This module exploits a type confusion bug in the Javascript Proxy object in
WebKit. The DFG JIT does not take into account that, through the use of a Proxy,
it is possible to run arbitrary JS code during the execution of a CreateThis
operation. This makes it possible to change the structure of e.g. an argument
without causing a bailout, leading to a type confusion (CVE-2018-4233).
The type confusion leads to the ability to allocate fake Javascript objects,
as well as the ability to find the address in memory of a Javascript object.
This allows us to construct a fake JSCell object that can be used to read
and write arbitrary memory from Javascript. The module then uses a ROP chain
to write the first stage shellcode into executable memory within the Safari
process and kick off its execution.
The first stage maps the second stage macho (containing CVE-2017-13861) into
executable memory, and jumps to its entrypoint. The CVE-2017-13861 async_wake
exploit leads to a kernel task port (TFP0) that can read and write arbitrary
kernel memory. The processes credential and sandbox structure in the kernel
is overwritten and the meterpreter payloads code signature hash is added to
the kernels trust cache, allowing Safari to load and execute the (self-signed)
meterpreter payload.
msf > use exploit/apple_ios/browser/webkit_createthis
msf exploit(webkit_createthis) > show targets
...targets...
msf exploit(webkit_createthis) > set TARGET < target-id >
msf exploit(webkit_createthis) > show options
...show and set options...
msf exploit(webkit_createthis) > exploit
Vulmon