****[**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.\
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:
* 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.
* 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.**
* The remaining parameters are any** values that are required by the method** (op).
Note that in order to debug binaries, **SIP needs to be disabled **(`csrutil disable` or `csrutil enable --without debug`) or to copy the binaries to a temporary folder and **remove the signature **with `codesign --remove-signature <binary-path> `or allow the debugging of the binary (you can use [this script](https://gist.github.com/carlospolop/a66b8d72bb8f43913c4b5ae45672578b))
Note that in order to **instrument system binarie**s, (such as `cloudconfigurationd`) on macOS, **SIP must be disabled** (just removing the signature won't work).
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.
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.
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)
#### Examples
* In line
```bash
#Count the number of syscalls of each running process
****[**ProcessMonitor**](https://objective-see.com/products/utilities.html#ProcessMonitor) is a very useful tool to check the process related actions a process is performing (for example, monitor which new processes a process is creating).
****[**FileMonitor**](https://objective-see.com/products/utilities.html#FileMonitor) allows to monitor file events (such as creation, modifications, and deletions) providing detailed information about such events.
****[**Taskexplorer**](https://objective-see.com/products/taskexplorer.html) is useful to see the **libraries** used by a binary, the **files** it's using and the **network** connections.\
| **run (r)** | Starting execution, which will continue unabated until a breakpoint is hit or the process terminates. |
| **continue (c)** | Continue execution of the debugged process. |
| **nexti (n)** | Execute the next instruction. This command will skip over function calls. |
| **stepi (s)** | Execute the next instruction. Unlike the nexti command, this command will step into function calls. |
| **finish (f)** | Execute the rest of the instructions in the current function (“frame”) return and halt. |
| **control + c** | Pause execution. If the process has been run (r) or continued (c), this will cause the process to halt ...wherever it is currently executing. |
| **print object (po)** | <p>This will print the object referenced by the param</p><p>po $raw</p><p><code>{</code></p><p><code> dnsChanger = {</code></p><p><code> "affiliate" = "";</code></p><p><code> "blacklist_dns" = ();</code></p><p>Note that most of Apple’s Objective-C APIs or methods return objects, and thus should be displayed via the “print object” (po) command. If po doesn't produce a meaningful output use <code>x/b</code><br></p> |
When calling the **`objc_sendMsg`** function, the **rsi** register holds the **name of the method **as a null-terminated (“C”) string. To print the name via lldb do:
* As noted in this writeup, “[Defeating Anti-Debug Techniques: macOS ptrace variants](https://alexomara.com/blog/defeating-anti-debug-techniques-macos-ptrace-variants/)” :\
ReportCrash **analyzes crashing processes and saves a crash report to disk**. A crash report contains information that can **help a developer diagnose** the cause of a crash.\
For applications and other processes** running in the per-user launchd context**, ReportCrash runs as a LaunchAgent and saves crash reports in the user's `~/Library/Logs/DiagnosticReports/`\
For daemons, other processes **running in the system launchd context** and other privileged processes, ReportCrash runs as a LaunchDaemon and saves crash reports in the system's `/Library/Logs/DiagnosticReports`
If you are worried about crash reports **being sent to Apple** you can disable them. If not, crash reports can be useful to **figure out how a server crashed**.
[**Checkout this section**](./#file-extensions-apps)** **to find out how you can find which app is responsible of **handling the specified scheme or protocol**.
