src/challenge/challenge-possession.cpp

/*
 * Copyright (c) 2017-2023, Regents of the University of California.
 *
 * This file is part of ndncert, a certificate management system based on NDN.
 *
 * ndncert is free software: you can redistribute it and/or modify it under the terms
 * of the GNU General Public License as published by the Free Software Foundation, either
 * version 3 of the License, or (at your option) any later version.
 *
 * ndncert 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 General Public License for more details.
 *
 * You should have received copies of the GNU General Public License along with
 * ndncert, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
 *
 * See AUTHORS.md for complete list of ndncert authors and contributors.
 */

#include "challenge-possession.hpp"

#include <ndn-cxx/security/signing-helpers.hpp>
#include <ndn-cxx/security/transform/public-key.hpp>
#include <ndn-cxx/security/verification-helpers.hpp>
#include <ndn-cxx/util/io.hpp>
#include <ndn-cxx/util/random.hpp>

#include <boost/property_tree/json_parser.hpp>

namespace ndncert {

NDN_LOG_INIT(ndncert.challenge.possession);
NDNCERT_REGISTER_CHALLENGE(ChallengePossession, "possession");

const std::string ChallengePossession::PARAMETER_KEY_CREDENTIAL_CERT = "issued-cert";
const std::string ChallengePossession::PARAMETER_KEY_NONCE = "nonce";
const std::string ChallengePossession::PARAMETER_KEY_PROOF = "proof";
const std::string ChallengePossession::NEED_PROOF = "need-proof";

ChallengePossession::ChallengePossession(const std::string& configPath)
  : ChallengeModule("Possession", 1, time::seconds(60))
{
  if (configPath.empty()) {
    m_configFile = std::string(NDNCERT_SYSCONFDIR) + "/ndncert/challenge-credential.conf";
  }
  else {
    m_configFile = configPath;
  }
}

void
ChallengePossession::parseConfigFile()
{
  JsonSection config;
  try {
    boost::property_tree::read_json(m_configFile, config);
  }
  catch (const boost::property_tree::file_parser_error& error) {
    NDN_THROW(std::runtime_error("Failed to parse configuration file " + m_configFile + ": " +
                                 error.message() + " on line " + std::to_string(error.line())));
  }

  if (config.begin() == config.end()) {
    NDN_THROW(std::runtime_error("Error processing configuration file: " + m_configFile + " no data"));
  }

  m_trustAnchors.clear();
  auto anchorList = config.get_child("anchor-list");
  auto it = anchorList.begin();
  for (; it != anchorList.end(); it++) {
    std::istringstream ss(it->second.get("certificate", ""));
    auto cert = ndn::io::load<Certificate>(ss);
    if (cert == nullptr) {
      NDN_LOG_ERROR("Cannot load the certificate from config file");
      continue;
    }
    m_trustAnchors.push_back(*cert);
  }
}

// For CA
std::tuple<ErrorCode, std::string>
ChallengePossession::handleChallengeRequest(const Block& params, ca::RequestState& request)
{
  params.parse();
  if (m_trustAnchors.empty()) {
    parseConfigFile();
  }
  Certificate credential;
  const uint8_t* signature = nullptr;
  size_t signatureLen = 0;
  const auto& elements = params.elements();
  for (size_t i = 0; i < elements.size() - 1; i++) {
    if (elements[i].type() == tlv::ParameterKey && elements[i + 1].type() == tlv::ParameterValue) {
      if (readString(elements[i]) == PARAMETER_KEY_CREDENTIAL_CERT) {
        try {
          credential.wireDecode(elements[i + 1].blockFromValue());
        }
        catch (const std::exception& e) {
          NDN_LOG_ERROR("Cannot load challenge parameter: credential " << e.what());
          return returnWithError(request, ErrorCode::INVALID_PARAMETER,
                                 "Cannot challenge credential: credential."s + e.what());
        }
      }
      else if (readString(elements[i]) == PARAMETER_KEY_PROOF) {
        signature = elements[i + 1].value();
        signatureLen = elements[i + 1].value_size();
      }
    }
  }

  // verify the credential and the self-signed cert
  if (request.status == Status::BEFORE_CHALLENGE) {
    NDN_LOG_TRACE("Challenge Interest arrives. Check certificate and init the challenge");

    // check the certificate
    if (!credential.hasContent() || signatureLen != 0) {
      return returnWithError(request, ErrorCode::BAD_INTEREST_FORMAT, "Cannot find certificate");
    }
    auto keyLocator = credential.getSignatureInfo().getKeyLocator().getName();
    ndn::security::transform::PublicKey key;
    key.loadPkcs8(credential.getPublicKey());
    bool checkOK = std::any_of(m_trustAnchors.begin(), m_trustAnchors.end(), [&] (const auto& anchor) {
      return (anchor.getKeyName() == keyLocator || anchor.getName() == keyLocator) &&
             ndn::security::verifySignature(credential, anchor);
    });
    if (!checkOK) {
      return returnWithError(request, ErrorCode::INVALID_PARAMETER, "Certificate cannot be verified");
    }

    // for the first time, init the challenge
    std::array<uint8_t, 16> secretCode{};
    ndn::random::generateSecureBytes(secretCode);
    JsonSection secretJson;
    secretJson.add(PARAMETER_KEY_NONCE, ndn::toHex(secretCode));
    secretJson.add(PARAMETER_KEY_CREDENTIAL_CERT, ndn::toHex(credential.wireEncode()));
    NDN_LOG_TRACE("Secret for request " << ndn::toHex(request.requestId) << " : " << ndn::toHex(secretCode));
    return returnWithNewChallengeStatus(request, NEED_PROOF, std::move(secretJson), m_maxAttemptTimes, m_secretLifetime);
  }
  else if (request.challengeState && request.challengeState->challengeStatus == NEED_PROOF) {
    NDN_LOG_TRACE("Challenge Interest (proof) arrives. Check the proof");
    //check the format and load credential
    if (credential.hasContent() || signatureLen == 0) {
      return returnWithError(request, ErrorCode::BAD_INTEREST_FORMAT, "Cannot find certificate");
    }
    credential = Certificate(Block(ndn::fromHex(request.challengeState->secrets.get(PARAMETER_KEY_CREDENTIAL_CERT, ""))));
    auto secretCode = *ndn::fromHex(request.challengeState->secrets.get(PARAMETER_KEY_NONCE, ""));

    //check the proof
    ndn::security::transform::PublicKey key;
    key.loadPkcs8(credential.getPublicKey());
    if (ndn::security::verifySignature({secretCode}, {signature, signatureLen}, key)) {
      return returnWithSuccess(request);
    }
    return returnWithError(request, ErrorCode::INVALID_PARAMETER,
                           "Cannot verify the proof of private key against credential.");
  }
  NDN_LOG_TRACE("Proof of possession: bad state");
  return returnWithError(request, ErrorCode::INVALID_PARAMETER, "Fail to recognize the request.");
}

// For Client
std::multimap<std::string, std::string>
ChallengePossession::getRequestedParameterList(Status status, const std::string& challengeStatus)
{
  std::multimap<std::string, std::string> result;
  if (status == Status::BEFORE_CHALLENGE) {
    result.emplace(PARAMETER_KEY_CREDENTIAL_CERT, "Please provide the certificate issued by a trusted CA.");
    return result;
  }
  else if (status == Status::CHALLENGE && challengeStatus == NEED_PROOF) {
    result.emplace(PARAMETER_KEY_PROOF, "Please sign a Data packet with request ID as the content.");
  }
  else {
    NDN_THROW(std::runtime_error("Unexpected status or challenge status."));
  }
  return result;
}

Block
ChallengePossession::genChallengeRequestTLV(Status status, const std::string& challengeStatus,
                                            const std::multimap<std::string, std::string>& params)
{
  Block request(tlv::EncryptedPayload);
  if (status == Status::BEFORE_CHALLENGE) {
    if (params.size() != 1) {
      NDN_THROW(std::runtime_error("Wrong parameter provided."));
    }
    request.push_back(ndn::makeStringBlock(tlv::SelectedChallenge, CHALLENGE_TYPE));
    for (const auto& item : params) {
      if (std::get<0>(item) == PARAMETER_KEY_CREDENTIAL_CERT) {
        request.push_back(ndn::makeStringBlock(tlv::ParameterKey, PARAMETER_KEY_CREDENTIAL_CERT));
        Block valueBlock(tlv::ParameterValue);
        auto& certTlvStr = std::get<1>(item);
        valueBlock.push_back(Block(ndn::make_span(reinterpret_cast<const uint8_t*>(certTlvStr.data()),
                                                  certTlvStr.size())));
        request.push_back(valueBlock);
      }
      else {
        NDN_THROW(std::runtime_error("Wrong parameter provided."));
      }
    }
  }
  else if (status == Status::CHALLENGE && challengeStatus == NEED_PROOF) {
    if (params.size() != 1) {
      NDN_THROW(std::runtime_error("Wrong parameter provided."));
    }
    for (const auto& item : params) {
      if (std::get<0>(item) == PARAMETER_KEY_PROOF) {
        request.push_back(ndn::makeStringBlock(tlv::ParameterKey, PARAMETER_KEY_PROOF));
        request.push_back(ndn::makeStringBlock(tlv::ParameterValue, std::get<1>(item)));
      }
      else {
        NDN_THROW(std::runtime_error("Wrong parameter provided."));
      }
    }
  }
  else {
    NDN_THROW(std::runtime_error("Unexpected status or challenge status."));
  }
  request.encode();
  return request;
}

void
ChallengePossession::fulfillParameters(std::multimap<std::string, std::string>& params,
                                       ndn::KeyChain& keyChain, const Name& issuedCertName,
                                       ndn::span<const uint8_t, 16> nonce)
{
  auto keyName = ndn::security::extractKeyNameFromCertName(issuedCertName);
  auto id = keyChain.getPib().getIdentity(ndn::security::extractIdentityFromCertName(issuedCertName));
  auto issuedCert = id.getKey(keyName).getCertificate(issuedCertName);
  const auto& issuedCertTlv = issuedCert.wireEncode();
  auto signature = keyChain.getTpm().sign({nonce}, keyName, ndn::DigestAlgorithm::SHA256);

  for (auto& [key, val] : params) {
    if (key == PARAMETER_KEY_CREDENTIAL_CERT) {
      val = std::string(reinterpret_cast<const char*>(issuedCertTlv.data()), issuedCertTlv.size());
    }
    else if (key == PARAMETER_KEY_PROOF) {
      val = std::string(signature->get<char>(), signature->size());
    }
  }
}

} // namespace ndncert