Class ChainBase

g2all/700/module/chain.js:174–526

//   stack_size: the size of the stack
//   upper_pad: the amount of extra space above stack
export class ChainBase {
  constructor(stack_size = 0x1000, upper_pad = 0x10000) {
    this._is_dirty = false;
    this.position = 0;

    const return_value = new Uint32Array(4);
    this._return_value = return_value;
    this.retval_addr = get_view_vector(return_value);

    const errno = new Uint32Array(1);
    this._errno = errno;
    this.errno_addr = get_view_vector(errno);

    const full_stack_size = upper_pad + stack_size;
    const stack_buffer = new ArrayBuffer(full_stack_size);
    const stack = new DataView(stack_buffer, upper_pad);
    this.stack = stack;
    this.stack_addr = get_view_vector(stack);
    this.stack_size = stack_size;
    this.full_stack_size = full_stack_size;
  }

  // use this if you want to write a new ROP chain but don't want to allocate
  // a new instance
  empty() {
    this.position = 0;
  }

  // flag indicating whether .run() was ever called with this chain
  get is_dirty() {
    return this._is_dirty;
  }

  clean() {
    this._is_dirty = false;
  }

  dirty() {
    this._is_dirty = true;
  }

  check_allow_run() {
    if (this.position === 0) {
      throw Error("chain is empty");
    }
    if (this.is_dirty) {
      throw Error("chain already ran, clean it first");
    }
  }

  reset() {
    this.empty();
    this.clean();
  }

  get retval_int() {
    return this._return_value[0] | 0;
  }