/etc/apparmor.d/abstractions/nameservice is in apparmor 2.7.102-0ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#
#    Copyright (C) 2002-2009 Novell/SUSE
#    Copyright (C) 2009-2011 Canonical Ltd.
#
#    This program is free software; you can redistribute it and/or
#    modify it under the terms of version 2 of the GNU General Public
#    License published by the Free Software Foundation.
#
# ------------------------------------------------------------------
  # Many programs wish to perform nameservice-like operations, such as
  # looking up users by name or id, groups by name or id, hosts by name
  # or IP, etc. These operations may be performed through files, dns,
  # NIS, NIS+, LDAP, hesiod, wins, etc. Allow them all here.
  /etc/group              r,
  /etc/host.conf          r,
  /etc/hosts              r,
  /etc/nsswitch.conf      r,
  /etc/gai.conf           r,
  /etc/passwd             r,
  /etc/protocols          r,
  /etc/resolv.conf        r,
  # on systems using resolvconf, /etc/resolv.conf is a symlink to
  # /{,var/}run/resolvconf/resolv.conf and a file sometimes referenced in
  # /etc/resolvconf/run/resolv.conf
  /{,var/}run/resolvconf/resolv.conf r,
  /etc/resolvconf/run/resolv.conf r,
  /etc/samba/lmhosts      r,
  /etc/services           r,
  # db backend
  /var/lib/misc/*.db      r,
  # The Name Service Cache Daemon can cache lookups, sometimes leading
  # to vast speed increases when working with network-based lookups.
  /{,var/}run/.nscd_socket   rw,
  /{,var/}run/nscd/socket    rw,
  /var/{db,cache,run}/nscd/{passwd,group,services,host}    r,
  # nscd renames and unlinks files in it's operation that clients will
  # have open
  /{,var/}run/nscd/db*  rmix,
  # The nss libraries are sometimes used in addition to PAM; make sure
  # they are available
  /lib{,32,64}/libnss_*.so*      mr,
  /usr/lib{,32,64}/libnss_*.so*  mr,
  /lib/@{multiarch}/libnss_*.so*      mr,
  /usr/lib/@{multiarch}/libnss_*.so*  mr,
  /etc/default/nss               r,
  # avahi-daemon is used for mdns4 resolution
  /{,var/}run/avahi-daemon/socket w,
  # nis
  #include <abstractions/nis>
  # ldap
  #include <abstractions/ldapclient>
  # winbind
  #include <abstractions/winbind>
  # likewise
  #include <abstractions/likewise>
  # mdnsd
  #include <abstractions/mdns>
  # kerberos
  #include <abstractions/kerberosclient>
  # TCP/UDP network access
  network inet  stream,
  network inet6 stream,
  network inet  dgram,
  network inet6 dgram,
  # interface details
  @{PROC}/*/net/route r,
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