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/* Copyright (c) 2012-2013, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/*
* \file replaycache.c
*
* \brief Self-scrubbing replay cache for rendservice.c
*/
#define REPLAYCACHE_PRIVATE
#include "or.h"
#include "replaycache.h"
/** Free the replaycache r and all of its entries.
*/
void
replaycache_free(replaycache_t *r)
{
if (!r) {
log_info(LD_BUG, "replaycache_free() called on NULL");
return;
}
if (r->digests_seen) digestmap_free(r->digests_seen, tor_free_);
tor_free(r);
}
/** Allocate a new, empty replay detection cache, where horizon is the time
* for entries to age out and interval is the time after which the cache
* should be scrubbed for old entries.
*/
replaycache_t *
replaycache_new(time_t horizon, time_t interval)
{
replaycache_t *r = NULL;
if (horizon < 0) {
log_info(LD_BUG, "replaycache_new() called with negative"
" horizon parameter");
goto err;
}
if (interval < 0) {
log_info(LD_BUG, "replaycache_new() called with negative interval"
" parameter");
interval = 0;
}
r = tor_malloc(sizeof(*r));
r->scrub_interval = interval;
r->scrubbed = 0;
r->horizon = horizon;
r->digests_seen = digestmap_new();
err:
return r;
}
/** See documentation for replaycache_add_and_test()
*/
STATIC int
replaycache_add_and_test_internal(
time_t present, replaycache_t *r, const void *data, size_t len,
time_t *elapsed)
{
int rv = 0;
char digest[DIGEST_LEN];
time_t *access_time;
/* sanity check */
if (present <= 0 || !r || !data || len == 0) {
log_info(LD_BUG, "replaycache_add_and_test_internal() called with stupid"
" parameters; please fix this.");
goto done;
}
/* compute digest */
crypto_digest(digest, (const char *)data, len);
/* check map */
access_time = digestmap_get(r->digests_seen, digest);
/* seen before? */
if (access_time != NULL) {
/*
* If it's far enough in the past, no hit. If the horizon is zero, we
* never expire.
*/
if (*access_time >= present - r->horizon || r->horizon == 0) {
/* replay cache hit, return 1 */
rv = 1;
/* If we want to output an elapsed time, do so */
if (elapsed) {
if (present >= *access_time) {
*elapsed = present - *access_time;
} else {
/* We shouldn't really be seeing hits from the future, but... */
*elapsed = 0;
}
}
}
/*
* If it's ahead of the cached time, update
*/
if (*access_time < present) {
*access_time = present;
}
} else {
/* No, so no hit and update the digest map with the current time */
access_time = tor_malloc(sizeof(*access_time));
*access_time = present;
digestmap_set(r->digests_seen, digest, access_time);
}
/* now scrub the cache if it's time */
replaycache_scrub_if_needed_internal(present, r);
done:
return rv;
}
/** See documentation for replaycache_scrub_if_needed()
*/
STATIC void
replaycache_scrub_if_needed_internal(time_t present, replaycache_t *r)
{
digestmap_iter_t *itr = NULL;
const char *digest;
void *valp;
time_t *access_time;
/* sanity check */
if (!r || !(r->digests_seen)) {
log_info(LD_BUG, "replaycache_scrub_if_needed_internal() called with"
" stupid parameters; please fix this.");
return;
}
/* scrub time yet? (scrubbed == 0 indicates never scrubbed before) */
if (present - r->scrubbed < r->scrub_interval && r->scrubbed > 0) return;
/* if we're never expiring, don't bother scrubbing */
if (r->horizon == 0) return;
/* okay, scrub time */
itr = digestmap_iter_init(r->digests_seen);
while (!digestmap_iter_done(itr)) {
digestmap_iter_get(itr, &digest, &valp);
access_time = (time_t *)valp;
/* aged out yet? */
if (*access_time < present - r->horizon) {
/* Advance the iterator and remove this one */
itr = digestmap_iter_next_rmv(r->digests_seen, itr);
/* Free the value removed */
tor_free(access_time);
} else {
/* Just advance the iterator */
itr = digestmap_iter_next(r->digests_seen, itr);
}
}
/* update scrubbed timestamp */
if (present > r->scrubbed) r->scrubbed = present;
}
/** Test the buffer of length len point to by data against the replay cache r;
* the digest of the buffer will be added to the cache at the current time,
* and the function will return 1 if it was already seen within the cache's
* horizon, or 0 otherwise.
*/
int
replaycache_add_and_test(replaycache_t *r, const void *data, size_t len)
{
return replaycache_add_and_test_internal(time(NULL), r, data, len, NULL);
}
/** Like replaycache_add_and_test(), but if it's a hit also return the time
* elapsed since this digest was last seen.
*/
int
replaycache_add_test_and_elapsed(
replaycache_t *r, const void *data, size_t len, time_t *elapsed)
{
return replaycache_add_and_test_internal(time(NULL), r, data, len, elapsed);
}
/** Scrub aged entries out of r if sufficiently long has elapsed since r was
* last scrubbed.
*/
void
replaycache_scrub_if_needed(replaycache_t *r)
{
replaycache_scrub_if_needed_internal(time(NULL), r);
}
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