sign-evmos-keplr.js

import { SigningStargateClient } from '@cosmjs/stargate'
import { fromBase64 } from "@cosmjs/encoding";
import {
  makeAuthInfoBytes,
  makeSignDoc,
} from '@cosmjs/proto-signing'
import { Int53, Uint53 } from "@cosmjs/math";
import { Any } from "cosmjs-types/google/protobuf/any";
import { PubKey } from "cosmjs-types/cosmos/crypto/secp256k1/keys";
import { TxRaw } from "cosmjs-types/cosmos/tx/v1beta1/tx";

async function sign(
  api,
  client, // SigningStargateClient
  signer, // keplr OfflineSigner
  chainId,
  signerAddress,
  messages,
  fee,
  memo,
) {
  // Query account info, because cosmjs doesn't support Evmos account
  const { accountNumber, sequence } = await api.getAccountInfo(signerAddress) // GET /cosmos/auth/v1beta1/accounts/{address}
  const accountFromSigner = (await signer.getAccounts()).find(
    (account) => account.address === signerAddress,
  );
  if (!accountFromSigner) {
    throw new Error("Failed to retrieve account from signer");
  }
  pubkeyBytes = accountFromSigner.pubkey

  // Custom typeUrl for EVMOS
  const pubk = Any.fromPartial({
    typeUrl: "/ethermint.crypto.v1.ethsecp256k1.PubKey",
    value: PubKey.encode({
      key: pubkeyBytes
    }).finish(),
  })

  const txBodyEncodeObject = {
    typeUrl: "/cosmos.tx.v1beta1.TxBody",
    value: {
      messages: messages,
      memo: memo,
    },
  };
  const txBodyBytes = client.registry.encode(txBodyEncodeObject);
  const gasLimit = Int53.fromString(fee.gas).toNumber();
  const authInfoBytes = makeAuthInfoBytes([{ pubkey: pubk, sequence }], fee.amount, gasLimit);
  const signDoc = makeSignDoc(txBodyBytes, authInfoBytes, chainId, accountNumber);
  const { signature, signed } = await signer.signDirect(signerAddress, signDoc);

  // returns txBytes for broadcast
  return TxRaw.encode({
    bodyBytes: signed.bodyBytes,
    authInfoBytes: signed.authInfoBytes,
    signatures: [fromBase64(signature.signature)],
  }).finish();
}