/*
* 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/pure_soft_keymaster_context.h>
#include <memory>
#include <openssl/aes.h>
#include <openssl/evp.h>
#include <openssl/hmac.h>
#include <openssl/rand.h>
#include <openssl/sha.h>
#include <openssl/x509v3.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/ec_key_factory.h>
#include <keymaster/km_openssl/hmac_key.h>
#include <keymaster/km_openssl/openssl_err.h>
#include <keymaster/km_openssl/openssl_utils.h>
#include <keymaster/km_openssl/rsa_key_factory.h>
#include <keymaster/km_openssl/soft_keymaster_enforcement.h>
#include <keymaster/km_openssl/triple_des_key.h>
#include <keymaster/logger.h>
#include <keymaster/operation.h>
#include <keymaster/wrapped_key.h>
#include "soft_attestation_cert.h"
using std::unique_ptr;
namespace keymaster {
PureSoftKeymasterContext::PureSoftKeymasterContext()
: 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)), os_version_(0), os_patchlevel_(0),
soft_keymaster_enforcement_(64, 64) {}
PureSoftKeymasterContext::~PureSoftKeymasterContext() {}
keymaster_error_t PureSoftKeymasterContext::SetSystemVersion(uint32_t os_version,
uint32_t os_patchlevel) {
os_version_ = os_version;
os_patchlevel_ = os_patchlevel;
return KM_ERROR_OK;
}
void PureSoftKeymasterContext::GetSystemVersion(uint32_t* os_version, uint32_t* os_patchlevel) const {
*os_version = os_version_;
*os_patchlevel = os_patchlevel_;
}
KeyFactory* PureSoftKeymasterContext::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*
PureSoftKeymasterContext::GetSupportedAlgorithms(size_t* algorithms_count) const {
*algorithms_count = array_length(supported_algorithms);
return supported_algorithms;
}
OperationFactory* PureSoftKeymasterContext::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);
}
keymaster_error_t PureSoftKeymasterContext::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 = SetKeyBlobAuthorizations(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, softwareRootOfTrust);
if (error != KM_ERROR_OK)
return error;
return SerializeIntegrityAssuredBlob(key_material, hidden, *hw_enforced, *sw_enforced, blob);
}
keymaster_error_t PureSoftKeymasterContext::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;
return UpgradeSoftKeyBlob(key, os_version_, os_patchlevel_, upgrade_params, upgraded_key);
}
keymaster_error_t PureSoftKeymasterContext::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.
//
// 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;
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);
};
AuthorizationSet hidden;
error = BuildHiddenAuthorizations(additional_params, &hidden, softwareRootOfTrust);
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);
return constructKey();
}
keymaster_error_t PureSoftKeymasterContext::DeleteKey(const KeymasterKeyBlob& /* blob */) const {
// Nothing to do for software-only contexts.
return KM_ERROR_OK;
}
keymaster_error_t PureSoftKeymasterContext::DeleteAllKeys() const {
return KM_ERROR_OK;
}
keymaster_error_t PureSoftKeymasterContext::AddRngEntropy(const uint8_t* buf, size_t length) const {
// XXX TODO according to boringssl openssl/rand.h RAND_add is deprecated and does
// nothing
RAND_add(buf, length, 0 /* Don't assume any entropy is added to the pool. */);
return KM_ERROR_OK;
}
keymaster_error_t PureSoftKeymasterContext::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);
}
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;
}
keymaster_error_t PureSoftKeymasterContext::UnwrapKey(
const KeymasterKeyBlob& wrapped_key_blob, const KeymasterKeyBlob& wrapping_key_blob,
const AuthorizationSet& /* wrapping_key_params */, const KeymasterKeyBlob& masking_key,
AuthorizationSet* wrapped_key_params, keymaster_key_format_t* wrapped_key_format,
KeymasterKeyBlob* wrapped_key_material) const {
keymaster_error_t error = KM_ERROR_OK;
if (!wrapped_key_material) return KM_ERROR_UNEXPECTED_NULL_POINTER;
// Parse wrapped key data
KeymasterBlob iv;
KeymasterKeyBlob transit_key;
KeymasterKeyBlob secure_key;
KeymasterBlob tag;
KeymasterBlob wrapped_key_description;
error = parse_wrapped_key(wrapped_key_blob, &iv, &transit_key, &secure_key, &tag,
wrapped_key_params, wrapped_key_format, &wrapped_key_description);
if (error != KM_ERROR_OK) return error;
UniquePtr<Key> key;
auto wrapping_key_params = AuthorizationSetBuilder()
.RsaEncryptionKey(2048, 65537)
.Digest(KM_DIGEST_SHA1)
.Padding(KM_PAD_RSA_OAEP)
.Authorization(TAG_PURPOSE, KM_PURPOSE_WRAP)
.build();
error = ParseKeyBlob(wrapping_key_blob, wrapping_key_params, &key);
if (error != KM_ERROR_OK) return error;
// Ensure the wrapping key has the right purpose
if (!key->hw_enforced().Contains(TAG_PURPOSE, KM_PURPOSE_WRAP) &&
!key->sw_enforced().Contains(TAG_PURPOSE, KM_PURPOSE_WRAP)) {
return KM_ERROR_INCOMPATIBLE_PURPOSE;
}
auto operation_factory = GetOperationFactory(KM_ALGORITHM_RSA, KM_PURPOSE_DECRYPT);
if (!operation_factory) return KM_ERROR_UNKNOWN_ERROR;
AuthorizationSet out_params;
OperationPtr operation(
operation_factory->CreateOperation(move(*key), wrapping_key_params, &error));
if (!operation.get()) return error;
error = operation->Begin(wrapping_key_params, &out_params);
if (error != KM_ERROR_OK) return error;
Buffer input;
Buffer output;
if (!input.Reinitialize(transit_key.key_material, transit_key.key_material_size)) {
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
}
error = operation->Finish(wrapping_key_params, input, Buffer() /* signature */, &out_params,
&output);
if (error != KM_ERROR_OK) return error;
// decrypt the encrypted key material with the transit key
KeymasterKeyBlob key_material = {output.peek_read(), output.available_read()};
// XOR the transit key with the masking key
if (key_material.key_material_size != masking_key.key_material_size) {
return KM_ERROR_INVALID_ARGUMENT;
}
for (size_t i = 0; i < key_material.key_material_size; i++) {
key_material.writable_data()[i] ^= masking_key.key_material[i];
}
auto transit_key_authorizations = AuthorizationSetBuilder()
.AesEncryptionKey(256)
.Padding(KM_PAD_NONE)
.Authorization(TAG_BLOCK_MODE, KM_MODE_GCM)
.Authorization(TAG_NONCE, iv)
.Authorization(TAG_MIN_MAC_LENGTH, 128)
.build();
if (transit_key_authorizations.is_valid() != AuthorizationSet::Error::OK) {
return TranslateAuthorizationSetError(transit_key_authorizations.is_valid());
}
auto gcm_params = AuthorizationSetBuilder()
.Padding(KM_PAD_NONE)
.Authorization(TAG_BLOCK_MODE, KM_MODE_GCM)
.Authorization(TAG_NONCE, iv)
.Authorization(TAG_MAC_LENGTH, 128)
.build();
if (gcm_params.is_valid() != AuthorizationSet::Error::OK) {
return TranslateAuthorizationSetError(transit_key_authorizations.is_valid());
}
auto aes_factory = GetKeyFactory(KM_ALGORITHM_AES);
if (!aes_factory) return KM_ERROR_UNKNOWN_ERROR;
UniquePtr<Key> aes_key;
error = aes_factory->LoadKey(move(key_material), gcm_params, move(transit_key_authorizations),
AuthorizationSet(), &aes_key);
if (error != KM_ERROR_OK) return error;
auto aes_operation_factory = GetOperationFactory(KM_ALGORITHM_AES, KM_PURPOSE_DECRYPT);
if (!aes_operation_factory) return KM_ERROR_UNKNOWN_ERROR;
OperationPtr aes_operation(
aes_operation_factory->CreateOperation(move(*aes_key), gcm_params, &error));
if (!aes_operation.get()) return error;
error = aes_operation->Begin(gcm_params, &out_params);
if (error != KM_ERROR_OK) return error;
size_t consumed = 0;
Buffer encrypted_key, plaintext;
if (!plaintext.Reinitialize(secure_key.key_material_size + tag.data_length)) {
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
}
if (!encrypted_key.Reinitialize(secure_key.key_material_size + tag.data_length)) {
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
}
if (!encrypted_key.write(secure_key.key_material, secure_key.key_material_size)) {
return KM_ERROR_UNKNOWN_ERROR;
}
if (!encrypted_key.write(tag.data, tag.data_length)) {
return KM_ERROR_UNKNOWN_ERROR;
}
AuthorizationSet update_outparams;
auto update_params = AuthorizationSetBuilder()
.Authorization(TAG_ASSOCIATED_DATA, wrapped_key_description.data,
wrapped_key_description.data_length)
.build();
if (update_params.is_valid() != AuthorizationSet::Error::OK) {
return TranslateAuthorizationSetError(transit_key_authorizations.is_valid());
}
error = aes_operation->Update(update_params, encrypted_key, &update_outparams, &plaintext,
&consumed);
if (error != KM_ERROR_OK) return error;
AuthorizationSet finish_params, finish_out_params;
Buffer finish_input;
error = aes_operation->Finish(finish_params, finish_input, Buffer() /* signature */,
&finish_out_params, &plaintext);
if (error != KM_ERROR_OK) return error;
*wrapped_key_material = {plaintext.peek_read(), plaintext.available_read()};
if (!wrapped_key_material->key_material && plaintext.peek_read()) {
return KM_ERROR_MEMORY_ALLOCATION_FAILED;
}
return error;
}
} // namespace keymaster