Bug 700930

Summary:	dev-lang/erlang: epmd default conf.d file allows killing service by every user
Product:	Gentoo Security	Reporter:	Hanno Böck <hanno>
Component:	Default Configs	Assignee:	Gentoo Security <security>
Status:	RESOLVED FIXED
Severity:	enhancement	CC:	slyfox
Priority:	Normal
Version:	unspecified
Hardware:	All
OS:	Linux
Whiteboard:
Package list:		Runtime testing required:	---

Description Hanno Böck gentoo-dev

2019-11-22 11:17:55 UTC

The conf.d/epmd default file starts epmd with the parameter "-relaxed_command_check".

This effectively means that a user can take down any erlang-based service, as one can send the kill command (with epmd -kill or by directly sending the appropriate command to the TCP port) [1].
If this is not passed then epmd can only be killed if no service is using it. (Unfortunately it seems not allowing to kill epmd by any user is not a considered scenario.)

It seems to me this is a dangerous default configuration and this shouldn't be enabled by default. I recommend we remove it from the conf.d file installed by default (and maybe add a comment pointing out the potential risk).


[1] http://erlang.org/doc/man/epmd.html

Comment 1 Larry the Git Cow gentoo-dev

2019-11-22 13:59:41 UTC

The bug has been referenced in the following commit(s):

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=118840a378b33af02851ba097c08fcb0f93cda98

commit 118840a378b33af02851ba097c08fcb0f93cda98
Author:     Sergei Trofimovich <slyfox@gentoo.org>
AuthorDate: 2019-11-22 13:59:20 +0000
Commit:     Sergei Trofimovich <slyfox@gentoo.org>
CommitDate: 2019-11-22 13:59:35 +0000

    dev-lang/erlang: drop -relaxed_command_check from defaults
    
    Reported-by: Hanno Böck
    Bug: https://bugs.gentoo.org/700930
    Package-Manager: Portage-2.3.79, Repoman-2.3.18
    Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

 dev-lang/erlang/erlang-22.1.8-r1.ebuild | 150 ++++++++++++++++++++++++++++++++
 dev-lang/erlang/files/epmd.confd-r2     |   2 +
 2 files changed, 152 insertions(+)