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/*
* Copyright (c) 2022 Project CHIP Authors
* All rights reserved.
*
* 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 <crypto/OperationalKeystore.h>
#include <lib/core/CHIPError.h>
#include <lib/core/CHIPPersistentStorageDelegate.h>
#include <lib/core/CHIPTLV.h>
#include <lib/core/DataModelTypes.h>
#include <lib/support/CHIPMem.h>
#include <lib/support/CodeUtils.h>
#include <lib/support/DefaultStorageKeyAllocator.h>
#include <lib/support/SafeInt.h>
#include "PersistentStorageOperationalKeystore.h"
namespace chip {
using namespace chip::Crypto;
namespace {
// Tags for our operational keypair storage.
constexpr TLV::Tag kOpKeyVersionTag = TLV::ContextTag(0);
constexpr TLV::Tag kOpKeyDataTag = TLV::ContextTag(1);
// If this version grows beyond UINT16_MAX, adjust OpKeypairTLVMaxSize
// accordingly.
constexpr uint16_t kOpKeyVersion = 1;
constexpr size_t OpKeyTLVMaxSize()
{
// Version and serialized key
return TLV::EstimateStructOverhead(sizeof(uint16_t), Crypto::P256SerializedKeypair::Capacity());
}
/** WARNING: This can leave the operational key on the stack somewhere, since many of the platform
* APIs use stack buffers and do not sanitize! This implementation is for example purposes
* only of the API and it is recommended to avoid directly accessing raw private key bits
* in storage.
*/
CHIP_ERROR StoreOperationalKey(FabricIndex fabricIndex, PersistentStorageDelegate * storage, P256Keypair * keypair)
{
VerifyOrReturnError(IsValidFabricIndex(fabricIndex) && (storage != nullptr) && (keypair != nullptr),
CHIP_ERROR_INVALID_ARGUMENT);
// Use a CapacityBoundBuffer to get RAII secret data clearing on scope exit.
Crypto::CapacityBoundBuffer<OpKeyTLVMaxSize()> buf;
TLV::TLVWriter writer;
writer.Init(buf.Bytes(), buf.Capacity());
TLV::TLVType outerType;
ReturnErrorOnFailure(writer.StartContainer(TLV::AnonymousTag(), TLV::kTLVType_Structure, outerType));
ReturnErrorOnFailure(writer.Put(kOpKeyVersionTag, kOpKeyVersion));
{
// P256SerializedKeypair has RAII secret clearing
Crypto::P256SerializedKeypair serializedOpKey;
ReturnErrorOnFailure(keypair->Serialize(serializedOpKey));
ReturnErrorOnFailure(writer.Put(kOpKeyDataTag, ByteSpan(serializedOpKey.Bytes(), serializedOpKey.Length())));
}
ReturnErrorOnFailure(writer.EndContainer(outerType));
const auto opKeyLength = writer.GetLengthWritten();
VerifyOrReturnError(CanCastTo<uint16_t>(opKeyLength), CHIP_ERROR_BUFFER_TOO_SMALL);
ReturnErrorOnFailure(storage->SyncSetKeyValue(DefaultStorageKeyAllocator::FabricOpKey(fabricIndex).KeyName(), buf,
static_cast<uint16_t>(opKeyLength)));
return CHIP_NO_ERROR;
}
/** WARNING: This can leave the operational key on the stack somewhere, since many of the platform
* APIs use stack buffers and do not sanitize! This implementation is for example purposes
* only of the API and it is recommended to avoid directly accessing raw private key bits
* in storage.
*/
CHIP_ERROR SignWithStoredOpKey(FabricIndex fabricIndex, PersistentStorageDelegate * storage, const ByteSpan & message,
P256ECDSASignature & outSignature)
{
VerifyOrReturnError(IsValidFabricIndex(fabricIndex) && (storage != nullptr), CHIP_ERROR_INVALID_ARGUMENT);
// Use RAII scoping for the transient keypair, to make sure it doesn't get leaked on any error paths.
// Key is put in heap since signature is a costly stack operation and P256Keypair is
// a costly class depending on the backend.
auto transientOperationalKeypair = Platform::MakeUnique<P256Keypair>();
if (!transientOperationalKeypair)
{
return CHIP_ERROR_NO_MEMORY;
}
// Scope 1: Load up the keypair data from storage
{
// Use a CapacityBoundBuffer to get RAII secret data clearing on scope exit.
Crypto::CapacityBoundBuffer<OpKeyTLVMaxSize()> buf;
// Load up the operational key structure from storage
uint16_t size = static_cast<uint16_t>(buf.Capacity());
CHIP_ERROR err =
storage->SyncGetKeyValue(DefaultStorageKeyAllocator::FabricOpKey(fabricIndex).KeyName(), buf.Bytes(), size);
if (err == CHIP_ERROR_PERSISTED_STORAGE_VALUE_NOT_FOUND)
{
err = CHIP_ERROR_INVALID_FABRIC_INDEX;
}
ReturnErrorOnFailure(err);
buf.SetLength(static_cast<size_t>(size));
// Read-out the operational key TLV entry.
TLV::ContiguousBufferTLVReader reader;
reader.Init(buf.Bytes(), buf.Length());
ReturnErrorOnFailure(reader.Next(TLV::kTLVType_Structure, TLV::AnonymousTag()));
TLV::TLVType containerType;
ReturnErrorOnFailure(reader.EnterContainer(containerType));
ReturnErrorOnFailure(reader.Next(kOpKeyVersionTag));
uint16_t opKeyVersion;
ReturnErrorOnFailure(reader.Get(opKeyVersion));
VerifyOrReturnError(opKeyVersion == kOpKeyVersion, CHIP_ERROR_VERSION_MISMATCH);
ReturnErrorOnFailure(reader.Next(kOpKeyDataTag));
{
ByteSpan keyData;
Crypto::P256SerializedKeypair serializedOpKey;
ReturnErrorOnFailure(reader.GetByteView(keyData));
// Unfortunately, we have to copy the data into a P256SerializedKeypair.
VerifyOrReturnError(keyData.size() <= serializedOpKey.Capacity(), CHIP_ERROR_BUFFER_TOO_SMALL);
// Before doing anything with the key, validate format further.
ReturnErrorOnFailure(reader.ExitContainer(containerType));
ReturnErrorOnFailure(reader.VerifyEndOfContainer());
memcpy(serializedOpKey.Bytes(), keyData.data(), keyData.size());
serializedOpKey.SetLength(keyData.size());
// Load-up key material
// WARNING: This makes use of the raw key bits
ReturnErrorOnFailure(transientOperationalKeypair->Deserialize(serializedOpKey));
}
}
// Scope 2: Sign message with the keypair
return transientOperationalKeypair->ECDSA_sign_msg(message.data(), message.size(), outSignature);
}
} // namespace
bool PersistentStorageOperationalKeystore::HasOpKeypairForFabric(FabricIndex fabricIndex) const
{
VerifyOrReturnError(mStorage != nullptr, false);
VerifyOrReturnError(IsValidFabricIndex(fabricIndex), false);
// If there was a pending keypair, then there's really a usable key
if (mIsPendingKeypairActive && (fabricIndex == mPendingFabricIndex) && (mPendingKeypair != nullptr))
{
return true;
}
// TODO(#16958): need to actually read the key to know if it's there due to platforms not
// properly enforcing CHIP_ERROR_BUFFER_TOO_SMALL behavior needed by
// PersistentStorageDelegate. Very unfortunate, needs fixing ASAP.
// Use a CapacityBoundBuffer to get RAII secret data clearing on scope exit.
Crypto::CapacityBoundBuffer<OpKeyTLVMaxSize()> buf;
uint16_t keySize = static_cast<uint16_t>(buf.Capacity());
CHIP_ERROR err =
mStorage->SyncGetKeyValue(DefaultStorageKeyAllocator::FabricOpKey(fabricIndex).KeyName(), buf.Bytes(), keySize);
return (err == CHIP_NO_ERROR);
}
CHIP_ERROR PersistentStorageOperationalKeystore::NewOpKeypairForFabric(FabricIndex fabricIndex,
MutableByteSpan & outCertificateSigningRequest)
{
VerifyOrReturnError(mStorage != nullptr, CHIP_ERROR_INCORRECT_STATE);
VerifyOrReturnError(IsValidFabricIndex(fabricIndex), CHIP_ERROR_INVALID_FABRIC_INDEX);
// If a key is pending, we cannot generate for a different fabric index until we commit or revert.
if ((mPendingFabricIndex != kUndefinedFabricIndex) && (fabricIndex != mPendingFabricIndex))
{
return CHIP_ERROR_INVALID_FABRIC_INDEX;
}
VerifyOrReturnError(outCertificateSigningRequest.size() >= Crypto::kMAX_CSR_Length, CHIP_ERROR_BUFFER_TOO_SMALL);
// Replace previous pending keypair, if any was previously allocated
ResetPendingKey();
mPendingKeypair = Platform::New<Crypto::P256Keypair>();
VerifyOrReturnError(mPendingKeypair != nullptr, CHIP_ERROR_NO_MEMORY);
mPendingKeypair->Initialize();
size_t csrLength = outCertificateSigningRequest.size();
CHIP_ERROR err = mPendingKeypair->NewCertificateSigningRequest(outCertificateSigningRequest.data(), csrLength);
if (err != CHIP_NO_ERROR)
{
ResetPendingKey();
return err;
}
outCertificateSigningRequest.reduce_size(csrLength);
mPendingFabricIndex = fabricIndex;
return CHIP_NO_ERROR;
}
CHIP_ERROR PersistentStorageOperationalKeystore::ActivateOpKeypairForFabric(FabricIndex fabricIndex,
const Crypto::P256PublicKey & nocPublicKey)
{
VerifyOrReturnError(mStorage != nullptr, CHIP_ERROR_INCORRECT_STATE);
VerifyOrReturnError(mPendingKeypair != nullptr, CHIP_ERROR_INVALID_FABRIC_INDEX);
VerifyOrReturnError(IsValidFabricIndex(fabricIndex) && (fabricIndex == mPendingFabricIndex), CHIP_ERROR_INVALID_FABRIC_INDEX);
// Validate public key being activated matches last generated pending keypair
VerifyOrReturnError(mPendingKeypair->Pubkey().Matches(nocPublicKey), CHIP_ERROR_INVALID_PUBLIC_KEY);
mIsPendingKeypairActive = true;
return CHIP_NO_ERROR;
}
CHIP_ERROR PersistentStorageOperationalKeystore::CommitOpKeypairForFabric(FabricIndex fabricIndex)
{
VerifyOrReturnError(mStorage != nullptr, CHIP_ERROR_INCORRECT_STATE);
VerifyOrReturnError(mPendingKeypair != nullptr, CHIP_ERROR_INVALID_FABRIC_INDEX);
VerifyOrReturnError(IsValidFabricIndex(fabricIndex) && (fabricIndex == mPendingFabricIndex), CHIP_ERROR_INVALID_FABRIC_INDEX);
VerifyOrReturnError(mIsPendingKeypairActive == true, CHIP_ERROR_INCORRECT_STATE);
// Try to store persistent key. On failure, leave everything pending as-is
CHIP_ERROR err = StoreOperationalKey(fabricIndex, mStorage, mPendingKeypair);
ReturnErrorOnFailure(err);
// If we got here, we succeeded and can reset the pending key: next `SignWithOpKeypair` will use the stored key.
ResetPendingKey();
return CHIP_NO_ERROR;
}
CHIP_ERROR PersistentStorageOperationalKeystore::RemoveOpKeypairForFabric(FabricIndex fabricIndex)
{
VerifyOrReturnError(mStorage != nullptr, CHIP_ERROR_INCORRECT_STATE);
VerifyOrReturnError(IsValidFabricIndex(fabricIndex), CHIP_ERROR_INVALID_FABRIC_INDEX);
// Remove pending state if matching
if ((mPendingKeypair != nullptr) && (fabricIndex == mPendingFabricIndex))
{
RevertPendingKeypair();
}
CHIP_ERROR err = mStorage->SyncDeleteKeyValue(DefaultStorageKeyAllocator::FabricOpKey(fabricIndex).KeyName());
if (err == CHIP_ERROR_PERSISTED_STORAGE_VALUE_NOT_FOUND)
{
err = CHIP_ERROR_INVALID_FABRIC_INDEX;
}
return err;
}
void PersistentStorageOperationalKeystore::RevertPendingKeypair()
{
VerifyOrReturn(mStorage != nullptr);
// Just reset the pending key, we never stored anything
ResetPendingKey();
}
CHIP_ERROR PersistentStorageOperationalKeystore::SignWithOpKeypair(FabricIndex fabricIndex, const ByteSpan & message,
Crypto::P256ECDSASignature & outSignature) const
{
VerifyOrReturnError(mStorage != nullptr, CHIP_ERROR_INCORRECT_STATE);
VerifyOrReturnError(IsValidFabricIndex(fabricIndex), CHIP_ERROR_INVALID_FABRIC_INDEX);
if (mIsPendingKeypairActive && (fabricIndex == mPendingFabricIndex))
{
VerifyOrReturnError(mPendingKeypair != nullptr, CHIP_ERROR_INTERNAL);
// We have an override key: sign with it!
return mPendingKeypair->ECDSA_sign_msg(message.data(), message.size(), outSignature);
}
return SignWithStoredOpKey(fabricIndex, mStorage, message, outSignature);
}
Crypto::P256Keypair * PersistentStorageOperationalKeystore::AllocateEphemeralKeypairForCASE()
{
// DO NOT CUT AND PASTE without considering the ReleaseEphemeralKeypair().
// If allocating a derived class, then `ReleaseEphemeralKeypair` MUST
// de-allocate the derived class after up-casting the base class pointer.
return Platform::New<Crypto::P256Keypair>();
}
void PersistentStorageOperationalKeystore::ReleaseEphemeralKeypair(Crypto::P256Keypair * keypair)
{
// DO NOT CUT AND PASTE without considering the AllocateEphemeralKeypairForCASE().
// This must delete the same concrete class as allocated in `AllocateEphemeralKeypairForCASE`
Platform::Delete<Crypto::P256Keypair>(keypair);
}
} // namespace chip