Exploitable crypto js code. Three exploits, one if you can load code before this module, one if you control the parameter passed to CryptoAPI.sha1.hash, and one if you can load code after this module

crypto.js

var CryptoAPI = (function() {
  var encoding = {
    a2b: function(a) { },
    b2a: function(b) { }
  };

  var API = {
    sha1: {
      name: 'sha1',
      identifier: '2b0e03021a',
      size: 20,
      block: 64,
      hash: function(s) {
        var len = (s += '\x80').length,
            blocks = len >> 6,
            chunk = len & 63,
            res = "",
            i = 0,
            j = 0,
            H = [0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476, 0xC3D2E1F0],
            w = [];

        while (chunk++ != 56) {
          s += "\x00";
          if (chunk == 64) {
            blocks++;
            chunk = 0;
          }
        }

        for (s += "\x00\x00\x00\x00", chunk = 3, len = 8 * (len - 1); chunk >= 0; chunk--) {
          s += encoding.b2a(len >> (8 * chunk) & 255);
        }

        for (i = 0; i < s.length; i++) {
          j = (j << 8) + encoding.a2b(s[i]);
          if ((i & 3) == 3) {
            w[(i >> 2) & 15] = j;
            j = 0;
          }
          if ((i & 63) == 63) CryptoAPI.sha1._round(H, w);
        }

        for (i = 0; i < H.length; i++)
          for (j = 3; j >= 0; j--)
            res += encoding.b2a(H[i] >> (8 * j) & 255);
        return res;
      }, // End "hash"
      _round: function(H, w) { }
    } // End "sha1"
  }; // End "API"

  return API; // End body of anonymous function
})(); // End "CryptoAPI"

module.exports = CryptoAPI;

Could you please elaborate on the exploits? Thanks!

I could find one vulnerability and the exploit.