From 13c4a755e66cbff0ac0c65eece015bddbe152ed2 Mon Sep 17 00:00:00 2001
From: Runxi Yu <me@runxiyu.org>
Date: Mon, 24 Mar 2025 01:30:53 +0800
Subject: Use a WebAssembly solver
---
challenge.tmpl | 286 ---------------------------------------------------------
1 file changed, 286 deletions(-)
delete mode 100644 challenge.tmpl
(limited to 'challenge.tmpl')
diff --git a/challenge.tmpl b/challenge.tmpl
deleted file mode 100644
index 13eac3d..0000000
--- a/challenge.tmpl
+++ /dev/null
@@ -1,286 +0,0 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
- <meta charset="utf-8" />
- <meta name="viewport" content="width=device-width, initial-scale=1" />
- <title>Proof-of-work challenge</title>
- <style>
- html {
- font-family: sans-serif;
- background-color: var(--background-color);
- color: var(--text-color);
- --radius-1: 0.32rem;
- --background-color: hsl(0, 0%, 100%);
- --text-color: hsl(0, 0%, 0%);
- --link-color: hsl(320, 50%, 36%);
- --light-text-color: hsl(0, 0%, 45%);
- --darker-border-color: hsl(0, 0%, 72%);
- --lighter-border-color: hsl(0, 0%, 85%);
- --text-decoration-color: hsl(0, 0%, 72%);
- --darker-box-background-color: hsl(0, 0%, 92%);
- --lighter-box-background-color: hsl(0, 0%, 95%);
- --primary-color: hsl(320, 50%, 36%);
- --primary-color-contrast: hsl(320, 0%, 100%);
- --danger-color: #ff0000;
- --danger-color-contrast: #ffffff;
- }
-
- @media (prefers-color-scheme: dark) {
- html {
- --background-color: hsl(0, 0%, 0%);
- --text-color: hsl(0, 0%, 100%);
- --link-color: hsl(320, 50%, 76%);
- --light-text-color: hsl(0, 0%, 78%);
- --darker-border-color: hsl(0, 0%, 35%);
- --lighter-border-color: hsl(0, 0%, 25%);
- --text-decoration-color: hsl(0, 0%, 30%);
- --darker-box-background-color: hsl(0, 0%, 20%);
- --lighter-box-background-color: hsl(0, 0%, 15%);
- }
- }
-
- body {
- margin: 0;
- padding: 1rem;
- }
-
- main {
- max-width: 720px;
- margin: 0 auto;
- }
-
- *:focus-visible {
- outline: 1.5px var(--primary-color) solid;
- }
-
- section {
- margin: 0;
- }
-
- label {
- display: block;
- font-style: italic;
- margin-top: 1rem;
- margin-bottom: 0.5rem;
- }
-
- h1 {
- margin-top: 0;
- }
-
- p, summary {
- line-height: 1.2;
- font-size: 1rem;
- }
-
- a {
- color: var(--link-color);
- text-decoration-color: var(--text-decoration-color);
- }
-
- input[type="text"] {
- font-family: monospace;
- font-size: 1rem;
- background-color: var(--lighter-box-background-color);
- color: var(--text-color);
- width: 100%;
- padding: 0.5rem;
- border-radius: var(--radius-1);
- border: none;
- box-shadow: inset 0 1px 4px rgba(0, 0, 0, 0.15);
- margin-bottom: 1rem;
- box-sizing: border-box;
- }
-
- input[type="submit"] {
- padding: 0.5rem 1rem;
- background-color: var(--primary-color);
- color: var(--primary-color-contrast);
- border: none;
- border-radius: var(--radius-1);
- cursor: pointer;
- }
-
- input[readonly] {
- background-color: var(--lighter-box-background-color);
- color: var(--text-color);
- cursor: text;
- }
-
- details {
- margin-top: 2rem;
- background-color: var(--lighter-box-background-color);
- padding: 0.5rem;
- border-radius: var(--radius-1);
- box-shadow: inset 0 1px 4px rgba(0, 0, 0, 0.15);
- }
-
- pre {
- overflow-x: auto;
- display: block;
- white-space: pre-wrap;
- word-break: break-word;
- }
-
- #solver_status {
- color: var(--light-text-color);
- margin-top: 1rem;
- }
- </style>
- <script>
- /*
- @licstart The following is the entire license notice for the
- JavaScript code in this page.
-
- Copyright (C) 2025 Runxi Yu
-
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions are
- met:
-
- 1. Redistributions of source code must retain the above copyright
- notice, this list of conditions and the following disclaimer.
-
- 2. Redistributions in binary form must reproduce the above copyright
- notice, this list of conditions and the following disclaimer in the
- documentation and/or other materials provided with the distribution.
-
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS "AS IS" AND ANY
- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
- CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
- NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
- SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
- @licend The above is the entire license notice
- for the JavaScript code in this page.
- */
- </script>
-</head>
-<body>
- <main>
- <header>
- <h1>Proof-of-work challenge</h1>
- </header>
-
- <section>
- <p>This site is protected by <a href="{{ .Global.SourceURL }}">Powxy</a>{{ if .Global.Version }} {{ .Global.Version }}{{ end }}.</p>
- <p>You must complete this proof-of-work challenge before you can access this site.</p>
- </section>
-
- <section>
- <p>Select a nonce no longer than 32 bytes, such that when it is appended to the decoded form of the challenge identifier, and the entire result is hashed with SHA-256, the first {{ .Global.NeedBits }} bits of the SHA-256 hash are all zeros. Within one octet, higher bits are considered to come before lower bits.</p>
- <p>In other words, find an nonce <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mi>N</mi><annotation encoding="application/x-tex">N</annotation></semantics></math> with <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mo stretchy="false" form="prefix">|</mo><mi>N</mi><mo stretchy="false" form="postfix">|</mo><mo>≤</mo><mn>32</mn><mspace width="0.167em"></mspace><mi mathvariant="normal">B</mi></mrow><annotation encoding="application/x-tex">\lvert N\rvert \le 32\,\mathrm{B}</annotation></semantics></math>, such that <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mrow><mi mathvariant="normal">S</mi><mi mathvariant="normal">H</mi><mi mathvariant="normal">A</mi><mn mathvariant="normal">256</mn></mrow><mrow><mo stretchy="true" form="prefix">(</mo><mi>I</mi><mspace width="0.167em"></mspace><mo stretchy="false" form="postfix">∥</mo><mspace width="0.167em"></mspace><mi>N</mi><mo stretchy="true" form="postfix">)</mo></mrow><mo><</mo><msup><mn>2</mn><mn>{{ .Global.NeedBitsReverse }}</mn></msup></mrow><annotation encoding="application/x-tex">\mathrm{SHA256}(I \,\|\, N) < 2^{{{ .Global.NeedBitsReverse }}}</annotation></semantics></math> in big endian, where <math display="inline" xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mi>I</mi><annotation encoding="application/x-tex">I</annotation></semantics></math> is the identifier provided below.</p>
- <label for="unsigned-identifier">Challenge identifier (read-only)</label>
- <input id="unsigned-identifier" type="text" readonly disabled tabindex="-1" value="{{ .Identifier }}" />
- </section>
-
- <section>
- <form method="POST">
- <p>Encode your selected nonce in base64 and submit it below.</p>
- <p>Please note that if your submission is successful, you will be given a cookie that will allow you to access this site for a period of time without having to complete the challenge again. By pressing the submit button, you agree to be given cookies for this purpose.</p>
- <label for="nonce">Nonce</label>
- <input id="nonce" name="powxy" type="text" />
- <input type="submit" value="Submit" />
- </form>
- </section>
-
- {{- if .Message }}
- <section>
- <p><strong>{{ .Message }}</strong></p>
- </section>
- {{- end }}
-
- <section>
- <p id="solver_status">JavaScript seems to be disabled. You must solve the challenge externally.</p>
- </section>
-
- <details>
- <summary>Offline solver program</summary>
- <pre>` + html.EscapeString(solverProgram) + `</pre>
- </details>
- </main>
-
- <script>
- document.addEventListener("DOMContentLoaded", function() {
- let challenge_b64 = "{{ .Identifier }}";
- let difficulty = {{ .Global.NeedBits }};
- let form = document.querySelector("form");
- let field = form.querySelector("input[name='powxy']");
- let status_el = document.getElementById("solver_status");
-
- if (!window.crypto || !window.crypto.subtle) {
- status_el.textContent = "SubtleCrypto not available. You must solve the challenge externally.";
- return;
- }
- status_el.textContent = "SubtleCrypto detected. Attempting to solve the challenge automatically...";
-
- let solver_active = true;
- form.addEventListener("submit", function() {
- solver_active = false;
- });
-
- async function solve_pow() {
- let identifier_bytes = Uint8Array.from(
- atob(challenge_b64),
- ch => ch.charCodeAt(0)
- );
-
- let nonce = 0n;
- let buf = new ArrayBuffer(8);
- let view = new DataView(buf);
-
- while (solver_active) {
- view.setBigUint64(0, nonce, true);
-
- let candidate = new Uint8Array(identifier_bytes.length + 8);
- candidate.set(identifier_bytes, 0);
- candidate.set(new Uint8Array(buf), identifier_bytes.length);
-
- let digest_buffer = await crypto.subtle.digest("SHA-256", candidate);
- let digest = new Uint8Array(digest_buffer);
-
- if (has_leading_zero_bits(digest, difficulty)) {
- let nonce_str = String.fromCharCode(...new Uint8Array(buf));
- field.value = btoa(nonce_str);
-
- status_el.textContent = "A solution has been found automatically in " + nonce + " iterations.";
- return;
- }
-
- nonce++;
-
- if ((nonce & 0x00FFn) === 0n) {
- status_el.textContent = "Attempting to solve automatically. Tried " + nonce + " candidates so far...";
- await new Promise(r => setTimeout(r, 0));
- }
- }
- }
-
- function has_leading_zero_bits(digest, bits) {
- let full_bytes = bits >>> 3;
- for (let i = 0; i < full_bytes; i++) {
- if (digest[i] !== 0) {
- return false;
- }
- }
- let remainder = bits & 7;
- if (remainder !== 0) {
- let mask = 0xFF << (8 - remainder);
- if ((digest[full_bytes] & mask) !== 0) {
- return false;
- }
- }
- return true;
- }
-
- solve_pow();
- });
- </script>
-</body>
-</html>
--
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