valid github signature check

README.md

@@ -63,14 +63,14 @@ Create a webhook on your git source (On GitHub, in the `Settings/Webhooks` part
 Here are the steps for Github, if you use another platform adapt it your way (header format on the config) :
 
 * Create a password or random secret
-* Calculate it's SHA1
 * Edit your configuration to add webhook info 
 ```json
 {
 ...
 "webhook": {
-    "secret_value": "sha1=<value>",
-    "secret_header": "X-Hub-Signature"
+    "endpoint": "/webhook",
+    "secret": "sha1=<value>",
+    "signature_header": "X-Hub-Signature"
   },
 ...
 }

package-lock.json

@@ -2704,6 +2704,11 @@
         "which": "^1.2.9"
       }
     },
+    "crypto": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/crypto/-/crypto-1.0.1.tgz",
+      "integrity": "sha512-VxBKmeNcqQdiUQUW2Tzq0t377b54N2bMtXO/qiLa+6eRRmmC4qT3D4OnTGoT/U6O9aklQ/jTwbOtRMTTY8G0Ig=="
+    },
     "cssom": {
       "version": "0.3.6",
       "resolved": "https://registry.npmjs.org/cssom/-/cssom-0.3.6.tgz",

package.json

@@ -5,6 +5,8 @@
   "description": "A static blog using Markdown pulled from your git repository.",
   "main": "src/server.js",
   "dependencies": {
+    "body-parser": "^1.19.0",
+    "crypto": "^1.0.1",
     "ejs": "^2.6.2",
     "express": "^4.17.1",
     "ncp": "^2.0.0",

src/app.js

@@ -3,6 +3,9 @@ const app = express();
 const fs = require('fs');
 const path = require('path');
 const Rss = require('rss');
+const bodyParser = require('body-parser');
+const crypto = require('crypto');
+app.use(bodyParser.json());
 
 /**
  * Terminal colors and symbols to display status messages
@@ -127,12 +130,20 @@ module.exports = (config) => {
   //webhook endpoint
   app.post(config['webhook']['endpoint'], (req, res) => {
     if (config['modules']['webhook']) {
-      if (config['webhook']['secret_header'] && req.get(config['webhook']['secret_header']) !== config['webhook']['secret_value']) {
-        res.sendStatus(403);
-      } else {
-        res.sendStatus(200);
-        //TODO reload
+      if (config['webhook']['signature_header'] && config['webhook']['secret']) {
+        const payload = JSON.stringify(req.body);
+        if (!payload) {
+          return res.sendStatus(403);
+        }
+        const hmac = crypto.createHmac('sha1', config['webhook']['secret']);
+        const digest = 'sha1=' + hmac.update(payload).digest('hex');
+        const checksum = req.headers[config['webhook']['signature_header']];
+        if (!checksum || !digest || checksum !== digest) {
+          return res.sendStatus(403);
+        }
       }
+      res.sendStatus(200);
+      //TODO reload
     } else {
       res.sendStatus(400);
     }

src/config.default.json

@@ -30,8 +30,8 @@
   },
   "webhook": {
     "endpoint": "/webhook",
-    "secret_value": "",
-    "secret_header": ""
+    "secret": "",
+    "signature_header": ""
   },
   "showdown": {
     "parseImgDimensions": true,

test/app.test.js

@@ -151,18 +151,29 @@ describe('Test webhook', () => {
       done();
     });
   });
+  test('403 no payload', (done) => {
+    config['webhook']['signature_header'] = 'testheader';
+    config['webhook']['secret'] = 'testvalue';
+    request(app).post('/webhooktest').then((response) => {
+      expect(response.statusCode).toBe(403);
+      done();
+    });
+  });
   test('403 wrong secret', (done) => {
-    config['webhook']['secret_header'] = 'testheader';
-    config['webhook']['secret_value'] = 'testvalue';
-    request(app).post('/webhooktest').set('testheader','testvalue2').then((response) => {
+    config['webhook']['signature_header'] = 'testheader';
+    config['webhook']['secret'] = 'testvalue';
+    request(app).post('/webhooktest').set('testheader', 'sha1=invalid').then((response) => {
       expect(response.statusCode).toBe(403);
       done();
     });
   });
   test('200 valid secret', (done) => {
-    config['webhook']['secret_header'] = 'testheader';
-    config['webhook']['secret_value'] = 'testvalue';
-    request(app).post('/webhooktest').set('testheader','testvalue').then((response) => {
+    config['webhook']['signature_header'] = 'testheader';
+    config['webhook']['secret'] = 'testvalue';
+    request(app).post('/webhooktest')
+      .send({})
+      .set('testheader', 'sha1=d924d5bd4b36faf9d572844ac9c12a09ce3e7134')
+      .then((response) => {
       expect(response.statusCode).toBe(200);
       //TODO test reload
       done();