13 KiB
macOS Basic Objective-C
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Objective-C
{% hint style="danger" %} Note that programs written in Objective-C retain their class declarations when compiled into Mach-O binaries. Such class declarations include the name and type of: {% endhint %}
- The class
- The class methods
- The class instance variables
You can get this information using class-dump:
class-dump Kindle.app
Note that this names could be obfuscated to make the reversing of the binary more difficult.
Classes, Methods & Objects
Interface, Properties & Methods
// Declare the interface of the class
@interface MyVehicle : NSObject
// Declare the properties
@property NSString *vehicleType;
@property int numberOfWheels;
// Declare the methods
- (void)startEngine;
- (void)addWheels:(int)value;
@end
Class
@implementation MyVehicle : NSObject
// No need to indicate the properties, only define methods
- (void)startEngine {
NSLog(@"Engine started");
}
- (void)addWheels:(int)value {
self.numberOfWheels += value;
}
@end
Object & Call Method
To create an instance of a class the alloc method is called which allocate memory for each property and zero those allocations. Then init is called, which initilize the properties to the required values.
// Something like this:
MyVehicle *newVehicle = [[MyVehicle alloc] init];
// Which is usually expressed as:
MyVehicle *newVehicle = [MyVehicle new];
// To call a method
// [myClassInstance nameOfTheMethodFirstParam:param1 secondParam:param2]
[newVehicle addWheels:4];
Class Methods
Class methods are defined with the plus sign (+) not the hyphen (-) that is used with instance methods. Like the NSString class method stringWithString:
+ (id)stringWithString:(NSString *)aString;
Setter & Getter
To set & get properties, you could do it with a dot notation or like if you were calling a method:
// Set
newVehicle.numberOfWheels = 2;
[newVehicle setNumberOfWheels:3];
// Get
NSLog(@"Number of wheels: %i", newVehicle.numberOfWheels);
NSLog(@"Number of wheels: %i", [newVehicle numberOfWheels]);
Instance Variables
Alternatively to setter & getter methods you can use instance variables. These variables have the same name as the properties but starting with a "_":
- (void)makeLongTruck {
_numberOfWheels = +10000;
NSLog(@"Number of wheels: %i", self.numberOfLeaves);
}
Protocols
Protocols are set of method declarations (without properties). A class that implements a protocol implement the declared methods.
There are 2 types of methods: mandatory and optional. By default a method is mandatory (but you can also indicate it with a @required tag). To indicate that a method is optional use @optional.
@protocol myNewProtocol
- (void) method1; //mandatory
@required
- (void) method2; //mandatory
@optional
- (void) method3; //optional
@end
All together
// gcc -framework Foundation test_obj.m -o test_obj
#import <Foundation/Foundation.h>
@protocol myVehicleProtocol
- (void) startEngine; //mandatory
@required
- (void) addWheels:(int)value; //mandatory
@optional
- (void) makeLongTruck; //optional
@end
@interface MyVehicle : NSObject <myVehicleProtocol>
@property int numberOfWheels;
- (void)startEngine;
- (void)addWheels:(int)value;
- (void)makeLongTruck;
@end
@implementation MyVehicle : NSObject
- (void)startEngine {
NSLog(@"Engine started");
}
- (void)addWheels:(int)value {
self.numberOfWheels += value;
}
- (void)makeLongTruck {
_numberOfWheels = +10000;
NSLog(@"Number of wheels: %i", self.numberOfWheels);
}
@end
int main() {
MyVehicle* mySuperCar = [MyVehicle new];
[mySuperCar startEngine];
mySuperCar.numberOfWheels = 4;
NSLog(@"Number of wheels: %i", mySuperCar.numberOfWheels);
[mySuperCar setNumberOfWheels:3];
NSLog(@"Number of wheels: %i", mySuperCar.numberOfWheels);
[mySuperCar makeLongTruck];
}
Basic Classes
String
{% code overflow="wrap" %}
// NSString
NSString *bookTitle = @"The Catcher in the Rye";
NSString *bookAuthor = [[NSString alloc] initWithCString:"J.D. Salinger" encoding:NSUTF8StringEncoding];
NSString *bookPublicationYear = [NSString stringWithCString:"1951" encoding:NSUTF8StringEncoding];
{% endcode %}
Basic classes are immutable, so to append a string to an existing one a new NSString needs to be created.
{% code overflow="wrap" %}
NSString *bookDescription = [NSString stringWithFormat:@"%@ by %@ was published in %@", bookTitle, bookAuthor, bookPublicationYear];
{% endcode %}
Or you could also use a mutable string class:
{% code overflow="wrap" %}
NSMutableString *mutableString = [NSMutableString stringWithString:@"The book "];
[mutableString appendString:bookTitle];
[mutableString appendString:@" was written by "];
[mutableString appendString:bookAuthor];
[mutableString appendString:@" and published in "];
[mutableString appendString:bookPublicationYear];
{% endcode %}
Number
{% code overflow="wrap" %}
// character literals.
NSNumber *theLetterZ = @'Z'; // equivalent to [NSNumber numberWithChar:'Z']
// integral literals.
NSNumber *fortyTwo = @42; // equivalent to [NSNumber numberWithInt:42]
NSNumber *fortyTwoUnsigned = @42U; // equivalent to [NSNumber numberWithUnsignedInt:42U]
NSNumber *fortyTwoLong = @42L; // equivalent to [NSNumber numberWithLong:42L]
NSNumber *fortyTwoLongLong = @42LL; // equivalent to [NSNumber numberWithLongLong:42LL]
// floating point literals.
NSNumber *piFloat = @3.141592654F; // equivalent to [NSNumber numberWithFloat:3.141592654F]
NSNumber *piDouble = @3.1415926535; // equivalent to [NSNumber numberWithDouble:3.1415926535]
// BOOL literals.
NSNumber *yesNumber = @YES; // equivalent to [NSNumber numberWithBool:YES]
NSNumber *noNumber = @NO; // equivalent to [NSNumber numberWithBool:NO]
{% endcode %}
Array, Sets & Dictionary
{% code overflow="wrap" %}
// Inmutable arrays
NSArray *colorsArray1 = [NSArray arrayWithObjects:@"red", @"green", @"blue", nil];
NSArray *colorsArray2 = @[@"yellow", @"cyan", @"magenta"];
NSArray *colorsArray3 = @[firstColor, secondColor, thirdColor];
// Mutable arrays
NSMutableArray *mutColorsArray = [NSMutableArray array];
[mutColorsArray addObject:@"red"];
[mutColorsArray addObject:@"green"];
[mutColorsArray addObject:@"blue"];
[mutColorsArray addObject:@"yellow"];
[mutColorsArray replaceObjectAtIndex:0 withObject:@"purple"];
// Sets
NSSet *fruitsSet1 = [NSSet setWithObjects:@"apple", @"banana", @"orange", nil];
NSSet *fruitsSet2 = [NSSet setWithArray:@[@"apple", @"banana", @"orange"]];
// Inmutable sets
NSMutableSet *mutFruitsSet = [NSMutableSet setWithObjects:@"apple", @"banana", @"orange", nil];
[mutFruitsSet addObject:@"grape"];
[mutFruitsSet removeObject:@"apple"];
// Dictionary
NSDictionary *fruitColorsDictionary = @{
@"apple" : @"red",
@"banana" : @"yellow",
@"orange" : @"orange",
@"grape" : @"purple"
};
// In dictionaryWithObjectsAndKeys you specify the value and then the key:
NSDictionary *fruitColorsDictionary2 = [NSDictionary dictionaryWithObjectsAndKeys:
@"red", @"apple",
@"yellow", @"banana",
@"orange", @"orange",
@"purple", @"grape",
nil];
// Mutable dictionary
NSMutableDictionary *mutFruitColorsDictionary = [NSMutableDictionary dictionaryWithDictionary:fruitColorsDictionary];
[mutFruitColorsDictionary setObject:@"green" forKey:@"apple"];
[mutFruitColorsDictionary removeObjectForKey:@"grape"];
{% endcode %}
Blocks
Blocks are functions that behaves as objects so they can be passed to functions or stored in arrays or dictionaries. Also, they can represent a value if they are given values so it's similar to lambdas.
{% code overflow="wrap" %}
returnType (^blockName)(argumentType1, argumentType2, ...) = ^(argumentType1 param1, argumentType2 param2, ...){
//Perform operations here
};
// For example
int (^suma)(int, int) = ^(int a, int b){
return a+b;
};
NSLog(@"3+4 = %d", suma(3,4));
{% endcode %}
It's also possible to define a block type to be used as a parameter in functions:
// Define the block type
typedef void (^callbackLogger)(void);
// Create a bloack with the block type
callbackLogger myLogger = ^{
NSLog(@"%@", @"This is my block");
};
// Use it inside a function as a param
void genericLogger(callbackLogger blockParam) {
NSLog(@"%@", @"This is my function");
blockParam();
}
genericLogger(myLogger);
// Call it inline
genericLogger(^{
NSLog(@"%@", @"This is my second block");
});
Files
{% code overflow="wrap" %}
// Manager to manage files
NSFileManager *fileManager = [NSFileManager defaultManager];
// Check if file exists:
if ([fileManager fileExistsAtPath:@"/path/to/file.txt" ] == YES) {
NSLog (@"File exists");
}
// copy files
if ([fileManager copyItemAtPath: @"/path/to/file1.txt" toPath: @"/path/to/file2.txt" error:nil] == YES) {
NSLog (@"Copy successful");
}
// Check if the content of 2 files match
if ([fileManager contentsEqualAtPath:@"/path/to/file1.txt" andPath:@"/path/to/file2.txt"] == YES) {
NSLog (@"File contents match");
}
// Delete file
if ([fileManager removeItemAtPath:@"/path/to/file1.txt" error:nil]) {
NSLog(@"Removed successfully");
}
{% endcode %}
It's also possible to manage files using NSURL objects instead of NSString objects. The method names are similar, but with URL instead of Path.
NSURL *fileSrc = [NSURL fileURLWithPath:@"/path/to/file1.txt"];
NSURL *fileDst = [NSURL fileURLWithPath:@"/path/to/file2.txt"];
[fileManager moveItemAtURL:fileSrc toURL:fileDst error: nil];
Most basic classes has a method writeToFile:<path> atomically:<YES> encoding:<encoding> error:nil defined that allows them to be directly be written to a file:
{% code overflow="wrap" %}
NSString* tmp = @"something temporary";
[tmp writeToFile:@"/tmp/tmp1.txt" atomically:YES encoding:NSASCIIStringEncoding error:nil];
{% endcode %}
☁️ HackTricks Cloud ☁️ -🐦 Twitter 🐦 - 🎙️ Twitch 🎙️ - 🎥 Youtube 🎥
- Do you work in a cybersecurity company? Do you want to see your company advertised in HackTricks? or do you want to have access to the latest version of the PEASS or download HackTricks in PDF? Check the SUBSCRIPTION PLANS!
- Discover The PEASS Family, our collection of exclusive NFTs
- Get the official PEASS & HackTricks swag
- Join the 💬 Discord group or the telegram group or follow me on Twitter 🐦@carlospolopm.
- Share your hacking tricks by submitting PRs to the hacktricks repo and hacktricks-cloud repo.