Starkcheck: Back-end trace analyser

[CremaFR]

repo of the project

https://github.com/LedgerHQ/StarkCheck

[CremaFR]

Initial specs/idea:

• Must be deployable easily outside Ledger
• Must be open source
• Must be stateless

Considering all the point above this back-end will have one endpoint /checks which takes a raw transactions and a policy as parameters and returns a message with a signed transaction hash.

Inputs: Transaction as defined here: https://docs.starknet.io/documentation/architecture_and_concepts/Blocks/transactions/ Policy is a list of

• ContractAssets -> myContract -> Amount (for ERC20)
• ContractAssets -> myContract -> NFTsIDs (for ERC721)

The back run simulate transaction on a node and analyse the trace to determine the risks. The back should also check for approvals (and returns warning if an address in the policy is spotted in the trace).

[CremaFR]

Some addresses and selectors to checks

eth erc20 addr: 0x72df4dc5b6c4df72e4288857317caf2ce9da166ab8719ab8306516a2fddfff7

approve selector: 0x219209e083275171774dab1df80982e9df2096516f06319c5c6d71ae0a8480c transferFrom selector: 0x41b033f4a31df8067c24d1e9b550a2ce75fd4a29e1147af9752174f0e6cb20 transfer selector: 0x83afd3f4caedc6eebf44246fe54e38c95e3179a5ec9ea81740eca5b482d12e

Some interesting transaction hash to check for "complex" calldata: https://testnet.starkscan.co/tx/0x02e6c38c8579fef5d530945d98a0f7905452a6e764658daf4e108d211ddffd06#internal-calls

[CremaFR]

The contract account's plugin will be updated to have the following:

• 2 new variable state:

  • StarkCheck pubkey to verify the OK signature
  • A policy hash to ensure the correct policy was sent and checked (If we can manage it offchain it's better but how?)
  • Changing those values is a timegated operation

• The signature field will be updated to include

  • The starkCheck signature
  • [Optionnal] a second signature to ACK you want to perform an operation that does not comply with the policy

• The big question is where to save the policy and how to restore one.

  • Stored: In the brower storage
  • Share the policy to other device (QR code or paste policy?)
  • Changing policy is a quick timegate (one to two hours? in order to not block for a long time an user if the browser storage is cleared)

[yogh333]

Draft sequence diagrams:

1. Setting a policy:
2. Checking a policy:

To be reviewed

[yogh333]

Updated Sequence diagrams:

1. Set policy:
2. Check policy:

[qd-qd]

In the following days, this issue will be detailed by all the tasks listed in the Starkcheck module project and then closed.