units: turn off DNSSEC validation when timesyncd resolves hostnames

We have a chicken and egg problem: validation of DNSSEC signatures
doesn't work without a correct clock, but to set the correct clock we
need to contact NTP servers which requires resolving a hostname, which
would normally require DNSSEC validation.

Let's break the cycle by excluding NTP hostname resolution from
validation for now.

Of course, this leaves NTP traffic unprotected. To cover that we need
NTPSEC support, which we can add later.

Fixes: #5873 #15607
This commit is contained in:
Lennart Poettering 2020-11-05 11:20:32 +01:00
parent aee9d18c8d
commit abf4e5c1d3

View file

@ -22,6 +22,10 @@ Wants=time-set.target
AmbientCapabilities=CAP_SYS_TIME
BusName=org.freedesktop.timesync1
CapabilityBoundingSet=CAP_SYS_TIME
# Turn off DNSSEC validation for hostname look-ups, since those need the
# correct time to work, but we likely won't acquire that without NTP. Let's
# break this chicken-and-egg cycle here.
Environment=SYSTEMD_NSS_RESOLVE_VALIDATE=0
ExecStart=!!@rootlibexecdir@/systemd-timesyncd
LockPersonality=yes
MemoryDenyWriteExecute=yes