crypto_ecc.c

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/*
     This file is part of GNUnet.
     Copyright (C) 2012, 2013, 2015 GNUnet e.V.

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     or (at your option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */

#include "platform.h"
#include <gcrypt.h>
#include "gnunet_crypto_lib.h"
#include "gnunet_strings_lib.h"
#include "benchmark.h"

#define EXTRA_CHECKS 0

#define CURVE "Ed25519"

#define LOG(kind, ...) GNUNET_log_from(kind, "util-crypto-ecc", __VA_ARGS__)

#define LOG_STRERROR(kind, syscall) \
  GNUNET_log_from_strerror(kind, "util-crypto-ecc", syscall)

#define LOG_STRERROR_FILE(kind, syscall, filename) \
  GNUNET_log_from_strerror_file(kind, "util-crypto-ecc", syscall, filename)

#define LOG_GCRY(level, cmd, rc)                      \
  do                                                  \
    {                                                   \
      LOG(level,                                       \
          _("`%s' failed at %s:%d with error: %s\n"), \
          cmd,                                         \
          __FILE__,                                    \
          __LINE__,                                    \
          gcry_strerror(rc));                         \
    } while (0)


static int
key_from_sexp(gcry_mpi_t *array,
              gcry_sexp_t sexp,
              const char *topname,
              const char *elems)
{
  gcry_sexp_t list;
  gcry_sexp_t l2;
  const char *s;
  unsigned int i;
  unsigned int idx;

  list = gcry_sexp_find_token(sexp, topname, 0);
  if (!list)
    return 1;
  l2 = gcry_sexp_cadr(list);
  gcry_sexp_release(list);
  list = l2;
  if (!list)
    return 2;

  idx = 0;
  for (s = elems; *s; s++, idx++)
    {
      l2 = gcry_sexp_find_token(list, s, 1);
      if (!l2)
        {
          for (i = 0; i < idx; i++)
            {
              gcry_free(array[i]);
              array[i] = NULL;
            }
          gcry_sexp_release(list);
          return 3; /* required parameter not found */
        }
      array[idx] = gcry_sexp_nth_mpi(l2, 1, GCRYMPI_FMT_USG);
      gcry_sexp_release(l2);
      if (!array[idx])
        {
          for (i = 0; i < idx; i++)
            {
              gcry_free(array[i]);
              array[i] = NULL;
            }
          gcry_sexp_release(list);
          return 4; /* required parameter is invalid */
        }
    }
  gcry_sexp_release(list);
  return 0;
}


static gcry_sexp_t
decode_private_ecdsa_key(const struct GNUNET_CRYPTO_EcdsaPrivateKey *priv)
{
  gcry_sexp_t result;
  int rc;

  rc = gcry_sexp_build(&result,
                       NULL,
                       "(private-key(ecc(curve \"" CURVE "\")"
                       "(d %b)))",
                       (int)sizeof(priv->d),
                       priv->d);
  if (0 != rc)
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      GNUNET_assert(0);
    }
#if EXTRA_CHECKS
  if (0 != (rc = gcry_pk_testkey(result)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_pk_testkey", rc);
      GNUNET_assert(0);
    }
#endif
  return result;
}


static gcry_sexp_t
decode_private_eddsa_key(const struct GNUNET_CRYPTO_EddsaPrivateKey *priv)
{
  gcry_sexp_t result;
  int rc;

  rc = gcry_sexp_build(&result,
                       NULL,
                       "(private-key(ecc(curve \"" CURVE "\")"
                       "(flags eddsa)(d %b)))",
                       (int)sizeof(priv->d),
                       priv->d);
  if (0 != rc)
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      GNUNET_assert(0);
    }
#if EXTRA_CHECKS
  if (0 != (rc = gcry_pk_testkey(result)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_pk_testkey", rc);
      GNUNET_assert(0);
    }
#endif
  return result;
}


static gcry_sexp_t
decode_private_ecdhe_key(const struct GNUNET_CRYPTO_EcdhePrivateKey *priv)
{
  gcry_sexp_t result;
  int rc;

  rc = gcry_sexp_build(&result,
                       NULL,
                       "(private-key(ecc(curve \"" CURVE "\")"
                       "(d %b)))",
                       (int)sizeof(priv->d),
                       priv->d);
  if (0 != rc)
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      GNUNET_assert(0);
    }
#if EXTRA_CHECKS
  if (0 != (rc = gcry_pk_testkey(result)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_pk_testkey", rc);
      GNUNET_assert(0);
    }
#endif
  return result;
}


void
GNUNET_CRYPTO_ecdsa_key_get_public(
  const struct GNUNET_CRYPTO_EcdsaPrivateKey *priv,
  struct GNUNET_CRYPTO_EcdsaPublicKey *pub)
{
  gcry_sexp_t sexp;
  gcry_ctx_t ctx;
  gcry_mpi_t q;

  BENCHMARK_START(ecdsa_key_get_public);

  sexp = decode_private_ecdsa_key(priv);
  GNUNET_assert(NULL != sexp);
  GNUNET_assert(0 == gcry_mpi_ec_new(&ctx, sexp, NULL));
  gcry_sexp_release(sexp);
  q = gcry_mpi_ec_get_mpi("q@eddsa", ctx, 0);
  GNUNET_assert(NULL != q);
  GNUNET_CRYPTO_mpi_print_unsigned(pub->q_y, sizeof(pub->q_y), q);
  gcry_mpi_release(q);
  gcry_ctx_release(ctx);

  BENCHMARK_END(ecdsa_key_get_public);
}


void
GNUNET_CRYPTO_eddsa_key_get_public(
  const struct GNUNET_CRYPTO_EddsaPrivateKey *priv,
  struct GNUNET_CRYPTO_EddsaPublicKey *pub)
{
  gcry_sexp_t sexp;
  gcry_ctx_t ctx;
  gcry_mpi_t q;

  BENCHMARK_START(eddsa_key_get_public);

  sexp = decode_private_eddsa_key(priv);
  GNUNET_assert(NULL != sexp);
  GNUNET_assert(0 == gcry_mpi_ec_new(&ctx, sexp, NULL));
  gcry_sexp_release(sexp);
  q = gcry_mpi_ec_get_mpi("q@eddsa", ctx, 0);
  GNUNET_assert(q);
  GNUNET_CRYPTO_mpi_print_unsigned(pub->q_y, sizeof(pub->q_y), q);
  gcry_mpi_release(q);
  gcry_ctx_release(ctx);

  BENCHMARK_END(eddsa_key_get_public);
}


void
GNUNET_CRYPTO_ecdhe_key_get_public(
  const struct GNUNET_CRYPTO_EcdhePrivateKey *priv,
  struct GNUNET_CRYPTO_EcdhePublicKey *pub)
{
  gcry_sexp_t sexp;
  gcry_ctx_t ctx;
  gcry_mpi_t q;

  BENCHMARK_START(ecdhe_key_get_public);

  sexp = decode_private_ecdhe_key(priv);
  GNUNET_assert(NULL != sexp);
  GNUNET_assert(0 == gcry_mpi_ec_new(&ctx, sexp, NULL));
  gcry_sexp_release(sexp);
  q = gcry_mpi_ec_get_mpi("q@eddsa", ctx, 0);
  GNUNET_assert(q);
  GNUNET_CRYPTO_mpi_print_unsigned(pub->q_y, sizeof(pub->q_y), q);
  gcry_mpi_release(q);
  gcry_ctx_release(ctx);

  BENCHMARK_END(ecdhe_key_get_public);
}


char *
GNUNET_CRYPTO_ecdsa_public_key_to_string(
  const struct GNUNET_CRYPTO_EcdsaPublicKey *pub)
{
  char *pubkeybuf;
  size_t keylen = (sizeof(struct GNUNET_CRYPTO_EcdsaPublicKey)) * 8;
  char *end;

  if (keylen % 5 > 0)
    keylen += 5 - keylen % 5;
  keylen /= 5;
  pubkeybuf = GNUNET_malloc(keylen + 1);
  end =
    GNUNET_STRINGS_data_to_string((unsigned char *)pub,
                                  sizeof(struct GNUNET_CRYPTO_EcdsaPublicKey),
                                  pubkeybuf,
                                  keylen);
  if (NULL == end)
    {
      GNUNET_free(pubkeybuf);
      return NULL;
    }
  *end = '\0';
  return pubkeybuf;
}


char *
GNUNET_CRYPTO_eddsa_public_key_to_string(
  const struct GNUNET_CRYPTO_EddsaPublicKey *pub)
{
  char *pubkeybuf;
  size_t keylen = (sizeof(struct GNUNET_CRYPTO_EddsaPublicKey)) * 8;
  char *end;

  if (keylen % 5 > 0)
    keylen += 5 - keylen % 5;
  keylen /= 5;
  pubkeybuf = GNUNET_malloc(keylen + 1);
  end =
    GNUNET_STRINGS_data_to_string((unsigned char *)pub,
                                  sizeof(struct GNUNET_CRYPTO_EddsaPublicKey),
                                  pubkeybuf,
                                  keylen);
  if (NULL == end)
    {
      GNUNET_free(pubkeybuf);
      return NULL;
    }
  *end = '\0';
  return pubkeybuf;
}


char *
GNUNET_CRYPTO_eddsa_private_key_to_string(
  const struct GNUNET_CRYPTO_EddsaPrivateKey *priv)
{
  char *privkeybuf;
  size_t keylen = (sizeof(struct GNUNET_CRYPTO_EddsaPrivateKey)) * 8;
  char *end;

  if (keylen % 5 > 0)
    keylen += 5 - keylen % 5;
  keylen /= 5;
  privkeybuf = GNUNET_malloc(keylen + 1);
  end = GNUNET_STRINGS_data_to_string((unsigned char *)priv,
                                      sizeof(
                                        struct GNUNET_CRYPTO_EddsaPrivateKey),
                                      privkeybuf,
                                      keylen);
  if (NULL == end)
    {
      GNUNET_free(privkeybuf);
      return NULL;
    }
  *end = '\0';
  return privkeybuf;
}


char *
GNUNET_CRYPTO_ecdsa_private_key_to_string(
  const struct GNUNET_CRYPTO_EcdsaPrivateKey *priv)
{
  char *privkeybuf;
  size_t keylen = (sizeof(struct GNUNET_CRYPTO_EcdsaPrivateKey)) * 8;
  char *end;

  if (keylen % 5 > 0)
    keylen += 5 - keylen % 5;
  keylen /= 5;
  privkeybuf = GNUNET_malloc(keylen + 1);
  end = GNUNET_STRINGS_data_to_string((unsigned char *)priv,
                                      sizeof(
                                        struct GNUNET_CRYPTO_EcdsaPrivateKey),
                                      privkeybuf,
                                      keylen);
  if (NULL == end)
    {
      GNUNET_free(privkeybuf);
      return NULL;
    }
  *end = '\0';
  return privkeybuf;
}


int
GNUNET_CRYPTO_ecdsa_public_key_from_string(
  const char *enc,
  size_t enclen,
  struct GNUNET_CRYPTO_EcdsaPublicKey *pub)
{
  size_t keylen = (sizeof(struct GNUNET_CRYPTO_EcdsaPublicKey)) * 8;

  if (keylen % 5 > 0)
    keylen += 5 - keylen % 5;
  keylen /= 5;
  if (enclen != keylen)
    return GNUNET_SYSERR;

  if (GNUNET_OK !=
      GNUNET_STRINGS_string_to_data(enc,
                                    enclen,
                                    pub,
                                    sizeof(
                                      struct GNUNET_CRYPTO_EcdsaPublicKey)))
    return GNUNET_SYSERR;
  return GNUNET_OK;
}


int
GNUNET_CRYPTO_eddsa_public_key_from_string(
  const char *enc,
  size_t enclen,
  struct GNUNET_CRYPTO_EddsaPublicKey *pub)
{
  size_t keylen = (sizeof(struct GNUNET_CRYPTO_EddsaPublicKey)) * 8;

  if (keylen % 5 > 0)
    keylen += 5 - keylen % 5;
  keylen /= 5;
  if (enclen != keylen)
    return GNUNET_SYSERR;

  if (GNUNET_OK !=
      GNUNET_STRINGS_string_to_data(enc,
                                    enclen,
                                    pub,
                                    sizeof(
                                      struct GNUNET_CRYPTO_EddsaPublicKey)))
    return GNUNET_SYSERR;
  return GNUNET_OK;
}


int
GNUNET_CRYPTO_eddsa_private_key_from_string(
  const char *enc,
  size_t enclen,
  struct GNUNET_CRYPTO_EddsaPrivateKey *priv)
{
  size_t keylen = (sizeof(struct GNUNET_CRYPTO_EddsaPrivateKey)) * 8;

  if (keylen % 5 > 0)
    keylen += 5 - keylen % 5;
  keylen /= 5;
  if (enclen != keylen)
    return GNUNET_SYSERR;

  if (GNUNET_OK !=
      GNUNET_STRINGS_string_to_data(enc,
                                    enclen,
                                    priv,
                                    sizeof(
                                      struct GNUNET_CRYPTO_EddsaPrivateKey)))
    return GNUNET_SYSERR;
#if CRYPTO_BUG
  if (GNUNET_OK != check_eddsa_key(priv))
    {
      GNUNET_break(0);
      return GNUNET_OK;
    }
#endif
  return GNUNET_OK;
}


void
GNUNET_CRYPTO_ecdhe_key_clear(struct GNUNET_CRYPTO_EcdhePrivateKey *pk)
{
  memset(pk, 0, sizeof(struct GNUNET_CRYPTO_EcdhePrivateKey));
}


void
GNUNET_CRYPTO_ecdsa_key_clear(struct GNUNET_CRYPTO_EcdsaPrivateKey *pk)
{
  memset(pk, 0, sizeof(struct GNUNET_CRYPTO_EcdsaPrivateKey));
}


void
GNUNET_CRYPTO_eddsa_key_clear(struct GNUNET_CRYPTO_EddsaPrivateKey *pk)
{
  memset(pk, 0, sizeof(struct GNUNET_CRYPTO_EddsaPrivateKey));
}


struct GNUNET_CRYPTO_EcdhePrivateKey *
GNUNET_CRYPTO_ecdhe_key_create()
{
  struct GNUNET_CRYPTO_EcdhePrivateKey *priv;

  priv = GNUNET_new(struct GNUNET_CRYPTO_EcdhePrivateKey);
  if (GNUNET_OK != GNUNET_CRYPTO_ecdhe_key_create2(priv))
    {
      GNUNET_free(priv);
      return NULL;
    }
  return priv;
}


int
GNUNET_CRYPTO_ecdhe_key_create2(struct GNUNET_CRYPTO_EcdhePrivateKey *pk)
{
  gcry_sexp_t priv_sexp;
  gcry_sexp_t s_keyparam;
  gcry_mpi_t d;
  int rc;

  BENCHMARK_START(ecdhe_key_create);

  /* NOTE: For libgcrypt >= 1.7, we do not need the 'eddsa' flag here,
     but should also be harmless. For libgcrypt < 1.7, using 'eddsa'
     disables an expensive key testing routine. We do not want to run
     the expensive check for ECDHE, as we generate TONS of keys to
     use for a very short time. */
  if (0 != (rc = gcry_sexp_build(&s_keyparam,
                                 NULL,
                                 "(genkey(ecc(curve \"" CURVE "\")"
                                 "(flags eddsa no-keytest)))")))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      return GNUNET_SYSERR;
    }
  if (0 != (rc = gcry_pk_genkey(&priv_sexp, s_keyparam)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_pk_genkey", rc);
      gcry_sexp_release(s_keyparam);
      return GNUNET_SYSERR;
    }
  gcry_sexp_release(s_keyparam);
#if EXTRA_CHECKS
  if (0 != (rc = gcry_pk_testkey(priv_sexp)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_pk_testkey", rc);
      gcry_sexp_release(priv_sexp);
      return GNUNET_SYSERR;
    }
#endif
  if (0 != (rc = key_from_sexp(&d, priv_sexp, "private-key", "d")))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "key_from_sexp", rc);
      gcry_sexp_release(priv_sexp);
      return GNUNET_SYSERR;
    }
  gcry_sexp_release(priv_sexp);
  GNUNET_CRYPTO_mpi_print_unsigned(pk->d, sizeof(pk->d), d);
  gcry_mpi_release(d);

  BENCHMARK_END(ecdhe_key_create);

  return GNUNET_OK;
}


struct GNUNET_CRYPTO_EcdsaPrivateKey *
GNUNET_CRYPTO_ecdsa_key_create()
{
  struct GNUNET_CRYPTO_EcdsaPrivateKey *priv;
  gcry_sexp_t priv_sexp;
  gcry_sexp_t s_keyparam;
  gcry_mpi_t d;
  int rc;

  BENCHMARK_START(ecdsa_key_create);

  if (0 != (rc = gcry_sexp_build(&s_keyparam,
                                 NULL,
                                 "(genkey(ecc(curve \"" CURVE "\")"
                                 "(flags)))")))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      return NULL;
    }
  if (0 != (rc = gcry_pk_genkey(&priv_sexp, s_keyparam)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_pk_genkey", rc);
      gcry_sexp_release(s_keyparam);
      return NULL;
    }
  gcry_sexp_release(s_keyparam);
#if EXTRA_CHECKS
  if (0 != (rc = gcry_pk_testkey(priv_sexp)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_pk_testkey", rc);
      gcry_sexp_release(priv_sexp);
      return NULL;
    }
#endif
  if (0 != (rc = key_from_sexp(&d, priv_sexp, "private-key", "d")))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "key_from_sexp", rc);
      gcry_sexp_release(priv_sexp);
      return NULL;
    }
  gcry_sexp_release(priv_sexp);
  priv = GNUNET_new(struct GNUNET_CRYPTO_EcdsaPrivateKey);
  GNUNET_CRYPTO_mpi_print_unsigned(priv->d, sizeof(priv->d), d);
  gcry_mpi_release(d);

  BENCHMARK_END(ecdsa_key_create);

  return priv;
}

struct GNUNET_CRYPTO_EddsaPrivateKey *
GNUNET_CRYPTO_eddsa_key_create()
{
  struct GNUNET_CRYPTO_EddsaPrivateKey *priv;
  gcry_sexp_t priv_sexp;
  gcry_sexp_t s_keyparam;
  gcry_mpi_t d;
  int rc;

  BENCHMARK_START(eddsa_key_create);

#if CRYPTO_BUG
again:
#endif
  if (0 != (rc = gcry_sexp_build(&s_keyparam,
                                 NULL,
                                 "(genkey(ecc(curve \"" CURVE "\")"
                                 "(flags eddsa)))")))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      return NULL;
    }
  if (0 != (rc = gcry_pk_genkey(&priv_sexp, s_keyparam)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_pk_genkey", rc);
      gcry_sexp_release(s_keyparam);
      return NULL;
    }
  gcry_sexp_release(s_keyparam);
#if EXTRA_CHECKS
  if (0 != (rc = gcry_pk_testkey(priv_sexp)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_pk_testkey", rc);
      gcry_sexp_release(priv_sexp);
      return NULL;
    }
#endif
  if (0 != (rc = key_from_sexp(&d, priv_sexp, "private-key", "d")))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "key_from_sexp", rc);
      gcry_sexp_release(priv_sexp);
      return NULL;
    }
  gcry_sexp_release(priv_sexp);
  priv = GNUNET_new(struct GNUNET_CRYPTO_EddsaPrivateKey);
  GNUNET_CRYPTO_mpi_print_unsigned(priv->d, sizeof(priv->d), d);
  gcry_mpi_release(d);

#if CRYPTO_BUG
  if (GNUNET_OK != check_eddsa_key(priv))
    {
      GNUNET_break(0);
      GNUNET_free(priv);
      goto again;
    }
#endif

  BENCHMARK_END(eddsa_key_create);

  return priv;
}


const struct GNUNET_CRYPTO_EcdsaPrivateKey *
GNUNET_CRYPTO_ecdsa_key_get_anonymous()
{
  static struct GNUNET_CRYPTO_EcdsaPrivateKey anonymous;
  static int once;

  if (once)
    return &anonymous;
  GNUNET_CRYPTO_mpi_print_unsigned(anonymous.d,
                                   sizeof(anonymous.d),
                                   GCRYMPI_CONST_ONE);
  once = 1;
  return &anonymous;
}


static gcry_sexp_t
data_to_eddsa_value(const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose)
{
  gcry_sexp_t data;
  int rc;

/* SEE #5398 */
#if 1
  struct GNUNET_HashCode hc;

  GNUNET_CRYPTO_hash(purpose, ntohl(purpose->size), &hc);
  if (0 != (rc = gcry_sexp_build(&data,
                                 NULL,
                                 "(data(flags eddsa)(hash-algo %s)(value %b))",
                                 "sha512",
                                 (int)sizeof(hc),
                                 &hc)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      return NULL;
    }
#else
  GNUNET_CRYPTO_hash(purpose, ntohl(purpose->size), &hc);
  if (0 != (rc = gcry_sexp_build(&data,
                                 NULL,
                                 "(data(flags eddsa)(hash-algo %s)(value %b))",
                                 "sha512",
                                 ntohl(purpose->size),
                                 purpose)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      return NULL;
    }
#endif
  return data;
}


static gcry_sexp_t
data_to_ecdsa_value(const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose)
{
  gcry_sexp_t data;
  int rc;

/* See #5398 */
#if 1
  struct GNUNET_HashCode hc;

  GNUNET_CRYPTO_hash(purpose, ntohl(purpose->size), &hc);
  if (0 != (rc = gcry_sexp_build(&data,
                                 NULL,
                                 "(data(flags rfc6979)(hash %s %b))",
                                 "sha512",
                                 (int)sizeof(hc),
                                 &hc)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      return NULL;
    }
#else
  if (0 != (rc = gcry_sexp_build(&data,
                                 NULL,
                                 "(data(flags rfc6979)(hash %s %b))",
                                 "sha512",
                                 ntohl(purpose->size),
                                 purpose)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      return NULL;
    }
#endif
  return data;
}


int
GNUNET_CRYPTO_ecdsa_sign(
  const struct GNUNET_CRYPTO_EcdsaPrivateKey *priv,
  const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
  struct GNUNET_CRYPTO_EcdsaSignature *sig)
{
  gcry_sexp_t priv_sexp;
  gcry_sexp_t sig_sexp;
  gcry_sexp_t data;
  int rc;
  gcry_mpi_t rs[2];

  BENCHMARK_START(ecdsa_sign);

  priv_sexp = decode_private_ecdsa_key(priv);
  data = data_to_ecdsa_value(purpose);
  if (0 != (rc = gcry_pk_sign(&sig_sexp, data, priv_sexp)))
    {
      LOG(GNUNET_ERROR_TYPE_WARNING,
          _("ECC signing failed at %s:%d: %s\n"),
          __FILE__,
          __LINE__,
          gcry_strerror(rc));
      gcry_sexp_release(data);
      gcry_sexp_release(priv_sexp);
      return GNUNET_SYSERR;
    }
  gcry_sexp_release(priv_sexp);
  gcry_sexp_release(data);

  /* extract 'r' and 's' values from sexpression 'sig_sexp' and store in
     'signature' */
  if (0 != (rc = key_from_sexp(rs, sig_sexp, "sig-val", "rs")))
    {
      GNUNET_break(0);
      gcry_sexp_release(sig_sexp);
      return GNUNET_SYSERR;
    }
  gcry_sexp_release(sig_sexp);
  GNUNET_CRYPTO_mpi_print_unsigned(sig->r, sizeof(sig->r), rs[0]);
  GNUNET_CRYPTO_mpi_print_unsigned(sig->s, sizeof(sig->s), rs[1]);
  gcry_mpi_release(rs[0]);
  gcry_mpi_release(rs[1]);

  BENCHMARK_END(ecdsa_sign);

  return GNUNET_OK;
}


int
GNUNET_CRYPTO_eddsa_sign(
  const struct GNUNET_CRYPTO_EddsaPrivateKey *priv,
  const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose,
  struct GNUNET_CRYPTO_EddsaSignature *sig)
{
  gcry_sexp_t priv_sexp;
  gcry_sexp_t sig_sexp;
  gcry_sexp_t data;
  int rc;
  gcry_mpi_t rs[2];

  BENCHMARK_START(eddsa_sign);

  priv_sexp = decode_private_eddsa_key(priv);
  data = data_to_eddsa_value(purpose);
  if (0 != (rc = gcry_pk_sign(&sig_sexp, data, priv_sexp)))
    {
      LOG(GNUNET_ERROR_TYPE_WARNING,
          _("EdDSA signing failed at %s:%d: %s\n"),
          __FILE__,
          __LINE__,
          gcry_strerror(rc));
      gcry_sexp_release(data);
      gcry_sexp_release(priv_sexp);
      return GNUNET_SYSERR;
    }
  gcry_sexp_release(priv_sexp);
  gcry_sexp_release(data);

  /* extract 'r' and 's' values from sexpression 'sig_sexp' and store in
     'signature' */
  if (0 != (rc = key_from_sexp(rs, sig_sexp, "sig-val", "rs")))
    {
      GNUNET_break(0);
      gcry_sexp_release(sig_sexp);
      return GNUNET_SYSERR;
    }
  gcry_sexp_release(sig_sexp);
  GNUNET_CRYPTO_mpi_print_unsigned(sig->r, sizeof(sig->r), rs[0]);
  GNUNET_CRYPTO_mpi_print_unsigned(sig->s, sizeof(sig->s), rs[1]);
  gcry_mpi_release(rs[0]);
  gcry_mpi_release(rs[1]);

  BENCHMARK_END(eddsa_sign);

  return GNUNET_OK;
}


int
GNUNET_CRYPTO_ecdsa_verify(
  uint32_t purpose,
  const struct GNUNET_CRYPTO_EccSignaturePurpose *validate,
  const struct GNUNET_CRYPTO_EcdsaSignature *sig,
  const struct GNUNET_CRYPTO_EcdsaPublicKey *pub)
{
  gcry_sexp_t data;
  gcry_sexp_t sig_sexpr;
  gcry_sexp_t pub_sexpr;
  int rc;

  BENCHMARK_START(ecdsa_verify);

  if (purpose != ntohl(validate->purpose))
    return GNUNET_SYSERR; /* purpose mismatch */

  /* build s-expression for signature */
  if (0 != (rc = gcry_sexp_build(&sig_sexpr,
                                 NULL,
                                 "(sig-val(ecdsa(r %b)(s %b)))",
                                 (int)sizeof(sig->r),
                                 sig->r,
                                 (int)sizeof(sig->s),
                                 sig->s)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      return GNUNET_SYSERR;
    }
  data = data_to_ecdsa_value(validate);
  if (0 != (rc = gcry_sexp_build(&pub_sexpr,
                                 NULL,
                                 "(public-key(ecc(curve " CURVE ")(q %b)))",
                                 (int)sizeof(pub->q_y),
                                 pub->q_y)))
    {
      gcry_sexp_release(data);
      gcry_sexp_release(sig_sexpr);
      return GNUNET_SYSERR;
    }
  rc = gcry_pk_verify(sig_sexpr, data, pub_sexpr);
  gcry_sexp_release(pub_sexpr);
  gcry_sexp_release(data);
  gcry_sexp_release(sig_sexpr);
  if (0 != rc)
    {
      LOG(GNUNET_ERROR_TYPE_INFO,
          _("ECDSA signature verification failed at %s:%d: %s\n"),
          __FILE__,
          __LINE__,
          gcry_strerror(rc));
      BENCHMARK_END(ecdsa_verify);
      return GNUNET_SYSERR;
    }
  BENCHMARK_END(ecdsa_verify);
  return GNUNET_OK;
}


int
GNUNET_CRYPTO_eddsa_verify(
  uint32_t purpose,
  const struct GNUNET_CRYPTO_EccSignaturePurpose *validate,
  const struct GNUNET_CRYPTO_EddsaSignature *sig,
  const struct GNUNET_CRYPTO_EddsaPublicKey *pub)
{
  gcry_sexp_t data;
  gcry_sexp_t sig_sexpr;
  gcry_sexp_t pub_sexpr;
  int rc;

  BENCHMARK_START(eddsa_verify);

  if (purpose != ntohl(validate->purpose))
    return GNUNET_SYSERR; /* purpose mismatch */

  /* build s-expression for signature */
  if (0 != (rc = gcry_sexp_build(&sig_sexpr,
                                 NULL,
                                 "(sig-val(eddsa(r %b)(s %b)))",
                                 (int)sizeof(sig->r),
                                 sig->r,
                                 (int)sizeof(sig->s),
                                 sig->s)))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "gcry_sexp_build", rc);
      return GNUNET_SYSERR;
    }
  data = data_to_eddsa_value(validate);
  if (0 != (rc = gcry_sexp_build(&pub_sexpr,
                                 NULL,
                                 "(public-key(ecc(curve " CURVE
                                 ")(flags eddsa)(q %b)))",
                                 (int)sizeof(pub->q_y),
                                 pub->q_y)))
    {
      gcry_sexp_release(data);
      gcry_sexp_release(sig_sexpr);
      return GNUNET_SYSERR;
    }
  rc = gcry_pk_verify(sig_sexpr, data, pub_sexpr);
  gcry_sexp_release(pub_sexpr);
  gcry_sexp_release(data);
  gcry_sexp_release(sig_sexpr);
  if (0 != rc)
    {
      LOG(GNUNET_ERROR_TYPE_INFO,
          _("EdDSA signature verification of type %u failed at %s:%d: %s\n"),
          (unsigned int)purpose,
          __FILE__,
          __LINE__,
          gcry_strerror(rc));
      BENCHMARK_END(eddsa_verify);
      return GNUNET_SYSERR;
    }
  BENCHMARK_END(eddsa_verify);
  return GNUNET_OK;
}


int
GNUNET_CRYPTO_ecc_ecdh(const struct GNUNET_CRYPTO_EcdhePrivateKey *priv,
                       const struct GNUNET_CRYPTO_EcdhePublicKey *pub,
                       struct GNUNET_HashCode *key_material)
{
  gcry_mpi_point_t result;
  gcry_mpi_point_t q;
  gcry_mpi_t d;
  gcry_ctx_t ctx;
  gcry_sexp_t pub_sexpr;
  gcry_mpi_t result_x;
  unsigned char xbuf[256 / 8];
  size_t rsize;

  BENCHMARK_START(ecc_ecdh);

  /* first, extract the q = dP value from the public key */
  if (0 != gcry_sexp_build(&pub_sexpr,
                           NULL,
                           "(public-key(ecc(curve " CURVE ")(q %b)))",
                           (int)sizeof(pub->q_y),
                           pub->q_y))
    return GNUNET_SYSERR;
  GNUNET_assert(0 == gcry_mpi_ec_new(&ctx, pub_sexpr, NULL));
  gcry_sexp_release(pub_sexpr);
  q = gcry_mpi_ec_get_point("q", ctx, 0);

  /* second, extract the d value from our private key */
  GNUNET_CRYPTO_mpi_scan_unsigned(&d, priv->d, sizeof(priv->d));

  /* then call the 'multiply' function, to compute the product */
  result = gcry_mpi_point_new(0);
  gcry_mpi_ec_mul(result, d, q, ctx);
  gcry_mpi_point_release(q);
  gcry_mpi_release(d);

  /* finally, convert point to string for hashing */
  result_x = gcry_mpi_new(256);
  if (gcry_mpi_ec_get_affine(result_x, NULL, result, ctx))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "get_affine failed", 0);
      gcry_mpi_point_release(result);
      gcry_ctx_release(ctx);
      return GNUNET_SYSERR;
    }
  gcry_mpi_point_release(result);
  gcry_ctx_release(ctx);

  rsize = sizeof(xbuf);
  GNUNET_assert(!gcry_mpi_get_flag(result_x, GCRYMPI_FLAG_OPAQUE));
  /* result_x can be negative here, so we do not use 'GNUNET_CRYPTO_mpi_print_unsigned'
     as that does not include the sign bit; x should be a 255-bit
     value, so with the sign it should fit snugly into the 256-bit
     xbuf */
  GNUNET_assert(
    0 == gcry_mpi_print(GCRYMPI_FMT_STD, xbuf, rsize, &rsize, result_x));
  GNUNET_CRYPTO_hash(xbuf, rsize, key_material);
  gcry_mpi_release(result_x);
  BENCHMARK_END(ecc_ecdh);
  return GNUNET_OK;
}


static gcry_mpi_t
derive_h(const struct GNUNET_CRYPTO_EcdsaPublicKey *pub,
         const char *label,
         const char *context)
{
  gcry_mpi_t h;
  struct GNUNET_HashCode hc;
  static const char *const salt = "key-derivation";

  GNUNET_CRYPTO_kdf(&hc,
                    sizeof(hc),
                    salt,
                    strlen(salt),
                    pub,
                    sizeof(*pub),
                    label,
                    strlen(label),
                    context,
                    strlen(context),
                    NULL,
                    0);
  GNUNET_CRYPTO_mpi_scan_unsigned(&h, (unsigned char *)&hc, sizeof(hc));
  return h;
}


struct GNUNET_CRYPTO_EcdsaPrivateKey *
GNUNET_CRYPTO_ecdsa_private_key_derive(
  const struct GNUNET_CRYPTO_EcdsaPrivateKey *priv,
  const char *label,
  const char *context)
{
  struct GNUNET_CRYPTO_EcdsaPublicKey pub;
  struct GNUNET_CRYPTO_EcdsaPrivateKey *ret;
  gcry_mpi_t h;
  gcry_mpi_t x;
  gcry_mpi_t d;
  gcry_mpi_t n;
  gcry_ctx_t ctx;

  GNUNET_assert(0 == gcry_mpi_ec_new(&ctx, NULL, CURVE));

  n = gcry_mpi_ec_get_mpi("n", ctx, 1);
  GNUNET_CRYPTO_ecdsa_key_get_public(priv, &pub);

  h = derive_h(&pub, label, context);
  GNUNET_CRYPTO_mpi_scan_unsigned(&x, priv->d, sizeof(priv->d));
  d = gcry_mpi_new(256);
  gcry_mpi_mulm(d, h, x, n);
  gcry_mpi_release(h);
  gcry_mpi_release(x);
  gcry_mpi_release(n);
  gcry_ctx_release(ctx);
  ret = GNUNET_new(struct GNUNET_CRYPTO_EcdsaPrivateKey);
  GNUNET_CRYPTO_mpi_print_unsigned(ret->d, sizeof(ret->d), d);
  gcry_mpi_release(d);
  return ret;
}


void
GNUNET_CRYPTO_ecdsa_public_key_derive(
  const struct GNUNET_CRYPTO_EcdsaPublicKey *pub,
  const char *label,
  const char *context,
  struct GNUNET_CRYPTO_EcdsaPublicKey *result)
{
  gcry_ctx_t ctx;
  gcry_mpi_t q_y;
  gcry_mpi_t h;
  gcry_mpi_t n;
  gcry_mpi_t h_mod_n;
  gcry_mpi_point_t q;
  gcry_mpi_point_t v;

  GNUNET_assert(0 == gcry_mpi_ec_new(&ctx, NULL, CURVE));

  /* obtain point 'q' from original public key.  The provided 'q' is
     compressed thus we first store it in the context and then get it
     back as a (decompresssed) point.  */
  q_y = gcry_mpi_set_opaque_copy(NULL, pub->q_y, 8 * sizeof(pub->q_y));
  GNUNET_assert(NULL != q_y);
  GNUNET_assert(0 == gcry_mpi_ec_set_mpi("q", q_y, ctx));
  gcry_mpi_release(q_y);
  q = gcry_mpi_ec_get_point("q", ctx, 0);
  GNUNET_assert(q);

  /* calculate h_mod_n = h % n */
  h = derive_h(pub, label, context);
  n = gcry_mpi_ec_get_mpi("n", ctx, 1);
  h_mod_n = gcry_mpi_new(256);
  gcry_mpi_mod(h_mod_n, h, n);
  /* calculate v = h_mod_n * q */
  v = gcry_mpi_point_new(0);
  gcry_mpi_ec_mul(v, h_mod_n, q, ctx);
  gcry_mpi_release(h_mod_n);
  gcry_mpi_release(h);
  gcry_mpi_release(n);
  gcry_mpi_point_release(q);

  /* convert point 'v' to public key that we return */
  GNUNET_assert(0 == gcry_mpi_ec_set_point("q", v, ctx));
  gcry_mpi_point_release(v);
  q_y = gcry_mpi_ec_get_mpi("q@eddsa", ctx, 0);
  GNUNET_assert(q_y);
  GNUNET_CRYPTO_mpi_print_unsigned(result->q_y, sizeof(result->q_y), q_y);
  gcry_mpi_release(q_y);
  gcry_ctx_release(ctx);
}


static void
reverse_buffer(unsigned char *buffer, size_t length)
{
  unsigned char tmp;
  size_t i;

  for (i = 0; i < length / 2; i++)
    {
      tmp = buffer[i];
      buffer[i] = buffer[length - 1 - i];
      buffer[length - 1 - i] = tmp;
    }
}


static gcry_mpi_t
eddsa_d_to_a(gcry_mpi_t d)
{
  unsigned char rawmpi[32]; /* 256-bit value */
  size_t rawmpilen;
  unsigned char digest[64]; /* 512-bit hash value */
  gcry_buffer_t hvec[2];
  unsigned int b;
  gcry_mpi_t a;

  b = 256 / 8; /* number of bytes in `d` */

  /* Note that we clear DIGEST so we can use it as input to left pad
     the key with zeroes for hashing.  */
  memset(digest, 0, sizeof digest);
  memset(hvec, 0, sizeof hvec);
  rawmpilen = sizeof(rawmpi);
  GNUNET_assert(
    0 == gcry_mpi_print(GCRYMPI_FMT_USG, rawmpi, rawmpilen, &rawmpilen, d));
  hvec[0].data = digest;
  hvec[0].off = 0;
  hvec[0].len = b > rawmpilen ? (b - rawmpilen) : 0;
  hvec[1].data = rawmpi;
  hvec[1].off = 0;
  hvec[1].len = rawmpilen;
  GNUNET_assert(
    0 == gcry_md_hash_buffers(GCRY_MD_SHA512, 0 /* flags */, digest, hvec, 2));
  /* Compute the A value.  */
  reverse_buffer(digest, 32);  /* Only the first half of the hash.  */
  digest[0] = (digest[0] & 0x7f) | 0x40;
  digest[31] &= 0xf8;

  GNUNET_CRYPTO_mpi_scan_unsigned(&a, digest, 32);
  return a;
}


static int
point_to_hash(gcry_mpi_point_t result,
              gcry_ctx_t ctx,
              struct GNUNET_HashCode *key_material)
{
  gcry_mpi_t result_x;
  unsigned char xbuf[256 / 8];
  size_t rsize;

  /* finally, convert point to string for hashing */
  result_x = gcry_mpi_new(256);
  if (gcry_mpi_ec_get_affine(result_x, NULL, result, ctx))
    {
      LOG_GCRY(GNUNET_ERROR_TYPE_ERROR, "get_affine failed", 0);
      return GNUNET_SYSERR;
    }

  rsize = sizeof(xbuf);
  GNUNET_assert(!gcry_mpi_get_flag(result_x, GCRYMPI_FLAG_OPAQUE));
  /* result_x can be negative here, so we do not use 'GNUNET_CRYPTO_mpi_print_unsigned'
     as that does not include the sign bit; x should be a 255-bit
     value, so with the sign it should fit snugly into the 256-bit
     xbuf */
  GNUNET_assert(
    0 == gcry_mpi_print(GCRYMPI_FMT_STD, xbuf, rsize, &rsize, result_x));
  GNUNET_CRYPTO_hash(xbuf, rsize, key_material);
  gcry_mpi_release(result_x);
  return GNUNET_OK;
}


int
GNUNET_CRYPTO_eddsa_ecdh(const struct GNUNET_CRYPTO_EddsaPrivateKey *priv,
                         const struct GNUNET_CRYPTO_EcdhePublicKey *pub,
                         struct GNUNET_HashCode *key_material)
{
  gcry_mpi_point_t result;
  gcry_mpi_point_t q;
  gcry_mpi_t d;
  gcry_mpi_t a;
  gcry_ctx_t ctx;
  gcry_sexp_t pub_sexpr;
  int ret;

  BENCHMARK_START(eddsa_ecdh);

  /* first, extract the q = dP value from the public key */
  if (0 != gcry_sexp_build(&pub_sexpr,
                           NULL,
                           "(public-key(ecc(curve " CURVE ")(q %b)))",
                           (int)sizeof(pub->q_y),
                           pub->q_y))
    return GNUNET_SYSERR;
  GNUNET_assert(0 == gcry_mpi_ec_new(&ctx, pub_sexpr, NULL));
  gcry_sexp_release(pub_sexpr);
  q = gcry_mpi_ec_get_point("q", ctx, 0);

  /* second, extract the d value from our private key */
  GNUNET_CRYPTO_mpi_scan_unsigned(&d, priv->d, sizeof(priv->d));

  /* NOW, because this is EdDSA, HASH 'd' first! */
  a = eddsa_d_to_a(d);
  gcry_mpi_release(d);

  /* then call the 'multiply' function, to compute the product */
  result = gcry_mpi_point_new(0);
  gcry_mpi_ec_mul(result, a, q, ctx);
  gcry_mpi_point_release(q);
  gcry_mpi_release(a);

  ret = point_to_hash(result, ctx, key_material);
  gcry_mpi_point_release(result);
  gcry_ctx_release(ctx);
  BENCHMARK_END(eddsa_ecdh);
  return ret;
}


int
GNUNET_CRYPTO_ecdsa_ecdh(const struct GNUNET_CRYPTO_EcdsaPrivateKey *priv,
                         const struct GNUNET_CRYPTO_EcdhePublicKey *pub,
                         struct GNUNET_HashCode *key_material)
{
  gcry_mpi_point_t result;
  gcry_mpi_point_t q;
  gcry_mpi_t d;
  gcry_ctx_t ctx;
  gcry_sexp_t pub_sexpr;
  int ret;

  BENCHMARK_START(ecdsa_ecdh);

  /* first, extract the q = dP value from the public key */
  if (0 != gcry_sexp_build(&pub_sexpr,
                           NULL,
                           "(public-key(ecc(curve " CURVE ")(q %b)))",
                           (int)sizeof(pub->q_y),
                           pub->q_y))
    return GNUNET_SYSERR;
  GNUNET_assert(0 == gcry_mpi_ec_new(&ctx, pub_sexpr, NULL));
  gcry_sexp_release(pub_sexpr);
  q = gcry_mpi_ec_get_point("q", ctx, 0);

  /* second, extract the d value from our private key */
  GNUNET_CRYPTO_mpi_scan_unsigned(&d, priv->d, sizeof(priv->d));

  /* then call the 'multiply' function, to compute the product */
  result = gcry_mpi_point_new(0);
  gcry_mpi_ec_mul(result, d, q, ctx);
  gcry_mpi_point_release(q);
  gcry_mpi_release(d);

  /* finally, convert point to string for hashing */
  ret = point_to_hash(result, ctx, key_material);
  gcry_mpi_point_release(result);
  gcry_ctx_release(ctx);
  BENCHMARK_END(ecdsa_ecdh);
  return ret;
}


int
GNUNET_CRYPTO_ecdh_eddsa(const struct GNUNET_CRYPTO_EcdhePrivateKey *priv,
                         const struct GNUNET_CRYPTO_EddsaPublicKey *pub,
                         struct GNUNET_HashCode *key_material)
{
  gcry_mpi_point_t result;
  gcry_mpi_point_t q;
  gcry_mpi_t d;
  gcry_ctx_t ctx;
  gcry_sexp_t pub_sexpr;
  int ret;

  BENCHMARK_START(ecdh_eddsa);

  /* first, extract the q = dP value from the public key */
  if (0 != gcry_sexp_build(&pub_sexpr,
                           NULL,
                           "(public-key(ecc(curve " CURVE ")(q %b)))",
                           (int)sizeof(pub->q_y),
                           pub->q_y))
    return GNUNET_SYSERR;
  GNUNET_assert(0 == gcry_mpi_ec_new(&ctx, pub_sexpr, NULL));
  gcry_sexp_release(pub_sexpr);
  q = gcry_mpi_ec_get_point("q", ctx, 0);

  /* second, extract the d value from our private key */
  GNUNET_CRYPTO_mpi_scan_unsigned(&d, priv->d, sizeof(priv->d));

  /* then call the 'multiply' function, to compute the product */
  result = gcry_mpi_point_new(0);
  gcry_mpi_ec_mul(result, d, q, ctx);
  gcry_mpi_point_release(q);
  gcry_mpi_release(d);

  /* finally, convert point to string for hashing */
  ret = point_to_hash(result, ctx, key_material);
  gcry_mpi_point_release(result);
  gcry_ctx_release(ctx);
  BENCHMARK_END(ecdh_eddsa);
  return ret;
}

int
GNUNET_CRYPTO_ecdh_ecdsa(const struct GNUNET_CRYPTO_EcdhePrivateKey *priv,
                         const struct GNUNET_CRYPTO_EcdsaPublicKey *pub,
                         struct GNUNET_HashCode *key_material)
{
  return GNUNET_CRYPTO_ecdh_eddsa(priv,
                                  (const struct GNUNET_CRYPTO_EddsaPublicKey *)
                                  pub,
                                  key_material);
}

/* end of crypto_ecc.c */