/**********************************************************************
 *                          gost_keyx.c                               *
 *             Copyright (c) 2005-2006 Cryptocom LTD                  *
 *         This file is distributed under the same license as OpenSSL *
 *                                                                    *
 *   VK0 34.10-2001 key exchange and GOST R 34.10-2001                *
 *   based PKCS7/SMIME support                                        *
 *          Requires OpenSSL 0.9.9 for compilation                    *
 **********************************************************************/
#include <openssl/evp.h>
#include <openssl/rand.h>
#include <string.h>
#include <openssl/objects.h>
#include "gost89.h"
#include "gosthash.h"
#include "e_gost_err.h"
#include "gost_keywrap.h"
#include "gost_lcl.h"
#include "gost2001_keyx.h"


/* Implementation of CryptoPro VKO 34.10-2001 algorithm */
static int VKO_compute_key(unsigned char *shared_key,size_t shared_key_size,const EC_POINT *pub_key,EC_KEY *priv_key,const unsigned char *ukm)
	{
	unsigned char ukm_be[8],databuf[64],hashbuf[64];
	BIGNUM *UKM=NULL,*p=NULL,*order=NULL,*X=NULL,*Y=NULL;
	const BIGNUM* key=EC_KEY_get0_private_key(priv_key);
	EC_POINT *pnt=EC_POINT_new(EC_KEY_get0_group(priv_key));
	int i;
	gost_hash_ctx hash_ctx;
	BN_CTX *ctx = BN_CTX_new();

	for (i=0;i<8;i++)
		{
		ukm_be[7-i]=ukm[i];
		}
	BN_CTX_start(ctx);
	UKM=getbnfrombuf(ukm_be,8);
	p=BN_CTX_get(ctx);
	order = BN_CTX_get(ctx);
	X=BN_CTX_get(ctx);
	Y=BN_CTX_get(ctx);
	EC_GROUP_get_order(EC_KEY_get0_group(priv_key),order,ctx);
	BN_mod_mul(p,key,UKM,order,ctx);	
	EC_POINT_mul(EC_KEY_get0_group(priv_key),pnt,NULL,pub_key,p,ctx);
	EC_POINT_get_affine_coordinates_GFp(EC_KEY_get0_group(priv_key),
		pnt,X,Y,ctx);
	/*Serialize elliptic curve point same way as we do it when saving
	 * key */
	store_bignum(Y,databuf,32);
	store_bignum(X,databuf+32,32);
 	/* And reverse byte order of whole buffer */
	for (i=0;i<64;i++)
		{
		hashbuf[63-i]=databuf[i];
		}
	init_gost_hash_ctx(&hash_ctx,&GostR3411_94_CryptoProParamSet);
	start_hash(&hash_ctx);
	hash_block(&hash_ctx,hashbuf,64);
	finish_hash(&hash_ctx,shared_key);
	done_gost_hash_ctx(&hash_ctx);
	BN_free(UKM);
	BN_CTX_end(ctx);
	BN_CTX_free(ctx);
	EC_POINT_free(pnt);
	return 32;
	}


/*
 * EVP_PKEY_METHOD callback derive. Implements VKO R 34.10-2001
 * algorithm
 */
int pkey_gost2001_derive(EVP_PKEY_CTX *ctx, unsigned char *key, size_t *keylen)
{
	/* Public key of peer in the ctx field peerkey
	 * Our private key in the ctx pkey
	 * ukm is in the algorithm specific context data
	 */
	EVP_PKEY *my_key = EVP_PKEY_CTX_get0_pkey(ctx);
	EVP_PKEY *peer_key = EVP_PKEY_CTX_get0_peerkey(ctx);
	struct gost_pmeth_data *data = EVP_PKEY_CTX_get_data(ctx);
	
	if (!data->shared_ukm) {
		GOSTerr(GOST_F_PKEY_GOST2001_DERIVE, GOST_R_UKM_NOT_SET);
		return 0;
	}	

	if (key == NULL) {
		*keylen = 32;
		return 32;
	}	
	
	*keylen=VKO_compute_key(key, 32, EC_KEY_get0_public_key(EVP_PKEY_get0(peer_key)),
		(EC_KEY *)EVP_PKEY_get0(my_key),data->shared_ukm);
	return 1;	
}


/*  
 * EVP_PKEY_METHOD callback encrypt  
 * Implementation of GOST2001 key transport, cryptocom variation 
 */
/* Generates ephemeral key based on pubk algorithm
 * computes shared key using VKO and returns filled up
 * GOST_KEY_TRANSPORT structure
 */

/*  
 * EVP_PKEY_METHOD callback encrypt  
 * Implementation of GOST2001 key transport, cryptopo variation 
 */

int pkey_GOST01cp_encrypt(EVP_PKEY_CTX *pctx, unsigned char *out, size_t *out_len, const unsigned char *key,size_t key_len) 
	{
	GOST_KEY_TRANSPORT *gkt=NULL; 
	EVP_PKEY *pubk = EVP_PKEY_CTX_get0_pkey(pctx);
	struct gost_pmeth_data *data = EVP_PKEY_CTX_get_data(pctx);
	const struct gost_cipher_info *param=get_encryption_params(NULL);
	unsigned char ukm[8], shared_key[32], crypted_key[44];
	int ret=0;
	int key_is_ephemeral=1;
	gost_ctx cctx;
	EVP_PKEY *sec_key=EVP_PKEY_CTX_get0_peerkey(pctx);
	if (data->shared_ukm) 
		{
		memcpy(ukm, data->shared_ukm,8);
		} 
	else if (out) 
		{
		
		if (RAND_bytes(ukm,8)<=0)
			{
			GOSTerr(GOST_F_PKEY_GOST01CP_ENCRYPT,
				GOST_R_RANDOM_GENERATOR_FAILURE);
			return 0;
			}	
		}	
	/* Check for private key in the peer_key of context */	
	if (sec_key) 
		{
		key_is_ephemeral=0;
		if (!gost_get0_priv_key(sec_key)) 
			{
			GOSTerr(GOST_F_PKEY_GOST01CP_ENCRYPT,
			GOST_R_NO_PRIVATE_PART_OF_NON_EPHEMERAL_KEYPAIR);
			goto err;
			}	
		} 
	else 
		{
		key_is_ephemeral=1;
		if (out) 
			{
			sec_key = EVP_PKEY_new();
			EVP_PKEY_assign(sec_key,EVP_PKEY_base_id(pubk),EC_KEY_new());
			EVP_PKEY_copy_parameters(sec_key,pubk);
			if (!gost2001_keygen(EVP_PKEY_get0(sec_key))) 
				{
				goto err;
				}	
			}
		}
	if (!get_gost_engine_param(GOST_PARAM_CRYPT_PARAMS) && param ==  gost_cipher_list)
		{
		param= gost_cipher_list+1;
		}	
    if (out) 
		{
		VKO_compute_key(shared_key,32,EC_KEY_get0_public_key(EVP_PKEY_get0(pubk)),EVP_PKEY_get0(sec_key),ukm);
		gost_init(&cctx,param->sblock);	
		keyWrapCryptoPro(&cctx,shared_key,ukm,key,crypted_key);
		}
	gkt = GOST_KEY_TRANSPORT_new();
	if (!gkt)
		{
		goto err;
		}	
	if(!ASN1_OCTET_STRING_set(gkt->key_agreement_info->eph_iv,
			ukm,8))
		{
		goto err;
		}	
	if (!ASN1_OCTET_STRING_set(gkt->key_info->imit,crypted_key+40,4))
		{
		goto err;
		}
	if (!ASN1_OCTET_STRING_set(gkt->key_info->encrypted_key,crypted_key+8,32))
		{
		goto err;
		}
	if (key_is_ephemeral) {	
		if (!X509_PUBKEY_set(&gkt->key_agreement_info->ephem_key,out?sec_key:pubk))
			{
			GOSTerr(GOST_F_PKEY_GOST01CP_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);
	if (key_is_ephemeral && sec_key) EVP_PKEY_free(sec_key);
	if (!key_is_ephemeral)
		{
		/* Set control "public key from client certificate used" */
		if (EVP_PKEY_CTX_ctrl(pctx, -1, -1, EVP_PKEY_CTRL_PEER_KEY, 3, NULL) <= 0)
			{
			GOSTerr(GOST_F_PKEY_GOST01CP_ENCRYPT,
				GOST_R_CTRL_CALL_FAILED);
			goto err;
			}
		}
	if ((*out_len = i2d_GOST_KEY_TRANSPORT(gkt,out?&out:NULL))>0) ret =1;
	GOST_KEY_TRANSPORT_free(gkt);
	return ret;	
	err:		
	if (key_is_ephemeral && sec_key) EVP_PKEY_free(sec_key);
	GOST_KEY_TRANSPORT_free(gkt);
	return -1;
	}
/*  
 * EVP_PKEY_METHOD callback decrypt  
 * Implementation of GOST2001 key transport, cryptopo variation 
 */
int pkey_GOST01cp_decrypt(EVP_PKEY_CTX *pctx, unsigned char *key, size_t * key_len, const unsigned char *in, size_t in_len)
	{
	const unsigned char *p = in;
	EVP_PKEY *priv = EVP_PKEY_CTX_get0_pkey(pctx);
	GOST_KEY_TRANSPORT *gkt = NULL;
	int ret=0;	
	unsigned char wrappedKey[44];
	unsigned char sharedKey[32];
	gost_ctx ctx;
	const struct gost_cipher_info *param=NULL;
	EVP_PKEY *eph_key=NULL, *peerkey=NULL;

	if (!key)
		{
		*key_len = 32;
		return 1;
		}	
	gkt = d2i_GOST_KEY_TRANSPORT(NULL,(const unsigned char **)&p,
		in_len);
	if (!gkt)
		{
		GOSTerr(GOST_F_PKEY_GOST01CP_DECRYPT,GOST_R_ERROR_PARSING_KEY_TRANSPORT_INFO);
		return -1;
		}	

	/* If key transport structure contains public key, use it */
	eph_key = X509_PUBKEY_get(gkt->key_agreement_info->ephem_key);
	if (eph_key)
		{
		if (EVP_PKEY_derive_set_peer(pctx, eph_key) <= 0)
			{
			GOSTerr(GOST_F_PKEY_GOST01CP_DECRYPT,
				GOST_R_INCOMPATIBLE_PEER_KEY);
			goto err;
			}
		}
	else
		{
		/* Set control "public key from client certificate used" */
		if (EVP_PKEY_CTX_ctrl(pctx, -1, -1, EVP_PKEY_CTRL_PEER_KEY, 3, NULL) <= 0)
			{
			GOSTerr(GOST_F_PKEY_GOST01CP_DECRYPT,
				GOST_R_CTRL_CALL_FAILED);
			goto err;
			}
		}
	peerkey = EVP_PKEY_CTX_get0_peerkey(pctx);
	if (!peerkey)
		{
		GOSTerr(GOST_F_PKEY_GOST01CP_DECRYPT,
			GOST_R_NO_PEER_KEY);
		goto err;
		}
		
	param = get_encryption_params(gkt->key_agreement_info->cipher);
	gost_init(&ctx,param->sblock);	
	OPENSSL_assert(gkt->key_agreement_info->eph_iv->length==8);
	memcpy(wrappedKey,gkt->key_agreement_info->eph_iv->data,8);
	OPENSSL_assert(gkt->key_info->encrypted_key->length==32);
	memcpy(wrappedKey+8,gkt->key_info->encrypted_key->data,32);
	OPENSSL_assert(gkt->key_info->imit->length==4);
	memcpy(wrappedKey+40,gkt->key_info->imit->data,4);	
	VKO_compute_key(sharedKey,32,EC_KEY_get0_public_key(EVP_PKEY_get0(peerkey)),
		EVP_PKEY_get0(priv),wrappedKey);
	if (!keyUnwrapCryptoPro(&ctx,sharedKey,wrappedKey,key))
		{
		GOSTerr(GOST_F_PKEY_GOST01CP_DECRYPT,
			GOST_R_ERROR_COMPUTING_SHARED_KEY);
		goto err;
		}	
				
	ret=1;
err:	
	if (eph_key) EVP_PKEY_free(eph_key);
	if (gkt) GOST_KEY_TRANSPORT_free(gkt);
	return ret;
	}