gnsrecord_crypto.c

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/*
     This file is part of GNUnet.
     Copyright (C) 2009-2013, 2018 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 "gnunet_util_lib.h"
#include "gnunet_constants.h"
#include "gnunet_signatures.h"
#include "gnunet_arm_service.h"
#include "gnunet_gnsrecord_lib.h"
#include "gnunet_dnsparser_lib.h"
#include "gnunet_tun_lib.h"


#define LOG(kind, ...) GNUNET_log_from(kind, "gnsrecord", __VA_ARGS__)


static void
derive_block_aes_key(struct GNUNET_CRYPTO_SymmetricInitializationVector *iv,
                     struct GNUNET_CRYPTO_SymmetricSessionKey *skey,
                     const char *label,
                     const struct GNUNET_CRYPTO_EcdsaPublicKey *pub)
{
  static const char ctx_key[] = "gns-aes-ctx-key";
  static const char ctx_iv[] = "gns-aes-ctx-iv";

  GNUNET_CRYPTO_kdf(skey, sizeof(struct GNUNET_CRYPTO_SymmetricSessionKey),
                    pub, sizeof(struct GNUNET_CRYPTO_EcdsaPublicKey),
                    label, strlen(label),
                    ctx_key, strlen(ctx_key),
                    NULL, 0);
  GNUNET_CRYPTO_kdf(iv, sizeof(struct GNUNET_CRYPTO_SymmetricInitializationVector),
                    pub, sizeof(struct GNUNET_CRYPTO_EcdsaPublicKey),
                    label, strlen(label),
                    ctx_iv, strlen(ctx_iv),
                    NULL, 0);
}


struct GNUNET_GNSRECORD_Block *
block_create(const struct GNUNET_CRYPTO_EcdsaPrivateKey *key,
             const struct GNUNET_CRYPTO_EcdsaPublicKey *pkey,
             struct GNUNET_TIME_Absolute expire,
             const char *label,
             const struct GNUNET_GNSRECORD_Data *rd,
             unsigned int rd_count)
{
  ssize_t payload_len = GNUNET_GNSRECORD_records_get_size(rd_count,
                                                          rd);
  struct GNUNET_GNSRECORD_Block *block;
  struct GNUNET_CRYPTO_EcdsaPrivateKey *dkey;
  struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
  struct GNUNET_CRYPTO_SymmetricSessionKey skey;
  struct GNUNET_GNSRECORD_Data rdc[GNUNET_NZL(rd_count)];
  uint32_t rd_count_nbo;
  struct GNUNET_TIME_Absolute now;

  if (payload_len < 0)
    {
      GNUNET_break(0);
      return NULL;
    }
  if (payload_len > GNUNET_GNSRECORD_MAX_BLOCK_SIZE)
    {
      GNUNET_break(0);
      return NULL;
    }
  /* convert relative to absolute times */
  now = GNUNET_TIME_absolute_get();
  for (unsigned int i = 0; i < rd_count; i++)
    {
      rdc[i] = rd[i];
      if (0 != (rd[i].flags & GNUNET_GNSRECORD_RF_RELATIVE_EXPIRATION))
        {
          struct GNUNET_TIME_Relative t;

          /* encrypted blocks must never have relative expiration times, convert! */
          rdc[i].flags &= ~GNUNET_GNSRECORD_RF_RELATIVE_EXPIRATION;
          t.rel_value_us = rdc[i].expiration_time;
          rdc[i].expiration_time = GNUNET_TIME_absolute_add(now, t).abs_value_us;
        }
    }
  /* serialize */
  rd_count_nbo = htonl(rd_count);
  {
    char payload[sizeof(uint32_t) + payload_len];

    GNUNET_memcpy(payload,
                  &rd_count_nbo,
                  sizeof(uint32_t));
    GNUNET_assert(payload_len ==
                  GNUNET_GNSRECORD_records_serialize(rd_count,
                                                     rdc,
                                                     payload_len,
                                                     &payload[sizeof(uint32_t)]));
    block = GNUNET_malloc(sizeof(struct GNUNET_GNSRECORD_Block) +
                          sizeof(uint32_t) +
                          payload_len);
    block->purpose.size = htonl(sizeof(uint32_t) +
                                payload_len +
                                sizeof(struct GNUNET_CRYPTO_EccSignaturePurpose) +
                                sizeof(struct GNUNET_TIME_AbsoluteNBO));
    block->purpose.purpose = htonl(GNUNET_SIGNATURE_PURPOSE_GNS_RECORD_SIGN);
    block->expiration_time = GNUNET_TIME_absolute_hton(expire);
    /* encrypt and sign */
    dkey = GNUNET_CRYPTO_ecdsa_private_key_derive(key,
                                                  label,
                                                  "gns");
    GNUNET_CRYPTO_ecdsa_key_get_public(dkey,
                                       &block->derived_key);
    derive_block_aes_key(&iv,
                         &skey,
                         label,
                         pkey);
    GNUNET_break(payload_len + sizeof(uint32_t) ==
                 GNUNET_CRYPTO_symmetric_encrypt(payload,
                                                 payload_len + sizeof(uint32_t),
                                                 &skey,
                                                 &iv,
                                                 &block[1]));
  }
  if (GNUNET_OK !=
      GNUNET_CRYPTO_ecdsa_sign(dkey,
                               &block->purpose,
                               &block->signature))
    {
      GNUNET_break(0);
      GNUNET_free(dkey);
      GNUNET_free(block);
      return NULL;
    }
  GNUNET_free(dkey);
  return block;
}


struct GNUNET_GNSRECORD_Block *
GNUNET_GNSRECORD_block_create(const struct GNUNET_CRYPTO_EcdsaPrivateKey *key,
                              struct GNUNET_TIME_Absolute expire,
                              const char *label,
                              const struct GNUNET_GNSRECORD_Data *rd,
                              unsigned int rd_count)
{
  struct GNUNET_CRYPTO_EcdsaPublicKey pkey;

  GNUNET_CRYPTO_ecdsa_key_get_public(key,
                                     &pkey);
  return block_create(key,
                      &pkey,
                      expire,
                      label,
                      rd,
                      rd_count);
}


struct KeyCacheLine {
  struct GNUNET_CRYPTO_EcdsaPrivateKey key;

  struct GNUNET_CRYPTO_EcdsaPublicKey pkey;
};


struct GNUNET_GNSRECORD_Block *
GNUNET_GNSRECORD_block_create2(const struct GNUNET_CRYPTO_EcdsaPrivateKey *key,
                               struct GNUNET_TIME_Absolute expire,
                               const char *label,
                               const struct GNUNET_GNSRECORD_Data *rd,
                               unsigned int rd_count)
{
#define CSIZE 64
  static struct KeyCacheLine cache[CSIZE];
  struct KeyCacheLine *line;

  line = &cache[(*(unsigned int *)key) % CSIZE];
  if (0 != memcmp(&line->key,
                  key,
                  sizeof(*key)))
    {
      /* cache miss, recompute */
      line->key = *key;
      GNUNET_CRYPTO_ecdsa_key_get_public(key,
                                         &line->pkey);
    }
#undef CSIZE
  return block_create(key,
                      &line->pkey,
                      expire,
                      label,
                      rd,
                      rd_count);
}



int
GNUNET_GNSRECORD_block_verify(const struct GNUNET_GNSRECORD_Block *block)
{
  return GNUNET_CRYPTO_ecdsa_verify(GNUNET_SIGNATURE_PURPOSE_GNS_RECORD_SIGN,
                                    &block->purpose,
                                    &block->signature,
                                    &block->derived_key);
}


int
GNUNET_GNSRECORD_block_decrypt(const struct GNUNET_GNSRECORD_Block *block,
                               const struct GNUNET_CRYPTO_EcdsaPublicKey *zone_key,
                               const char *label,
                               GNUNET_GNSRECORD_RecordCallback proc,
                               void *proc_cls)
{
  size_t payload_len = ntohl(block->purpose.size) -
                       sizeof(struct GNUNET_CRYPTO_EccSignaturePurpose) -
                       sizeof(struct GNUNET_TIME_AbsoluteNBO);
  struct GNUNET_CRYPTO_SymmetricInitializationVector iv;
  struct GNUNET_CRYPTO_SymmetricSessionKey skey;

  if (ntohl(block->purpose.size) <
      sizeof(struct GNUNET_CRYPTO_EccSignaturePurpose) +
      sizeof(struct GNUNET_TIME_AbsoluteNBO))
    {
      GNUNET_break_op(0);
      return GNUNET_SYSERR;
    }
  derive_block_aes_key(&iv,
                       &skey,
                       label,
                       zone_key);
  {
    char payload[payload_len];
    uint32_t rd_count;

    GNUNET_break(payload_len ==
                 GNUNET_CRYPTO_symmetric_decrypt(&block[1], payload_len,
                                                 &skey, &iv,
                                                 payload));
    GNUNET_memcpy(&rd_count,
                  payload,
                  sizeof(uint32_t));
    rd_count = ntohl(rd_count);
    if (rd_count > 2048)
      {
        /* limit to sane value */
        GNUNET_break_op(0);
        return GNUNET_SYSERR;
      }
    {
      struct GNUNET_GNSRECORD_Data rd[GNUNET_NZL(rd_count)];
      unsigned int j;
      struct GNUNET_TIME_Absolute now;

      if (GNUNET_OK !=
          GNUNET_GNSRECORD_records_deserialize(payload_len - sizeof(uint32_t),
                                               &payload[sizeof(uint32_t)],
                                               rd_count,
                                               rd))
        {
          GNUNET_break_op(0);
          return GNUNET_SYSERR;
        }
      /* hide expired records */
      now = GNUNET_TIME_absolute_get();
      j = 0;
      for (unsigned int i = 0; i < rd_count; i++)
        {
          if (0 != (rd[i].flags & GNUNET_GNSRECORD_RF_RELATIVE_EXPIRATION))
            {
              /* encrypted blocks must never have relative expiration times, skip! */
              GNUNET_break_op(0);
              continue;
            }

          if (0 != (rd[i].flags & GNUNET_GNSRECORD_RF_SHADOW_RECORD))
            {
              int include_record = GNUNET_YES;
              /* Shadow record, figure out if we have a not expired active record */
              for (unsigned int k = 0; k < rd_count; k++)
                {
                  if (k == i)
                    continue;
                  if (rd[i].expiration_time < now.abs_value_us)
                    include_record = GNUNET_NO; /* Shadow record is expired */
                  if ((rd[k].record_type == rd[i].record_type) &&
                      (rd[k].expiration_time >= now.abs_value_us) &&
                      (0 == (rd[k].flags & GNUNET_GNSRECORD_RF_SHADOW_RECORD)))
                    {
                      include_record = GNUNET_NO; /* We have a non-expired, non-shadow record of the same type */
                      GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                                 "Ignoring shadow record\n");
                      break;
                    }
                }
              if (GNUNET_YES == include_record)
                {
                  rd[i].flags ^= GNUNET_GNSRECORD_RF_SHADOW_RECORD; /* Remove Flag */
                  if (j != i)
                    rd[j] = rd[i];
                  j++;
                }
            }
          else if (rd[i].expiration_time >= now.abs_value_us)
            {
              /* Include this record */
              if (j != i)
                rd[j] = rd[i];
              j++;
            }
          else
            {
              struct GNUNET_TIME_Absolute at;

              at.abs_value_us = rd[i].expiration_time;
              GNUNET_log(GNUNET_ERROR_TYPE_INFO,
                         "Excluding record that expired %s (%llu ago)\n",
                         GNUNET_STRINGS_absolute_time_to_string(at),
                         (unsigned long long)rd[i].expiration_time - now.abs_value_us);
            }
        }
      rd_count = j;
      if (NULL != proc)
        proc(proc_cls,
             rd_count,
             (0 != rd_count) ? rd : NULL);
    }
  }
  return GNUNET_OK;
}


void
GNUNET_GNSRECORD_query_from_private_key(const struct GNUNET_CRYPTO_EcdsaPrivateKey *zone,
                                        const char *label,
                                        struct GNUNET_HashCode *query)
{
  struct GNUNET_CRYPTO_EcdsaPublicKey pub;

  GNUNET_CRYPTO_ecdsa_key_get_public(zone,
                                     &pub);
  GNUNET_GNSRECORD_query_from_public_key(&pub,
                                         label,
                                         query);
}


void
GNUNET_GNSRECORD_query_from_public_key(const struct GNUNET_CRYPTO_EcdsaPublicKey *pub,
                                       const char *label,
                                       struct GNUNET_HashCode *query)
{
  struct GNUNET_CRYPTO_EcdsaPublicKey pd;

  GNUNET_CRYPTO_ecdsa_public_key_derive(pub,
                                        label,
                                        "gns",
                                        &pd);
  GNUNET_CRYPTO_hash(&pd,
                     sizeof(pd),
                     query);
}


/* end of gnsrecord_crypto.c */