Frida snippet used to hook hashing methods

frida_widm_hashing_hooks.js

Java.perform(function() {
  const target = Java.use('nl.avro.demol.base.extensions.StringKt');

  target.calculateHmac.implementation = function() {
    const args = JSON.stringify(arguments, null, 2);
    const retVal = target.calculateHmac.apply(this, arguments);

    console.log('[!] calculateHmac called!');
    console.log('Arguments:', args);

    return retVal;
  }

  target.hmac.implementation = function() {
    const args = JSON.stringify(arguments, null, 2);
    const retVal = target.hmac.apply(this, arguments);

    console.log('[!] hmac called!');
    console.log('Arguments:', args);

    var buffer = Java.array('byte', retVal);
    var result = "";
    for (var i = 0; i < buffer.length; ++i) {
        result+= (String.fromCharCode(buffer[i]));
    }

    console.log('Return value: ', result);

    return retVal;
  }
});