body-fingerprint

Install

1npm install body-fingerprint

Usage

1const express = require("express");
2const app = express();
3
4const { bodyFingerprint, jsonFingerprint } = require("body-fingerprint");
5
6app.use(bodyFingerprint);
7app.use(jsonFingerprint);
8
9app.get("/", (_, res) =>
10  res.send(`
11<script>
12body = new FormData();
13body.set('a', 'b');
14body.set('c', 'd');
15body.set('e', new File([], ''))
16fetch('/', {
17    method: 'post', 
18    body})
19    .then((res) => res.text())
20    .then((res) => document.body.insertAdjacentHTML(
21        'beforebegin',
22        '<span style="white-space: pre-line">' + res + '</span>'
23    ));
24fetch('/', {
25    method: 'post', 
26    headers: {'content-type': 'application/json'},
27    body: JSON.stringify({
28        a: 'b',
29        c: 'd', 
30        e: {
31            f: 'g'
32        }
33    })
34})
35    .then((res) => res.text())
36    .then((res) => document.body.insertAdjacentHTML(
37        'beforebegin',
38        '<span style="white-space: pre-line">' + res + '</span>'
39    ))    
40</script>
41`)
42);
43
44app.post("/", (req, res) => {
45  res.send([req.multipart.fingerprint, req.json.fingerprint]);
46});
47
48app.listen(3000);

Multipart Fingerprint

Request:

POST /multipart HTTP/1.1
Host: example.com
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary1234567890123456

------WebKitFormBoundary1234567890123456
Content-Disposition: form-data; name="a"

b
------WebKitFormBoundary1234567890123456
Content-Disposition: form-data; name="c"

d
------WebKitFormBoundary1234567890123456
Content-Disposition: form-data; name="e"; filename=""
Content-Type: application/octet-stream


------WebKitFormBoundary1234567890123456--

Generated req.multipart object:

1{
2  "parts": [
3    {
4      "attributes": {
5        "order": ["name"]
6      },
7      "headers": {
8        "order": ["Content-Disposition"]
9      }
10    },
11    {
12      "attributes": {
13        "order": ["name"]
14      },
15      "headers": {
16        "order": ["Content-Disposition"]
17      }
18    },
19    {
20      "attributes": {
21        "order": ["name", "filename"]
22      },
23      "headers": {
24        "order": ["Content-Disposition", "Content-Type"]
25      }
26    }
27  ]
28}

JSON Fingerprint

Request:

1POST /json HTTP/1.1
2Host: example.com
3Content-Type: application/json
4
5{
6  a: 1,
7  b: {
8    c: 2,
9    d: 3,
10  }
11}

Generated req.json object:

1{
2  "fingerprint": "a,b,c,d",
3  "order": ["a", "b", "c", "d"],
4  "spaces": [" ", "\r", " \r", ... "\r"] // spaces fingerprint of json structure
5}

Options

depthFirstOrder - traverses keys using depth-first search

1{
2  a: 1,
3  b: {
4    c: 2,
5    d: 3,
6  }
7}

produces a,c,d,b if depthFirstOrder is true. false by default

Entropy

A property value representing Shannon entropy. null by default

• For multipart access through req.multipart.entropy

• For JSON access through req.json.entropy

Test

1npm test