hacktricks/ios-pentesting

iOS Pentesting

iOS Basics

{% page-ref page="ios-basics.md" %}

Testing Environment

In this page you can find information about the iOS simulator, emulators and jailbreaking:

{% page-ref page="ios-testing-environment.md" %}

Initial Analysis

Listing Installed Apps

When targeting apps that are installed on the device, you'll first have to figure out the correct bundle identifier of the application you want to analyze. You can use frida-ps -Uai to get all apps `-a` currently installed `-i` on the connected USB device `-U`:

$ frida-ps -Uai
 PID  Name                 Identifier
----  -------------------  -----------------------------------------
6847  Calendar             com.apple.mobilecal
6815  Mail                 com.apple.mobilemail
   -  App Store            com.apple.AppStore
   -  Apple Store          com.apple.store.Jolly
   -  Calculator           com.apple.calculator
   -  Camera               com.apple.camera
   -  iGoat-Swift          OWASP.iGoat-Swift

IPA Structure

.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.
• _CodeSignature/ contains a plist file with a signature over all files in the bundle.
• Assets.car: Another zipped archive that contains assets icons.
• Frameworks/ contains the app native libraries as .dylib or .framework files.
• PlugIns/ may contain app extensions as .appex files not present in the example.
• Core Data: 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: 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.

Info.plist

The information property list or Info.plist is the main source of information for an iOS app. It consists of a structured file containing key-value pairs describing essential configuration information about the app. Actually, all bundled executables app extensions, frameworks and apps are expected to have an Info.plist file. You can find all possible keys in the Apple Developer Documentation.

The file might be formatted in XML or binary (bplist). You can convert it to XML format with one simple command:

• On macOS with plutil, which is a tool that comes natively with macOS 10.2 and above versions no official online documentation is currently available:

  $ plutil -convert xml1 Info.plist
  

• On Linux:

  $ apt install libplist-utils
  $ plistutil -i Info.plist -o Info_xml.plist
  

Here's a non-exhaustive list of some info and the corresponding keywords that you can easily search for in the Info.plist file by just inspecting the file or by using grep -i <keyword> Info.plist:

• App permissions Purpose Strings: UsageDescription
• Custom URL schemes: CFBundleURLTypes
• Exported/imported custom document types: UTExportedTypeDeclarations / UTImportedTypeDeclarations
• App Transport Security ATS configuration: NSAppTransportSecurity

Please refer to the mentioned chapters to learn more about how to test each of these points.

Data Paths

On iOS, system applications can be found in the /Applications directory while user-installed apps are available under /private/var/containers/. However, finding the right folder just by navigating the file system is not a trivial task as every app gets a random 128-bit UUID Universal Unique Identifier assigned for its directory names.

In order to easily obtain the installation directory information for user-installed apps you can use objection's command env will also show you all the directory information of the app:

OWASP.iGoat-Swift on (iPhone: 11.1.2) [usb] # env

Name               Path
-----------------  -------------------------------------------------------------------------------------------
BundlePath         /var/containers/Bundle/Application/3ADAF47D-A734-49FA-B274-FBCA66589E67/iGoat-Swift.app
CachesDirectory    /var/mobile/Containers/Data/Application/8C8E7EB0-BC9B-435B-8EF8-8F5560EB0693/Library/Caches
DocumentDirectory  /var/mobile/Containers/Data/Application/8C8E7EB0-BC9B-435B-8EF8-8F5560EB0693/Documents
LibraryDirectory   /var/mobile/Containers/Data/Application/8C8E7EB0-BC9B-435B-8EF8-8F5560EB0693/Library

As you can see, apps have two main locations:

• The Bundle directory `/var/containers/Bundle/Application/3ADAF47D-A734-49FA-B274-FBCA66589E67/`.
• The Data directory `/var/mobile/Containers/Data/Application/8C8E7EB0-BC9B-435B-8EF8-8F5560EB0693/`.

These folders contain information that must be examined closely during application security assessments for example when analyzing the stored data for sensitive data.

Bundle directory:

• AppName.app
  • This is the Application Bundle as seen before in the IPA, it contains essential application data, static content as well as the application's compiled binary.
  • This directory is visible to users, but users can't write to it.
  • Content in this directory is not backed up.
  • The contents of this folder are used to validate the code signature.

Data directory:

• Documents/
  • Contains all the user-generated data. The application end user initiates the creation of this data.
  • Visible to users and users can write to it.
  • Content in this directory is backed up.
  • The app can disable paths by setting NSURLIsExcludedFromBackupKey.
• Library/
  • Contains all files that aren't user-specific, such as caches, preferences, cookies, and property list plist configuration files.
  • iOS apps usually use the Application Support and Caches subdirectories, but the app can create custom subdirectories.
• Library/Caches/
  • Contains semi-persistent cached files.
  • Invisible to users and users can't write to it.
  • Content in this directory is not backed up.
  • The OS may delete this directory's files automatically when the app is not running and storage space is running low.
• Library/Application Support/
  • Contains persistent files necessary for running the app.
  • Invisible to users and users can't write to it.
  • Content in this directory is backed up.
  • The app can disable paths by setting NSURLIsExcludedFromBackupKey.
• Library/Preferences/
  • Used for storing properties that can persist even after an application is restarted.
  • Information is saved, unencrypted, inside the application sandbox in a plist file called [BUNDLE_ID].plist.
  • All the key/value pairs stored using NSUserDefaults can be found in this file.
• tmp/
  • Use this directory to write temporary files that do not need to persist between app launches.
  • Contains non-persistent cached files.
  • Invisible to users.
  • Content in this directory is not backed up.
  • The OS may delete this directory's files automatically when the app is not running and storage space is running low.

Let's take a closer look at iGoat-Swift's Application Bundle .app directory inside the Bundle directory `/var/containers/Bundle/Application/3ADAF47D-A734-49FA-B274-FBCA66589E67/iGoat-Swift.app`:

OWASP.iGoat-Swift on (iPhone: 11.1.2) [usb] # ls
NSFileType      Perms  NSFileProtection    ...  Name
------------  -------  ------------------  ...  --------------------------------------
Regular           420  None                ...  rutger.html
Regular           420  None                ...  mansi.html
Regular           420  None                ...  splash.html
Regular           420  None                ...  about.html

Regular           420  None                ...  LICENSE.txt
Regular           420  None                ...  Sentinel.txt
Regular           420  None                ...  README.txt

Binary Reversing

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:

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:

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

Disassembling the binary

Disassemble the text section:

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:

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:

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 and IDA.

Data Storage

To learn about how iOS stores data in the device read this page:

{% page-ref page="ios-basics.md" %}

{% hint style="warning" %} The following places to store information should be checked right after installing the application, after checking all the functionalities of the application and even after login out from one user and login into a different one.
The goal is to find unprotected sensitive information of the application passwords, tokens, of the current user and of previously logged users. {% endhint %}

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.

To find all the plist of used by the application you can access to /private/var/mobile/Containers/Data/Application/{APPID} and run:

find ./ -name "*.plist"

The file might be formatted in XML or binary (bplist). You can convert it to XML format with one simple command:

• On macOS with plutil, which is a tool that comes natively with macOS 10.2 and above versions no official online documentation is currently available:

  $ plutil -convert xml1 Info.plist
  

• On Linux:

  $ apt install libplist-utils
  $ plistutil -i Info.plist -o Info_xml.plist
  

NSUserDefaults

The NSUserDefaults class provides a programmatic interface for interacting with the default system. The default system allows an application to customize its behaviour according to user preferences. Data saved by NSUserDefaults can be viewed in the application bundle. This class stores data in a plist file, but it's meant to be used with small amounts of data.

You can locate this plist file inside the application's folder: /private/var/mobile/Containers/Data/Application/{APPID}/Library/Preferences/*.plist

Search sensitive information inside the file.

Core Data

Core Data is a framework for managing the model layer of objects in your application. Core Data can use SQLite as its persistent store, but the framework itself is not a database.
CoreData does not encrypt it's data by default. However, an additional encryption layer can be added to CoreData. See the GitHub Repo for more details.

You can find the SQLite Core Data information of an application in the path /private/var/mobile/Containers/Data/Application/{APPID}/Library/Application Support

If you can open the SQLite and access sensitive information, then you found a miss-configuration.

{% code title="Code from iGoat" %}

-(void)storeDetails {
    AppDelegate * appDelegate = (AppDelegate *)(UIApplication.sharedApplication.delegate);
    
    NSManagedObjectContext *context =[appDelegate managedObjectContext];
    
    User *user = [self fetchUser];
    if (user) {
        return;
    }
    user = [NSEntityDescription insertNewObjectForEntityForName:@"User"
                                                  inManagedObjectContext:context];
    user.email = CoreDataEmail;
    user.password = CoreDataPassword;
    NSError *error;
    if (![context save:&error]) {
        NSLog(@"Error in saving data: %@", [error localizedDescription]);
        
    }else{
        NSLog(@"data stored in core data");
    }
}

{% endcode %}

SQLite Databases

It's common for applications to create their own sqlite database. They may be storing sensitive data on them and leaving it unencrypted. Therefore, it's always interesting to check every database inside the applications directory. Therefore go to the application directory where the data is saved `/private/var/mobile/Containers/Data/Application/{APPID}`

find ./ -name "*.sqlite" -or -name "*.db"

YapDatabase

YapDatabase is a key/value store built on top of SQLite.
As the Yap databases are sqlite databases you can find them using the purposed commend in the previous section.

Firebase Real-Time Databases

It can be leveraged by application developers to store and sync data with a NoSQL cloud-hosted database. The data is stored as JSON and is synchronized in real-time to every connected client and also remains available even when the application goes offline.

You can find how to check for misconfigured Firebase databases here:

{% page-ref page="../pentesting/pentesting-web/buckets/firebase-database.md" %}

Realm databases

Realm Objective-C and Realm Swift aren't supplied by Apple, but they are still worth noting. They store everything unencrypted, unless the configuration has encryption enabled.

You can find this databases in /private/var/mobile/Containers/Data/Application/{APPID}

iPhone:/private/var/mobile/Containers/Data/Application/A079DF84-726C-4AEA-A194-805B97B3684A/Documents root# ls
default.realm  default.realm.lock  default.realm.management/  default.realm.note|

You can use the tool Realm Studio to open this database files.

The following example demonstrates how to use encryption with a Realm database:

// Open the encrypted Realm file where getKey() is a method to obtain a key from the Keychain or a server
let config = Realm.Configuration(encryptionKey: getKey())
do {
  let realm = try Realm(configuration: config)
  // Use the Realm as normal
} catch let error as NSError {
  // If the encryption key is wrong, `error` will say that it's an invalid database
  fatalError("Error opening realm: \(error)")
}

Couchbase Lite Databases

Couchbase Lite is a lightweight, embedded, document-oriented NoSQL database engine that can be synced. It compiles natively for iOS and macOS.

Check for possible couchbase databases in /private/var/mobile/Containers/Data/Application/{APPID}/Library/Application Support/

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.
You can also use objection to convert these files to a JSON format and inspect the data.

...itudehacks.DVIAswiftv2.develop on (iPhone: 13.2.3) [usb] # ios cookies get --json
[
    {
        "domain": "highaltitudehacks.com",
        "expiresDate": "2051-09-15 07:46:43 +0000",
        "isHTTPOnly": "false",
        "isSecure": "false",
        "name": "username",
        "path": "/",
        "value": "admin123",
        "version": "0"
    }
]

Cache

By default NSURLSession stores data, such as HTTP requests and responses in the Cache.db database. This database can contain sensitive data, if tokens, usernames or any other sensitive information has been cached. To find the cached information open the data directory of the app `/var/mobile/Containers/Data/Application/<UUID>` and go to /Library/Caches/<Bundle Identifier>. The WebKit cache is also being stored in the Cache.db file. Objection can open and interact with the database with the command sqlite connect Cache.db, as it is a normal SQLite database.

It is recommended to disable Caching this data, as it may contain sensitive information in the request or response. The following list below shows different ways of achieving this:

1. It is recommended to remove Cached responses after logout. This can be done with the provided method by Apple called removeAllCachedResponses You can call this method as follows:

   URLCache.shared.removeAllCachedResponses()

   This method will remove all cached requests and responses from Cache.db file.

2. If you don't need to use the advantage of cookies it would be recommended to just use the .ephemeral configuration property of URLSession, which will disable saving cookies and Caches.

   Apple documentation:

   An ephemeral session configuration object is similar to a default session configuration (see default), except that the corresponding session object doesn’t store caches, credential stores, or any session-related data to disk. Instead, session-related data is stored in RAM. The only time an ephemeral session writes data to disk is when you tell it to write the contents of a URL to a file.

3. Cache can be also disabled by setting the Cache Policy to .notAllowed. It will disable storing Cache in any fashion, either in memory or on disk.

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

Tools like Keychain-Dumper can be used to dump the keychain the dive must be jailbroken.
You can also use ios keychain dump from Objection****

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 > General > Keyboard > 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 > General > Reset > 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.

Logs

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.

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.

Monitoring System Logs

Many apps log informative and potentially sensitive messages to the console log. The log also contains crash reports and other useful information. You can collect console logs through the Xcode Devices window as follows:

1. Launch Xcode.
2. Connect your device to your host computer.
3. Choose Window -> Devices and Simulators.
4. Click on your connected iOS device in the left section of the Devices window.
5. Reproduce the problem.
6. Click on the Open Console button located in the upper right-hand area of the Devices window to view the console logs on a separate window.

You can also connect to the device shell as explained in Accessing the Device Shell, install socat via apt-get and run the following command:

iPhone:~ root# socat - UNIX-CONNECT:/var/run/lockdown/syslog.sock

========================
ASL is here to serve you
> watch
OK

Jun  7 13:42:14 iPhone chmod[9705] <Notice>: MS:Notice: Injecting: (null) [chmod] (1556.00)
Jun  7 13:42:14 iPhone readlink[9706] <Notice>: MS:Notice: Injecting: (null) [readlink] (1556.00)
Jun  7 13:42:14 iPhone rm[9707] <Notice>: MS:Notice: Injecting: (null) [rm] (1556.00)
Jun  7 13:42:14 iPhone touch[9708] <Notice>: MS:Notice: Injecting: (null) [touch] (1556.00)
...

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 is used to invoke an application from an URI.
For example, the URI: myapp://hostname?data=123876123 will invoke the application mydata the one that has **register** the scheme `mydata` to the action related to the hostname hostname sending the parameter data with value 123876123

You can find the schemes registered by an application in the app's Info.plist file searching for CFBundleURLTypes.

However, note that malicious applications can re-register URIs already registered by applications. So, if you are sending sensitive information via URIs myapp://hostname?password=123456 a malicious application can intercept the URI with the sensitive information.

Also, the input of these URIs should be checked and sanitised, as it can be coming from malicious origins trying to exploit SQLInjections, XSS, CSRF, Path Traversals, or other possible vulnerabilities.

Universal Links

Universal links allows to redirect users directly to the app without passing through safari for redirection.
Universal links are unique, so they can't be claimed by other apps because they use standard HTTP(S) links to the website where the owner has uploaded a file to make sure that the website and the app are related.
As these links uses HTTP(S) schemes, when the app isn't installed, safari will open the link redirecting the users to the page. These allows apps to communicate with the app even if it isn't installed.

To create universal links it's needed to create a JSON file called apple-app-site-association with the details. Then this file needs to be hosted in the root directory of your webserver e.g. [https://google.com/apple-app-site-association](https://google.com/apple-app-site-association).
For the pentester this file is very interesting as it discloses paths. It can even be disclosing paths of releases that haven't been published yet.

Third Party SDKs

One problem of 3rd party SDKs is that there is no granular control over the features offered by the SDK. You could sue the SDK and have all features including diagnostic leaks and insecure HTTP connections, or not use it. Also, usually it's no possible for the applications developers to patch a vulnerability on the SDK.
Moreover some SDKs start containing malware once they are very trusted by the community.

You can find the libraries used by an application by running otool against the app and **running** it **against** **each** shared **library** to find more shared libraries used.

Hot Patching

The developers can remotely patch all installations of their app instantly without having to resubmit the application to the App store and wait until it's approved.
For this purpose it's usually use JSPatch.
This is a dangerous mechanism that could be abused by malicious third party SDKs.

Misc

• In /System/Library you can find the frameworks installed in the phone used by system applications
• The applications installed by the user from the App Store are located inside /User/Applications
• And the /User/Library contains data saved by the user level applications
• You can access /User/Library/Notes/notes.sqlite to read the notes saved inside the application.
• Inside the folder of an installed application **`/User/Applications/<APP ID>/`** you can find some interesting files:
  • iTunesArtwork: The icon used by the app
  • iTunesMetadata.plist: Info of the app used in the App Store
  • /Library/*: Contains the preferences and cache. In /Library/Cache/Snapshots/* you can find the snapshot performed to the application before sending it to the background.

Dynamic Analysis

Network Communication

It's important to check that no communication is occurring without encryption and also that the application is correctly validating the TLS certificate of the server.
To check these kind of issues you can use a proxy like Burp:

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

Hostname check

One common issue validating the TLS certificate is to check that the certificate was signed by a trusted CA, but not check if the hostname of the certificate is the hostname being accessed.
In order to check this issue using Burp, after trusting Burp CA in the iPhone, you can create a new certificate with Burp for a different hostname and use it. If the application still works, then, something it's vulnerable.

Certificate Pinning

If an application is correctly using SSL Pinning, then the application will only works if the certificate is the once expected to be. When testing an application this might be a problem as Burp will serve it's own certificate.
In order to bypass this protection inside a jailbroken device, you can install the application SSL Kill Switch ****or install Burp Mobile Assistant****

Automatic Tools

****

References

• https://mobile-security.gitbook.io/mobile-security-testing-guide/ios-testing-guide/0x06b-basic-security-testing#information-gathering