mirror of
https://github.com/carlospolop/hacktricks
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292 lines
19 KiB
Markdown
292 lines
19 KiB
Markdown
# MacOS Apps - Inspecting, debugging and Fuzzing
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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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.png>)
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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** | <p><strong>rsp+</strong><br><strong>(on the stack)</strong></p> | **5th+ argument to the method** |
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### Packed binaries
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* Check for high entropy
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* Check the strings (is there is almost no understandable string, packed)
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* The UPX packer for MacOS generates a section called "\_\_XHDR"
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## Dynamic Analysis
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{% hint style="warning" %}
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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))
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{% endhint %}
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{% hint style="warning" %}
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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).
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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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### ProcessMonitor
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[**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).
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### FileMonitor
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[**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.
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### fs\_usage
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Allows to follow actions performed by processes:
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```bash
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fs_usage -w -f filesys ls #This tracks filesystem actions of proccess names containing ls
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fs_usage -w -f network curl #This tracks network actions
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```
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### TaskExplorer
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[**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.\
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It also checks the binary processes against **virustotal** and show information about the binary.
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### lldb
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**lldb** is the de **facto tool** for **macOS** binary **debugging**.
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```bash
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lldb ./malware.bin
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lldb -p 1122
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lldb -n malware.bin
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lldb -n malware.bin --waitfor
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```
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| **(lldb) Command** | **Description** |
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| ----------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| **run (r)** | Starting execution, which will continue unabated until a breakpoint is hit or the process terminates. |
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| **continue (c)** | Continue execution of the debugged process. |
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| **nexti (n)** | Execute the next instruction. This command will skip over function calls. |
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| **stepi (s)** | Execute the next instruction. Unlike the nexti command, this command will step into function calls. |
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| **finish (f)** | Execute the rest of the instructions in the current function (“frame”) return and halt. |
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| **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. |
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| **breakpoint (b)** | <p>b main</p><p>b -[NSDictionary objectForKey:]</p><p>b 0x0000000100004bd9</p><p>br l #Breakpoint list</p><p>br e/dis <num> #Enable/Disable breakpoint</p><p>breakpoint delete <num></p> |
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| **help** | <p>help breakpoint #Get help of breakpoint command</p><p>help memory write #Get help to write into the memory</p> |
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| **reg** | <p>reg read $rax</p><p>reg write $rip 0x100035cc0</p> |
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| **x/s \<reg/memory address>** | Display the memory as a null-terminated string. |
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| **x/i \<reg/memory address>** | Display the memory as assembly instruction. |
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| **x/b \<reg/memory address>** | Display the memory as byte. |
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| **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> |
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| **memory write** | memory write 0x100600000 -s 4 0x41414141 #Write AAAA in that address |
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{% hint style="info" %}
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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:
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`(lldb) x/s $rsi: 0x1000f1576: "startMiningWithPort:password:coreCount:slowMemory:currency:"`
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`(lldb) print (char*)$rsi:`\
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`(char *) $1 = 0x00000001000f1576 "startMiningWithPort:password:coreCount:slowMemory:currency:"`
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`(lldb) reg read $rsi: rsi = 0x00000001000f1576 "startMiningWithPort:password:coreCount:slowMemory:currency:"`
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{% endhint %}
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### Anti-Dynamic Analysis
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#### VM detection
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* The command **`sysctl hw.model`** returns "Mac" when the **host is a MacOS** but something different when it's a VM.
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* Playing with the values of **`hw.logicalcpu`** and **`hw.physicalcpu`** some malwares try to detect if it's a VM.
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* Some malwares can also **detect** if the machine is **VMware** based on the MAC address (00:50:56).
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* It's also possible to find **if a process is being debugged** with a simple code such us:
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* `if(P_TRACED == (info.kp_proc.p_flag & P_TRACED)){ //process being debugged }`
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* It can also invoke the **`ptrace`** system call with the **`PT_DENY_ATTACH`** flag. This **prevents** a deb**u**gger from attaching and tracing.
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* You can check if the **`sysctl` ** or**`ptrace`** function is being **imported** (but the malware could import it dynamically)
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* As noted in this writeup, “[Defeating Anti-Debug Techniques: macOS ptrace variants](https://alexomara.com/blog/defeating-anti-debug-techniques-macos-ptrace-variants/)” :\
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“_The message Process # exited with **status = 45 (0x0000002d)** is usually a tell-tale sign that the debug target is using **PT\_DENY\_ATTACH**_”
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## Fuzzing
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### [ReportCrash](https://ss64.com/osx/reportcrash.html#:\~:text=ReportCrash%20analyzes%20crashing%20processes%20and%20saves%20a%20crash%20report%20to%20disk.\&text=ReportCrash%20also%20records%20the%20identity,when%20a%20crash%20is%20detected.)
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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.\
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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/`\
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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`
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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**.
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```bash
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#To disable crash reporting:
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launchctl unload -w /System/Library/LaunchAgents/com.apple.ReportCrash.plist
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sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.ReportCrash.Root.plist
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#To re-enable crash reporting:
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launchctl load -w /System/Library/LaunchAgents/com.apple.ReportCrash.plist
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sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.ReportCrash.Root.plist
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```
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### Sleep
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While fuzzing in a MacOS it's important to not allow the Mac to sleep:
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* systemsetup -setsleep Never
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* pmset, System Preferences
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* [KeepingYouAwake](https://github.com/newmarcel/KeepingYouAwake)
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#### SSH Disconnect
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If you are fuzzing via a SSH connection it's important to make sure the session isn't going to day. So change the sshd\_config file with:
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* TCPKeepAlive Yes
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* ClientAliveInterval 0
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* ClientAliveCountMax 0
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```bash
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sudo launchctl unload /System/Library/LaunchDaemons/ssh.plist
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sudo launchctl load -w /System/Library/LaunchDaemons/ssh.plist
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```
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### Internal Handlers
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[**Checkout this section**](./#file-extensions-apps) to find out how you can find which app is responsible of **handling the specified scheme or protocol**.
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### Enumerating Network Processes
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This interesting to find processes that are managing network data:
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```bash
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dtrace -n 'syscall::recv*:entry { printf("-> %s (pid=%d)", execname, pid); }' >> recv.log
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#wait some time
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sort -u recv.log > procs.txt
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cat procs.txt
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```
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Or use `netstat` or `lsof`
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### More Fuzzing MacOS Info
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* [https://github.com/bnagy/slides/blob/master/OSXScale.pdf](https://github.com/bnagy/slides/blob/master/OSXScale.pdf)
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* [https://github.com/bnagy/francis/tree/master/exploitaben](https://github.com/bnagy/francis/tree/master/exploitaben)
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* [https://github.com/ant4g0nist/crashwrangler](https://github.com/ant4g0nist/crashwrangler)
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## References
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* [**OS X Incident Response: Scripting and Analysis**](https://www.amazon.com/OS-Incident-Response-Scripting-Analysis-ebook/dp/B01FHOHHVS)
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* [**https://www.youtube.com/watch?v=T5xfL9tEg44**](https://www.youtube.com/watch?v=T5xfL9tEg44)
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* [**https://taomm.org/vol1/analysis.html**](https://taomm.org/vol1/analysis.html)
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