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MIG was created to **simplify the process of Mach IPC** code creation. It basically **generates the needed code** for server and client to communicate with a given definition. Even if the generated code is ugly, a developer will just need to import it and his code will be much simpler than before.
### Example
Create a definition file, in this case with a very simple function:
{% code title="myipc.defs" %}
```cpp
subsystem myipc 500; // Arbitrary name and id
userprefix USERPREF; // Prefix for created functions in the client
serverprefix SERVERPREF; // Prefix for created functions in the server
#include <mach/mach_types.defs>
#include <mach/std_types.defs>
simpleroutine Subtract(
server_port : mach_port_t;
n1 : uint32_t;
n2 : uint32_t);
```
{% endcode %}
Now use mig to generate the server and client code that will be able to comunicate within each other to call the Subtract function:
Several new files will be created in the current directory.
In the files **`myipcServer.c`** and **`myipcServer.h`** you can find the declaration and definition of the struct **`SERVERPREFmyipc_subsystem`**, which basically defines the function to call based on the received message ID (we indicated a starting number of 500):
{% tabs %}
{% tab title="myipcServer.c" %}
```c
/* Description of this subsystem, for use in direct RPC */
In this example we have only defined 1 function in the definitions, but if we would have defined more functions, they would have been inside the array of **`SERVERPREFmyipc_subsystem`** and the first one would have been assigned to the ID **500**, the second one to the ID **501**...
Actually it's possible to identify this relation in the struct **`subsystem_to_name_map_myipc`** from **`myipcServer.h`**:
```c
#ifndef subsystem_to_name_map_myipc
#define subsystem_to_name_map_myipc \
{ "Subtract", 500 }
#endif
```
Finally, another important function to make the server work will be **`myipc_server`**, which is the one that will actually **call the function** related to the received id:
printf("bootstrap_look_up() failed with code 0x%x\n", kr);
return 1;
}
printf("Port right name %d\n", port);
USERPREFSubtract(port, 40, 2);
}
```
{% endtab %}
{% endtabs %}
### Binary Analysis
As many binaries now use MIG to expose mach ports, it's interesting to know how to **identify that MIG was used** and the **functions that MIG executes** with each message ID.
[**jtool2**](../../macos-apps-inspecting-debugging-and-fuzzing/#jtool2) can parse MIG information from a Mach-O binary indicating the message ID and identifying the function to execute:
```bash
jtool2 -d __DATA.__const myipc_server | grep MIG
```
It was previously mentioned that the function that will take care of **calling the correct function depending on the received message ID** was `myipc_server`. However, you usually won't have the symbols of the binary (no functions names), so it's interesting to **check how it looks like decompiled** as it will always be very similar (the code of this function is independent from the functions exposed):
{% tabs %}
{% tab title="myipc_server decompiled 1" %}
<preclass="language-c"><codeclass="lang-c">int _myipc_server(int arg0, int arg1) {
var_10 = arg0;
var_18 = arg1;
// Initial instructions to find the proper function ponters
Actually if you go to the function **`0x100004000`** you will find the array of **`routine_descriptor`** structs. The first element of the struct is the **address** where the **function** is implemented, and the **struct takes 0x28 bytes**, so each 0x28 bytes (starting from byte 0) you can get 8 bytes and that will be the **address of the function** that will be called:
<summary><strong>Learn AWS hacking from zero to hero with</strong><ahref="https://training.hacktricks.xyz/courses/arte"><strong>htARTE (HackTricks AWS Red Team Expert)</strong></a><strong>!</strong></summary>
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* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** 🐦 [**@carlospolopm**](https://twitter.com/carlospolopm)**.**
* **Share your hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
