Initial commit

Once again a weird place to commit, I have already done a lot of work, but I am just bad at using git, okay.

packages/lib/.gitignore

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+dist
+node_modules

packages/lib/README.md

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+# @impost/lib
+
+This package contains the types and WASM code for the impost. It is useful for
+building other packages that want to use the WASM code, a client, or a server.
+
+## Usage
+
+```ts
+import {
+  validate_challenge,
+  generate_target_number_challenge,
+} from "@impost/lib/validator";
+import {
+  init_solver,
+  get_wasm_module,
+  solve_target_number_challenge,
+} from "@impost/lib/solver";
+import { type Challenge, ChallengeStrategy } from "@impost/lib";
+
+const challenge = await generate_target_number_challenge(
+  // timeout in ms
+  {
+    // impost automatically recognizes this parameter, its also recommended to
+    // add a timestamp to prevent replay or pre-computation attacks
+    expires_at: Date.now() + 3600,
+  }
+  // max number
+  1_000
+);
+
+if (challenge === null) {
+  throw new Error("Failed to generate challenge");
+}
+
+let solver = await init_solver(
+  {
+    __get_solution: () => Atomics.load(atomic_solution!, 0),
+    __set_solution: (value: number) =>
+      Atomics.store(atomic_solution!, 0, value),
+    __cmpxchg_solution: (expected: number, replacement: number) =>
+      Atomics.compareExchange(atomic_solution!, 0, expected, replacement),
+    __fetch_add_nonce: (value: number) => Atomics.add(atomic_nonce!, 0, value),
+  },
+  await get_wasm_module()
+);
+
+const solution = await solve_target_number_challenge(solver, {
+  salt: challenge.salt,
+  target: challenge.target,
+});
+
+const is_valid = await validate_challenge(challenge, {
+  challenge: challenge.target,
+  nonce: solution,
+});
+
+if (is_valid) {
+  console.log("Challenge solved!", solution);
+}
+```

packages/lib/package.json

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+{
+    "name": "@impost/lib",
+    "version": "0.1.0",
+    "type": "module",
+    "license": "BSL-1.0",
+    "exports": {
+        ".": {
+            "types": "./dist/index.d.ts",
+            "import": "./dist/index.js"
+        },
+        "./solver": {
+            "types": "./dist/solver.d.ts",
+            "import": "./dist/solver.js"
+        },
+        "./validator": {
+            "types": "./dist/validator.d.ts",
+            "import": "./dist/validator.js"
+        }
+    },
+    "files": [
+        "dist"
+    ],
+    "scripts": {
+        "build": "tsc && vite build",
+        "watch": "tsc && vite build --watch",
+        "dev": "vite",
+        "test": "echo \"Error: no test specified\" && exit 1"
+    },
+    "devDependencies": {
+        "oxc-minify": "^0.97.0",
+        "tslib": "^2.6.2",
+        "typescript": "^5.3.3",
+        "vite": "npm:rolldown-vite@latest",
+        "vite-plugin-dts": "^4.5.4"
+    },
+    "dependencies": {
+        "uuidv7": "^1.0.2"
+    }
+}

packages/lib/src/index.ts

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+export enum ChallengeAlgorithm {
+    Argon2id = "argon2id",
+}
+
+export enum ChallengeStrategy {
+    LeadingZeroes = "leading_zeroes",
+    TargetNumber = "target_number",
+}
+
+// In this case, the client will repeatedly hash a number with has until it 
+// finds a hash thaat starts with *difficulty* leading zeroes
+export interface ChallengeLeadingZeroes {
+    algorithm: ChallengeAlgorithm;
+    strategy: ChallengeStrategy.LeadingZeroes;
+    salt: string; // random string
+    difficulty: number;
+}
+
+// In this case, the server generates a random number, and the client will hash
+// the salt (a random string) + a random number until it finds a hash that is equal to challenge
+export interface ChallengeTargetNumber {
+    algorithm: ChallengeAlgorithm;
+    strategy: ChallengeStrategy.TargetNumber;
+    salt: string; // random string
+    target: string; // hash of salt + random number
+}
+
+export type Challenge = ChallengeLeadingZeroes | ChallengeTargetNumber;

packages/lib/src/solver.ts

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+import WASMSolverUrl from '../../../solver/zig-out/bin/solver.wasm?url&inline';
+
+type WasmExports = Record<string, Function> & {
+    "malloc": (byte_count: number) => number | null;
+    "free": (ptr: number | null, byte_count: number) => void;
+    "solve_leaading_zeroes_challenge": (challenge_ptr: number, challenge_len: number, difficulty: number) => number;
+    "solve_target_number_challenge": (challenge_ptr: number, challenge_len: number, target_ptr: number, target_len: number) => number;
+    "memory": WebAssembly.Memory;
+}
+
+export interface SolverModule extends WebAssembly.Instance {
+    exports: WasmExports;
+}
+
+export type SolverEnv = {
+    __get_solution: () => number;
+    __set_solution: (value: number) => void;
+    __cmpxchg_solution: (expected: number, replacement: number) => number;
+    __fetch_add_nonce: (value: number) => number;
+};
+
+export async function get_wasm_module(): Promise<WebAssembly.Module> {
+    return WebAssembly.compileStreaming(fetch(WASMSolverUrl));;
+}
+
+export async function init_solver(env: SolverEnv, module: WebAssembly.Module): Promise<SolverModule> {
+    return await WebAssembly.instantiate(module, {
+        env,
+    }) as unknown as SolverModule;
+}
+
+export function solve_leaading_zeroes_challenge(solver: SolverModule, challenge: { salt: string, difficulty: number }): number {
+    const { salt, difficulty } = challenge;
+    const encoder = new TextEncoder();
+
+    const salt_bytes = encoder.encode(salt);
+
+    const salt_ptr = solver.exports.malloc(salt_bytes.length);
+    if (salt_ptr === 0 || salt_ptr === null) {
+        throw new Error("Failed to allocate memory for challenge string");
+    }
+
+    const memory = new Uint8Array(solver.exports.memory.buffer);
+    memory.set(salt_bytes, salt_ptr);
+
+    const ret = solver.exports.solve_leaading_zeroes_challenge(
+        salt_ptr,
+        salt_bytes.length,
+        difficulty,
+    );
+
+    if (ret < 0) {
+        throw new Error("Failed to solve challenge");
+    }
+
+    return ret;
+}
+
+export function solve_target_number_challenge(solver: SolverModule, challenge: { salt: string, target: string }): number {
+    const { salt, target } = challenge;
+    const encoder = new TextEncoder();
+
+    const salt_bytes = encoder.encode(salt);
+    const target_bytes = encoder.encode(target);
+
+    const salt_ptr = solver.exports.malloc(salt_bytes.length);
+    if (salt_ptr === 0 || salt_ptr === null) {
+        throw new Error("Failed to allocate memory for salt string");
+    }
+
+    const target_ptr = solver.exports.malloc(target_bytes.length);
+    if (target_ptr === 0 || target_ptr === null) {
+        throw new Error("Failed to allocate memory for target string");
+    }
+
+    const memory = new Uint8Array(solver.exports.memory.buffer);
+    memory.set(salt_bytes, salt_ptr);
+    memory.set(target_bytes, target_ptr);
+
+    const ret = solver.exports.solve_target_number_challenge(
+        target_ptr,
+        target_bytes.length,
+        salt_ptr,
+        salt_bytes.length,
+    );
+
+    if (ret < 0) {
+        throw new Error("Failed to solve challenge");
+    }
+
+    return ret;
+}

packages/lib/src/validator.ts

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+import { ChallengeAlgorithm, ChallengeStrategy, type Challenge } from '.';
+import WASMValidatorUrl from '../../../solver/zig-out/bin/validator.wasm?url&inline';
+
+type WasmExports = Record<string, Function> & {
+    "malloc": (byte_count: number) => number | null;
+    "free": (ptr: number | null, byte_count: number) => void;
+    "validate_leading_zeroes_challenge": (challenge_ptr: number, challenge_len: number, nonce_ptr: number, nonce_len: number, difficulty: number) => number;
+    "validate_target_number_challenge": (target_ptr: number, target_len: number, nonce_ptr: number, nonce_len: number, salt_ptr: number, salt_len: number) => number;
+    "hash": (challenge_ptr: number, challenge_len: number, nonce_ptr: number, nonce_len: number) => bigint;
+    "memory": WebAssembly.Memory;
+}
+
+export interface ValidatorModule extends WebAssembly.Instance {
+    exports: WasmExports;
+}
+
+function array_to_base64(buffer: ArrayBuffer): string {
+    return btoa(String.fromCharCode(...new Uint8Array(buffer)));
+}
+
+async function generate_leading_zeroes_challenge(parameters: Object, difficulty: number): Promise<Challenge> {
+    let parameters_str = Object.entries(parameters).map(([key, value]) => `${key}=${value}`).join("&");
+    let salt = `${array_to_base64(crypto.getRandomValues(new Uint8Array(32)).buffer)}?${parameters_str}`;
+
+    let challenge: Challenge = {
+        algorithm: ChallengeAlgorithm.Argon2id,
+        strategy: ChallengeStrategy.LeadingZeroes,
+        salt,
+        difficulty,
+    };
+
+    return challenge;
+}
+
+async function generate_target_number_challenge(parameters: Object, max_number: number): Promise<Challenge | null> {
+    // in target number config, since we need to generate a target hash, we
+    // need to hash the salt + nonce, so the client knows what the target is
+    const validator = (await WebAssembly.instantiateStreaming(fetch(WASMValidatorUrl))).instance as unknown as ValidatorModule;
+
+    let parameters_str = Object.entries(parameters).map(([key, value]) => `${key}=${value}`).join("&");
+    let salt = `${array_to_base64(crypto.getRandomValues(new Uint8Array(32)).buffer)}?${parameters_str}`;
+    let random_number = new DataView(crypto.getRandomValues(new Uint8Array(4)).buffer).getUint32(0, true) % max_number;
+
+    const encoder = new TextEncoder();
+    const salt_bytes = encoder.encode(salt);
+    const random_number_bytes = encoder.encode(random_number.toString());
+
+    const salt_ptr = validator.exports.malloc(salt_bytes.length);
+    const random_number_ptr = validator.exports.malloc(random_number_bytes.length);
+
+    if (salt_ptr === 0 || salt_ptr === null || random_number_ptr === 0 || random_number_ptr === null) {
+        console.error("Failed to allocate memory for challenge string");
+        return null;
+    }
+
+    const memory = new Uint8Array(validator.exports.memory.buffer);
+    memory.set(salt_bytes, salt_ptr);
+    memory.set(random_number_bytes, random_number_ptr);
+
+    let target_blob: bigint = validator.exports.hash(salt_ptr, salt_bytes.length, random_number_ptr, random_number_bytes.length);
+    let target_ptr = Number(target_blob & BigInt(0xFFFFFFFF));
+    let target_len = Number(target_blob >> BigInt(32));
+
+    validator.exports.free(salt_ptr, salt_bytes.length);
+    validator.exports.free(random_number_ptr, random_number_bytes.length);
+
+    // do NOT use `memory` here, by this time it has almost definitely been resized and will cause errors to touch
+    let target_slice = new Uint8Array(validator.exports.memory.buffer.slice(target_ptr, target_ptr + target_len));
+    const target = new TextDecoder().decode(target_slice);
+
+    let challenge: Challenge = {
+        algorithm: ChallengeAlgorithm.Argon2id,
+        strategy: ChallengeStrategy.TargetNumber,
+        salt,
+        target
+    };
+
+    return challenge;
+}
+
+export interface LeadingZeroesChallengeConfig {
+    parameters: Object;
+    strategy: ChallengeStrategy.LeadingZeroes;
+    difficulty: number;
+}
+
+export interface TargetNumberChallengeConfig {
+    parameters: Object;
+    strategy: ChallengeStrategy.TargetNumber;
+    max_number: number;
+}
+
+export type ChallengeConfig = LeadingZeroesChallengeConfig | TargetNumberChallengeConfig;
+
+export async function generate_challenge(config: ChallengeConfig): Promise<Challenge | null> {
+    let challenge: Challenge | null = null;
+    switch (config.strategy) {
+        case ChallengeStrategy.LeadingZeroes:
+            challenge = await generate_leading_zeroes_challenge(config.parameters, config.difficulty);
+            break;
+        case ChallengeStrategy.TargetNumber:
+            challenge = await generate_target_number_challenge(config.parameters, config.max_number);
+            break;
+    }
+
+    if (challenge === null) {
+        return null;
+    }
+
+    return challenge;
+}
+
+export async function validate_challenge(challenge: Challenge, challenge_solution: { challenge: string, nonce: string }): Promise<boolean> {
+    const validator = (await WebAssembly.instantiateStreaming(fetch(WASMValidatorUrl))).instance as unknown as ValidatorModule
+
+    const encoder = new TextEncoder();
+
+    let err;
+    let memory;
+    let nonce_bytes, nonce_ptr;
+    let target_bytes, target_ptr;
+    switch (challenge.strategy) {
+        case ChallengeStrategy.LeadingZeroes:
+            target_bytes = encoder.encode(challenge_solution.challenge);
+            nonce_bytes = encoder.encode(challenge_solution.nonce);
+
+            target_ptr = validator.exports.malloc(challenge_solution.challenge.length);
+            nonce_ptr = validator.exports.malloc(challenge_solution.nonce.length);
+
+            if (target_ptr === 0 || target_ptr === null || nonce_ptr === 0 || nonce_ptr === null) {
+                console.error("Failed to allocate memory for challenge string");
+                return false;
+            }
+
+            memory = new Uint8Array(validator.exports.memory.buffer);
+            memory.set(target_bytes, target_ptr);
+            memory.set(nonce_bytes, nonce_ptr);
+
+            err = validator.exports.validate_leading_zeroes_challenge(target_ptr, target_bytes.length, nonce_ptr, nonce_bytes.length, challenge.difficulty);
+
+            validator.exports.free(target_ptr, target_bytes.length);
+            validator.exports.free(nonce_ptr, nonce_bytes.length);
+            break;
+        case ChallengeStrategy.TargetNumber:
+            target_bytes = encoder.encode(challenge.target);
+            const salt_bytes = encoder.encode(challenge.salt);
+            nonce_bytes = encoder.encode(challenge_solution.nonce);
+
+            const salt_ptr = validator.exports.malloc(salt_bytes.length);
+            target_ptr = validator.exports.malloc(target_bytes.length);
+            nonce_ptr = validator.exports.malloc(nonce_bytes.length);
+
+            if (salt_ptr === 0 || salt_ptr === null || target_ptr === 0 || target_ptr === null || nonce_ptr === 0 || nonce_ptr === null) {
+                console.error("Failed to allocate memory for challenge string");
+                return false;
+            }
+
+            memory = new Uint8Array(validator.exports.memory.buffer);
+            memory.set(salt_bytes, salt_ptr);
+            memory.set(target_bytes, target_ptr);
+            memory.set(nonce_bytes, nonce_ptr);
+
+            err = validator.exports.validate_target_number_challenge(target_ptr, target_bytes.length, nonce_ptr, nonce_bytes.length, salt_ptr, salt_bytes.length);
+
+            validator.exports.free(salt_ptr, salt_bytes.length);
+            validator.exports.free(target_ptr, target_bytes.length);
+            validator.exports.free(nonce_ptr, nonce_bytes.length);
+            break;
+    }
+
+    return err === 0;
+}

packages/lib/src/vite-env.d.ts

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+/// <reference types="vite/client" />

packages/lib/tsconfig.json

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+{
+  "compilerOptions": {
+    "declaration": true,
+    "target": "ES2022",
+    "experimentalDecorators": true,
+    "useDefineForClassFields": false,
+    "module": "ESNext",
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "types": ["vite/client"],
+    "skipLibCheck": true,
+
+    /* Bundler mode */
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "verbatimModuleSyntax": true,
+    "moduleDetection": "force",
+    "noEmit": true,
+
+    /* Linting */
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noFallthroughCasesInSwitch": true,
+    "noUncheckedSideEffectImports": true
+  },
+  "include": ["src"]
+}

packages/lib/vite.config.ts

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+import { resolve } from 'path';
+import { defineConfig } from 'vite';
+import dts from 'vite-plugin-dts';
+
+export default defineConfig({
+    build: {
+        target: 'es2022',
+        rollupOptions: {
+            input: [
+                resolve(__dirname, 'src/index.ts'),
+                resolve(__dirname, 'src/solver.ts'),
+                resolve(__dirname, 'src/validator.ts'),
+            ],
+            preserveEntrySignatures: "strict",
+            output: {
+                dir: 'dist',
+                entryFileNames: '[name].js',
+                preserveModules: false
+            }
+        },
+        sourcemap: true
+    },
+    resolve: {
+        alias: {
+            '@': '/src'
+        }
+    },
+    plugins: [dts()]
+});

packages/widget/.gitignore

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+dist
+node_modules

packages/widget/index.html

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+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>vite-project</title>
+    <script type="module" src="/src/pow-captcha.ts"></script>
+  </head>
+  <body>
+    <pow-captcha />
+  </body>
+</html>

packages/widget/package.json

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+{
+    "name": "@impost/widget",
+    "version": "0.1.0",
+    "type": "module",
+    "license": "BSL-1.0",
+    "module": "./dist/impost.js",
+    "exports": {
+        ".": {
+            "import": "./dist/impost.js"
+        }
+    },
+    "files": [
+        "dist"
+    ],
+    "scripts": {
+        "build": "tsc && vite build",
+        "watch": "tsc && vite build --watch",
+        "dev": "vite",
+        "test": "echo \"Error: no test specified\" && exit 1"
+    },
+    "peerDependencies": {
+        "lit": "^3.1.2",
+        "lit-element": "^3.1.2"
+    },
+    "devDependencies": {
+        "@types/node": "^20.11.24",
+        "lit": "^3.1.2",
+        "lit-element": "^3.1.2",
+        "oxc-minify": "^0.97.0",
+        "tslib": "^2.6.2",
+        "typescript": "^5.3.3",
+        "vite": "npm:rolldown-vite@latest",
+        "vite-plugin-dts": "^4.5.4"
+    }
+}

packages/widget/src/entry.ts

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+export * from './pow-captcha';

packages/widget/src/pow-captcha.ts

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+import { LitElement, html, css, isServer, type PropertyValues } from 'lit';
+import { customElement, property, state } from 'lit/decorators.js';
+import { type ChallengeSolveRequest, type SolutionMessage, WorkerMessageType, type WorkerRequest, WorkerResponseType } from './types/worker';
+import { type Challenge, ChallengeStrategy } from '@impost/lib';
+import { get_wasm_module } from '@impost/lib/solver';
+
+import ChallengeWorker from './solver-worker?worker&inline';
+
+@customElement('pow-captcha')
+export class PowCaptcha extends LitElement {
+    static override styles = css`
+    :host {
+        display: block;
+        width: var(--impost-widget-width, 250px);
+    }
+    .impost-widget {
+        display: flex;
+        flex-direction: column;
+        border: 1px solid var(--impost-widget-border-color, #505050);
+        font-family: sans-serif;
+        background-color: var(--impost-widget-background-color, #070408);
+        border-radius: var(--impost-widget-border-radius, 8px);
+    }
+    .impost-main {
+        display: flex;
+        align-items: center;
+        gap: 0.375rem;
+        padding: 0.75rem;
+    }
+    .impost-main span {
+        height: min-content;
+    }
+    .impost-checkbox {
+        display: flex;
+        align-items: center;
+        justify-content: center;
+        width: 1.5rem;
+        height: 1.5rem;
+        color: var(--impost-widget-checkbox-color, #6e6e6eff);
+    }
+    .impost-checkbox input {
+        height: 80%;
+        width: 80%;
+        margin: 0;
+    }
+    .impost-footer {
+        display: flex;
+        padding: 0.25rem 0.75rem;
+        font-size: 0.75rem;
+        color: var(--impost-widget-footer-color, #a2a2a2);
+        justify-content: space-around;
+        align-items: end;
+    }
+    .impost-footer div {
+        height: min-content;
+    }
+    .impost-footer #provider-link {
+        margin-left: auto;
+    }
+    .impost-footer div a {
+        color: var(--impost-widget-footer-color, #a2a2a2);
+    }
+    .impost-footer div a:hover {
+        text-decoration: none;
+    }
+    .hidden {
+        display: none;
+    }
+  `;
+
+
+    // one of: "load", "focus", "submit", "off"
+    @property({ type: String })
+    auto: "onload" | "onfocus" | "onsubmit" | "off" = "off";
+
+    @property({ type: String })
+    challengeUrl: string = 'http://localhost:3000/api/pow';
+
+    @property({ type: String })
+    challengejson: string = '';
+
+    // needed to allow for multiple widgets on the same page if you wanted to
+    // do that for some reason
+    uid: string = Math.floor(Math.random() * 100000).toString();
+
+    @state()
+    private solution: string = '';
+
+    @state()
+    private errorMessage: string = '';
+
+    @state()
+    private challengeData: Challenge | null = null;
+
+    @state()
+    private solved: boolean = false;
+
+    @state()
+    private isSolving: boolean = false;
+
+    @state()
+    private disabled: boolean = true;
+
+    @state()
+    private hashRate: number = 0;
+
+    // stores the nonce and solution atomics
+    private sab: SharedArrayBuffer = new SharedArrayBuffer(8);
+
+    private solverWorkers: Worker[] | null = null;
+
+    private solveStartTime: number | null = null;
+    private hashRateInterval: number | null = null;
+
+    override connectedCallback() {
+        super.connectedCallback();
+        this.fetchChallenge();
+
+        this.initWorkers();
+
+        switch (this.auto) {
+            case 'onload':
+                this.solveChallenge();
+                break;
+            case 'onfocus':
+                this.addEventListener('focus', () => this.solveChallenge());
+                break;
+            case 'onsubmit':
+                if (this.parentElement?.nodeName === 'FORM') {
+                    this.parentElement.addEventListener('submit', () => this.solveChallenge());
+                }
+                break;
+        }
+    }
+
+    protected override firstUpdated(_changedProperties: PropertyValues): void {
+        super.firstUpdated(_changedProperties);
+
+        this.disabled = false;
+    }
+
+    override disconnectedCallback() {
+        super.disconnectedCallback();
+        if (this.hashRateInterval !== null) {
+            clearInterval(this.hashRateInterval);
+            this.hashRateInterval = null;
+        }
+
+        for (const worker of this.solverWorkers || []) {
+            worker.terminate();
+            this.solverWorkers = null;
+        }
+    }
+
+    getCurrentWorkingNonce() {
+        return Atomics.load(new Uint32Array(this.sab), 0);
+    }
+
+    async fetchChallenge() {
+        this.errorMessage = '';
+        if (this.challengeData !== null) {
+            return;
+        }
+
+        if (this.challengejson !== '' && this.challengeData === null) {
+            this.challengeData = JSON.parse(this.challengejson);
+            this.challengejson = '';
+            return;
+        }
+
+        if (isServer) {
+            return;
+        }
+
+        await fetch(`${this.challengeUrl}/challenge`)
+            .then(response => response.json())
+            .then(data => {
+                this.challengeData = data;
+            })
+            .catch(error => {
+                console.error('Error fetching challenge:', error);
+                this.errorMessage = 'Failed to fetch challenge. Please try again.';
+            });
+    }
+
+    async initWorkers() {
+        this.solverWorkers = [];
+
+        const num_workers = navigator.hardwareConcurrency;
+        for (let i = 0; i < num_workers; i++) {
+            this.solverWorkers.push(new ChallengeWorker());
+        }
+
+        const atomics_view = new Int32Array(this.sab);
+        Atomics.store(atomics_view, 0, 0);
+        Atomics.store(atomics_view, 1, 0);
+
+        let wasm_module = await get_wasm_module();
+        let worker_promises: Promise<void>[] = [];
+        for (let i = 0; i < this.solverWorkers.length; i++) {
+            console.log('Worker', i);
+            const worker = this.solverWorkers[i]!;
+
+            worker_promises.push(new Promise<void>((resolve, reject) => {
+                const message_handler = (event: MessageEvent<SolutionMessage>) => {
+                    console.log('Worker', i, 'got message', event.data);
+
+                    if (event.data.type === WorkerResponseType.Error) {
+                        console.error("Worker error:", event.data.error);
+                        reject(event.data.error);
+                    }
+
+                    if (event.data.type === WorkerResponseType.InitOk) {
+                        resolve();
+                    }
+
+                    reject(new Error("Unexpected message from worker"));
+                };
+
+                const error_handler = (error: ErrorEvent) => {
+                    console.error("Worker error:", error);
+                    reject(error);
+                };
+
+                worker.addEventListener('message', message_handler);
+                worker.addEventListener('error', error_handler);
+
+                worker.postMessage({
+                    type: WorkerMessageType.Init,
+                    module: wasm_module,
+                    sab: this.sab,
+                } as WorkerRequest);
+            }));
+        }
+
+        const timeoutMs = 10 * 1000;
+        let timeout: number;
+        const timeoutPromise = new Promise((_, reject) => {
+            timeout = setTimeout(() => {
+                this.errorMessage = 'Failed to initialize workers in time. Please refresh the page.';
+                reject(new Error(`Function timed out after ${timeoutMs}ms`));
+            }, timeoutMs);
+        });
+
+        await Promise.race([
+            Promise.allSettled(worker_promises).then(() => {
+                console.log('All workers initialized');
+            }),
+            timeoutPromise,
+        ]).then(() => {
+            clearTimeout(timeout);
+        });
+    }
+
+    async issueChallengeToWorker(worker: Worker, request: ChallengeSolveRequest): Promise<SolutionMessage> {
+        return new Promise<SolutionMessage>((resolve, reject) => {
+            const message_handler = (event: MessageEvent<SolutionMessage>) => {
+                worker.removeEventListener('message', message_handler);
+                worker.removeEventListener('error', error_handler);
+
+                resolve(event.data);
+            };
+
+            const error_handler = (error: ErrorEvent) => {
+                worker.removeEventListener('error', error_handler);
+                worker.removeEventListener('message', message_handler);
+                console.error("Worker error:", error);
+
+                reject(error);
+            };
+
+            worker.addEventListener('message', message_handler);
+            worker.addEventListener('error', error_handler);
+
+            switch (request.strategy) {
+                case ChallengeStrategy.LeadingZeroes:
+                    worker.postMessage({
+                        strategy: ChallengeStrategy.LeadingZeroes,
+                        salt: request.salt,
+                        difficulty: request.difficulty,
+                    } as WorkerRequest);
+                    break;
+                case ChallengeStrategy.TargetNumber:
+                    worker.postMessage({
+                        strategy: ChallengeStrategy.TargetNumber,
+                        target: request.target,
+                        salt: request.salt,
+                    } as WorkerRequest);
+                    break;
+            }
+        });
+    }
+
+    async solveChallenge() {
+        if (!this.challengeData || this.solverWorkers === null) {
+            this.errorMessage = 'Captcha is not ready. Please wait or refresh.';
+            return;
+        }
+
+        if (this.solution !== '') {
+            return;
+        }
+
+        this.solveStartTime = performance.now();
+        this.hashRateInterval = setInterval(async () => {
+            const nonce = this.getCurrentWorkingNonce();
+
+            this.hashRate = (nonce / ((performance.now() - this.solveStartTime!) / 1000));
+        }, 250);
+
+        this.dispatchEvent(new CustomEvent('impost:solve', {
+            detail: {
+                solution: this.solution,
+            },
+            bubbles: true,
+            composed: true,
+        }))
+
+        console.log(this.challengeData);
+
+        this.isSolving = true;
+        this.errorMessage = '';
+        this.solution = '';
+
+        const atomics_view = new Int32Array(this.sab);
+        Atomics.store(atomics_view, 0, 0);
+        Atomics.store(atomics_view, 1, -1);
+
+        let request: ChallengeSolveRequest;
+
+        switch (this.challengeData.strategy) {
+            case ChallengeStrategy.LeadingZeroes:
+                request = {
+                    strategy: ChallengeStrategy.LeadingZeroes,
+                    salt: this.challengeData.salt,
+                    difficulty: this.challengeData.difficulty,
+                };
+                break;
+            case ChallengeStrategy.TargetNumber:
+                request = {
+                    strategy: ChallengeStrategy.TargetNumber,
+                    target: this.challengeData.target,
+                    salt: this.challengeData.salt,
+                };
+                break;
+        }
+
+        console.log('Sending challenge to workers...');
+        // TODO: the first response is not always the solution, due to cmpxchg 
+        // blocking, some workers may block on the read, and as soon as they 
+        // unblock, they return 0 since the challenge is already solved.
+        //
+        // We need to do a better job of tracking solvers, so if one worker
+        // errors out, we only error out if all workers have errored out.
+        let worker_promises: Promise<SolutionMessage>[] = [];
+        for (let worker of this.solverWorkers) {
+            // dispatch to all workers, func is async so it will not block
+            worker_promises.push(this.issueChallengeToWorker(worker, request));
+        }
+
+        let solution = await Promise.race(worker_promises);
+
+        if (solution.type === WorkerResponseType.Error) {
+            this.errorMessage = solution.error;
+            return;
+        }
+
+        if (solution.type !== WorkerResponseType.Solution) {
+            this.errorMessage = "Something went wrong, please try again later.";
+            return;
+        }
+
+        this.solution = Atomics.load(atomics_view, 1).toString();
+        this.isSolving = false;
+        this.solved = true;
+
+        if (this.hashRateInterval !== null) {
+            clearInterval(this.hashRateInterval);
+            this.hashRateInterval = null;
+        }
+
+        this.dispatchEvent(new CustomEvent('impost:solved', {
+            detail: {
+                solution: this.solution,
+            },
+            bubbles: true,
+            composed: true,
+        }))
+    }
+
+    solvePreventDefault(event: Event) {
+        event.preventDefault();
+
+        this.solveChallenge();
+    }
+
+    override render() {
+        if (this.challengejson !== '' && this.challengeData === null) {
+            this.challengeData = JSON.parse(this.challengejson);
+            this.challengejson = '';
+        }
+
+        if (this.errorMessage) {
+            return html`
+        <div class="error-message">${this.errorMessage}</div>
+      `;
+        }
+
+        if (this.challengeData === null) {
+            return html`
+        <div class="loading-message">Loading captcha challenge...</div>
+      `;
+        }
+
+        return html`
+        <div class="impost-widget">
+            <div class="impost-main">
+                <div class="impost-checkbox">
+                    ${!this.isSolving ? html`
+                        <input type="checkbox" id="impost-checkbox-${this.uid}" @click=${this.solvePreventDefault} @change=${this.solvePreventDefault} ?disabled=${this.disabled} ?checked=${this.solved}>
+                    ` : html`
+                        <svg xmlns="http://www.w3.org/2000/svg" width="20" height="20" viewBox="0 0 24 24">
+                            <!-- Icon from SVG Spinners by Utkarsh Verma - https://github.com/n3r4zzurr0/svg-spinners/blob/main/LICENSE -->
+                            <g stroke="currentColor">
+                                <circle cx="12" cy="12" r="9.5" fill="none" stroke-linecap="round" stroke-width="3">
+                                    <animate attributeName="stroke-dasharray" calcMode="spline" dur="1.5s" keySplines="0.42,0,0.58,1;0.42,0,0.58,1;0.42,0,0.58,1" keyTimes="0;0.475;0.95;1" repeatCount="indefinite" values="0 150;42 150;42 150;42 150"/>
+                                    <animate attributeName="stroke-dashoffset" calcMode="spline" dur="1.5s" keySplines="0.42,0,0.58,1;0.42,0,0.58,1;0.42,0,0.58,1" keyTimes="0;0.475;0.95;1" repeatCount="indefinite" values="0;-16;-59;-59"/>
+                                </circle>
+                                <animateTransform attributeName="transform" dur="2s" repeatCount="indefinite" type="rotate" values="0 12 12;360 12 12"/>
+                            </g>
+                        </svg>
+                    `}
+                </div>
+                <label for="impost-checkbox-${this.uid}">${this.solved ? 'Verified' : html`${this.isSolving ? 'Verifying...' : 'I am not a robot'}`}</label>
+            </div>
+
+            <div class="impost-footer">
+                ${this.isSolving && this.hashRate > 0 ? html`
+                    <div>
+                        <span>H/s:</span>
+                        <span>${this.hashRate.toFixed(2)}</span>
+                    </div>
+                ` : ``}
+                <div id="provider-link">
+                    Protected by <a href="https://github.com/impost/pow-captcha" target="_blank">Impost</a>
+                </div>
+            </div>
+        </div>
+
+        <input
+            type = "text"
+            id = "impost-solution"
+            class="hidden"
+            .value = ${this.solution}
+        />
+    `;
+    }
+}

packages/widget/src/solver-worker.ts

@@ -0,0 +1,91 @@
+// This worker just sits on another thread and waits for message to solve
+// challenges so that we dont block the render thread
+
+import {
+    type WorkerRequest,
+    type SolutionMessage,
+    WorkerMessageType,
+    WorkerResponseType,
+} from "./types/worker";
+
+import { ChallengeStrategy } from "@impost/lib";
+
+import { type SolverModule, init_solver, solve_leaading_zeroes_challenge, solve_target_number_challenge } from '@impost/lib/solver';
+
+let solver: SolverModule | null = null;
+
+let atomic_nonce: Int32Array | null = null;
+let atomic_solution: Int32Array | null = null;
+
+onmessage = async (event: MessageEvent<WorkerRequest>) => {
+    if (event.data.type === WorkerMessageType.Init) {
+        atomic_nonce = new Int32Array(event.data.sab, 0, 1);
+        atomic_solution = new Int32Array(event.data.sab, 4, 1);
+        let module = event.data.module;
+
+        try {
+            solver = await init_solver({
+                __get_solution: () => Atomics.load(atomic_solution!, 0),
+                __set_solution: (value: number) => Atomics.store(atomic_solution!, 0, value),
+                __cmpxchg_solution: (expected: number, replacement: number) => Atomics.compareExchange(atomic_solution!, 0, expected, replacement),
+                __fetch_add_nonce: (value: number) => Atomics.add(atomic_nonce!, 0, value),
+            }, module);
+        } catch (error: any) {
+            postMessage({
+                type: WorkerResponseType.Error,
+                error: `Could not load WASM solver: ${error.message}`,
+            } as SolutionMessage);
+            return;
+        }
+
+        if (!solver) {
+            postMessage({
+                type: WorkerResponseType.Error,
+                error: "Failed to load WASM solver",
+            } as SolutionMessage);
+            return;
+        }
+
+        postMessage({
+            type: WorkerResponseType.InitOk,
+        } as SolutionMessage);
+        return;
+    }
+
+    if (!solver) {
+        postMessage({
+            type: WorkerResponseType.Error,
+            error: "WASM solver not loaded",
+        } as SolutionMessage);
+        return;
+    }
+
+    if (atomic_nonce === null || atomic_solution === null) {
+        throw new Error("Atomics not initialized");
+    }
+
+    const { strategy } = event.data;
+
+    let solution: number;
+    switch (strategy) {
+        case ChallengeStrategy.LeadingZeroes:
+            solution = solve_leaading_zeroes_challenge(solver, event.data)
+            break;
+        case ChallengeStrategy.TargetNumber:
+            solution = solve_target_number_challenge(solver, event.data)
+            break;
+    }
+
+    // we are just assuming that if its less than -1, its the min i32
+    if (solution < 0) {
+        return postMessage({
+            type: WorkerResponseType.Error,
+            error: "failed to solve challenge",
+        } as SolutionMessage);
+    }
+
+    postMessage({
+        type: WorkerResponseType.Solution,
+        nonce: solution === -1 ? null : solution.toString()
+    } as SolutionMessage);
+};

packages/widget/src/types/worker.ts

@@ -0,0 +1,60 @@
+import { ChallengeStrategy } from "@impost/lib";
+
+export enum WorkerMessageType {
+    Init = "init",
+    Challenge = "challenge",
+}
+
+interface WorkerInitRequest {
+    type: WorkerMessageType.Init;
+    module: WebAssembly.Module;
+
+    sab: SharedArrayBuffer;
+}
+
+interface ChallengeLeadingZeroesSolveRequest {
+    strategy: ChallengeStrategy.LeadingZeroes;
+    salt: string;
+    difficulty: number;
+}
+
+interface WorkerChallengeLeadingZeroesSolveRequest extends ChallengeLeadingZeroesSolveRequest {
+    type: WorkerMessageType.Challenge;
+}
+
+interface ChallengeTargetNumberSolveRequest {
+    strategy: ChallengeStrategy.TargetNumber;
+    target: string;
+    salt: string;
+}
+
+interface WorkerChallengeTargetNumberSolveRequest extends ChallengeTargetNumberSolveRequest {
+    type: WorkerMessageType.Challenge;
+}
+
+export type ChallengeSolveRequest = ChallengeLeadingZeroesSolveRequest | ChallengeTargetNumberSolveRequest;
+type WorkerChallengeSolveRequest = WorkerChallengeLeadingZeroesSolveRequest | WorkerChallengeTargetNumberSolveRequest;
+
+export type WorkerRequest = WorkerInitRequest | WorkerChallengeSolveRequest;
+
+export enum WorkerResponseType {
+    Error = "error",
+    InitOk = "init_ok",
+    Solution = "solution",
+}
+
+interface ErrorMessageResponse {
+    type: WorkerResponseType.Error;
+    error: string;
+}
+
+interface SolutionMessageResponse {
+    type: WorkerResponseType.Solution;
+    nonce: string;
+}
+
+interface InitOkMessageResponse {
+    type: WorkerResponseType.InitOk;
+}
+
+export type SolutionMessage = ErrorMessageResponse | SolutionMessageResponse | InitOkMessageResponse;

packages/widget/src/vite-env.d.ts

@@ -0,0 +1 @@
+/// <reference types="vite/client" />

packages/widget/tsconfig.json

@@ -0,0 +1,27 @@
+{
+  "compilerOptions": {
+    "declaration": true,
+    "target": "ES2022",
+    "experimentalDecorators": true,
+    "useDefineForClassFields": false,
+    "module": "ESNext",
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "types": ["vite/client"],
+    "skipLibCheck": true,
+
+    /* Bundler mode */
+    "moduleResolution": "bundler",
+    "allowImportingTsExtensions": true,
+    "verbatimModuleSyntax": true,
+    "moduleDetection": "force",
+    "noEmit": true,
+
+    /* Linting */
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noFallthroughCasesInSwitch": true,
+    "noUncheckedSideEffectImports": true
+  },
+  "include": ["src"]
+}

packages/widget/vite.config.ts

@@ -0,0 +1,29 @@
+import { resolve } from 'path';
+import { defineConfig } from 'vite';
+import dts from 'vite-plugin-dts';
+
+export default defineConfig({
+    build: {
+        target: 'es2022',
+        lib: {
+            entry: resolve(__dirname, 'src/entry.ts'),
+            formats: ['es'],
+            fileName: 'impost',
+        },
+        rollupOptions: {
+            external: [/^lit/, /^@lit\//],
+            output: {
+                preserveModules: false,
+                dir: 'dist',
+            },
+        },
+        // WARN: this setting has caused issues for me in the past, but now it
+        // seems to work fine. I'm not sure why, but minifying the bundle saves
+        // 5KB, and it doesnt *cause* issues, so I'm leaving it on.
+        minify: true,
+    },
+
+    plugins: [
+        dts(),
+    ],
+});