ABCI2.0 use-cases collection #448

adizere · 2023-03-02T17:27:54Z

adizere
Mar 2, 2023
Maintainer

Two questions from a user on Telegram:

Is it possible to add some logic that adds some bytes to the Block header (using ABCI++? ProcessProposal seems promising but only works on transactions)

Is it possible to get the current block proposer to sign a message (bytes) and include that signature as part of the block.

Don't currently see if it's ever possible for an application running over ABCI to request such an action to be done, and would love some guidance on this front.

sergio-mena · 2023-03-02T18:13:30Z

sergio-mena
Mar 2, 2023
Collaborator

[I imagine you mean PrepareProposal, since the data passed to the application in ProcessProposal is read-only] This is not possible in ABCI 1.0 or ABCI 2.0, unfortunately. But we can take this as a feature request and analyze its feasibility. Actually, this looks similar to one of the reasons Celestia need to keep a fork. So solving this would probably make the Celestia folks happy.
There is a way to do this in both ABCI 1.0 and ABCI 2.0. Since the application can add its own transactions during PrepareProposal, one could imagine the following solution:
- the application defines a new transaction type that contains the required data (in your example: the message and its signature)
- the application's spec sets the following rule: all blocks MUST have exactly one transaction of the new type, and the signature inside it must be valid
- in PrepareProposal, the application makes sure that exactly one transaction of the new transaction type in the list of transactions it returns to CometBFT in ResponsePrepareProposal
- in ProcessProposal, the application rejects any proposed block that does not have exactly one transaction of the new type with a valid signature

This is an example to illustrate the idea, so YMMV.

3 replies

lasarojc Mar 3, 2023

While we cannot add anything directly into the header today, the approach that @sergio-mena proposes in 2. could also be used to simulate what you need in 1. That is, you could have a special transaction, containing the "extended header information" added to the block during PrepareProposal. The definition of a valid block may restrict the number of such special transactions according to your needs, for example requiring exact one or at most one such transaction. Again, YMMV, but if you think this approach does not work, please share more about your use case.

AmitPr Mar 8, 2023

Hi! Yeah this is basically where I ended up ending up reaching myself. The only missing piece to the puzzle is figuring out how to get the signature. Ideally, I could ask the underlying application to sign the transaction from my Cosmos SDK module, for example with their validator consensus key. Any idea what I could do for this last part?

I know some solutions use an auxilliary process that submits transactions to the node, but that does feel somewhat clunky.

lasarojc Jun 27, 2023

The test app in our test framework does some signature manipulation; maybe you can get some ideas there. (https://github.com/cometbft/cometbft/blob/main/test/e2e/app/app.go)
No much experience in the SDK to comment on using it.

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adizere Mar 2, 2023 Maintainer

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sergio-mena Mar 2, 2023 Collaborator

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lasarojc Mar 3, 2023

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AmitPr Mar 8, 2023

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lasarojc Jun 27, 2023

adizere
Mar 2, 2023
Maintainer

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sergio-mena
Mar 2, 2023
Collaborator