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factor out Parser for decrypted Sigma2
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@Alami-Amine
Alami-Amine committed Dec 27, 2024
1 parent d785361 commit 403d4ee
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Showing 3 changed files with 68 additions and 35 deletions.
89 changes: 56 additions & 33 deletions src/protocols/secure_channel/CASESession.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1485,7 +1485,7 @@ CHIP_ERROR CASESession::HandleSigma2_and_SendSigma3(System::PacketBufferHandle &
CHIP_ERROR CASESession::HandleSigma2(System::PacketBufferHandle && msg)
{
MATTER_TRACE_SCOPE("HandleSigma2", "CASESession");
TLVReader decryptedDataTlvReader;
ContiguousBufferTLVReader decryptedDataTlvReader;

const uint8_t * buf = msg->Start();
size_t buflen = msg->DataLength();
Expand All @@ -1504,12 +1504,12 @@ CHIP_ERROR CASESession::HandleSigma2(System::PacketBufferHandle && msg)
P256PublicKey responderPublicKey;

// uint8_t responderRandom[kSigmaParamRandomNumberSize];
ByteSpan responderNOC;
ByteSpan responderICAC;
// ByteSpan responderNOC;
// ByteSpan responderICAC;

// uint16_t responderSessionId;

TLVType containerType = kTLVType_Structure;
// TLVType containerType = kTLVType_Structure;
size_t msg_r2_signed_len;

size_t msg_r2_encrypted_len = 0;
Expand All @@ -1521,6 +1521,7 @@ CHIP_ERROR CASESession::HandleSigma2(System::PacketBufferHandle && msg)
tlvReader.Init(std::move(msg));

ParsedSigma2 parsedSigma2;
ParsedSigma2TBEData parsedSigma2TBEData;

FabricId fabricId = kUndefinedFabricId;
{
Expand All @@ -1533,8 +1534,6 @@ CHIP_ERROR CASESession::HandleSigma2(System::PacketBufferHandle && msg)
VerifyOrExit(mEphemeralKey != nullptr, err = CHIP_ERROR_INTERNAL);
VerifyOrExit(buf != nullptr, err = CHIP_ERROR_MESSAGE_INCOMPLETE);

SuccessOrExit(err = mCommissioningHash.AddData(ByteSpan{ buf, buflen }));

ParseSigma2(tlvReader, parsedSigma2);

ChipLogDetail(SecureChannel, "Peer assigned session key ID %d", parsedSigma2.responderSessionId);
Expand All @@ -1545,7 +1544,7 @@ CHIP_ERROR CASESession::HandleSigma2(System::PacketBufferHandle && msg)
memcpy(mRemotePubKey.Bytes(), parsedSigma2.responderEphPubKey.data(), mRemotePubKey.Length());

// Generate a Shared Secret
SuccessOrExit(err = mEphemeralKey->ECDH_derive_secret(mRemotePubKey, mSharedSecret));
ReturnErrorOnFailure(err = mEphemeralKey->ECDH_derive_secret(mRemotePubKey, mSharedSecret));

// Generate the S2K key
{
Expand All @@ -1554,6 +1553,9 @@ CHIP_ERROR CASESession::HandleSigma2(System::PacketBufferHandle && msg)
err = ConstructSaltSigma2(ByteSpan(parsedSigma2.responderRandom), mRemotePubKey, ByteSpan(mIPK), saltSpan));
ReturnErrorOnFailure(err = DeriveSigmaKey(saltSpan, ByteSpan(kKDFSR2Info), sr2k));
}
// TODO verify location of this
// TODO why does this trigger a fialure if i move it just after call to PArseSigma2
ReturnErrorOnFailure(err = mCommissioningHash.AddData(ByteSpan{ buf, buflen }));

if (parsedSigma2.responderMrpParamsPresent)
{
Expand All @@ -1571,27 +1573,19 @@ CHIP_ERROR CASESession::HandleSigma2(System::PacketBufferHandle && msg)
sr2k.KeyHandle(), kTBEData2_Nonce, kTBEDataNonceLength, parsedSigma2.msgR2Encrypted.Get()));

decryptedDataTlvReader.Init(parsedSigma2.msgR2Encrypted.Get(), msg_r2_encrypted_len);
SuccessOrExit(err = decryptedDataTlvReader.Next(containerType, AnonymousTag()));
SuccessOrExit(err = decryptedDataTlvReader.EnterContainer(containerType));

SuccessOrExit(err = decryptedDataTlvReader.Next(kTLVType_ByteString, AsTlvContextTag(TBEDataTags::kSenderNOC)));
SuccessOrExit(err = decryptedDataTlvReader.Get(responderNOC));
ParseSigma2TBEData(decryptedDataTlvReader, parsedSigma2TBEData);

SuccessOrExit(err = decryptedDataTlvReader.Next());
if (decryptedDataTlvReader.GetTag() == AsTlvContextTag(TBEDataTags::kSenderICAC))
{
VerifyOrExit(decryptedDataTlvReader.GetType() == kTLVType_ByteString, err = CHIP_ERROR_WRONG_TLV_TYPE);
SuccessOrExit(err = decryptedDataTlvReader.Get(responderICAC));
SuccessOrExit(err = decryptedDataTlvReader.Next(kTLVType_ByteString, AsTlvContextTag(TBEDataTags::kSignature)));
}
std::copy(parsedSigma2TBEData.resumptionId.begin(), parsedSigma2TBEData.resumptionId.end(), mNewResumptionId.begin());

// Validate responder identity located in msg_r2_encrypted
// Constructing responder identity
{
CompressedFabricId unused;
FabricId responderFabricId;
SuccessOrExit(err = SetEffectiveTime());
SuccessOrExit(err = mFabricsTable->VerifyCredentials(mFabricIndex, responderNOC, responderICAC, mValidContext, unused,
SuccessOrExit(err = mFabricsTable->VerifyCredentials(mFabricIndex, parsedSigma2TBEData.responderNOC,
parsedSigma2TBEData.responderICAC, mValidContext, unused,
responderFabricId, responderNodeId, responderPublicKey));
VerifyOrExit(fabricId == responderFabricId, err = CHIP_ERROR_INVALID_CASE_PARAMETER);
// Verify that responderNodeId (from responderNOC) matches one that was included
Expand All @@ -1600,29 +1594,23 @@ CHIP_ERROR CASESession::HandleSigma2(System::PacketBufferHandle && msg)
}

// Construct msg_R2_Signed and validate the signature in msg_r2_encrypted
msg_r2_signed_len = EstimateStructOverhead(sizeof(uint16_t), responderNOC.size(), responderICAC.size(), kP256_PublicKey_Length,
kP256_PublicKey_Length);
msg_r2_signed_len =
EstimateStructOverhead(sizeof(uint16_t), parsedSigma2TBEData.responderNOC.size(), parsedSigma2TBEData.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()),
SuccessOrExit(err = ConstructTBSData(parsedSigma2TBEData.responderNOC, parsedSigma2TBEData.responderICAC,
ByteSpan(mRemotePubKey, mRemotePubKey.Length()),
ByteSpan(mEphemeralKey->Pubkey(), mEphemeralKey->Pubkey().Length()), msg_R2_Signed.Get(),
msg_r2_signed_len));

VerifyOrExit(decryptedDataTlvReader.GetTag() == AsTlvContextTag(TBEDataTags::kSignature), 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.Bytes(), tbsData2Signature.Length()));

// Validate signature
SuccessOrExit(err = responderPublicKey.ECDSA_validate_msg_signature(msg_R2_Signed.Get(), msg_r2_signed_len, tbsData2Signature));

// Retrieve session resumption ID
SuccessOrExit(err = decryptedDataTlvReader.Next(kTLVType_ByteString, AsTlvContextTag(TBEDataTags::kResumptionID)));
SuccessOrExit(err = decryptedDataTlvReader.GetBytes(mNewResumptionId.data(), mNewResumptionId.size()));
SuccessOrExit(err = responderPublicKey.ECDSA_validate_msg_signature(msg_R2_Signed.Get(), msg_r2_signed_len,
parsedSigma2TBEData.tbsData2Signature));

// Retrieve peer CASE Authenticated Tags (CATs) from peer's NOC.
SuccessOrExit(err = ExtractCATsFromOpCert(responderNOC, mPeerCATs));
SuccessOrExit(err = ExtractCATsFromOpCert(parsedSigma2TBEData.responderNOC, mPeerCATs));

exit:
if (err != CHIP_NO_ERROR)
Expand All @@ -1632,6 +1620,41 @@ CHIP_ERROR CASESession::HandleSigma2(System::PacketBufferHandle && msg)
return err;
}

CHIP_ERROR CASESession::ParseSigma2TBEData(ContiguousBufferTLVReader & decryptedDataTlvReader,
ParsedSigma2TBEData & outParsedSigma2TBE)
{
CHIP_ERROR err = CHIP_NO_ERROR;
TLVType containerType = kTLVType_Structure;

ReturnErrorOnFailure(err = decryptedDataTlvReader.Next(containerType, AnonymousTag()));
ReturnErrorOnFailure(err = decryptedDataTlvReader.EnterContainer(containerType));

ReturnErrorOnFailure(err = decryptedDataTlvReader.Next(kTLVType_ByteString, AsTlvContextTag(TBEDataTags::kSenderNOC)));
ReturnErrorOnFailure(err = decryptedDataTlvReader.GetByteView(outParsedSigma2TBE.responderNOC));

ReturnErrorOnFailure(err = decryptedDataTlvReader.Next());
if (decryptedDataTlvReader.GetTag() == AsTlvContextTag(TBEDataTags::kSenderICAC))
{
VerifyOrReturnError(decryptedDataTlvReader.GetType() == kTLVType_ByteString, err = CHIP_ERROR_WRONG_TLV_TYPE);
ReturnErrorOnFailure(err = decryptedDataTlvReader.GetByteView(outParsedSigma2TBE.responderICAC));
ReturnErrorOnFailure(err = decryptedDataTlvReader.Next(kTLVType_ByteString, AsTlvContextTag(TBEDataTags::kSignature)));
}

VerifyOrReturnError(decryptedDataTlvReader.GetTag() == AsTlvContextTag(TBEDataTags::kSignature),
err = CHIP_ERROR_INVALID_TLV_TAG);
VerifyOrReturnError(outParsedSigma2TBE.tbsData2Signature.Capacity() >= decryptedDataTlvReader.GetLength(),
err = CHIP_ERROR_INVALID_TLV_ELEMENT);
outParsedSigma2TBE.tbsData2Signature.SetLength(decryptedDataTlvReader.GetLength());
ReturnErrorOnFailure(err = decryptedDataTlvReader.GetBytes(outParsedSigma2TBE.tbsData2Signature.Bytes(),
outParsedSigma2TBE.tbsData2Signature.Length()));

// Retrieve session resumption ID
ReturnErrorOnFailure(err = decryptedDataTlvReader.Next(kTLVType_ByteString, AsTlvContextTag(TBEDataTags::kResumptionID)));
ReturnErrorOnFailure(err = decryptedDataTlvReader.GetByteView(outParsedSigma2TBE.resumptionId));

return CHIP_NO_ERROR;
}

CHIP_ERROR CASESession::SendSigma3a()
{
MATTER_TRACE_SCOPE("SendSigma3", "CASESession");
Expand Down
10 changes: 10 additions & 0 deletions src/protocols/secure_channel/CASESession.h
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Original file line number Diff line number Diff line change
Expand Up @@ -261,6 +261,15 @@ class DLL_EXPORT CASESession : public Messaging::UnsolicitedMessageHandler,
bool responderMrpParamsPresent = false;
SessionParameters responderSessionParams;
};

struct ParsedSigma2TBEData
{
ByteSpan responderNOC;
ByteSpan responderICAC;
Crypto::P256ECDSASignature tbsData2Signature;
ByteSpan resumptionId;
};

/**
* @brief Encodes a Sigma1 message into TLV format and allocates a buffer for it, which is owned by the PacketBufferHandle
* outparam.
Expand Down Expand Up @@ -294,6 +303,7 @@ class DLL_EXPORT CASESession : public Messaging::UnsolicitedMessageHandler,

static CHIP_ERROR ParseSigma2(TLV::ContiguousBufferTLVReader & tlvReader, ParsedSigma2 & parsedMessage);

static CHIP_ERROR ParseSigma2TBEData(TLV::ContiguousBufferTLVReader & tlvReader, ParsedSigma2TBEData & parsedMessage);
/**
* @brief Encodes a Sigma2 message into TLV format and allocates a buffer for it, which is owned by the PacketBufferHandle
* outparam.
Expand Down
4 changes: 2 additions & 2 deletions src/protocols/secure_channel/tests/TestCASESession.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1108,8 +1108,8 @@ struct SessionResumptionTestStorage : SessionResumptionStorage
{
SessionResumptionTestStorage(CHIP_ERROR findMethodReturnCode, ScopedNodeId peerNodeId, ResumptionIdStorage * resumptionId,
Crypto::P256ECDHDerivedSecret * sharedSecret) :
mFindMethodReturnCode(findMethodReturnCode), mPeerNodeId(peerNodeId), mResumptionId(resumptionId),
mSharedSecret(sharedSecret)
mFindMethodReturnCode(findMethodReturnCode),
mPeerNodeId(peerNodeId), mResumptionId(resumptionId), mSharedSecret(sharedSecret)
{}
SessionResumptionTestStorage(CHIP_ERROR findMethodReturnCode) : mFindMethodReturnCode(findMethodReturnCode) {}
CHIP_ERROR FindByScopedNodeId(const ScopedNodeId & node, ResumptionIdStorage & resumptionId,
Expand Down

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