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ADR 004: IBC Whitelisting #696

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ADR 004: IBC Whitelisting #696

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77934d8
feat: add initial vesion of ADR for whitelisting chains
rahulghangas Sep 9, 2022
70b7f6e
chore: remove markdown lint
rahulghangas Sep 15, 2022
ffabfbd
chore: typo
rahulghangas Sep 15, 2022
b407e4b
chore: typo
rahulghangas Sep 15, 2022
35694cc
chore: only use allowlist
rahulghangas Sep 25, 2022
e3b6219
chore: rename ADR-004-ibc whitelist to ADR-004-ibc-allowlist
rahulghangas Sep 25, 2022
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27 changes: 27 additions & 0 deletions docs/architecture/ADR-004-IBC-whitelist.md
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# ADR 004: IBC Whitelist/Allowlist
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[optional] one term is sufficient to describe this. Slight preference for Allowlist because rails/rails#33677

Suggested change
# ADR 004: IBC Whitelist/Allowlist
# ADR 004: IBC Allowlist

Note: accepting this suggestion implies updating the filename too. Preferably: adr-004-ibc-allowlist.md to conform to #772


## Terminology

All terminology is defined in [ICS 024](https://github.com/cosmos/ibc/tree/main/spec/core/ics-024-host-requirements) and some references are from corresponding implementation of [ICS 002](https://github.com/cosmos/ibc/tree/main/spec/core/ics-002-client-semantics) in [ibc-go](https://github.com/cosmos/ibc-go/blob/da1b7e0aaf4b7d466b1a7d1ed4f5d81149ff1d5b/modules/core/02-client)

## Changelog

- 2022-03-03: Initial Commit

## Context

While enabling IBC, we want to connect, and allow messages from selected chains. However, we don't want the ability for an arbitrary entity to create an IBC connection with a zone. This is so that we can keep the state machine as minimal and focused as possible.

ICS specification indicates that is possible by providing a custom `validateClientIdentifier`, but no such functionality exists currently.

Secondly, the ICS specification dictates that `createClient` takes in an `Identifier`. A potential solution could be to create a store for allowed `Identifiers` at genesis, and reject creation of clients for invalid identifiers. However, this is not true for the current state of the implementation. Rather, client ID is generated from an incremental counter `NextClientSequence` and the client type.

## Proposal

Fork IBC, and create a store of whitelisted public keys. Only `createClient` txns that are signed by private keys corresponding to whitelisted/stored public keys are deemed valid, and the rest are invalidated. Specific keys will only be required for client creation, and rest of IBC will work as is.
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while a list of keys would probably be simplest, I'm guessing that it's also possible to rely strictly on governance?

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Yes, this is possible. Creation of clients can be strictly restricted to governance

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@rahulghangas rahulghangas Sep 14, 2022 •
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Note: this still requires us having to fork IBC (iiuc)


## Alternative approaches

1. Simplest solution is fork to IBC, and add a small change to disallow creation/registration of new clients. Then we can create clients for the chains that we want to allow at genesis, and effectively create a whitelist. However, adding new clients or removing clients is not feasible under this.
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agree that relying on hardforks for any changes isn't desirable imo. Not being able to move tokens for a few weeks if something weird happens seems like a non-starter.


2. Add a middleware to revert packets from non-whitelisted chains. This still adds state bloat since clients and corresponding connections are allowed to be established, but adds economic incentive in terms of lost gas from the malicious user/actor