (const struct cache_item *)v2;
return strcmp(ci1->pathname, ci2->pathname);
}
/* Convert a pointer returned by canon_path() to a struct cache_item *. */
#define resolved_to_item(_r) ((struct cache_item *)((_r) - offsetof(struct cache_item, resolved)))
/*
* Delete a ref from item and free if the refcount reaches 0.
*/
static void
canon_path_free_item(void *v)
{
struct cache_item *item = v;
debug_decl(canon_path_free_item, SUDOERS_DEBUG_UTIL);
if (--item->refcnt == 0)
free(item);
debug_return;
}
/*
* Delete a ref from the item containing "resolved" and free if
* the refcount reaches 0.
*/
void
canon_path_free(char *resolved)
{
debug_decl(canon_path_free, SUDOERS_DEBUG_UTIL);
if (resolved != NULL)
canon_path_free_item(resolved_to_item(resolved));
debug_return;
}
/*
* Free canon_cache.
* This only removes the reference for that the cache owns.
* Other references remain valid until canon_path_free() is called.
*/
void
canon_path_free_cache(void)
{
debug_decl(canon_path_free_cache, SUDOERS_DEBUG_UTIL);
if (canon_cache != NULL) {
rbdestroy(canon_cache, canon_path_free_item);
canon_cache = NULL;
}
debug_return;
}
/*
* Like realpath(3) but caches the result. Returns an entry from the
* cache on success (with an added reference) or NULL on failure.
*/
char *
canon_path(const char *inpath)
{
size_t item_size, inlen, reslen = 0;
char *resolved, resbuf[PATH_MAX];
struct cache_item key, *item;
struct rbnode *node = NULL;
debug_decl(canon_path, SUDOERS_DEBUG_UTIL);
if (canon_cache == NULL) {
canon_cache = rbcreate(compare);
if (canon_cache == NULL) {
sudo_warnx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
debug_return_str(NULL);
}
} else {
/* Check cache. */
key.pathname = (char *)inpath;
if ((node = rbfind(canon_cache, &key)) != NULL) {
item = node->data;
goto done;
}
}
/*
* Not cached, call realpath(3).
* Older realpath() doesn't support passing a NULL buffer.
* We special-case the empty string to resolve to "/".
* XXX - warn on errors other than ENOENT?
*/
if (*inpath == '\0')
resolved = (char *)"/";
else
resolved = realpath(inpath, resbuf);
inlen = strlen(inpath);
/* one for NULL terminator of resolved, one for NULL terminator of pathname */
item_size = sizeof(*item) + inlen + 2;
if (resolved != NULL) {
reslen = strlen(resolved);
item_size += reslen;
}
item = malloc(item_size);
if (item == NULL) {
sudo_warnx(U_("%s: %s"), __func__, U_("unable to allocate memory"));
debug_return_str(NULL);
}
if (resolved != NULL)
memcpy(item->resolved, resolved, reslen);
item->resolved[reslen] = '\0';
item->pathname = item->resolved + reslen + 1;
memcpy(item->pathname, inpath, inlen);
item->pathname[inlen] = '\0';
item->refcnt = 1;
switch (rbinsert(canon_cache, item, NULL)) {
case 1:
/* should not happen */
sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
"path \"%s\" already exists in the cache", inpath);
item->refcnt = 0;
break;
case -1:
/* can't cache item, just return it */
sudo_debug_printf(SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO,
"can't cache path \"%s\"", inpath);
item->refcnt = 0;
break;
}
done:
if (item->refcnt != 0) {
sudo_debug_printf(SUDO_DEBUG_DEBUG,
"%s: path %s -> %s (%s)", __func__, inpath,
item->resolved[0] ? item->resolved : "NULL",
node ? "cache hit" : "cached");
}
if (item->resolved[0] == '\0') {
/* negative result, free item if not cached */
if (item->refcnt == 0)
free(item);
debug_return_str(NULL);
}
item->refcnt++;
debug_return_str(item->resolved);
}
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