coredumps disallowed when creds are changed?

[Ravi Pokala]

-----Original Message-----
From: Eugene Grosbein <eugen at grosbein.net>
Date: 2018-10-08, Monday at 15:33
To: Ravi Pokala <rpokala at freebsd.org>, "freebsd-hackers at freebsd.org" <freebsd-hackers at freebsd.org>
Subject: Re: coredumps disallowed when creds are changed?

> 09.10.2018 4:31, Ravi Pokala wrote:
> 
>> Greetings hackers.
>> 
>> core(5) states:
>> 
>>> By default, a process that changes user or group credentials
>>> whether real or effective will not create a corefile.
>>> This behaviour can be changed to generate a core dump by setting the sysctl(8) variable kern.sugid_coredump to 1.
>> 
>> Can someone explain why?
> 
> Real/effective user/group id often are changed for a process started
> by non-privilegied user running set[ug]id binary like csh/chpass/passwd(1)
> that can read sensitive system data similar to /etc/master.passwd
> containing password hashes. If such utility reads sensitive data
> and then crashes due to a bug, its coredump may leak data to unexpected places
> of file system like /home partition, then go to a dump/backup of file system,
> get uploaded offsite as part of backup etc. That should not happen by default.

That makes perfect sense. Thanks Eugene!

-Ravi (rpokala@)