Proving bug in Dex

[bkase]

This happens when creating a proof for Dex.redeemLiquidity()

In the Pickles wrap prover, the compute_witness step (in Plonk_constraint_system) fails when it tries to access external_vars at out-of-bounds indices.

The fact that this is the wrap prover makes the issue more mysterious because we wouldn't expect the wrap circuit to be influenced by a badly written snarkyjs circuit (which, for example, created less witnesses than expected or similar)

[Trivo25]

Quick update: The bug seems to be caused by the method TokenContract.approveUpdateAndSend(zkappUpdate: AccountUpdate, to: PublicKey, amount: UInt64), more specifically, the AccountUpdate as argument.

[Trivo25]

The bug only appears when we try to prove an AccountUpdate (pass it as an argument to another zkApp method) where the authorization is either None_given or Proof, whereas signing the AccountUpdate (authorization: signature) works.

The bug appears when trying to prove the transaction (add the missing proofs to all AccountUpdates via the provers array https://github.com/MinaProtocol/mina/blob/develop/src/lib/snarky_js_bindings/lib/snarky_js_bindings_lib.ml#L2215)

panicked at 'called `Result::unwrap()` on an `Err` value: Error { kind: UnexpectedEof, message: "failed to fill whole buffer" }', src/arkworks/pasta_fp.rs:59:21 

this error can be traced back to compute_witness and https://github.com/MinaProtocol/mina/blob/develop/src/lib/crypto/kimchi_backend/common/plonk_constraint_system.ml#L464

where it seems like x is not being computed correctly(?) https://github.com/MinaProtocol/mina/blob/develop/src/lib/crypto/kimchi_backend/common/plonk_constraint_system.ml#L444