/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <folly/ssl/OpenSSLCertUtils.h>

#include <folly/FileUtil.h>
#include <folly/ScopeGuard.h>
#include <folly/String.h>
#include <folly/ssl/OpenSSLPtrTypes.h>

namespace folly {
namespace ssl {

namespace {
std::string getOpenSSLErrorString(unsigned long err) {
  std::array<char, 256> errBuff;
  ERR_error_string_n(err, errBuff.data(), errBuff.size());
  return std::string(errBuff.data());
}
} // namespace

Optional<std::string> OpenSSLCertUtils::getCommonName(X509& x509) {
  auto subject = X509_get_subject_name(&x509);
  if (!subject) {
    return none;
  }

  auto cnLoc = X509_NAME_get_index_by_NID(subject, NID_commonName, -1);
  if (cnLoc < 0) {
    return none;
  }

  auto cnEntry = X509_NAME_get_entry(subject, cnLoc);
  if (!cnEntry) {
    return none;
  }

  auto cnAsn = X509_NAME_ENTRY_get_data(cnEntry);
  if (!cnAsn) {
    return none;
  }

  auto cnData = reinterpret_cast<const char*>(ASN1_STRING_get0_data(cnAsn));
  auto cnLen = ASN1_STRING_length(cnAsn);
  if (!cnData || cnLen <= 0) {
    return none;
  }

  return Optional<std::string>(std::string(cnData, cnLen));
}

std::vector<std::string> OpenSSLCertUtils::getSubjectAltNames(X509& x509) {
  auto names = reinterpret_cast<STACK_OF(GENERAL_NAME)*>(
      X509_get_ext_d2i(&x509, NID_subject_alt_name, nullptr, nullptr));
  if (!names) {
    return {};
  }
  SCOPE_EXIT { sk_GENERAL_NAME_pop_free(names, GENERAL_NAME_free); };

  std::vector<std::string> ret;
  auto count = sk_GENERAL_NAME_num(names);
  for (int i = 0; i < count; i++) {
    auto genName = sk_GENERAL_NAME_value(names, i);
    if (!genName || genName->type != GEN_DNS) {
      continue;
    }
    auto nameData = reinterpret_cast<const char*>(
        ASN1_STRING_get0_data(genName->d.dNSName));
    auto nameLen = ASN1_STRING_length(genName->d.dNSName);
    if (!nameData || nameLen <= 0) {
      continue;
    }
    ret.emplace_back(nameData, nameLen);
  }
  return ret;
}

Optional<std::string> OpenSSLCertUtils::getSubject(X509& x509) {
  auto subject = X509_get_subject_name(&x509);
  if (!subject) {
    return none;
  }

  auto bio = BioUniquePtr(BIO_new(BIO_s_mem()));
  if (bio == nullptr) {
    throw std::runtime_error("Cannot allocate bio");
  }
  if (X509_NAME_print_ex(bio.get(), subject, 0, XN_FLAG_ONELINE) <= 0) {
    return none;
  }

  char* bioData = nullptr;
  size_t bioLen = BIO_get_mem_data(bio.get(), &bioData);
  return std::string(bioData, bioLen);
}

Optional<std::string> OpenSSLCertUtils::getIssuer(X509& x509) {
  auto issuer = X509_get_issuer_name(&x509);
  if (!issuer) {
    return none;
  }

  auto bio = BioUniquePtr(BIO_new(BIO_s_mem()));
  if (bio == nullptr) {
    throw std::runtime_error("Cannot allocate bio");
  }

  if (X509_NAME_print_ex(bio.get(), issuer, 0, XN_FLAG_ONELINE) <= 0) {
    return none;
  }

  char* bioData = nullptr;
  size_t bioLen = BIO_get_mem_data(bio.get(), &bioData);
  return std::string(bioData, bioLen);
}

folly::Optional<std::string> OpenSSLCertUtils::toString(X509& x509) {
  auto in = BioUniquePtr(BIO_new(BIO_s_mem()));
  if (in == nullptr) {
    throw std::runtime_error("Cannot allocate bio");
  }

  int flags = 0;

  flags |= X509_FLAG_NO_HEADER | /* A few bytes of cert and data */
      X509_FLAG_NO_PUBKEY | /* Public key */
      X509_FLAG_NO_AUX | /* Auxiliary info? */
      X509_FLAG_NO_SIGDUMP | /* Prints the signature */
      X509_FLAG_NO_SIGNAME; /* Signature algorithms */

#ifdef X509_FLAG_NO_IDS
  flags |= X509_FLAG_NO_IDS; /* Issuer/subject IDs */
#endif

  if (X509_print_ex(in.get(), &x509, XN_FLAG_ONELINE, flags) > 0) {
    char* bioData = nullptr;
    size_t bioLen = BIO_get_mem_data(in.get(), &bioData);
    return std::string(bioData, bioLen);
  } else {
    return none;
  }
}

std::string OpenSSLCertUtils::getNotAfterTime(X509& x509) {
  return getDateTimeStr(X509_get0_notAfter(&x509));
}

std::string OpenSSLCertUtils::getNotBeforeTime(X509& x509) {
  return getDateTimeStr(X509_get0_notBefore(&x509));
}

std::chrono::system_clock::time_point OpenSSLCertUtils::asnTimeToTimepoint(
    const ASN1_TIME* asnTime) {
  int dSecs = 0;
  int dDays = 0;

  auto epoch_time_t = std::chrono::system_clock::to_time_t(
      std::chrono::system_clock::time_point());
  folly::ssl::ASN1TimeUniquePtr epoch_asn(ASN1_TIME_set(nullptr, epoch_time_t));

  if (!epoch_asn) {
    throw std::runtime_error("failed to allocate epoch asn.1 time");
  }

  if (ASN1_TIME_diff(&dDays, &dSecs, epoch_asn.get(), asnTime) != 1) {
    throw std::runtime_error("invalid asn.1 time");
  }

  return std::chrono::system_clock::time_point(
      std::chrono::seconds(dSecs) + std::chrono::hours(24 * dDays));
}

std::string OpenSSLCertUtils::getDateTimeStr(const ASN1_TIME* time) {
  if (!time) {
    return "";
  }

  auto bio = BioUniquePtr(BIO_new(BIO_s_mem()));
  if (bio == nullptr) {
    throw std::runtime_error("Cannot allocate bio");
  }

  if (ASN1_TIME_print(bio.get(), time) <= 0) {
    throw std::runtime_error("Cannot print ASN1_TIME");
  }

  char* bioData = nullptr;
  size_t bioLen = BIO_get_mem_data(bio.get(), &bioData);
  return std::string(bioData, bioLen);
}

X509UniquePtr OpenSSLCertUtils::derDecode(ByteRange range) {
  auto begin = range.data();
  X509UniquePtr cert(d2i_X509(nullptr, &begin, range.size()));
  if (!cert) {
    throw std::runtime_error("could not read cert");
  }
  return cert;
}

std::unique_ptr<IOBuf> OpenSSLCertUtils::derEncode(X509& x509) {
  auto len = i2d_X509(&x509, nullptr);
  if (len < 0) {
    throw std::runtime_error("Error computing length");
  }
  auto buf = IOBuf::create(len);
  auto dataPtr = buf->writableData();
  len = i2d_X509(&x509, &dataPtr);
  if (len < 0) {
    throw std::runtime_error("Error converting cert to DER");
  }
  buf->append(len);
  return buf;
}

std::vector<X509UniquePtr> OpenSSLCertUtils::readCertsFromBuffer(
    ByteRange range) {
  BioUniquePtr b(
      BIO_new_mem_buf(const_cast<unsigned char*>(range.data()), range.size()));
  if (!b) {
    throw std::runtime_error("failed to create BIO");
  }
  std::vector<X509UniquePtr> certs;
  ERR_clear_error();
  while (true) {
    X509UniquePtr x509(PEM_read_bio_X509(b.get(), nullptr, nullptr, nullptr));
    if (x509) {
      certs.push_back(std::move(x509));
      continue;
    }
    auto err = ERR_get_error();
    ERR_clear_error();
    if (BIO_eof(b.get()) && ERR_GET_LIB(err) == ERR_LIB_PEM &&
        ERR_GET_REASON(err) == PEM_R_NO_START_LINE) {
      // Reach end of buffer.
      break;
    }
    throw std::runtime_error(folly::to<std::string>(
        "Unable to parse cert ",
        certs.size(),
        ": ",
        getOpenSSLErrorString(err)));
  }
  return certs;
}

std::array<uint8_t, SHA_DIGEST_LENGTH> OpenSSLCertUtils::getDigestSha1(
    X509& x509) {
  unsigned int len;
  std::array<uint8_t, SHA_DIGEST_LENGTH> md;
  int rc = X509_digest(&x509, EVP_sha1(), md.data(), &len);

  if (rc <= 0) {
    throw std::runtime_error("Could not calculate SHA1 digest for cert");
  }
  return md;
}

std::array<uint8_t, SHA256_DIGEST_LENGTH> OpenSSLCertUtils::getDigestSha256(
    X509& x509) {
  unsigned int len;
  std::array<uint8_t, SHA256_DIGEST_LENGTH> md;
  int rc = X509_digest(&x509, EVP_sha256(), md.data(), &len);

  if (rc <= 0) {
    throw std::runtime_error("Could not calculate SHA256 digest for cert");
  }
  return md;
}

X509StoreUniquePtr OpenSSLCertUtils::readStoreFromFile(std::string caFile) {
  std::string certData;
  if (!folly::readFile(caFile.c_str(), certData)) {
    throw std::runtime_error(
        folly::to<std::string>("Could not read store file: ", caFile));
  }
  return readStoreFromBuffer(folly::StringPiece(certData));
}

X509StoreUniquePtr OpenSSLCertUtils::readStoreFromBuffer(ByteRange certRange) {
  auto certs = readCertsFromBuffer(certRange);
  ERR_clear_error();
  folly::ssl::X509StoreUniquePtr store(X509_STORE_new());
  for (auto& caCert : certs) {
    if (X509_STORE_add_cert(store.get(), caCert.get()) != 1) {
      auto err = ERR_get_error();
      if (ERR_GET_LIB(err) != ERR_LIB_X509 ||
          ERR_GET_REASON(err) != X509_R_CERT_ALREADY_IN_HASH_TABLE) {
        throw std::runtime_error(folly::to<std::string>(
            "Could not insert CA certificate into store: ",
            getOpenSSLErrorString(err)));
      }
    }
  }
  return store;
}
} // namespace ssl
} // namespace folly
