Bug#912525: systemd: nobody group is created by systemd-sysusers automatically

[Keh-Ming Luoh]

Package: systemd
Version: 239-11~bpo9+1
Severity: normal
Tags: patch

Dear Maintainer,

When I upgrade my systemd, I found there is a "nobody" group created
automatically.
I was wondering what caused that.
After tracing down the behavior, I figured out the following line in
/usr/lib/sysusers.d/basic.conf triggered it.

  "u nobody     65534   - /nonexistent         /usr/sbin/nologin"

Then I started to trace code from
https://salsa.debian.org/systemd-team/systemd.git

I think there is a bug in debian/extra/make-sysusers-basic 

Skipping the GID when generating basic.conf may cause the above
behavior.

BR,
-KM

-- Package-specific info:

-- System Information:
Debian Release: 9.5
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.9.0-8-amd64 (SMP w/6 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages systemd depends on:
ii  adduser         3.115
ii  libacl1         2.2.52-3+b1
ii  libapparmor1    2.11.0-3+deb9u2
ii  libaudit1       1:2.6.7-2
ii  libblkid1       2.29.2-1+deb9u1
ii  libc6           2.24-11+deb9u3
ii  libcap2         1:2.25-1
ii  libcryptsetup4  2:1.7.3-4
ii  libgcrypt20     1.7.6-2+deb9u3
ii  libgnutls30     3.5.8-5+deb9u3
ii  libgpg-error0   1.26-2
ii  libidn11        1.33-1
ii  libip4tc0       1.6.0+snapshot20161117-6
ii  libkmod2        23-2
ii  liblz4-1        0.0~r131-2+b1
ii  liblzma5        5.2.2-1.2+b1
ii  libmount1       2.29.2-1+deb9u1
ii  libpam0g        1.1.8-3.6
ii  libseccomp2     2.3.1-2.1
ii  libselinux1     2.6-3+b3
ii  libsystemd0     239-11~bpo9+1
ii  mount           2.29.2-1+deb9u1
ii  procps          2:3.3.12-3+deb9u1
ii  util-linux      2.29.2-1+deb9u1

Versions of packages systemd recommends:
ii  dbus            1.10.26-0+deb9u1
ii  libpam-systemd  239-11~bpo9+1

Versions of packages systemd suggests:
ii  policykit-1        0.105-18
ii  systemd-container  239-11~bpo9+1

Versions of packages systemd is related to:
pn  dracut           <none>
ii  initramfs-tools  0.130
ii  udev             232-25+deb9u4

-- no debconf information
-------------- next part --------------
>From e29915221cfbe90f393d1139ee27036b73ed37a3 Mon Sep 17 00:00:00 2001
From: Keh-Ming Luoh <kmluoh at ubnt.com>
Date: Wed, 31 Oct 2018 19:07:29 -0700
Subject: [PATCH] don't skip gid even it's the same as uid, or nobody group
 will be created automatically

---
 debian/extra/make-sysusers-basic | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/debian/extra/make-sysusers-basic b/debian/extra/make-sysusers-basic
index 0aaa65cc5c..c70ebd30d6 100755
--- a/debian/extra/make-sysusers-basic
+++ b/debian/extra/make-sysusers-basic
@@ -14,4 +14,4 @@ done < /usr/share/base-passwd/group.master
 
 echo
 
-awk -F:  '{ i = ($3 == $4) ? $3 : $3":"$4; printf("u %-10s %-7s - %-20s %s\n", $1,i,$6,$7) }'  < /usr/share/base-passwd/passwd.master
+awk -F:  '{ i = $3":"$4; printf("u %-10s %-7s - %-20s %s\n", $1,i,$6,$7) }'  < /usr/share/base-passwd/passwd.master
-- 
2.11.0

-------------- next part --------------
>From e29915221cfbe90f393d1139ee27036b73ed37a3 Mon Sep 17 00:00:00 2001
From: Keh-Ming Luoh <kmluoh at ubnt.com>
Date: Wed, 31 Oct 2018 19:07:29 -0700
Subject: [PATCH] don't skip gid even it's the same as uid, or nobody group
 will be created automatically

---
 debian/extra/make-sysusers-basic | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/debian/extra/make-sysusers-basic b/debian/extra/make-sysusers-basic
index 0aaa65cc5c..c70ebd30d6 100755
--- a/debian/extra/make-sysusers-basic
+++ b/debian/extra/make-sysusers-basic
@@ -14,4 +14,4 @@ done < /usr/share/base-passwd/group.master
 
 echo
 
-awk -F:  '{ i = ($3 == $4) ? $3 : $3":"$4; printf("u %-10s %-7s - %-20s %s\n", $1,i,$6,$7) }'  < /usr/share/base-passwd/passwd.master
+awk -F:  '{ i = $3":"$4; printf("u %-10s %-7s - %-20s %s\n", $1,i,$6,$7) }'  < /usr/share/base-passwd/passwd.master
-- 
2.11.0