How to handle SIGN_MODE_TEXTUAL spec updates

[amaury1093]

Summary

Define how to handle SIGN_MODE_TEXTUAL spec updates.

Problem Definition

We allow SIGN_MODE_TEXTUAL's spec to be updated, as state-machine-breaking changes. However, we need to define how to coordinate these updates between node and clients.

Take an example: imagine SDK v0.48 uses SIGN_MODE_TEXTUAL v1 (current spec), but v0.49 uses v2 (small value renderer formatting change). If a JS client uses v1 to generate to sign doc and the signature, and sends to a v2 node (or vice versa), then we'll get the usual hard-to-debug message:

signature verification failed; verify nonce, acct num and chain id.

Find a solution that:

1. Allows coordination between clients and node on which spec version to use
2. Allows easy debugging of failed signatures

Proposal

During yesterday's Textual sync, multiple solutions were discussed:

• Proposals 1a and 1b: put the version info in the Tx itself
• Proposals 2a and 2b: put the version info into the Textual SignDoc

➡️ Proposal 1a: Use SIGN_MODE_TEXTUAL_V{N}

Create a new sign mode with a version suffix each time there's a spec change. The first one can be SIGN_MODE_TEXTUAL, but subsequent ones are _V2 etc.

• Pros:
  • solves 1 & 2 in the easiest possible way
• Cons:
  • multiple Textual sign modes, slight code duplication

In this case, we should also probably disallow one node being able to activate two different SIGN_MODE_TEXTUAL versions at the same time.

➡️ Proposal 1b: Add a new field in the Tx struct

Similar to Proposal 1a, but put the version somewhere else in the Tx, e.g.

  message Single {
    // mode is the signing mode of the single signer
    cosmos.tx.signing.v1beta1.SignMode mode = 1;

+   // Additional info for the sign mode
+   string additional_info = 2;
  }

• Pros:
  • solves 1 & 2
  • we keep one single SIGN_MODE_TEXTUAL enum
  • backwards compatible
• Cons:
  • modification of the Tx struct

➡️ Proposal 2a: Put the version in the Textual sign doc (not shown to user)

After #15282, Textual's sign doc is the CBOR encoding of:

type SignDoc struct {
  screens []Screen
}

it would be easy to add a version uint64 field there.

• Pros:
  • solves 2, debuggability is slightly worse than 1a and 1b, but still doable
  • one SIGN_MODE_TEXTUAL enum
• Cons:
  • problem 1 needs a separate solution, though should be easy to implement (e.g. a simple mapping SDK version <-> Textual spec Version should suffice for JS clients, or in the future, a gRPC endpoint).

➡️ Proposal 2b: Show the spec version as an expert screen

Same as 2b, but put the spec version in one of the Ledger screens (expert mode only).

• Pros:
  • slight improvement over 2a's debuggability
• Cons:
  • additional screen