iOS Internals and Security Testing
1.0.0
As a conformant UNIX system, OS X works with the well-known directories that are standard on all UNIX flavors:
OS X adds its own special directories to the UNIX tree, under the system root:
From the file system perspective, iOS is very similar to OS X, with the following differences:
Files with the .ipa extension can be uncompressed by changing the extension to .zip and unzipping.
/iTunesArtwork
/iTunesArtwork@2x
/iTunesMetadata.plist
/WatchKitSupport/WK
/META-INF
/Payload/
/Payload/<Application>.app/
/Payload/<Application>.app/<Application> ← Apple FairPlay DRM Encrypted Executable
/Payload/<Application>.app/Info.plist A file that contains some of the application specific configurations
/Payload/<Application>.app/_CodeSignature/ Contains a plist file with a signature over all files in the bundle
/Payload/<Application>.app/Assets.car Another zipped archive that contains assets (icons)
/Payload/<Application>.app/Frameworks/ Contains the app native libraries as .dylib or .framework files
/Payload/<Application>.app/PlugIns/ May contain app extensions as .appex files
/Payload/<Application>.app/Core Data It is used to save permanent data for offline use and sync across iCloud devices
/Payload/<Application>.app/PkgInfo An alternate way to specify the type and creator codes of your application or bundle
/Payload/<Application>.app/en.lproj, etc Language packs that contains resources for those specific languages
/var/containers/Bundle/Application/<UUID> Bundle directory; tampering invalidates signature
/var/mobile/Containers/Data/<UUID> Application runtime data
/var/mobile/Containers/Data/<UUID>/Documents/ Contains all the user-generated data
/var/mobile/Containers/Data/<UUID>/Library/ Contains all files that aren't user-specific – caches, preferences, cookies, plist files
/var/mobile/Containers/Data/<UUID>/Library/Caches/
Contains semi-persistent cached files
/var/mobile/Containers/Data/<UUID>/Library/Application Support/
Contains persistent files necessary for running the app
/var/mobile/Containers/Data/<UUID>/Library/Preferences/<bundle id>.plist
Properties that can persist after an application is restarted. Contains NSUserDefaults
/var/mobile/Containers/Data/<UUID>/tmp/ Temporary files that do not need to persist between app launches
plist files are structured XML files that contains key-value pairs supporting basic object types, like dictionaries, lists, numbers and strings. Usually the top level object is a dictionary. plist can be binary or xml or json file.
| Abstract type | XML element | Cocoa class | Core Foundation type |
|---|---|---|---|
| array | <array> |
NSArray |
CFArray (CFArrayRef) |
| dictionary | <dict> |
NSDictionary |
CFDictionary (CFDictionaryRef) |
| string | <string> |
NSString |
CFString (CFStringRef) |
| data | <data> |
NSData |
CFData (CFDataRef) |
| date | <date> |
NSDate |
CFDate (CFDateRef) |
| number - integer | <integer> |
NSNumber (intValue) |
CFNumber (CFNumberRef, integer value) |
| number - floating point | <real> |
NSNumber (floatValue) |
CFNumber (CFNumberRef, floating-point value) |
| Boolean | <true/> or <false/> |
NSNumber (boolValue == YES or boolValue == NO) |
CFBoolean (CFBooleanRef ; kCFBooleanTrue or kCFBooleanFalse) |
A standard Info.plist contains the following entries:
plutil -convert xml1 binary_file.plist
plutil -convert xml1 data_file.json -o data_file.plist
https://docs.python.org/3/library/plistlib.html
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 /var/mobile/Applications/<UUID>. UUID is random.
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.
App developers can leverage the iOS Data Protection APIs to implement fine-grained access control for user data stored in flash memory. The APIs are built on top of the Secure Enclave Processor (SEP). The SEP is a coprocessor that provides cryptographic operations for data protection and key management. A device-specific hardware key-the device UID (Unique ID)-is embedded in the secure enclave, ensuring the integrity of data protection even when the operating system kernel is compromised.
When a file is created on the disk, a new 256-bit AES key is generated with the help of secure enclave's hardware based random number generator. The content of the file is then encrypted with the generated key. And then, this key is saved encrypted with a class key along with the class ID, with both data encrypted by the system's key, inside the metadata of the file.
For decrypting the file, the metadata is decrypted using the system's key. Then using the class ID the class key is retrieved to decrypt the per-file key and decrypt the file.
Files can be assigned to one of four different protection classes, which are explained in more detail in the iOS Security Guide.
Each app has a unique home directory and is sandboxed, so that they cannot access protected system resources or files stored by the system or by other apps. These restrictions are implemented via sandbox policies (aka. profiles), which are enforced by the Trusted BSD (MAC) Mandatory Access Control Framework via a kernel extension.
Some capabilities/permissions can be configured by the app's developers (e.g. Data Protection or Keychain Sharing) and will directly take effect after the installation. However, for others, the user will be explicitly asked the first time the app attempts to access a protected resource.
Purpose strings or usage description strings are custom texts that are offered to users in the system's permission request alert when requesting permission to access protected data or resources.
If having the original source code, you can verify the permissions included in the Info.plist file:
Info.plist file in the default editor and search for the keys starting with "Privacy -".You may switch the view to display the raw values by right-clicking and selecting "Show Raw Keys/Values" (this way for example "Privacy - Location When In Use Usage Description" will turn into NSLocationWhenInUseUsageDescription).
If only having the IPA:
Info.plist is located in Payload/<appname>.app/Info.plist.plutil -convert xml1 Info.plist) as explained in the chapter "iOS Basic Security Testing", section "The Info.plist File".UsageDescription:<plist version="1.0">
<dict>
<key>NSLocationWhenInUseUsageDescription</key>
<string>Your location is used to provide turn-by-turn directions to your destination.</string>
Device capabilities are used by the App Store to ensure that only compatible devices are listed and therefore are allowed to download the app. They are specified in the Info.plist file of the app under the [UIRequiredDeviceCapabilities](https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/iPhoneOSKeys.html#//apple_ref/doc/plist/info/UIRequiredDeviceCapabilities) key.
<key>UIRequiredDeviceCapabilities</key>
<array>
<string>armv7</string>
</array>
Typically you'll find the armv7 capability, meaning that the app is compiled only for the armv7 instruction set, or if it’s a 32/64-bit universal app.
For example, an app might be completely dependent on NFC to work (e.g. a "NFC Tag Reader" app). According to the archived iOS Device Compatibility Reference, NFC is only available starting on the iPhone 7 (and iOS 11). A developer might want to exclude all incompatible devices by setting the nfc device capability.
Entitlements are key value pairs that are signed in to an app and allow authentication beyond runtime factors, like UNIX user ID. Since entitlements are digitally signed, they can’t be changed. Entitlements are used extensively by system apps and daemons to perform specific privileged operations that would otherwise require the process to run as root. This greatly reduces the potential for privilege escalation by a compromised system app or daemon.
For example, if you want to set the "Default Data Protection" capability, you would need to go to the Capabilities tab in Xcode and enable Data Protection. This is directly written by Xcode to the <appname>.entitlements file as the com.apple.developer.default-data-protection entitlement with default value NSFileProtectionComplete. In the IPA we might find this in the embedded.mobileprovision as:
<key>Entitlements</key>
<dict>
...
<key>com.apple.developer.default-data-protection</key>
<string>NSFileProtectionComplete</string>
</dict>
For other capabilities such as HealthKit, the user has to be asked for permission, therefore it is not enough to add the entitlements, special keys and strings have to be added to the Info.plist file of the app.
The Secure Enclave is part of the A7 and newer SoCs used for data protection, Touch ID and Face ID. The purpose of the Secure Enclave is to handle keys and other info such as biometrics that is sensitive enough to not be handled by the Application Processor. It is isolated with a hardware filter so the AP cannot access it. It shares RAM with the AP, but its portion of the RAM — TZ0 is encrypted. The secure enclave itself is a flashable 4MB AKF processor core called the secure enclave processor (SEP). The technology used is similar to ARM's TrustZone/SecurCore but contains proprietary code for Apple KF cores in general and SEP specifically.
The SoC in each device have an AES coprocessor with the GID Key and UID Key built in.
The device’s unique ID (UID) and a device group ID (GID) are AES 256-bit keys fused (UID) or compiled (GID) into the application processor during manufacturing. No software or firmware can read them directly; they can see only the results of encryption or decryption operations performed using them. The UID is unique to each device and is not recorded by Apple or any of its suppliers. The GID is common to all processors in a class of devices and is used as an additional level of protection when delivering system software during installation and restore. Integrating these keys into the silicon helps prevent them from being tampered with or bypassed, or accessed outside the AES engine.
The GID key (Group ID key) is a 256-bit AES key shared by all devices with the same application processor. The GID key is part of how iOS encrypts software on the device. This is one component of the iOS security system, which also includes SHSH signatures. This key is different on each Apple SoC model.
The GID Key has so far not been extracted from any device, so the only way to use it is by going through the AES engine itself.
But
GID can be obtained through the expensive Cold Boot Attack procedure (https://en.m.wikipedia.org/wiki/Cold_boot_attack) and the next no less expensive procedure of scanning the SoC with an electron-beam lithographer Raith CHIPSCANNER (https://minateh.ru/equipment/technological/e-beam-lithography/). Such experiment is unjustifiably expensive and complex, so it never occurred to anyone to try to implement it except for the private laboratory Cellebrite. Cellebrite does not share its research.
The UID key (device's Unique ID key) is an AES 256-bit hardware key, unique to each iPhone.
Some derived keys are computed by the IOAESAccelerator kernel service at boot. These keys are generated by encrypting static values either with the UID key (0x7D0 identifier) or the GID key (0x3E8 identifier).
Key 0x835 – Generated by encrypting 0x01010101010101010101010101010101 with the UID-key. Used for data protection.
Key 0x836 – Generated by encrypting 0x00E5A0E6526FAE66C5C1C6D4F16D6180 with the UID-key. This is computed by the kernel during a restore, but is zeroed out during a normal boot. It is also computed by the Secure Bootloader, and its only known use is to decrypt LLB in NOR. Like 0x835, it is different for each device.
Key 0x837 – Generated by encrypting 0x345A2D6C5050D058780DA431F0710E15 with the S5L8900 GID Key, resulting in 0x188458A6D15034DFE386F23B61D43774. It is used as the encryption key for IMG2 files. With the introduction of IMG3 in iPhone OS 2.0, KBAGs are now used instead of the 0x837 key. Because iPhone OS versions 1.x were used only on the iPhone and iPod touch (both use the S5L8900) the encrypted values for other processors don't matter.
Key 0x838 – Generated by encrypting 0x8C8318A27D7F030717D2B8FC5514F8E1 with the UID-key. Another UID-AES-key-based key, it is used to encrypt everything but LLB in the NOR (iBoot, DeviceTree, pictures).
Key 0x899 – Generated by encrypting 0xD1E8FCB53937BF8DEFC74CD1D0F1D4B0 with the UID-key. Usage unknown.
Key 0x89A – Generated by encrypting 0xDB1F5B33606C5F1C1934AA66589C0661 with the UID-key, getting a device-specific key. Used on A4 devices. It is used to encrypt the SHSH blobs on the device.
Key 0x89B – Generated by encrypting 0x183E99676BB03C546FA468F51C0CBD49 with the UID-key. It is used to encrypt the data partition key.
Key 0x8A3 – Generated by encrypting 0x568241656551e0cdf56ff84cc11a79ef with the UID-key (using AES-256-CBC). It is used during software upgrades on A12 and later to encrypt the "generator" value (using AES-128-CBC) before hashing it to become the nonce.
More info:
https://css.csail.mit.edu/6.858/2020/readings/ios-security-may19.pdf
https://www.securitylab.ru/contest/428454.php
https://www.securitylab.ru/contest/429973.php
Objective-C module files have the “.m” extension (if a mix of C++ and Objective-C was used, the “.mm” extension). Header files - “.h”. All objects of classes created in Objective-C must be allocated in heap. Therefore, the id type, which is a pointer to an object of any class (in fact, void *), acquires special significance. A null pointer is referred to as the constant nil. Thus, a pointer to any class can be cast to the id type. A problem arises: how to find out which class the object hiding under id belongs to? This is done thanks to the isa invariant, which is present in any object of a class that inherits a special base class NSObject (the NS prefix stands for NeXT Step). The isa invariant is of the reserved type Class. An object of this type allows you to find out the names of its own and the base class, a set of class invariants, as well as the prototypes of all methods that this object has implemented and their addresses (through a local list of selectors). All Objective-C reserved words other than C reserved words begin with an @ symbol (eg @protocol, @selector, @interface). Typically, the names of scoped class invariants (@private, @protected) begin with an underscore. For strings, Cocoa has a very handy NSString class. The string constant of this class is written as @"Hello world", and not as the usual C string constant "Hello world". The BOOL type (essentially unsigned char) can take the constant values YES and NO. All Objective-C-specific reserved words (which differ from the C language and are found in the header file objc/objc.h) are listed below:
@interface Starts declaring a class or category (category is class extension without inheritance)
@end Completes the declarationdefinition of any class, category or protocol
@private Limits the scope of class invariants to class methods (similar to C++)
@protected Stands by default. Limits the scope of class invariants to class methods and methods of derived classes (similar to C++)
@public Removes scoping restrictions (similar to C++)
@try Defines a block with possible exception throwing (similar to C++)
@throw Throws an exception object (similar to C++)
@catch() Handles the exception thrown in the preceding @try block (similar to C++)
@finally Defines the block after the @try block to which control is passed regardless of whether an exception was thrown or not
@class Abbreviated form of class declaration (name only (similar to C++))
@selector(method_name) Returns the compiled selector for the method name method_name
@protocol(protocol_name) Returns an instance of the protocol class named protocol_name
@encode(type_spec) Initializes a character string that will be used to encrypt data of type type_spec
@synchronized() Defines a block of code executed by only one thread at any given point in time
@implementation Starts defining a class or category
@protocol Begins a protocol declaration (analogous to a C++ class consisting of pure virtual functions)
To force an object to execute a method, you need to send it a message named the same as the required method. This message is called a method selector. The syntax for sending is as follows:
[receiver method];
- (void) addObject: (id) otherObject;
If you put a plus sign + at the beginning of a method prototype, then such a method will be considered a class method and, naturally, will not accept the implicit self parameter (this is similar to declaring a static method in C++). And without the isa invariant of the object pointed to by self, the super pointer, of course, will not work either.
Thus, the prototype of any method is declared like this:
- | + (<return type>) mainMethodNamePart
[: (<type of first parameter>) nameOfFirstFormalParameter
[[optionalMethodNamePart]: (<type of second parameter>) secondFormalParameterName] ...
]
For example:
+ (Class)class;
+ (id)alloc;
- (id)init;
- (void)addObject: (id)anObject;
+ (NSString *)stringWithCString: (const char*)aCString usingUncoding: (enum NSStringEncoding)encoding;
- (NSString *)initStringWithFormat: (NSString *)format, ...;
Apple Developer Documentation
https://developer.apple.com/library/archive/documentation/MacOSX/Conceptual/OSX_Technology_Overview/SystemFrameworks/SystemFrameworks.html
https://www.theiphonewiki.com/wiki//System/Library/Frameworks
Frameworks are stored in several locations on the file system:
Additionally, applications may include their own frameworks.
Apple Developer Documentation – Network
Apple Developer Documentation – NetworkExtension
Apple Developer Documentation – NetworkingDriverKit
Most of the apps you might encounter connect to remote endpoints. Even before you perform any dynamic analysis (e.g. traffic capture and analysis), you can obtain some initial inputs or entry points by enumerating the domains to which the application is supposed to communicate to.
Typically these domains will be present as strings within the binary of the application. One can extract domains by retrieving strings with rabin2 -zz <path_to_binary> or in the IDA Pro. The latter option has a clear advantage: it can provide you with context, as you'll be able to see in which context each domain is being used by checking the cross-references.
From here on you can use this information to derive more insights which might be of use later during your analysis, e.g. you could match the domains to the pinned certificates or perform further reconnaissance on domain names to know more about the target environment.
The implementation and verification of secure connections can be an intricate process and there are numerous aspects to consider. For instance, many applications use other protocols apart from HTTP such as XMPP or plain TCP packets, or perform certificate pinning in an attempt to deter MITM attacks.
The Network framework was introduced at The Apple Worldwide Developers Conference (WWDC) in 2018 and is a replacement to the Sockets API. This low-level networking framework provides classes to send and receive data with built in dynamic networking, security and performance support.
TLS 1.3 is enabled by default in the Network framework, if the argument using: .tls is used. It is the preferred option over the legacy Secure Transport framework.
URLSession was built upon the Network framework and utilizes the same transport services. The class also uses TLS 1.3 by default, if the endpoint is HTTPS.
URLSession should be used for HTTP and HTTPS connections, instead of utilizing the Network framework directly. The class natively supports both URL schemes and is optimized for such connections. It requires less boilerplate code, reducing the propensity for errors and ensuring secure connections by default. The Network framework should only be used when there are low-level and/or advanced networking requirements.
The official Apple documentation includes examples of using the Network framework to implement netcat and URLSession to fetch website data into memory.
https://developer.limneos.net/
https://www.theiphonewiki.com/wiki//System/Library/PrivateFrameworks
Latest tool for your device can be found here https://canijailbreak.com
This research is basically written for checkra1ned iPhones 5s through X with iOS 10–15 and can be updated in a long term if a new bootrom pwnage tool will be released. Check it out https://www.theiphonewiki.com/wiki/Bootrom#Bootrom_Exploits
https://repo.chariz.com for example)killall SpringBoardOpen .deb/.ipa file with Filza File Manager and press Install, if you see an error with .deb installation try to find and install all dependencies
Install AppSync Unified from https://cydia.akemi.ai/ repo
https://apt.bingner.com/
https://apt.thebigboss.org/repofiles/cydia/
https://cydia.saurik.com
https://repo.dynastic.co/
https://getdelta.co/
https://cokepokes.github.io/
https://cydia.akemi.ai/
https://nscake.github.io/
https://repo.chariz.com/
https://mrepo.org/
https://rejail.ru/
https://repo.hackyouriphone.org/
https://build.frida.re/ — frida
https://cydia.radare.org/ — radare2
Install on desktop
brew install libimobiledevice ideviceinstaller libirecovery
sudo port install idevicerestore
idevice_id List attached devices or print device name of given device
idevicebackup Create or restore backup for devices (legacy)
idevicebackup2 Create or restore backups for devices running iOS 4 or later
idevicecrashreport Retrieve crash reports from a device
idevicedebug Interact with the debugserver service of a device
idevicedebugserverproxy Proxy a debugserver connection from a device for remote debugging
idevicediagnostics Interact with the diagnostics interface of a device
ideviceenterrecovery Make a device enter recovery mode
ideviceimagemounter Mount disk images on the device
ideviceinfo Show information about a connected device
idevicename Display or set the device name
idevicepair Manage host pairings with devices and usbmuxd
idevicescreenshot Gets a screenshot from the connected device
idevicesetlocation Simulate location on device
idevicesyslog Relay syslog of a connected device
ideviceinstaller --list-apps
ideviceinstaller --install <Application.ipa>
ideviceinstaller --uninstall <bundle id>
idevicedebug -d run <bundle id>
irecovery --shell Allows communication with iBoot/iBSS of iOS device
idevicerestore --latest Restore a new firmware to a device
idevicerestore --erase --latest
Force restoring with erasing all data
inetcat Utility to expose a raw connection to the device
iproxy 2222:22 Bind local port 2222 and forward to 22 of the first USB device
Install on device Apple File Conduit "2"
Use iMazing or iFunBox to access filesystem
Install Filza File Manager
Install OpenSSH on device and run on desktop:
iproxy 2222:22
ssh -p 2222 root@localhost
Default iOS password for root is alpine. Don't change it if you have a bad memory
Install on device NewTerm 2 from https://repo.chariz.com to use local terminal
cd /private/var/containers/Bundle/Application/<guid>/myapp.app
// Contains compiled code, statically linked files, compressed NIB files.
cd /private/var/mobile/Containers/Data/Application/
ls -lrt // Your freshly installed IPA is at the bottom of list
cd [app guid]/Documents/
cd [app guid]/Library/
/private/var/Keychains
TrustStore.sqlite3
keychain-2.db
pinningrules.sqlite3
// Extract IPA (whether App Store encrypted or not)
scp -r -P 2222 root@localhost:/var/containers/Bundle/Application/<app GUID>/hitme.app ~/hitme.app
// Different to SSH, the uppercase P for Port with SCP. Order important.
scp -P 2222 root@localhost:/var/root/overflow.c localfilename.c
// from Jailbroken device to local machine
// Caution:no space after the root@localhost: Otherwise you copy the entire filesystem!
scp -P 2222 root@localhost:/private/var/mobile/Containers/Data/Application/<App GUID>/Library/Caches/Snapshots/com.my.app
// from local machine to remote Jailbroken device
scp -P 2222 hello.txt root@localhost:/var/root/
Install libFLEX and FLEXing from https://nscake.github.io/
Open NewTerm and run killall SpringBoard
Now you can load FLEX inside any application by longpress on the statusbar
Frida is a dynamic binary instrumentation toolkit that allows us to execute scripts in previously locked down software. In a nutshell, Frida lets you inject snippets of JavaScript into native apps on Windows, Mac, Linux, iOS and Android.
Add frida repo to the cydia – https://build.frida.re/
If you don't have Python 3:
brew install pyenv
pyenv install 3.9.0 (or the latest available)
Then install
pip3 install frida-tools
frida-ls-devices List available devices
frida-ps -U List all running processes names and PIDs on a USB device
frida-ps -Uai List all installed apps on a USB device
frida-ps -Ua List all running apps on a USB device
frida-ls-devices List all attached devices
frida-ps -D 0216027d1d6d3a03 Connect Frida to the specific device
frida-discover Tool for discovering internal functions in a process
frida-trace -U Twitter -i "*URL*" Tracing native APIs
frida-trace -U -f com.toyopagroup.picaboo -I "libcommonCrypto*"
Launch the app and trace crypto API calls
frida-trace -U Twitter -m "-[NSURL* *HTTP*]" Tracing Objective-C APIs
frida -U -n Twitter -l inject.js Inject script into process on a USB device via REPL
frida -n cat Connect to cat by name
frida -f foobar Force open foobar
frida -U -f foobar --no-pause Open foobar over usb and force start. starts app running
frida-ps -U | grep -i myapp Get the target app's process ID from USB connected device
frida -U -f foobar --no-pause -q --eval 'console.log("Hi Frida");'
Run script and quit Frida
At this point we have our NativeFunction stored in the play_sound variable. Call it just like a regular function play_sound() and also remember to give the (int) input parameter: play_sound(1007)
Putting it all together:
var address = Module.findExportByName('AudioToolbox', 'AudioServicesPlaySystemSound')
var play_sound = new NativeFunction(address, 'void', ['int'])
play_sound(1007)
You have to get an instance of the object first, either:
var instance = ObjC.classes.ClassName.alloc().init();ObjC.choose, like - if you know there's only one instance already created somewhere on the heap - you can to something like var instance = ObjC.chooseSync(ObjC.classes.ClassName)[0];var instance = ObjC.classes.MySingleton.getInstance().myInterestingInstance();and then call the method on the instance:
instance.setSomething();
or, if the method signature takes an argument, like - setSomething:, you can also pass the argument (just remember to put a _ instead of ObjC's :):
instance.setSomething_(argument);
frida -U "My App" // Attach Frida to app over USB
Process.id
419
Process.getCurrentThreadId()
3843
var b = "hello frida"
console.log(b)
"hello frida"
c = Memory.allocUtf8String(b)
"0x1067ec510"
Memory.readUtf8String(c)
"hello frida"
console.log(c)
0x1067ec510
console.log(c.readUtf8String(5))
hello
console.log(c.readUtf8String(11))
hello frida
ptrToC = new NativePointer(c);
"0x1067ec510"
console.log(ptrToC)
0x1067ec510
console.log(ptrToC.readCString(8))
hello fr
Memory.readUtf8String(ptrToC)
"hello frida"
Objective-C's syntax includes the : and @ characters. These characters were not used in the Frida Javascript API.
// Attach to playground process ID
frida -p $(ps -ax | grep -i -m1 playground |awk '{print $1}')
ObjC.available
true
ObjC.classes.UIDevice.currentDevice().systemVersion().toString()
"11.1"
ObjC.classes.NSBundle.mainBundle().executablePath().UTF8String()
ObjC.classes.UIWindow.keyWindow().toString()
RET: <WKNavigation: 0x106e165c0>
// shows Static Methods and Instance Methods
ObjC.classes.NSString.$ownMethods
ObjC.classes.NSString.$ivars
var myDate = ObjC.classes.NSDate.alloc().init()
console.log(myDate)
2019-04-19 19:03:46 +0000
myDate.timeIntervalSince1970()
1555700626.021566
myDate.description().toString()
"2019-04-19 19:03:46 +0000"
var a = ObjC.classes.NSUUID.alloc().init()
console.log(a)
4645BFD2-94EE-413D-9CE5-8982D41ED6AE
a.UUIDString()
{
"handle": "0x7ff3b2403b20"
}
a.UUIDString().toString()
"4645BFD2-94EE-413D-9CE5-8982D41ED6AE"
var b = ObjC.classes.NSString.stringWithString_("foo");
b.isKindOfClass_(ObjC.classes.NSString)
true
b.isKindOfClass_(ObjC.classes.NSUUID)
false
b.isEqualToString_("foo")
true
b.description().toString()
"foo"
var c = ObjC.classes.NSString.stringWithFormat_('foo ' + 'bar ' + 'lives');
console.log(c)
foo bar lives
var url = ObjC.classes.NSURL.URLWithString_('www.foobar.com')
console.log(url)
www.foobar.com
url.isKindOfClass_(ObjC.classes.NSURL)
true
console.log(url.$class)
NSURL
var b = ObjC.classes.NSString.stringWithString_("foo");
var d = ObjC.classes.NSData
d = b.dataUsingEncoding_(1) // NSASCIIStringEncoding = 1, NSUTF8StringEncoding = 4,
console.log(d)
<666f6f> // This prints the Hex value "666f6f = foo"
d.$className
"NSConcreteMutableData"
var x = d.CKHexString() // Get you the Byte array as a Hex string
console.log(x)
666f6f
x.$className
"NSTaggedPointerString"
var newStr = ObjC.classes.NSString.stringWithUTF8String_[d.bytes]
// demoapp is the iOS app name
myapp=$(ps x | grep -i -m1 demoapp | awk '{print $1}')
frida-trace -i "getfsent*" -p $myapp
// Connect to process with Frida script
frida --codeshare mrmacete/objc-method-observer -p 85974
Process.enumerateModules()
// this will print all loaded Modules
Process.findModuleByName("libboringssl.dylib")
{
"base": "0x1861e2000",
"name": "libboringssl.dylib",
"path": "/usr/lib/libboringssl.dylib",
"size": 712704
}
Process.findModuleByAddress("0x1c1c4645c")
{
"base": "0x1c1c2a000",
"name": "libsystem_kernel.dylib",
"path": "/usr/lib/system/libsystem_kernel.dylib",
"size": 200704
}
DebugSymbol.fromAddress(Module.findExportByName(null, 'strstr'))
{
"address": "0x183cb81e8",
"fileName": "",
"lineNumber": 0,
"moduleName": "libsystem_c.dylib",
"name": "strstr"
}
Module.findExportByName(null, 'strstr')
"0x183cb81e8"
Module.getExportByName(null,'strstr')
"0x183cb81e8"
Process.findModuleByAddress("0x183cb81e8")
{
"base": "0x183cb6000",
"name": "libsystem_c.dylib",
"path": "/usr/lib/system/libsystem_c.dylib",
"size": 516096
}
a = Process.findModuleByName("Reachability")
a.enumerateExports()
....
{
"address": "0x102fab020",
"name": "ReachabilityVersionString",
"type": "variable"
},
{
"address": "0x102fab058",
"name": "ReachabilityVersionNumber",
"type": "variable"
}
....
...
..
frida -U -f funky-chicken.debugger-challenge --no-pause -q --eval 'var x={};Process.enumerateModulesSync().forEach(function(m){x[m.name] = Module.enumerateExportsSync(m.name)});' | grep -B 1 -A 1 task_threads
"address": "0x1c1c4645c",
"name": "task_threads",
"type": "function"
frida -U -f funky-chicken.debugger-challenge --no-pause -q --eval 'var x={};Process.findModuleByAddress("0x1c1c4645c");'
{
"base": "0x1c1c2a000",
"name": "libsystem_kernel.dylib",
"path": "/usr/lib/system/libsystem_kernel.dylib",
"size": 200704
}
[objc_playground]-> var a = ObjC.classes.NSString.stringWithString_("foo");
[objc_playground]-> a.superclass().toString()
"NSString"
[objc_playground]-> a.class().toString()
"NSTaggedPointerString"
// PASTE THIS CODE INTO THE FRIDA INTERFACE...
Interceptor.attach(ObjC.classes.NSTaggedPointerString['- isEqualToString:'].implementation, {
onEnter: function (args) {
var str = new ObjC.Object(ptr(args[2])).toString()
console.log('[+] Hooked NSTaggedPointerString[- isEqualToString:] ->' , str);
}
});
// TRIGGER YOUR INTERCEPTOR
[objc_playground_2]-> a.isEqualToString_("foo")
[+] Hooked NSTaggedPointerString[- isEqualToString:] -> foo
1 // TRUE
[objc_playground_2]-> a.isEqualToString_("bar")
[+] Hooked NSTaggedPointerString[- isEqualToString:] -> bar
0 // FALSE
// frida -U -l open.js --no-pause -f com.yd.demoapp
// the below javascript code is the contents of open.js
var targetFunction = Module.findExportByName("libsystem_kernel.dylib", "open");
Interceptor.attach(targetFunction, {
onEnter: function (args) {
const path = Memory.readUtf8String(this.context.x0);
console.log("[+] " + path)
}
});
frida-trace --v Check it works
frida-trace --help Excellent place to read about Flags
frida-trace -f objc_playground Spawn and NO trace
frida-trace -m "+[NSUUID UUID]" -U "Debug CrackMe" Trace ObjC UUID static Class Method
frida-trace -m "*[ComVendorDebugger* *]" -U -f com.robot.demo.app ObjC wildcard trace on Classes
frida-trace -m "*[YDDummyApp.UserProfileMngr *]" -U -f com.robot.demo.app Trace mangled Swift functions
frida-trace -i "getaddrinfo" -i "SSLSetSessionOption" -U -f com.robot.demo Trace C function on iOS
frida-trace -m "*[*URLProtection* *]" -U -f com.robot.demo For https challenge information
frida-trace -m "*[NSURLSession* *didReceiveChallenge*]" -U -f com.robot.demo Check whether https check delegate used
frida-trace -U -f com.robot.demo.app -I libsystem_c.dylib Trace entire Module.
frida-trace -p $myapp -I UIKit Trace UIKit Module.
frida-trace -f objc_playground -I CoreFoundation Trace CoreFoundation Module.
frida-trace -I YDRustyKit -U -f com.yd.mobile Trace my own module.
frida-trace -m "-[NSURLRequest initWithURL:]" -U -f com.robot.demo Get app files and APIs
frida-trace -m "-[NSURL initWithString:]" -U -f com.robot.demo Find the API endpoints
frida-trace -m "*[NSURL absoluteString]" -U -f com.robot.demo My favorite of these
frida-trace -i "*strcpy" -f hitme aaaa bbbb
Instrumenting functions...
_platform_strcpy: Loaded handler at "/.../__handlers__/libSystem.B.dylib/_platform_strcpy.js"
Started tracing 1 function. Press Ctrl+C to stop.
Edit the auto-generated, template Javascript file.
-----------
onEnter: function (log, args, state) {
// strcpy() arg1 is the Source. arg0 is the Destination.
console.log('n[+] _platform_strcpy()');
var src_ptr = args[1].toString()
var src_string = Memory.readCString(args[1]);
var src_byte_array = Memory.readByteArray(args[1],4);
var textDecoder = new TextDecoder("utf-8");
var decoded = textDecoder.decode(src_byte_array);
console.log('[+] src_ptrt-> ' , src_ptr);
console.log('[+] src_stringt-> ' + src_string);
console.log('[+] src_byte_arrayt-> ' + src_byte_array);
console.log('[+] src_byte_array sizet-> ' + src_byte_array.byteLength);
console.log('[+] src_byte_array decodedt-> ' + decoded);
},
The results:
[+] _platform_strcpy()
[+] src_ptr -> 0x7ffeefbffaa6
[+] src_string -> aaaa
[+] src_byte_array -> [object ArrayBuffer]
[+] src_byte_array size -> 4
[+] decoded -> aaaa
[+] _platform_strcpy()
[+] src_ptr -> 0x7ffeefbffaab
[+] src_string -> bbbb
[+] src_byte_array -> [object ArrayBuffer]
[+] src_byte_array size -> 4
[+] decoded -> bbbb
frida-ps -Uai // get your bundle ID
frida --codeshare mrmacete/objc-method-observer -U -f funky-chicken.push-demo
[+] At the Frida prompt...
observeSomething('*[ABC* *]'); // any Class beginning with ABC, regardless of instance or static class
observeSomething('-[WKWebsiteDataStore httpCookieStore]');
observeSomething('-[WKWebAllowDenyPolicyListener *]');
observeSomething('-[WKWebView loadRequest:]'); // dump the URL to hit
observeSomething('-[WKWebView load*]'); // you get all HTML, js, css, etc
observeSomething('-[WKWebView loadHTMLString:baseURL:]') // really effective; see the entire request
observeSomething('-[WKWebView *Agent]'); // try to see if somebody set a custom UserAgent
observeSomething('*[* isEqualToString*]'); // watch string compares
bash -c "exec -a YDFooBar ./frida-server &"
frida-server -l 0.0.0.0:19999 &
frida-ps -ai -H 192.168.0.38:19999
frida-trace -m "*[NSURLSession* *didReceiveChallenge*]" -H 192.168.0.38:19999 -f com.youdog.rusty.tinyDormant
Objection is a runtime mobile exploration toolkit powered by Frida to assess the security posture of mobile applications without needing to write scripts.
pip3 install objection
objection device_type Get information about an attached device
objection explore Start the objection exploration REPL
objection explore --startup-command 'ios jailbreak simulate'
objection explore --startup-command 'ios jailbreak disable'
Early Instrumentation
ls
env This will print out the locations of the applications Library, Caches and Documents directories
!<shell command> Run OS command
file download <remote path> [<local path>]
file upload <local path> [<remote path>]
Upload/Download
file cat <file> View file
memory dump all <local destination>
memory dump from_base <base_address> <size_to_dump> <local_destination>
Dump all memory/Dump part
memory list modules List loaded modules in memory
memory list exports <module_name> Exports of a loaded module
memory search "<pattern eg: 41 41 41 ?? 41>" (--string) (--offsets-only)
memory write "<address>" "<pattern eg: 41 41 41 41>" (--string)
Search/Write
sqlite connect pewpew.sqlite Query the sqlite database
sqlite execute schema Have a look at the table structure
sqlite execute query select * from data;
Execute any query
import <local path frida-script> Import frida script
jobs list List running scripts/jobs
jobs kill <job id> Kill script/job
ios plist cat credentials.plist Read plist file
ios info binary Inspect binary info
ios sslpinning disable --quiet Disable SSL pinning
ios jailbreak simulate Simulate a jailbroken environment to understand how an application behaves
ios jailbreak disable Jailbreak detection bypass
ios nsuserdefaults get Dump NSUserDefaults
ios nsurlcredentialstorage dump Dump NSURLCredentialStorage
ios keychain dump Dump app keychain
ios cookies get Get secure flags and sensitive data stored in cookies
ios monitor crypto monitor Hooks CommonCrypto to output information about cryptographic operation
ios ui dump Dump UI hierarchy
ios ui alert "<message>" Show alert
env Local app paths
ios bundles list_bundles List bundles of the application
ios bundles list_frameworks List external frameworks used by the application
ios hooking list classes List classes of the app
ios hooking search classes <str> Search a class that contains a string
ios hooking list class_methods List methods of a specific class
ios hooking search methods <str> Search a method that contains a string
ios hooking watch class <class_name>
Hook all the methods of a class, dump all the initial parameters and returns
ios hooking watch method "-[<class_name> <method_name>]" --dump-args --dump-return --dump-backtrace
Hook an specific method of a class dumping the parameters, backtraces and returns
ios hooking set return_value "-[<class_name> <method_name>]" false
This will make the selected method return the indicated boolean
ios hooking generate simple <class_name>
Generate hooking template.
r2 frida://device-id/Snapchat Attach to a running app using the display name.
r2 frida://attach/usb//Gadget Attach to the Frida Gadget
r2 frida://device-id//com.snapchat.android Spawn an app using two // and the package name.
r2 frida://spawn/usb/device-id/com.android.app Or explicitly using the word spawn
r2 frida://spawn/usb//com.android.app Or without entering the device-id
=!? Get the list of commands
=!?~^i:
i Show target information
ii[*] List imports
il List libraries
is[*] <lib> List symbols of lib (local and global ones)
iE[*] <lib> Same as is, but only for the export global ones
iEa[*] (<lib>) <sym> Show address of export symbol
isa[*] (<lib>) <sym> Show address of symbol
ic <class> List Objective-C classes or methods of <class>
ip <protocol> List Objective-C protocols or methods of <protocol>
=!i Shows target information
=!i* Shows target information in r2 form
.=!i* Radare2 imports all the dynamic binary data from Frida. E.g: which architecture, endianness, pointer size, etc...
.=!iE* Radare2 imports all the dynamic export data from Frida for all the dynamic libraries.
.=!iE* <lib> Radare2 imports all the dynamic export data from Frida for only one specific library.
.=!ii* Radare2 imports all the dynamic import data from Frida.
=!ii <lib> List imports. Commonly used with the symbol ~, which is the internal grep of r2.
=!ii* <lib> List imports in r2 form.
=!il List libraries. Commonly used with the symbol ~, which is the internal grep of r2.
=!iE <lib> List exports of library(ies)
=!iEa (<lib>) <sym> Show address of export symbol
=!iEa* (<lib>) <sym> Show address of export symbol in r2 format
=!isa[*] (<lib>) <sym> Show address of symbol
=!ic List classes
=!/ keyword Search hex/string pattern in memory ranges (see search.in=?)
> =!?~^/:
/[x][j] <string|hexpairs> Search hex/string pattern in memory ranges (see search.in=?)
/w[j] string Search wide string
/v[1248][j] value Search for a value honoring e cfg.bigendian of given width
> =!?~^d:
db (<addr>|<sym>) List or place breakpoint
db- (<addr>|<sym>)|* Remove breakpoint(s)
dc Continue breakpoints or resume a spawned process
dd[-][fd] ([newfd]) List, dup2 or close filedescriptors
dm[.|j|*] Show memory regions
dma <size> Allocate bytes on the heap, address is returned
dmas <string> Allocate a string inited with on the heap
dmad <addr> <size> Allocate bytes on the heap, copy contents from
dmal List live heap allocations created with dma[s]
dma- (<addr>...) Kill the allocations at (or all of them without param)
dmp <addr> <size> <perms> Change page at
dmm List all named squashed mapsdmh List all heap allocated chunksdmhj List all heap allocated chunks in JSONdmh* Export heap chunks and regions as r2 flagsdmhm Show which maps are used to allocate heap chunksdp Show current piddpt Show threadsdr Show thread registers (see dpt)dl libname Dlopen a librarydl2 libname [main] Inject library using Frida's >= 8.2 new APIdt (<addr>|<sym>) ... Trace list of addresses or symbolsdth (<addr>|<sym>) (x y..) Define function header (z=str,i=int,v=hex barray,s=barray)dt- Clear all tracingdtr <addr> (<regs>...) Trace register valuesdtf <addr> [fmt] Trace address with format (^ixzO) (see dtf?)dtSf[*j] [sym|addr] Trace address or symbol using the stalker (Frida >= 10.3.13)dtS[*j] seconds Trace all threads for given seconds using the stalkerdi[0,1,-1] [addr] Intercept and replace return value of addressdx [hexpairs] Inject code and execute it (TODO)dxc [sym|addr] [args..] Call the target symbol with given args
e[?] [a[=b]] List/get/set config evaluable vars
[0x00000000]> =!e
e patch.code=true
e search.in=perm:r--
e search.quiet=false
e stalker.event=compile
e stalker.timeout=300
e stalker.in=raw =!. script.js
=!ic List iOS classes
More info: https://mobile-security.gitbook.io/mobile-security-testing-guide/ios-testing-guide/0x06c-reverse-engineering-and-tampering#tampering-and-runtime-instrumentation
Frida GUI.
Frida GUI.
Frida GUI. https://github.com/FuzzySecurity/Fermion
More info:
https://frida.re/docs/examples/ios/
https://frida.re/docs/frida-trace/
https://frida.re/docs/examples/ios/
https://github.com/sensepost/objection/wiki/Using-objection
Apple's Entitlements Troubleshooting – https://developer.apple.com/library/content/technotes/tn2415/_index.html
Apple's Code Signing – https://developer.apple.com/support/code-signing/
Cycript Manual – http://www.cycript.org/manual/
Frida iOS Tutorial – https://www.frida.re/docs/ios/
Frida iOS Examples – https://www.frida.re/docs/examples/ios/
r2frida Wiki – https://github.com/enovella/r2frida-wiki/blob/master/README.md
Charlie Miller, Dino Dai Zovi. The iOS Hacker's Handbook. Wiley, 2012 – https://www.wiley.com/en-us/iOS+Hacker's+Handbook-p-9781118204122
Jonathan Levin. Mac OS X and iOS Internals: To the Apple's Core. Wiley, 2013 – http://newosxbook.com/MOXiI.pdf
Install SSL Kill Switch 2 from https://github.com/nabla-c0d3/ssl-kill-switch2/releases/
Open your settings and enable SSL Kill Switch 2
Run Charles on PC.
Install Charles Root Certificate on iOS device:
Help → SSL Proxing → Install Charles Root Certificate on Mobile Device or Remote Browser.
The following window will appear:
Depending on your network architecture the IP address Charles is running on may differ.
Proxy → SSL Proxying Settings... → Add (Include) → Host: * ; Port: *
Since all binary files inside an .ipa are encrypted with AES and being decrypted with a private key by Secure Enclave Processor at the runtime there is a few ways to decrypt it:
If you don't have Node.js:
brew install nvm
nvm install node
To dump decrypted ipa using bagbak utility install it on desktop:
sudo npm install -g bagbak
Then download your application from the App Store and dump:
bagbak <bundle id or name> --uuid <uuid> --output <output>
There are several ways to run the hardware AES engine:
Patch iBoot to jump to aes_crypto_cmd
Use OpenIBoot
Use XPwn with a kernel patch
Use Greenpois0n console:
ideviceenterrecovery
irecovery --shell
go aes dec <file>
Use ipwndfu
Use checkra1n
Run checkra1n with -p to run into pongoOS (https://github.com/checkra1n/pongoOS) and use the aes command over USB
If you want to disassemble an application from the App Store, remove the FairPlay DRM first.
After decrypting .ipa file open app binary in disassembler like IDA Pro.
In this section the term "app binary" refers to the Macho-O file in the application bundle which contains the compiled code, and should not be confused with the application bundle - the IPA file.
If you have a license for IDA Pro, you can analyze the app binary using IDA Pro as well.
To get started, simply open the app binary in IDA Pro.
Upon opening the file, IDA Pro will perform auto-analysis, which can take a while depending on the size of the binary. Once the auto-analysis is completed you can browse the disassembly in the IDA View (Disassembly) window and explore functions in the Functions window, both shown in the screenshot below.
https://github.com/ChiChou/IDA-ObjCExplorer/blob/master/ObjCExplore.py – Obj-C Classes Explorer for IDA Pro. Just press Ctrl + Shift + E.
https://github.com/avast/retdec-idaplugin – RetDec decompiler for IDA Pro. Just press Ctrl + D.
https://github.com/zynamics/objc-helper-plugin-ida – zynamics Objective-C helper script.
https://github.com/techbliss/Frida_For_Ida_Pro – Connect frida.
https://github.com/vadimszzz/idapython/blob/master/cortex_m_firmware.py – IDA Python module for loading ARM Cortex M firmware.
https://github.com/saelo/ida_scripts/blob/master/kernelcache.py – Identify and rename function stubs in an iOS kernelcache.
https://github.com/luismiras/IDA-iOS-scripts/blob/master/find_iOS_syscalls.py – Find iOS syscalls.
https://github.com/stefanesser/IDA-IOS-Toolkit/blob/master/listAllKEXT.py – List all Kexts.
https://github.com/stefanesser/IDA-IOS-Toolkit/blob/master/findSyscallTable.py – This script searches the iOS syscall table within the iOS kernelcache.
https://github.com/stefanesser/IDA-IOS-Toolkit/blob/master/fixupSysctlSet.py – This script ensures that all sysctl_oid structures referenced by the sysctl_set segment are marked correctly.
https://github.com/bazad/ida_kernelcache – An IDA Toolkit for analyzing iOS kernelcaches.
You can use class-dump to get information about methods in the application's source code.
Note the architectures: armv7 (which is 32-bit) and arm64. This design of a fat binary allows an application to be deployed on all devices. To analyze the application with class-dump, we must create a so-called thin binary, which contains one architecture only:
iOS8-jailbreak:~ root# lipo -thin armv7 DamnVulnerableIOSApp -output DVIA32
And then we can proceed to performing class-dump:
iOS8-jailbreak:~ root# class-dump DVIA32
@interface FlurryUtil : ./DVIA/DVIA/DamnVulnerableIOSApp/DamnVulnerableIOSApp/YapDatabase/Extensions/Views/Internal/
{
}
+ (BOOL)appIsCracked;
+ (BOOL)deviceIsJailbroken; Note the plus sign, which means that this is a class method that returns a BOOL type. A minus sign would mean that this is an instance method. Refer to later sections to understand the practical difference between these.
Strings are always a good starting point while analyzing a binary, as they provide context to the associated code. For instance, an error log string such as "Cryptogram generation failed" gives us a hint that the adjoining code might be responsible for the generation of a cryptogram.
In order to extract strings from an iOS binary, you can use GUI tools such as Ghidra or Cutter or rely on CLI-based tools such as the strings Unix utility strings <path_to_binary> or radare2's rabin2 rabin2 -zz <path_to_binary>. When using the CLI-based ones you can take advantage of other tools such as grep (e.g. in conjunction with regular expressions) to further filter and analyze the results.
nm
nm libprogressbar.a | less
rabin2
rabin2 -s file
radare2
is~FUNC
Check URLs:
strings <binary inside app bundle> | grep -E 'session|https'
strings <binary inside app bundle> | grep -E 'pinning'
rabin2 -qz <binary inside app bundle> // in Data Section
rabin2 -qzz <binary inside app bundle> // ALL strings in binary
jtool -dA __TEXT.__cstring c_playground
Dumping C-Strings from address 0x100000f7c (Segment: __TEXT.__cstring)..
Address : 0x100000f7c = Offset 0xf7c
0x100000f7c: and we have a winner @ %ldr
0x100000f98: and that's a wrap folks!r
IDA Pro can be used for obtaining cross references by right clicking the desired function and selecting Show xrefs.
w0 = 32-bitx0 = 64-bitwzr or xzr. Write to = discard, read from = 0.sp - unlike other instruction sets, never modified implicitly (e.g. no push/pop).pc, not modifiable directly.str).mov to copy one register to another, e.g. mov x0, x1 -> x0 = x1.0 loaded from wzr/xzr.orr x0, xzr, 5.movz+movk, e.g.:
movz x0, 0x1234, lsl 32
movk x0, 0x5678, lsl 16
movk x0, 0x9abcx0 = 0x123456789abc.movn for negative values, e.g. movn x0, 1 -> x0 = -1.lsl and lsr instructions = logic-shift-left and logic-shift-right, e.g. lsl x0, x0, 8 -> x0 <<= 8.
lsl and lsr not only used as instructions, but also as operands to other instructions (see movz above).asl for arithmetic shift also exists, but less frequently used.ldr and str with multiple variations and addressing modes:
ldr x0, [x1] -> x0 = *x1str x0, [x1] -> *x1 = x0ldr x0, [x1, 0x10] -> x0 = *(x1 + 0x10)ldp/stp to load/store two registers at once behind each other, e.g.:stp x0, x1, [x2] -> *x2 = x0; *(x2 + 8) = x1;xN for 64-bit, wN for 32-bitldrh/srth for 16-bitldrb/strb for 8-bitldrsw x0, [x1] -> load 32-bit int, sign extend to 64-bitldrsh x0, [x1] -> load 16-bit int, sign extend to 64-bitldrsb x0, [x1] -> load 8-bit int, sign extend to 64-bitstr instructions)ldr x0, [x1, 0x10]ldr x0, [x1, 0x10]! (notice the !) -> x1 += 0x10; x0 = *x1;ldr x0, [x1], 0x10 -> x0 = *x1; x1 += 0x10;adr x0, 0x12345 (only works for small offset from PC)adrp+add:
adrp x0, 0xffffff8012345000 ; "address of page", last 12 bits are always zero
add x0, x0, 0x678ldr.Note: Only dealing with integral types here. The rules change when floating-point is involved.
x0-x7 first 8 arguments, rest on the stack (low address to high) with natural alignment (as if they were members of a struct)x8 pointer to where to write the return value if >128 bits, otherwise scratch registerx9-x17 scratch registersx18 platform register (reserved, periodically zeroed by XNU)x19-x28 callee-savedx29 frame pointer (basically also just callee-saved)x30 return addressx19-x28 usually start like this:
stp x24, x23, [sp, -0x40]!
stp x22, x21, [sp, 0x10]
stp x20, x19, [sp, 0x20]
stp x29, x30, [sp, 0x30]
add x29, sp, 0x30ldp x29, x30, [sp, 0x30]
ldp x20, x19, [sp, 0x20]
ldp x22, x21, [sp, 0x10]
ldp x24, x23, [sp], 0x40
retadd sp, sp, 0x... and sub sp, sp, 0x....x0-x7 come before variadic arguments on the stack, naturally aligned.x0.x0, the second/upper half in x1.x8 to where the result is written.nzcv holds condition flags (Negative, Zero, Carry, oVerflow).instr.cond), others as source operands (instr ..., cond). List of condition codes:
eq/ne = equal/not equallt/le/gt/ge = less than/less or equal/greater than/greater or equal (signed)lo/ls/hi/hs = lower/lower or same/higher/higher or same (unsigned)cs/cc = carry set/carry clear are aliases of hs/lo.cmp = most common/basic compare instruction, sets condition flags. Examples:
cmp x0, x1
cmp x0, 3cmn = compare negativetst = bitwise testadds/adcs = add/add with carrysubs/sbcs = subtract/subtract with carrynegs/ngcs = negate/negate with carrycset = conditional set, e.g.:
cmp x0, 3
cset x0, lox0 = (x0 < 3)csel = conditional select, e.g.:
cmp x0, 3
csel x0, x1, x2, lox0 = (x0 < 3) ? x1 : x2ccmp = conditional compare, e.g.:
cmp x0, 3
ccmp x0, 7, 2, hs
b.hi 0xffffff8012345678hi condition will be true if x0 < 3 || x0 > 7 (third ccmp operand is raw nzcv data).b = simple branch, jump to PC-relative address.b 0xffffff8012345678cmp x0, 3
b.lo 0xffffff8012345678 ; jump to 0xffffff8012345678 if x < 3cbz/cbnz = compare-branch-zero and compare-branch-non-zero.cmp xN, 0
b.eq 0x...cmp xN, 0
b.ne 0x...if(x) or if(!x).)tbz/tbnz = test single bit and branch if zero/non-zero.tbz x0, 3, ... translates to if((x0 & (1 << 3)) == 0) goto ....bl = branch-and-link (e.g. bl 0xffffff8012345678)x30 and jump to PC-relative address. Used for static function calls.blr = branch-and-link to register (e.g. blr x8)x30 and jump to address in x8. Used for calls with function pointers or C++ virtual methods.br = branch to register (e.g. br x8)x8. Used for tail calls.ret = return to address in register, default: x30x30 (e.g. ret x8), but compiler doesn't usually generate that.nop = do nothingsvc = make a system call using an immediate value (e.g. svc 0x80). Note that the immediate value is separate from the syscall number. XNU ignores the immediate and expects the syscall number in x16.. = special symbol that refers to the address of the instruction it is used in (e.g. adr x0, .)Install the following prerequisites:
brew install ldid xz
Set up the THEOS environment variable:
echo "export THEOS=~/theos" >> ~/.zshrc
source ~/.zshrc
Clone Theos:
git clone --recursive https://github.com/theos/theos.git $THEOS
Get the toolchain:
Xcode contains the toolchain.
Get an iOS SDK:
Xcode always provides the latest iOS SDK, but as of Xcode 7.3, it no longer includes private frameworks you can link against. This may be an issue when developing tweaks. You can get patched SDKs from our SDKs repo.
curl -LO https://github.com/theos/sdks/archive/master.zip
TMP=$(mktemp -d)
unzip master.zip -d $TMP
mv $TMP/sdks-master/*.sdk $THEOS/sdks
rm -r master.zip $TMP
Logos is a Perl regex-based preprocessor that simplifies the boilerplate code needed to create hooks for Objective-C methods and C functions with an elegant Objective-C-like syntax. It’s most commonly used along with the Theos build system, which was originally developed to create jailbreak tweaks. Logos was once integrated in the same Git repo as Theos, but now has been decoupled from Theos to its own repo.
Logos aims to provide an interface for Cydia Substrate by default, but can be configured to directly use the Objective-C runtime.
Logos is a component of the Theos development suite.
%hookf(return type, functionName, arguments list...) {
/* body */
}
Generate a function hook for the function named functionName. Set functionName in %init to an expression if the symbol should be dynamically looked up.
Example:
// Given the function prototype (only add it yourself if it's not declared in an included/imported header)
FILE *fopen(const char *path, const char *mode);
// The hook is thus made
%hookf(FILE *, fopen, const char *path, const char *mode) {
puts("Hey, we're hooking fopen to deny relative paths!");
if (path[0] != '/') {
return NULL;
}
return %orig; // Call the original implementation of this function
}
// functions can also be looked up at runtime, if, for example, the function is in a private framework
%hookf(BOOL, MGGetBoolAnswer, CFStringRef string) {
if (CFEqual(string, CFSTR("StarkCapability"))) {
return YES;
}
return %orig;
}
%ctor() {
%init(MGGetBoolAnswer = MSFindSymbol(NULL, "_MGGetBoolAnswer"));
}
%ctor {
/* body */
}
Generate an anonymous constructor (of default priority). This function is executed after the binary is loaded into memory. argc, argv, and envp are implicit arguments so they can be used as they would be in a main function.
%dtor {
/* body */
}
Generate an anonymous deconstructor (of default priority). This function is executed before the binary is unloaded from memory.argc, argv, and envp are implicit arguments so they can be used as they would be in a main function.
The directives in this category open a block of code which must be closed by an %end directive (shown below). These should not exist within functions or methods.
%group GroupName
/* %hooks */
%end
Generate a hook group with the name GroupName. Groups can be used for conditional initialization or code organization. All ungrouped hooks are in the default group, initializable via %init without arguments.
Cannot be inside another %group block.
Grouping can be used to manage backwards compatibility with older code.
Example:
%group iOS8
%hook IOS8_SPECIFIC_CLASS
// your code here
%end // end hook
%end // end group ios8
%group iOS9
%hook IOS9_SPECIFIC_CLASS
// your code here
%end // end hook
%end // end group ios9
%ctor {
if (kCFCoreFoundationVersionNumber > 1200) {
%init(iOS9);
} else {
%init(iOS8);
}
}
%hook ClassName
/* objc methods */
%end
Open a hook block for the class named ClassName.
Can be inside a %group block.
Example:
%hook SBApplicationController
- (void)uninstallApplication:(SBApplication *)application {
NSLog(@"Hey, we're hooking uninstallApplication:!");
%orig; // Call the original implementation of this method
}
%end
%new
/* objc method */
%new(signature)
/* objc method */
Add a new method to a hooked class or subclass by adding this directive above the method definition. signature is the Objective-C type encoding for the new method; if it is omitted, one will be generated.
Must be inside a %hook or %subclass block.
Example:
%new
- (void)handleTapGesture:(UITapGestureRecognizer *)gestureRecognizer {
NSLog(@"Recieved tap: %@", gestureRecognizer);
}
%subclass ClassName: Superclass <Protocol list>
/* %properties and methods */
%end
Generate a subclass at runtime. Like @property in normal Objective-C classes, you can use %property to add properties to the subclass. The %new specifier is needed for a method that doesn’t exist in the superclass. To instantiate an object of the new class, you can use the %c operator.
Can be inside a %group block.
Example:
// An interface is required to be able to call methods of the runtime subclass using block syntax.
@interface MyObject : NSObject
@property (nonatomic, retain) NSString * someValue;
@end
%subclass MyObject : NSObject
%property (nonatomic, retain) NSString * someValue;
- (instancetype)init {
if ((self = %orig)) {
[self setSomeValue:@"value"];
}
return self;
}
%end
%ctor {
// The runtime subclass cannot be linked at compile time so you have to use %c().
MyObject *myObject = [[%c(MyObject) alloc] init];
NSLog(@"myObject: %@", [myObject someValue]);
}
%property (nonatomic|assign|retain|copy|weak|strong|getter=...|setter=...) Type name;
Add a property to a %subclass just like you would with @property to a normal Objective-C subclass as well as adding new properties to existing classes within %hook.
Must be inside a %hook or %subclass block.
%end
Close a %group, %hook or %subclass block.
The directives in this category should only exist within a function or method body.
%init;
%init([<ClassName>=<expr>, …]);
%init(GroupName[, [+|-]<ClassName>=<expr>, …]);
Initialize a group’s method and function hooks. Passing no group name will initialize the default group. Passing ClassName=exprarguments will substitute the given expressions for those classes at initialization time. The + sigil (as in class methods in Objective-C) can be prepended to the classname to substitute an expression for the metaclass. If not specified, the sigil defaults to -, to substitute the class itself. If not specified, the metaclass is derived from the class.
The class name replacement is specially useful for classes that contain characters that can’t be used as the class name token for the %hook directive, such as spaces and dots.
Example:
%hook ClassName
- (id)init {
return %orig;
}
%end
%ctor {
%init(ClassName=objc_getClass("SwiftApp.ClassName"));
}
%c([+|-]ClassName)
Evaluates to ClassName at runtime. If the + sigil is specified, it evaluates to MetaClass instead of Class. If not specified, the sigil defaults to -, evaluating to Class.
%orig
%orig(args, …)
Call the original hooked function or method. Doesn’t work in a %new‘d method. Works in subclasses, strangely enough, because MobileSubstrate will generate a super-call closure at hook time. (If the hooked method doesn’t exist in the class we’re hooking, it creates a stub that just calls the superclass implementation.) args is passed to the original function - don’t include self and _cmd, Logos does this for you.
Example:
%hook ClassName
- (int)add:(int)a to:(int)b {
if (a != 0) {
// Return original result if `a` is not 0
return %orig;
}
// Otherwise, use 1 as `a`
return %orig(1, b);
}
%end
&%orig
Get a pointer to the original function or method. Return type is void (*)(id, SEL[, arg types])
Example:
// Call from outside hooked method:
void (*orig_ClassName_start)(id, SEL) = nil;
void doStuff(id self, SEL _cmd) {
if (self && orig_ClassName_start) {
orig_ClassName_start(self, _cmd);
}
}
%hook ClassName
- (void)start {
%orig;
orig_ClassName_start = &%orig;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC),
dispatch_get_main_queue(), ^{
doStuff(self, _cmd);
});
}
%end
// Call with another object:
%hook ClassName
- (int)add:(int)a to:(int)b {
int (*_orig)(id, SEL, int, int) = &%orig;
ClassName * myObject = [ClassName new];
int r = _orig(myObject, _cmd, 1, 2);
[myObject release];
return r;
}
%end
Real world example at PreferenceLoader
%log;
%log([(<type>)<expr>, …]);
Dump the method arguments to syslog. Typed arguments included in %log will be logged as well.
You can use logify.pl to create a Logos source file from a header file that will log all of the functions of that header file. Here is an example of a very simple Logos tweak generated by logify.pl.
Given a header file named SSDownloadAsset.h:
@interface SSDownloadAsset : NSObject
- (NSString *)finalizedPath;
- (NSString *)downloadPath;
- (NSString *)downloadFileName;
+ (id)assetWithURL:(id)url type:(int)type;
- (id)initWithURLRequest:(id)urlrequest type:(int)type;
- (id)initWithURLRequest:(id)urlrequest;
- (id)_initWithDownloadMetadata:(id)downloadMetadata type:(id)type;
@end
You can find logify.pl at $THEOS/bin/logify.pl and you would use it as so:
$THEOS/bin/logify.pl ./SSDownloadAsset.h
The resulting output should be:
%hook SSDownloadAsset
- (NSString *)finalizedPath { %log; NSString * r = %orig; NSLog(@" = %@", r); return r; }
- (NSString *)downloadPath { %log; NSString * r = %orig; NSLog(@" = %@", r); return r; }
- (NSString *)downloadFileName { %log; NSString * r = %orig; NSLog(@" = %@", r); return r; }
+ (id)assetWithURL:(id)url type:(int)type { %log; id r = %orig; NSLog(@" = %@", r); return r; }
- (id)initWithURLRequest:(id)urlrequest type:(int)type { %log; id r = %orig; NSLog(@" = %@", r); return r; }
- (id)initWithURLRequest:(id)urlrequest { %log; id r = %orig; NSLog(@" = %@", r); return r; }
- (id)_initWithDownloadMetadata:(id)downloadMetadata type:(id)type { %log; id r = %orig; NSLog(@" = %@", r); return r; }
%end
| Extension | Process order |
|---|---|
| x | will be processed by Logos, then preprocessed and compiled as Objective-C. |
| xm | will be processed by Logos, then preprocessed and compiled as Objective-C++. |
| xi | will be preprocessed first, then Logos will process the result, and then it will be compiled as Objective-C. |
| xmi | will be preprocessed first, then Logos will process the result, and then it will be compiled as Objective-C++. |
xi or xmi files enable Logos directives to be used in preprocessor macros, such as #define. You can also import other Logos source files with the #include statement. However, this is discouraged, since this leads to longer build times recompiling code that hasn’t changed. Separating into x and xm files, sharing variables and functions via extern declarations, is recommended.
These file extensions control how a build system such as Theos should build a Logos file. Logos itself does not take the file extension into account and works regardless of whether a file is Objective-C or Objective-C++.
https://theos.dev/docs/
https://cydia.saurik.com/faq/developing.html
http://www.cydiasubstrate.com/id/7cee77bc-c4a5-4b8b-b6ef-36e7dd039692/
http://www.cydiasubstrate.com/inject/
https://iphonedev.wiki/index.php/Cydia_Substrate
https://cwcaude.github.io/project/tutorial/2020/07/02/iOS-tweak-dev-1.html
https://cwcaude.github.io/project/tutorial/2020/07/04/iOS-tweak-dev-2.html
https://cwcaude.github.io/project/tutorial/2020/07/12/iOS-tweak-dev-3.html
https://cwcaude.github.io/project/tutorial/2020/07/16/iOS-tweak-dev-4.html
