Bug#870638: systemd: /var/log/btmp has inconsistent permissions

[Mark Charter]

Package: systemd
Version: 232-25+deb9u1
Severity: normal

Dear Maintainer,

When /var/log/btmp is created at installation (by
/var/lib/dpkg/info/base-files.postinst) its permissions are 0660
(u=rw,g=rw,o=).  When it is (re)created by log file rotation (in
/etc/logrotate.conf) its permissions are also 0660.  But if it is
created by systemd, or after a reboot, its permissions (from
/usr/lib/tmpfiles.d/var.conf) are 0600.  So its permissions can change
with time, and they often change across a reboot.

I suggest that the three sources of file permissions should be made
consistent, for example by changing the permissions in
/usr/lib/tmpfiles.d/var.conf from

f /var/log/btmp 0600 root utmp -

to

f /var/log/btmp 0660 root utmp -

-- Package-specific info:

-- System Information:
Debian Release: 9.1
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.9.0-3-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_GB.utf8, LC_CTYPE=en_GB.utf8 (charmap=UTF-8), LANGUAGE=en_GB:en (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
ii  libaudit1       1:2.6.7-2
ii  libblkid1       2.29.2-1
ii  libc6           2.24-11+deb9u1
ii  libcap2         1:2.25-1
ii  libcryptsetup4  2:1.7.3-4
ii  libgcrypt20     1.7.6-2+deb9u1
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
ii  libpam0g        1.1.8-3.6
ii  libseccomp2     2.3.1-2.1
ii  libselinux1     2.6-3+b1
ii  libsystemd0     232-25+deb9u1
ii  mount           2.29.2-1
ii  procps          2:3.3.12-3
ii  util-linux      2.29.2-1

Versions of packages systemd recommends:
ii  dbus            1.10.18-1
ii  libpam-systemd  232-25+deb9u1

Versions of packages systemd suggests:
ii  policykit-1        0.105-18
pn  systemd-container  <none>
pn  systemd-ui         <none>

Versions of packages systemd is related to:
pn  dracut           <none>
ii  initramfs-tools  0.130
ii  udev             232-25+deb9u1

-- Configuration Files:
/etc/systemd/logind.conf changed [not included]

-- no debconf information