crypto/property/property.c - third_party/openssl - Git at Google

 /*
  * Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
  * Copyright (c) 2019, Oracle and/or its affiliates.  All rights reserved.
  *
  * Licensed under the Apache License 2.0 (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
  * in the file LICENSE in the source distribution or at
  * https://www.openssl.org/source/license.html
  */

 #include <string.h>
 #include <stdio.h>
 #include <stdarg.h>
 #include <openssl/crypto.h>
 #include "internal/property.h"
 #include "internal/ctype.h"
 #include <openssl/lhash.h>
 #include <openssl/rand.h>
 #include "internal/thread_once.h"
 #include "internal/lhash.h"
 #include "internal/sparse_array.h"
 #include "property_lcl.h"

 /* The number of elements in the query cache before we initiate a flush */
 #define IMPL_CACHE_FLUSH_THRESHOLD  500

 typedef struct {
     OSSL_PROPERTY_LIST *properties;
     void *method;
     void (*method_destruct)(void *);
 } IMPLEMENTATION;

 DEFINE_STACK_OF(IMPLEMENTATION)

 typedef struct {
     const char *query;
     void *method;
     char body[1];
 } QUERY;

 DEFINE_LHASH_OF(QUERY);

 typedef struct {
     int nid;
     STACK_OF(IMPLEMENTATION) *impls;
     LHASH_OF(QUERY) *cache;
 } ALGORITHM;

 struct ossl_method_store_st {
     size_t nelem;
     SPARSE_ARRAY_OF(ALGORITHM) *algs;
     OSSL_PROPERTY_LIST *global_properties;
     int need_flush;
     unsigned int nbits;
     unsigned char rand_bits[(IMPL_CACHE_FLUSH_THRESHOLD + 7) / 8];
     CRYPTO_RWLOCK *lock;
 };

 typedef struct {
     OSSL_METHOD_STORE *store;
     LHASH_OF(QUERY) *cache;
     size_t nelem;
 } IMPL_CACHE_FLUSH;

 DEFINE_SPARSE_ARRAY_OF(ALGORITHM);

 static void ossl_method_cache_flush(OSSL_METHOD_STORE *store, int nid);
 static void ossl_method_cache_flush_all(OSSL_METHOD_STORE *c);

 int ossl_property_read_lock(OSSL_METHOD_STORE *p)
 {
     return p != NULL ? CRYPTO_THREAD_read_lock(p->lock) : 0;
 }

 int ossl_property_write_lock(OSSL_METHOD_STORE *p)
 {
     return p != NULL ? CRYPTO_THREAD_write_lock(p->lock) : 0;
 }

 int ossl_property_unlock(OSSL_METHOD_STORE *p)
 {
     return p != 0 ? CRYPTO_THREAD_unlock(p->lock) : 0;
 }

 int ossl_method_store_init(void)
 {
     if (ossl_property_string_init()
             && ossl_prop_defn_init()
             && ossl_property_parse_init())
         return 1;

     ossl_method_store_cleanup();
     return 0;
 }

 void ossl_method_store_cleanup(void)
 {
     ossl_property_string_cleanup();
     ossl_prop_defn_cleanup();
 }

 static CRYPTO_ONCE method_store_init_flag = CRYPTO_ONCE_STATIC_INIT;
 DEFINE_RUN_ONCE_STATIC(do_method_store_init)
 {
     return OPENSSL_init_crypto(0, NULL)
         && ossl_method_store_init()
         && OPENSSL_atexit(&ossl_method_store_cleanup);
 }

 static unsigned long query_hash(const QUERY *a)
 {
     return OPENSSL_LH_strhash(a->query);
 }

 static int query_cmp(const QUERY *a, const QUERY *b)
 {
     return strcmp(a->query, b->query);
 }

 static void impl_free(IMPLEMENTATION *impl)
 {
     if (impl != NULL) {
         if (impl->method_destruct)
             impl->method_destruct(impl->method);
         OPENSSL_free(impl);
     }
 }

 static void impl_cache_free(QUERY *elem)
 {
     OPENSSL_free(elem);
 }

 static void alg_cleanup(ossl_uintmax_t idx, ALGORITHM *a)
 {
     if (a != NULL) {
         sk_IMPLEMENTATION_pop_free(a->impls, &impl_free);
         lh_QUERY_doall(a->cache, &impl_cache_free);
         lh_QUERY_free(a->cache);
         OPENSSL_free(a);
     }
 }

 OSSL_METHOD_STORE *ossl_method_store_new(void)
 {
     OSSL_METHOD_STORE *res;

     if (!RUN_ONCE(&method_store_init_flag, do_method_store_init))
         return 0;

     res = OPENSSL_zalloc(sizeof(*res));
     if (res != NULL) {
         if ((res->algs = ossl_sa_ALGORITHM_new()) == NULL) {
             OPENSSL_free(res);
             return NULL;
         }
         if ((res->lock = CRYPTO_THREAD_lock_new()) == NULL) {
             OPENSSL_free(res->algs);
             OPENSSL_free(res);
             return NULL;
         }
     }
     return res;
 }

 void ossl_method_store_free(OSSL_METHOD_STORE *store)
 {
     if (store != NULL) {
         ossl_sa_ALGORITHM_doall(store->algs, &alg_cleanup);
         ossl_sa_ALGORITHM_free(store->algs);
         ossl_property_free(store->global_properties);
         CRYPTO_THREAD_lock_free(store->lock);
         OPENSSL_free(store);
     }
 }

 static ALGORITHM *ossl_method_store_retrieve(OSSL_METHOD_STORE *store, int nid)
 {
     return ossl_sa_ALGORITHM_get(store->algs, nid);
 }

 static int ossl_method_store_insert(OSSL_METHOD_STORE *store, ALGORITHM *alg)
 {
         return ossl_sa_ALGORITHM_set(store->algs, alg->nid, alg);
 }

 int ossl_method_store_add(OSSL_METHOD_STORE *store,
                           int nid, const char *properties,
                           void *method, void (*method_destruct)(void *))
 {
     ALGORITHM *alg = NULL;
     IMPLEMENTATION *impl;
     int ret = 0;

     if (nid <= 0 || method == NULL || store == NULL)
         return 0;
     if (properties == NULL)
         properties = "";

     /* Create new entry */
     impl = OPENSSL_malloc(sizeof(*impl));
     if (impl == NULL)
         return 0;
     impl->method = method;
     impl->method_destruct = method_destruct;

     /*
      * Insert into the hash table if required.
      *
      * A write lock is used unconditionally because we wend our way down to the
      * property string code which isn't locking friendly.
      */
     ossl_property_write_lock(store);
     ossl_method_cache_flush(store, nid);
     if ((impl->properties = ossl_prop_defn_get(properties)) == NULL) {
         if ((impl->properties = ossl_parse_property(properties)) == NULL)
             goto err;
         ossl_prop_defn_set(properties, impl->properties);
     }

     alg = ossl_method_store_retrieve(store, nid);
     if (alg == NULL) {
         if ((alg = OPENSSL_zalloc(sizeof(*alg))) == NULL
                 || (alg->impls = sk_IMPLEMENTATION_new_null()) == NULL
                 || (alg->cache = lh_QUERY_new(&query_hash, &query_cmp)) == NULL)
             goto err;
         alg->nid = nid;
         if (!ossl_method_store_insert(store, alg))
             goto err;
     }

     /* Push onto stack */
     if (sk_IMPLEMENTATION_push(alg->impls, impl))
         ret = 1;
     ossl_property_unlock(store);
     if (ret == 0)
         impl_free(impl);
     return ret;

 err:
     ossl_property_unlock(store);
     alg_cleanup(0, alg);
     impl_free(impl);
     return 0;
 }

 int ossl_method_store_remove(OSSL_METHOD_STORE *store, int nid,
                              const void *method)
 {
     ALGORITHM *alg = NULL;
     int i;

     if (nid <= 0 || method == NULL || store == NULL)
         return 0;

     ossl_property_write_lock(store);
     ossl_method_cache_flush(store, nid);
     alg = ossl_method_store_retrieve(store, nid);
     if (alg == NULL) {
         ossl_property_unlock(store);
         return 0;
     }

     /*
      * A sorting find then a delete could be faster but these stacks should be
      * relatively small, so we avoid the overhead.  Sorting could also surprise
      * users when result orderings change (even though they are not guaranteed).
      */
     for (i = 0; i < sk_IMPLEMENTATION_num(alg->impls); i++) {
         IMPLEMENTATION *impl = sk_IMPLEMENTATION_value(alg->impls, i);

         if (impl->method == method) {
             sk_IMPLEMENTATION_delete(alg->impls, i);
             ossl_property_unlock(store);
             impl_free(impl);
             return 1;
         }
     }
     ossl_property_unlock(store);
     return 0;
 }

 int ossl_method_store_fetch(OSSL_METHOD_STORE *store, int nid,
                             const char *prop_query, void **method)
 {
     ALGORITHM *alg;
     IMPLEMENTATION *impl;
     OSSL_PROPERTY_LIST *pq = NULL, *p2;
     int ret = 0;
     int j;

     if (nid <= 0 || method == NULL || store == NULL)
         return 0;

     /*
      * This only needs to be a read lock, because queries never create property
      * names or value and thus don't modify any of the property string layer.
      */
     ossl_property_read_lock(store);
     alg = ossl_method_store_retrieve(store, nid);
     if (alg == NULL) {
         ossl_property_unlock(store);
         return 0;
     }

     if (prop_query == NULL) {
         if ((impl = sk_IMPLEMENTATION_value(alg->impls, 0)) != NULL) {
             *method = impl->method;
             ret = 1;
         }
         goto fin;
     }
     pq = ossl_parse_query(prop_query);
     if (pq == NULL)
         goto fin;
     if (store->global_properties != NULL) {
         p2 = ossl_property_merge(pq, store->global_properties);
         if (p2 == NULL)
             goto fin;
         ossl_property_free(pq);
         pq = p2;
     }
     for (j = 0; j < sk_IMPLEMENTATION_num(alg->impls); j++) {
         impl = sk_IMPLEMENTATION_value(alg->impls, j);

         if (ossl_property_match(pq, impl->properties)) {
             *method = impl->method;
             ret = 1;
             goto fin;
         }
     }
 fin:
     ossl_property_unlock(store);
     ossl_property_free(pq);
     return ret;
 }

 int ossl_method_store_set_global_properties(OSSL_METHOD_STORE *store,
                                             const char *prop_query) {
     int ret = 0;

     if (store == NULL)
         return 1;

     ossl_property_write_lock(store);
     ossl_method_cache_flush_all(store);
     if (prop_query == NULL) {
         ossl_property_free(store->global_properties);
         store->global_properties = NULL;
         ossl_property_unlock(store);
         return 1;
     }
     store->global_properties = ossl_parse_query(prop_query);
     ret = store->global_properties != NULL;
     ossl_property_unlock(store);
     return ret;
 }

 static void impl_cache_flush_alg(ossl_uintmax_t idx, ALGORITHM *alg)
 {
     lh_QUERY_doall(alg->cache, &impl_cache_free);
     lh_QUERY_flush(alg->cache);
 }

 static void ossl_method_cache_flush(OSSL_METHOD_STORE *store, int nid)
 {
     ALGORITHM *alg = ossl_method_store_retrieve(store, nid);

     if (alg != NULL) {
         store->nelem -= lh_QUERY_num_items(alg->cache);
         impl_cache_flush_alg(0, alg);
     }
 }

 static void ossl_method_cache_flush_all(OSSL_METHOD_STORE *store)
 {
     ossl_sa_ALGORITHM_doall(store->algs, &impl_cache_flush_alg);
     store->nelem = 0;
 }

 IMPLEMENT_LHASH_DOALL_ARG(QUERY, IMPL_CACHE_FLUSH);

 /*
  * Flush an element from the query cache (perhaps).
  *
  * In order to avoid taking a write lock to keep accurate LRU information or
  * using atomic operations to approximate similar, the procedure used here
  * is to stochastically flush approximately half the cache.  Since generating
  * random numbers is relatively expensive, we produce them in blocks and
  * consume them as we go, saving generated bits between generations of flushes.
  *
  * This procedure isn't ideal, LRU would be better.  However, in normal
  * operation, reaching a full cache would be quite unexpected.  It means
  * that no steady state of algorithm queries has been reached.  I.e. it is most
  * likely an attack of some form.  A suboptimal clearance strategy that doesn't
  * degrade performance of the normal case is preferable to a more refined
  * approach that imposes a performance impact.
  */
 static void impl_cache_flush_cache(QUERY *c, IMPL_CACHE_FLUSH *state)
 {
     OSSL_METHOD_STORE *store = state->store;
     unsigned int n;

     if (store->nbits == 0) {
         if (!RAND_bytes(store->rand_bits, sizeof(store->rand_bits)))
             return;
         store->nbits = sizeof(store->rand_bits) * 8;
     }
     n = --store->nbits;
     if ((store->rand_bits[n >> 3] & (1 << (n & 7))) != 0)
         OPENSSL_free(lh_QUERY_delete(state->cache, c));
     else
         state->nelem++;
 }

 static void impl_cache_flush_one_alg(ossl_uintmax_t idx, ALGORITHM *alg,
                                      void *v)
 {
     IMPL_CACHE_FLUSH *state = (IMPL_CACHE_FLUSH *)v;

     state->cache = alg->cache;
     lh_QUERY_doall_IMPL_CACHE_FLUSH(state->cache, &impl_cache_flush_cache,
                                     state);
 }

 static void ossl_method_cache_flush_some(OSSL_METHOD_STORE *store)
 {
     IMPL_CACHE_FLUSH state;

     state.nelem = 0;
     state.store = store;
     ossl_sa_ALGORITHM_doall_arg(store->algs, &impl_cache_flush_one_alg, &state);
     store->need_flush = 0;
     store->nelem = state.nelem;
 }

 int ossl_method_store_cache_get(OSSL_METHOD_STORE *store, int nid,
                                 const char *prop_query, void **method)
 {
     ALGORITHM *alg;
     QUERY elem, *r;

     if (nid <= 0 || store == NULL)
         return 0;

     ossl_property_read_lock(store);
     alg = ossl_method_store_retrieve(store, nid);
     if (alg == NULL) {
         ossl_property_unlock(store);
         return 0;
     }

     elem.query = prop_query;
     r = lh_QUERY_retrieve(alg->cache, &elem);
     if (r == NULL) {
         ossl_property_unlock(store);
         return 0;
     }
     *method = r->method;
     ossl_property_unlock(store);
     return 1;
 }

 int ossl_method_store_cache_set(OSSL_METHOD_STORE *store, int nid,
                                 const char *prop_query, void *method)
 {
     QUERY elem, *old, *p = NULL;
     ALGORITHM *alg;
     size_t len;

     if (nid <= 0 || store == NULL)
         return 0;
     if (prop_query == NULL)
         return 1;

     ossl_property_write_lock(store);
     if (store->need_flush)
         ossl_method_cache_flush_some(store);
     alg = ossl_method_store_retrieve(store, nid);
     if (alg == NULL) {
         ossl_property_unlock(store);
         return 0;
     }

     if (method == NULL) {
         elem.query = prop_query;
         lh_QUERY_delete(alg->cache, &elem);
         ossl_property_unlock(store);
         return 1;
     }
     p = OPENSSL_malloc(sizeof(*p) + (len = strlen(prop_query)));
     if (p != NULL) {
         p->query = p->body;
         p->method = method;
         memcpy((char *)p->query, prop_query, len + 1);
         if ((old = lh_QUERY_insert(alg->cache, p)) != NULL)
             OPENSSL_free(old);
         if (old != NULL || !lh_QUERY_error(alg->cache)) {
             store->nelem++;
             if (store->nelem >= IMPL_CACHE_FLUSH_THRESHOLD)
                 store->need_flush = 1;
             ossl_property_unlock(store);
             return 1;
         }
     }
     ossl_property_unlock(store);
     OPENSSL_free(p);
     return 0;
 }
	/*
	* Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
	* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
	*
	* Licensed under the Apache License 2.0 (the "License"). You may not use
	* this file except in compliance with the License. You can obtain a copy
	* in the file LICENSE in the source distribution or at
	* https://www.openssl.org/source/license.html
	*/

	#include <string.h>
	#include <stdio.h>
	#include <stdarg.h>
	#include <openssl/crypto.h>
	#include "internal/property.h"
	#include "internal/ctype.h"
	#include <openssl/lhash.h>
	#include <openssl/rand.h>
	#include "internal/thread_once.h"
	#include "internal/lhash.h"
	#include "internal/sparse_array.h"
	#include "property_lcl.h"

	/* The number of elements in the query cache before we initiate a flush */
	#define IMPL_CACHE_FLUSH_THRESHOLD 500

	typedef struct {
	OSSL_PROPERTY_LIST *properties;
	void *method;
	void (method_destruct)(void );
	} IMPLEMENTATION;

	DEFINE_STACK_OF(IMPLEMENTATION)

	typedef struct {
	const char *query;
	void *method;
	char body[1];
	} QUERY;

	DEFINE_LHASH_OF(QUERY);

	typedef struct {
	int nid;
	STACK_OF(IMPLEMENTATION) *impls;
	LHASH_OF(QUERY) *cache;
	} ALGORITHM;

	struct ossl_method_store_st {
	size_t nelem;
	SPARSE_ARRAY_OF(ALGORITHM) *algs;
	OSSL_PROPERTY_LIST *global_properties;
	int need_flush;
	unsigned int nbits;
	unsigned char rand_bits[(IMPL_CACHE_FLUSH_THRESHOLD + 7) / 8];
	CRYPTO_RWLOCK *lock;
	};

	typedef struct {
	OSSL_METHOD_STORE *store;
	LHASH_OF(QUERY) *cache;
	size_t nelem;
	} IMPL_CACHE_FLUSH;

	DEFINE_SPARSE_ARRAY_OF(ALGORITHM);

	static void ossl_method_cache_flush(OSSL_METHOD_STORE *store, int nid);
	static void ossl_method_cache_flush_all(OSSL_METHOD_STORE *c);

	int ossl_property_read_lock(OSSL_METHOD_STORE *p)
	{
	return p != NULL ? CRYPTO_THREAD_read_lock(p->lock) : 0;
	}

	int ossl_property_write_lock(OSSL_METHOD_STORE *p)
	{
	return p != NULL ? CRYPTO_THREAD_write_lock(p->lock) : 0;
	}

	int ossl_property_unlock(OSSL_METHOD_STORE *p)
	{
	return p != 0 ? CRYPTO_THREAD_unlock(p->lock) : 0;
	}

	int ossl_method_store_init(void)
	{
	if (ossl_property_string_init()
	&& ossl_prop_defn_init()
	&& ossl_property_parse_init())
	return 1;

	ossl_method_store_cleanup();
	return 0;
	}

	void ossl_method_store_cleanup(void)
	{
	ossl_property_string_cleanup();
	ossl_prop_defn_cleanup();
	}

	static CRYPTO_ONCE method_store_init_flag = CRYPTO_ONCE_STATIC_INIT;
	DEFINE_RUN_ONCE_STATIC(do_method_store_init)
	{
	return OPENSSL_init_crypto(0, NULL)
	&& ossl_method_store_init()
	&& OPENSSL_atexit(&ossl_method_store_cleanup);
	}

	static unsigned long query_hash(const QUERY *a)
	{
	return OPENSSL_LH_strhash(a->query);
	}

	static int query_cmp(const QUERY a, const QUERY b)
	{
	return strcmp(a->query, b->query);
	}

	static void impl_free(IMPLEMENTATION *impl)
	{
	if (impl != NULL) {
	if (impl->method_destruct)
	impl->method_destruct(impl->method);
	OPENSSL_free(impl);
	}
	}

	static void impl_cache_free(QUERY *elem)
	{
	OPENSSL_free(elem);
	}

	static void alg_cleanup(ossl_uintmax_t idx, ALGORITHM *a)
	{
	if (a != NULL) {
	sk_IMPLEMENTATION_pop_free(a->impls, &impl_free);
	lh_QUERY_doall(a->cache, &impl_cache_free);
	lh_QUERY_free(a->cache);
	OPENSSL_free(a);
	}
	}

	OSSL_METHOD_STORE *ossl_method_store_new(void)
	{
	OSSL_METHOD_STORE *res;

	if (!RUN_ONCE(&method_store_init_flag, do_method_store_init))
	return 0;

	res = OPENSSL_zalloc(sizeof(*res));
	if (res != NULL) {
	if ((res->algs = ossl_sa_ALGORITHM_new()) == NULL) {
	OPENSSL_free(res);
	return NULL;
	}
	if ((res->lock = CRYPTO_THREAD_lock_new()) == NULL) {
	OPENSSL_free(res->algs);
	OPENSSL_free(res);
	return NULL;
	}
	}
	return res;
	}

	void ossl_method_store_free(OSSL_METHOD_STORE *store)
	{
	if (store != NULL) {
	ossl_sa_ALGORITHM_doall(store->algs, &alg_cleanup);
	ossl_sa_ALGORITHM_free(store->algs);
	ossl_property_free(store->global_properties);
	CRYPTO_THREAD_lock_free(store->lock);
	OPENSSL_free(store);
	}
	}

	static ALGORITHM ossl_method_store_retrieve(OSSL_METHOD_STORE store, int nid)
	{
	return ossl_sa_ALGORITHM_get(store->algs, nid);
	}

	static int ossl_method_store_insert(OSSL_METHOD_STORE store, ALGORITHM alg)
	{
	return ossl_sa_ALGORITHM_set(store->algs, alg->nid, alg);
	}

	int ossl_method_store_add(OSSL_METHOD_STORE *store,
	int nid, const char *properties,
	void method, void (method_destruct)(void *))
	{
	ALGORITHM *alg = NULL;
	IMPLEMENTATION *impl;
	int ret = 0;

	if (nid <= 0 \|\| method == NULL \|\| store == NULL)
	return 0;
	if (properties == NULL)
	properties = "";

	/* Create new entry */
	impl = OPENSSL_malloc(sizeof(*impl));
	if (impl == NULL)
	return 0;
	impl->method = method;
	impl->method_destruct = method_destruct;

	/*
	* Insert into the hash table if required.
	*
	* A write lock is used unconditionally because we wend our way down to the
	* property string code which isn't locking friendly.
	*/
	ossl_property_write_lock(store);
	ossl_method_cache_flush(store, nid);
	if ((impl->properties = ossl_prop_defn_get(properties)) == NULL) {
	if ((impl->properties = ossl_parse_property(properties)) == NULL)
	goto err;
	ossl_prop_defn_set(properties, impl->properties);
	}

	alg = ossl_method_store_retrieve(store, nid);
	if (alg == NULL) {
	if ((alg = OPENSSL_zalloc(sizeof(*alg))) == NULL
	\|\| (alg->impls = sk_IMPLEMENTATION_new_null()) == NULL
	\|\| (alg->cache = lh_QUERY_new(&query_hash, &query_cmp)) == NULL)
	goto err;
	alg->nid = nid;
	if (!ossl_method_store_insert(store, alg))
	goto err;
	}

	/* Push onto stack */
	if (sk_IMPLEMENTATION_push(alg->impls, impl))
	ret = 1;
	ossl_property_unlock(store);
	if (ret == 0)
	impl_free(impl);
	return ret;

	err:
	ossl_property_unlock(store);
	alg_cleanup(0, alg);
	impl_free(impl);
	return 0;
	}

	int ossl_method_store_remove(OSSL_METHOD_STORE *store, int nid,
	const void *method)
	{
	ALGORITHM *alg = NULL;
	int i;

	if (nid <= 0 \|\| method == NULL \|\| store == NULL)
	return 0;

	ossl_property_write_lock(store);
	ossl_method_cache_flush(store, nid);
	alg = ossl_method_store_retrieve(store, nid);
	if (alg == NULL) {
	ossl_property_unlock(store);
	return 0;
	}

	/*
	* A sorting find then a delete could be faster but these stacks should be
	* relatively small, so we avoid the overhead. Sorting could also surprise
	* users when result orderings change (even though they are not guaranteed).
	*/
	for (i = 0; i < sk_IMPLEMENTATION_num(alg->impls); i++) {
	IMPLEMENTATION *impl = sk_IMPLEMENTATION_value(alg->impls, i);

	if (impl->method == method) {
	sk_IMPLEMENTATION_delete(alg->impls, i);
	ossl_property_unlock(store);
	impl_free(impl);
	return 1;
	}
	}
	ossl_property_unlock(store);
	return 0;
	}

	int ossl_method_store_fetch(OSSL_METHOD_STORE *store, int nid,
	const char prop_query, void *method)
	{
	ALGORITHM *alg;
	IMPLEMENTATION *impl;
	OSSL_PROPERTY_LIST pq = NULL, p2;
	int ret = 0;
	int j;

	if (nid <= 0 \|\| method == NULL \|\| store == NULL)
	return 0;

	/*
	* This only needs to be a read lock, because queries never create property
	* names or value and thus don't modify any of the property string layer.
	*/
	ossl_property_read_lock(store);
	alg = ossl_method_store_retrieve(store, nid);
	if (alg == NULL) {
	ossl_property_unlock(store);
	return 0;
	}

	if (prop_query == NULL) {
	if ((impl = sk_IMPLEMENTATION_value(alg->impls, 0)) != NULL) {
	*method = impl->method;
	ret = 1;
	}
	goto fin;
	}
	pq = ossl_parse_query(prop_query);
	if (pq == NULL)
	goto fin;
	if (store->global_properties != NULL) {
	p2 = ossl_property_merge(pq, store->global_properties);
	if (p2 == NULL)
	goto fin;
	ossl_property_free(pq);
	pq = p2;
	}
	for (j = 0; j < sk_IMPLEMENTATION_num(alg->impls); j++) {
	impl = sk_IMPLEMENTATION_value(alg->impls, j);

	if (ossl_property_match(pq, impl->properties)) {
	*method = impl->method;
	ret = 1;
	goto fin;
	}
	}
	fin:
	ossl_property_unlock(store);
	ossl_property_free(pq);
	return ret;
	}

	int ossl_method_store_set_global_properties(OSSL_METHOD_STORE *store,
	const char *prop_query) {
	int ret = 0;

	if (store == NULL)
	return 1;

	ossl_property_write_lock(store);
	ossl_method_cache_flush_all(store);
	if (prop_query == NULL) {
	ossl_property_free(store->global_properties);
	store->global_properties = NULL;
	ossl_property_unlock(store);
	return 1;
	}
	store->global_properties = ossl_parse_query(prop_query);
	ret = store->global_properties != NULL;
	ossl_property_unlock(store);
	return ret;
	}

	static void impl_cache_flush_alg(ossl_uintmax_t idx, ALGORITHM *alg)
	{
	lh_QUERY_doall(alg->cache, &impl_cache_free);
	lh_QUERY_flush(alg->cache);
	}

	static void ossl_method_cache_flush(OSSL_METHOD_STORE *store, int nid)
	{
	ALGORITHM *alg = ossl_method_store_retrieve(store, nid);

	if (alg != NULL) {
	store->nelem -= lh_QUERY_num_items(alg->cache);
	impl_cache_flush_alg(0, alg);
	}
	}

	static void ossl_method_cache_flush_all(OSSL_METHOD_STORE *store)
	{
	ossl_sa_ALGORITHM_doall(store->algs, &impl_cache_flush_alg);
	store->nelem = 0;
	}

	IMPLEMENT_LHASH_DOALL_ARG(QUERY, IMPL_CACHE_FLUSH);

	/*
	* Flush an element from the query cache (perhaps).
	*
	* In order to avoid taking a write lock to keep accurate LRU information or
	* using atomic operations to approximate similar, the procedure used here
	* is to stochastically flush approximately half the cache. Since generating
	* random numbers is relatively expensive, we produce them in blocks and
	* consume them as we go, saving generated bits between generations of flushes.
	*
	* This procedure isn't ideal, LRU would be better. However, in normal
	* operation, reaching a full cache would be quite unexpected. It means
	* that no steady state of algorithm queries has been reached. I.e. it is most
	* likely an attack of some form. A suboptimal clearance strategy that doesn't
	* degrade performance of the normal case is preferable to a more refined
	* approach that imposes a performance impact.
	*/
	static void impl_cache_flush_cache(QUERY c, IMPL_CACHE_FLUSH state)
	{
	OSSL_METHOD_STORE *store = state->store;
	unsigned int n;

	if (store->nbits == 0) {
	if (!RAND_bytes(store->rand_bits, sizeof(store->rand_bits)))
	return;
	store->nbits = sizeof(store->rand_bits) * 8;
	}
	n = --store->nbits;
	if ((store->rand_bits[n >> 3] & (1 << (n & 7))) != 0)
	OPENSSL_free(lh_QUERY_delete(state->cache, c));
	else
	state->nelem++;
	}

	static void impl_cache_flush_one_alg(ossl_uintmax_t idx, ALGORITHM *alg,
	void *v)
	{
	IMPL_CACHE_FLUSH state = (IMPL_CACHE_FLUSH )v;

	state->cache = alg->cache;
	lh_QUERY_doall_IMPL_CACHE_FLUSH(state->cache, &impl_cache_flush_cache,
	state);
	}

	static void ossl_method_cache_flush_some(OSSL_METHOD_STORE *store)
	{
	IMPL_CACHE_FLUSH state;

	state.nelem = 0;
	state.store = store;
	ossl_sa_ALGORITHM_doall_arg(store->algs, &impl_cache_flush_one_alg, &state);
	store->need_flush = 0;
	store->nelem = state.nelem;
	}

	int ossl_method_store_cache_get(OSSL_METHOD_STORE *store, int nid,
	const char prop_query, void *method)
	{
	ALGORITHM *alg;
	QUERY elem, *r;

	if (nid <= 0 \|\| store == NULL)
	return 0;

	ossl_property_read_lock(store);
	alg = ossl_method_store_retrieve(store, nid);
	if (alg == NULL) {
	ossl_property_unlock(store);
	return 0;
	}

	elem.query = prop_query;
	r = lh_QUERY_retrieve(alg->cache, &elem);
	if (r == NULL) {
	ossl_property_unlock(store);
	return 0;
	}
	*method = r->method;
	ossl_property_unlock(store);
	return 1;
	}

	int ossl_method_store_cache_set(OSSL_METHOD_STORE *store, int nid,
	const char prop_query, void method)
	{
	QUERY elem, old, p = NULL;
	ALGORITHM *alg;
	size_t len;

	if (nid <= 0 \|\| store == NULL)
	return 0;
	if (prop_query == NULL)
	return 1;

	ossl_property_write_lock(store);
	if (store->need_flush)
	ossl_method_cache_flush_some(store);
	alg = ossl_method_store_retrieve(store, nid);
	if (alg == NULL) {
	ossl_property_unlock(store);
	return 0;
	}

	if (method == NULL) {
	elem.query = prop_query;
	lh_QUERY_delete(alg->cache, &elem);
	ossl_property_unlock(store);
	return 1;
	}
	p = OPENSSL_malloc(sizeof(*p) + (len = strlen(prop_query)));
	if (p != NULL) {
	p->query = p->body;
	p->method = method;
	memcpy((char *)p->query, prop_query, len + 1);
	if ((old = lh_QUERY_insert(alg->cache, p)) != NULL)
	OPENSSL_free(old);
	if (old != NULL \|\| !lh_QUERY_error(alg->cache)) {
	store->nelem++;
	if (store->nelem >= IMPL_CACHE_FLUSH_THRESHOLD)
	store->need_flush = 1;
	ossl_property_unlock(store);
	return 1;
	}
	}
	ossl_property_unlock(store);
	OPENSSL_free(p);
	return 0;
	}