monero/src/cryptonote_core/tx_sanity_check.cpp

// Copyright (c) 2019-2020, The Monero Project
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#include <stdint.h>
#include <vector>
#include "cryptonote_basic/cryptonote_basic.h"
#include "cryptonote_basic/cryptonote_format_utils.h"
#include "blockchain.h"
#include "tx_sanity_check.h"

#undef MONERO_DEFAULT_LOG_CATEGORY
#define MONERO_DEFAULT_LOG_CATEGORY "verify"

namespace cryptonote
{

bool tx_sanity_check(const cryptonote::blobdata &tx_blob, uint64_t rct_outs_available)
{
  cryptonote::transaction tx;

  if (!cryptonote::parse_and_validate_tx_from_blob(tx_blob, tx))
  {
    MERROR("Failed to parse transaction");
    return false;
  }

  if (cryptonote::is_coinbase(tx))
  {
    MERROR("Transaction is coinbase");
    return false;
  }
  std::set<uint64_t> rct_indices;
  size_t n_indices = 0;

  for (const auto &txin : tx.vin)
  {
    if (txin.type() != typeid(cryptonote::txin_to_key))
      continue;
    const cryptonote::txin_to_key &in_to_key = boost::get<cryptonote::txin_to_key>(txin);
    if (in_to_key.amount != 0)
      continue;
    const std::vector<uint64_t> absolute = cryptonote::relative_output_offsets_to_absolute(in_to_key.key_offsets);
    for (uint64_t offset: absolute)
      rct_indices.insert(offset);
    n_indices += in_to_key.key_offsets.size();
  }

  return tx_sanity_check(rct_indices, n_indices, rct_outs_available);
}

bool tx_sanity_check(const std::set<uint64_t> &rct_indices, size_t n_indices, uint64_t rct_outs_available)
{
  if (n_indices <= 10)
  {
    MDEBUG("n_indices is only " << n_indices << ", not checking");
    return true;
  }

  if (rct_outs_available < 10000)
    return true;

  if (rct_indices.size() < n_indices * 8 / 10)
  {
    MERROR("amount of unique indices is too low (amount of rct indices is " << rct_indices.size() << ", out of total " << n_indices << "indices.");
    return false;
  }

  std::vector<uint64_t> offsets(rct_indices.begin(), rct_indices.end());
  uint64_t median = epee::misc_utils::median(offsets);
  if (median < rct_outs_available * 6 / 10)
  {
    MERROR("median offset index is too low (median is " << median << " out of total " << rct_outs_available << "offsets). Transactions should contain a higher fraction of recent outputs.");
    return false;
  }

  return true;
}

}