[Bug 1832672] Re: systemd-resolve not ignoring comments in /etc/hosts

[Dan Streetman]

ubuntu at lp1832672-b:~$ dpkg -l systemd|grep ii
ii  systemd        237-3ubuntu10.31 amd64        system and service manager
ubuntu at lp1832672-b:~$ grep bar /etc/hosts
127.0.2.1 foo # bar
ubuntu at lp1832672-b:~$ systemd-resolve -4 bar
bar: 127.0.2.1

-- Information acquired via protocol DNS in 1.9ms.
-- Data is authenticated: yes


ubuntu at lp1832672-b:~$ dpkg -l systemd|grep ii
ii  systemd        237-3ubuntu10.33 amd64        system and service manager
ubuntu at lp1832672-b:~$ grep bar /etc/hosts
127.0.2.1 foo # bar
ubuntu at lp1832672-b:~$ systemd-resolve -4 bar
bar: resolve call failed: 'bar' not found


** Tags removed: verification-needed verification-needed-bionic
** Tags added: verification-done verification-done-bionic

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https://bugs.launchpad.net/bugs/1832672

Title:
  systemd-resolve not ignoring comments in /etc/hosts

Status in systemd:
  Unknown
Status in systemd package in Ubuntu:
  Fix Released
Status in systemd source package in Bionic:
  Fix Committed

Bug description:
  [impact]

  resolved does not ignore comments properly in /etc/hosts

  [test case]

  see original description below

  [regression potential]

  as this modifies resolved parsing of /etc/hosts, regressions would
  likely be in hostname lookups from hosts in /etc/hosts, or failure(s)
  to parse /etc/hosts correctly.

  [other info]

  original description:
  ---

  
  $ lsb_release -rd
  Description:	Ubuntu 18.04.2 LTS
  Release:	18.04

  $ LANG=C apt-cache policy systemd
  systemd:
    Installed: 237-3ubuntu10.22
    Candidate: 237-3ubuntu10.22
    Version table:
   *** 237-3ubuntu10.22 500
          500 http://ch.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
          100 /var/lib/dpkg/status
       237-3ubuntu10.19 500
          500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
       237-3ubuntu10 500
          500 http://ch.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
          500 http://mirrors.kernel.org/ubuntu bionic/main amd64 Packages

  $ head -1 /etc/hosts
  127.0.2.1 foo # bar

  $ /usr/bin/systemd-resolve -4 bar

  expected
  ----------
  bar: resolve call failed: 'bar' not found

  What happened instead
  ---------------------
  bar: 127.0.2.1

  HOSTS(5)
  > Text from a "#" character until the end of the line is a comment, and is ignored.

  This is fixed in upstream:
  https://github.com/systemd/systemd/issues/10779
  https://github.com/systemd/systemd/commit/bd0052777981044cf54a1e9d6e3acb1c3d813656

  Please backport to current LTS version.
  I accidentally connected to wrong systems because of this bug.

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