Web header corruption with cgi calls using xymonmenu.cfg and xymonpage - a workaround

Den 10.01.2014 19:56, Deiss, Mark skrev:

Maybe this has been fixed in Xymon releases 4.3.11+. This is dealing
with custom cgi's being placed into
cgi-bin/cgi-secure that are calling the xymonpage procedure. Problem
is being experienced in 4.3.11.

When installing/modifying a custom module, running into corrupt web
content with the
upper menu installed through the xymonmenu.cfg/XYMONBODYHEADER
mechanism via xymonpage. One variables is not
being defined (XYMONSERVERSECURECGIURL) and de-referencing of another
(XYMONSERVERWWWWURL) during
execution. The latter condition is kinky; I tried tracing through
xymonpage.c/headfoot.c but ended
up getting lost. Until the XYMONSERVESECURECGIURL is ~~encountered in
the xymonmenu.cfg, the XYMONSERVERWWWURL is
being resolved.

I think this is caused by missing out the fact that xymonserver.cfg is NOT intended to be used directly in shell scripts. As it says at the very top of xymonserver.cfg:

    # NB : Even though it might look like a shell-script, it is NOT.


So when you do this:

#!/bin/sh
export XYMONHOME=<your path>/xymon/server
. ${XYMONHOME}/etc/xymonserver.cfg

then you are doing it wrong. E.g. it won't handle any "include" or "directory" settings.

function try1 {
# 1) bad iteration, source in everything at parent level - this results in erratic variable
#       expansion in results, cannot find value for XYMONSERVERSECURECGIURL and XYMONSERVERWWWURL
#       initially defined but lost on first incidence of XYMONSERVERSECURECGIURL (undefined)
. ${XYMONHOME}/etc/xymonserver.cfg
echo hello | \
        ${XYMONHOME}/bin/xymonpage

You cannot source xymonserver.cfg. The correct way of doing what you want is:

echo hello | \
         ${XYMONHOME}/bin/xymoncmd --env=${XYMONHOME}/etc/xymonserver.cfg xymonpage

In other words, you must let xymoncmd process the xymonserver.cfg file, and then have xymoncmd directly invoke the Xymon command that you want to use. You can omit the "--env" option if you compiled Xymon with the correct XYMONHOME setting.

function try2 {
# 2) bad iteration, source in using xymoncmd - same erratic results
exec ${XYMONHOME}/bin/xymoncmd --env=${XYMONHOME}/etc/xymonserver.cfg echo hello | \
        ${XYMONHOME}/bin/xymonpage
}

Here xymoncmd sets up the environment for the "echo hello" command, but your SHELL does NOT pass this to the xymonpage command.

function try3 {
# 3) works, source in everything at parent level - to set up environment for initial
#       execution (the "echo hello" portion) then also re-introduce environment in
#       xymonpage using "--env" setting, xymonpage is not reliably picking up runtime
#       inherittance otherwise
exec ${XYMONHOME}/bin/xymoncmd --env=${XYMONHOME}/etc/xymonserver.cfg echo hello | \
        ${XYMONHOME}/bin/xymonpage --env=${XYMONHOME}/etc/xymonserver.cfg
}

Yep, this works because xymonpage now reads xymonserver.cfg by itself. So it doesn't rely on things coming in via the environment variables. You don't need the xymoncmd at all, the "echo hello" doesn't use it (same as in 2)).

function try4 {
# 4) works
. ${XYMONHOME}/etc/xymonserver.cfg
echo hello | \
        ${XYMONHOME}/bin/xymonpage --env=${XYMONHOME}/etc/xymonserver.cfg
}

Same as 3), but the source'ing of xymonserver.cfg is both wrong and useless.


Hope this helps.


Regards,
Henrik