Re: Howto strace apache as nobody/apache user?

[Peter Kosinar <goober () ksp sk>]

Hello,

> into many process after leaving its root credentials, usually being
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= calling some variant of setuid()/setgid()

> Is this a security feature of apache or what?

No, this is not Apache-specific. At least on Linux, calling set[ug]id() 
turns off the so-called "dumpable" flag for the process. As a regular 
user, you can only ptrace (that's the syscall used by strace) processes 
which have this flag turned on (naturally, you also need to have the same 
[ug]id as the process you're wanting to trace). If you are root or have 
the CAP_SYS_PTRACE capability, these restrictions don't apply.

Another example -- if you're using an OpenSSH sshd with privilege 
separation turned on, you should see two sshd processes associated with 
every connection; one of them running as root, the other one as the user. 
Still, you can't trace neither the first, nor the second because of 
aforementioned criteria.

Peter

--
[Name] Peter Kosinar   [Quote] 2B | ~2B = exp(i*PI)   [ICQ] 134813278



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