├── .prettierrc ├── .gitignore ├── wrangler.toml ├── package.json ├── .github └── workflows │ └── semgrep.yml ├── LICENSE-MIT ├── README.md ├── index.js └── LICENSE-APACHE /.prettierrc: -------------------------------------------------------------------------------- 1 | { 2 | "singleQuote": true, 3 | "semi": false, 4 | "trailingComma": "all", 5 | "tabWidth": 2, 6 | "printWidth": 80 7 | } 8 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | /target 2 | /dist 3 | **/*.rs.bk 4 | Cargo.lock 5 | bin/ 6 | pkg/ 7 | wasm-pack.log 8 | worker/ 9 | node_modules/ 10 | .cargo-ok 11 | -------------------------------------------------------------------------------- /wrangler.toml: -------------------------------------------------------------------------------- 1 | name = "access-crl-worker" 2 | type = "webpack" 3 | 4 | workers_dev = false 5 | route = "" 6 | account_id = "" 7 | zone_id = "" 8 | kv-namespaces = [{ binding = "CRL_NAMESPACE", id = "" }] 9 | vars = { CRL_URL = "" } 10 | -------------------------------------------------------------------------------- /package.json: -------------------------------------------------------------------------------- 1 | { 2 | "private": true, 3 | "name": "access-crl-worker-template", 4 | "version": "1.0.0", 5 | "description": "A self contained worker that can be used for doing basic CRL checks. It assumes that the request has gone through Access MTLS.", 6 | "main": "index.js", 7 | "scripts": { 8 | "test": "echo \"Error: no test specified\" && exit 1", 9 | "format": "prettier --write '**/*.{js,css,json,md}'" 10 | }, 11 | "author": "James Royal ", 12 | "license": "MIT OR Apache-2.0", 13 | "devDependencies": { 14 | "prettier": "^1.18.2" 15 | }, 16 | "dependencies": { 17 | "pkijs": "^2.1.84" 18 | } 19 | } 20 | -------------------------------------------------------------------------------- /.github/workflows/semgrep.yml: -------------------------------------------------------------------------------- 1 | 2 | on: 3 | pull_request: {} 4 | workflow_dispatch: {} 5 | push: 6 | branches: 7 | - main 8 | - master 9 | schedule: 10 | - cron: '0 0 * * *' 11 | name: Semgrep config 12 | jobs: 13 | semgrep: 14 | name: semgrep/ci 15 | runs-on: ubuntu-20.04 16 | env: 17 | SEMGREP_APP_TOKEN: ${{ secrets.SEMGREP_APP_TOKEN }} 18 | SEMGREP_URL: https://cloudflare.semgrep.dev 19 | SEMGREP_APP_URL: https://cloudflare.semgrep.dev 20 | SEMGREP_VERSION_CHECK_URL: https://cloudflare.semgrep.dev/api/check-version 21 | container: 22 | image: returntocorp/semgrep 23 | steps: 24 | - uses: actions/checkout@v3 25 | - run: semgrep ci 26 | -------------------------------------------------------------------------------- /LICENSE-MIT: -------------------------------------------------------------------------------- 1 | MIT License 2 | 3 | Copyright (c) 2020 Cloudflare 4 | 5 | Permission is hereby granted, free of charge, to any person obtaining a copy 6 | of this software and associated documentation files (the "Software"), to deal 7 | in the Software without restriction, including without limitation the rights 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 9 | copies of the Software, and to permit persons to whom the Software is 10 | furnished to do so, subject to the following conditions: 11 | 12 | The above copyright notice and this permission notice shall be included in all 13 | copies or substantial portions of the Software. 14 | 15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 21 | SOFTWARE. 22 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Access CRL Worker Template 2 | 3 | This worker fetches a CRL from a given endpoint and uses it to check if a certificate used with [Cloudflare Access Mutual TLS](https://developers.cloudflare.com/access/service-auth/mtls/) is valid. 4 | 5 | ## Configuration 6 | 7 | There are a few setup steps needed to use this worker 8 | 9 | 1. Create or reuse a Cloudflare Workers KV namespace and put the ID in your `wrangler.toml` file on the `kv-namespaces` line. 10 | 1. If you are creating a new namespace, you can use wrangler to do it. 11 | ```shell 12 | $ wrangler kv:namespace create CRL_NAMESPACE 13 | ``` 14 | 1. Copy the output of the command into your `wrangler.toml` file and replace the stub. 15 | 16 | 1. Set the URL of your CRL 17 | 1. **If you are using wrangler version 1.8.0 or higher.** Set the `CRL_URL` variable in your `wrangler.toml` file to your CRL URL. 18 | 1. **If you are using a wrangler version older than 1.8.0** Uncomment and replace the CRL_URL variable in `index.js` with the location of your CRL. Remove the `vars` line in the `wrangler.toml` file. 19 | 20 | ## Deployment 21 | Make sure you have set the needed configuration and then run the following. 22 | ``` 23 | wrangler publish 24 | ``` 25 | 26 | #### Force refetch 27 | 28 | By default we rely on the next update field in the CRL to know when to refresh the CRL. However you can force a refresh of the CRL by adding a `force-crl-refresh: 1` header to the your request 29 | 30 | ## Caveats 31 | 32 | 1. Due to workers CPU time limits any CRL with more than 5000 serial numbers on it has a chance to hit the CPU time limit and fail. 33 | 1. This worker will only check the CRL if the request coming in had a certifcate successfully presented to the Cloudflare edge. -------------------------------------------------------------------------------- /index.js: -------------------------------------------------------------------------------- 1 | /** 2 | * This worker script will handle loading a CRL and doing a cert revocation check 3 | * 4 | * You can force a refresh of the CRL by adding a `force-crl-refresh: 1` header to the original request 5 | */ 6 | 7 | import * as asn1js from 'asn1js' 8 | import { CertificateRevocationList } from 'pkijs' 9 | 10 | // The URL where your CRL is located. We will fetch it from here. 11 | // Uncomment this line if you can't use wrangler >= 1.8.0 12 | // const CRL_URL = '' 13 | 14 | // The key we store your crl under in your namespace 15 | const CRL_KV_KEY = `CRL_${btoa(CRL_URL)}` 16 | 17 | // Optional header that will force the worker to get an updated CRL 18 | const FORCE_CRL_REFRESH_HEADER = 'force-crl-refresh' 19 | 20 | /** 21 | * Worker entry point 22 | */ 23 | addEventListener('fetch', event => { 24 | event.respondWith(handleRequest(event)) 25 | }) 26 | 27 | /** 28 | * Return a 403 response 29 | */ 30 | function forbidden() { 31 | return new Response('client certificate was revoked', { status: 403 }) 32 | } 33 | 34 | /** 35 | * Helper function that converts a buffer to a hex string 36 | * @param {*} inputBuffer 37 | */ 38 | function bufToHex(inputBuffer) { 39 | let result = '' 40 | for (const item of new Uint8Array(inputBuffer, 0, inputBuffer.byteLength)) { 41 | const str = item.toString(16).toUpperCase() 42 | if (str.length === 1) result += '0' 43 | result += str 44 | } 45 | return result.trim() 46 | } 47 | 48 | /** 49 | * Fetchs a CRL list, parses out the serial numbers, and stores them into workers kv 50 | */ 51 | async function updateCRL() { 52 | const crlResp = await fetch(CRL_URL) 53 | if (crlResp.status == 200) { 54 | const buf = await crlResp.arrayBuffer() 55 | const asn1 = asn1js.fromBER(buf) 56 | const crlSimpl = new CertificateRevocationList({ 57 | schema: asn1.result, 58 | }) 59 | const newCRL = { 60 | nextUpdate: crlSimpl.nextUpdate.value, 61 | thisUpdate: crlSimpl.thisUpdate.value, 62 | revokedSerialNumbers: crlSimpl.revokedCertificates.reduce( 63 | (revokedSerialNums, cert) => { 64 | let serialNum = bufToHex(cert.userCertificate.valueBlock.valueHex) 65 | revokedSerialNums[serialNum] = true 66 | return revokedSerialNums 67 | }, 68 | {}, 69 | ), 70 | } 71 | CRL_NAMESPACE.put(CRL_KV_KEY, JSON.stringify(newCRL)) 72 | return newCRL 73 | } 74 | throw new Error(`failed to fetch crl with status ${crlResp.status}`) 75 | } 76 | 77 | /** 78 | * Load a CRL from workers kv. Handles refreshing the crl as needed. 79 | */ 80 | async function loadCRL(event, forceCRLRefresh = false) { 81 | // Force a refresh of the CRL list if needed 82 | if (forceCRLRefresh) { 83 | return await updateCRL() 84 | } 85 | 86 | // attempt to get the CRL from workers kv first 87 | let crl = await CRL_NAMESPACE.get(CRL_KV_KEY, 'json') 88 | if (!crl) { 89 | // the CRL wasn't in workers kv, so go fetch it from the source 90 | crl = await updateCRL() 91 | } 92 | 93 | // Check to see if we should refresh the CRL 94 | const nextUpdate = Date.parse(crl.next_update) 95 | const now = new Date() 96 | if (now > nextUpdate) { 97 | // it is time to update the CRL. Out of band send a request to update the workers kv key 98 | event.waitUntil(updateCRL()) 99 | } 100 | 101 | return crl 102 | } 103 | 104 | async function handleRequest(event) { 105 | try { 106 | const request = event.request 107 | // Ensure the request has the Cloudflare cf object and certificate headers and that the certificate was successfully presented 108 | // If so, then check the CRL to see if the cert was revoked. 109 | if ( 110 | request.cf && 111 | request.cf.tlsClientAuth && 112 | request.cf.tlsClientAuth.certPresented && 113 | request.cf.tlsClientAuth.certVerified === 'SUCCESS' 114 | ) { 115 | // Check to see if we were asked to force a CRL refresh 116 | const forceCRLRefresh = request.headers.get(FORCE_CRL_REFRESH_HEADER) 117 | ? true 118 | : false 119 | 120 | // Load the crl 121 | const crl = await loadCRL(event, forceCRLRefresh) 122 | if (!crl) { 123 | return new Response('failed to load CRL', { status: 500 }) 124 | } 125 | 126 | // Check to see if the certificate the user presented is in the crl 127 | if (crl.revokedSerialNumbers[request.cf.tlsClientAuth.certSerial]) { 128 | return forbidden() 129 | } 130 | } 131 | return await fetch(request) 132 | } catch (e) { 133 | return new Response(`failed to load CRL ${e}`, { status: 500 }) 134 | } 135 | } 136 | -------------------------------------------------------------------------------- /LICENSE-APACHE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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