hacktricks/ios-pentesting/README.md

# iOS Pentesting

## Privilege Separation and Sandbox

Applications the user can access run as the **mobile** user while critical system processes run as **root**.  
However, the sandbox allows better control over actions that processes and applications can perform.

For example, even if two processes run as the same user \(mobile\), they are **not allowed to access or modify each other's data**.

Each application is installed under **`private/var/mobile/Applications/{random ID}`**  
Once installed, applications have limited read access to some system areas and functions \(SMS, phone call...\). If an application wants to access a **protected area,** a **pop-up requesting permission** appears.

## Jailbreaking

Apple strictly requires that the code running on the iPhone must be **signed by a certificate issued by Apple**. **Jailbreaking** is the process of actively **circumventing such restrictions** and other security controls put in places by the OS. Therefore, once the device is jailbroken, the **integrity check** which is responsible for checking apps being installed is patched so it is **bypassed**.

{% hint style="info" %}
Unlike Android, **you cannot switch to "Developer Mode"** in iOS to run unsigned/untrusted code on the device.
{% endhint %}

The most important side effect of Jailbreaking is that it **removes any sandboxing put in place by the OS**. Therefore, any **app on the device can read any file** on the filesystem, including other apps files, cookies and keychain.

A jailbroken device allows users to **install unapproved apps** and leverage **more APIs**, which otherwise aren't accessible.

There are 2 types of jailbreaks:

* **Tethered**: Temporary jailbreak that requires the device to be connected to a computer every-time the device needs a restart. The jailbreak is reversed otherwise.
* **Untethered**: Rebooting the device does not reset the jailbreak.

**For regular users it's not recommended to jailbreak the mobile.  
Note also that updating the OS removes the effect of jailbreaking.**

## **Simulator**

All the tools required to build and support an iOS app are **only officially supported on Mac OS**.  
Apple's de facto tool for creating/debugging/instrumenting iOS applications is **Xcode**. It can be used to download other components such as **simulators** and different **SDK** **versions** required to build and **test** your app.  
It's highly recommended to **download** Xcode from the **official app store**. Other versions may be carrying malware.

The simulator files can be found in `/Users/<username>/Library/Developer/CoreSimulator/Devices`

To open the simulator, run Xcode, then press in the _Xcode tab_ --&gt; _Open Developer tools_ --&gt; _Simulator_  
In the following image clicking in "iPod touch \[...\]" you can select other device to test in:

![](../.gitbook/assets/image%20%28459%29.png)

![](../.gitbook/assets/image%20%28460%29.png)

### Applications in the Simulator

Inside `/Users/<username>/Library/Developer/CoreSimulator/Devices` you may find all the **installed simulators**. If you want to access the files of an application created inside one of the emulators it might be difficult to know **in which one the app is installed**. A quick way to **find the correct UID** is to execute the app in the simulator and execute:

```bash
xcrun simctl list | grep Booted
    iPhone 8 (BF5DA4F8-6BBE-4EA0-BA16-7E3AFD16C06C) (Booted)
```

Once you know the UID the apps installed within it can be found in `/Users/<username>/Library/Developer/CoreSimulator/Devices/{UID}/data/Containers/Data/Application`

However, surprisingly you won't find the application here. You need to access `/Users/<username>/Library/Developer/Xcode/DerivedData/{Application}/Build/Products/Debug-iphonesimulator/`

And in this folder you can **find the package of the application.**

## Apple Developer Program

A **provisioning identity** is a collection of public and private keys that are associated an Apple developer account. In order to **sign apps** you need to pay **99$/year** to register in the **Apple Developer Program** to get your provisioning identity. Without this you won't be able to run applications from the source code in a physical device. Another option to do this is to use a **jailbroken device**.

Starting in Xcode 7.2 Apple has provided an option to create a **free iOS development provisioning profile** that allows to write and test your application on a real iPhone. Go to _Xcode_ --&gt; _Preferences_ --&gt; _Accounts_ --&gt; _+_ \(Add new Appli ID you your credentials\) --&gt; _Click on the Apple ID created_ --&gt; _Manage Certificates_ --&gt; _+_ \(Apple Development\) --&gt; _Done_  
Then, in order to run your application in your iPhone you need first to **indicate the iPhone to trust the computer.** Then, you can try to **run the application in the mobile from Xcode,** but and error will appear. So go to _Settings_ --&gt; _General_ --&gt; _Profiles and Device Management_ --&gt; Select the untrusted profile and click "**Trust**".

Note that **applications signed by the same signing certificate can share resources on a secure manner, like keychain items**.

## Objective-C and Swift Basics

**Objecttive-C** has a **dynamic runtime**, so when an Objective-C program is executed in iOS, it calls libraries whose **address are resolved at runtime** by comparing the name of the function sent in the message against a list of all the function names available.

At the beginning, only apps created by Apple run the iPhones, so they had **access to everything** as they were **trusted**. However, when Apple **allowed** **third party applications,** Apple just removed the headers files of the powerful functions to "hide" them to developers. However, developers found that "safe" functions needed a few of these undocumented functions and just creating a **custom header file with the names of the undocumented functions, it was possible to invoke this powerful hidden functions.** Actually, Apple, before allowing an app to be published, check if the app calls any of these prohibited functions.

Then, Swift appeared. As **Swift is statically bound** \(it doesn't resolve the address of the functions in runtime like Objective-C\), it can be checked more easily the calls a Swift program is going to make via static code analysis.

## Obfuscation

Unlike an Android Application, the binary of an iOS app **can only be disassembled** and not decompiled.  
When an application is submitted to the app store, Apple first verifies the app conduct and before releasing it to the app-store, **Apple encrypts the binary using** [**FairPlay**](https://developer.apple.com/streaming/fps/). So the binary download from the app store is encrypted complicating  ting the reverse-engineering tasks.

However, note that there are other **third party software that can be used to obfuscate** the resulting binaries.

### Removing App Store Encryption

In order to run the encrypted binary, the device needs to decrypt it  in memory. Then, it's possible to **dump the decrypted binary from the memory**.

First, check if the binary is compiled with the PIE \(Position Independent Code\) flag:

```bash
otool -Vh Original_App #Check the last word of the last line of this code
Home:
Mach header
      magic  cputype cpusubtype  caps    filetype ncmds sizeofcmds      flags
MH_MAGIC_64   X86_64        ALL  0x00     EXECUTE    47       6080   NOUNDEFS DYLDLINK TWOLEVEL PIE
```

If it's set you can use the script [`change_macho_flags.py`](https://chromium.googlesource.com/chromium/src/+/49.0.2623.110/build/mac/change_mach_o_flags.py) to remove it with python2:

```bash
python change_mach_o_flags.py --no-pie Original_App
otool -Vh Hello_World
Hello_World:
Mach header
      magic  cputype cpusubtype  caps    filetype ncmds sizeofcmds      flags
   MH_MAGIC      ARM         V7  0x00     EXECUTE    22       2356   NOUNDEFS DYLDLINK TWOLEVEL MH_NO_HEAP_EXECUTION
```

Now that the PIE flag isn't set, the OS will load the program at a **fixed starting location** every-time. In order to find this **location** you can use:

```bash
otool -l Original_App | grep -A 3 LC_SEGMENT | grep -A 1 __TEXT
  segname __TEXT
   vmaddr 0x00004000
```

Then, it's necessary to extract the the memory range that needs to be dumped:

```bash
otool -l Original_App | grep -A 4 LC_ENCRYPTION_INFO
          cmd LC_ENCRYPTION_INFO
      cmdsize 20
     cryptoff 16384
    cryptsize 17416192
      cryptid 0
```

The value of **`cryptoff`** indicated the starting address of the encrypted content and the **`cryptsize`** indicates the size of the encrypted content.

So, the `start address` to dump will be `vmaddr + cryptoff` and the `end address` will be the `start address + cryptsize`  
In this case: `start_address = 0x4000 + 0x4000 = 0x8000` __and `end_address = 0x8000 + 0x109c000 = 0x10a4000`

With this information it's just necessary to run the application in the jailbroken device, attach to the process with gdb \(`gdb -p <pid>`\) and dump the memory:

```bash
dump memory dump.bin 0x8000 0x10a4000
```

Congrats! You have decrypted the encrypted section in dump.bin. Now **transfer this dump to your computer and overwrite the encrypted section with the decrypted** one:

```bash
dd bs=1 seek=<starting_address> conv=notrunc if=dump.bin of=Original_App
```

There is one more step to complete. The application is still **indicating** in its metadata that it's **encrypted**, but it **isn't**. Then, when executed, the device will try to decrypt the already decrypted section and it's going to fail.  
However, you can use tools like [**MachOView**](https://sourceforge.net/projects/machoview/) to change this info. Just open the binary and set the **cryptid** to 0:

![](../.gitbook/assets/image%20%28458%29.png)

### Removing App Store Encryption Automatically

You can use tools like [**Clutch**](https://github.com/KJCracks/Clutch) to automatically remove the encryption and an app.

## IPA Reversing

`.ipa` files are **zipped** **packages**, so you can change the extension to `.zip` and **decompress** them. A **complete** **packaged** app ready to be installed is commonly referred to as a **Bundle**.  
After decompressing them you should see `<NAME>.app` , a zipped archive that contains the rest of the resources.

* **Info.plist**: A file that contains some of the application specific configurations.
* **Assets.car**: Another zipped archive that contains assets \(icons\).
* \*\*\*\*[**Core Data**](https://developer.apple.com/documentation/coredata): It is used to save your application’s permanent data for offline use, to cache temporary data, and to add undo functionality to your app on a single device. To sync data across multiple devices in a single iCloud account, Core Data automatically mirrors your schema to a CloudKit container.
* \*\*\*\*[**PkgInfo**](https://developer.apple.com/library/archive/documentation/MacOSX/Conceptual/BPRuntimeConfig/Articles/ConfigApplications.html): The `PkgInfo` file is an alternate way to specify the type and creator codes of your application or bundle.
* **en.lproj, fr.proj, Base.lproj**: Are the language packs that contains resources for those specific languages, and a default resource in case a language isn' t supported.

There are multiple ways to define the UI in an iOS application: _storyboard_, _nib_ or _xib_ files.

### Binary

Inside the `<application-name>.app` folder you will find a binary file called `<application-name>`. This is the file that will be **executed**. You can perform a basic inspection of the binary with the tool **`otool`**:

```bash
otool -Vh DVIA-v2 #Check some compilation attributes
      magic  cputype cpusubtype  caps    filetype ncmds sizeofcmds      flags
MH_MAGIC_64    ARM64        ALL  0x00     EXECUTE    65       7112   NOUNDEFS DYLDLINK TWOLEVEL WEAK_DEFINES BINDS_TO_WEAK PIE

otool -L DVIA-v2 #Get third party libraries
DVIA-v2:
	/usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 400.9.1)
	/usr/lib/libsqlite3.dylib (compatibility version 9.0.0, current version 274.6.0)
	/usr/lib/libz.1.dylib (compatibility version 1.0.0, current version 1.2.11)
	@rpath/Bolts.framework/Bolts (compatibility version 1.0.0, current version 1.0.0)
[...]
```

#### Check if the app is encrypted

See if there is any output for:

```bash
otool -l <app-binary> | grep -A 4 LC_ENCRYPTION_INFO
```

#### Disassembling the binary

Disassemble the text section:

```bash
otool -tV DVIA-v2
DVIA-v2:
(__TEXT,__text) section
+[DDLog initialize]:
0000000100004ab8	sub	sp, sp, #0x60
0000000100004abc	stp	x29, x30, [sp, #0x50]   ; Latency: 6
0000000100004ac0	add	x29, sp, #0x50
0000000100004ac4	sub	x8, x29, #0x10
0000000100004ac8	mov	x9, #0x0
0000000100004acc	adrp	x10, 1098 ; 0x10044e000
0000000100004ad0	add	x10, x10, #0x268
```

To print the **Objective-C segment** of the sample application one can use:

```bash
otool -oV DVIA-v2
DVIA-v2:
Contents of (__DATA,__objc_classlist) section
00000001003dd5b8 0x1004423d0 _OBJC_CLASS_$_DDLog
    isa        0x1004423a8 _OBJC_METACLASS_$_DDLog
    superclass 0x0 _OBJC_CLASS_$_NSObject
    cache      0x0 __objc_empty_cache
    vtable     0x0
    data       0x1003de748
        flags          0x80
        instanceStart  8
```

In order to obtain a more compact Objective-C code you can use [**class-dump**](http://stevenygard.com/projects/class-dump/):

```bash
class-dump some-app
//
//     Generated by class-dump 3.5 (64 bit).
//
//     class-dump is Copyright (C) 1997-1998, 2000-2001, 2004-2013 by Steve Nygard.
//

#pragma mark Named Structures

struct CGPoint {
    double _field1;
    double _field2;
};

struct CGRect {
    struct CGPoint _field1;
    struct CGSize _field2;
};

struct CGSize {
    double _field1;
    double _field2;
};
```

However, the best options to disassemble the binary are: [**Hopper**](https://www.hopperapp.com/download.html?) and [**IDA**](https://www.hex-rays.com/products/ida/support/download_freeware/).

## Testing

### Storage Access

You can use [**iFunBox**](https://www.i-funbox.com/en/page-download.html) to access the all the storage inside an application sandbox/folder

{% hint style="info" %}
Starting in iOS version 8.4, Apple has **restricted the third-party managers to access to the application sandbox**, so tools like iFunbox and iExplorer no longer display/retrieve files from apps installed on the device if the device isn't jailbroken.
{% endhint %}

### Burp Proxy Configuration

{% page-ref page="burp-configuration-for-ios.md" %}

### Snapshots

Whenever you press the home button, iOS **takes a snapshot of the current screen** to be able to do the transition to the application on a much smoother way. However, if **sensitive** **data** is present in the current screen, it will be **saved** in the **image** \(which **persists** **across** **reboots**\). These are the snapshots that you can also access double tapping the home screen to switch between apps.

Unless the iPhone is jailbroken, the **attacker** needs to have **access** to the **device** **unblocked** to see these screenshots. By default the last snapshot is stored in the application's sandbox in `/Library/Caches/Snapshots/` folder \(the trusted computers can' t access the filesystem from iOX 7.0\).

Once way to prevent this bad behaviour is to put a blank screen or remove the sensitive data before taking the snapshot using the `ApplicationDidEnterBackground()` function.

### Keychain

A keychain is an **encrypted** **container** where every application can **store** **sensitive** pieces of **information** and only the same app \(or authorised apps\) can retrieve the contents.  
The iOS **generated its own password for the keychain** and **stores** an **encrypted** version of this key in the device. This password is encrypted with AES using an AES key created by a **PBKDF2** function of the **user's passcode + salt** \(the 256 bit device **UID** **only** **accessible** to the secure **enclave chipset** on the device\). Due to the use of this device UID as salt, a device won't be able to decrypt the keychain of a different device even knowing the users passcode.

The only ways to try to BF this password is dumping the encrypted key and BF the passcode + salt \(the **pbkdf2** function uses **at least 10000 iteration**s\). Or trying to **BF inside the device** to avoids BFing the salt, however, secure enclave ensures there is at least a **5s delay between 2 failed password attempts**.

When a backup process is initiated the keychain **data backed up remains encrypted and the keychain password isn't included in the backup**.

**In a jailbroken device the keychain isn't protected.**

#### **Attribute types for items saved in the keychain:**

* **kSecAttrAccessibleAlways:** These items will not be stored securely in the keychain and are available at all times, even when the device is blocked
* **kSecAttrAccessibleAfterFirstUnlock**: Items secure in the keychain until the device is first unlocked after a reboot. Then, the items are accessible even when the device is blocked.
* **kSecAttrAccessibleWhenUnlocked**: Items are secure at rest and when the device is locked. The items are only accessible when the device is unlocked.
* **kSecAttrAccessibleWhenPasscodeSetThisDeviceOnly**: Like **kSecAttrAccessibleWhenUnlocked** but you a passcode must be set in the device. If the passcode is unset, these secrets are deleted from the device.

You can also select the "_**ThisDeviceOnly**_" on keychain objects to ensure that even the encrypted keychains objects **never leave the device during backups**.

The iPhone uses the **passcode introduced by the user unlocking the device to decrypt the secrets in the keychain**.

iOS uses the _**AppIdentifierPrefix**_ \(Team ID\) and the _**BundleIdentifier**_ \(provided by the dev\) to enforce **access control oven keychain items**. Then, the same team **can** **configure** **2 apps to share keychain items**.

Tools like [**Keychain-Dumper**](https://github.com/ptoomey3/Keychain-Dumper) can be used to dump the keychain \(the dive must be jailbroken\).

{% hint style="info" %}
In **iOS earlier than 10.3**, when an application is deleted from the device, iOS **doesn't clean up the keychain**. So on these devices you can **find secrets of deleted apps**.
{% endhint %}

### Cookies

iOS store the cookies of the apps in the **`Library/Cookies/cookies.binarycookies`** inside each apps folder. However, developers sometimes decide to save them in the **keychain** as the mentioned **cookie file can be accessed in backups**.

To inspect the cookies file you can use [**this python script**](https://github.com/mdegrazia/Safari-Binary-Cookie-Parser).

### Plist

**plist** files are structured XML files that **contains key-value pairs**. It's a way to store persistent data, so sometimes you may find **sensitive information in these files**. It's recommended to check these files after installing the app and after using intensively it to see if new data is written.

The most common way to persist data in plist files is through the usage of **NSUserDefaults**. This plist file is saved inside the app sandbox in **`Library/Preferences/<appBundleID>.plist`**

This data cannot be longer accessed directly via a trusted computer, but can be accessed performing a **backup**.

### Custom Keyboards

From iOS 8.0 Apple allows to install custom extensions for iOS like custom keyboards.  
The installed keyboards can be managed via **Settings** &gt; **General** &gt; **Keyboard** &gt; **Keyboards**  
Custom keyboards can be used to **sniff** the **keystrokes** and send them to the attacker server. However, note that **custom keyboards requiring  networking connectivity will be notified to the user.**  
Also, the **user can switch to a different** \(more trusted\) **keyboard** for introducing the credentials.

Moreover, **applications can prevent its users from using custom keyboards** within the app \(or at least for sensitive parts of the app\).

Note that because of auto-correct and auto-suggestions, the default iOS keyboard will capture and store each non-standard word word in a cache file if the attribute **securetTextEntry** is not set to **true** or if **autoCorrectionType** is not set to **UITextAutoCorrectionTypeNo.**

By default the keyboards store this cache inside the applications sandbox in `Library/Keyboard/{locale}-dynamic-text.dat` file. However, it might be saving the date elsewhere.  
It's possible to reset the cache in _**Settings**_ &gt; _**General**_ &gt; _**Reset**_ &gt; _**Reset Keyboard Dictionary**_

**Therefore, check always these files and search for possible sensitive information.  
Intercepting the network traffic is another way to check if the custom keyboard is sending keystroked to a remote server.**

### **Log Files**

The most common ways to debug code is using logging, and the application **may print sensitive information inside the logs**.  
In iOS version 6 and below, logs were world readable \(a malicious app could read logs from other apps and extract sensitive information from there\). **Nowadays, apps can only access their own logs**.

However, an **attacker** with **physical** **access** to an **unlocked** device can connect it  to a computer and **read the logs** \(note that the logs written to disk by an app aren't removed if the app ins uninstalled\).

To inspect the application logs, connect the iPhone to your computer and open _**Xcode**_ &gt; _**Devices**_ &gt; _**{Your device}**_ and you should see the live logs in the console.

It's recommended to **navigate through all the screens** of the app and **interact** with **every** UI element and **functionality** of and provide input text in all text fields and **review the logs** looking for **sensitive** **information** exposed.

### Clipboard

Some applications may save sensitive information inside the clipboard, which is dangerous because then a different application may sniff the clipboard and steal the data. 

Fortunately, apps signed by the same certificate can create **private** **UIPasteboards**. This way, unlike the global Pasteboard, only **selected** **applications** can share and view the content of the **private** **pasteboard**.

Then, it's important to **check that sensitive information isn't being saved inside the global pasteboard**.  
It's also important to check that an **application isn't using the global pasteboard data to perform actions**, as malicious application could tamper this data.

An **application can also prevent its users to copy sensitive data to the clipboard** \(which is recommended\).

### Custom URI Handlers / Deeplinks / Custom Schemes

A custom URI handler can