[Bug 1624071] Re: libnss-resolve: Fallback from resolve to dns breaks DNSSEC validation

[Anders Kaseorg]

** Description changed:

  The libnss-resolve postinst script inserts ‘resolve’ before ‘dns’ in the
  hosts line of /etc/nsswitch.conf.  This makes DNSSEC validation
  impossible, even with DNSSEC=yes in /etc/systemd/resolved.conf, because
  if libnss_resolve returns a validation failure, glibc will simply fall
  back to libnss_dns.  It also makes NXDOMAIN lookups twice as slow.
- 
- The following syntax would preserve the fallback in the case that
- systemd-resolved is not running at all, but allow systemd-resolved to
- fail lookups that should fail when it is running:
- 
- hosts:          files resolve [!TRYAGAIN=return] dns

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/1624071

Title:
  libnss-resolve: Fallback from resolve to dns breaks DNSSEC validation

Status in systemd package in Ubuntu:
  Triaged

Bug description:
  The libnss-resolve postinst script inserts ‘resolve’ before ‘dns’ in
  the hosts line of /etc/nsswitch.conf.  This makes DNSSEC validation
  impossible, even with DNSSEC=yes in /etc/systemd/resolved.conf,
  because if libnss_resolve returns a validation failure, glibc will
  simply fall back to libnss_dns.  It also makes NXDOMAIN lookups twice
  as slow.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1624071/+subscriptions