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CASESession.cpp
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/*
*
* Copyright (c) 2021 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 <inttypes.h>
#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 <protocols/Protocols.h>
#include <protocols/secure_channel/StatusReport.h>
#include <system/TLVPacketBufferBackingStore.h>
#include <transport/SessionManager.h>
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 size_t kKDFInfoLength = sizeof(kKDFSR2Info);
constexpr uint8_t kKDFSEInfo[] = { 0x53, 0x65, 0x73, 0x73, 0x69, 0x6f, 0x6e, 0x4b, 0x65, 0x79, 0x73 };
constexpr size_t kKDFSEInfoLength = sizeof(kKDFSEInfo);
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_SigmaR1" */ { 0x4e, 0x43, 0x41, 0x53, 0x45, 0x5f, 0x53, 0x69, 0x67, 0x6d, 0x61, 0x53, 0x31 };
constexpr uint8_t kResume2MIC_Nonce[] =
/* "NCASE_SigmaR2" */ { 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");
enum
{
kTag_TBEData_SenderNOC = 1,
kTag_TBEData_SenderICAC = 2,
kTag_TBEData_Signature = 3,
kTag_TBEData_ResumptionID = 4,
};
#ifdef ENABLE_HSM_HKDF
using HKDF_sha_crypto = HKDF_shaHSM;
#else
using HKDF_sha_crypto = HKDF_sha;
#endif
// Wait at most 30 seconds for the response from the peer.
// This timeout value assumes the underlying transport is reliable.
// The session establishment fails if the response is not received within timeout window.
static constexpr ExchangeContext::Timeout kSigma_Response_Timeout = System::Clock::Seconds16(30);
CASESession::CASESession()
{
SetSecureSessionType(Transport::SecureSession::Type::kCASE);
mTrustedRootId = CertificateKeyId();
}
CASESession::~CASESession()
{
// Let's clear out any security state stored in the object, before destroying it.
Clear();
}
void CASESession::Clear()
{
// 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();
mCASESessionEstablished = false;
PairingSession::Clear();
mState = kInitialized;
CloseExchange();
}
void CASESession::CloseExchange()
{
if (mExchangeCtxt != nullptr)
{
mExchangeCtxt->Close();
mExchangeCtxt = nullptr;
}
}
CHIP_ERROR CASESession::ToCachable(CASESessionCachable & cachableSession)
{
const NodeId peerNodeId = GetPeerNodeId();
VerifyOrReturnError(CanCastTo<uint16_t>(mSharedSecret.Length()), CHIP_ERROR_INTERNAL);
VerifyOrReturnError(CanCastTo<uint64_t>(peerNodeId), CHIP_ERROR_INTERNAL);
memset(&cachableSession, 0, sizeof(cachableSession));
cachableSession.mSharedSecretLen = LittleEndian::HostSwap16(static_cast<uint16_t>(mSharedSecret.Length()));
cachableSession.mPeerNodeId = LittleEndian::HostSwap64(peerNodeId);
for (size_t i = 0; i < cachableSession.mPeerCATs.size(); i++)
{
cachableSession.mPeerCATs.val[i] = LittleEndian::HostSwap32(GetPeerCATs().val[i]);
}
// TODO: Get the fabric index
cachableSession.mLocalFabricIndex = 0;
cachableSession.mSessionSetupTimeStamp = LittleEndian::HostSwap64(mSessionSetupTimeStamp);
memcpy(cachableSession.mResumptionId, mResumptionId, sizeof(mResumptionId));
memcpy(cachableSession.mSharedSecret, mSharedSecret, mSharedSecret.Length());
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::FromCachable(const CASESessionCachable & cachableSession)
{
uint16_t length = LittleEndian::HostSwap16(cachableSession.mSharedSecretLen);
ReturnErrorOnFailure(mSharedSecret.SetLength(static_cast<size_t>(length)));
memset(mSharedSecret, 0, sizeof(mSharedSecret.Capacity()));
memcpy(mSharedSecret, cachableSession.mSharedSecret, length);
SetPeerNodeId(LittleEndian::HostSwap64(cachableSession.mPeerNodeId));
Credentials::CATValues peerCATs;
for (size_t i = 0; i < cachableSession.mPeerCATs.size(); i++)
{
peerCATs.val[i] = LittleEndian::HostSwap32(cachableSession.mPeerCATs.val[i]);
}
SetPeerCATs(peerCATs);
SetSessionTimeStamp(LittleEndian::HostSwap64(cachableSession.mSessionSetupTimeStamp));
// TODO: Set the fabric index correctly
mLocalFabricIndex = cachableSession.mLocalFabricIndex;
memcpy(mResumptionId, cachableSession.mResumptionId, sizeof(mResumptionId));
const ByteSpan * ipkListSpan = GetIPKList();
VerifyOrReturnError(ipkListSpan->size() == sizeof(mIPK), CHIP_ERROR_INVALID_ARGUMENT);
memcpy(mIPK, ipkListSpan->data(), sizeof(mIPK));
mCASESessionEstablished = true;
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::Init(uint16_t localSessionId, SessionEstablishmentDelegate * delegate)
{
VerifyOrReturnError(delegate != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
Clear();
ReturnErrorOnFailure(mCommissioningHash.Begin());
mDelegate = delegate;
SetLocalSessionId(localSessionId);
mValidContext.Reset();
mValidContext.mRequiredKeyUsages.Set(KeyUsageFlags::kDigitalSignature);
mValidContext.mRequiredKeyPurposes.Set(KeyPurposeFlags::kServerAuth);
return CHIP_NO_ERROR;
}
CHIP_ERROR
CASESession::ListenForSessionEstablishment(uint16_t localSessionId, FabricTable * fabrics, SessionEstablishmentDelegate * delegate)
{
VerifyOrReturnError(fabrics != nullptr, CHIP_ERROR_INVALID_ARGUMENT);
ReturnErrorOnFailure(Init(localSessionId, delegate));
mFabricsTable = fabrics;
mCASESessionEstablished = false;
ChipLogDetail(SecureChannel, "Waiting for Sigma1 msg");
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::EstablishSession(const Transport::PeerAddress peerAddress, FabricInfo * fabric, NodeId peerNodeId,
uint16_t localSessionId, ExchangeContext * exchangeCtxt,
SessionEstablishmentDelegate * delegate)
{
CHIP_ERROR err = CHIP_NO_ERROR;
// Return early on error here, as we have not initalized any state yet
ReturnErrorCodeIf(exchangeCtxt == nullptr, CHIP_ERROR_INVALID_ARGUMENT);
ReturnErrorCodeIf(fabric == nullptr, CHIP_ERROR_INVALID_ARGUMENT);
err = Init(localSessionId, delegate);
// 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);
mFabricInfo = fabric;
mExchangeCtxt->SetResponseTimeout(kSigma_Response_Timeout);
SetPeerAddress(peerAddress);
SetPeerNodeId(peerNodeId);
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 %" PRIu8,
mState);
mDelegate->OnSessionEstablishmentError(CHIP_ERROR_TIMEOUT);
// Null out mExchangeCtxt so that Clear() doesn't try closing it. The
// exchange will handle that.
mExchangeCtxt = nullptr;
Clear();
}
CHIP_ERROR CASESession::DeriveSecureSession(CryptoContext & session, CryptoContext::SessionRole role)
{
size_t saltlen;
(void) kKDFSEInfo;
(void) kKDFSEInfoLength;
VerifyOrReturnError(mCASESessionEstablished, CHIP_ERROR_INCORRECT_STATE);
// Generate Salt for Encryption keys
saltlen = sizeof(mIPK) + kSHA256_Hash_Length;
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_salt;
ReturnErrorCodeIf(!msg_salt.Alloc(saltlen), CHIP_ERROR_NO_MEMORY);
{
Encoding::LittleEndian::BufferWriter bbuf(msg_salt.Get(), saltlen);
bbuf.Put(mIPK, sizeof(mIPK));
bbuf.Put(mMessageDigest, sizeof(mMessageDigest));
VerifyOrReturnError(bbuf.Fit(), CHIP_ERROR_BUFFER_TOO_SMALL);
}
ReturnErrorOnFailure(session.InitFromSecret(ByteSpan(mSharedSecret, mSharedSecret.Length()), ByteSpan(msg_salt.Get(), saltlen),
CryptoContext::SessionInfoType::kSessionEstablishment, role));
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::SendSigma1()
{
size_t data_len = TLV::EstimateStructOverhead(kSigmaParamRandomNumberSize, // initiatorRandom
sizeof(uint16_t), // initiatorSessionId,
kSHA256_Hash_Length, // destinationId
kP256_PublicKey_Length, // InitiatorEphPubKey,
/* TLV::EstimateStructOverhead(sizeof(uint16_t),
sizeof(uint16)_t), // initiatorMRPParams */
kCASEResumptionIDSize, 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 };
// Generate an ephemeral keypair
ReturnErrorOnFailure(mEphemeralKey.Initialize());
// 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()));
// Generate a Destination Identifier
{
MutableByteSpan destinationIdSpan(destinationIdentifier);
ReturnErrorCodeIf(mFabricInfo == nullptr, CHIP_ERROR_INCORRECT_STATE);
memcpy(mIPK, GetIPKList()->data(), sizeof(mIPK));
ReturnErrorOnFailure(
mFabricInfo->GenerateDestinationID(ByteSpan(mIPK), ByteSpan(mInitiatorRandom), GetPeerNodeId(), 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 CASE session was previously established using the current state information, let's fill in the session resumption
// information in the the Sigma1 request. It'll speed up the session establishment process if the peer can resume the old
// session, since no certificate chains will have to be verified.
if (mCASESessionEstablished)
{
ReturnErrorOnFailure(tlvWriter.PutBytes(TLV::ContextTag(6), mResumptionId, kCASEResumptionIDSize));
uint8_t initiatorResume1MIC[CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES];
MutableByteSpan resumeMICSpan(initiatorResume1MIC);
ReturnErrorOnFailure(GenerateSigmaResumeMIC(ByteSpan(mInitiatorRandom), ByteSpan(mResumptionId), ByteSpan(kKDFS1RKeyInfo),
ByteSpan(kResume1MIC_Nonce), resumeMICSpan));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(7), resumeMICSpan));
}
ReturnErrorOnFailure(tlvWriter.EndContainer(outerContainerType));
ReturnErrorOnFailure(tlvWriter.Finalize(&msg_R1));
ReturnErrorOnFailure(mCommissioningHash.AddData(ByteSpan{ msg_R1->Start(), msg_R1->DataLength() }));
// The state is being updated here before the message is successfully sent.
// This is done here due to limitation in unit test harness, where the SendMessage() immediately calls
// the OnMessageReceived(). If mState was updated after SendMessage, the receive will fail in unit tests.
// TODO: Update secure session SendMessage() unit test harness to do asynchronous send and receives.
mState = kSentSigma1;
// Call delegate to send the msg to peer
ReturnErrorOnFailure(mExchangeCtxt->SendMessage(Protocols::SecureChannel::MsgType::CASE_Sigma1, std::move(msg_R1),
SendFlags(SendMessageFlags::kExpectResponse)));
ChipLogDetail(SecureChannel, "Sent Sigma1 msg");
mDelegate->OnSessionEstablishmentStarted();
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::HandleSigma1_and_SendSigma2(System::PacketBufferHandle && msg)
{
ReturnErrorOnFailure(HandleSigma1(std::move(msg)));
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::HandleSigma1(System::PacketBufferHandle && msg)
{
CHIP_ERROR err = CHIP_NO_ERROR;
System::PacketBufferTLVReader tlvReader;
uint16_t initiatorSessionId;
ByteSpan destinationIdentifier;
ByteSpan initiatorRandom;
ChipLogDetail(SecureChannel, "Received Sigma1 msg");
bool sessionResumptionRequested = false;
ByteSpan resumptionId;
ByteSpan resume1MIC;
ByteSpan initiatorPubKey;
const ByteSpan * ipkListSpan = GetIPKList();
FabricIndex fabricIndex = kUndefinedFabricIndex;
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);
if (sessionResumptionRequested && resumptionId.data_equal(ByteSpan(mResumptionId)))
{
// Cross check resume1MIC with the shared secret
if (ValidateSigmaResumeMIC(resume1MIC, initiatorRandom, resumptionId, ByteSpan(kKDFS1RKeyInfo),
ByteSpan(kResume1MIC_Nonce)) == CHIP_NO_ERROR)
{
// Send Sigma2Resume message to the initiator
SuccessOrExit(err = SendSigma2Resume(initiatorRandom));
mDelegate->OnSessionEstablishmentStarted();
// Early returning here, since we have sent Sigma2Resume, and no further processing is needed for the Sigma1 message
return CHIP_NO_ERROR;
}
}
memcpy(mIPK, ipkListSpan->data(), sizeof(mIPK));
VerifyOrExit(mFabricsTable != nullptr, err = CHIP_ERROR_INCORRECT_STATE);
fabricIndex =
mFabricsTable->FindDestinationIDCandidate(destinationIdentifier, initiatorRandom, ipkListSpan, GetIPKListEntries());
VerifyOrExit(fabricIndex != kUndefinedFabricIndex, err = CHIP_ERROR_KEY_NOT_FOUND);
mFabricInfo = mFabricsTable->FindFabricWithIndex(fabricIndex);
VerifyOrExit(mFabricInfo != nullptr, err = CHIP_ERROR_INCORRECT_STATE);
// 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 = kInitialized;
}
else if (err != CHIP_NO_ERROR)
{
SendStatusReport(mExchangeCtxt, kProtocolCodeInvalidParam);
mState = kInitialized;
}
return err;
}
CHIP_ERROR CASESession::SendSigma2Resume(const ByteSpan & initiatorRandom)
{
size_t max_sigma2_resume_data_len = TLV::EstimateStructOverhead(kCASEResumptionIDSize, CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES,
sizeof(uint16_t) /*, kMRPOptionalParamsLength, */);
System::PacketBufferTLVWriter tlvWriter;
System::PacketBufferHandle msg_R2_resume;
TLV::TLVType outerContainerType = TLV::kTLVType_NotSpecified;
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(mResumptionId, sizeof(mResumptionId)));
ReturnErrorOnFailure(tlvWriter.StartContainer(TLV::AnonymousTag, TLV::kTLVType_Structure, outerContainerType));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(1), ByteSpan(mResumptionId)));
uint8_t sigma2ResumeMIC[CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES];
MutableByteSpan resumeMICSpan(sigma2ResumeMIC);
ReturnErrorOnFailure(GenerateSigmaResumeMIC(initiatorRandom, ByteSpan(mResumptionId), ByteSpan(kKDFS2RKeyInfo),
ByteSpan(kResume2MIC_Nonce), resumeMICSpan));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(2), resumeMICSpan));
ReturnErrorOnFailure(tlvWriter.Put(TLV::ContextTag(3), GetLocalSessionId()));
// TODO: Add support for optional MRP parameters
ReturnErrorOnFailure(tlvWriter.EndContainer(outerContainerType));
ReturnErrorOnFailure(tlvWriter.Finalize(&msg_R2_resume));
// The state is being updated here before the message is successfully sent.
// This is done here due to limitation in unit test harness, where the SendMessage() immediately calls
// the OnMessageReceived(). If mState was updated after SendMessage, the receive will fail in unit tests.
// TODO: Update secure session SendMessage() unit test harness to do asynchronous send and receives.
mState = kSentSigma2Resume;
// Call delegate to send the msg to peer
ReturnErrorOnFailure(mExchangeCtxt->SendMessage(Protocols::SecureChannel::MsgType::CASE_Sigma2Resume, std::move(msg_R2_resume),
SendFlags(SendMessageFlags::kExpectResponse)));
ChipLogDetail(SecureChannel, "Sent Sigma2Resume msg");
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::SendSigma2()
{
VerifyOrReturnError(mFabricInfo != nullptr, CHIP_ERROR_INCORRECT_STATE);
ByteSpan icaCert;
ReturnErrorOnFailure(mFabricInfo->GetICACert(icaCert));
ByteSpan nocCert;
ReturnErrorOnFailure(mFabricInfo->GetNOCCert(nocCert));
mTrustedRootId = mFabricInfo->GetTrustedRootId();
VerifyOrReturnError(!mTrustedRootId.empty(), CHIP_ERROR_INTERNAL);
// Fill in the random value
uint8_t msg_rand[kSigmaParamRandomNumberSize];
ReturnErrorOnFailure(DRBG_get_bytes(&msg_rand[0], sizeof(msg_rand)));
// Generate an ephemeral keypair
#ifdef ENABLE_HSM_CASE_EPHEMERAL_KEY
mEphemeralKey.SetKeyId(CASE_EPHEMERAL_KEY);
#endif
ReturnErrorOnFailure(mEphemeralKey.Initialize());
// 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));
HKDF_sha_crypto mHKDF;
uint8_t sr2k[CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES];
ReturnErrorOnFailure(mHKDF.HKDF_SHA256(mSharedSecret, mSharedSecret.Length(), saltSpan.data(), saltSpan.size(), kKDFSR2Info,
kKDFInfoLength, sr2k, CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES));
// Construct Sigma2 TBS Data
size_t msg_r2_signed_len =
TLV::EstimateStructOverhead(nocCert.size(), icaCert.size(), 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
VerifyOrReturnError(mFabricInfo->GetOperationalKey() != nullptr, CHIP_ERROR_INCORRECT_STATE);
P256ECDSASignature tbsData2Signature;
ReturnErrorOnFailure(
mFabricInfo->GetOperationalKey()->ECDSA_sign_msg(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(), kCASEResumptionIDSize);
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));
}
ReturnErrorOnFailure(tlvWriter.PutBytes(TLV::ContextTag(kTag_TBEData_Signature), tbsData2Signature,
static_cast<uint32_t>(tbsData2Signature.Length())));
// Generate a new resumption ID
ReturnErrorOnFailure(DRBG_get_bytes(mResumptionId, sizeof(mResumptionId)));
ReturnErrorOnFailure(tlvWriter.PutBytes(TLV::ContextTag(kTag_TBEData_ResumptionID), mResumptionId,
static_cast<uint32_t>(sizeof(mResumptionId))));
ReturnErrorOnFailure(tlvWriter.EndContainer(outerContainerType));
ReturnErrorOnFailure(tlvWriter.Finalize());
msg_r2_signed_enc_len = static_cast<size_t>(tlvWriter.GetLengthWritten());
// Generate the encrypted data blob
ReturnErrorOnFailure(AES_CCM_encrypt(msg_R2_Encrypted.Get(), msg_r2_signed_enc_len, nullptr, 0, sr2k,
CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES, kTBEData2_Nonce, kTBEDataNonceLength,
msg_R2_Encrypted.Get(), msg_R2_Encrypted.Get() + msg_r2_signed_enc_len,
CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES));
// Construct Sigma2 Msg
size_t data_len = TLV::EstimateStructOverhead(kSigmaParamRandomNumberSize, sizeof(uint16_t), kP256_PublicKey_Length,
msg_r2_signed_enc_len, CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES);
System::PacketBufferHandle msg_R2 = System::PacketBufferHandle::New(data_len);
VerifyOrReturnError(!msg_R2.IsNull(), CHIP_ERROR_NO_MEMORY);
System::PacketBufferTLVWriter tlvWriterMsg2;
outerContainerType = TLV::kTLVType_NotSpecified;
tlvWriterMsg2.Init(std::move(msg_R2));
ReturnErrorOnFailure(tlvWriterMsg2.StartContainer(TLV::AnonymousTag, TLV::kTLVType_Structure, outerContainerType));
ReturnErrorOnFailure(tlvWriterMsg2.PutBytes(TLV::ContextTag(1), &msg_rand[0], sizeof(msg_rand)));
ReturnErrorOnFailure(tlvWriterMsg2.Put(TLV::ContextTag(2), GetLocalSessionId()));
ReturnErrorOnFailure(
tlvWriterMsg2.PutBytes(TLV::ContextTag(3), mEphemeralKey.Pubkey(), static_cast<uint32_t>(mEphemeralKey.Pubkey().Length())));
ReturnErrorOnFailure(tlvWriterMsg2.PutBytes(TLV::ContextTag(4), msg_R2_Encrypted.Get(),
static_cast<uint32_t>(msg_r2_signed_enc_len + CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES)));
ReturnErrorOnFailure(tlvWriterMsg2.EndContainer(outerContainerType));
ReturnErrorOnFailure(tlvWriterMsg2.Finalize(&msg_R2));
ReturnErrorOnFailure(mCommissioningHash.AddData(ByteSpan{ msg_R2->Start(), msg_R2->DataLength() }));
// The state is being updated here before the message is successfully sent.
// This is done here due to limitation in unit test harness, where the SendMessage() immediately calls
// the OnMessageReceived(). If mState was updated after SendMessage, the receive will fail in unit tests.
// TODO: Update secure session SendMessage() unit test harness to do asynchronous send and receives.
mState = kSentSigma2;
// Call delegate to send the msg to peer
ReturnErrorOnFailure(mExchangeCtxt->SendMessage(Protocols::SecureChannel::MsgType::CASE_Sigma2, std::move(msg_R2),
SendFlags(SendMessageFlags::kExpectResponse)));
ChipLogDetail(SecureChannel, "Sent Sigma2 msg");
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::HandleSigma2Resume(System::PacketBufferHandle && msg)
{
CHIP_ERROR err = CHIP_NO_ERROR;
System::PacketBufferTLVReader tlvReader;
TLV::TLVType containerType = TLV::kTLVType_Structure;
uint16_t responderSessionId;
uint32_t decodeTagIdSeq = 0;
ChipLogDetail(SecureChannel, "Received Sigma2Resume msg");
uint8_t sigma2ResumeMIC[CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES];
tlvReader.Init(std::move(msg));
SuccessOrExit(err = tlvReader.Next(containerType, TLV::AnonymousTag));
SuccessOrExit(err = tlvReader.EnterContainer(containerType));
SuccessOrExit(err = tlvReader.Next());
VerifyOrExit(TLV::TagNumFromTag(tlvReader.GetTag()) == ++decodeTagIdSeq, err = CHIP_ERROR_INVALID_TLV_TAG);
VerifyOrExit(tlvReader.GetLength() == kCASEResumptionIDSize, err = CHIP_ERROR_INVALID_TLV_ELEMENT);
SuccessOrExit(err = tlvReader.GetBytes(mResumptionId, kCASEResumptionIDSize));
SuccessOrExit(err = tlvReader.Next());
VerifyOrExit(TLV::TagNumFromTag(tlvReader.GetTag()) == ++decodeTagIdSeq, err = CHIP_ERROR_INVALID_TLV_TAG);
VerifyOrExit(tlvReader.GetLength() == CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES, err = CHIP_ERROR_INVALID_TLV_ELEMENT);
SuccessOrExit(err = tlvReader.GetBytes(sigma2ResumeMIC, CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES));
SuccessOrExit(err = ValidateSigmaResumeMIC(ByteSpan(sigma2ResumeMIC), ByteSpan(mInitiatorRandom), ByteSpan(mResumptionId),
ByteSpan(kKDFS2RKeyInfo), ByteSpan(kResume2MIC_Nonce)));
SuccessOrExit(err = tlvReader.Next());
VerifyOrExit(TLV::TagNumFromTag(tlvReader.GetTag()) == ++decodeTagIdSeq, err = CHIP_ERROR_INVALID_TLV_TAG);
SuccessOrExit(err = tlvReader.Get(responderSessionId));
ChipLogDetail(SecureChannel, "Peer assigned session session ID %d", responderSessionId);
SetPeerSessionId(responderSessionId);
SendStatusReport(mExchangeCtxt, kProtocolCodeSuccess);
// TODO: Set timestamp on the new session, to allow selecting a least-recently-used session for eviction
// on running out of session contexts.
mCASESessionEstablished = true;
// Forget our exchange, as no additional messages are expected from the peer
mExchangeCtxt = nullptr;
// Call delegate to indicate session establishment is successful
mDelegate->OnSessionEstablished();
exit:
if (err != CHIP_NO_ERROR)
{
SendStatusReport(mExchangeCtxt, kProtocolCodeInvalidParam);
}
return err;
}
CHIP_ERROR CASESession::HandleSigma2_and_SendSigma3(System::PacketBufferHandle && msg)
{
ReturnErrorOnFailure(HandleSigma2(std::move(msg)));
ReturnErrorOnFailure(SendSigma3());
return CHIP_NO_ERROR;
}
CHIP_ERROR CASESession::HandleSigma2(System::PacketBufferHandle && msg)
{
CHIP_ERROR err = CHIP_NO_ERROR;
System::PacketBufferTLVReader tlvReader;
TLV::TLVReader decryptedDataTlvReader;
TLV::TLVType containerType = TLV::kTLVType_Structure;
const uint8_t * buf = msg->Start();
size_t buflen = msg->DataLength();
uint8_t msg_salt[kIPKSize + kSigmaParamRandomNumberSize + kP256_PublicKey_Length + kSHA256_Hash_Length];
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R2_Encrypted;
size_t msg_r2_encrypted_len = 0;
size_t msg_r2_encrypted_len_with_tag = 0;
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R2_Signed;
size_t msg_r2_signed_len;
uint8_t sr2k[CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES];
P256ECDSASignature tbsData2Signature;
P256PublicKey remoteCredential;
uint8_t responderRandom[kSigmaParamRandomNumberSize];
ByteSpan responderNOC;
ByteSpan responderICAC;
uint16_t responderSessionId;
uint32_t decodeTagIdSeq = 0;
VerifyOrExit(buf != nullptr, err = CHIP_ERROR_MESSAGE_INCOMPLETE);
ChipLogDetail(SecureChannel, "Received Sigma2 msg");
tlvReader.Init(std::move(msg));
SuccessOrExit(err = tlvReader.Next(containerType, TLV::AnonymousTag));
SuccessOrExit(err = tlvReader.EnterContainer(containerType));
// Retrieve Responder's Random value
SuccessOrExit(err = tlvReader.Next());
VerifyOrExit(TLV::TagNumFromTag(tlvReader.GetTag()) == ++decodeTagIdSeq, err = CHIP_ERROR_INVALID_TLV_TAG);
SuccessOrExit(err = tlvReader.GetBytes(responderRandom, sizeof(responderRandom)));
// Assign Session ID
SuccessOrExit(err = tlvReader.Next());
VerifyOrExit(TLV::TagNumFromTag(tlvReader.GetTag()) == ++decodeTagIdSeq, err = CHIP_ERROR_INVALID_TLV_TAG);
SuccessOrExit(err = tlvReader.Get(responderSessionId));
ChipLogDetail(SecureChannel, "Peer assigned session session ID %d", responderSessionId);
SetPeerSessionId(responderSessionId);
// Retrieve Responder's Ephemeral Pubkey
SuccessOrExit(err = tlvReader.Next());
VerifyOrExit(TLV::TagNumFromTag(tlvReader.GetTag()) == ++decodeTagIdSeq, err = CHIP_ERROR_INVALID_TLV_TAG);
SuccessOrExit(err = tlvReader.GetBytes(mRemotePubKey, static_cast<uint32_t>(mRemotePubKey.Length())));
// Generate a Shared Secret
SuccessOrExit(err = mEphemeralKey.ECDH_derive_secret(mRemotePubKey, mSharedSecret));
// Generate the S2K key
{
MutableByteSpan saltSpan(msg_salt);
err = ConstructSaltSigma2(ByteSpan(responderRandom), mRemotePubKey, ByteSpan(mIPK), saltSpan);
SuccessOrExit(err);
HKDF_sha_crypto mHKDF;
err = mHKDF.HKDF_SHA256(mSharedSecret, mSharedSecret.Length(), saltSpan.data(), saltSpan.size(), kKDFSR2Info,
kKDFInfoLength, sr2k, CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES);
SuccessOrExit(err);
}
SuccessOrExit(err = mCommissioningHash.AddData(ByteSpan{ buf, buflen }));
// Generate decrypted data
SuccessOrExit(err = tlvReader.Next());
VerifyOrExit(TLV::TagNumFromTag(tlvReader.GetTag()) == ++decodeTagIdSeq, err = CHIP_ERROR_INVALID_TLV_TAG);
VerifyOrExit(msg_R2_Encrypted.Alloc(tlvReader.GetLength()), err = CHIP_ERROR_NO_MEMORY);
msg_r2_encrypted_len_with_tag = tlvReader.GetLength();
VerifyOrExit(msg_r2_encrypted_len_with_tag > CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES, err = CHIP_ERROR_INVALID_TLV_ELEMENT);
SuccessOrExit(err = tlvReader.GetBytes(msg_R2_Encrypted.Get(), static_cast<uint32_t>(msg_r2_encrypted_len_with_tag)));
msg_r2_encrypted_len = msg_r2_encrypted_len_with_tag - CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES;
SuccessOrExit(err = AES_CCM_decrypt(msg_R2_Encrypted.Get(), msg_r2_encrypted_len, nullptr, 0,
msg_R2_Encrypted.Get() + msg_r2_encrypted_len, CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES, sr2k,
CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES, kTBEData2_Nonce, kTBEDataNonceLength,
msg_R2_Encrypted.Get()));
decryptedDataTlvReader.Init(msg_R2_Encrypted.Get(), msg_r2_encrypted_len);
containerType = TLV::kTLVType_Structure;
SuccessOrExit(err = decryptedDataTlvReader.Next(containerType, TLV::AnonymousTag));
SuccessOrExit(err = decryptedDataTlvReader.EnterContainer(containerType));
SuccessOrExit(err = decryptedDataTlvReader.Next(TLV::kTLVType_ByteString, TLV::ContextTag(kTag_TBEData_SenderNOC)));
SuccessOrExit(err = decryptedDataTlvReader.Get(responderNOC));
SuccessOrExit(err = decryptedDataTlvReader.Next());
if (TLV::TagNumFromTag(decryptedDataTlvReader.GetTag()) == kTag_TBEData_SenderICAC)
{
VerifyOrExit(decryptedDataTlvReader.GetType() == TLV::kTLVType_ByteString, err = CHIP_ERROR_WRONG_TLV_TYPE);
SuccessOrExit(err = decryptedDataTlvReader.Get(responderICAC));
SuccessOrExit(err = decryptedDataTlvReader.Next(TLV::kTLVType_ByteString, TLV::ContextTag(kTag_TBEData_Signature)));
}
// Validate responder identity located in msg_r2_encrypted
// Constructing responder identity
SuccessOrExit(err = Validate_and_RetrieveResponderID(responderNOC, responderICAC, remoteCredential));
// Construct msg_R2_Signed and validate the signature in msg_r2_encrypted
msg_r2_signed_len = TLV::EstimateStructOverhead(sizeof(uint16_t), responderNOC.size(), responderICAC.size(),
kP256_PublicKey_Length, kP256_PublicKey_Length);
VerifyOrExit(msg_R2_Signed.Alloc(msg_r2_signed_len), err = CHIP_ERROR_NO_MEMORY);
SuccessOrExit(err = ConstructTBSData(responderNOC, responderICAC, ByteSpan(mRemotePubKey, mRemotePubKey.Length()),
ByteSpan(mEphemeralKey.Pubkey(), mEphemeralKey.Pubkey().Length()), msg_R2_Signed.Get(),
msg_r2_signed_len));
VerifyOrExit(TLV::TagNumFromTag(decryptedDataTlvReader.GetTag()) == kTag_TBEData_Signature, err = CHIP_ERROR_INVALID_TLV_TAG);
VerifyOrExit(tbsData2Signature.Capacity() >= decryptedDataTlvReader.GetLength(), err = CHIP_ERROR_INVALID_TLV_ELEMENT);
tbsData2Signature.SetLength(decryptedDataTlvReader.GetLength());
SuccessOrExit(err = decryptedDataTlvReader.GetBytes(tbsData2Signature, tbsData2Signature.Length()));
// Validate signature
SuccessOrExit(err = remoteCredential.ECDSA_validate_msg_signature(msg_R2_Signed.Get(), msg_r2_signed_len, tbsData2Signature));
// Retrieve session resumption ID
SuccessOrExit(err = decryptedDataTlvReader.Next(TLV::kTLVType_ByteString, TLV::ContextTag(kTag_TBEData_ResumptionID)));
SuccessOrExit(err = decryptedDataTlvReader.GetBytes(mResumptionId, static_cast<uint32_t>(sizeof(mResumptionId))));
// Retrieve peer CASE Authenticated Tags (CATs) from peer's NOC.
Credentials::CATValues peerCATs;
SuccessOrExit(err = ExtractCATsFromOpCert(responderNOC, peerCATs));
SetPeerCATs(peerCATs);
exit:
if (err != CHIP_NO_ERROR)
{
SendStatusReport(mExchangeCtxt, kProtocolCodeInvalidParam);
}
return err;
}
CHIP_ERROR CASESession::SendSigma3()
{
CHIP_ERROR err = CHIP_NO_ERROR;
MutableByteSpan messageDigestSpan(mMessageDigest);
System::PacketBufferHandle msg_R3;
size_t data_len;
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R3_Encrypted;
size_t msg_r3_encrypted_len;
uint8_t msg_salt[kIPKSize + kSHA256_Hash_Length];
uint8_t sr3k[CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES];
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R3_Signed;
size_t msg_r3_signed_len;
P256ECDSASignature tbsData3Signature;
ChipLogDetail(SecureChannel, "Sending Sigma3");
ByteSpan icaCert;
ByteSpan nocCert;
VerifyOrExit(mFabricInfo != nullptr, err = CHIP_ERROR_INCORRECT_STATE);
SuccessOrExit(err = mFabricInfo->GetICACert(icaCert));
SuccessOrExit(err = mFabricInfo->GetNOCCert(nocCert));
mTrustedRootId = mFabricInfo->GetTrustedRootId();
VerifyOrExit(!mTrustedRootId.empty(), err = CHIP_ERROR_INTERNAL);
// Prepare Sigma3 TBS Data Blob
msg_r3_signed_len = TLV::EstimateStructOverhead(icaCert.size(), nocCert.size(), kP256_PublicKey_Length, kP256_PublicKey_Length);
VerifyOrExit(msg_R3_Signed.Alloc(msg_r3_signed_len), err = CHIP_ERROR_NO_MEMORY);
SuccessOrExit(err = ConstructTBSData(nocCert, icaCert, ByteSpan(mEphemeralKey.Pubkey(), mEphemeralKey.Pubkey().Length()),
ByteSpan(mRemotePubKey, mRemotePubKey.Length()), msg_R3_Signed.Get(), msg_r3_signed_len));
// Generate a signature
VerifyOrExit(mFabricInfo->GetOperationalKey() != nullptr, err = CHIP_ERROR_INCORRECT_STATE);
err = mFabricInfo->GetOperationalKey()->ECDSA_sign_msg(msg_R3_Signed.Get(), msg_r3_signed_len, tbsData3Signature);
SuccessOrExit(err);
// Prepare Sigma3 TBE Data Blob
msg_r3_encrypted_len = TLV::EstimateStructOverhead(nocCert.size(), icaCert.size(), tbsData3Signature.Length());
VerifyOrExit(msg_R3_Encrypted.Alloc(msg_r3_encrypted_len + CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES), err = CHIP_ERROR_NO_MEMORY);
{
TLV::TLVWriter tlvWriter;
TLV::TLVType outerContainerType = TLV::kTLVType_NotSpecified;
tlvWriter.Init(msg_R3_Encrypted.Get(), msg_r3_encrypted_len);
SuccessOrExit(err = tlvWriter.StartContainer(TLV::AnonymousTag, TLV::kTLVType_Structure, outerContainerType));
SuccessOrExit(err = tlvWriter.Put(TLV::ContextTag(kTag_TBEData_SenderNOC), nocCert));
if (!icaCert.empty())
{
SuccessOrExit(err = tlvWriter.Put(TLV::ContextTag(kTag_TBEData_SenderICAC), icaCert));
}
SuccessOrExit(err = tlvWriter.PutBytes(TLV::ContextTag(kTag_TBEData_Signature), tbsData3Signature,
static_cast<uint32_t>(tbsData3Signature.Length())));
SuccessOrExit(err = tlvWriter.EndContainer(outerContainerType));
SuccessOrExit(err = tlvWriter.Finalize());
msg_r3_encrypted_len = static_cast<size_t>(tlvWriter.GetLengthWritten());
}
// Generate S3K key
{
MutableByteSpan saltSpan(msg_salt);
err = ConstructSaltSigma3(ByteSpan(mIPK), saltSpan);
SuccessOrExit(err);
HKDF_sha_crypto mHKDF;
err = mHKDF.HKDF_SHA256(mSharedSecret, mSharedSecret.Length(), saltSpan.data(), saltSpan.size(), kKDFSR3Info,
kKDFInfoLength, sr3k, CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES);
SuccessOrExit(err);
}
// Generated Encrypted data blob
err = AES_CCM_encrypt(msg_R3_Encrypted.Get(), msg_r3_encrypted_len, nullptr, 0, sr3k, CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES,
kTBEData3_Nonce, kTBEDataNonceLength, msg_R3_Encrypted.Get(),
msg_R3_Encrypted.Get() + msg_r3_encrypted_len, CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES);
SuccessOrExit(err);
// Generate Sigma3 Msg
data_len = TLV::EstimateStructOverhead(CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES, msg_r3_encrypted_len);
msg_R3 = System::PacketBufferHandle::New(data_len);
VerifyOrExit(!msg_R3.IsNull(), err = CHIP_ERROR_NO_MEMORY);
{
System::PacketBufferTLVWriter tlvWriter;
TLV::TLVType outerContainerType = TLV::kTLVType_NotSpecified;
tlvWriter.Init(std::move(msg_R3));
err = tlvWriter.StartContainer(TLV::AnonymousTag, TLV::kTLVType_Structure, outerContainerType);
SuccessOrExit(err);
err = tlvWriter.PutBytes(TLV::ContextTag(1), msg_R3_Encrypted.Get(),
static_cast<uint32_t>(msg_r3_encrypted_len + CHIP_CRYPTO_AEAD_MIC_LENGTH_BYTES));
SuccessOrExit(err);
err = tlvWriter.EndContainer(outerContainerType);
SuccessOrExit(err);
err = tlvWriter.Finalize(&msg_R3);
SuccessOrExit(err);
}
err = mCommissioningHash.AddData(ByteSpan{ msg_R3->Start(), msg_R3->DataLength() });
SuccessOrExit(err);
// The state is being updated here before the message is successfully sent.
// This is done here due to limitation in unit test harness, where the SendMessage() immediately calls
// the OnMessageReceived(). If mState was updated after SendMessage, the receive will fail in unit tests.
// TODO: Update secure session SendMessage() unit test harness to do asynchronous send and receives.
mState = kSentSigma3;
// Call delegate to send the Msg3 to peer
err = mExchangeCtxt->SendMessage(Protocols::SecureChannel::MsgType::CASE_Sigma3, std::move(msg_R3),
SendFlags(SendMessageFlags::kExpectResponse));
SuccessOrExit(err);
ChipLogDetail(SecureChannel, "Sent Sigma3 msg");
err = mCommissioningHash.Finish(messageDigestSpan);
SuccessOrExit(err);
exit:
if (err != CHIP_NO_ERROR)
{
SendStatusReport(mExchangeCtxt, kProtocolCodeInvalidParam);
mState = kInitialized;
}
return err;
}
CHIP_ERROR CASESession::HandleSigma3(System::PacketBufferHandle && msg)
{
CHIP_ERROR err = CHIP_NO_ERROR;
MutableByteSpan messageDigestSpan(mMessageDigest);
System::PacketBufferTLVReader tlvReader;
TLV::TLVReader decryptedDataTlvReader;
TLV::TLVType containerType = TLV::kTLVType_Structure;
const uint8_t * buf = msg->Start();
const uint16_t bufLen = msg->DataLength();
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R3_Encrypted;
size_t msg_r3_encrypted_len = 0;
size_t msg_r3_encrypted_len_with_tag = 0;
chip::Platform::ScopedMemoryBuffer<uint8_t> msg_R3_Signed;
size_t msg_r3_signed_len;
uint8_t sr3k[CHIP_CRYPTO_SYMMETRIC_KEY_LENGTH_BYTES];
P256ECDSASignature tbsData3Signature;
P256PublicKey remoteCredential;