coredumps disallowed when creds are changed?

[Ravi Pokala]

Greetings hackers.

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?

Thanks,

Ravi (rpokala@)

[Eugene Grosbein]

Post by Ravi Pokala
Greetings hackers.

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.

[Ravi Pokala]

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

Post by Eugene Grosbein

Post by Ravi Pokala
Greetings hackers.

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@)