Is it possible to 'hide' a process from the listing of `ps` or `top` on Linux

Question

First, I presume that if this is possible it would need to be done as root (or as a user who shares root's UID of 0).

How can a process be launched so that it does not show up in a ps aux or ps ef or top listing if the command is run by non-root?

Is this even possible?

The distributions I typically run are RHEL/CentOS and Ubuntu - so if there is a distro-specific answer, that's ok, too.

Solution 1

Well, you have a couple of options here. Taking the easy way out would be to swap the ps and top programs out with modified versions that hide what it is you want to hide.

The alternative would be to run your code embedded in an existing process, or write a wrapper-script around your code with an innocuous name.

In some versions of PS, you can modify it by changing argv[], but not sure if that works for top, and not sure if it works in linux (It's mainly a BSD convention).

It all depends, on exactly what you are looking to achieve by doing this?

Solution 2

According to kernel patch http://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=0499680a42141d86417a8fbaa8c8db806bea1201, you can use the hidepid option for the proc filesystem:

hidepid=0 (default) means the old behavior - anybody may read all world-readable /proc/PID/* files.

hidepid=1 means users may not access any /proc// directories, but their own. Sensitive files like cmdline, sched*, status are now protected against other users. As permission checking done in proc_pid_permission() and files' permissions are left untouched, programs expecting specific files' modes are not confused.

hidepid=2 means hidepid=1 plus all /proc/PID/ will be invisible to other users. It doesn't mean that it hides whether a process exists (it can be learned by other means, e.g. by kill -0 $PID), but it hides process' euid and egid. It compicates intruder's task of gathering info about running processes, whether some daemon runs with elevated privileges, whether another user runs some sensitive program, whether other users run any program at all, etc.

gid=XXX defines a group that will be able to gather all processes' info (as in hidepid=0 mode). This group should be used instead of putting nonroot user in sudoers file or something. However, untrusted users (like daemons, etc.) which are not supposed to monitor the tasks in the whole system should not be added to the group.

You are not able to control the visibility on process level however you can ensure that your users can see their own processes only.

In case you have kernel version greater than 3.3 you can make a try with the following command:

 
mount /proc -o remount,hidepid=2

Solution 3

The option described in this link worked for me. In that link, the author is hiding a process called evil_script.py.

I'm pasting the content here just in case the link goes down:

1. First, create a file named processhider.c with the content found in this link: processhider.c

2. Compile the code with:

   gcc -Wall -fPIC -shared -o libprocesshider.so processhider.c -ldl

3. Move the library with:

   sudo mv libprocesshider.so /usr/local/lib/

4. Tell the dynamic linker to use it:

   echo /usr/local/lib/libprocesshider.so >> /etc/ld.so.preload

That is it. If you now run ps faux you won't see any process called evil_script.py.

Comments

[Admin]

warren: Ever find a solution to this?

[Admin]

@Chris - nope... @fianchetto's answer seems to be the only route, and that's a lot more work than I'm comfortable undertaking :-|

[Admin]

I am going to undertake this project and will report back with anything I determine.

[David Yates]

my goal here is for processes spawned by root to not be visible to all users (perhaps security-related daemons or similar)

[Brōtsyorfuzthrāx]

@flanchetto So, are you saying if I have a program that is already running and it later runs a command-line command with a password in it in the same process that the password will be securely given? e.g. run python myScript.py and all the subprocess.Popen commands (which may or may not contain passwords) are not shown, as long as it's the same process?

[Brōtsyorfuzthrāx]

Can you limit the hidepid=2 thing so it only affects specific users (or so it whitelists certain users)?

[Brōtsyorfuzthrāx]

Anyway, that doesn't work (I just tried it and saw the password). So, I'm assuming you mean something else. Feel free to clarify. :)

[lepe]

Works great! My problem was that I'm connecting to a server using a cron script and any user was able to see the credentials using "htop" (for example). Setting to "hidepid=2" users can not see processes launched by other users which is what I was looking for. Why is not set by default?

[David Yates]

That only hides something in my view

[Florian Wendelborn]

@lepe probably for legacy reasons. Would break this and that and therefore can't (yet) be used everywhere.

[phil294]

OP asked for the pid to be invisible in overall, not just to other users ...?

[Avery235]

Is there a way to hide processes created by certain users only? eg. root?