gost94_keyx.c

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/**********************************************************************
 *                             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 */
/* 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
 * algorithm
 */
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 as specified in RFC 4357 
 */
static int make_cp_exchange_key(BIGNUM *priv_key,EVP_PKEY *pubk, unsigned char *shared_key)
    {
    unsigned char dh_key [128];
    int ret;
    gost_hash_ctx hash_ctx;
    DH *dh = DH_new();
    
    if (!dh)
        return 0;
    memset(dh_key,0,128);
    dh->g = BN_dup(pubk->pkey.dsa->g);
    dh->p = BN_dup(pubk->pkey.dsa->p);
    dh->priv_key = BN_dup(priv_key);
    ret=compute_pair_key_le(dh_key,((DSA *)(EVP_PKEY_get0(pubk)))->pub_key,dh) ;
    DH_free(dh);
    if (!ret)   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 derive. Implements VKO R 34.10-94 */

int pkey_gost94_derive(EVP_PKEY_CTX *ctx,unsigned char *key,size_t *keylen)
    {
        EVP_PKEY *pubk = EVP_PKEY_CTX_get0_peerkey(ctx);
        EVP_PKEY *mykey = EVP_PKEY_CTX_get0_pkey(ctx);
        *keylen = 32;
        if (key == NULL) return 1;

        return make_cp_exchange_key(gost_get0_priv_key(mykey), pubk, key);
    }

/* 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;
    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);
    gost_ctx cctx;
    int key_is_ephemeral=1;
    EVP_PKEY *mykey = EVP_PKEY_CTX_get0_peerkey(ctx);

    /* Do not use vizir cipher parameters with cryptopro */
    if (!get_gost_engine_param(GOST_PARAM_CRYPT_PARAMS) && param ==  gost_cipher_list)
        {
        param= gost_cipher_list+1;
        }   

    if (mykey) 
        {
        /* If key already set, it is not ephemeral */
        key_is_ephemeral=0;
        if (!gost_get0_priv_key(mykey)) 
            {
            GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
            GOST_R_NO_PRIVATE_PART_OF_NON_EPHEMERAL_KEYPAIR);
            goto err;
            }   
        } 
    else 
        {
        /* Otherwise generate ephemeral key */
        key_is_ephemeral = 1;
        if (out) 
            {
            mykey = EVP_PKEY_new();
            EVP_PKEY_assign(mykey, EVP_PKEY_base_id(pubk),DSA_new());
            EVP_PKEY_copy_parameters(mykey,pubk);
            if (!gost_sign_keygen(EVP_PKEY_get0(mykey))) 
                {
                goto err;
                }   
            }
        }   
    if (out)
        make_cp_exchange_key(gost_get0_priv_key(mykey),pubk,shared_key);
    if (data->shared_ukm) 
        {
        memcpy(ukm,data->shared_ukm,8);
        }
    else if (out) 
        {   
        if (RAND_bytes(ukm,8)<=0)
            {
            GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
                    GOST_R_RANDOM_GENERATOR_FAILURE);
            goto err;
            }   
        }
        
    if (out) {
        gost_init(&cctx,param->sblock);
        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 (key_is_ephemeral) { 
    if (!X509_PUBKEY_set(&gkt->key_agreement_info->ephem_key,out?mykey:pubk))
        {
        GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,GOST_R_CANNOT_PACK_EPHEMERAL_KEY);
        goto err;
        }
        if (out) EVP_PKEY_free(mykey);
    }   
    ASN1_OBJECT_free(gkt->key_agreement_info->cipher);
    gkt->key_agreement_info->cipher = OBJ_nid2obj(param->nid);
    *outlen = i2d_GOST_KEY_TRANSPORT(gkt,out?&out:NULL);
    if (*outlen <= 0)
        {
        GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,GOST_R_ERROR_PACKING_KEY_TRANSPORT_INFO);
        goto err;
        }
    if (!key_is_ephemeral)
        {
        /* Set control "public key from client certificate used" */
        if (EVP_PKEY_CTX_ctrl(ctx, -1, -1, EVP_PKEY_CTRL_PEER_KEY, 3, NULL) <= 0)
            {
            GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
                GOST_R_CTRL_CALL_FAILED);
            goto err;
            }
        }
    GOST_KEY_TRANSPORT_free(gkt);
    return 1;   
    memerr:
        if (key_is_ephemeral) {
            EVP_PKEY_free(mykey);
        }   
    GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
        GOST_R_MALLOC_FAILURE);
    err:        
    GOST_KEY_TRANSPORT_free(gkt);
    return -1;
    }

    
/* EVP_PLEY_METHOD callback decrypt for
 * GOST R 34.10-94 cryptopro modification
 */
int pkey_GOST94cp_decrypt(EVP_PKEY_CTX *ctx, unsigned char *key, size_t *key_len,const unsigned char *in, size_t in_len) {
    const unsigned char *p = in;
    GOST_KEY_TRANSPORT *gkt = NULL;
    unsigned char wrappedKey[44];
    unsigned char sharedKey[32];
    gost_ctx cctx;
    const struct gost_cipher_info *param=NULL;
    EVP_PKEY *eph_key=NULL, *peerkey=NULL;
    EVP_PKEY *priv= EVP_PKEY_CTX_get0_pkey(ctx); 
    
    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_GOST94CP_DECRYPT,GOST_R_ERROR_PARSING_KEY_TRANSPORT_INFO);
        return 0;
        }   
    eph_key = X509_PUBKEY_get(gkt->key_agreement_info->ephem_key);
    if (eph_key)
        {
        if (EVP_PKEY_derive_set_peer(ctx, eph_key) <= 0)
            {
            GOSTerr(GOST_F_PKEY_GOST94CP_DECRYPT,
                GOST_R_INCOMPATIBLE_PEER_KEY);
            goto err;
            }
        }
    else
        {
        /* Set control "public key from client certificate used" */
        if (EVP_PKEY_CTX_ctrl(ctx, -1, -1, EVP_PKEY_CTRL_PEER_KEY, 3, NULL) <= 0)
            {
            GOSTerr(GOST_F_PKEY_GOST94CP_DECRYPT,
                GOST_R_CTRL_CALL_FAILED);
            goto err;
            }
        }
    peerkey = EVP_PKEY_CTX_get0_peerkey(ctx);
    if (!peerkey)
        {
        GOSTerr(GOST_F_PKEY_GOST94CP_DECRYPT,
            GOST_R_NO_PEER_KEY);
        goto err;
        }

    param = get_encryption_params(gkt->key_agreement_info->cipher);
    if(!param){
        goto err;
    }
    
    gost_init(&cctx,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);  
    make_cp_exchange_key(gost_get0_priv_key(priv),peerkey,sharedKey);
    if (!keyUnwrapCryptoPro(&cctx,sharedKey,wrappedKey,key))
        {
        GOSTerr(GOST_F_PKEY_GOST94CP_DECRYPT,
            GOST_R_ERROR_COMPUTING_SHARED_KEY);
        goto err;
        }   
                
    EVP_PKEY_free(eph_key);
    GOST_KEY_TRANSPORT_free(gkt);
    return 1;
err:
    EVP_PKEY_free(eph_key);
    GOST_KEY_TRANSPORT_free(gkt);
    return -1;
    }