NetBSD Problem Report #55764

From kimmo@suominen.org  Thu Oct 29 07:03:08 2020
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Message-Id: <20201029070302.47A0D1B737@equinoxe.x.gw.fi>
Date: Thu, 29 Oct 2020 09:03:02 +0200 (EET)
From: kim@netbsd.org (Kimmo Suominen)
To: gnats-bugs@NetBSD.org
Subject: per_user_tmp=YES not really usable
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>Number:         55764
>Category:       security
>Synopsis:       per_user_tmp=YES not really usable
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    security-officer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Oct 29 07:05:00 +0000 2020
>Originator:     Kimmo Suominen
>Release:        NetBSD 9.1
>Organization:
>Environment:
System: NetBSD equinoxe.x.gw.fi 9.1 NetBSD 9.1 (GENERIC) #0: Sun Oct 18 19:24:30 UTC 2020 mkrepro@mkrepro.NetBSD.org:/usr/src/sys/arch/amd64/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:

	When using per_user_tmp=YES the /private/tmp/@ruid target is
	only created if a program calls setusercontext(3). This leaves
	programs that call setuid(2) (often followed by setgid(2) and
	initgroups(3)) without a /tmp directory, making various things
	fail (e.g. vi(1) needs /tmp).

>How-To-Repeat:

	Try using any of the following from pkgsrc:

	- security/doas (fixed in doas-6.2p4nb3, where I switched it to
	  using setusercontext(3))

	- security/priv (waiting for the package maintaner to reply to
	  email; https://www.netbsd.org/~kim/priv-setusercontext.diff
	  has a proposed fix)

	- security/sudo (the code was too convoluted for a quick patch)

>Fix:

	I know some people like to run "sudo su" -- this would be one
	reason to use it...

	It would be nice if the /private/tmp/@ruid target was created by
	some magic that made it work for setuid(2) as well.

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