Hacktoberfest 2026: the issues maintainers tagged for October, open and beginner-friendly. Browse Hacktoberfest issues

M2M Token only authentication in Clerk Middleware

Open
  • Is something wrong?
#9,981 0 comments 0 reactions 1 assignee View on GitHub

Maintainers usually reply within 1 day

@wobsoriano is already working on this.

Since Sep 29, 2026.

Assessment

This issue has not been assessed yet.

Description

needs-triage
Preliminary Checks
Reproduction

https://github.com/x-delfino/clerk-fastify-issue-repro

Publishable key

pk_test_dG91Y2hlZC1mb3dsLTk5MDYuY2xlcmsuYWNjb3VudHMuZGV2JA

Description

I'm trying to use M2M tokens to authenticate one machine to another, without any subsequent backend API access. I'm testing this with the clerk fastify plugin, but I don't think the issue is necessarily specific to that package

Steps to reproduce:

  1. Create M2M Machines in Clerk:
  • MachineA: no scopes
  • MachineB: scope for MachineA
  1. Setup workspace (using MachineA secret key):
git clone https://github.com/x-delfino/clerk-fastify-issue-repro
cd clerk-fastify-issue-repro
pnpm install
export CLERK_MACHINE_SECRET_KEY="ak_XXXXXXXXX"
pnpm run serve
  1. Generate token for MachineB
  2. make HTTP request:
TOKEN="MACHINE_B_TOKEN"
curl -H "Authorization: Bearer $TOKEN" localhost:8080/protected

Expected behavior:

To receive response:

{"message":"Machine authenticated successfully","subject":"mch_XXXXXXXXX","scopes":["mch_XXXXXXXXX"]}

Actual behavior:

Response received:

{"statusCode":500,"error":"Internal Server Error","message":"Publishable key is missing.\n\nTo create a new Clerk app, run:\nnpx clerk@latest init\n\nTo use an existing Clerk app, run:\nnpx clerk@latest link\nnpx clerk@latest env pull\n\nFor production keys, run:\nnpx clerk@latest env pull --instance prod\n\nOr copy keys from https://dashboard.clerk.com/~/api-keys into your .env file."}

Providing CLERK_PUBLISHABLE_KEY changes the response to:

{"statusCode":500,"error":"Internal Server Error","message":"Missing Clerk Secret Key. Go to https://dashboard.clerk.com and get your key for your instance."}

Detail:

The clerk middleware for fastify hardcodes the acceptsToken to 'any':

https://github.com/clerk/javascript/blob/dfb620474e85fa36f8925e3f3091b5911c080492/packages/fastify/src/withClerkMiddleware.ts#L110-L116

When the token is then processed, as it's not explicitly M2MToken or ApiKey - it tries to load the publishable key:

https://github.com/clerk/javascript/blob/26feba7c666f48cc4f8d3ecf1ebfd3290cbdf679/packages/backend/src/tokens/authenticateContext.ts#L86-L98

I patched the fastify clerk middleware to allow the acceptsToken key to be provided:

    const requestState = await clerkClient.authenticateRequest(req, {
      ...clerkOptions,
      secretKey,
      publishableKey,
      proxyUrl: resolvedProxyUrl,
      // acceptsToken: 'any',
    });

Allowing me to update my sample code to:

fastify.register(clerkPlugin, { acceptsToken: "m2m_token" })

Allowing me to receive and validate M2M tokens using M2M tokens only

However, this isn't type correct. ClerkFastifyOptions, through a chain of intersections, doesn't pull in acceptsToken from AuthenticateRequestOptions

https://github.com/clerk/javascript/blob/2ee976bb66b7c112ae5bec5605a5bb42736c7e01/packages/backend/src/tokens/factory.ts#L8-L22

I'm not sure the best way to proceed from here as changes may affect more than fastify

Environment
System:
    OS: macOS 26.5
    CPU: (10) arm64 Apple M4
    Memory: 134.00 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 26.10.0 - /nix/store/xs1l2nzllqp7imnhpd2n6cm0m70yzp10-nodejs-26.10.0/bin/node
    npm: 11.19.1 - /nix/store/xs1l2nzllqp7imnhpd2n6cm0m70yzp10-nodejs-26.10.0/bin/npm
    pnpm: 11.27.0 - /nix/store/gjkd8wjh079v7i5j2rb8y0b5r19addpa-pnpm-11.27.0/bin/pnpm
  Browsers:
    Safari: 26.5
  npmPackages:
    @clerk/fastify: ^3.1.82 => 3.1.82 
    @types/node: ^26.6.3 => 26.6.3 
    fastify: ^5.12.5 => 5.12.5 
    typescript: ^7.0.2 => 7.0.2
Dominant language
TypeScript
Stars
1.8k
Forks
479
Avg merge
1d 18h
Merged PRs (30d)
313

Getting set up

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from clerk/javascript

All issues in clerk/javascript

Similar issues

More TypeScript issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.