galaxy-game/ui/frontend/tests/e2e/fixtures/sign-response.ts

// Helper used by `auth-flow.spec.ts` to forge a Connect-Web-shaped
// `ExecuteCommandResponse` signed with the fixture gateway response
// key. Lives next to the keypair fixture so the e2e file stays
// focused on the UI flow. Connect-Web's default transport uses
// JSON over HTTP/1.1, so the helper emits JSON bytes; the canonical
// signing input is still the binary form defined in
// `ui/core/canon/response.go`.

import { create, toJson, toJsonString } from "@bufbuild/protobuf";
import { webcrypto } from "node:crypto";
import { ExecuteCommandResponseSchema } from "../../../src/proto/edge/v1/edge_gateway_pb";
import {
	FIXTURE_PRIVATE_KEY_PKCS8_BASE64,
	decodeBase64,
} from "./gateway-key";
import { buildResponseSigningInput } from "./canon";

const PROTOCOL_VERSION = "v1";

export interface ForgedResponseInput {
	requestId: string;
	timestampMs: bigint;
	resultCode: string;
	payloadBytes: Uint8Array;
}

let cachedPrivateKey: CryptoKey | null = null;

async function privateKey(): Promise<CryptoKey> {
	if (cachedPrivateKey !== null) {
		return cachedPrivateKey;
	}
	const pkcs8 = decodeBase64(FIXTURE_PRIVATE_KEY_PKCS8_BASE64);
	cachedPrivateKey = await webcrypto.subtle.importKey(
		"pkcs8",
		pkcs8,
		{ name: "Ed25519" },
		false,
		["sign"],
	);
	return cachedPrivateKey;
}

async function sha256(payload: Uint8Array): Promise<Uint8Array> {
	const digest = await webcrypto.subtle.digest("SHA-256", payload);
	return new Uint8Array(digest);
}

/**
 * forgeExecuteCommandResponseJson produces the JSON body of a
 * gateway response that `GalaxyClient.executeCommand` will accept
 * under the fixture public key, encoded the way Connect-Web's
 * default JSON transport expects to receive it.
 */
export async function forgeExecuteCommandResponseJson(
	input: ForgedResponseInput,
): Promise<string> {
	const payloadHash = await sha256(input.payloadBytes);
	const canonical = buildResponseSigningInput({
		protocolVersion: PROTOCOL_VERSION,
		requestId: input.requestId,
		timestampMs: input.timestampMs,
		resultCode: input.resultCode,
		payloadHash,
	});
	const sig = await webcrypto.subtle.sign(
		{ name: "Ed25519" },
		await privateKey(),
		canonical,
	);
	const message = create(ExecuteCommandResponseSchema, {
		protocolVersion: PROTOCOL_VERSION,
		requestId: input.requestId,
		timestampMs: input.timestampMs,
		resultCode: input.resultCode,
		payloadBytes: input.payloadBytes,
		payloadHash,
		signature: new Uint8Array(sig),
	});
	return toJsonString(ExecuteCommandResponseSchema, message);
}

export { toJson };