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/* $OpenBSD: x509_issuer_cache.c,v 1.4 2022/12/26 07:18:53 jmc Exp $ */
/*
* Copyright (c) 2020 Bob Beck <beck@openbsd.org>
*
* 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.
*/
/* x509_issuer_cache */
/*
* The issuer cache is a cache of parent and child x509 certificate
* hashes with a signature validation result.
*
* Entries should only be added to the cache with a validation result
* from checking the public key math that "parent" signed "child".
*
* Finding an entry in the cache gets us the result of a previously
* performed validation of the signature of "parent" signing for the
* validity of "child". It allows us to skip doing the public key math
* when validating a certificate chain. It does not allow us to skip
* any other steps of validation (times, names, key usage, etc.)
*/
#include <pthread.h>
#include <string.h>
#include "x509_issuer_cache.h"
static int
x509_issuer_cmp(struct x509_issuer *x1, struct x509_issuer *x2)
{
int pcmp;
if ((pcmp = memcmp(x1->parent_md, x2->parent_md, EVP_MAX_MD_SIZE)) != 0)
return pcmp;
return memcmp(x1->child_md, x2->child_md, EVP_MAX_MD_SIZE);
}
static size_t x509_issuer_cache_count;
static size_t x509_issuer_cache_max = X509_ISSUER_CACHE_MAX;
static RB_HEAD(x509_issuer_tree, x509_issuer) x509_issuer_cache =
RB_INITIALIZER(&x509_issuer_cache);
static TAILQ_HEAD(lruqueue, x509_issuer) x509_issuer_lru =
TAILQ_HEAD_INITIALIZER(x509_issuer_lru);
static pthread_mutex_t x509_issuer_tree_mutex = PTHREAD_MUTEX_INITIALIZER;
RB_PROTOTYPE(x509_issuer_tree, x509_issuer, entry, x509_issuer_cmp);
RB_GENERATE(x509_issuer_tree, x509_issuer, entry, x509_issuer_cmp);
/*
* Set the maximum number of cached entries. On additions to the cache
* the least recently used entries will be discarded so that the cache
* stays under the maximum number of entries. Setting a maximum of 0
* disables the cache.
*/
int
x509_issuer_cache_set_max(size_t max)
{
if (pthread_mutex_lock(&x509_issuer_tree_mutex) != 0)
return 0;
x509_issuer_cache_max = max;
(void) pthread_mutex_unlock(&x509_issuer_tree_mutex);
return 1;
}
/*
* Free the oldest entry in the issuer cache. Returns 1
* if an entry was successfully freed, 0 otherwise. Must
* be called with x509_issuer_tree_mutex held.
*/
void
x509_issuer_cache_free_oldest()
{
struct x509_issuer *old;
if (x509_issuer_cache_count == 0)
return;
old = TAILQ_LAST(&x509_issuer_lru, lruqueue);
TAILQ_REMOVE(&x509_issuer_lru, old, queue);
RB_REMOVE(x509_issuer_tree, &x509_issuer_cache, old);
free(old->parent_md);
free(old->child_md);
free(old);
x509_issuer_cache_count--;
}
/*
* Free the entire issuer cache, discarding all entries.
*/
void
x509_issuer_cache_free()
{
if (pthread_mutex_lock(&x509_issuer_tree_mutex) != 0)
return;
while (x509_issuer_cache_count > 0)
x509_issuer_cache_free_oldest();
(void) pthread_mutex_unlock(&x509_issuer_tree_mutex);
}
/*
* Find a previous result of checking if parent signed child
*
* Returns:
* -1 : No entry exists in the cache. signature must be checked.
* 0 : The signature of parent signing child is invalid.
* 1 : The signature of parent signing child is valid.
*/
int
x509_issuer_cache_find(unsigned char *parent_md, unsigned char *child_md)
{
struct x509_issuer candidate, *found;
int ret = -1;
memset(&candidate, 0, sizeof(candidate));
candidate.parent_md = parent_md;
candidate.child_md = child_md;
if (x509_issuer_cache_max == 0)
return -1;
if (pthread_mutex_lock(&x509_issuer_tree_mutex) != 0)
return -1;
if ((found = RB_FIND(x509_issuer_tree, &x509_issuer_cache,
&candidate)) != NULL) {
TAILQ_REMOVE(&x509_issuer_lru, found, queue);
TAILQ_INSERT_HEAD(&x509_issuer_lru, found, queue);
ret = found->valid;
}
(void) pthread_mutex_unlock(&x509_issuer_tree_mutex);
return ret;
}
/*
* Attempt to add a validation result to the cache.
*
* valid must be:
* 0: The signature of parent signing child is invalid.
* 1: The signature of parent signing child is valid.
*
* Previously added entries for the same parent and child are *not* replaced.
*/
void
x509_issuer_cache_add(unsigned char *parent_md, unsigned char *child_md,
int valid)
{
struct x509_issuer *new;
if (x509_issuer_cache_max == 0)
return;
if (valid != 0 && valid != 1)
return;
if ((new = calloc(1, sizeof(struct x509_issuer))) == NULL)
return;
if ((new->parent_md = calloc(1, EVP_MAX_MD_SIZE)) == NULL)
goto err;
memcpy(new->parent_md, parent_md, EVP_MAX_MD_SIZE);
if ((new->child_md = calloc(1, EVP_MAX_MD_SIZE)) == NULL)
goto err;
memcpy(new->child_md, child_md, EVP_MAX_MD_SIZE);
new->valid = valid;
if (pthread_mutex_lock(&x509_issuer_tree_mutex) != 0)
goto err;
while (x509_issuer_cache_count >= x509_issuer_cache_max)
x509_issuer_cache_free_oldest();
if (RB_INSERT(x509_issuer_tree, &x509_issuer_cache, new) == NULL) {
TAILQ_INSERT_HEAD(&x509_issuer_lru, new, queue);
x509_issuer_cache_count++;
new = NULL;
}
(void) pthread_mutex_unlock(&x509_issuer_tree_mutex);
err:
if (new != NULL) {
free(new->parent_md);
free(new->child_md);
}
free(new);
return;
}
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