altcha/dist/workers/sha.js

Privacy-first CAPTCHA widget, compliant with global regulations (GDPR/HIPAA/CCPA/LGDP/DPDPA/PIPL) and WCAG accessible. No tracking, self-verifying.

(function() {
  "use strict";
  function bufferStartsWith(buffer, prefix) {
    if (prefix.length > buffer.length) {
      return false;
    }
    for (let i = 0; i < prefix.length; i++) {
      if (buffer[i] !== prefix[i]) {
        return false;
      }
    }
    return true;
  }
  function bufferToHex(buffer) {
    return Array.from(new Uint8Array(buffer)).map((b) => b.toString(16).padStart(2, "0")).join("");
  }
  function concatBuffers(a, b) {
    const out = new Uint8Array(a.length + b.length);
    out.set(a, 0);
    out.set(b, a.length);
    return out;
  }
  function hexToBuffer(hex) {
    if (hex.length % 2 !== 0) {
      throw new Error(`Hex string must have an even length. Got: ${hex}`);
    }
    const buffer = new ArrayBuffer(hex.length / 2);
    const view = new DataView(buffer);
    for (let i = 0; i < hex.length; i += 2) {
      const byteString = hex.substring(i, i + 2);
      const byteValue = parseInt(byteString, 16);
      view.setUint8(i / 2, byteValue);
    }
    return new Uint8Array(buffer);
  }
  async function delay(ms) {
    await new Promise((resolve) => setTimeout(resolve, ms));
  }
  function timeDuration(start) {
    return Math.floor((performance.now() - start) * 10) / 10;
  }
  class PasswordBuffer {
    constructor(nonce, mode = "uint32") {
      this.nonce = nonce;
      this.mode = mode;
      this.buffer = new Uint8Array(this.nonce.length + this.COUNTER_BYTES);
      this.buffer.set(this.nonce, 0);
      this.dataView = new DataView(this.buffer.buffer);
    }
    COUNTER_BYTES = 4;
    buffer;
    dataView;
    encoder = new TextEncoder();
    /**
     * Appends the counter to the nonce buffer.
     * In 'string' mode, encodes the counter as a UTF-8 string.
     * In 'uint32' mode, writes the counter as a big-endian 32-bit integer.
     */
    setCounter(n) {
      if (this.mode === "string") {
        return concatBuffers(this.nonce, this.encoder.encode(n.toString()));
      }
      this.dataView.setUint32(this.nonce.length, n, false);
      return this.buffer;
    }
  }
  async function solveChallenge(options) {
    const {
      challenge,
      controller,
      counterMode = "uint32",
      counterStart = 0,
      counterStep = 1,
      deriveKey: deriveKey2,
      timeout = 9e4
    } = options;
    const { nonce, keyPrefix, salt } = challenge.parameters;
    const nonceBuf = hexToBuffer(nonce);
    const saltBuf = hexToBuffer(salt);
    const keyPrefixBuf = keyPrefix.length % 2 === 0 ? hexToBuffer(keyPrefix) : null;
    const password = new PasswordBuffer(nonceBuf, counterMode);
    const start = performance.now();
    let counter = counterStart;
    let iterations = 0;
    let derivedKeyHex = "";
    let lastYield = start;
    while (true) {
      if (controller?.signal.aborted || timeout && iterations % 10 === 0 && performance.now() - start > timeout) {
        return null;
      }
      const { derivedKey } = await deriveKey2(
        challenge.parameters,
        saltBuf,
        password.setCounter(counter)
      );
      if (iterations % 10 === 0 && performance.now() - lastYield > 200) {
        await delay(0);
        lastYield = performance.now();
      }
      if (keyPrefixBuf ? bufferStartsWith(derivedKey, keyPrefixBuf) : bufferToHex(derivedKey).startsWith(keyPrefix)) {
        derivedKeyHex = bufferToHex(derivedKey);
        break;
      }
      counter = counter + counterStep;
      iterations = iterations + 1;
    }
    return {
      counter,
      derivedKey: derivedKeyHex,
      time: timeDuration(start)
    };
  }
  function handler(options) {
    const { deriveKey: deriveKey2 } = options;
    let controller = void 0;
    self.onmessage = async (message) => {
      const { challenge, counterMode, counterStart, counterStep, timeout, type } = message.data;
      if (type === "abort") {
        controller?.abort();
      } else if (type === "work") {
        controller = new AbortController();
        let solution;
        try {
          solution = await solveChallenge({
            challenge,
            controller,
            counterStart,
            counterStep,
            deriveKey: deriveKey2,
            counterMode,
            timeout
          });
        } catch (err) {
          return self.postMessage({ error: err });
        }
        self.postMessage(solution);
      }
    };
  }
  async function deriveKey(parameters, salt, password) {
    const { algorithm, keyLength = 32 } = parameters;
    const iterations = Math.max(1, parameters.cost);
    let data = void 0;
    let derivedKey = void 0;
    for (let i = 0; i < iterations; i++) {
      if (i === 0) {
        data = concatBuffers(salt, password);
      } else {
        data = derivedKey;
      }
      derivedKey = new Uint8Array(
        (await crypto.subtle.digest(algorithm, data)).slice(0, keyLength)
      );
    }
    return {
      parameters: {},
      derivedKey
    };
  }
  handler({
    deriveKey
  });
})();