Class ChainBase

g2all/900/module/chain.js:177–532

//   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;
    }