Public bug reported:
My client has 200+ devices automatically uploading information via sftp
and scp to a server every few minutes. After a recent update, I noticed
the load on their server spiking through the roof. Upon investigation, I
discovered a horde of landscape-sysinfo and /usr/bin/lsb_release
processes running that correlated with login session notifications in
/etc/syslog and the load spikes.
It appears that even in non-interactive sessions where this information
will never be seen, the configuration options below in /etc/pam.d/sshd
cause these items to be launched (in fact, probably everything in /etc
/update-motd.d). This only started on the system in question after a
recent set of system updates were in stalled.
The content of /etc/update-motd.d/* really, really, really shouldn't be
executed if the session in question is not interactive, as it provides
no value at all. Unfortunately, to disable it for these non-interactive
sessions, we also have to disable it for the interactive ones as well
where it has some value (though not enough to make spiking the load on
this server through the roof an acceptable tradeoff).
# Print the message of the day upon successful login.
# This includes a dynamically generated part from /run/motd.dynamic
# and a static (admin-editable) part from /etc/motd.
#session optional pam_motd.so motd=/run/motd.dynamic
#session optional pam_motd.so noupdate
Also, looking at the script 00-header in /etc/update-motd.d/,
/usr/bin/lsb_release is being improperly launched, as /etc/lsb_release
does include the necessary information:
[ -r /etc/lsb-release ] && . /etc/lsb-release
if [ -z "$DISTRIB_DESCRIPTION" ] && [ -x /usr/bin/lsb_release ]; then
# Fall back to using the very slow lsb_release utility
DISTRIB_DESCRIPTION=$(lsb_release -s -d)
fi
# cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=16.04
DISTRIB_CODENAME=xenial
DISTRIB_DESCRIPTION="Ubuntu 16.04.7 LTS"
** Affects: openssh (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1893716
Title:
scripts in /etc/update-motd.d/ run even on login via non-interactive
scp and sftp sessions
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