Dynamic attaching to process

[catap]

Hey,

strace for example can dynamic attach to process and trace it. I think we can do same over ptrace and some magic :)

[ronaldtse]

@catap we're all eager to see magic 👍

[erikbor]

@catap, please take into account multi platform support for this (e.g.: *BSD's and macOS). Cheers.

[pablo-mendoza]

This would be pretty hard to do with our current approach (shared library). We would need to basically force the dynamic linker to re link everything. I'm thinking it could somehow be done in Linux, not sure about about the other platforms and it we can it would be pretty platform specific code.

[pablo-mendoza]

For linux see man dl_iterate_phdr

[catap]

@riataman or we can do it over ptrace. I did a littel googling and found this: https://stackoverflow.com/questions/24355344/inject-shared-library-into-a-process

Anyway, I have no idea how it's possible on *BSD. For macOS I have idea try to use dtrace, but I'm not sure.

[drystone]

@catap, @riataman I think there is more to it than loading the shared library beacause the function pointers in the ELFs GOT will already have been fixed up to the functions in the shared libraries at load time. I guess it would be possible to locate the GOT and reset the pointers to the fixup routines and you'd need to do that for all the shared libraries too. Not impossible but not straigtforward either.

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On Wed, Jul 12, 2017 at 02:55:28AM -0700, Kirill A. Korinsky wrote: @riataman or we can do it over ptrace. I did a littel googling and found this: https://stackoverflow.com/questions/24355344/ inject-shared-library-into-a-process Anyway, I have no idea how it's possible on *BSD. For macOS I have idea try to use dtrace, but I'm not sure. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.*

[pablo-mendoza]

@catap are you taking a crack at this? Otherwise I'd like to give this a go.

[catap]

@riataman it's yours :)

[erikbor]

@riataman is this still something you want to work on?

[pablo-mendoza]

Well, I looked at this for a while but never found a solution I was happy with. I made some tests works but those required to use gdb to inject into the running process.

There was another option of manually injecting the so, but that required very platform dependant asm code for each OS/architecture.

I would have been happy if there was a libgdb that I could use, but something like that was abandoned by the gdb developers many moons ago.

Long story short, if someone wants to give this a shoot feel free to do so.

[erikbor]

@riataman Thanks for the update

[ronaldtse]

@catap would you be able to work your magic on this? 😉