crypto/scoped_fake_user_verifying_key_provider.cc

// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "crypto/scoped_fake_user_verifying_key_provider.h"

#include <memory>
#include <utility>
#include <vector>

#include "base/base64.h"
#include "base/containers/flat_map.h"
#include "base/containers/span.h"
#include "base/functional/bind.h"
#include "base/functional/callback.h"
#include "base/functional/callback_helpers.h"
#include "base/no_destructor.h"
#include "crypto/signature_verifier.h"
#include "crypto/unexportable_key.h"
#include "crypto/user_verifying_key.h"

namespace crypto {

namespace {

// The vector of deleted keys needs to be shared between instances of
// FakeUserVerifyingKeyProvider - in production the keys all live in a shared
// key store, so deleting a key via one provider should show up in any other
// providers as well.
std::vector<UserVerifyingKeyLabel>& GetDeletedKeys() {
  static base::NoDestructor<std::vector<UserVerifyingKeyLabel>> s_labels;
  return *s_labels;
}

// When true, fake UV signing keys indicate that they are hardware backed.
bool g_fake_hardware_backing_ = false;

// Wraps a software `UnexportableSigningKey`.
class FakeUserVerifyingSigningKey : public UserVerifyingSigningKey {
 public:
  FakeUserVerifyingSigningKey(
      UserVerifyingKeyLabel label,
      std::unique_ptr<UnexportableSigningKey> software_key)
      : label_(std::move(label)), software_key_(std::move(software_key)) {}

  ~FakeUserVerifyingSigningKey() override = default;

  void Sign(base::span<const uint8_t> data,
            UserVerifyingKeySignatureCallback callback) override {
    auto opt_signature = software_key_->SignSlowly(data);
    if (!opt_signature.has_value()) {
      std::move(callback).Run(
          base::unexpected(UserVerifyingKeySigningError::kUnknownError));
      return;
    }
    std::move(callback).Run(base::ok(*opt_signature));
  }

  std::vector<uint8_t> GetPublicKey() const override {
    return software_key_->GetSubjectPublicKeyInfo();
  }

  const UserVerifyingKeyLabel& GetKeyLabel() const override { return label_; }

  bool IsHardwareBacked() const override { return g_fake_hardware_backing_; }

 private:
  const UserVerifyingKeyLabel label_;
  std::unique_ptr<UnexportableSigningKey> software_key_;
};

class FakeUserVerifyingKeyProvider : public UserVerifyingKeyProvider {
 public:
  ~FakeUserVerifyingKeyProvider() override = default;

  void GenerateUserVerifyingSigningKey(
      base::span<const SignatureVerifier::SignatureAlgorithm>
          acceptable_algorithms,
      UserVerifyingKeyCreationCallback callback) override {
    auto software_unexportable_key =
        GetSoftwareUnsecureUnexportableKeyProvider()->GenerateSigningKeySlowly(
            acceptable_algorithms);
    UserVerifyingKeyLabel key_label =
        base::Base64Encode(software_unexportable_key->GetWrappedKey());
    std::move(callback).Run(std::make_unique<FakeUserVerifyingSigningKey>(
        std::move(key_label), std::move(software_unexportable_key)));
  }

  void GetUserVerifyingSigningKey(
      UserVerifyingKeyLabel key_label,
      UserVerifyingKeyCreationCallback callback) override {
    for (auto deleted_key : GetDeletedKeys()) {
      if (deleted_key == key_label) {
        std::move(callback).Run(
            base::unexpected(UserVerifyingKeyCreationError::kUnknownError));
        return;
      }
    }
    std::vector<SignatureVerifier::SignatureAlgorithm> algorithms = {
        SignatureVerifier::SignatureAlgorithm::ECDSA_SHA256};
    std::optional<std::vector<uint8_t>> wrapped_key =
        base::Base64Decode(key_label);
    CHECK(wrapped_key);
    auto software_unexportable_key =
        GetSoftwareUnsecureUnexportableKeyProvider()
            ->FromWrappedSigningKeySlowly(*wrapped_key);
    CHECK(software_unexportable_key);
    std::move(callback).Run(
        base::ok(std::make_unique<FakeUserVerifyingSigningKey>(
            std::move(key_label), std::move(software_unexportable_key))));
  }

  void DeleteUserVerifyingKey(
      UserVerifyingKeyLabel key_label,
      base::OnceCallback<void(bool)> callback) override {
    GetDeletedKeys().push_back(key_label);
    std::move(callback).Run(true);
  }
};

class FailingUserVerifyingSigningKey : public UserVerifyingSigningKey {
 public:
  FailingUserVerifyingSigningKey() : label_("test") {}
  ~FailingUserVerifyingSigningKey() override = default;

  void Sign(base::span<const uint8_t> data,
            UserVerifyingKeySignatureCallback callback) override {
    std::move(callback).Run(
        base::unexpected(UserVerifyingKeySigningError::kUnknownError));
  }

  std::vector<uint8_t> GetPublicKey() const override { return {1, 2, 3, 4}; }

  const UserVerifyingKeyLabel& GetKeyLabel() const override { return label_; }

 private:
  const UserVerifyingKeyLabel label_;
};

class FailingUserVerifyingKeyProvider : public UserVerifyingKeyProvider {
 public:
  ~FailingUserVerifyingKeyProvider() override = default;

  void GenerateUserVerifyingSigningKey(
      base::span<const SignatureVerifier::SignatureAlgorithm>
          acceptable_algorithms,
      UserVerifyingKeyCreationCallback callback) override {
    std::move(callback).Run(
        base::ok(std::make_unique<FailingUserVerifyingSigningKey>()));
  }

  void GetUserVerifyingSigningKey(
      UserVerifyingKeyLabel key_label,
      UserVerifyingKeyCreationCallback callback) override {
    std::move(callback).Run(
        base::ok(std::make_unique<FailingUserVerifyingSigningKey>()));
  }

  void DeleteUserVerifyingKey(
      UserVerifyingKeyLabel key_label,
      base::OnceCallback<void(bool)> callback) override {}
};

std::unique_ptr<UserVerifyingKeyProvider> GetMockUserVerifyingKeyProvider() {
  return std::make_unique<FakeUserVerifyingKeyProvider>();
}

std::unique_ptr<UserVerifyingKeyProvider> GetNullUserVerifyingKeyProvider() {
  return nullptr;
}

std::unique_ptr<UserVerifyingKeyProvider> GetFailingUserVerifyingKeyProvider() {
  return std::make_unique<FailingUserVerifyingKeyProvider>();
}

}  // namespace

ScopedFakeUserVerifyingKeyProvider::ScopedFakeUserVerifyingKeyProvider(
    bool fake_hardware_backing) {
  g_fake_hardware_backing_ = fake_hardware_backing;
  internal::SetUserVerifyingKeyProviderForTesting(
      GetMockUserVerifyingKeyProvider);
}

ScopedFakeUserVerifyingKeyProvider::~ScopedFakeUserVerifyingKeyProvider() {
  g_fake_hardware_backing_ = false;
  internal::SetUserVerifyingKeyProviderForTesting(nullptr);
}

ScopedNullUserVerifyingKeyProvider::ScopedNullUserVerifyingKeyProvider() {
  internal::SetUserVerifyingKeyProviderForTesting(
      GetNullUserVerifyingKeyProvider);
}

ScopedNullUserVerifyingKeyProvider::~ScopedNullUserVerifyingKeyProvider() {
  internal::SetUserVerifyingKeyProviderForTesting(nullptr);
}

ScopedFailingUserVerifyingKeyProvider::ScopedFailingUserVerifyingKeyProvider() {
  internal::SetUserVerifyingKeyProviderForTesting(
      GetFailingUserVerifyingKeyProvider);
}

ScopedFailingUserVerifyingKeyProvider::
    ~ScopedFailingUserVerifyingKeyProvider() {
  internal::SetUserVerifyingKeyProviderForTesting(nullptr);
}

ScopedUserVerifyingKeysSupportedOverride::
    ScopedUserVerifyingKeysSupportedOverride(
        UserVerifyingKeysSupportedOverride override) {
  internal::SetUserVerifyingKeysSupportedOverrideForTesting(
      std::move(override));
}

ScopedUserVerifyingKeysSupportedOverride::
    ~ScopedUserVerifyingKeysSupportedOverride() {
  internal::SetUserVerifyingKeysSupportedOverrideForTesting(
      base::NullCallback());
}

}  // namespace crypto