// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/browser/chromeos/attestation/platform_verification_flow.h"

#include "base/command_line.h"
#include "base/logging.h"
#include "base/message_loop/message_loop.h"
#include "base/metrics/histogram.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "chrome/browser/chromeos/attestation/attestation_ca_client.h"
#include "chrome/browser/chromeos/attestation/attestation_signed_data.pb.h"
#include "chrome/browser/chromeos/profiles/profile_helper.h"
#include "chrome/browser/chromeos/settings/cros_settings.h"
#include "chrome/browser/media/protected_media_identifier_permission_context.h"
#include "chrome/browser/media/protected_media_identifier_permission_context_factory.h"
#include "chrome/browser/profiles/profile.h"
#include "chromeos/attestation/attestation_flow.h"
#include "chromeos/chromeos_switches.h"
#include "chromeos/cryptohome/async_method_caller.h"
#include "chromeos/dbus/cryptohome_client.h"
#include "chromeos/dbus/dbus_thread_manager.h"
#include "components/content_settings/core/browser/host_content_settings_map.h"
#include "components/content_settings/core/common/content_settings_pattern.h"
#include "components/user_manager/user.h"
#include "content/public/browser/browser_context.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/render_process_host.h"
#include "content/public/browser/render_view_host.h"
#include "content/public/browser/user_metrics.h"
#include "content/public/browser/web_contents.h"
#include "content/public/common/url_constants.h"
#include "net/cert/x509_certificate.h"

namespace {

const int kTimeoutInSeconds = 8;
const char kAttestationResultHistogram[] =
    "ChromeOS.PlatformVerification.Result";
const char kAttestationAvailableHistogram[] =
    "ChromeOS.PlatformVerification.Available";
const int kAttestationResultHistogramMax = 10;

// A callback method to handle DBus errors.
void DBusCallback(const base::Callback<void(bool)>& on_success,
                  const base::Closure& on_failure,
                  chromeos::DBusMethodCallStatus call_status,
                  bool result) {
  if (call_status == chromeos::DBUS_METHOD_CALL_SUCCESS) {
    on_success.Run(result);
  } else {
    LOG(ERROR) << "PlatformVerificationFlow: DBus call failed!";
    on_failure.Run();
  }
}

// A helper to call a ChallengeCallback with an error result.
void ReportError(
    const chromeos::attestation::PlatformVerificationFlow::ChallengeCallback&
        callback,
    chromeos::attestation::PlatformVerificationFlow::Result error) {
  UMA_HISTOGRAM_ENUMERATION(kAttestationResultHistogram, error,
                            kAttestationResultHistogramMax);
  callback.Run(error, std::string(), std::string(), std::string());
}
}  // namespace

namespace chromeos {
namespace attestation {

// A default implementation of the Delegate interface.
class DefaultDelegate : public PlatformVerificationFlow::Delegate {
 public:
  DefaultDelegate() {}
  ~DefaultDelegate() override {}

  const GURL& GetURL(content::WebContents* web_contents) override {
    const GURL& url = web_contents->GetLastCommittedURL();
    if (!url.is_valid())
      return web_contents->GetVisibleURL();
    return url;
  }

  const user_manager::User* GetUser(
      content::WebContents* web_contents) override {
    return ProfileHelper::Get()->GetUserByProfile(
        Profile::FromBrowserContext(web_contents->GetBrowserContext()));
  }

  bool IsPermittedByUser(content::WebContents* web_contents) override {
    ProtectedMediaIdentifierPermissionContext* permission_context =
        ProtectedMediaIdentifierPermissionContextFactory::GetForProfile(
            Profile::FromBrowserContext(web_contents->GetBrowserContext()));

    // TODO(xhwang): Using delegate_->GetURL() here is not right. The platform
    // verification may be requested by a frame from a different origin. This
    // will be solved when http://crbug.com/454847 is fixed.
    const GURL& requesting_origin = GetURL(web_contents).GetOrigin();

    GURL embedding_origin = web_contents->GetLastCommittedURL().GetOrigin();

    ContentSetting content_setting = permission_context->GetPermissionStatus(
        requesting_origin, embedding_origin);

    return content_setting == CONTENT_SETTING_ALLOW;
  }

  bool IsInSupportedMode(content::WebContents* web_contents) override {
    Profile* profile =
        Profile::FromBrowserContext(web_contents->GetBrowserContext());
    if (profile->IsOffTheRecord() || profile->IsGuestSession())
      return false;

    base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
    return !command_line->HasSwitch(chromeos::switches::kSystemDevMode) ||
           command_line->HasSwitch(chromeos::switches::kAllowRAInDevMode);
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(DefaultDelegate);
};

PlatformVerificationFlow::ChallengeContext::ChallengeContext(
    content::WebContents* web_contents,
    const std::string& service_id,
    const std::string& challenge,
    const ChallengeCallback& callback)
    : web_contents(web_contents),
      service_id(service_id),
      challenge(challenge),
      callback(callback) {}

PlatformVerificationFlow::ChallengeContext::~ChallengeContext() {}

PlatformVerificationFlow::PlatformVerificationFlow()
    : attestation_flow_(NULL),
      async_caller_(cryptohome::AsyncMethodCaller::GetInstance()),
      cryptohome_client_(DBusThreadManager::Get()->GetCryptohomeClient()),
      delegate_(NULL),
      timeout_delay_(base::TimeDelta::FromSeconds(kTimeoutInSeconds)) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  scoped_ptr<ServerProxy> attestation_ca_client(new AttestationCAClient());
  default_attestation_flow_.reset(new AttestationFlow(
      async_caller_,
      cryptohome_client_,
      attestation_ca_client.Pass()));
  attestation_flow_ = default_attestation_flow_.get();
  default_delegate_.reset(new DefaultDelegate());
  delegate_ = default_delegate_.get();
}

PlatformVerificationFlow::PlatformVerificationFlow(
    AttestationFlow* attestation_flow,
    cryptohome::AsyncMethodCaller* async_caller,
    CryptohomeClient* cryptohome_client,
    Delegate* delegate)
    : attestation_flow_(attestation_flow),
      async_caller_(async_caller),
      cryptohome_client_(cryptohome_client),
      delegate_(delegate),
      timeout_delay_(base::TimeDelta::FromSeconds(kTimeoutInSeconds)) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (!delegate_) {
    default_delegate_.reset(new DefaultDelegate());
    delegate_ = default_delegate_.get();
  }
}

PlatformVerificationFlow::~PlatformVerificationFlow() {
}

void PlatformVerificationFlow::ChallengePlatformKey(
    content::WebContents* web_contents,
    const std::string& service_id,
    const std::string& challenge,
    const ChallengeCallback& callback) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);

  if (!delegate_->GetURL(web_contents).is_valid()) {
    LOG(WARNING) << "PlatformVerificationFlow: Invalid URL.";
    ReportError(callback, INTERNAL_ERROR);
    return;
  }

  // Note: The following two checks are also checked in GetPermissionStatus.
  // Checking them here explicitly to report the correct error type.

  if (!IsAttestationAllowedByPolicy()) {
    VLOG(1) << "Platform verification not allowed by device policy.";
    ReportError(callback, POLICY_REJECTED);
    return;
  }

  // TODO(xhwang): Change to DCHECK when prefixed EME support is removed.
  // See http://crbug.com/249976
  if (!delegate_->IsInSupportedMode(web_contents)) {
    VLOG(1) << "Platform verification denied because it's not supported in the "
            << "current mode.";
    ReportError(callback, PLATFORM_NOT_VERIFIED);
    return;
  }

  if (!delegate_->IsPermittedByUser(web_contents)) {
    VLOG(1) << "Platform verification not permitted by user.";
    ReportError(callback, USER_REJECTED);
    return;
  }

  ChallengeContext context(web_contents, service_id, challenge, callback);
  // Check if the device has been prepared to use attestation.
  BoolDBusMethodCallback dbus_callback =
      base::Bind(&DBusCallback,
                 base::Bind(&PlatformVerificationFlow::OnAttestationPrepared,
                            this, context),
                 base::Bind(&ReportError, callback, INTERNAL_ERROR));
  cryptohome_client_->TpmAttestationIsPrepared(dbus_callback);
}

void PlatformVerificationFlow::OnAttestationPrepared(
    const ChallengeContext& context,
    bool attestation_prepared) {
  UMA_HISTOGRAM_BOOLEAN(kAttestationAvailableHistogram, attestation_prepared);

  if (!attestation_prepared) {
    // This device is not currently able to use attestation features.
    ReportError(context.callback, PLATFORM_NOT_VERIFIED);
    return;
  }

  // Permission allowed. Now proceed to get certificate.
  const user_manager::User* user = delegate_->GetUser(context.web_contents);
  if (!user) {
    ReportError(context.callback, INTERNAL_ERROR);
    LOG(ERROR) << "Profile does not map to a valid user.";
    return;
  }

  GetCertificate(context, user->email(), false /* Don't force a new key */);
}

void PlatformVerificationFlow::GetCertificate(const ChallengeContext& context,
                                              const std::string& user_id,
                                              bool force_new_key) {
  scoped_ptr<base::Timer> timer(new base::Timer(false,    // Don't retain.
                                                false));  // Don't repeat.
  base::Closure timeout_callback = base::Bind(
      &PlatformVerificationFlow::OnCertificateTimeout,
      this,
      context);
  timer->Start(FROM_HERE, timeout_delay_, timeout_callback);

  AttestationFlow::CertificateCallback certificate_callback = base::Bind(
      &PlatformVerificationFlow::OnCertificateReady,
      this,
      context,
      user_id,
      base::Passed(&timer));
  attestation_flow_->GetCertificate(
      PROFILE_CONTENT_PROTECTION_CERTIFICATE,
      user_id,
      context.service_id,
      force_new_key,
      certificate_callback);
}

void PlatformVerificationFlow::OnCertificateReady(
    const ChallengeContext& context,
    const std::string& user_id,
    scoped_ptr<base::Timer> timer,
    bool operation_success,
    const std::string& certificate) {
  // Log failure before checking the timer so all failures are logged, even if
  // they took too long.
  if (!operation_success) {
    LOG(WARNING) << "PlatformVerificationFlow: Failed to certify platform.";
  }
  if (!timer->IsRunning()) {
    LOG(WARNING) << "PlatformVerificationFlow: Certificate ready but call has "
                 << "already timed out.";
    return;
  }
  timer->Stop();
  if (!operation_success) {
    ReportError(context.callback, PLATFORM_NOT_VERIFIED);
    return;
  }
  if (IsExpired(certificate)) {
    GetCertificate(context, user_id, true /* Force a new key */);
    return;
  }
  cryptohome::AsyncMethodCaller::DataCallback cryptohome_callback = base::Bind(
      &PlatformVerificationFlow::OnChallengeReady,
      this,
      context,
      certificate);
  std::string key_name = kContentProtectionKeyPrefix;
  key_name += context.service_id;
  async_caller_->TpmAttestationSignSimpleChallenge(KEY_USER,
                                                   user_id,
                                                   key_name,
                                                   context.challenge,
                                                   cryptohome_callback);
}

void PlatformVerificationFlow::OnCertificateTimeout(
    const ChallengeContext& context) {
  LOG(WARNING) << "PlatformVerificationFlow: Timing out.";
  ReportError(context.callback, TIMEOUT);
}

void PlatformVerificationFlow::OnChallengeReady(
    const ChallengeContext& context,
    const std::string& certificate,
    bool operation_success,
    const std::string& response_data) {
  if (!operation_success) {
    LOG(ERROR) << "PlatformVerificationFlow: Failed to sign challenge.";
    ReportError(context.callback, INTERNAL_ERROR);
    return;
  }
  SignedData signed_data_pb;
  if (response_data.empty() || !signed_data_pb.ParseFromString(response_data)) {
    LOG(ERROR) << "PlatformVerificationFlow: Failed to parse response data.";
    ReportError(context.callback, INTERNAL_ERROR);
    return;
  }
  VLOG(1) << "Platform verification successful.";
  UMA_HISTOGRAM_ENUMERATION(kAttestationResultHistogram, SUCCESS,
                            kAttestationResultHistogramMax);
  context.callback.Run(SUCCESS,
                       signed_data_pb.data(),
                       signed_data_pb.signature(),
                       certificate);
}

bool PlatformVerificationFlow::IsAttestationAllowedByPolicy() {
  // Check the device policy for the feature.
  bool enabled_for_device = false;
  if (!CrosSettings::Get()->GetBoolean(kAttestationForContentProtectionEnabled,
                                       &enabled_for_device)) {
    LOG(ERROR) << "Failed to get device setting.";
    return false;
  }
  if (!enabled_for_device) {
    VLOG(1) << "Platform verification denied because Verified Access is "
            << "disabled for the device.";
    return false;
  }

  return true;
}

bool PlatformVerificationFlow::IsExpired(const std::string& certificate) {
  scoped_refptr<net::X509Certificate> x509(
      net::X509Certificate::CreateFromBytes(certificate.data(),
                                            certificate.length()));
  if (!x509.get() || x509->valid_expiry().is_null()) {
    LOG(WARNING) << "Failed to parse certificate, cannot check expiry.";
    return false;
  }
  return (base::Time::Now() > x509->valid_expiry());
}

}  // namespace attestation
}  // namespace chromeos