Fetch Aggregated Signature from Istanbul block header

[waymobetta]

Signature Verification parameters that are used to call the bridge smart contract method execute are malformed, i.e. the signature field is empty and therefore not being passed.

Description

Previously, the signature of the block that is to be proved was being fetched from the block header (blockData.EpochSnarkData().Signature) which was empty because according to the Celo team, the EpochSnarkData is only present in epoch blocks.

The aggregated signature, however, should be present in every block, and can be found within the extra data.

Related Issue Or Context

Closes: #102

How Has This Been Tested? Testing details.

• I was able to log the Signature utils.SignatureVerification.Signature and it returns a valid signature

Types of changes

• [X] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation

Checklist:

• [X] I have commented my code, particularly in hard-to-understand areas.
• [X] I have ensured that all acceptance criteria (or expected behavior) from issue are met
• [ ] I have updated the documentation locally and in chainbridge-docs.
• [x] I have added tests to cover my changes.
• [x] I have ensured that all the checks are passing and green, I've signed the CLA bot

[github-actions[bot]]

Go Test coverage is 40.8 %\ :sparkles: :sparkles: :sparkles:

[github-actions[bot]]

Go Test coverage is 40.8 %\ :sparkles: :sparkles: :sparkles:

[github-actions[bot]]

Go Test coverage is 40.8 %\ :sparkles: :sparkles: :sparkles:

[github-actions[bot]]

Go Test coverage is 40.7 %\ :sparkles: :sparkles: :sparkles:

[github-actions[bot]]

Go Test coverage is 40.7 %\ :sparkles: :sparkles: :sparkles:

[github-actions[bot]]

Go Test coverage is 40.8 %\ :sparkles: :sparkles: :sparkles:

[waymobetta]

This PR has been overly complicated for no reason- the fix was straightforward as we just import a utility function from Celo's celo-blockchain library to use for extracting the IstanbulExtra data from the block header.

The fix worked; the tests still did not pass.

Things got complicated when needing to utilize an interface in order to leverage gomock. Despite attemping to do so, the main issue- which was that the dummy block being used within the tests did not contain IstanbulExtra data- became lost in complexity behind needing to implement an interface, especially when the IstanbulExtra data was ignored anyway.

Example:

    extra, err := types.ExtractIstanbulExtra(block.Header())
    s.Nil(err)

    _ = utils.NewFungibleTransfer(
        listener.cfg.ID,
        destID,
        nonce,
        prop.ResourceID,
        &utils.MerkleProof{
            TxRootHash: block.TxHash(),
            Nodes:      proof,
            Key:        key,
        },
        &utils.SignatureVerification{
            AggregatePublicKey: pk,
            BlockHash:          block.Header().Hash(),
            Signature:          extra.AggregatedSeal.Signature,
        },
        prop.Amount,
        prop.DestinationRecipientAddress,
    )

A fix was pushed to create a new type of dummy block (replacing the existing) one that included InstanbulExtra data (borrowed from the celo-blockchain tests), which was then used to satisfy two checks that are performed on the extra field of the block, including:

1. an IstanbulExtraVanity length check
2. an RLP decode check on the raw data

After satisfying these requirements with the creation of the new dummyBlockWithIstanbulExtra, the tests passed.

[github-actions[bot]]

Go Test coverage is 40.8 %\ :sparkles: :sparkles: :sparkles:

[github-actions[bot]]

Go Test coverage is 40.8 %\ :sparkles: :sparkles: :sparkles:

[P1sar]

celo-blockchain tests

I beginning i mentioned that you should try build block header with valid Extra for tests not without reason before trying to use gomocks.

[github-actions[bot]]

Go Test coverage is 40.8 %\ :sparkles: :sparkles: :sparkles: