text: /**********************************************************************
   *                             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;
      int tmp_outlen;
      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();
              if (!mykey)
                  goto memerr;
              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);
      tmp_outlen = i2d_GOST_KEY_TRANSPORT(gkt, out ? &out : NULL);
      if (tmp_outlen <= 0) {
          GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
                  GOST_R_ERROR_PACKING_KEY_TRANSPORT_INFO);
          goto err;
      }
      *outlen = tmp_outlen;
      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;
  }
  