denoFun.ts

const maps = () => Deno.readTextFileSync("/proc/self/maps").trim();
const parseMaps = (maps: string) => {
  const data = [];
  for (const line of maps.split("\n")) {
    const [adddrRange, flags, , , , name] = line.split(/ +/);
    data.push({
      name: name !== "" ? name : undefined,
      startAddr: parseInt(adddrRange.split("-")[0], 16),
      endAddr: parseInt(adddrRange.split("-")[1], 16),
      flags: {
        r: flags.includes("r"),
        w: flags.includes("w"),
      },
    });
  }
  return data;
};

const data = parseMaps(maps());
const mem = Deno.openSync(`/proc/self/mem`, { read: true, write: true });
const heap = data.find((d) => d.name === "[heap]")!;

const ankor = new TextEncoder().encode(
  "hello",
);
const buf = new Uint8Array(512);
let count = 0;

Deno.seekSync(mem.rid, heap.startAddr, Deno.SeekMode.Start);

while (1) {
  const n = (await Deno.read(mem.rid, buf))!;
  count += n;
  const data = decode(buf.slice(0, n));
  if (
    data.includes(
      decode(ankor),
    )
  ) {
    const o = findSubArrayIndex(buf, ankor);
    if (!data.includes(decode(ankor) + '"')) { // "string is code section, if its not it we probably hit the right spot
      console.log(decode(ankor));
      Deno.seekSync(mem.rid, -n! + o, Deno.SeekMode.Current);
      await mem.write(encode("world"));
      console.log(decode(ankor));
      Deno.exit(0);
    }
  }
}

async function _printBuf() {
  const buf = new Uint8Array(512);
  await Deno.read(mem.rid, buf);
  console.log(new TextDecoder().decode(buf));
}
function encode(str: string) {
  return new TextEncoder().encode(str);
}
function decode(buf: Uint8Array) {
  return new TextDecoder().decode(buf);
}
function findSubArrayIndex(array: Uint8Array, subArray: Uint8Array) {
  for (let i = 0; i < array.length - subArray.length; i++) {
    if (
      array.slice(i, i + subArray.length).every((v, j) => v === subArray[j])
    ) {
      return i;
    }
  }
  return -1;
}