IBC ConnectionOpenAck fails for solo machine client

[devashishdxt]

Summary of Bug

After creating an IBC solo machine client, the connection handshake fails at ConnectionOpenAck.

For a solo machine, in MsgConnectionOpenAck, we send proof_height, proof_try, proof_client and proof_consensus. On cosmos-sdk side, this function is called to verify all the details of the message. For solo machine, proof_try contains signed connection data, proof_client contains signed client state of tendermint client on solo machine, proof_consensus contains signed consensus state of tendermint client on solo machine and proof_height is the height of the solo machine at which these proofs were created.

Each of these proofs are verified by cosmos chain in these functions:

• VerifyConnectionState
• VerifyClientState
• VerifyClientConsensusState

All these functions are also supplied with proof_height which are verified against the sequence stored in solo machine client state on cosmos chain. But, all the above three functions increment the sequence stored in solo machine client state. here, here and here.

The verification goes fine for the first verification function which is called, i.e., VerifyConnectionState (which increments the sequence in client state). Verification fails in VerifyClientState here because VerifyConnectionState changes the sequence/revision height in client state.

Version

v0.42.4

Steps to Reproduce

Here is the code:

• Solo machine: https://github.com/devashishdxt/ibc-solo-machine
• Cosmos SDK (there was a small bug in cosmos-sdk's solo machine code so I'm currently using my own fork): https://github.com/devashishdxt/cosmos-sdk/tree/solo-machine

To run the solo machine setup:

• Start IBC enabled cosmos-sdk chain (with replaced custom cosmos-sdk fork).
• Start solo machine server cargo run -- start (If you're running cosmos chain locally, all the defaults are set and you don't have to provide any values when starting)
  Next, send AddChainRequest (use bloom RPC to send grpc requests). The defaults are set in a way that you don't have to provide any values if you're running the chain locally.

Finally, to establish connection, call grpc Connect. This will create a client, connection on both cosmos-sdk and solo machine and fails when sending acknowledgement of connection to cosmos-sdk.

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For Admin Use

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[colin-axner]

Thanks for opening the issue and providing a lot of information! We need to change the solo machine verify functions to be a pointer so that incrementing the sequence can be referenced in the call to the client state verify function

[colin-axner]

We won't be backporting this, so the fix won't be included until the first release of the IBC module on this repository (3-4 weeks)

[AdityaSripal]

Thanks for the writeup!