/*
 *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

// Handling of certificates and keypairs for SSLStreamAdapter's peer mode.
#include "rtc_base/ssl_identity.h"

#include <openssl/ossl_typ.h>

#include <cstdint>
#include <cstring>
#include <ctime>
#include <memory>
#include <optional>
#include <string>
#include <utility>

#include "absl/strings/string_view.h"
#include "api/array_view.h"
#include "rtc_base/checks.h"
#ifdef OPENSSL_IS_BORINGSSL
#include "rtc_base/boringssl_identity.h"
#else
#include "rtc_base/openssl_identity.h"
#endif
#include "rtc_base/base64.h"
#include "rtc_base/strings/string_builder.h"
#include "rtc_base/time_utils.h"

namespace webrtc {

//////////////////////////////////////////////////////////////////////
// Helper Functions
//////////////////////////////////////////////////////////////////////

namespace {
// Read `n` bytes from ASN1 number string at *`pp` and return the numeric value.
// Update *`pp` and *`np` to reflect number of read bytes.
// TODO(bugs.webrtc.org/9860) - Remove this code.
inline int ASN1ReadInt(const unsigned char** pp, size_t* np, size_t n) {
  const unsigned char* p = *pp;
  int x = 0;
  for (size_t i = 0; i < n; i++) {
    x = 10 * x + p[i] - '0';
  }
  *pp = p + n;
  *np = *np - n;
  return x;
}

}  // namespace

// TODO(bugs.webrtc.org/9860) - Remove this code.
int64_t ASN1TimeToSec(const unsigned char* s, size_t length, bool long_format) {
  size_t bytes_left = length;
  // Make sure the string ends with Z.  Doing it here protects the strspn call
  // from running off the end of the string in Z's absense.
  if (length == 0 || s[length - 1] != 'Z') {
    return -1;
  }
  // Make sure we only have ASCII digits so that we don't need to clutter the
  // code below and ASN1ReadInt with error checking.
  size_t n = strspn(reinterpret_cast<const char*>(s), "0123456789");
  if (n + 1 != length) {
    return -1;
  }
  // Read out ASN1 year, in either 2-char "UTCTIME" or 4-char "GENERALIZEDTIME"
  // format.  Both format use UTC in this context.
  int year = 0;
  if (long_format) {
    // ASN1 format: yyyymmddhh[mm[ss[.fff]]]Z where the Z is literal, but
    // RFC 5280 requires us to only support exactly yyyymmddhhmmssZ.
    if (bytes_left < 11) {
      return -1;
    }
    year = ASN1ReadInt(&s, &bytes_left, 4);
    year -= 1900;
  } else {
    // ASN1 format: yymmddhhmm[ss]Z where the Z is literal, but RFC 5280
    // requires us to only support exactly yymmddhhmmssZ.
    if (bytes_left < 9) {
      return -1;
    }
    year = ASN1ReadInt(&s, &bytes_left, 2);
    // Per RFC 5280 4.1.2.5.1
    if (year < 50) {
      year += 100;
    }
  }

  // Read out remaining ASN1 time data and store it in `tm` in documented
  // std::tm format.
  tm tm;
  tm.tm_year = year;
  tm.tm_mon = ASN1ReadInt(&s, &bytes_left, 2) - 1;
  tm.tm_mday = ASN1ReadInt(&s, &bytes_left, 2);
  tm.tm_hour = ASN1ReadInt(&s, &bytes_left, 2);
  tm.tm_min = ASN1ReadInt(&s, &bytes_left, 2);
  tm.tm_sec = ASN1ReadInt(&s, &bytes_left, 2);

  // Now just Z should remain.  Its existence was asserted above.
  if (bytes_left != 1) {
    return -1;
  }
  return TmToSeconds(tm);
}

//////////////////////////////////////////////////////////////////////
// KeyParams
//////////////////////////////////////////////////////////////////////

const char kPemTypeCertificate[] = "CERTIFICATE";
const char kPemTypeRsaPrivateKey[] = "RSA PRIVATE KEY";
const char kPemTypeEcPrivateKey[] = "EC PRIVATE KEY";

KeyParams::KeyParams(KeyType key_type) {
  if (key_type == KT_ECDSA) {
    type_ = KT_ECDSA;
    params_.curve = EC_NIST_P256;
  } else if (key_type == KT_RSA) {
    type_ = KT_RSA;
    params_.rsa.mod_size = kRsaDefaultModSize;
    params_.rsa.pub_exp = kRsaDefaultExponent;
  } else {
    RTC_DCHECK_NOTREACHED();
  }
}

// static
KeyParams KeyParams::RSA(int mod_size, int pub_exp) {
  KeyParams kt(KT_RSA);
  kt.params_.rsa.mod_size = mod_size;
  kt.params_.rsa.pub_exp = pub_exp;
  return kt;
}

// static
KeyParams KeyParams::ECDSA(ECCurve curve) {
  KeyParams kt(KT_ECDSA);
  kt.params_.curve = curve;
  return kt;
}

bool KeyParams::IsValid() const {
  if (type_ == KT_RSA) {
    return (params_.rsa.mod_size >= kRsaMinModSize &&
            params_.rsa.mod_size <= kRsaMaxModSize &&
            params_.rsa.pub_exp > params_.rsa.mod_size);
  } else if (type_ == KT_ECDSA) {
    return (params_.curve == EC_NIST_P256);
  }
  return false;
}

RSAParams KeyParams::rsa_params() const {
  RTC_DCHECK(type_ == KT_RSA);
  return params_.rsa;
}

ECCurve KeyParams::ec_curve() const {
  RTC_DCHECK(type_ == KT_ECDSA);
  return params_.curve;
}

//////////////////////////////////////////////////////////////////////
// SSLIdentity
//////////////////////////////////////////////////////////////////////

bool SSLIdentity::PemToDer(absl::string_view pem_type,
                           absl::string_view pem_string,
                           std::string* der) {
  // Find the inner body. We need this to fulfill the contract of returning
  // pem_length.
  std::string pem_type_str(pem_type);
  size_t header = pem_string.find("-----BEGIN " + pem_type_str + "-----");
  if (header == absl::string_view::npos) {
    return false;
  }
  size_t body = pem_string.find('\n', header);
  if (body == absl::string_view::npos) {
    return false;
  }
  size_t trailer = pem_string.find("-----END " + pem_type_str + "-----");
  if (trailer == absl::string_view::npos) {
    return false;
  }
  std::string inner(pem_string.substr(body + 1, trailer - (body + 1)));
  std::optional<std::string> decoded =
      Base64Decode(inner, Base64DecodeOptions::kForgiving);
  if (!decoded.has_value()) {
    return false;
  }
  *der = std::move(*decoded);
  return true;
}

std::string SSLIdentity::DerToPem(absl::string_view pem_type,
                                  const unsigned char* data,
                                  size_t length) {
  StringBuilder result;
  result << "-----BEGIN " << pem_type << "-----\n";

  ArrayView<const uint8_t> data_view(data, length);
  std::string b64_encoded = Base64Encode(data_view);
  // Divide the Base-64 encoded data into 64-character chunks, as per 4.3.2.4
  // of RFC 1421.
  static const size_t kChunkSize = 64;
  size_t chunks = (b64_encoded.size() + (kChunkSize - 1)) / kChunkSize;
  for (size_t i = 0, chunk_offset = 0; i < chunks;
       ++i, chunk_offset += kChunkSize) {
    result << b64_encoded.substr(chunk_offset, kChunkSize);
    result << "\n";
  }
  result << "-----END " << pem_type << "-----\n";
  return result.Release();
}

// static
std::unique_ptr<SSLIdentity> SSLIdentity::Create(absl::string_view common_name,
                                                 const KeyParams& key_param,
                                                 time_t certificate_lifetime) {
#ifdef OPENSSL_IS_BORINGSSL
  return BoringSSLIdentity::CreateWithExpiration(common_name, key_param,
                                                 certificate_lifetime);
#else
  return OpenSSLIdentity::CreateWithExpiration(common_name, key_param,
                                               certificate_lifetime);
#endif
}

// static
std::unique_ptr<SSLIdentity> SSLIdentity::Create(absl::string_view common_name,
                                                 const KeyParams& key_param) {
  return Create(common_name, key_param, kDefaultCertificateLifetimeInSeconds);
}

// static
std::unique_ptr<SSLIdentity> SSLIdentity::Create(absl::string_view common_name,
                                                 KeyType key_type) {
  return Create(common_name, KeyParams(key_type),
                kDefaultCertificateLifetimeInSeconds);
}

//  static
std::unique_ptr<SSLIdentity> SSLIdentity::CreateForTest(
    const SSLIdentityParams& params) {
#ifdef OPENSSL_IS_BORINGSSL
  return BoringSSLIdentity::CreateForTest(params);
#else
  return OpenSSLIdentity::CreateForTest(params);
#endif
}

// Construct an identity from a private key and a certificate.
// static
std::unique_ptr<SSLIdentity> SSLIdentity::CreateFromPEMStrings(
    absl::string_view private_key,
    absl::string_view certificate) {
#ifdef OPENSSL_IS_BORINGSSL
  return BoringSSLIdentity::CreateFromPEMStrings(private_key, certificate);
#else
  return OpenSSLIdentity::CreateFromPEMStrings(private_key, certificate);
#endif
}

// Construct an identity from a private key and a certificate chain.
// static
std::unique_ptr<SSLIdentity> SSLIdentity::CreateFromPEMChainStrings(
    absl::string_view private_key,
    absl::string_view certificate_chain) {
#ifdef OPENSSL_IS_BORINGSSL
  return BoringSSLIdentity::CreateFromPEMChainStrings(private_key,
                                                      certificate_chain);
#else
  return OpenSSLIdentity::CreateFromPEMChainStrings(private_key,
                                                    certificate_chain);
#endif
}

bool operator==(const SSLIdentity& a, const SSLIdentity& b) {
#ifdef OPENSSL_IS_BORINGSSL
  return static_cast<const BoringSSLIdentity&>(a) ==
         static_cast<const BoringSSLIdentity&>(b);
#else
  return static_cast<const OpenSSLIdentity&>(a) ==
         static_cast<const OpenSSLIdentity&>(b);
#endif
}
bool operator!=(const SSLIdentity& a, const SSLIdentity& b) {
  return !(a == b);
}

}  // namespace webrtc