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/********************************************************************************/
/* */
/* Private Exponent D cache functions */
/* Written by Stefan Berger */
/* IBM Thomas J. Watson Research Center */
/* */
/* Licenses and Notices */
/* */
/* 1. Copyright Licenses: */
/* */
/* - Trusted Computing Group (TCG) grants to the user of the source code in */
/* this specification (the "Source Code") a worldwide, irrevocable, */
/* nonexclusive, royalty free, copyright license to reproduce, create */
/* derivative works, distribute, display and perform the Source Code and */
/* derivative works thereof, and to grant others the rights granted herein. */
/* */
/* - The TCG grants to the user of the other parts of the specification */
/* (other than the Source Code) the rights to reproduce, distribute, */
/* display, and perform the specification solely for the purpose of */
/* developing products based on such documents. */
/* */
/* 2. Source Code Distribution Conditions: */
/* */
/* - Redistributions of Source Code must retain the above copyright licenses, */
/* this list of conditions and the following disclaimers. */
/* */
/* - Redistributions in binary form must reproduce the above copyright */
/* licenses, this list of conditions and the following disclaimers in the */
/* documentation and/or other materials provided with the distribution. */
/* */
/* 3. Disclaimers: */
/* */
/* - THE COPYRIGHT LICENSES SET FORTH ABOVE DO NOT REPRESENT ANY FORM OF */
/* LICENSE OR WAIVER, EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, WITH */
/* RESPECT TO PATENT RIGHTS HELD BY TCG MEMBERS (OR OTHER THIRD PARTIES) */
/* THAT MAY BE NECESSARY TO IMPLEMENT THIS SPECIFICATION OR OTHERWISE. */
/* Contact TCG Administration (admin@trustedcomputinggroup.org) for */
/* information on specification licensing rights available through TCG */
/* membership agreements. */
/* */
/* - THIS SPECIFICATION IS PROVIDED "AS IS" WITH NO EXPRESS OR IMPLIED */
/* WARRANTIES WHATSOEVER, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR */
/* FITNESS FOR A PARTICULAR PURPOSE, ACCURACY, COMPLETENESS, OR */
/* NONINFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS, OR ANY WARRANTY */
/* OTHERWISE ARISING OUT OF ANY PROPOSAL, SPECIFICATION OR SAMPLE. */
/* */
/* - Without limitation, TCG and its members and licensors disclaim all */
/* liability, including liability for infringement of any proprietary */
/* rights, relating to use of information in this specification and to the */
/* implementation of this specification, and TCG disclaims all liability for */
/* cost of procurement of substitute goods or services, lost profits, loss */
/* of use, loss of data or any incidental, consequential, direct, indirect, */
/* or special damages, whether under contract, tort, warranty or otherwise, */
/* arising in any way out of use or reliance upon this specification or any */
/* information herein. */
/* */
/* (c) Copyright IBM Corp., 2021 */
/* */
/********************************************************************************/
#include "Tpm.h"
#include "ExpDCache_fp.h"
/* Implement a cache for the private exponent D so it doesn't need to be
* recalculated every time from P, Q, E and N (modulus). The cache has a
* number of entries that cache D and use P, Q, and E for lookup.
* A least-recently-used cache eviction strategy is implemented that evicts
* the oldest cache entry in case space is needed. An entry is young once
* it is added or made young when it was found via lookup. All other entries
* age by '1' when an entry is added or accessed.
*/
struct ExpDCacheEntry {
/* The age of the entry; the higher the number the more likely it
* will be evicted soon
*/
unsigned int age;
BIGNUM *P; /* input */
BIGNUM *N; /* input */
BIGNUM *E; /* input */
BIGNUM *Q; /* cached */
BIGNUM *D; /* cached */
};
#define DCACHE_NUM_ENTRIES 64
static struct ExpDCacheEntry ExpDCache[DCACHE_NUM_ENTRIES];
/* Increment the age of all cache entries that have a current age <= maxage */
static void ExpDCacheIncrementAge(unsigned maxage)
{
size_t i;
for (i = 0; i < ARRAY_SIZE(ExpDCache); i++) {
if (ExpDCache[i].age <= maxage && ExpDCache[i].D != NULL)
ExpDCache[i].age++;
}
}
/* Free the data associated with a ExpDCacheEntry and initialize it */
static void ExpDCacheEntryFree(struct ExpDCacheEntry *dce)
{
BN_clear_free(dce->P);
BN_free(dce->N);
BN_free(dce->E);
BN_clear_free(dce->Q);
BN_clear_free(dce->D);
memset(dce, 0, sizeof(*dce));
}
void ExpDCacheFree(void)
{
size_t i;
for (i = 0; i < ARRAY_SIZE(ExpDCache); i++)
ExpDCacheEntryFree(&ExpDCache[i]);
}
/* Get a ExpDCacheEntry by finding either an unused entry or evicting the oldest
* entry. The returned entry will have all NULL pointers and age 0.
*/
static struct ExpDCacheEntry *ExpDCacheEntryGet(void)
{
size_t i, use_i = 0;
unsigned oldest_age = 0;
struct ExpDCacheEntry *dce;
for (i = 0; i < ARRAY_SIZE(ExpDCache); i++) {
if (ExpDCache[i].D == NULL) {
/* use this free entry */
use_i = i;
break;
}
if (ExpDCache[i].age > oldest_age) {
/* this one is currently the oldest */
use_i = i;
oldest_age = ExpDCache[i].age;
}
}
dce = &ExpDCache[use_i];
ExpDCacheEntryFree(dce);
return dce;
}
/* Add 'D' to the ExpDCache. This function does not check for duplicates */
void ExpDCacheAdd(const BIGNUM *P, const BIGNUM *N, const BIGNUM *E,
const BIGNUM *Q, const BIGNUM *D)
{
struct ExpDCacheEntry *dce = ExpDCacheEntryGet();
/* age of 'dce' is '0' */
dce->P = BN_dup(P);
dce->N = BN_dup(N);
dce->E = BN_dup(E);
dce->Q = BN_dup(Q);
dce->D = BN_dup(D);
if (!dce->P || !dce->N || !dce->E || !dce->Q || !dce->D)
ExpDCacheEntryFree(dce);
else
ExpDCacheIncrementAge(~0);
}
BIGNUM *ExpDCacheFind(const BIGNUM *P, const BIGNUM *N, const BIGNUM *E, BIGNUM **Q)
{
size_t i;
unsigned myage;
BIGNUM *D;
for (i = 0; i < ARRAY_SIZE(ExpDCache); i++) {
if (BN_cmp(ExpDCache[i].P, P) == 0 && BN_cmp(ExpDCache[i].N, N) == 0 &&
BN_cmp(ExpDCache[i].E, E) == 0) {
/* entry found */
myage = ExpDCache[i].age;
/* mark this entry as most recently used */
ExpDCache[i].age = 0;
/* Increment everyone who is <= 'myage'.
* The age of this entry will be '1' after that.
*/
ExpDCacheIncrementAge(myage);
*Q = BN_dup(ExpDCache[i].Q);
if (*Q == NULL)
return NULL;
D = BN_dup(ExpDCache[i].D);
if (D == NULL) {
BN_clear_free(*Q);
*Q = NULL;
return NULL;
}
BN_set_flags(*Q, BN_FLG_CONSTTIME);
BN_set_flags(D, BN_FLG_CONSTTIME);
return D;
}
}
return NULL;
}
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