// Copyright 2017 Google Inc.
//
// 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 "tink/signature/public_key_verify_wrapper.h"

#include <memory>
#include <string>
#include <utility>

#include "absl/status/status.h"
#include "absl/strings/str_cat.h"
#include "tink/crypto_format.h"
#include "tink/internal/monitoring_util.h"
#include "tink/internal/registry_impl.h"
#include "tink/internal/util.h"
#include "tink/monitoring/monitoring.h"
#include "tink/primitive_set.h"
#include "tink/public_key_verify.h"
#include "tink/util/status.h"
#include "tink/util/statusor.h"
#include "proto/tink.pb.h"

namespace crypto {
namespace tink {

namespace {

constexpr absl::string_view kPrimitive = "public_key_verify";
constexpr absl::string_view kVerifyApi = "verify";

using ::google::crypto::tink::OutputPrefixType;

util::Status Validate(PrimitiveSet<PublicKeyVerify>* public_key_verify_set) {
  if (public_key_verify_set == nullptr) {
    return util::Status(absl::StatusCode::kInternal,
                        "public_key_verify_set must be non-NULL");
  }
  if (public_key_verify_set->get_primary() == nullptr) {
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "public_key_verify_set has no primary");
  }
  return util::OkStatus();
}

class PublicKeyVerifySetWrapper : public PublicKeyVerify {
 public:
  explicit PublicKeyVerifySetWrapper(
      std::unique_ptr<PrimitiveSet<PublicKeyVerify>> public_key_verify_set,
      std::unique_ptr<MonitoringClient> monitoring_verify_client = nullptr)
      : public_key_verify_set_(std::move(public_key_verify_set)),
      monitoring_verify_client_(std::move(monitoring_verify_client)) {}

  crypto::tink::util::Status Verify(absl::string_view signature,
                                    absl::string_view data) const override;

  ~PublicKeyVerifySetWrapper() override = default;

 private:
  std::unique_ptr<PrimitiveSet<PublicKeyVerify>> public_key_verify_set_;
  std::unique_ptr<MonitoringClient> monitoring_verify_client_;
};

util::Status PublicKeyVerifySetWrapper::Verify(absl::string_view signature,
                                               absl::string_view data) const {
  // BoringSSL expects a non-null pointer for data,
  // regardless of whether the size is 0.
  data = internal::EnsureStringNonNull(data);
  signature = internal::EnsureStringNonNull(signature);

  if (signature.length() <= CryptoFormat::kNonRawPrefixSize) {
    // This also rejects raw signatures with size of 4 bytes or fewer.
    // We're not aware of any schemes that output signatures that small.
    return util::Status(absl::StatusCode::kInvalidArgument,
                        "Signature too short.");
  }
  absl::string_view key_id =
      signature.substr(0, CryptoFormat::kNonRawPrefixSize);
  auto primitives_result = public_key_verify_set_->get_primitives(key_id);
  if (primitives_result.ok()) {
    absl::string_view raw_signature =
        signature.substr(CryptoFormat::kNonRawPrefixSize);
    for (auto& entry : *(primitives_result.value())) {
      std::string legacy_data;
      absl::string_view view_on_data_or_legacy_data = data;
      if (entry->get_output_prefix_type() == OutputPrefixType::LEGACY) {
        legacy_data = absl::StrCat(data, std::string("\x00", 1));
        view_on_data_or_legacy_data = legacy_data;
      }
      auto& public_key_verify = entry->get_primitive();
      auto verify_result =
          public_key_verify.Verify(raw_signature, view_on_data_or_legacy_data);
      if (verify_result.ok()) {
        if (monitoring_verify_client_ != nullptr) {
          monitoring_verify_client_->Log(entry->get_key_id(), data.size());
        }
        return util::OkStatus();
      } else {
        // LOG that a matching key didn't verify the signature.
      }
    }
  }

  // No matching key succeeded with verification, try all RAW keys.
  auto raw_primitives_result = public_key_verify_set_->get_raw_primitives();
  if (raw_primitives_result.ok()) {
    for (auto& public_key_verify_entry : *(raw_primitives_result.value())) {
      auto& public_key_verify = public_key_verify_entry->get_primitive();
      auto verify_result = public_key_verify.Verify(signature, data);
      if (verify_result.ok()) {
        if (monitoring_verify_client_ != nullptr) {
          monitoring_verify_client_->Log(public_key_verify_entry->get_key_id(),
                                         data.size());
        }
        return util::OkStatus();
      }
    }
  }
  if (monitoring_verify_client_ != nullptr) {
    monitoring_verify_client_->LogFailure();
  }
  return util::Status(absl::StatusCode::kInvalidArgument, "Invalid signature.");
}

}  // anonymous namespace

util::StatusOr<std::unique_ptr<PublicKeyVerify>> PublicKeyVerifyWrapper::Wrap(
    std::unique_ptr<PrimitiveSet<PublicKeyVerify>> public_key_verify_set)
    const {
  util::Status status = Validate(public_key_verify_set.get());
  if (!status.ok()) return status;

  MonitoringClientFactory* const monitoring_factory =
      internal::RegistryImpl::GlobalInstance().GetMonitoringClientFactory();

  // Monitoring is not enabled. Create a wrapper without monitoring clients.
  if (monitoring_factory == nullptr) {
    return {absl::make_unique<PublicKeyVerifySetWrapper>(
        std::move(public_key_verify_set))};
  }

  util::StatusOr<MonitoringKeySetInfo> keyset_info =
      internal::MonitoringKeySetInfoFromPrimitiveSet(*public_key_verify_set);
  if (!keyset_info.ok()) {
    return keyset_info.status();
  }

  util::StatusOr<std::unique_ptr<MonitoringClient>> monitoring_verify_client =
      monitoring_factory->New(
          MonitoringContext(kPrimitive, kVerifyApi, *keyset_info));
  if (!monitoring_verify_client.ok()) {
    return monitoring_verify_client.status();
  }

  return {absl::make_unique<PublicKeyVerifySetWrapper>(
      std::move(public_key_verify_set), *std::move(monitoring_verify_client))};
}

}  // namespace tink
}  // namespace crypto