36 lines
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1.9 KiB
Text
36 lines
No EOL
1.9 KiB
Text
io_hideventsystem is a MIG service which provides proxy access to various HID devices for untrusted
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clients. On iOS it's hosted by backboardd and on MacOS by hidd. The actual implementation is
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in IOKit.framework.
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I, and also pangu jailbreak team, had previously found a few bugs in the kernel IODataQueue code.
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It seems that io_hideventsystem also uses IODataQueues purely in userspace. That is, via shared
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memory between two userspace processes rather than between a userspace process and the kernel.
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It turns out that the userspace code for enqueuing and dequeuing from an IODataQueue has none
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of the hardening that the kernel code now has, so it's trivial to just replace the length, head
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and tail fields (which are in a header at the start of the shared memory buffer) such that
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the remote process tries to enqueue outside of the bounds of the IODataQueue's actual backing
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buffer.
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This is a very basic PoC thrown together to minimally repro the issue.
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Run build.sh and run.sh, use the mouse a bit and notice the hidd crash log. Don't try to attach lldb to hidd, you will
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struggle to interact with it!
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Specifically the server will allocate a buffer wrapped by a mach port (via mach_make_memory_entry_64)
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then in the client you can see inside IOHIDEventQueueCreateWithVM the port's memory being mapped.
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The attached dylib just interposes mach_vm_map to replace the size and tail fields once the shared
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memory is mapped in the client.
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I've also tested this on iOS just manually manipulating the shared memory after it's mapped.
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Depending on how clients use io_hideventsystem it might be possible to hop first in to backboardd
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then in to another client (if that client is also enqueuing events into a queue) but that will
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take some more research.
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Tested on MacOS 10.13.6 and iOS 11.3.1 (that's the highest version I have on a device with me right now.)
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Proof of Concept:
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https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/45648.zip |