mirror of
https://github.com/idapython/src
synced 2026-06-08 14:47:00 +00:00
Arnaud Diederen
75 lines
3.0 KiB
Markdown
75 lines
3.0 KiB
Markdown
Overview
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========
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This document describes the IDAPython linking process used on Apple Silicon Macs.
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Motivation
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==========
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Since IDAPython must be compatible with different Python versions, we must provide the user with
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a mechanism to easily switch between them. Traditionally the approach on Mac was to have the
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idapyswitch utility patch the libpython load commands in all of IDAPython's modules.
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However this gets us into trouble on Apple Silicon, because codesigning rules are strictly enforced.
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If we patch a dylib binary in IDA's installation, its code signature is invalidated and macOS will
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refuse to load it (not only that, but the process is immediately killed).
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We must be able to switch between various Python versions _without_ modifying IDA's binaries.
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TBD Files
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=========
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This is where .tbd files can help us.
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A .tbd file is a stub library that can be used in place of a real dylib. It is essentially just a text file
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that describes the contents of a given library - e.g. the target arch, all exported symbols, and (most importantly)
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the library's install name.
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This allows us to configure the libpython install name used when our IDAPython binaries are linked, so that they
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point to a symlink for libpython instead of the real libpython binary. Thus, it is trivial to switch between
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different Python versions because need only to modify the symlink target, and all of IDAPython's modules can
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remain untouched.
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Generating TBD Files
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====================
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.tbd files can be generated using the 'tapi' utility on macOS. It is usually found here:
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/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/tapi
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For example, this is how you can recreate libpython3.tbd:
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$ alias tapi='/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/tapi'
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$ cp /Library/Frameworks/Python.framework/Versions/3.9/Python /tmp/
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$ tapi stubify /tmp/Python
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$ mv /tmp/Python.tbd ~/idasrc/current/plugins/idapython/libpython3.tbd
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Then replace the following line:
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install-name: '/Library/Frameworks/Python.framework/Versions/3.9/Python'
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With:
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install-name: '@executable_path/libpython3.link.dylib'
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Note that the libpython3.link.dylib symlink will be created by idapyswitch at idapython build time
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(see TBD_MODULE_DEP in idapython/makefile and pyver_tool_t::do_apply_version() in idapyswitch_mac.cpp).
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It is also a good idea to clean up the .tbd file by removing all config directives that aren't
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absolutely necessary. This makes it more likely that the .tbd file will continue to be compatible
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with newer versions of the macOS linker (no surprise, the format is really unstable).
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So far it seems that only the following options are required:
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--- !tapi-tbd
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tbd-version: 4
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targets: [ arm64-macos, x86_64-macos ]
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install-name: '@executable_path/libpython3.link.dylib'
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current-version: 3.9
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compatibility-version: 3.9
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exports:
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- targets: [ arm64-macos, x86_64-macos ]
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symbols: [ _PyAST_CompileEx, ...
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Everything else can be removed.
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