CubeSigner TypeScript SDK

CubeSigner is a hardware-backed, non-custodial platform for securely managing cryptographic keys. This repository is the TypeScript SDK for programmatically interacting with CubeSigner services.

CubeSigner background

The Cubist team built CubeSigner to address the key security vs key availability tradeoff: right now, many teams are forced to keep keys available in memory and therefore exposed to attackers, or try to keep keys safe—usually only at rest—at serious latency and engineering cost. CubeSigner addresses this problem by giving developers low-latency access to hardware-backed key generation and signing. During each of these operations, CubeSigner safeguards their users' keys in HSM-sealed Nitro Enclaves—combining cold wallet security with hot wallet speed and simplicity.

Right now, the CubeSigner SDK supports signing for EVM chains like Ethereum and Avalanche, and non-EVM chains Bitcoin and Solana. Support for more chains is in the works!

Installing the SDK

You can install the SDK from npm:

npm install --save "@cubist-labs/cubesigner-sdk"
npm install --save "@cubist-labs/cubesigner-sdk-fs-storage" # support for filesystem-backed sessions

Logging into CubeSigner

Before running the "getting started" examples below (or tests later), you must log into your CubeSigner organization using the cs command-line tool, e.g.,

cs login [email protected] --env '<gamma|prod|...>'

Getting started

[!TIP] For migration from v0.3.* to v0.4.*, please see MIGRATION.md

In this section we are going to walk through a simple CubeSigner setup. We'll create a signing key, then sign some EVM transactions, and then add a security policy to restrict the kinds of transactions that CubeSigner is allowed to sign.

To start, we'll instantiate the top-level CubeSignerClient class from an existing CubeSigner management session already stored on disk (remember, you must already be logged in).

Let's also assume that the following imports are available to all the examples below.

import * as cs from "@cubist-labs/cubesigner-sdk";
import { JsonFileSessionManager, defaultManagementSessionManager } from "@cubist-labs/cubesigner-sdk-fs-storage";
import assert from "assert";

Instantiate CubeSignerClient

The first order of business is to create an instance of CubeSignerClient. We can do that by simply loading a session token from the default location on disk (which is where the cs login command saves it):

const cubesigner = await cs.CubeSignerClient.create(defaultManagementSessionManager());

Alternatively, a CubeSignerClient instance can be created by explicitly providing a session manager:

// Create a session manager backed by a JSON file
const fileStorage = new JsonFileSessionManager(
  `${process.env.HOME}/.config/cubesigner/management-session.json`,
);
await cs.CubeSignerClient.create(fileStorage);

Get User and Org info

We can now obtain some information about the logged-in user and the organization the user belongs to:

const me = await cubesigner.user();
console.log(me);
assert(me.user_id); // each user has a globally unique ID
assert(me.org_ids); // IDs of all organizations this user is a member of
assert(me.org_ids.length === 1); // assume that the user is a member of exactly one org

const org = await cubesigner.org();
assert(await org.enabled()); // assume that the org is enabled

There is a lot more to do with an organization, like creating/listing keys, creating/listing roles, setting up org-wide security policies, etc.

For the rest of this tutorial, we assume the logged-in user is a member of at least one organization.

Create a Key

Next, let's create a key that we'll later use to sign an Ethereum transaction. For that, we need a key of type Secp256k1.Evm.

const secpKey = await org.createKey(cs.Secp256k1.Evm);
assert((await secpKey.owner()) == me.user_id);
assert(await secpKey.enabled());
assert(await secpKey.type(), cs.Secp256k1.Evm);
console.log(`Created '${cs.Secp256k1.Evm}' key ${secpKey.id}`);

Sign an Ethereum transaction

Let's create a dummy EvmSignRequest.

const eth1Request = <cs.EvmSignRequest>{
  chain_id: 1,
  tx: {
    to: "0xff50ed3d0ec03ac01d4c79aad74928bff48a7b2b",
    type: "0x00",
    gas: "0x61a80",
    gasPrice: "0x77359400",
    nonce: "0",
    value: "0x100",
  },
};

It seems we have everything in place to sign this request with the previously created key. However, attempting to do so fails with 403 Forbidden saying something like Session does not have the required scopes...

try {
  console.log("Trying to sign with improper scopes");
  await secpKey.signEvm(eth1Request);
  assert(false, "Must not be allowed to sign without scopes");
} catch (e) {
  assert(`${e}`.includes("Session does not have required scopes"));
}

By default, the sessions created by the CLI cannot perform signing operations. All sessions have a series of scopes which which determine what that session can be used for. We'll talk more about this later, but for now just know that we need a new session with the proper scopes:

let signingClient = await cs.CubeSignerClient.create(
  // declare the "sign:*" scope which allows us to sign using any keys the
  // account has access to
  await cubesigner.org().createSession("readme signing demo", ["manage:key:get", "sign:*"]));
const signingKey = new cs.Key(signingClient, secpKey.cached);
let sig = await signingKey.signEvm(eth1Request);
console.log(sig.data());
assert(sig.data().rlp_signed_tx);

Using ethers.js instead of the SDK directly

If your application uses ethers.js, you can configure it to use CubeSigner to sign transactions.

import { Signer } from "@cubist-labs/cubesigner-sdk-ethers-v6";
import { ethers } from "ethers";

// Create new Signer
const ethersSigner = new Signer(secpKey.materialId, signingClient);
assert((await ethersSigner.getAddress()) === ethers.getAddress(secpKey.materialId));
// sign transaction as usual:
console.log(
  "ethers.js signature:",
  await ethersSigner.signTransaction({
    chainId: 1,
    to: "0xff50ed3d0ec03ac01d4c79aad74928bff48a7b2b",
    value: ethers.parseEther("0.0000001"),
  }),
);

Access control with Role

CubeSigner uses roles to control access to keys when more than one user wants to use them. You can think of roles as groups that give certain users access to certain keys. To get started, let's create a Role and then simply call createSession on it:

// Create a role, implicitly adding ourselves as a member
const role = await org.createRole();

console.log("Adding key to role, then signing an Ethereum transaction");
await role.addKey(secpKey);

// Members of the role can create sessions which can only access keys in the role
const roleClient = await cs.CubeSignerClient.create(
  // Role sessions implicitly have the "sign:*" scope
  await role.createSession("readme")
);
console.log(`Created client for role '${role.id}'`);

Set security policies

When we add a Secp256k1.Evm key to a role (as we did above), a client associated with that role allows us to sign any Ethereum transaction with that key. If that seems too permissive, we can attach a security policy to restrict the allowed usages of this key in this role.

For example, to restrict signing to transactions with a pre-approved recipient, we can attach a TxReceiver policy to our key:

console.log("Setting transaction receiver policy");
await secpKey.setPolicy([{ TxReceiver: "0xff50ed3d0ec03ac01d4c79aad74928bff48a7b2b" }]);
console.log("Signing transaction");
const roleKey = new cs.Key(roleClient, secpKey.cached);
sig = await roleKey.signEvm(eth1Request);
assert(sig.data().rlp_signed_tx);

Try changing the transaction receiver and verify that the transaction indeed gets rejected:

console.log("Signing a transaction to a different receiver must be rejected");
try {
  await roleKey.signEvm({
    chain_id: 1,
    tx: <any>{
      ...eth1Request.tx,
      to: "0x0000000000000000000000000000000000000000",
    },
  });
  assert(false, "Must be rejected by policy");
} catch (e) {
  assert(`${e}`.includes("Transaction receiver not allowed by policy"));
}

Warning Setting new policies overwrites the previous ones. Call Key::appendPolicy instead of Key::setPolicy to append to existing policies.

Sign a raw blob

The CubeSignerClient class exposes the signBlob method, which signs an arbitrary (raw, uninterpreted) bag of bytes with a given key. This operation, however, is not permitted by default; it is permanently disabled for BLS keys, and for other key types it can be enabled by attaching an "AllowRawBlobSigning" policy:

// Create a new Ed25519 key (e.g., for Cardano) and add it to our roleClient's role
const edKey = await org.createKey(cs.Ed25519.Cardano);
await role.addKey(edKey);
console.log(`Created '${await edKey.type()}' key ${edKey.id} and added it to role ${role.id}`);

// Sign raw blobs with our new ed key and the secp we created before
for (const key of [edKey, secpKey]) {
  console.log(`Confirming that raw blob with ${await key.type()} is rejected by default`);
  const roleKey = new cs.Key(roleClient, key.cached);
  const blobReq = <cs.BlobSignRequest>{
    message_base64: "L1kE9g59xD3fzYQQSR7340BwU9fGrP6EMfIFcyX/YBc=",
  };
  try {
    await roleKey.signBlob(blobReq);
    assert(false, "Must be rejected by policy");
  } catch (e) {
    assert(`${e}`.includes("Raw blob signing not allowed"));
  }

  console.log("Signing raw blob after adding 'AllowRawBlobSigning' policy");
  await key.appendPolicy(["AllowRawBlobSigning"]);
  const blobSig = await roleKey.signBlob(blobReq);
  console.log(blobSig.data());
  assert(blobSig.data().signature);
}

Warning When signing a raw blob with a Secp256k1 key, the blob MUST be the output of a secure hash function like SHA-256, and must be exactly 32 bytes long. This is a strict requirement of the ECDSA signature algorithm used by Bitcoin, Ethereum, and other blockchains. Signing any byte string that is not the output of a secure hash function can lead to catastrophic security failure, including completely leaking your secret key.

Trying to sign an invalid message with a secp key will fail with 400 Bad Request saying Signature scheme: InvalidMessage.

Session Management

In the above examples we've used 3 different sessions:

1. A management session that we created using the CLI
2. A signing session that we created using (1)
3. A role session that we created used (1)

All CubeSignerClients require a valid session in order to operate. In this section we'll dive into the specifics of sessions in the TypeScript SDK.

Loading from disk

If you already have an active session in cs (the CubeSigner CLI), you can load it into the TypeScript SDK with a simple helper (as we did earlier).

await cs.CubeSignerClient.create(defaultManagementSessionManager())

Or we can use the CLI to create our own session explicitly for our JavaScript client:

cs session create --role-id $ROLE_ID --scope sign-all --output json > session.json

Then we can load it like so:

try {
  await cs.CubeSignerClient.create(new JsonFileSessionManager("./session.json"));
} catch {
  console.error("Unable to find file")
}

Loading from Memory

If you already have the session information (SessionData in Typescript) in memory, you can load that directly into a client.

// Get the session data we want to use with the client
const sessionData: cs.SessionData = await role.createSession("readme");
await cs.CubeSignerClient.create(new cs.MemorySessionManager(sessionData))
// or, for short
await cs.CubeSignerClient.create(sessionData)

[!WARNING]
Clients created this way will automatically refresh the session. If you try to use this session with another client, they will both try to refresh, leading to failures.

Managers, Storage and Refreshing

As we've seen in the examples above, all CubeSignerClients are constructed using the create constructor. The create constructor accepts either raw SessionData or a SessionManager. So far we've seen two different session managers:

• JsonFileSessionManager
• MemorySessionManager

These managers are responsible for keeping your session tokens refreshed and (optionally) persisted. Whenever your session tokens are refreshed, JsonFileSessionManager will write the new tokens to disk.

More complex managers can be written by implementing the SessionManager interface.

Create a session for an OIDC user

CubeSigner supports the OIDC standard for authenticating third-party users.

First, we need an OIDC token. We can get one from Google or any other supported OIDC issuer! For the purpose of this example, we'll assume the OIDC token is stored in the OIDC_TOKEN environment variable

import * as dotenv from "dotenv"; // npm install [email protected]
dotenv.config();

const oidcToken = process.env["OIDC_TOKEN"];
assert(oidcToken);

Before we can use the OIDC token for authentication, we must add an org policy to allow the particular issuer/audience pair from the token.

const oldOrgPolicy = await org.policy();
const oidcPayload = JSON.parse(atob(oidcToken.split(".")[1].replace(/-/g, "+").replace(/_/g, "/")));
const oidcAuthSourcesPolicy = {
  OidcAuthSources: {
    [oidcPayload.iss]: [oidcPayload.aud],
  },
};
console.log("Setting org policy", oidcAuthSourcesPolicy);
await org.setPolicy([oidcAuthSourcesPolicy]);

Finally, exchange the OIDC token for a session.

const oidcSessionResp = await cs.CubeSignerClient.createOidcSession(
  cubesigner.env,
  org.id, // org id to log into
  oidcToken,
  ["manage:mfa:*", "sign:*"] // scopes for the session 
);
const oidcClient = await cs.CubeSignerClient.create(oidcSessionResp.data());

Info For full details on how to use this SDK to create a CubeSigner account for a third-party user and then exchange a valid OIDC token CubeSigner session, check out the OIDC Example.

Set up TOTP for a user

To manage a user we need a session bound to that user. It doesn't matter if that user is native to CubeSigner or a third-party OIDC user. For that purpose, in this section we are going to use the previously created oidcCubeSigner instance.

To set up TOTP, we first call the resetTotpStart method to initiate a TOTP reset procedure.

console.log(`Setting up TOTP for user ${me.email}`);
let totpResetResp = await oidcClient.resetTotp();

If the user has already configured TOTP (or any other form of MFA), this response will require multi factor authentication. In that case, for example, call totpApprove and provide the code for the existing TOTP to proceed:

import { authenticator } from "otplib"; // npm install [email protected]

let totpSecret = process.env["CS_USER_TOTP_SECRET"]!;
if (totpResetResp.requiresMfa()) {
  console.log("Resetting TOTP requires MFA");
  const code = authenticator.generate(totpSecret);
  totpResetResp = await totpResetResp.totpApprove(oidcClient, code);
  assert(!totpResetResp.requiresMfa());
  console.log("MFA approved using existing TOTP");
}

The response contains a TOTP challenge, i.e., a new TOTP configuration in the form of the standard TOTP url. From that url, we can generate a QR code to present to the user, or create an authenticator for automated testing.

const totpChallenge = totpResetResp.data();
assert(totpChallenge.url);

To complete the challenge, we must call resetTotpComplete and provide the TOTP code matching the TOTP configuration from the challenge:

totpSecret = new URL(totpChallenge.totp_url).searchParams.get("secret");
assert(totpSecret);
await totpChallenge.answer(authenticator.generate(totpSecret));

After TOTP is configured, we can double check that our authenticator is generating the correct code by calling verifyTotp

console.log(`Verifying current TOTP code`);
let code = authenticator.generate(totpSecret);
await oidcClient.verifyTotp(code);

We can also check that the user's profile now indeed includes Totp as one of the configured MFA factors.

const mfa = (await oidcClient.user()).mfa;
console.log("Configured MFA types", mfa);
assert(mfa.map((m) => m.type).includes("totp"));

Configure MFA policy for signing

We've already discussed assigning a security policy to a key; requiring multi-factor authentication is another such policy.

Let's update our secpKey key to require an additional approval via TOTP before anything may be signed with that key:

console.log(`Require TOTP for key ${secpKey.materialId}`);
await secpKey.appendPolicy([{ RequireMfa: { count: 1, allowed_mfa_types: ["Totp"] } }]);

Now, when we call any signing operation on secpKey, we'll receive 202 Accepted instead of 200 Ok. The response body contains an MFA ID, which we can use to fetch and inspect the associated MFA request, see how many approvals it requires, what kind of MFA factors it allows, etc. Instead, since we know that our key requires TOTP, we can just call totpApprove on the response and pass the current TOTP code to it; if the code is correct, the call will succeed and return the signature.

console.log(`Signing a transaction now requires TOTP`);
const oidcKey = new cs.Key(oidcClient, secpKey.cached);
let resp = await oidcKey.signEvm(eth1Request);
assert(resp.requiresMfa());

console.log(`Approving with TOTP code`);
code = authenticator.generate(totpSecret);
resp = await resp.totpApprove(oidcClient, code);
assert(!resp.requiresMfa());
console.log(resp.data());
assert(resp.data().rlp_signed_tx);

Clean up

Once we are done, we can revoke the signer session and delete the role we created.

console.log("Cleaning up");
await signingClient.revokeSession();
await roleClient.revokeSession();
await role.delete();

As of now, deleting keys is not supported.

Building the SDK

npm install
npm run build

Running the SDK tests

After logging in, you can just run:

npm test

The tests will create some temporary keys and roles (in the organization of the signed-in user), then sign some messages, and finally clean (most of it) up.

License

Copyright (C) 2022-2023 Cubist, Inc.

See the NOTICE file for licensing information.