/*
* Copyright 2015 The Android Open Source Project
*
* 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 <keymaster/contexts/soft_keymaster_context.h>
#include <memory>
#include <openssl/rand.h>
#include <keymaster/android_keymaster_utils.h>
#include <keymaster/key_blob_utils/auth_encrypted_key_blob.h>
#include <keymaster/key_blob_utils/integrity_assured_key_blob.h>
#include <keymaster/key_blob_utils/ocb_utils.h>
#include <keymaster/key_blob_utils/software_keyblobs.h>
#include <keymaster/km_openssl/aes_key.h>
#include <keymaster/km_openssl/asymmetric_key.h>
#include <keymaster/km_openssl/attestation_utils.h>
#include <keymaster/km_openssl/hmac_key.h>
#include <keymaster/km_openssl/openssl_err.h>
#include <keymaster/km_openssl/triple_des_key.h>
#include <keymaster/legacy_support/ec_keymaster0_key.h>
#include <keymaster/legacy_support/ec_keymaster1_key.h>
#include <keymaster/legacy_support/keymaster0_engine.h>
#include <keymaster/legacy_support/rsa_keymaster0_key.h>
#include <keymaster/legacy_support/rsa_keymaster1_key.h>
#include <keymaster/logger.h>
#include "soft_attestation_cert.h"
using std::unique_ptr;
namespace keymaster {
namespace {
KeymasterBlob string2Blob(const std::string& str) {
return KeymasterBlob(reinterpret_cast<const uint8_t*>(str.data()), str.size());
}
} // anonymous namespace
SoftKeymasterContext::SoftKeymasterContext(const std::string& root_of_trust)
: rsa_factory_(new RsaKeyFactory(this)), ec_factory_(new EcKeyFactory(this)),
aes_factory_(new AesKeyFactory(this, this)),
tdes_factory_(new TripleDesKeyFactory(this, this)),
hmac_factory_(new HmacKeyFactory(this, this)), km1_dev_(nullptr),
root_of_trust_(string2Blob(root_of_trust)), os_version_(0), os_patchlevel_(0) {}
SoftKeymasterContext::~SoftKeymasterContext() {}
keymaster_error_t SoftKeymasterContext::SetHardwareDevice(keymaster0_device_t* keymaster0_device) {
if (!keymaster0_device)
return KM_ERROR_UNEXPECTED_NULL_POINTER;
if ((keymaster0_device->flags & KEYMASTER_SOFTWARE_ONLY) != 0) {
LOG_E("SoftKeymasterContext only wraps hardware keymaster0 devices", 0);
return KM_ERROR_INVALID_ARGUMENT;
}
km0_engine_.reset(new Keymaster0Engine(keymaster0_device));
rsa_factory_.reset(new RsaKeymaster0KeyFactory(this, km0_engine_.get()));
ec_factory_.reset(new EcdsaKeymaster0KeyFactory(this, km0_engine_.get()));
// Keep AES and HMAC factories.
return KM_ERROR_OK;
}
keymaster_error_t SoftKeymasterContext::SetHardwareDevice(keymaster1_device_t* keymaster1_device) {
if (!keymaster1_device)
return KM_ERROR_UNEXPECTED_NULL_POINTER;
km1_dev_ = keymaster1_device;
km1_engine_.reset(new Keymaster1Engine(keymaster1_device));
rsa_factory_.reset(new RsaKeymaster1KeyFactory(this, km1_engine_.get()));
ec_factory_.reset(new EcdsaKeymaster1KeyFactory(this, km1_engine_.get()));
// Use default HMAC and AES key factories. Higher layers will pass HMAC/AES keys/ops that are
// supported by the hardware to it and other ones to the software-only factory.
return KM_ERROR_OK;
}
keymaster_error_t SoftKeymasterContext::SetSystemVersion(uint32_t os_version,
uint32_t os_patchlevel) {
os_version_ = os_version;
os_patchlevel_ = os_patchlevel;
return KM_ERROR_OK;
}
void SoftKeymasterContext::GetSystemVersion(uint32_t* os_version, uint32_t* os_patchlevel) const {
*os_version = os_version_;
*os_patchlevel = os_patchlevel_;
}
KeyFactory* SoftKeymasterContext::GetKeyFactory(keymaster_algorithm_t algorithm) const {
switch (algorithm) {
case KM_ALGORITHM_RSA:
return rsa_factory_.get();
case KM_ALGORITHM_EC:
return ec_factory_.get();
case KM_ALGORITHM_AES:
return aes_factory_.get();
case KM_ALGORITHM_TRIPLE_DES:
return tdes_factory_.get();
case KM_ALGORITHM_HMAC:
return hmac_factory_.get();
default:
return nullptr;
}
}
static keymaster_algorithm_t supported_algorithms[] = {KM_ALGORITHM_RSA, KM_ALGORITHM_EC,
KM_ALGORITHM_AES, KM_ALGORITHM_HMAC};
keymaster_algorithm_t*
SoftKeymasterContext::GetSupportedAlgorithms(size_t* algorithms_count) const {
*algorithms_count = array_length(supported_algorithms);
return supported_algorithms;
}
OperationFactory* SoftKeymasterContext::GetOperationFactory(keymaster_algorithm_t algorithm,
keymaster_purpose_t purpose) const {
KeyFactory* key_factory = GetKeyFactory(algorithm);
if (!key_factory)
return nullptr;
return key_factory->GetOperationFactory(purpose);
}
static keymaster_error_t TranslateAuthorizationSetError(AuthorizationSet::Error err) {
switch (err) {
case AuthorizationSet::OK:
return KM_ERROR_OK;
case AuthorizationSet::ALLOCATION_FAILURE:
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
case AuthorizationSet::MALFORMED_DATA:
return KM_ERROR_UNKNOWN_ERROR;
}
return KM_ERROR_OK;
}
static keymaster_error_t SetAuthorizations(const AuthorizationSet& key_description,
keymaster_key_origin_t origin, uint32_t os_version,
uint32_t os_patchlevel, AuthorizationSet* hw_enforced,
AuthorizationSet* sw_enforced) {
sw_enforced->Clear();
for (auto& entry : key_description) {
switch (entry.tag) {
// These cannot be specified by the client.
case KM_TAG_ROOT_OF_TRUST:
case KM_TAG_ORIGIN:
LOG_E("Root of trust and origin tags may not be specified", 0);
return KM_ERROR_INVALID_TAG;
// These don't work.
case KM_TAG_ROLLBACK_RESISTANT:
LOG_E("KM_TAG_ROLLBACK_RESISTANT not supported", 0);
return KM_ERROR_UNSUPPORTED_TAG;
// These are hidden.
case KM_TAG_APPLICATION_ID:
case KM_TAG_APPLICATION_DATA:
break;
// Everything else we just copy into sw_enforced, unless the KeyFactory has placed it in
// hw_enforced, in which case we defer to its decision.
default:
if (hw_enforced->GetTagCount(entry.tag) == 0)
sw_enforced->push_back(entry);
break;
}
}
sw_enforced->push_back(TAG_CREATION_DATETIME, java_time(time(nullptr)));
sw_enforced->push_back(TAG_ORIGIN, origin);
sw_enforced->push_back(TAG_OS_VERSION, os_version);
sw_enforced->push_back(TAG_OS_PATCHLEVEL, os_patchlevel);
return TranslateAuthorizationSetError(sw_enforced->is_valid());
}
keymaster_error_t SoftKeymasterContext::CreateKeyBlob(const AuthorizationSet& key_description,
const keymaster_key_origin_t origin,
const KeymasterKeyBlob& key_material,
KeymasterKeyBlob* blob,
AuthorizationSet* hw_enforced,
AuthorizationSet* sw_enforced) const {
keymaster_error_t error = SetAuthorizations(key_description, origin, os_version_,
os_patchlevel_, hw_enforced, sw_enforced);
if (error != KM_ERROR_OK)
return error;
AuthorizationSet hidden;
error = BuildHiddenAuthorizations(key_description, &hidden, root_of_trust_);
if (error != KM_ERROR_OK)
return error;
return SerializeIntegrityAssuredBlob(key_material, hidden, *hw_enforced, *sw_enforced, blob);
}
keymaster_error_t SoftKeymasterContext::UpgradeKeyBlob(const KeymasterKeyBlob& key_to_upgrade,
const AuthorizationSet& upgrade_params,
KeymasterKeyBlob* upgraded_key) const {
UniquePtr<Key> key;
keymaster_error_t error = ParseKeyBlob(key_to_upgrade, upgrade_params, &key);
if (error != KM_ERROR_OK)
return error;
// Three cases here:
//
// 1. Software key blob. Version info, if present, is in sw_enforced. If not present, we
// should add it.
//
// 2. Keymaster0 hardware key blob. Version info, if present, is in sw_enforced. If not
// present we should add it.
//
// 3. Keymaster1 hardware key blob. Version info is not present and we shouldn't have been
// asked to upgrade.
// Handle case 3.
if (km1_dev_ && key->hw_enforced().Contains(TAG_PURPOSE) &&
!key->hw_enforced().Contains(TAG_OS_PATCHLEVEL))
return KM_ERROR_INVALID_ARGUMENT;
// Handle case 1 and 2
return UpgradeSoftKeyBlob(key, os_version_, os_patchlevel_, upgrade_params, upgraded_key);
}
keymaster_error_t SoftKeymasterContext::ParseKeyBlob(const KeymasterKeyBlob& blob,
const AuthorizationSet& additional_params,
UniquePtr<Key>* key) const {
// This is a little bit complicated.
//
// The SoftKeymasterContext has to handle a lot of different kinds of key blobs.
//
// 1. New keymaster1 software key blobs. These are integrity-assured but not encrypted. The
// raw key material and auth sets should be extracted and returned. This is the kind
// produced by this context when the KeyFactory doesn't use keymaster0 to back the keys.
//
// 2. Old keymaster1 software key blobs. These are OCB-encrypted with an all-zero master key.
// They should be decrypted and the key material and auth sets extracted and returned.
//
// 3. Old keymaster0 software key blobs. These are raw key material with a small header tacked
// on the front. They don't have auth sets, so reasonable defaults are generated and
// returned along with the raw key material.
//
// 4. New keymaster0 hardware key blobs. These are integrity-assured but not encrypted (though
// they're protected by the keymaster0 hardware implementation). The keymaster0 key blob
// and auth sets should be extracted and returned.
//
// 5. Keymaster1 hardware key blobs. These are raw hardware key blobs. They contain auth
// sets, which we retrieve from the hardware module.
//
// 6. Old keymaster0 hardware key blobs. These are raw hardware key blobs. They don't have
// auth sets so reasonable defaults are generated and returned along with the key blob.
//
// Determining what kind of blob has arrived is somewhat tricky. What helps is that
// integrity-assured and OCB-encrypted blobs are self-consistent and effectively impossible to
// parse as anything else. Old keymaster0 software key blobs have a header. It's reasonably
// unlikely that hardware keys would have the same header. So anything that is neither
// integrity-assured nor OCB-encrypted and lacks the old software key header is assumed to be
// keymaster0 hardware.
AuthorizationSet hw_enforced;
AuthorizationSet sw_enforced;
KeymasterKeyBlob key_material;
AuthorizationSet hidden;
keymaster_error_t error;
auto constructKey = [&, this] () mutable -> keymaster_error_t {
// GetKeyFactory
if (error != KM_ERROR_OK) return error;
keymaster_algorithm_t algorithm;
if (!hw_enforced.GetTagValue(TAG_ALGORITHM, &algorithm) &&
!sw_enforced.GetTagValue(TAG_ALGORITHM, &algorithm)) {
return KM_ERROR_INVALID_ARGUMENT;
}
auto factory = GetKeyFactory(algorithm);
return factory->LoadKey(move(key_material), additional_params, move(hw_enforced),
move(sw_enforced), key);
};
error = BuildHiddenAuthorizations(additional_params, &hidden, root_of_trust_);
if (error != KM_ERROR_OK)
return error;
// Assume it's an integrity-assured blob (new software-only blob, or new keymaster0-backed
// blob).
error = DeserializeIntegrityAssuredBlob(blob, hidden, &key_material, &hw_enforced, &sw_enforced);
if (error != KM_ERROR_INVALID_KEY_BLOB)
return constructKey();
// Wasn't an integrity-assured blob. Maybe it's an OCB-encrypted blob.
error = ParseOcbAuthEncryptedBlob(blob, hidden, &key_material, &hw_enforced, &sw_enforced);
if (error == KM_ERROR_OK)
LOG_D("Parsed an old keymaster1 software key", 0);
if (error != KM_ERROR_INVALID_KEY_BLOB)
return constructKey();
// Wasn't an OCB-encrypted blob. Maybe it's an old softkeymaster blob.
error = ParseOldSoftkeymasterBlob(blob, &key_material, &hw_enforced, &sw_enforced);
if (error == KM_ERROR_OK)
LOG_D("Parsed an old sofkeymaster key", 0);
if (error != KM_ERROR_INVALID_KEY_BLOB)
return constructKey();
if (km1_dev_) {
error = ParseKeymaster1HwBlob(blob, additional_params, &key_material, &hw_enforced,
&sw_enforced);
} else if (km0_engine_) {
error = ParseKeymaster0HwBlob(blob, &key_material, &hw_enforced, &sw_enforced);
} else {
return KM_ERROR_INVALID_KEY_BLOB;
}
return constructKey();
}
keymaster_error_t SoftKeymasterContext::DeleteKey(const KeymasterKeyBlob& blob) const {
if (km1_engine_) {
// HACK. Due to a bug with Qualcomm's Keymaster implementation, which causes the device to
// reboot if we pass it a key blob it doesn't understand, we need to check for software
// keys. If it looks like a software key there's nothing to do so we just return.
KeymasterKeyBlob key_material;
AuthorizationSet hw_enforced, sw_enforced;
keymaster_error_t error = DeserializeIntegrityAssuredBlob_NoHmacCheck(
blob, &key_material, &hw_enforced, &sw_enforced);
if (error == KM_ERROR_OK) {
return KM_ERROR_OK;
}
return km1_engine_->DeleteKey(blob);
}
if (km0_engine_) {
// This could be a keymaster0 hardware key, and it could be either raw or encapsulated in an
// integrity-assured blob. If it's integrity-assured, we can't validate it strongly,
// because we don't have the necessary additional_params data. However, the probability
// that anything other than an integrity-assured blob would have all of the structure
// required to decode as a valid blob is low -- unless it's maliciously-constructed, but the
// deserializer should be proof against bad data, as should the keymaster0 hardware.
//
// Thus, we first try to parse it as integrity-assured. If that works, we pass the result
// to the underlying hardware. If not, we pass blob unmodified to the underlying hardware.
KeymasterKeyBlob key_material;
AuthorizationSet hw_enforced, sw_enforced;
keymaster_error_t error = DeserializeIntegrityAssuredBlob_NoHmacCheck(
blob, &key_material, &hw_enforced, &sw_enforced);
if (error == KM_ERROR_OK && km0_engine_->DeleteKey(key_material))
return KM_ERROR_OK;
km0_engine_->DeleteKey(blob);
// We succeed unconditionally at this point, even if delete failed. Failure indicates that
// either the blob is a software blob (which we can't distinguish with certainty without
// additional_params) or because it is a hardware blob and the hardware failed. In the
// first case, there is no error. In the second case, the client can't do anything to fix
// it anyway, so it's not too harmful to simply swallow the error. This is not ideal, but
// it's the least-bad alternative.
return KM_ERROR_OK;
}
// Nothing to do for software-only contexts.
return KM_ERROR_OK;
}
keymaster_error_t SoftKeymasterContext::DeleteAllKeys() const {
if (km1_engine_)
return km1_engine_->DeleteAllKeys();
if (km0_engine_ && !km0_engine_->DeleteAllKeys())
return KM_ERROR_UNKNOWN_ERROR;
return KM_ERROR_OK;
}
keymaster_error_t SoftKeymasterContext::AddRngEntropy(const uint8_t* buf, size_t length) const {
RAND_add(buf, length, 0 /* Don't assume any entropy is added to the pool. */);
return KM_ERROR_OK;
}
keymaster_error_t SoftKeymasterContext::ParseKeymaster1HwBlob(
const KeymasterKeyBlob& blob, const AuthorizationSet& additional_params,
KeymasterKeyBlob* key_material, AuthorizationSet* hw_enforced,
AuthorizationSet* sw_enforced) const {
assert(km1_dev_);
keymaster_blob_t client_id = {nullptr, 0};
keymaster_blob_t app_data = {nullptr, 0};
keymaster_blob_t* client_id_ptr = nullptr;
keymaster_blob_t* app_data_ptr = nullptr;
if (additional_params.GetTagValue(TAG_APPLICATION_ID, &client_id))
client_id_ptr = &client_id;
if (additional_params.GetTagValue(TAG_APPLICATION_DATA, &app_data))
app_data_ptr = &app_data;
// Get key characteristics, which incidentally verifies that the HW recognizes the key.
keymaster_key_characteristics_t* characteristics;
keymaster_error_t error = km1_dev_->get_key_characteristics(km1_dev_, &blob, client_id_ptr,
app_data_ptr, &characteristics);
if (error != KM_ERROR_OK)
return error;
unique_ptr<keymaster_key_characteristics_t, Characteristics_Delete> characteristics_deleter(
characteristics);
LOG_D("Module \"%s\" accepted key", km1_dev_->common.module->name);
hw_enforced->Reinitialize(characteristics->hw_enforced);
sw_enforced->Reinitialize(characteristics->sw_enforced);
*key_material = blob;
return KM_ERROR_OK;
}
keymaster_error_t SoftKeymasterContext::ParseKeymaster0HwBlob(const KeymasterKeyBlob& blob,
KeymasterKeyBlob* key_material,
AuthorizationSet* hw_enforced,
AuthorizationSet* sw_enforced) const {
assert(km0_engine_);
unique_ptr<EVP_PKEY, EVP_PKEY_Delete> tmp_key(km0_engine_->GetKeymaster0PublicKey(blob));
if (!tmp_key)
return KM_ERROR_INVALID_KEY_BLOB;
LOG_D("Module \"%s\" accepted key", km0_engine_->device()->common.module->name);
keymaster_error_t error = FakeKeyAuthorizations(tmp_key.get(), hw_enforced, sw_enforced);
if (error == KM_ERROR_OK)
*key_material = blob;
return error;
}
keymaster_error_t SoftKeymasterContext::GenerateAttestation(const Key& key,
const AuthorizationSet& attest_params, CertChainPtr* cert_chain) const {
keymaster_error_t error = KM_ERROR_OK;
keymaster_algorithm_t key_algorithm;
if (!key.authorizations().GetTagValue(TAG_ALGORITHM, &key_algorithm)) {
return KM_ERROR_UNKNOWN_ERROR;
}
if ((key_algorithm != KM_ALGORITHM_RSA && key_algorithm != KM_ALGORITHM_EC))
return KM_ERROR_INCOMPATIBLE_ALGORITHM;
// We have established that the given key has the correct algorithm, and because this is the
// SoftKeymasterContext we can assume that the Key is an AsymmetricKey. So we can downcast.
const AsymmetricKey& asymmetric_key = static_cast<const AsymmetricKey&>(key);
auto attestation_chain = getAttestationChain(key_algorithm, &error);
if (error != KM_ERROR_OK) return error;
auto attestation_key = getAttestationKey(key_algorithm, &error);
if (error != KM_ERROR_OK) return error;
return generate_attestation(asymmetric_key, attest_params,
*attestation_chain, *attestation_key, *this, cert_chain);
}
keymaster_error_t SoftKeymasterContext::UnwrapKey(const KeymasterKeyBlob&, const KeymasterKeyBlob&,
const AuthorizationSet&, const KeymasterKeyBlob&,
AuthorizationSet*, keymaster_key_format_t*,
KeymasterKeyBlob*) const {
return KM_ERROR_UNIMPLEMENTED;
}
} // namespace keymaster