path: root/engines/ccgost/gost94_keyx.c

/**********************************************************************
 *                             gost94_keyx.c                          *
 *             Copyright (c) 2005-2006 Cryptocom LTD                  *
 *         This file is distributed under the same license as OpenSSL *
 *                                                                    *
 *     Implements generation and parsing of GOST_KEY_TRANSPORT for    *
 *     			GOST R 34.10-94 algorithms                            *
 *																	  *
 *          Requires OpenSSL 0.9.9 for compilation                    *
 **********************************************************************/
#include <string.h>
#include <openssl/dh.h>
#include <openssl/rand.h>
#include <openssl/evp.h>
#include <openssl/objects.h>

#include "gost89.h"
#include "gosthash.h"
#include "e_gost_err.h"
#include "gost_keywrap.h"
#include "gost_lcl.h"
/* Common functions for both 94 and 2001 key exchange schemes */
int decrypt_cryptocom_key(unsigned char *sess_key,int max_key_len,
	const unsigned char *crypted_key,int crypted_key_len, gost_ctx *ctx)
	{
	int i;
	int j;
	int blocks = crypted_key_len >>3;
	unsigned char gamma[8];
	if (max_key_len <crypted_key_len)
		{
		GOSTerr(GOST_F_DECRYPT_CRYPTOCOM_KEY,GOST_R_NOT_ENOUGH_SPACE_FOR_KEY);
		return 0;
		}	
	if ((crypted_key_len & 7) !=0) 
		{
		GOSTerr(GOST_F_DECRYPT_CRYPTOCOM_KEY,GOST_R_INVALID_ENCRYPTED_KEY_SIZE);
		return 0;
		}	
	for (i=blocks-1;i>0;i--) 
		{
		gostcrypt(ctx,crypted_key+(i-1)*8,gamma);
		for(j=0;j<8;j++) 
			{
			sess_key[i*8+j]=gamma[j]^crypted_key[i*8+j];
			}
		}	
	gostcrypt(ctx,sess_key+crypted_key_len-8,gamma);	
	for(j=0;j<8;j++) 
		{
		sess_key[j]=gamma[j]^crypted_key[j];
		}
	return 1;
	}
int encrypt_cryptocom_key(const unsigned char *sess_key,int key_len,
	unsigned char *crypted_key, gost_ctx *ctx)
	{
	int i;
	int j;
	unsigned char gamma[8];
	memcpy(gamma,sess_key+key_len-8,8);
	for (i=0;i<key_len;i+=8)
		{
		gostcrypt(ctx,gamma,gamma);
		for (j=0;j<8;j++)
			gamma[j]=crypted_key[i+j]=sess_key[i+j]^gamma[j];
		}
	return 1;
	}
/* Implementation of the Diffi-Hellman key agreement scheme based on
 * GOST-94 keys */

/* Computes Diffie-Hellman key and stores it into buffer in
 * little-endian byte order as expected by both versions of GOST 94
 * algorigthm
 */
static int compute_pair_key_le(unsigned char *pair_key,BIGNUM *pub_key,DH *dh) 
	{
	unsigned char be_key[128];
	int i,key_size;
	key_size=DH_compute_key(be_key,pub_key,dh);
	if (!key_size) return 0;
	memset(pair_key,0,128);
	for (i=0;i<key_size;i++)
		{
		pair_key[i]=be_key[key_size-1-i];
		}
	return key_size;	
	}	
/*
 * Computes 256 bit key exchange key for CryptoCom variation of GOST 94
 * algorithm
 */
static int make_gost_shared_key(DH *dh,EVP_PKEY *pubk,unsigned char *shared_key) 
	{
	unsigned char dh_key [128];
	int i;
	/* Compute key */
	memset(dh_key,0,128);
	if (!compute_pair_key_le(dh_key,((DSA *)EVP_PKEY_get0(pubk))->pub_key,dh)) return 0;	
	/* Fold it down to 256 bit */
	/* According to GOST  either 2^1020<p<2^1024 or 
	 * 2^509<p<2^512, so DH_size can be exactly 128 or exactly 64 only
	 */
	
	if (DH_size(dh)==128)
		{
		for (i=0;i<64;i++)
			{
			dh_key[i]^=dh_key[64+i];
			}
		}
	for (i=0;i<32;i++)
		{
		shared_key[i]=dh_key[i]^dh_key[32+i];
		}
	return 1;
	}

static DH *make_ephemeral_key(EVP_PKEY *pubk,BIGNUM *ephemeral_key)
	{
	DH *dh = DH_new();
	dh->g = BN_dup(pubk->pkey.dsa->g);
	dh->p = BN_dup(pubk->pkey.dsa->p);
	dh->priv_key = BN_dup(ephemeral_key);
	/* Generate ephemeral key pair */
	if (!DH_generate_key(dh))
		{
		DH_free(dh);
		return NULL;
		}	
	return dh;
	}	
/*
 * Computes 256 bit Key exchange key as specified in RFC 4357 
 */
static int make_cp_exchange_key(DH *dh,EVP_PKEY *pubk, unsigned char *shared_key)
	{
	unsigned char dh_key [128];
	gost_hash_ctx hash_ctx;
	memset(dh_key,0,128);
	if (!compute_pair_key_le(dh_key,((DSA *)(EVP_PKEY_get0(pubk)))->pub_key,dh)) return 0;
	init_gost_hash_ctx(&hash_ctx,&GostR3411_94_CryptoProParamSet);
	start_hash(&hash_ctx);
	hash_block(&hash_ctx,dh_key,128);
	finish_hash(&hash_ctx,shared_key);
	done_gost_hash_ctx(&hash_ctx);
	return 1;
	}

/* EVP_PKEY_METHOD callback encrypt for
 * GOST R 34.10-94 cryptopro modification
 */

int pkey_GOST94cp_encrypt(EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen, const unsigned char* key, size_t key_len ) 
	{
	GOST_KEY_TRANSPORT *gkt=NULL;
	DH *dh = NULL;
	unsigned char shared_key[32], ukm[8],crypted_key[44];
	const struct gost_cipher_info *param=get_encryption_params(NULL);
	EVP_PKEY *pubk = EVP_PKEY_CTX_get0_pkey(ctx);
	struct gost_pmeth_data *data = EVP_PKEY_CTX_get_data(ctx);
	int size=-1;
	gost_ctx cctx;

	if (!(data->eph_seckey))
		{
		GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
			GOST_R_CTX_NOT_INITIALIZED_FOR_ENCRYPT);
		return -1;
		}	

	dh = make_ephemeral_key(pubk,gost_get_priv_key(data->eph_seckey));
	gost_init(&cctx,param->sblock);	
	make_cp_exchange_key(dh,pubk,shared_key);
	if (RAND_bytes(ukm,8)<=0)
		{
		GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
			GOST_R_RANDOM_GENERATOR_FAILURE);
		return -1;
		}	
	keyWrapCryptoPro(&cctx,shared_key,ukm,key,crypted_key);
	gkt = GOST_KEY_TRANSPORT_new();
	if (!gkt)
		{
		goto memerr;
		}	
	if(!ASN1_OCTET_STRING_set(gkt->key_agreement_info->eph_iv,
			ukm,8))
		{
		goto memerr;
		}	
	if (!ASN1_OCTET_STRING_set(gkt->key_info->imit,crypted_key+40,4))
		{
		goto memerr;
		}
	if (!ASN1_OCTET_STRING_set(gkt->key_info->encrypted_key,crypted_key+8,32))
		{
		goto memerr;
		}
	if (!X509_PUBKEY_set(&gkt->key_agreement_info->ephem_key,data->eph_seckey))
		{
		GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,GOST_R_CANNOT_PACK_EPHEMERAL_KEY);
		goto err;
		}	
	ASN1_OBJECT_free(gkt->key_agreement_info->cipher);
	gkt->key_agreement_info->cipher = OBJ_nid2obj(param->nid);
	*outlen = i2d_GOST_KEY_TRANSPORT(gkt,&out);
	if (!size)
		{
		GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,GOST_R_ERROR_PACKING_KEY_TRANSPORT_INFO);
		size=-1;
		}
	GOST_KEY_TRANSPORT_free(gkt);
	DH_free(dh);
	return 1;	
	memerr:
	GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
		GOST_R_MALLOC_FAILURE);
	er