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CASESession.cpp
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CASESession.cpp
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/*
*
* Copyright (c) 2021-2022 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.
*/
/**
* @file
* This file implements the the CHIP CASE Session object that provides
* APIs for constructing a secure session using a certificate from the device's
* operational credentials.
*
*/
#include <protocols/secure_channel/CASESession.h>
#include <atomic>
#include <inttypes.h>
#include <memory>
#include <string.h>
#include <lib/core/CHIPEncoding.h>
#include <lib/core/CHIPSafeCasts.h>
#include <lib/support/CHIPMem.h>
#include <lib/support/CodeUtils.h>
#include <lib/support/SafeInt.h>
#include <lib/support/ScopedBuffer.h>
#include <lib/support/TypeTraits.h>
#include <platform/PlatformManager.h>
#include <protocols/Protocols.h>
#include <protocols/secure_channel/CASEDestinationId.h>
#include <protocols/secure_channel/PairingSession.h>
#include <protocols/secure_channel/SessionResumptionStorage.h>
#include <protocols/secure_channel/StatusReport.h>
#include <system/SystemClock.h>
#include <system/TLVPacketBufferBackingStore.h>
#include <trace/trace.h>
#include <tracing/scope.h>
#include <transport/SessionManager.h>
#if CHIP_CRYPTO_HSM
#include <crypto/hsm/CHIPCryptoPALHsm.h>
#endif
namespace {
enum
{
kTag_TBEData_SenderNOC = 1,
kTag_TBEData_SenderICAC = 2,
kTag_TBEData_Signature = 3,
kTag_TBEData_ResumptionID = 4,
};
enum
{
kTag_TBSData_SenderNOC = 1,
kTag_TBSData_SenderICAC = 2,
kTag_TBSData_SenderPubKey = 3,
kTag_TBSData_ReceiverPubKey = 4,
};
enum
{
kTag_Sigma1_InitiatorRandom = 1,
kTag_Sigma1_InitiatorSessionId = 2,
kTag_Sigma1_DestinationId = 3,
kTag_Sigma1_InitiatorEphPubKey = 4,
kTag_Sigma1_InitiatorMRPParams = 5,
kTag_Sigma1_ResumptionID = 6,
kTag_Sigma1_InitiatorResumeMIC = 7,
};
enum
{
kTag_Sigma2_ResponderRandom = 1,
kTag_Sigma2_ResponderSessionId = 2,
kTag_Sigma2_ResponderEphPubKey = 3,
kTag_Sigma2_Encrypted2 = 4,
kTag_Sigma2_ResponderMRPParams = 5,
};
enum
{
kTag_Sigma3_Encrypted3 = 1,
};
} // namespace
namespace chip {
using namespace Crypto;
using namespace Credentials;
using namespace Messaging;
using namespace Encoding;
using namespace Protocols::SecureChannel;
constexpr uint8_t kKDFSR2Info[] = { 0x53, 0x69, 0x67, 0x6d, 0x61, 0x32 };
constexpr uint8_t kKDFSR3Info[] = { 0x53, 0x69, 0x67, 0x6d, 0x61, 0x33 };
constexpr uint8_t kKDFS1RKeyInfo[] = { 0x53, 0x69, 0x67, 0x6d, 0x61, 0x31, 0x5f, 0x52, 0x65, 0x73, 0x75, 0x6d, 0x65 };
constexpr uint8_t kKDFS2RKeyInfo[] = { 0x53, 0x69, 0x67, 0x6d, 0x61, 0x32, 0x5f, 0x52, 0x65, 0x73, 0x75, 0x6d, 0x65 };
constexpr uint8_t kResume1MIC_Nonce[] =
/* "NCASE_SigmaS1" */ { 0x4e, 0x43, 0x41, 0x53, 0x45, 0x5f, 0x53, 0x69, 0x67, 0x6d, 0x61, 0x53, 0x31 };
constexpr uint8_t kResume2MIC_Nonce[] =
/* "NCASE_SigmaS2" */ { 0x4e, 0x43, 0x41, 0x53, 0x45, 0x5f, 0x53, 0x69, 0x67, 0x6d, 0x61, 0x53, 0x32 };
constexpr uint8_t kTBEData2_Nonce[] =
/* "NCASE_Sigma2N" */ { 0x4e, 0x43, 0x41, 0x53, 0x45, 0x5f, 0x53, 0x69, 0x67, 0x6d, 0x61, 0x32, 0x4e };
constexpr uint8_t kTBEData3_Nonce[] =
/* "NCASE_Sigma3N" */ { 0x4e, 0x43, 0x41, 0x53, 0x45, 0x5f, 0x53, 0x69, 0x67, 0x6d, 0x61, 0x33, 0x4e };
constexpr size_t kTBEDataNonceLength = sizeof(kTBEData2_Nonce);
static_assert(sizeof(kTBEData2_Nonce) == sizeof(kTBEData3_Nonce), "TBEData2_Nonce and TBEData3_Nonce must be same size");
// Amounts of time to allow for server-side processing of messages.
//
// These timeout values only allow for the server-side processing and assume that any transport-specific
// latency will be added to them.
//
// The session establishment fails if the response is not received within the resulting timeout window,
// which accounts for both transport latency and the server-side latency.
static constexpr ExchangeContext::Timeout kExpectedLowProcessingTime = System::Clock::Seconds16(2);
static constexpr ExchangeContext::Timeout kExpectedSigma1ProcessingTime = kExpectedLowProcessingTime;
static constexpr ExchangeContext::Timeout kExpectedHighProcessingTime = System::Clock::Seconds16(30);
// Helper for managing a session's outstanding work.
// Holds work data which is provided to a scheduled work callback (standalone),
// then (if not canceled) to a scheduled after work callback (on the session).
template <class DATA>
class CASESession::WorkHelper
{
public:
// Work callback, processed in the background via `PlatformManager::ScheduleBackgroundWork`.
// This is a non-member function which does not use the associated session.
// The return value is passed to the after work callback (called afterward).
// Set `cancel` to true if calling the after work callback is not necessary.
typedef CHIP_ERROR (*WorkCallback)(DATA & data, bool & cancel);
// After work callback, processed in the main Matter task via `PlatformManager::ScheduleWork`.
// This is a member function to be called on the associated session after the work callback.
// The `status` value is the result of the work callback (called beforehand).
typedef CHIP_ERROR (CASESession::*AfterWorkCallback)(DATA & data, CHIP_ERROR status);
public:
// Create a work helper using the specified session, work callback, after work callback, and data (template arg).
// Lifetime is managed by sharing between the caller (typically the session) and the helper itself (while work is scheduled).
static Platform::SharedPtr<WorkHelper> Create(CASESession & session, WorkCallback workCallback,
AfterWorkCallback afterWorkCallback)
{
struct EnableShared : public WorkHelper
{
EnableShared(CASESession & session, WorkCallback workCallback, AfterWorkCallback afterWorkCallback) :
WorkHelper(session, workCallback, afterWorkCallback)
{}
};
auto ptr = Platform::MakeShared<EnableShared>(session, workCallback, afterWorkCallback);
if (ptr)
{
ptr->mWeakPtr = ptr; // used by `ScheduleWork`
}
return ptr;
}
// Do the work immediately.
// No scheduling, no outstanding work, no shared lifetime management.
CHIP_ERROR DoWork()
{
VerifyOrReturnError(mSession && mWorkCallback && mAfterWorkCallback, CHIP_ERROR_INCORRECT_STATE);
auto * helper = this;
bool cancel = false;
helper->mStatus = helper->mWorkCallback(helper->mData, cancel);
if (!cancel)
{
helper->mStatus = (helper->mSession->*(helper->mAfterWorkCallback))(helper->mData, helper->mStatus);
}
return helper->mStatus;
}
// Schedule the work for later execution.
// If lifetime is managed, the helper shares management while work is outstanding.
CHIP_ERROR ScheduleWork()
{
VerifyOrReturnError(mSession && mWorkCallback && mAfterWorkCallback, CHIP_ERROR_INCORRECT_STATE);
// Hold strong ptr while work is outstanding
mStrongPtr = mWeakPtr.lock(); // set in `Create`
auto status = DeviceLayer::PlatformMgr().ScheduleBackgroundWork(WorkHandler, reinterpret_cast<intptr_t>(this));
if (status != CHIP_NO_ERROR)
{
// Release strong ptr since scheduling failed
mStrongPtr.reset();
}
return status;
}
// Cancel the work, by clearing the associated session.
void CancelWork() { mSession.store(nullptr); }
bool IsCancelled() const { return mSession.load() == nullptr; }
private:
// Create a work helper using the specified session, work callback, after work callback, and data (template arg).
// Lifetime is not managed, see `Create` for that option.
WorkHelper(CASESession & session, WorkCallback workCallback, AfterWorkCallback afterWorkCallback) :
mSession(&session), mWorkCallback(workCallback), mAfterWorkCallback(afterWorkCallback)
{}
// Handler for the work callback.
static void WorkHandler(intptr_t arg)
{
auto * helper = reinterpret_cast<WorkHelper *>(arg);
// Hold strong ptr while work is handled
auto strongPtr(std::move(helper->mStrongPtr));
VerifyOrReturn(!helper->IsCancelled());
bool cancel = false;
// Execute callback in background thread; data must be OK with this
helper->mStatus = helper->mWorkCallback(helper->mData, cancel);
VerifyOrReturn(!cancel && !helper->IsCancelled());
// Hold strong ptr while work is outstanding
helper->mStrongPtr.swap(strongPtr);
auto status = DeviceLayer::PlatformMgr().ScheduleWork(AfterWorkHandler, reinterpret_cast<intptr_t>(helper));
if (status != CHIP_NO_ERROR)
{
// Release strong ptr since scheduling failed
helper->mStrongPtr.reset();
}
}
// Handler for the after work callback.
static void AfterWorkHandler(intptr_t arg)
{
auto * helper = reinterpret_cast<WorkHelper *>(arg);
// Hold strong ptr while work is handled
auto strongPtr(std::move(helper->mStrongPtr));
if (auto * session = helper->mSession.load())
{
// Execute callback in Matter thread; session should be OK with this
(session->*(helper->mAfterWorkCallback))(helper->mData, helper->mStatus);
}
}
private:
// Lifetime management: `ScheduleWork` sets `mStrongPtr` from `mWeakPtr`.
Platform::WeakPtr<WorkHelper> mWeakPtr;
// Lifetime management: `ScheduleWork` sets `mStrongPtr` from `mWeakPtr`.
Platform::SharedPtr<WorkHelper> mStrongPtr;
// Associated session, cleared by `CancelWork`.
std::atomic<CASESession *> mSession;
// Work callback, called by `WorkHandler`.
WorkCallback mWorkCallback;
// After work callback, called by `AfterWorkHandler`.
AfterWorkCallback mAfterWorkCallback;
// Return value of `mWorkCallback`, passed to `mAfterWorkCallback`.
CHIP_ERROR mStatus;
public:
// Data passed to `mWorkCallback` and `mAfterWorkCallback`.
DATA mData;
};
struct CASESession::SendSigma3Data
{
FabricIndex fabricIndex;
// Use one or the other
const FabricTable * fabricTable;
const Crypto::OperationalKeystore * keystore;
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R3_Signed;
size_t msg_r3_signed_len;
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R3_Encrypted;
size_t msg_r3_encrypted_len;
chip::Platform::ScopedMemoryBuffer<uint8_t> icacBuf;
MutableByteSpan icaCert;
chip::Platform::ScopedMemoryBuffer<uint8_t> nocBuf;
MutableByteSpan nocCert;
P256ECDSASignature tbsData3Signature;
};
struct CASESession::HandleSigma3Data
{
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R3_Signed;
size_t msg_r3_signed_len;
ByteSpan initiatorNOC;
ByteSpan initiatorICAC;
uint8_t rootCertBuf[kMaxCHIPCertLength];
ByteSpan fabricRCAC;
P256ECDSASignature tbsData3Signature;
FabricId fabricId;
NodeId initiatorNodeId;
ValidationContext validContext;
};
CASESession::~CASESession()
{
// Let's clear out any security state stored in the object, before destroying it.
Clear();
}
void CASESession::OnSessionReleased()
{
// Call into our super-class before we clear our state.
PairingSession::OnSessionReleased();
Clear();
}
void CASESession::Clear()
{
// Cancel any outstanding work.
if (mSendSigma3Helper)
{
mSendSigma3Helper->CancelWork();
mSendSigma3Helper.reset();
}
if (mHandleSigma3Helper)
{
mHandleSigma3Helper->CancelWork();
mHandleSigma3Helper.reset();
}
// This function zeroes out and resets the memory used by the object.
// It's done so that no security related information will be leaked.
mCommissioningHash.Clear();
PairingSession::Clear();
mState = State::kInitialized;
Crypto::ClearSecretData(mIPK);
if (mFabricsTable != nullptr)
{
mFabricsTable->RemoveFabricDelegate(this);
mFabricsTable->ReleaseEphemeralKeypair(mEphemeralKey);
mEphemeralKey = nullptr;
}
mLocalNodeId = kUndefinedNodeId;
mPeerNodeId = kUndefinedNodeId;
mFabricsTable = nullptr;
mFabricIndex = kUndefinedFabricIndex;
}
void CASESession::InvalidateIfPendingEstablishmentOnFabric(FabricIndex fabricIndex)
{
if (mFabricIndex != fabricIndex)
{
return;
}
if (!IsSessionEstablishmentInProgress())
{
return;
}
AbortPendingEstablish(CHIP_ERROR_CANCELLED);
}
CHIP_ERROR CASESession::Init(SessionManager & sessionManager, Credentials::CertificateValidityPolicy * policy,
SessionEstablishmentDelegate * delegate, const ScopedNodeId & sessionEvictionHint)
{
VerifyOrReturnError(delegate != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
VerifyOrReturnError(mGroupDataProvider != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
VerifyOrReturnError(sessionManager.GetSessionKeystore() != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
Clear();
ReturnErrorOnFailure(mCommissioningHash.Begin());
mDelegate = delegate;
ReturnErrorOnFailure(AllocateSecureSession(sessionManager, sessionEvictionHint));
mValidContext.Reset();
mValidContext.mRequiredKeyUsages.Set(KeyUsageFlags::kDigitalSignature);
mValidContext.mRequiredKeyPurposes.Set(KeyPurposeFlags::kServerAuth);
mValidContext.mValidityPolicy = policy;
return CHIP_NO_ERROR;
}
CHIP_ERROR
CASESession::PrepareForSessionEstablishment(SessionManager & sessionManager, FabricTable * fabricTable,
SessionResumptionStorage * sessionResumptionStorage,
Credentials::CertificateValidityPolicy * policy,
SessionEstablishmentDelegate * delegate, const ScopedNodeId & previouslyEstablishedPeer,
Optional<ReliableMessageProtocolConfig> mrpLocalConfig)
{
// Below VerifyOrReturnError is not SuccessOrExit since we only want to goto `exit:` after
// Init has been successfully called.
VerifyOrReturnError(fabricTable != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
ReturnErrorOnFailure(Init(sessionManager, policy, delegate, previouslyEstablishedPeer));
CHIP_ERROR err = CHIP_NO_ERROR;
SuccessOrExit(err = fabricTable->AddFabricDelegate(this));
mFabricsTable = fabricTable;
mRole = CryptoContext::SessionRole::kResponder;
mSessionResumptionStorage = sessionResumptionStorage;
mLocalMRPConfig = mrpLocalConfig;
ChipLogDetail(SecureChannel, "Allocated SecureSession (%p) - waiting for Sigma1 msg",
mSecureSessionHolder.Get().Value()->AsSecureSession());
exit:
if (err != CHIP_NO_ERROR)
{
Clear();
}
return err;
}
CHIP_ERROR CASESession::EstablishSession(SessionManager & sessionManager, FabricTable * fabricTable, ScopedNodeId peerScopedNodeId,
ExchangeContext * exchangeCtxt, SessionResumptionStorage * sessionResumptionStorage,
Credentials::CertificateValidityPolicy * policy, SessionEstablishmentDelegate * delegate,
Optional<ReliableMessageProtocolConfig> mrpLocalConfig)
{
MATTER_TRACE_EVENT_SCOPE("EstablishSession", "CASESession");
MATTER_TRACE_SCOPE(::chip::Tracing::Scope::CASESession_EstablishSession);
CHIP_ERROR err = CHIP_NO_ERROR;
// Return early on error here, as we have not initialized any state yet
ReturnErrorCodeIf(exchangeCtxt == nullptr, CHIP_ERROR_INVALID_ARGUMENT);
ReturnErrorCodeIf(fabricTable == nullptr, CHIP_ERROR_INVALID_ARGUMENT);
// Use FabricTable directly to avoid situation of dangling index from stale FabricInfo
// until we factor-out any FabricInfo direct usage.
ReturnErrorCodeIf(peerScopedNodeId.GetFabricIndex() == kUndefinedFabricIndex, CHIP_ERROR_INVALID_ARGUMENT);
const auto * fabricInfo = fabricTable->FindFabricWithIndex(peerScopedNodeId.GetFabricIndex());
ReturnErrorCodeIf(fabricInfo == nullptr, CHIP_ERROR_INVALID_ARGUMENT);
err = Init(sessionManager, policy, delegate, peerScopedNodeId);
mRole = CryptoContext::SessionRole::kInitiator;
// We are setting the exchange context specifically before checking for error.
// This is to make sure the exchange will get closed if Init() returned an error.
mExchangeCtxt = exchangeCtxt;
// From here onwards, let's go to exit on error, as some state might have already
// been initialized
SuccessOrExit(err);
SuccessOrExit(err = fabricTable->AddFabricDelegate(this));
mFabricsTable = fabricTable;
mFabricIndex = fabricInfo->GetFabricIndex();
mSessionResumptionStorage = sessionResumptionStorage;
mLocalMRPConfig = mrpLocalConfig;
mExchangeCtxt->UseSuggestedResponseTimeout(kExpectedSigma1ProcessingTime);
mPeerNodeId = peerScopedNodeId.GetNodeId();
mLocalNodeId = fabricInfo->GetNodeId();
ChipLogProgress(SecureChannel, "Initiating session on local FabricIndex %u from 0x" ChipLogFormatX64 " -> 0x" ChipLogFormatX64,
static_cast<unsigned>(mFabricIndex), ChipLogValueX64(mLocalNodeId), ChipLogValueX64(mPeerNodeId));
err = SendSigma1();
SuccessOrExit(err);
exit:
if (err != CHIP_NO_ERROR)
{
Clear();
}
return err;
}
void CASESession::OnResponseTimeout(ExchangeContext * ec)
{
VerifyOrReturn(ec != nullptr, ChipLogError(SecureChannel, "CASESession::OnResponseTimeout was called by null exchange"));
VerifyOrReturn(mExchangeCtxt == ec, ChipLogError(SecureChannel, "CASESession::OnResponseTimeout exchange doesn't match"));
ChipLogError(SecureChannel, "CASESession timed out while waiting for a response from the peer. Current state was %u",
to_underlying(mState));
// Discard the exchange so that Clear() doesn't try aborting it. The
// exchange will handle that.
DiscardExchange();
AbortPendingEstablish(CHIP_ERROR_TIMEOUT);
}
void CASESession::AbortPendingEstablish(CHIP_ERROR err)
{
Clear();
// Do this last in case the delegate frees us.
NotifySessionEstablishmentError(err);
}
CHIP_ERROR CASESession::DeriveSecureSession(CryptoContext & session) const
{
switch (mState)
{
case State::kFinished: {
std::array<uint8_t, sizeof(mIPK) + kSHA256_Hash_Length> msg_salt;
{
Encoding::LittleEndian::BufferWriter bbuf(msg_salt);
bbuf.Put(mIPK, sizeof(mIPK));
bbuf.Put(mMessageDigest, sizeof(mMessageDigest));
VerifyOrReturnError(bbuf.Fit(), CHIP_ERROR_BUFFER_TOO_SMALL);
}
ReturnErrorOnFailure(session.InitFromSecret(*mSessionManager->GetSessionKeystore(), mSharedSecret.Span(),
ByteSpan(msg_salt), CryptoContext::SessionInfoType::kSessionEstablishment,
mRole));
return CHIP_NO_ERROR;
}
case State::kFinishedViaResume: {
std::array<uint8_t, sizeof(mInitiatorRandom) + decltype(mResumeResumptionId)().size()> msg_salt;
{
Encoding::LittleEndian::BufferWriter bbuf(msg_salt);
bbuf.Put(mInitiatorRandom, sizeof(mInitiatorRandom));
bbuf.Put(mResumeResumptionId.data(), mResumeResumptionId.size());
VerifyOrReturnError(bbuf.Fit(), CHIP_ERROR_BUFFER_TOO_SMALL);
}
ReturnErrorOnFailure(session.InitFromSecret(*mSessionManager->GetSessionKeystore(), mSharedSecret.Span(),
ByteSpan(msg_salt), CryptoContext::SessionInfoType::kSessionResumption, mRole));
return CHIP_NO_ERROR;
}
default:
return CHIP_ERROR_INCORRECT_STATE;
}
}
CHIP_ERROR CASESession::RecoverInitiatorIpk()
{
Credentials::GroupDataProvider::KeySet ipkKeySet;
CHIP_ERROR err = mGroupDataProvider->GetIpkKeySet(mFabricIndex, ipkKeySet);
if (err != CHIP_NO_ERROR)
{
ChipLogError(SecureChannel, "Failed to obtain IPK for initiating: %" CHIP_ERROR_FORMAT, err.Format());
return err;
}
if ((ipkKeySet.num_keys_used == 0) || (ipkKeySet.num_keys_used > Credentials::GroupDataProvider::KeySet::kEpochKeysMax))
{
ChipLogError(SecureChannel, "Found invalid IPK keyset for initiator.");
return CHIP_ERROR_INTERNAL;
}
// For the generation of the Destination Identifier,
// the originator SHALL use the operational group key with the second oldest
// EpochStartTime, if one exists, otherwise it SHALL use the single operational
// group key available. The EpochStartTime are already ordered
size_t ipkIndex = (ipkKeySet.num_keys_used > 1) ? ((ipkKeySet.num_keys_used - 1) - 1) : 0;
memcpy(&mIPK[0], ipkKeySet.epoch_keys[ipkIndex].key, sizeof(mIPK));
// Leaving this logging code for debug, but this cannot be enabled at runtime
// since it leaks private security material.
#if 0
ChipLogProgress(SecureChannel, "RecoverInitiatorIpk: GroupDataProvider %p, Got IPK for FabricIndex %u", mGroupDataProvider,
static_cast<unsigned>(mFabricIndex));
ChipLogByteSpan(SecureChannel, ByteSpan(mIPK));
#endif
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::SendSigma1()
{
MATTER_TRACE_EVENT_SCOPE("SendSigma1", "CASESession");
MATTER_TRACE_SCOPE(::chip::Tracing::Scope::CASESession_SendSigma1);
const size_t mrpParamsSize = mLocalMRPConfig.HasValue() ? TLV::EstimateStructOverhead(sizeof(uint16_t), sizeof(uint16_t)) : 0;
size_t data_len = TLV::EstimateStructOverhead(kSigmaParamRandomNumberSize, // initiatorRandom
sizeof(uint16_t), // initiatorSessionId,
kSHA256_Hash_Length, // destinationId
kP256_PublicKey_Length, // InitiatorEphPubKey,
mrpParamsSize, // initiatorMRPParams
SessionResumptionStorage::kResumptionIdSize, CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES);
System::PacketBufferTLVWriter tlvWriter;
System::PacketBufferHandle msg_R1;
TLV::TLVType outerContainerType = TLV::kTLVType_NotSpecified;
uint8_t destinationIdentifier[kSHA256_Hash_Length] = { 0 };
// Lookup fabric info.
const auto * fabricInfo = mFabricsTable->FindFabricWithIndex(mFabricIndex);
ReturnErrorCodeIf(fabricInfo == nullptr, CHIP_ERROR_INCORRECT_STATE);
// Validate that we have a session ID allocated.
VerifyOrReturnError(GetLocalSessionId().HasValue(), CHIP_ERROR_INCORRECT_STATE);
// Generate an ephemeral keypair
mEphemeralKey = mFabricsTable->AllocateEphemeralKeypairForCASE();
VerifyOrReturnError(mEphemeralKey != nullptr, CHIP_ERROR_NO_MEMORY);
ReturnErrorOnFailure(mEphemeralKey->Initialize(ECPKeyTarget::ECDH));
// Fill in the random value
ReturnErrorOnFailure(DRBG_get_bytes(mInitiatorRandom, sizeof(mInitiatorRandom)));
// Construct Sigma1 Msg
msg_R1 = System::PacketBufferHandle::New(data_len);
VerifyOrReturnError(!msg_R1.IsNull(), CHIP_ERROR_NO_MEMORY);
tlvWriter.Init(std::move(msg_R1));
ReturnErrorOnFailure(tlvWriter.StartContainer(TLV::AnonymousTag(), TLV::kTLVType_Structure, outerContainerType));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(1), ByteSpan(mInitiatorRandom)));
// Retrieve Session Identifier
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(2), GetLocalSessionId().Value()));
// Generate a Destination Identifier based on the node we are attempting to reach
{
// Obtain originator IPK matching the fabric where we are trying to open a session. mIPK
// will be properly set thereafter.
ReturnErrorOnFailure(RecoverInitiatorIpk());
FabricId fabricId = fabricInfo->GetFabricId();
Crypto::P256PublicKey rootPubKey;
ReturnErrorOnFailure(mFabricsTable->FetchRootPubkey(mFabricIndex, rootPubKey));
Credentials::P256PublicKeySpan rootPubKeySpan{ rootPubKey.ConstBytes() };
MutableByteSpan destinationIdSpan(destinationIdentifier);
ReturnErrorOnFailure(GenerateCaseDestinationId(ByteSpan(mIPK), ByteSpan(mInitiatorRandom), rootPubKeySpan, fabricId,
mPeerNodeId, destinationIdSpan));
}
ReturnErrorOnFailure(tlvWriter.PutBytes(TLV::ContextTag(3), destinationIdentifier, sizeof(destinationIdentifier)));
ReturnErrorOnFailure(
tlvWriter.PutBytes(TLV::ContextTag(4), mEphemeralKey->Pubkey(), static_cast<uint32_t>(mEphemeralKey->Pubkey().Length())));
if (mLocalMRPConfig.HasValue())
{
ChipLogDetail(SecureChannel, "Including MRP parameters");
ReturnErrorOnFailure(EncodeMRPParameters(TLV::ContextTag(5), mLocalMRPConfig.Value(), tlvWriter));
}
// Try to find persistent session, and resume it.
bool resuming = false;
if (mSessionResumptionStorage != nullptr)
{
CHIP_ERROR err = mSessionResumptionStorage->FindByScopedNodeId(fabricInfo->GetScopedNodeIdForNode(mPeerNodeId),
mResumeResumptionId, mSharedSecret, mPeerCATs);
if (err == CHIP_NO_ERROR)
{
// Found valid resumption state, try to resume the session.
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(6), mResumeResumptionId));
uint8_t initiatorResume1MIC[CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES];
MutableByteSpan resumeMICSpan(initiatorResume1MIC);
ReturnErrorOnFailure(GenerateSigmaResumeMIC(ByteSpan(mInitiatorRandom), ByteSpan(mResumeResumptionId),
ByteSpan(kKDFS1RKeyInfo), ByteSpan(kResume1MIC_Nonce), resumeMICSpan));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(7), resumeMICSpan));
resuming = true;
}
}
ReturnErrorOnFailure(tlvWriter.EndContainer(outerContainerType));
ReturnErrorOnFailure(tlvWriter.Finalize(&msg_R1));
ReturnErrorOnFailure(mCommissioningHash.AddData(ByteSpan{ msg_R1->Start(), msg_R1->DataLength() }));
// Call delegate to send the msg to peer
ReturnErrorOnFailure(mExchangeCtxt->SendMessage(Protocols::SecureChannel::MsgType::CASE_Sigma1, std::move(msg_R1),
SendFlags(SendMessageFlags::kExpectResponse)));
mState = resuming ? State::kSentSigma1Resume : State::kSentSigma1;
ChipLogProgress(SecureChannel, "Sent Sigma1 msg");
mDelegate->OnSessionEstablishmentStarted();
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::HandleSigma1_and_SendSigma2(System::PacketBufferHandle && msg)
{
MATTER_TRACE_EVENT_SCOPE("HandleSigma1_and_SendSigma2", "CASESession");
MATTER_TRACE_SCOPE(::chip::Tracing::Scope::CASESession_HandleSigma1_and_SendSigma2);
ReturnErrorOnFailure(HandleSigma1(std::move(msg)));
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::FindLocalNodeFromDestinationId(const ByteSpan & destinationId, const ByteSpan & initiatorRandom)
{
VerifyOrReturnError(mFabricsTable != nullptr, CHIP_ERROR_INCORRECT_STATE);
bool found = false;
for (const FabricInfo & fabricInfo : *mFabricsTable)
{
// Basic data for candidate fabric, used to compute candidate destination identifiers
FabricId fabricId = fabricInfo.GetFabricId();
NodeId nodeId = fabricInfo.GetNodeId();
Crypto::P256PublicKey rootPubKey;
ReturnErrorOnFailure(mFabricsTable->FetchRootPubkey(fabricInfo.GetFabricIndex(), rootPubKey));
Credentials::P256PublicKeySpan rootPubKeySpan{ rootPubKey.ConstBytes() };
// Get IPK operational group key set for current candidate fabric
GroupDataProvider::KeySet ipkKeySet;
CHIP_ERROR err = mGroupDataProvider->GetIpkKeySet(fabricInfo.GetFabricIndex(), ipkKeySet);
if ((err != CHIP_NO_ERROR) ||
((ipkKeySet.num_keys_used == 0) || (ipkKeySet.num_keys_used > Credentials::GroupDataProvider::KeySet::kEpochKeysMax)))
{
continue;
}
// Try every IPK candidate we have for a match
for (size_t keyIdx = 0; keyIdx < ipkKeySet.num_keys_used; ++keyIdx)
{
uint8_t candidateDestinationId[kSHA256_Hash_Length];
MutableByteSpan candidateDestinationIdSpan(candidateDestinationId);
ByteSpan candidateIpkSpan(ipkKeySet.epoch_keys[keyIdx].key);
err = GenerateCaseDestinationId(ByteSpan(candidateIpkSpan), ByteSpan(initiatorRandom), rootPubKeySpan, fabricId, nodeId,
candidateDestinationIdSpan);
if ((err == CHIP_NO_ERROR) && (candidateDestinationIdSpan.data_equal(destinationId)))
{
// Found a match, stop working, cache IPK, update local fabric context
found = true;
MutableByteSpan ipkSpan(mIPK);
CopySpanToMutableSpan(candidateIpkSpan, ipkSpan);
mFabricIndex = fabricInfo.GetFabricIndex();
mLocalNodeId = nodeId;
break;
}
}
if (found)
{
break;
}
}
return found ? CHIP_NO_ERROR : CHIP_ERROR_KEY_NOT_FOUND;
}
CHIP_ERROR CASESession::TryResumeSession(SessionResumptionStorage::ConstResumptionIdView resumptionId, ByteSpan resume1MIC,
ByteSpan initiatorRandom)
{
VerifyOrReturnError(mSessionResumptionStorage != nullptr, CHIP_ERROR_INCORRECT_STATE);
VerifyOrReturnError(mFabricsTable != nullptr, CHIP_ERROR_INCORRECT_STATE);
SessionResumptionStorage::ConstResumptionIdView resumptionIdSpan(resumptionId);
ScopedNodeId node;
ReturnErrorOnFailure(mSessionResumptionStorage->FindByResumptionId(resumptionIdSpan, node, mSharedSecret, mPeerCATs));
// Cross check resume1MIC with the shared secret
ReturnErrorOnFailure(
ValidateSigmaResumeMIC(resume1MIC, initiatorRandom, resumptionId, ByteSpan(kKDFS1RKeyInfo), ByteSpan(kResume1MIC_Nonce)));
const auto * fabricInfo = mFabricsTable->FindFabricWithIndex(node.GetFabricIndex());
VerifyOrReturnError(fabricInfo != nullptr, CHIP_ERROR_INCORRECT_STATE);
mFabricIndex = node.GetFabricIndex();
mPeerNodeId = node.GetNodeId();
mLocalNodeId = fabricInfo->GetNodeId();
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::HandleSigma1(System::PacketBufferHandle && msg)
{
MATTER_TRACE_EVENT_SCOPE("HandleSigma1", "CASESession");
MATTER_TRACE_SCOPE(::chip::Tracing::Scope::CASESession_HandleSigma1);
CHIP_ERROR err = CHIP_NO_ERROR;
System::PacketBufferTLVReader tlvReader;
uint16_t initiatorSessionId;
ByteSpan destinationIdentifier;
ByteSpan initiatorRandom;
ChipLogProgress(SecureChannel, "Received Sigma1 msg");
bool sessionResumptionRequested = false;
ByteSpan resumptionId;
ByteSpan resume1MIC;
ByteSpan initiatorPubKey;
SuccessOrExit(err = mCommissioningHash.AddData(ByteSpan{ msg->Start(), msg->DataLength() }));
tlvReader.Init(std::move(msg));
SuccessOrExit(err = ParseSigma1(tlvReader, initiatorRandom, initiatorSessionId, destinationIdentifier, initiatorPubKey,
sessionResumptionRequested, resumptionId, resume1MIC));
ChipLogDetail(SecureChannel, "Peer assigned session key ID %d", initiatorSessionId);
SetPeerSessionId(initiatorSessionId);
VerifyOrExit(mFabricsTable != nullptr, err = CHIP_ERROR_INCORRECT_STATE);
if (sessionResumptionRequested && resumptionId.size() == SessionResumptionStorage::kResumptionIdSize &&
CHIP_NO_ERROR ==
TryResumeSession(SessionResumptionStorage::ConstResumptionIdView(resumptionId.data()), resume1MIC, initiatorRandom))
{
std::copy(initiatorRandom.begin(), initiatorRandom.end(), mInitiatorRandom);
std::copy(resumptionId.begin(), resumptionId.end(), mResumeResumptionId.begin());
// Send Sigma2Resume message to the initiator
SuccessOrExit(err = SendSigma2Resume());
mDelegate->OnSessionEstablishmentStarted();
// Early returning here, since we have sent Sigma2Resume, and no further processing is needed for the Sigma1 message
return CHIP_NO_ERROR;
}
// Attempt to match the initiator's desired destination based on local fabric table.
err = FindLocalNodeFromDestinationId(destinationIdentifier, initiatorRandom);
if (err == CHIP_NO_ERROR)
{
ChipLogProgress(SecureChannel, "CASE matched destination ID: fabricIndex %u, NodeID 0x" ChipLogFormatX64,
static_cast<unsigned>(mFabricIndex), ChipLogValueX64(mLocalNodeId));
// Side-effect of FindLocalNodeFromDestinationId success was that mFabricIndex/mLocalNodeId are now
// set to the local fabric and associated NodeId that was targeted by the initiator.
}
else
{
ChipLogError(SecureChannel, "CASE failed to match destination ID with local fabrics");
ChipLogByteSpan(SecureChannel, destinationIdentifier);
}
SuccessOrExit(err);
// ParseSigma1 ensures that:
// mRemotePubKey.Length() == initiatorPubKey.size() == kP256_PublicKey_Length.
memcpy(mRemotePubKey.Bytes(), initiatorPubKey.data(), mRemotePubKey.Length());
SuccessOrExit(err = SendSigma2());
mDelegate->OnSessionEstablishmentStarted();
exit:
if (err == CHIP_ERROR_KEY_NOT_FOUND)
{
SendStatusReport(mExchangeCtxt, kProtocolCodeNoSharedRoot);
mState = State::kInitialized;
}
else if (err != CHIP_NO_ERROR)
{
SendStatusReport(mExchangeCtxt, kProtocolCodeInvalidParam);
mState = State::kInitialized;
}
return err;
}
CHIP_ERROR CASESession::SendSigma2Resume()
{
MATTER_TRACE_EVENT_SCOPE("SendSigma2Resume", "CASESession");
MATTER_TRACE_SCOPE(::chip::Tracing::Scope::CASESession_SendSigma2Resume);
const size_t mrpParamsSize = mLocalMRPConfig.HasValue() ? TLV::EstimateStructOverhead(sizeof(uint16_t), sizeof(uint16_t)) : 0;
size_t max_sigma2_resume_data_len = TLV::EstimateStructOverhead(
SessionResumptionStorage::kResumptionIdSize, CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES, sizeof(uint16_t), mrpParamsSize);
System::PacketBufferTLVWriter tlvWriter;
System::PacketBufferHandle msg_R2_resume;
TLV::TLVType outerContainerType = TLV::kTLVType_NotSpecified;
// Validate that we have a session ID allocated.
VerifyOrReturnError(GetLocalSessionId().HasValue(), CHIP_ERROR_INCORRECT_STATE);
msg_R2_resume = System::PacketBufferHandle::New(max_sigma2_resume_data_len);
VerifyOrReturnError(!msg_R2_resume.IsNull(), CHIP_ERROR_NO_MEMORY);
tlvWriter.Init(std::move(msg_R2_resume));
// Generate a new resumption ID
ReturnErrorOnFailure(DRBG_get_bytes(mNewResumptionId.data(), mNewResumptionId.size()));
ReturnErrorOnFailure(tlvWriter.StartContainer(TLV::AnonymousTag(), TLV::kTLVType_Structure, outerContainerType));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(1), mNewResumptionId));
uint8_t sigma2ResumeMIC[CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES];
MutableByteSpan resumeMICSpan(sigma2ResumeMIC);
ReturnErrorOnFailure(GenerateSigmaResumeMIC(ByteSpan(mInitiatorRandom), mNewResumptionId, ByteSpan(kKDFS2RKeyInfo),
ByteSpan(kResume2MIC_Nonce), resumeMICSpan));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(2), resumeMICSpan));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(3), GetLocalSessionId().Value()));
if (mLocalMRPConfig.HasValue())
{
ChipLogDetail(SecureChannel, "Including MRP parameters");
ReturnErrorOnFailure(EncodeMRPParameters(TLV::ContextTag(4), mLocalMRPConfig.Value(), tlvWriter));
}
ReturnErrorOnFailure(tlvWriter.EndContainer(outerContainerType));
ReturnErrorOnFailure(tlvWriter.Finalize(&msg_R2_resume));
// Call delegate to send the msg to peer
ReturnErrorOnFailure(mExchangeCtxt->SendMessage(Protocols::SecureChannel::MsgType::CASE_Sigma2Resume, std::move(msg_R2_resume),
SendFlags(SendMessageFlags::kExpectResponse)));
mState = State::kSentSigma2Resume;
ChipLogDetail(SecureChannel, "Sent Sigma2Resume msg");
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::SendSigma2()
{
MATTER_TRACE_EVENT_SCOPE("SendSigma2", "CASESession");
MATTER_TRACE_SCOPE(::chip::Tracing::Scope::CASESession_SendSigma2);
VerifyOrReturnError(GetLocalSessionId().HasValue(), CHIP_ERROR_INCORRECT_STATE);
VerifyOrReturnError(mFabricsTable != nullptr, CHIP_ERROR_INCORRECT_STATE);
chip::Platform::ScopedMemoryBuffer<uint8_t> icacBuf;
VerifyOrReturnError(icacBuf.Alloc(kMaxCHIPCertLength), CHIP_ERROR_NO_MEMORY);
chip::Platform::ScopedMemoryBuffer<uint8_t> nocBuf;
VerifyOrReturnError(nocBuf.Alloc(kMaxCHIPCertLength), CHIP_ERROR_NO_MEMORY);
MutableByteSpan icaCert{ icacBuf.Get(), kMaxCHIPCertLength };
ReturnErrorOnFailure(mFabricsTable->FetchICACert(mFabricIndex, icaCert));
MutableByteSpan nocCert{ nocBuf.Get(), kMaxCHIPCertLength };
ReturnErrorOnFailure(mFabricsTable->FetchNOCCert(mFabricIndex, nocCert));
// Fill in the random value
uint8_t msg_rand[kSigmaParamRandomNumberSize];
ReturnErrorOnFailure(DRBG_get_bytes(&msg_rand[0], sizeof(msg_rand)));
// Generate an ephemeral keypair
mEphemeralKey = mFabricsTable->AllocateEphemeralKeypairForCASE();
VerifyOrReturnError(mEphemeralKey != nullptr, CHIP_ERROR_NO_MEMORY);
ReturnErrorOnFailure(mEphemeralKey->Initialize(ECPKeyTarget::ECDH));
// Generate a Shared Secret
ReturnErrorOnFailure(mEphemeralKey->ECDH_derive_secret(mRemotePubKey, mSharedSecret));
uint8_t msg_salt[kIPKSize + kSigmaParamRandomNumberSize + kP256_PublicKey_Length + kSHA256_Hash_Length];
MutableByteSpan saltSpan(msg_salt);
ReturnErrorOnFailure(ConstructSaltSigma2(ByteSpan(msg_rand), mEphemeralKey->Pubkey(), ByteSpan(mIPK), saltSpan));
AutoReleaseSessionKey sr2k(*mSessionManager->GetSessionKeystore());
ReturnErrorOnFailure(DeriveSigmaKey(saltSpan, ByteSpan(kKDFSR2Info), sr2k));
// Construct Sigma2 TBS Data
size_t msg_r2_signed_len =
TLV::EstimateStructOverhead(kMaxCHIPCertLength, kMaxCHIPCertLength, kP256_PublicKey_Length, kP256_PublicKey_Length);
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R2_Signed;
VerifyOrReturnError(msg_R2_Signed.Alloc(msg_r2_signed_len), CHIP_ERROR_NO_MEMORY);
ReturnErrorOnFailure(ConstructTBSData(nocCert, icaCert, ByteSpan(mEphemeralKey->Pubkey(), mEphemeralKey->Pubkey().Length()),
ByteSpan(mRemotePubKey, mRemotePubKey.Length()), msg_R2_Signed.Get(), msg_r2_signed_len));
// Generate a Signature
P256ECDSASignature tbsData2Signature;
ReturnErrorOnFailure(
mFabricsTable->SignWithOpKeypair(mFabricIndex, ByteSpan{ msg_R2_Signed.Get(), msg_r2_signed_len }, tbsData2Signature));
msg_R2_Signed.Free();
// Construct Sigma2 TBE Data
size_t msg_r2_signed_enc_len = TLV::EstimateStructOverhead(nocCert.size(), icaCert.size(), tbsData2Signature.Length(),
SessionResumptionStorage::kResumptionIdSize);
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R2_Encrypted;
VerifyOrReturnError(msg_R2_Encrypted.Alloc(msg_r2_signed_enc_len + CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES), CHIP_ERROR_NO_MEMORY);
TLV::TLVWriter tlvWriter;
TLV::TLVType outerContainerType = TLV::kTLVType_NotSpecified;
tlvWriter.Init(msg_R2_Encrypted.Get(), msg_r2_signed_enc_len);
ReturnErrorOnFailure(tlvWriter.StartContainer(TLV::AnonymousTag(), TLV::kTLVType_Structure, outerContainerType));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(kTag_TBEData_SenderNOC), nocCert));
if (!icaCert.empty())
{
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(kTag_TBEData_SenderICAC), icaCert));
}
// We are now done with ICAC and NOC certs so we can release the memory.
{
icacBuf.Free();
icaCert = MutableByteSpan{};
nocBuf.Free();
nocCert = MutableByteSpan{};
}