Hennge Test.md

hennge.go

package main

import (
	"bufio"
	"fmt"
	"os"
)

var in = bufio.NewReader(os.Stdin)

func power4(x int64) int64 {
	return x * x * x * x
}

func recursiveReadAndSumPower4Numbers(x int, sum *int64) {
	if x == 0 {
		return
	}

	var y int64
	fmt.Fscan(in, &y)

	if y <= 0 {
		*sum += power4(y)
	}

	recursiveReadAndSumPower4Numbers(x-1, sum)
}

func recursiveProcessTests(t int) {
	if t == 0 {
		return
	}

	var x int
	fmt.Fscan(in, &x)

	var sum int64 = 0
	recursiveReadAndSumPower4Numbers(x, &sum)

	fmt.Println(sum)

	recursiveProcessTests(t - 1)
}

func main() {
	var t int
	fmt.Fscan(in, &t)

	recursiveProcessTests(t)
}

totp_rfc_6238.js

import crypto from "crypto";

function totpHex(secretHex, counter, algo, digits = 8) {
    const msg = Buffer.alloc(8);
    msg.writeBigUInt64BE(BigInt(counter));

    const hmac = crypto
        .createHmac(algo, Buffer.from(secretHex, "hex"))
        .update(msg)
        .digest();

    const offset = hmac[hmac.length - 1] & 0x0f;

    const code =
        ((hmac[offset] & 0x7f) << 24) |
        ((hmac[offset + 1] & 0xff) << 16) |
        ((hmac[offset + 2] & 0xff) << 8) |
        (hmac[offset + 3] & 0xff);

    return (code % 10 ** digits).toString().padStart(digits, "0");
}

// test part

const seed =
    "3132333435363738393031323334353637383930";

const seed32 =
    seed + "313233343536373839303132";

const seed64 =
    seed +
    "3132333435363738393031323334353637383930" +
    "3132333435363738393031323334353637383930" +
    "31323334";

const times = [
    59,
    1111111109,
    1111111111,
    1234567890,
    2000000000,
    20000000000
];

const X = 30;

for (const t of times) {
    const counter = Math.floor(t / X);
    const hexT = counter.toString(16).toUpperCase().padStart(16, "0");

    console.log("Time:", t);
    console.log("T(hex):", hexT);
    console.log("SHA1  :", totpHex(seed, counter, "sha1"));
    console.log("SHA256:", totpHex(seed32, counter, "sha256"));
    console.log("SHA512:", totpHex(seed64, counter, "sha512"));
    console.log("----");
}

EMAIL=""
GITHUB_PATH=""
OTP=""
curl -X POST \
  https://api.challenge.hennge.com/challenges/backend-recursion/004 \
  -H "Content-Type: application/json" \
  -H "Authorization: Basic $(printf '%s:%s' "$EMAIL" "$OTP" | base64)" \
  -d "{
    \"github_url\": \"https://gist.github.com/$GITHUB_PATH\",
    \"contact_email\": \"$EMAIL\",
    \"solution_language\": \"golang\"
  }"

Quick way to double verify otpauth implementation.

import * as OTPAuth from "otpauth";


function generateHenngeTOTP(email) {
  const secretString = email + "HENNGECHALLENGE004";

  const totp = new OTPAuth.TOTP({
    issuer: "HENNGE",
    label: email,
    algorithm: "SHA512",
    digits: 10,
    period: 30,
    secret: OTPAuth.Secret.fromUTF8(secretString),
  });

  return totp.generate();
}

const email = "[email protected]";
const otp = generateHenngeTOTP(email);

console.log("TOTP:", otp);