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0 pointsnrdvana1y ago0 comments

The real security flaw is extracting a value from a process's own memory to identify what the process is. If you want a secure way to identify what a process is and where it came from, that needs to be a new feature in the OS.

argv[0] was designed to be part of the arguments to the program, and it succeeds perfectly at that task. The problem is that it has been abused by external tools as a way to identify the program just because there was no other alternative.

It has to be writable because the entire argv string (in program memory) is writable and declared as

  int main(int argc, char **argv)

not

  int main(int argc, const char **argv)

and needs to preserve back-compat. Classic C code might be calling strtok on the arguments, so that block of memory needs to remain writable.

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Joker_vD1y ago

> The real security flaw is extracting a value from a process's own memory to identify what the process is. If you want a secure way to identify what a process is and where it came from, that needs to be a new feature in the OS.

How would that help? After all, even if this info comes from the OS, the decision logic still lives in your process's memory which the parent process still has full access to.

gwbas1c1y ago

Take a closer look at the exploits listed, they all have to do with malware manipulating argv[0] when creating a new process; not with a process manipulating argv after it starts.

There is no mention of mutable memory attacks.

(If I was on a computer I'd fire up a C IDE to even see what happens when I mutate argv. I suspect the OS keeps its own copy of what the process was started with.)

Zironic1y ago

It's not about mutable memory attacks, it's about not understanding the purpose of argv[0]. argv[0] is an argument, you are supposed to be able to set it to whatever you want. You are not supposed to rely on an argument to identify a program, that is nonsensical.

The problem here isn't argv[0], the problem is security software not understanding what argv[0] is and if you want security software to better be able to identify processes, the solution isnt changing argv[0], it's implementing an actual process ID checking.

thayne1y ago

> it has been abused by external tools as a way to identify the program just because there was no other alternative.

There is an alternative, at least on linux: /proc/$pid/exe.

And if your question is "what executable is running" that is a better way to get it. But for a program like busybox, argv[0] is also important.

account421y ago

Pretty much any OS lets you examine which binaries have been mapped into the process adddress space meaning there are plenty alternatives.

rerdavies1y ago

It's simply a case of "Do use argv[0] for this, and don't use it for THAT.

Both Windows and Linux provide APIs to get the actual path of the executable. Posix, to the best of my knowledge, does not. Regrettably. And the Linux API is, admittedly, a bit weird. But not that difficult really. Nothing that you can't get Claude to spit out for you in under 45 seconds. ;-P

The contents of argv[0] are yours to use and abuse as you see fit. Operating systems don't know or care if you go trampling recklessly through the contents of argv[0].

And the authors contention that "power --shutdown" and "power --reboot" are viable alternatives to "shutdown" and "reboot" seems.... disingenuous. Is the politest word I can come up with.

And, if you haven't asked yourself, "wait a second, what happens if somebody passes me garbage via execve" before you are halfway through writing the substantial amount of code required to portably normalize argv[0] to an executable path, I don't think you can be trusted to write secure code of any form. Just normalizing the various forms of argv[0] that a Linux shell passes you is a non-trivial effort. So don't use it for THAT.

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