Cosmos Signer

This application can sign potentially arbitrary off-line generated transactions from any Cosmos-SDK based blockchain. It is itself technically a Cosmos-SDK application, but it is not meant to be run as a blockchain node, rather as a standalone application. All the node-related code has been stripped out or the functionality has been disabled.

The core component is the x/signer module, which is canonically a Cosmos-SDK module, however it just provides the CLI commands to sign transactions in the x/signer/client/cli package. The CLI code extends and-reuses the x/auth/client/cli package from the Cosmos-SDK, which already provides code to sign transactions. The only purpose of the x/signer module is to allow dynamic registration of the proto types required to encode and decode the provided transactions.

Since the x/signer module is a Cosmos-SDK module, it is also possible to add its functionality to any other compatible Cosmos-SDK application. However, the utility of such module might be questionable on a specific chain, where generic-purpose signers are generally not needed.

How

The core functionality is available in the x/signer/client/cli package. Other important modifications for the CLI itself are available at cmd/cosmos-signer/cmd, in particular in commands.go.

To allow dynamic registration of the proto types, the x/signer module uses go plugins to load the required types from per-chain plugins.

These plugins are built - as of now - by ripping out and modifying the original chain source code, of which we just need the types packages of the used modules, and replacing the go.mod with the same go.mod as the comos-signer (plus adaptations, which suggest this process might not be easily automatable). The plugin main.go will have to look something like this:

package main

import (
    govtypes "github.com/atomone-hub/govgen/x/gov/types"
)

var Govgen_gov_v1beta1_RegisterLegacyAminoCodec = govtypes.RegisterLegacyAminoCodec
var Govgen_gov_v1beta1_RegisterInterfaces = govtypes.RegisterInterfaces

func main() {}

Examples can be found for gaia and govgen in the plugins directory.

In both cases, we used - or adapted the code to support - Cosmos-SDK v0.50.x, and synchronized any other dependency with the root application. This was done as an intentional excercise to test compatibility across different Cosmos-SDK versions, and to check complexity and feasibility of getting to a truly generic signer, which should somehow be "version-agnostic".

The challenge is that go plugins - although seem very appropriate for this task - need to be built with the exact same dependencies as the root application, which is not necessarily easy to achieve in the context of Cosmos-SDK apps.

Build

To build the signer, run:

./build.sh

which will build the signer and the plugins for gaia and govgen, and make them available in the build directory.

Run

The application should be familiar to anyone who has used the Cosmos-SDK CLI. The only available command for now is tx sign (and the keys commands for keys management). The interface is the same as the x/auth-provided commands, but --offline flag is mandatory, as obviously the signer is meant to be used to sign offline-generated transactions. There are also a few notable additions of flags that are available with the cosmos signer:

• --bech32-prefix: to specify the bech32 prefix that we need to use for encoding the addresses. It defaults to cosmos, and can be used throghout the whole application (e.g. even for keys commands).
• --prefix-pub: to specify the prefix for the public key. It defaults to pub, and can be used throghout the whole application (e.g. even for keys commands).

and specifically for the tx sign command:

• --plugins-dir: to specify the directory where the plugins are located. It is a mandatory flag.