[CASESession] Factoring Out Sigma2 and Sigma3 Parsing Functions for Improved Testability #36941
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…sionParameters as an outparam and does not touch PairingSession class member mRemoteSessionParameters - a utility SetRemoteSessionParameters to be able to set PairingSession class member mRemoteSessionParameters
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PR #36941: Size comparison from 2249628 to ea053d8 Increases above 0.2%:
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PR #36941: Size comparison from 2249628 to cc77e8c Increases above 0.2%:
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| if (data.keystore != nullptr) | ||
| { | ||
| SuccessOrExit(err = helper->ScheduleWork()); | ||
| ReturnErrorOnFailure(helper->ScheduleWork()); |
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This is async and will swithc context. It is certain that there is nothing here that will be out of scope later?
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I did not change the scope of any of the decoded elements, so it should be fine.
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Well that assumes it was fine before... Do we run the unit tests with asan?
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| SuccessOrExit(err = ConstructTBSData(data.initiatorNOC, data.initiatorICAC, ByteSpan(mRemotePubKey, mRemotePubKey.Length()), | ||
| ByteSpan(mEphemeralKey->Pubkey(), mEphemeralKey->Pubkey().Length()), | ||
| data.msg_R3_Signed.Get(), data.msg_r3_signed_len)); | ||
| data.msgR3Signed.Get(), data.msgR3SignedLen)); |
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If we passed a mutable span instead to the ConstructTBSData, then it may be clearer that it's a max length in msgR3SignedLen?
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Do you mean I should modify ConstructTBSData to take a MutableByteSpan instead of a Pointer + length? that would require more changes in the other parts of the code, it might be better to do it as a follow up.
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Sure, we can do a follow-up.
| @@ -2018,6 +2006,71 @@ CHIP_ERROR CASESession::HandleSigma3a(System::PacketBufferHandle && msg) | |||
| return err; | |||
| } | |||
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| CHIP_ERROR CASESession::ParseSigma3(ContiguousBufferTLVReader & tlvReader, | |||
| Platform::ScopedMemoryBufferWithSize<uint8_t> & msgR3Encrypted) | |||
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Suggest passing a MutableByteSpan. The fact that we are mutating the payload to decrypt in place was never really stated, but it's actually what's happening.
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Actually, it looks like even the alloc is done by this method on the provided msgR3Encrypted. Suggest calling it outMsgR3Encrypted.
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I added comments to the method in the header file, as well as during instantiation of parameters passed to it
I made it like:
CHIP_ERROR CASESession::ParseSigma3(ContiguousBufferTLVReader & tlvReader,
Platform::ScopedMemoryBufferWithSize<uint8_t> & outMsgR3Encrypted,
MutableByteSpan & outMsgR3EncryptedPayload, ByteSpan & outMsgR3Mic)
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tcarmelveilleux
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Jan 20, 2025
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PR #36941: Size comparison from 17ad72e to 1f9cd96 Full report (71 builds for bl602, bl702, bl702l, cc13x4_26x4, cc32xx, cyw30739, efr32, esp32, linux, nrfconnect, nxp, psoc6, qpg, stm32, telink, tizen)
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| MutableByteSpan msgR2EncryptedPayload; | ||
| ByteSpan msgR2Mic; | ||
| SessionParameters responderSessionParams; | ||
| uint16_t responderSessionId; |
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Spec calls this responderSessionID. Why the random casing difference? This applies to some other bits too (resumptionId here and in EncodeSigma2ResumeInputs, responderSessionId in EncodeSigma2ResumeInputs, resumptionId and responderSessionId in ParsedSigma2Resume).
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Well, there seems to be dispute on how should we treat abbreviations with camelCase, treat them like a word or keep them all Capital?
| } | ||
| // Msg2 should only be added to MessageDigest after we construct SaltSigma2 that is used to derive S2K |
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Why? We're not using SaltSigma2 here.... why does this ordering requirement exist?
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because to construct SaltSigma2, we use the MessageDigest/TranscriptHash that only includes Msg1 and doesn't include Msg2 (this happens within CASESession::ConstructSaltSigma2)
| sr2k.KeyHandle(), kTBEData2_Nonce, kTBEDataNonceLength, msg_R2_Encrypted.Get())); | ||
| if (parsedSigma2.responderSessionParamStructPresent) | ||
| { | ||
| SetRemoteSessionParameters(parsedSigma2.responderSessionParams); |
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This used to be after successful decrypt, no? Why the ordering change?
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hmm, is it an issue if we do it before a sucessful decrypt? there seems to be nothing in spec about it?
I wanted to group all the outer sigma-2-struct parts together
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I will move this after signature validation, as it was done before
| SuccessOrExit(err = decryptedDataTlvReader.Get(responderICAC)); | ||
| SuccessOrExit(err = decryptedDataTlvReader.Next(TLV::kTLVType_ByteString, AsTlvContextTag(TBEDataTags::kSignature))); | ||
| } | ||
| std::copy(parsedSigma2TBEData.resumptionId.begin(), parsedSigma2TBEData.resumptionId.end(), mNewResumptionId.begin()); |
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This used to be after signature validation, right? Why the ordering change?
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I just wanted to group the parts related to Sigma2TBEData together.
- Looking at the spec, this is done after signature validation, I will move it there.
- I will also move
SetPeerSessionId(responderSessionId);to after signature validation, as it is like that in the spec (but wasn't the case in the code)
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PR #36941: Size comparison from 17ad72e to 291a38f Increases above 0.2%:
Full report (71 builds for bl602, bl702, bl702l, cc13x4_26x4, cc32xx, cyw30739, efr32, esp32, linux, nrfconnect, nxp, psoc6, qpg, stm32, telink, tizen)
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Overview:
This PR continues the CASESession refactoring efforts to improve testability and robustness, building on:
Key Changes:
1. Refactoring:
2. Hardening and Fixes:
TBSData2SignatureandTBSData3Signature.EndOfContainerTLV elements by ensuringExitContaineris called after TLV-Reading containers TLV Reading of Containers often missed a call to ExitContainer #36959.Testing