cam-reverse/func_replacements.js

const u16_swap = (x) => ((x & 0xff00) >> 8) | ((x & 0x00ff) << 8);

const swap_endianness_u16 = (ptr) => {
  const bytes = ptr.readU16();
  const swapped = [(bytes & 0xff00) >> 8, bytes & 0x00ff];
  return swapped;
};
const swap_endianness_u32 = (ptr) => {
  const bytes = ptr.readU32();
  const swapped = [
    (bytes & 0xff000000) >> 24,
    (bytes & 0x00ff0000) >> 16,
    (bytes & 0x0000ff00) >> 8,
    bytes & 0x000000ff,
  ];
  return swapped;
};

const compare_buf = (a, b, len) => {
  console.log(`comparin len ${len}`);
  const ba = new Uint8Array(a.readByteArray(len));
  const bb = new Uint8Array(b.readByteArray(len));

  let deltas = new Uint8Array(len);
  let bad = false;
  for (let i = 0; i < len; i++) {
    if (ba[i] == bb[i]) {
      deltas[i] = 0;
    } else {
      deltas[i] = 0xff;
      bad = true;
    }
  }
  if (bad) {
    console.log("deltas");
    console.log(deltas.buffer);
    console.log("buf a");
    console.log(ba.buffer);
    console.log("buf b");
    console.log(bb.buffer);
    console.log("####");
  }
};

const Commands = {
  Close: 0xf1f0,
  LanSearchExt: 0xf132,
  LanSearch: 0xf130,
  P2PAlive: 0xf1e0,
  P2PAliveAck: 0xf1e1,
  Hello: 0xf100,
  P2pRdy: 0xf142,
  P2pReq: 0xf120,
  LstReq: 0xf167,
  DrwAck: 0xf1d1,
  Drw: 0xf1d0,
};

const CommandsByValue = Object.keys(Commands).reduce((acc, cur) => {
  acc[Commands[cur]] = cur;
  return acc;
}, {});

const pack_P2pHdr = (in_buf, out_buf) => {
  // shitty memcpy
  out_buf.writeByteArray(in_buf.readByteArray(4));
  return 4;
};

const writeCommand2 = (command, buf) => {
  buf.writeByteArray([(command & 0xff00) >> 8, command & 0xff]);
};
const writeCommand4 = (command, buf) => {
  buf.writeByteArray([(command & 0xff00) >> 8, command & 0xff, 0x00, 0x00]);
};
const create_Close = (buf) => {
  writeCommand4(Commands.Close, buf);
  return 4;
};

const create_LanSearchExt = (buf) => {
  writeCommand4(Commands.LanSearchExt, buf);
  return 4;
};

const create_LanSearch = (buf) => {
  writeCommand4(Commands.LanSearch, buf);
  return 4;
};

const create_P2pAliveAck = (buf) => {
  writeCommand4(Commands.P2PAliveAck, buf);
  return 4;
};
const create_P2pAlive = (buf) => {
  writeCommand4(Commands.P2PAlive, buf);
  return 4;
};

const create_Hello = (buf) => {
  writeCommand4(Commands.Hello, buf);
  return 4;
};

const create_P2pRdy = (outbuf, inbuf) => {
  // TODO: this is literlly the same as create_LstReq, just different command
  const P2PRDY_SIZE = 0x14;
  writeCommand2(Commands.P2pRdy, outbuf);
  outbuf.add(2).writeU16(P2PRDY_SIZE << 8);
  outbuf.add(8).writeU64(inbuf.readU64());
  outbuf.add(16).writeU64(inbuf.add(8).readU64());
  outbuf.add(2 * 0xc).writeU32(inbuf.add(16).readU32());
  return P2PRDY_SIZE + 4;
};

const create_P2pReq = (outbuf, inbuf, m_s_addr, addr_fam) => {
  const P2PREQ_SIZE = 0x24;
  writeCommand2(Commands.P2pReq, outbuf);
  outbuf.add(2).writeU16(P2PREQ_SIZE << 8);
  outbuf.add(8).writeU64(inbuf.readU64());
  outbuf.add(16).writeU64(inbuf.add(8).readU64());
  outbuf.add(2 * 0xc).writeU32(inbuf.add(16).readU32());

  outbuf.add(2 * 0xe).writeByteArray(swap_endianness_u16(m_s_addr));
  outbuf.add(2 * 0xf).writeByteArray(swap_endianness_u16(m_s_addr.add(2)));

  outbuf.add(2 * 0x12).writeU64(0);
  outbuf.add(2 * 0x10).writeByteArray(swap_endianness_u32(m_s_addr.add(4))); // ip address

  return P2PREQ_SIZE + 4;
};

const create_LstReq = (outbuf, inbuf) => {
  /* original
        in
                                 0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
     0123456789ABCDEF 00000000  42 41 54 43 00 00 00 00 00 09 4c fb 45 58 4c 56
     BATC......L.EXLV 00000010  53 00 00 00 00 00 00 00 00 00 00 00 S...........

        out
                                         0  1  2  3  4  5  6  7  8  9  A  B  C
     D  E  F 0123456789ABCDEF 00000000  f1 67 00 14 00 00 00 00 42 41 54 43 00
     00 00 00 .g......BATC.... 00000010  00 09 4c fb 45 58 4c 56 53 00 00 00
     ..L.EXLVS... retval 0x18

        */
  const LISTREQ_SIZE = 0x14;
  writeCommand2(Commands.LstReq, outbuf);
  outbuf.add(2).writeU16(LISTREQ_SIZE << 8);

  // 4 * sizeof(short)
  outbuf.add(8).writeU64(inbuf.readU64());
  // 8 * sizeof(short)
  outbuf.add(16).writeU64(inbuf.add(8).readU64());
  // 0xc * sizeof(short)
  outbuf.add(2 * 0xc).writeU32(inbuf.add(0x10).readU32());

  return LISTREQ_SIZE + 4; // this is actually wrong (and unused) in the code -- it is 0x1c
};

const dbg_create_DrwAck = (og_func) => {
  const create_DrwAck = (outbuf, idk_param2, channel, half_len, inbuf) => {
    // console.log(`2: ${idk_param2} 3: ${channel}, halflen: ${half_len}`);
    //  param2 is 0xd1 if "unlocked" and 0xd2 if "locked"?
    const copyLen = half_len * 2;
    writeCommand2(Commands.DrwAck, outbuf);
    outbuf.add(2).writeU16(u16_swap(copyLen + 4));
    outbuf.add(8).writeU8(idk_param2);
    outbuf.add(9).writeU8(channel);
    outbuf.add(10).writeU16(u16_swap(half_len));
    outbuf.add(12).writeByteArray(inbuf.readByteArray(copyLen));
    return half_len * 2 + 8; // this is wrong in the code as well - should be +12
  };
  return create_DrwAck;
};

const dbg_create_Drw = (og_func) => {
  const create_Drw = (
    outbuf,
    idk_param2,
    idk_param3,
    idk_param4,
    copy_len,
    inbuf,
  ) => {
    /// idk_param4 goes up by 0x100 per call

    // console.log(
    //   `2: ${idk_param2.toString(16)} 3: ${idk_param3.toString(16)} 4:
    //   ${idk_param4.toString(16)} copylen: ${copy_len}`,
    //);
    /*
     * 2: ffffffd1 3: 0 4: 3100 copylen: 44
        In buffer
                           0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
     0123456789ABCDEF 00000000  11 0a 31 10 24 00 00 00 75 39 4c 74 01 01 01 01
     ..1.$...u9Lt.... 00000010  01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
     ................ 00000020  01 01 01 01 01 01 01 01 01 01 01 00 ............
        OG retval 52
        OG out buffer
                           0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
     0123456789ABCDEF 00000000  f1 d0 00 30 00 00 00 00 d1 00 00 31 11 0a 31 10
     ...0.......1..1. 00000010  24 00 00 00 75 39 4c 74 01 01 01 01 01 01 01 01
     $...u9Lt........ 00000020  01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
     ................ 00000030  01 01 01 01
        */

    const copy_len_swapped = u16_swap(copy_len + 4);
    writeCommand2(Commands.Drw, outbuf);
    outbuf.add(2).writeU16(copy_len_swapped);
    outbuf.add(8).writeU8(0xd1);
    outbuf.add(10).writeU16(idk_param4);
    outbuf.add(12).writeByteArray(inbuf.readByteArray(copy_len));

    return copy_len + 8;
  };
  return create_Drw;
};
const dbg_pack_ClntPkt = (og_func) => {
  const pack_ClntPkt = (addr_fam, inbuf, outbuf) => {
    const cmd = u16_swap(inbuf.readU16());
    console.log(
      `pack_ClntPkt: cmd 0x${cmd.toString(16)} = ${
        CommandsByValue[cmd]
      }; fam ${addr_fam}; inbuf =>`,
    );
    //console.log(inbuf.readByteArray(16));

    //const ret = og_func(addr_fam, inbuf, outbuf);

    // const new_outbuf = Memory.alloc(ret);
    const hdrLen = pack_P2pHdr(inbuf, outbuf);
    const packFn = {
      [Commands.LanSearch]: () => hdrLen,
      [Commands.LanSearchExt]: () => hdrLen,
      [Commands.Close]: () => hdrLen,
      [Commands.Hello]: () => hdrLen,
      [Commands.P2pReq]: () =>
        hdrLen + pack_P2pReq4(inbuf.add(8), outbuf.add(hdrLen)),
      [Commands.LstReq]: () =>
        hdrLen + pack_P2pId(inbuf.add(8), outbuf.add(hdrLen)),
      [Commands.DrwAck]: () => {
        const pkt_size = u16_swap(inbuf.add(2).readU16());
        return hdrLen + pack_DrwAck(inbuf.add(8), pkt_size, outbuf.add(hdrLen));
      },
      [Commands.Drw]: () => {
        const pkt_size = u16_swap(inbuf.add(2).readU16());
        return hdrLen + pack_Drw(inbuf.add(8), pkt_size, outbuf.add(hdrLen));
      },
    };
    /*
	  // No PackClnt?
	  P2PAlive: 0xf1e0,
	  P2PAliveAck: 0xf1e1,

	  P2pRdy: 0xf142, // idk??
	  */

    const fn = packFn[cmd];
    if (fn == undefined) {
      console.error(`IDK how to handle ${cmd}`);
    } else {
      const my_ret = fn();
      //compare_buf(outbuf, new_outbuf, ret);
      //console.log(new_outbuf.readByteArray(ret));
      return my_ret;
    }
    return -1;
  };
  return pack_ClntPkt;
};

const pack_Drw = (inbuf, m_pkt_size, outbuf) => {
  // a shitty memcpy?
  const DRW_HDR_SIZE = 0x4;

  outbuf.writeU8(inbuf.readU8());
  outbuf.add(1).writeU8(inbuf.add(1).readU8());
  outbuf.add(2).writeU16(inbuf.add(2).readU16());
  outbuf
    .add(4)
    .writeByteArray(inbuf.add(4).readByteArray(m_pkt_size - DRW_HDR_SIZE));

  return m_pkt_size;
};
// FIXME literally identical to pack_Drw
const pack_DrwAck = (inbuf, m_pkt_size, outbuf) => {
  // a shitty memcpy?
  const DRW_ACK_HDR_SIZE = 0x4;

  outbuf.writeU8(inbuf.readU8());
  outbuf.add(1).writeU8(inbuf.add(1).readU8());
  outbuf.add(2).writeU16(inbuf.add(2).readU16());
  outbuf
    .add(4)
    .writeByteArray(inbuf.add(4).readByteArray(m_pkt_size - DRW_ACK_HDR_SIZE));

  return m_pkt_size;
};

const pack_P2pId = (inbuf, outbuf) => {
  outbuf.writeU64(inbuf.readU64());
  outbuf.add(8).writeU32(inbuf.add(8).readU32());
  outbuf.add(0xc).writeU64(inbuf.add(0xc).readU32());

  return 0x14;
};

const pack_P2pReq4 = (inbuf, outbuf) => {
  // a shitty memcpy?
  Memory.copy(outbuf, inbuf, 0x24);
  return 0x24;
};

export const replace_func = (stub, ret, args) => {
  const name_in_elf = stub.name.replace("dbg_", ""); // UGH  FIXME
  const symbol_addr = DebugSymbol.fromName(name_in_elf).address;
  if (symbol_addr == 0) {
    console.error(`Could not find ${name_in_elf}`);
    return;
  }

  const orig_func = new NativeFunction(symbol_addr, ret, args);

  let replacement_func;
  if (stub.name.startsWith("dbg_")) {
    replacement_func = stub(orig_func);
  } else {
    replacement_func = stub;
  }

  console.log(
    `Replacing ${name_in_elf}, signature "${ret} ${name_in_elf}(${args})"`,
  );

  Interceptor.replace(
    symbol_addr,
    new NativeCallback(replacement_func, ret, args),
  );
};

/* Send_Pkt_LanSearch =
 * create_LanSearch(buf)
 * pack_ClntPkt(2, buf, &packed_buf)
 * UdpPktSend(packed_buf)
 */
/* Send_Pkt_Hello =
 * create_Hello
 * pack_ClntPkt
 * UdpPktSend
 */
export const replaceFunctions = () => {
  const replacements = [
    [create_P2pAlive, "uint8", ["pointer"]],
    [create_P2pAliveAck, "uint8", ["pointer"]],
    [create_LanSearch, "uint8", ["pointer"]],
    [create_LanSearchExt, "uint8", ["pointer"]],
    [create_Hello, "uint8", ["pointer"]],
    [create_Close, "uint8", ["pointer"]],
    [
      dbg_create_Drw,
      "uint",
      ["pointer", "uint64", "uint8", "uint16", "uint32", "pointer"],
    ],
    [
      dbg_create_DrwAck,
      "uint",
      ["pointer", "uint8", "uint8", "uint16", "pointer"],
    ],
    [create_P2pReq, "uint8", ["pointer", "pointer", "pointer", "uint"]],
    [create_LstReq, "uint8", ["pointer", "pointer"]],
    [create_P2pRdy, "uint8", ["pointer", "pointer"]],
    [pack_P2pHdr, "uint8", ["pointer", "pointer"]],
    [pack_Drw, "uint8", ["pointer", "uint16", "pointer"]],
    [pack_DrwAck, "uint8", ["pointer", "uint16", "pointer"]],
    [pack_P2pId, "uint32", ["pointer", "pointer"]],
    [pack_P2pReq4, "uint64", ["pointer", "pointer"]],
    [dbg_pack_ClntPkt, "uint32", ["uint32", "pointer", "pointer"]],
  ];

  replacements.forEach((x) => replace_func(...x));
  return replacements.map((x) => x[0].name.replace("dbg_", ""));
};