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//
// Copyright (C) 2020 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 "host/commands/secure_env/primary_key_builder.h"
#include <android-base/logging.h>
#include <tss2/tss2_mu.h>
#include <tss2/tss2_rc.h>
PrimaryKeyBuilder::PrimaryKeyBuilder() : public_area_({}) {
public_area_.nameAlg = TPM2_ALG_SHA256;
};
void PrimaryKeyBuilder::SigningKey() {
public_area_.type = TPM2_ALG_KEYEDHASH;
public_area_.objectAttributes |= TPMA_OBJECT_SIGN_ENCRYPT;
public_area_.objectAttributes |= TPMA_OBJECT_USERWITHAUTH;
public_area_.objectAttributes |= TPMA_OBJECT_SENSITIVEDATAORIGIN;
public_area_.parameters.keyedHashDetail.scheme = (TPMT_KEYEDHASH_SCHEME) {
.scheme = TPM2_ALG_HMAC,
.details.hmac.hashAlg = TPM2_ALG_SHA256,
};
}
void PrimaryKeyBuilder::ParentKey() {
public_area_.type = TPM2_ALG_SYMCIPHER;
public_area_.objectAttributes |= TPMA_OBJECT_USERWITHAUTH;
public_area_.objectAttributes |= TPMA_OBJECT_RESTRICTED;
public_area_.objectAttributes |= TPMA_OBJECT_DECRYPT;
public_area_.objectAttributes |= TPMA_OBJECT_FIXEDTPM;
public_area_.objectAttributes |= TPMA_OBJECT_FIXEDPARENT;
public_area_.objectAttributes |= TPMA_OBJECT_SENSITIVEDATAORIGIN;
public_area_.parameters.symDetail.sym = (TPMT_SYM_DEF_OBJECT) {
.algorithm = TPM2_ALG_AES,
.keyBits.aes = 128, // The default maximum AES key size in the simulator.
.mode.aes = TPM2_ALG_CFB,
};
}
void PrimaryKeyBuilder::UniqueData(const std::string& data) {
if (data.size() > TPM2_SHA256_DIGEST_SIZE) {
LOG(FATAL) << "Unique data size was too large";
}
/* The unique field normally has a precise size to go with the type of the
* object. During primary key creation the unique field accepts any short byte
* string to let the user introduce variability into the primary key creation
* process which is otherwise determinstic relative to secret TPM state. */
public_area_.unique.sym.size = data.size();
memcpy(&public_area_.unique.sym.buffer, data.data(), data.size());
}
TpmObjectSlot PrimaryKeyBuilder::CreateKey(
TpmResourceManager& resource_manager) {
TPM2B_AUTH authValue = {};
auto rc =
Esys_TR_SetAuth(resource_manager.Esys(), ESYS_TR_RH_OWNER, &authValue);
if (rc != TSS2_RC_SUCCESS) {
LOG(ERROR) << "Esys_TR_SetAuth failed with return code " << rc
<< " (" << Tss2_RC_Decode(rc) << ")";
return {};
}
TPM2B_TEMPLATE public_template = {};
size_t offset = 0;
rc = Tss2_MU_TPMT_PUBLIC_Marshal(&public_area_, &public_template.buffer[0],
sizeof(public_template.buffer), &offset);
if (rc != TSS2_RC_SUCCESS) {
LOG(ERROR) << "Tss2_MU_TPMT_PUBLIC_Marshal failed with return code " << rc
<< " (" << Tss2_RC_Decode(rc) << ")";
return {};
}
public_template.size = offset;
TPM2B_SENSITIVE_CREATE in_sensitive = {};
auto key_slot = resource_manager.ReserveSlot();
if (!key_slot) {
LOG(ERROR) << "No slots available";
return {};
}
ESYS_TR raw_handle;
// TODO(b/154956668): Define better ACLs on these keys.
// Since this is a primary key, it's generated deterministically. It would
// also be possible to generate this once and hold it in storage.
rc = Esys_CreateLoaded(
/* esysContext */ resource_manager.Esys(),
/* primaryHandle */ ESYS_TR_RH_OWNER,
/* shandle1 */ ESYS_TR_PASSWORD,
/* shandle2 */ ESYS_TR_NONE,
/* shandle3 */ ESYS_TR_NONE,
/* inSensitive */ &in_sensitive,
/* inPublic */ &public_template,
/* objectHandle */ &raw_handle,
/* outPrivate */ nullptr,
/* outPublic */ nullptr);
if (rc != TSS2_RC_SUCCESS) {
LOG(ERROR) << "Esys_CreateLoaded failed with return code " << rc
<< " (" << Tss2_RC_Decode(rc) << ")";
return {};
}
key_slot->set(raw_handle);
return key_slot;
}
std::function<TpmObjectSlot(TpmResourceManager&)>
SigningKeyCreator(const std::string& unique) {
return [unique](TpmResourceManager& resource_manager) {
PrimaryKeyBuilder key_builder;
key_builder.SigningKey();
key_builder.UniqueData(unique);
return key_builder.CreateKey(resource_manager);
};
}
std::function<TpmObjectSlot(TpmResourceManager&)>
ParentKeyCreator(const std::string& unique) {
return [unique](TpmResourceManager& resource_manager) {
PrimaryKeyBuilder key_builder;
key_builder.ParentKey();
key_builder.UniqueData(unique);
return key_builder.CreateKey(resource_manager);
};
}
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