139 lines
4.5 KiB
Markdown
139 lines
4.5 KiB
Markdown
# Inspecting and debugging Mac OS Sotware
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## Static Analysis
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### otool
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```bash
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otool -L /bin/ls #List dynamically linked libraries
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otool -tv /bin/ps #Decompile application
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```
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### SuspiciousPackage
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\*\*\*\*[**SuspiciousPackage**](https://mothersruin.com/software/SuspiciousPackage/get.html) is a tool useful to inspect **.pkg** files \(installers\) and see what is inside before installing it.
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These installers have `preinstall` and `postinstall` bash scripts that malware authors usually abuse to **persist** **the** **malware**.
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### hdiutil
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This tool allows to **mount** Apple disk images \(**.dmg**\) files to inspect them before running anything:
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```bash
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hdiutil attach ~/Downloads/Firefox\ 58.0.2.dmg
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```
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It will be mounted in `/Volumes`
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### Objective-C
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When a function is called in a binary that uses objective-C, the compiled code instead of calling that function, it will call **`objc_msgSend`**. Which will be calling the final function:
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The params this function expects are:
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* The first parameter \(**self**\) is "a pointer that points to the **instance of the class that is to receive the message**". Or more simply put, it’s the object that the method is being invoked upon. If the method is a class method, this will be an instance of the class object \(as a whole\), whereas for an instance method, self will point to an instantiated instance of the class as an object.
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* The second parameter, \(**op**\), is "the selector of the method that handles the message". Again, more simply put, this is just the **name of the method.**
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* The remaining parameters are any **values that are required by the method** \(op\).
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| **Argument** | **Register** | **\(for\) objc\_msgSend** |
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| :--- | :--- | :--- |
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| **1st argument** | **rdi** | **self: object that the method is being invoked upon** |
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| **2nd argument** | **rsi** | **op: name of the method** |
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| **3rd argument** | **rdx** | **1st argument to the method** |
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| **4th argument** | **rcx** | **2nd argument to the method** |
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| **5th argument** | **r8** | **3rd argument to the method** |
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| **6th argument** | **r9** | **4th argument to the method** |
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| **7th+ argument** | **rsp+ \(on the stack\)** | **5th+ argument to the method** |
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## Dynamic Analysis
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{% hint style="warning" %}
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These tools require **SIP to be disabled** or to copy the binaries to a temporary folder and **remove the signature** with `codesign --remove-signature <binary-path>`
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{% endhint %}
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### dtruss
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```bash
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dtruss -c ls #Get syscalls of ls
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dtruss -c -p 1000 #get syscalls of PID 1000
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```
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### ktrace
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You can use this one even with **SIP activated**
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```bash
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ktrace trace -s -S -t c -c ls | grep "ls("
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```
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### dtrace
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It allows users access to applications at an extremely **low level** and provides a way for users to **trace** **programs** and even change their execution flow. Dtrace uses **probes** which are **placed throughout the kernel** and are at locations such as the beginning and end of system calls.
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The available probes of dtrace can be obtained with:
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```bash
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dtrace -l | head
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ID PROVIDER MODULE FUNCTION NAME
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1 dtrace BEGIN
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2 dtrace END
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3 dtrace ERROR
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43 profile profile-97
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44 profile profile-199
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```
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The probe name consists of four parts: the provider, module, function, and name \(`fbt:mach_kernel:ptrace:entry`\). If you not specifies some part of the name, Dtrace will apply that part as a wildcard.
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A more detailed explanation and more examples can be found in [https://illumos.org/books/dtrace/chp-intro.html](https://illumos.org/books/dtrace/chp-intro.html)
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#### Examples
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* In line
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```bash
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#Count the number of syscalls of each running process
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sudo dtrace -n 'syscall:::entry {@[execname] = count()}'
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```
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* script
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```bash
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syscall:::entry
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/pid == $1/
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{
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}
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#Log every syscall of a PID
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sudo dtrace -s script.d 1234
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```
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```bash
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syscall::open:entry
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{
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printf("%s(%s)", probefunc, copyinstr(arg0));
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}
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syscall::close:entry
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{
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printf("%s(%d)\n", probefunc, arg0);
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}
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#Log files opened and closed by a process
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sudo dtrace -s b.d -c "cat /etc/hosts"
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```
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```bash
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syscall:::entry
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{
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;
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}
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syscall:::return
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{
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printf("=%d\n", arg1);
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}
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#Log sys calls with values
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sudo dtrace -s syscalls_info.d -c "cat /etc/hosts"
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```
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