cryptohome/tpm_bound_to_pcr_auth_block.cc - mirrors/cros/chromiumos/platform2 - Git at Google

 // Copyright 2020 The Chromium OS 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 "cryptohome/tpm_bound_to_pcr_auth_block.h"

 #include <map>
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>

 #include <base/check.h>
 #include <base/logging.h>
 #include <base/optional.h>
 #include <brillo/secure_blob.h>

 #include "cryptohome/crypto.h"
 #include "cryptohome/crypto/aes.h"
 #include "cryptohome/crypto/scrypt.h"
 #include "cryptohome/crypto/secure_blob_util.h"
 #include "cryptohome/crypto_error.h"
 #include "cryptohome/cryptohome_keys_manager.h"
 #include "cryptohome/cryptohome_metrics.h"
 #include "cryptohome/tpm.h"
 #include "cryptohome/tpm_auth_block_utils.h"
 #include "cryptohome/vault_keyset.pb.h"

 using hwsec::error::TPMError;
 using hwsec::error::TPMErrorBase;
 using hwsec_foundation::error::CreateErrorWrap;

 namespace cryptohome {

 TpmBoundToPcrAuthBlock::TpmBoundToPcrAuthBlock(
     Tpm* tpm, CryptohomeKeysManager* cryptohome_keys_manager)
     : AuthBlock(kTpmBackedPcrBound),
       tpm_(tpm),
       cryptohome_key_loader_(
           cryptohome_keys_manager->GetKeyLoader(CryptohomeKeyType::kRSA)),
       utils_(tpm, cryptohome_key_loader_) {
   CHECK(tpm != nullptr);
   CHECK(cryptohome_key_loader_ != nullptr);

   // Create the scrypt thread.
   // TODO(yich): Create another thread in userdataauth and passing it to here.
   base::Thread::Options options;
   options.message_pump_type = base::MessagePumpType::IO;
   scrypt_thread_ = std::make_unique<base::Thread>("scrypt_thread");
   scrypt_thread_->StartWithOptions(options);
   scrypt_task_runner_ = scrypt_thread_->task_runner();
 }

 base::Optional<AuthBlockState> TpmBoundToPcrAuthBlock::Create(
     const AuthInput& user_input, KeyBlobs* key_blobs, CryptoError* error) {
   const brillo::SecureBlob& vault_key = user_input.user_input.value();
   const brillo::SecureBlob& salt = user_input.salt.value();
   const std::string& obfuscated_username =
       user_input.obfuscated_username.value();

   // If the cryptohome key isn't loaded, try to load it.
   if (!cryptohome_key_loader_->HasCryptohomeKey())
     cryptohome_key_loader_->Init();

   // If the key still isn't loaded, fail the operation.
   if (!cryptohome_key_loader_->HasCryptohomeKey())
     return base::nullopt;

   const auto vkk_key = CreateSecureRandomBlob(kDefaultAesKeySize);
   brillo::SecureBlob pass_blob(kDefaultPassBlobSize);
   brillo::SecureBlob vkk_iv(kAesBlockSize);
   if (!DeriveSecretsScrypt(vault_key, salt, {&pass_blob, &vkk_iv}))
     return base::nullopt;

   std::map<uint32_t, std::string> default_pcr_map =
       tpm_->GetPcrMap(obfuscated_username, false /* use_extended_pcr */);
   std::map<uint32_t, std::string> extended_pcr_map =
       tpm_->GetPcrMap(obfuscated_username, true /* use_extended_pcr */);

   // Encrypt the VKK using the TPM and the user's passkey. The output is two
   // encrypted blobs, sealed to PCR in |tpm_key| and |extended_tpm_key|,
   // which are stored in the serialized vault keyset.
   TpmKeyHandle cryptohome_key = cryptohome_key_loader_->GetCryptohomeKey();
   brillo::SecureBlob auth_value;
   if (TPMErrorBase err =
           tpm_->GetAuthValue(cryptohome_key, pass_blob, &auth_value)) {
     LOG(ERROR) << "Failed to get auth value: " << *err;
     return base::nullopt;
   }

   brillo::SecureBlob tpm_key;
   if (TPMErrorBase err = tpm_->SealToPcrWithAuthorization(
           vkk_key, auth_value, default_pcr_map, &tpm_key)) {
     LOG(ERROR) << "Failed to wrap vkk with creds: " << *err;
     return base::nullopt;
   }

   brillo::SecureBlob extended_tpm_key;
   if (TPMErrorBase err = tpm_->SealToPcrWithAuthorization(
           vkk_key, auth_value, extended_pcr_map, &extended_tpm_key)) {
     LOG(ERROR) << "Failed to wrap vkk with creds for extended PCR: " << *err;
     return base::nullopt;
   }

   AuthBlockState auth_block_state;
   AuthBlockState::TpmBoundToPcrAuthBlockState* auth_state =
       auth_block_state.mutable_tpm_bound_to_pcr_state();

   // Allow this to fail.  It is not absolutely necessary; it allows us to
   // detect a TPM clear.  If this fails due to a transient issue, then on next
   // successful login, the vault keyset will be re-saved anyway.
   brillo::SecureBlob pub_key_hash;
   if (TPMErrorBase err =
           tpm_->GetPublicKeyHash(cryptohome_key, &pub_key_hash)) {
     LOG(ERROR) << "Failed to get the TPM public key hash: " << *err;
   } else {
     auth_state->set_tpm_public_key_hash(pub_key_hash.data(),
                                         pub_key_hash.size());
   }

   auth_state->set_scrypt_derived(true);
   auth_state->set_tpm_key(tpm_key.data(), tpm_key.size());
   auth_state->set_extended_tpm_key(extended_tpm_key.data(),
                                    extended_tpm_key.size());

   // Pass back the vkk_key and vkk_iv so the generic secret wrapping can use it.
   key_blobs->vkk_key = vkk_key;
   // Note that one might expect the IV to be part of the AuthBlockState. But
   // since it's taken from the scrypt output, it's actually created by the auth
   // block, not used to initialize the auth block.
   key_blobs->vkk_iv = vkk_iv;
   key_blobs->chaps_iv = vkk_iv;

   return auth_block_state;
 }

 bool TpmBoundToPcrAuthBlock::Derive(const AuthInput& auth_input,
                                     const AuthBlockState& state,
                                     KeyBlobs* key_out_data,
                                     CryptoError* error) {
   if (!state.has_tpm_bound_to_pcr_state()) {
     DLOG(FATAL) << "Called with an invalid auth block state";
     return false;
   }

   const AuthBlockState::TpmBoundToPcrAuthBlockState& tpm_state =
       state.tpm_bound_to_pcr_state();

   if (!tpm_state.scrypt_derived()) {
     LOG(ERROR) << "All TpmBoundtoPcr operations should be scrypt derived.";
     return false;
   }

   brillo::SecureBlob tpm_public_key_hash;
   if (tpm_state.has_tpm_public_key_hash()) {
     tpm_public_key_hash.assign(tpm_state.tpm_public_key_hash().begin(),
                                tpm_state.tpm_public_key_hash().end());
   }

   if (!utils_.CheckTPMReadiness(tpm_state.has_tpm_key(),
                                 tpm_state.has_tpm_public_key_hash(),
                                 tpm_public_key_hash, error)) {
     return false;
   }

   key_out_data->vkk_iv = brillo::SecureBlob(kAesBlockSize);
   key_out_data->vkk_key = brillo::SecureBlob(kDefaultAesKeySize);

   bool locked_to_single_user = auth_input.locked_to_single_user.value_or(false);
   brillo::SecureBlob salt(tpm_state.salt().begin(), tpm_state.salt().end());
   std::string tpm_key_str = locked_to_single_user ? tpm_state.extended_tpm_key()
                                                   : tpm_state.tpm_key();
   brillo::SecureBlob tpm_key(tpm_key_str.begin(), tpm_key_str.end());

   if (!DecryptTpmBoundToPcr(auth_input.user_input.value(), tpm_key, salt, error,
                             &key_out_data->vkk_iv.value(),
                             &key_out_data->vkk_key.value())) {
     return false;
   }

   key_out_data->chaps_iv = key_out_data->vkk_iv;

   if (tpm_state.has_wrapped_reset_seed()) {
     key_out_data->wrapped_reset_seed = brillo::SecureBlob();
     key_out_data->wrapped_reset_seed.value().assign(
         tpm_state.wrapped_reset_seed().begin(),
         tpm_state.wrapped_reset_seed().end());
   }

   if (!tpm_state.has_tpm_public_key_hash() && error) {
     *error = CryptoError::CE_NO_PUBLIC_KEY_HASH;
   }

   return true;
 }

 bool TpmBoundToPcrAuthBlock::DecryptTpmBoundToPcr(
     const brillo::SecureBlob& vault_key,
     const brillo::SecureBlob& tpm_key,
     const brillo::SecureBlob& salt,
     CryptoError* error,
     brillo::SecureBlob* vkk_iv,
     brillo::SecureBlob* vkk_key) const {
   brillo::SecureBlob pass_blob(kDefaultPassBlobSize);

   // Prepare the parameters for scrypt.
   std::vector<brillo::SecureBlob*> gen_secrets{&pass_blob, vkk_iv};
   bool derive_result = false;

   base::WaitableEvent done(base::WaitableEvent::ResetPolicy::MANUAL,
                            base::WaitableEvent::InitialState::NOT_SIGNALED);

   // Derive secrets on scrypt task runner.
   scrypt_task_runner_->PostTask(
       FROM_HERE,
       base::BindOnce(
           [](const brillo::SecureBlob& passkey, const brillo::SecureBlob& salt,
              std::vector<brillo::SecureBlob*> gen_secrets, bool* result,
              base::WaitableEvent* done) {
             *result =
                 DeriveSecretsScrypt(passkey, salt, std::move(gen_secrets));
             done->Signal();
           },
           vault_key, salt, gen_secrets, &derive_result, &done));

   // Preload the sealed data while deriving secrets in scrypt.
   ScopedKeyHandle preload_handle;
   TPMErrorBase err;
   for (int i = 0; i < kTpmDecryptMaxRetries; ++i) {
     err = tpm_->PreloadSealedData(tpm_key, &preload_handle);
     if (err == nullptr)
       break;

     if (!TpmAuthBlockUtils::TPMErrorIsRetriable(err))
       break;
   }

   // Wait for the scrypt finished.
   done.Wait();

   if (!derive_result) {
     LOG(ERROR) << "scrypt derivation failed";
     return false;
   }

   if (err) {
     LOG(ERROR) << "Failed to preload the sealed data: " << *err;
     return false;
   }

   // On TPM1.2 devices, preloading sealed data is meaningless and
   // UnsealWithAuthorization will check the preload_handle not containing any
   // value.
   base::Optional<TpmKeyHandle> handle;
   if (preload_handle.has_value()) {
     handle = preload_handle.value();
   }

   for (int i = 0; i < kTpmDecryptMaxRetries; ++i) {
     TpmKeyHandle cryptohome_key = cryptohome_key_loader_->GetCryptohomeKey();
     brillo::SecureBlob auth_value;
     if (TPMErrorBase auth_err =
             tpm_->GetAuthValue(cryptohome_key, pass_blob, &auth_value)) {
       err = CreateErrorWrap<TPMError>(std::move(auth_err),
                                       "Failed to get auth value");
       // TODO(yich): Reload cryptohome key might be a better choice.
       break;
     }

     std::map<uint32_t, std::string> pcr_map({{kTpmSingleUserPCR, ""}});
     err = tpm_->UnsealWithAuthorization(handle, tpm_key, auth_value, pcr_map,
                                         vkk_key);

     if (err == nullptr)
       return true;

     if (!TpmAuthBlockUtils::TPMErrorIsRetriable(err))
       break;

     // If the error is retriable, reload the key first.
     if (!cryptohome_key_loader_->ReloadCryptohomeKey()) {
       LOG(ERROR) << "Unable to reload Cryptohome key.";
       break;
     }
   }
   if (err) {
     LOG(ERROR) << "Failed to unwrap VKK with creds: " << *err;
   }
   *error = TpmAuthBlockUtils::TPMErrorToCrypto(err);
   return false;
 }

 }  // namespace cryptohome
	// Copyright 2020 The Chromium OS 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 "cryptohome/tpm_bound_to_pcr_auth_block.h"

	#include <map>
	#include <memory>
	#include <string>
	#include <utility>
	#include <vector>

	#include <base/check.h>
	#include <base/logging.h>
	#include <base/optional.h>
	#include <brillo/secure_blob.h>

	#include "cryptohome/crypto.h"
	#include "cryptohome/crypto/aes.h"
	#include "cryptohome/crypto/scrypt.h"
	#include "cryptohome/crypto/secure_blob_util.h"
	#include "cryptohome/crypto_error.h"
	#include "cryptohome/cryptohome_keys_manager.h"
	#include "cryptohome/cryptohome_metrics.h"
	#include "cryptohome/tpm.h"
	#include "cryptohome/tpm_auth_block_utils.h"
	#include "cryptohome/vault_keyset.pb.h"

	using hwsec::error::TPMError;
	using hwsec::error::TPMErrorBase;
	using hwsec_foundation::error::CreateErrorWrap;

	namespace cryptohome {

	TpmBoundToPcrAuthBlock::TpmBoundToPcrAuthBlock(
	Tpm* tpm, CryptohomeKeysManager* cryptohome_keys_manager)
	: AuthBlock(kTpmBackedPcrBound),
	tpm_(tpm),
	cryptohome_key_loader_(
	cryptohome_keys_manager->GetKeyLoader(CryptohomeKeyType::kRSA)),
	utils_(tpm, cryptohome_key_loader_) {
	CHECK(tpm != nullptr);
	CHECK(cryptohome_key_loader_ != nullptr);

	// Create the scrypt thread.
	// TODO(yich): Create another thread in userdataauth and passing it to here.
	base::Thread::Options options;
	options.message_pump_type = base::MessagePumpType::IO;
	scrypt_thread_ = std::make_unique<base::Thread>("scrypt_thread");
	scrypt_thread_->StartWithOptions(options);
	scrypt_task_runner_ = scrypt_thread_->task_runner();
	}

	base::Optional<AuthBlockState> TpmBoundToPcrAuthBlock::Create(
	const AuthInput& user_input, KeyBlobs* key_blobs, CryptoError* error) {
	const brillo::SecureBlob& vault_key = user_input.user_input.value();
	const brillo::SecureBlob& salt = user_input.salt.value();
	const std::string& obfuscated_username =
	user_input.obfuscated_username.value();

	// If the cryptohome key isn't loaded, try to load it.
	if (!cryptohome_key_loader_->HasCryptohomeKey())
	cryptohome_key_loader_->Init();

	// If the key still isn't loaded, fail the operation.
	if (!cryptohome_key_loader_->HasCryptohomeKey())
	return base::nullopt;

	const auto vkk_key = CreateSecureRandomBlob(kDefaultAesKeySize);
	brillo::SecureBlob pass_blob(kDefaultPassBlobSize);
	brillo::SecureBlob vkk_iv(kAesBlockSize);
	if (!DeriveSecretsScrypt(vault_key, salt, {&pass_blob, &vkk_iv}))
	return base::nullopt;

	std::map<uint32_t, std::string> default_pcr_map =
	tpm_->GetPcrMap(obfuscated_username, false /* use_extended_pcr */);
	std::map<uint32_t, std::string> extended_pcr_map =
	tpm_->GetPcrMap(obfuscated_username, true /* use_extended_pcr */);

	// Encrypt the VKK using the TPM and the user's passkey. The output is two
	// encrypted blobs, sealed to PCR in \|tpm_key\| and \|extended_tpm_key\|,
	// which are stored in the serialized vault keyset.
	TpmKeyHandle cryptohome_key = cryptohome_key_loader_->GetCryptohomeKey();
	brillo::SecureBlob auth_value;
	if (TPMErrorBase err =
	tpm_->GetAuthValue(cryptohome_key, pass_blob, &auth_value)) {
	LOG(ERROR) << "Failed to get auth value: " << *err;
	return base::nullopt;
	}

	brillo::SecureBlob tpm_key;
	if (TPMErrorBase err = tpm_->SealToPcrWithAuthorization(
	vkk_key, auth_value, default_pcr_map, &tpm_key)) {
	LOG(ERROR) << "Failed to wrap vkk with creds: " << *err;
	return base::nullopt;
	}

	brillo::SecureBlob extended_tpm_key;
	if (TPMErrorBase err = tpm_->SealToPcrWithAuthorization(
	vkk_key, auth_value, extended_pcr_map, &extended_tpm_key)) {
	LOG(ERROR) << "Failed to wrap vkk with creds for extended PCR: " << *err;
	return base::nullopt;
	}

	AuthBlockState auth_block_state;
	AuthBlockState::TpmBoundToPcrAuthBlockState* auth_state =
	auth_block_state.mutable_tpm_bound_to_pcr_state();

	// Allow this to fail. It is not absolutely necessary; it allows us to
	// detect a TPM clear. If this fails due to a transient issue, then on next
	// successful login, the vault keyset will be re-saved anyway.
	brillo::SecureBlob pub_key_hash;
	if (TPMErrorBase err =
	tpm_->GetPublicKeyHash(cryptohome_key, &pub_key_hash)) {
	LOG(ERROR) << "Failed to get the TPM public key hash: " << *err;
	} else {
	auth_state->set_tpm_public_key_hash(pub_key_hash.data(),
	pub_key_hash.size());
	}

	auth_state->set_scrypt_derived(true);
	auth_state->set_tpm_key(tpm_key.data(), tpm_key.size());
	auth_state->set_extended_tpm_key(extended_tpm_key.data(),
	extended_tpm_key.size());

	// Pass back the vkk_key and vkk_iv so the generic secret wrapping can use it.
	key_blobs->vkk_key = vkk_key;
	// Note that one might expect the IV to be part of the AuthBlockState. But
	// since it's taken from the scrypt output, it's actually created by the auth
	// block, not used to initialize the auth block.
	key_blobs->vkk_iv = vkk_iv;
	key_blobs->chaps_iv = vkk_iv;

	return auth_block_state;
	}

	bool TpmBoundToPcrAuthBlock::Derive(const AuthInput& auth_input,
	const AuthBlockState& state,
	KeyBlobs* key_out_data,
	CryptoError* error) {
	if (!state.has_tpm_bound_to_pcr_state()) {
	DLOG(FATAL) << "Called with an invalid auth block state";
	return false;
	}

	const AuthBlockState::TpmBoundToPcrAuthBlockState& tpm_state =
	state.tpm_bound_to_pcr_state();

	if (!tpm_state.scrypt_derived()) {
	LOG(ERROR) << "All TpmBoundtoPcr operations should be scrypt derived.";
	return false;
	}

	brillo::SecureBlob tpm_public_key_hash;
	if (tpm_state.has_tpm_public_key_hash()) {
	tpm_public_key_hash.assign(tpm_state.tpm_public_key_hash().begin(),
	tpm_state.tpm_public_key_hash().end());
	}

	if (!utils_.CheckTPMReadiness(tpm_state.has_tpm_key(),
	tpm_state.has_tpm_public_key_hash(),
	tpm_public_key_hash, error)) {
	return false;
	}

	key_out_data->vkk_iv = brillo::SecureBlob(kAesBlockSize);
	key_out_data->vkk_key = brillo::SecureBlob(kDefaultAesKeySize);

	bool locked_to_single_user = auth_input.locked_to_single_user.value_or(false);
	brillo::SecureBlob salt(tpm_state.salt().begin(), tpm_state.salt().end());
	std::string tpm_key_str = locked_to_single_user ? tpm_state.extended_tpm_key()
	: tpm_state.tpm_key();
	brillo::SecureBlob tpm_key(tpm_key_str.begin(), tpm_key_str.end());

	if (!DecryptTpmBoundToPcr(auth_input.user_input.value(), tpm_key, salt, error,
	&key_out_data->vkk_iv.value(),
	&key_out_data->vkk_key.value())) {
	return false;
	}

	key_out_data->chaps_iv = key_out_data->vkk_iv;

	if (tpm_state.has_wrapped_reset_seed()) {
	key_out_data->wrapped_reset_seed = brillo::SecureBlob();
	key_out_data->wrapped_reset_seed.value().assign(
	tpm_state.wrapped_reset_seed().begin(),
	tpm_state.wrapped_reset_seed().end());
	}

	if (!tpm_state.has_tpm_public_key_hash() && error) {
	*error = CryptoError::CE_NO_PUBLIC_KEY_HASH;
	}

	return true;
	}

	bool TpmBoundToPcrAuthBlock::DecryptTpmBoundToPcr(
	const brillo::SecureBlob& vault_key,
	const brillo::SecureBlob& tpm_key,
	const brillo::SecureBlob& salt,
	CryptoError* error,
	brillo::SecureBlob* vkk_iv,
	brillo::SecureBlob* vkk_key) const {
	brillo::SecureBlob pass_blob(kDefaultPassBlobSize);

	// Prepare the parameters for scrypt.
	std::vector<brillo::SecureBlob*> gen_secrets{&pass_blob, vkk_iv};
	bool derive_result = false;

	base::WaitableEvent done(base::WaitableEvent::ResetPolicy::MANUAL,
	base::WaitableEvent::InitialState::NOT_SIGNALED);

	// Derive secrets on scrypt task runner.
	scrypt_task_runner_->PostTask(
	FROM_HERE,
	base::BindOnce(
	[](const brillo::SecureBlob& passkey, const brillo::SecureBlob& salt,
	std::vector<brillo::SecureBlob> gen_secrets, bool result,
	base::WaitableEvent* done) {
	*result =
	DeriveSecretsScrypt(passkey, salt, std::move(gen_secrets));
	done->Signal();
	},
	vault_key, salt, gen_secrets, &derive_result, &done));

	// Preload the sealed data while deriving secrets in scrypt.
	ScopedKeyHandle preload_handle;
	TPMErrorBase err;
	for (int i = 0; i < kTpmDecryptMaxRetries; ++i) {
	err = tpm_->PreloadSealedData(tpm_key, &preload_handle);
	if (err == nullptr)
	break;

	if (!TpmAuthBlockUtils::TPMErrorIsRetriable(err))
	break;
	}

	// Wait for the scrypt finished.
	done.Wait();

	if (!derive_result) {
	LOG(ERROR) << "scrypt derivation failed";
	return false;
	}

	if (err) {
	LOG(ERROR) << "Failed to preload the sealed data: " << *err;
	return false;
	}

	// On TPM1.2 devices, preloading sealed data is meaningless and
	// UnsealWithAuthorization will check the preload_handle not containing any
	// value.
	base::Optional<TpmKeyHandle> handle;
	if (preload_handle.has_value()) {
	handle = preload_handle.value();
	}

	for (int i = 0; i < kTpmDecryptMaxRetries; ++i) {
	TpmKeyHandle cryptohome_key = cryptohome_key_loader_->GetCryptohomeKey();
	brillo::SecureBlob auth_value;
	if (TPMErrorBase auth_err =
	tpm_->GetAuthValue(cryptohome_key, pass_blob, &auth_value)) {
	err = CreateErrorWrap<TPMError>(std::move(auth_err),
	"Failed to get auth value");
	// TODO(yich): Reload cryptohome key might be a better choice.
	break;
	}

	std::map<uint32_t, std::string> pcr_map({{kTpmSingleUserPCR, ""}});
	err = tpm_->UnsealWithAuthorization(handle, tpm_key, auth_value, pcr_map,
	vkk_key);

	if (err == nullptr)
	return true;

	if (!TpmAuthBlockUtils::TPMErrorIsRetriable(err))
	break;

	// If the error is retriable, reload the key first.
	if (!cryptohome_key_loader_->ReloadCryptohomeKey()) {
	LOG(ERROR) << "Unable to reload Cryptohome key.";
	break;
	}
	}
	if (err) {
	LOG(ERROR) << "Failed to unwrap VKK with creds: " << *err;
	}
	*error = TpmAuthBlockUtils::TPMErrorToCrypto(err);
	return false;
	}

	} // namespace cryptohome