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Enable debugging any App's WebView on MacOS

This is a PoC to enable debugging WebView in any App, by patching WebInspect the dylib regulating which App can be debugged by Safari.

The idea is to tweak method -[RWIRelayDelegateMac _allowApplication:bundleIdentifier:] to always return TRUE.

As notice from the disassembled flow diagram, function isProxyApplication is one of the judgement conditions. Moreover, from the opcodes, we see bl is set before test, so we can change test al, al to test bl, bl.

Flow diagram

Just get it done by patching opcode 84 CO to 84 DB. However, the location of this opcode may vary in different OS versions. In this example is 0x6daaf.

opcode

How to use

First of all, disable SIP (System Integrity Protection), otherwise, task_for_pid won't work.

Warning! disabling SIP is at your own risk, you should make sure your environment is safe by yourself.

  1. Drag WebInspector into your favorite disassembler (IDA, Hopper, etc.) and analyze, the path is as below.
/System/Library/PrivateFrameworks/WebInspector.framework/Versions/A/WebInspector

By searching _allowApplication, you can locate the method -[RWIRelayDelegateMac _allowApplication:bundleIdentifier:], where you can find the opcodes to test for isProxyApplication's result, as the second image shown above.

Or you can get the address with lldb:

# start safari
lldb -p $(pgrep webinspectord)

In lldb run the following:

image lookup -v -r -s "allowApplication"
# get the adress from range range = [0x00007ff927e6692f-0x00007ff927e669d5)
disass -s 0x00007ff927e6692f -c 50
# find the correct address and subtract current aslr_offset

Open main.m, scroll to the last line of code, change the visual memory address 0x6c660 to that you see on your disassembler/debugger.

patch_mem(remoteTask, aslr_offset+0x6c660, sizeof(unsigned short), 0xc084, 0xdb84);
  1. In your terminal, compile it with make command
$ make
  1. Open Safari.app, run with sudo privilege
$ sudo ./patchwebinspect

If the program gives a successful prompt, then you can debug any WebView. This program only patchs memory, so each time Safari relaunches, the effect is gone, and need to re-patch. The following images show WeChat's WebView can be debugged after patched.

WeChat 1

WeChat 2

MIT License

Copyright (c) 2019 zwo

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.