Error reading in an Ed25519KeyIdentity from pem file after bumping agentJS from 0.15.3 to 1.1.1

[ByronBecker]

Describe the bug
Previously, in a NodeJS enviroment calling Ed25519KeyIdentity.fromSecretKey() with a key generated from dfx worked.

After bumping agentJS from ^0.15.3 to ^1.1.1, I now receive the following error.

<path_to_my_project>/node_modules/@noble/curves/src/abstract/utils.ts:134
    throw new Error(`${title} expected ${expectedLength} bytes, got ${len}`);
          ^
Error: private key expected 32 bytes, got 64
    at ensureBytes (<path_to_my_project>/node_modules/@noble/curves/src/abstract/utils.ts:134:11)
    at getExtendedPublicKey (<path_to_my_project>node_modules/@noble/curves/src/abstract/edwards.ts:421:22)
    at Object.getPublicKey (<path_to_my_project>/node_modules/@noble/curves/src/abstract/edwards.ts:435:12)
    at Function.fromSecretKey (<path_to_my_project>/node_modules/@dfinity/identity/src/identity/ed25519.ts:160:31)
    at identityFromPemFile (<path_to_my_project>/scripts/utils.ts:12:29)
    ...

Where the code for forming the identity from the pem file looks like this:

// utils.ts
import { Ed25519KeyIdentity } from "@dfinity/identity";
import { readFileSync } from "fs-extra";
const pemFile = require("pem-file");

export function identityFromPemFile(pemFilePath: string): Ed25519KeyIdentity {
  const rawKey = readFileSync(pemFilePath).toString();
  const buf = pemFile.decode(rawKey);
  if (buf.length !== 85) {
    throw new Error(`expecting byte length 85 but got ${buf.length}`);
  }
  const secretKey = Buffer.concat([buf.slice(16, 48), buf.slice(53, 85)]);
  return Ed25519KeyIdentity.fromSecretKey(secretKey);
}

// Example usage
const identity = identityFromPemFile(<path_to_your_key);

I see that in the 0.20.0 Release Notes you have

this change replaces the package tweetnacl with @noble/curves for Ed25519 curve signatures and validation.

To Reproduce
Steps to reproduce the behavior:

1. Generate an Ed25519KeyIdentity with dfx (old version of dfx, not exactly sure which one 🤷 )
2. Set up a TypeScript NodeJS Project with agent-js 0.15.3 installed and the script from utils.ts above, with your identity file path subbed in
3. Run the script with ts-node, it should succeed
4. Bump agent-js to ^1.1.1, and run the script again. You should see the error message described above.

Expected behavior
Ed25519KeyIdentity.fromSecretKey() should not behave differently between 0.15.3 and agent-js >= 0.20.0

Desktop (please complete the following information):

• OS: OSX
• Node v18.12.1

[ByronBecker]

@krpeacock

For anyone else that runs into this issue, this solution fixed the error for me.

https://forum.dfinity.org/t/using-dfinity-agent-in-node-js/6169/69