Category Archives: Linux

some linux topics, hacks, fixes, bugs and so on — everything what seems to be important to me.

Get CVE information from NIST NVD and RHEL

Just two littel scripts that come handy if you want to download all the CVE info in JSON format for offline use.

#!/bin/bash
urls=$(curl https://nvd.nist.gov/vuln/data-feeds#JSON_FEED | grep 'https://' | grep -i json.gz | sed 's/.*href=//g' | cut -d\'  -f2)

mkdir -p ./nistNvdJson
cd nistNvdJson
for l in $urls;
do
wget $l
done
gunzip *
Donwload NIST NVD CVEs in JSON

 

#!/bin/bash


loopVar=1
dataDir="rhelCveData"
mkdir $dataDir -p
echo "getting data:"
T="$(date +%s)"
while [[ $loopVar -ne 0 ]];
do
        echo -n "-$loopVar- "
        data=$(curl -s https://access.redhat.com/labs/securitydataapi/cve.json?page=$loopVar)
        if [[ "$data" == "[]" ]]; then
                loopVar=0
        else
                toFile=$toFile${data:1:-1}", "
                let loopVar=loopVar+1
        fi
done
T="$(($(date +%s)-T))"
echo "[${toFile::-2}]" >> "$dataDir/rhelCve.json"
sed -i 's/^\[\]$//g' "$dataDir/rhelCve.json"
printf "Got data in: %02dd:%02dh:%02dm:%02ds\n" "$((T/86400))" "$((T/3600%24))" "$((T/60%60))" "$((T%60))"
Get CVE infos for RHEL

 

Additional information:
If you query the NIST NVD Data and search for RHEL CPEs you won’t get a lot of hits as only a smal percentage of the CVEs that affect Red Hat software has the correct CPE attached. However – NIST NVD is nice to have because in the Red Hat CVEs only the total CVSS score is listed but no detailed vulnerability metrics are included.

vCenter alarm Polling (v2) – Cross platform version (Windows & Appliance)

As it has been some time since my last post about a solution on how to get vCenter alarms to Zabbix, and VMware also evolved I followed a new approach on that topic as my initial post only supports Windows vCenters. Furthermore the solution is not as stable as I wished that it would be, so my new approach is to query all alarms from a vCenter via it’s SDK.
Initially all the alarms are discovered and created in Zabbix and in a second step the values for the discovered alarms are polled.
Currently the script used the data center object of the vCenter to discover alarms, so it can’t be used on a standalone ESXi-Server. However – if the code is changed to use whatever object is needed to get the alarms directly from the ESXi-server it should also be possible to get alarms directly from a server without the need of a vCenter (but I didn’t implement that till now as there wasn’t the need/time).

vCenter alarms – SDK (tested with ESXi 6.0+ and Zabbix 3.0 on RHEL 7)

To install the vCenter alarms the attached zip needs to be downloaded and the VMware Perl SDK must be installed on the Zabbix Server.
The template needs to be imported into Zabbix and the vCenter username and password need to be set in the username/password macros of the template.

The other two files (vcenterAlarms.pl & vcenterAlarms.wrapper) need to be extracted to the externalscripts folder of the Zabbix Server. The wrapper script is just a shell script that is executed by a Zabbix item to call the per script and send the that to Zabbix via Zabbix Sender.  As the VMware API is quite slow the wrapper also starts itself again with NOHUP because otherwise the timeout defined in the Zabbix Server configuration would cause an exit of the script. For my setup it always took longer than 30 Seconds till tall data where gathered and therefor the Zabbix Server would kill the script in the middle of the execution and no data would be sent to Zabbix. That’s why I added this workaround. Furthermore it also checks if there are less than eleven vcenterAlarms.wrapper processes running, and only starts if there are less, to ensure that Zabbix does not spawn hundreds of NOHUP-processes.

 

 

 

 

Apache – force autocomplete=off for password fields

If 3rd party software is installed it is quite likely that the autocomplete attribute for password fields is not set to off. Editing such settings directly in the sourceode is possible most of the time, but it’s not the nicest way and you also run into the problem that everything could be gone again after an update of the software.

A nice workaround is to use the substitute module to accomplish that.

<Location "/">
    AddOutputFilterByType SUBSTITUTE text/html
    Substitute "s|<input type=password|<input type=password autocomplete=off|i"
</Location>
disable autocomplete for password fields

Create you onw 4to6-tunnel / Access IPv6 service from IPv4 address

With my recent ISP-change for my internet at home there where quite a lot of changes. One of that changes was, that UPC – my current provider – uses DualStack Lite.
For me it’s the first ISP that really provides IPv6. So that’s pretty cool and I finally had the chance (was forced) into digging deeper into IPv6.

In general everything is working quite well but, as it’s dual stack lite my router doesn’t provide an option to do some portforwarding to one of my hosts inside my local network. At least not for IPv4 connections. So I have no chance to access one of my devices via my public IPv4 address what becomes a problem when I want to connect to my home network via VPN from an IPv4 only network.

I couldn’t find any suitable 4to6 tunnel broker that lets me access my IPv6-devices through an IPv4 address, but luckily I have a VPS that runs on real dualstack and therefor has an IPv4 and IPv6 address.

So to access my IPV6 VPN server in my private network from an IPv4 only network I created an SSH-tunnel from my VPN-server (that runs on a Raspberry PI) to my VPS and forwarded the OpenVPN port.

To do that the VPS’ sshd-configuration needs to be adapted to expose forwarded ports to it’s public IP-address(es). For that the following setting needs to be added to/ changed in the sshd_config:

GatewayPorts yes

 

After that I created the following script on my VPN-Raspberry:

#!/bin/bash

varConnectionString="-nNT -R 1194:localhost:1194 <username>@<servername> -p <port>"

if [[ $(ps aux | grep -v "grep" | grep "$(echo $varConnectionString | sed 's/^-/\\-/g')") ]]; then

echo "Found active connection"

else

echo "No active connection found"
ssh $(echo $varConnectionString) &
fi
create SSH-tunnel

That script is added to be exectuted every half hour as a cronjob. So if the connection (for whatever reason) gets diconnected it will automatically reconnect to the VPS and forward the port again.

 

ORACLE – Convert datetime to epoch / unixtimestamp

It seems Oracle DB doesn’t provide a function to create a unix timestamp from an internal datetime. I have to admit – I’m kinda disappointed about that, but OK – its Oracle …

So, how can we get a timestamp from Oracle. I have googled quite a time, but non of the solutions google offered me worked, so i it’s time to think about it by myself and ended up with the following solution:

select (extract(day from (EVENT_TIME  - to_date('01-JAN-1970','DD-MON-YYYY')))*86400+extract(hour from EVENT_TIME)*3600+extract(minute from EVENT_TIME)*60+extract(second from EVENT_TIME)) as EPOCH from SOMETABLE order by event_time DESC;

At first I subtract the start of the epoch from my current timestamp. this will provide me the days since 1970-01-01. Afterwards I extract hours, minutes and seconds from the timestamp and with all those data it’s possible to calc the timestamp of the specific datetime.

Zabbix – Clear hosts from untemplated items

Sometimes you run into the problem, that you have a host which had a template attached but somebody wanted to replace the template or something like that and unfortunately hit just “Unlink” instead of “Unlink and Clear” and all the items are still in the host.

If you have only one host it’s normaly no problem to delete all items per hand, but if you have multiple of those hosts it’s quite some work do remove the old items.

Solution nr. one would be tu use the filters to select all items in a specified host group and delte those items, but the applications, discovery rules and so on will still remain in the hosts and have to be deleted in a 2nd/3rd step.

See the Screenshot below:Zabbix Host configuration - item filters

 

My preferred solution for this problem is a simple regex based find/replace with Notepad++.
Herefor an export of the affected hosts is needed. The xml-file could be opend with NPP and the following regexes are needed for find/replace (CTRL+H) to remove the unwanted items.

Find what: (<discovery_rules>[\s\S]*?<\/discovery_rules>)|(<triggers>[\s\S]*?<\/triggers>)|(<inventory>[\s\S]*?<\/inventory>)|(<items>[\s\S]*?<\/items>)

Replace with: (?1<discovery_rules />)(?2<triggers />)(?3<inventory />)(?4<items />)

In the above example multiple regexes with multiple replace-patterns are used to replace the items, discovery rules, triggers an inventory and reset it.

Remove Oracle ApEx from the database

Because Nessus seems to dislike Oracle ApEx we needed to remove it from the database.  Oracles manual regrading the removal is pretty straight forward (https://docs.oracle.com/database/121/HTMIG/trouble.htm#HTMIG270), but I wanted to do it in a single none intreactive line which makes it easier to do de removal automated.

so – here it is:

echo quit | sqlplus -S "sys/sys as sysdba" @$ORACLE_HOME/apex/apxremov.sql

Zabbix 1.8 to 2.2 Upgrade

Lately I was asked to help to upgrade Zabbix from 1.8 to 2.2 in a project. It wasn’t a problem to upgrade the templates – that was easily done with a xml-export/import but the hosts where kind of a challenge because the exported xml-files for the hosts itself pretty differs between 1.8 and 2.2.

Because i already had the PhpZabbixApi (https://github.com/confirm/PhpZabbixApi/blob/master/README.md) installed on the tared system i decided to write a little script which pareses the 1.8-host export and creates the hosts in 2.2. The script inc. the lib is attached at the end of the post.

I tested the script with Zabbix 1.8.6->2.2.10 and everything worked fine. Currently the script is capable of creating the hosts (with Zabbix-agent & SNMP-interface), creating the host groups and adding the hosts to the correct host group and also linking the correct templates to the host. However, the templates need to be already available on the target system to be linked correctly.

After extracting the script on the target Zabbix server the xml-import from the old system needs to be uploaded into the same directory as the script (scp) and the login data for Zabbix need to be adapted in the script. Afterwards the import can be started from a bash via:

Zabbix1.8_2.2_upgrade

 

Get vCenter alarms into Zabbix via poll-method

Some time ago i wrote a post on how to forward vCenter alarms to Zabbix ( https://blog.fawcs.info/2015/05/getting-vcenter-alarms-to-zabbix/) and I have to admit, that this solutions is kind of a pain in the ass. I’m getting the alarm info from environmental varaibles which are automatically set by the vCenter when an alarm changes its status, but it seems that there is a “littel” problem with “overlapping” alarms. For example if there are occuring multiple alarms within a short period only the first alarm will be forwarded to zabbix, but non of the follwoing alarms. Besides that this is not an ideal solution I personally do not like my former approach because it’s an event driven approach. So if one event goes missing we have an inconsistent system :/

It’s quite some time since I wanted to redesign the solution and now I’m finally having some time ( and the pressure) to do so. 🙂
The new approach is based on using userparameters to execute a powershellscript on the vCenter to discover all active alarms and create items in Zabbix. At the moment I’m creating three item prototyes. One for the Timestamp when the alarm became active, another item for the acknowledged-state of the alarm and the last one for the severity of the alarm.

There are two userparemeters which run two powershell scripts. The first one (vcenter.alarm.polling.discovery.ps1) does the discovery and the second one (vcenter.alarm.polling.itemdata.ps1) is to get the data for the discoverd items.
There are also three triggers (one for each severity gray, yellow, red) which will be active als long as the alarm is not acknowledged.

You can download the scripts, userparameters and the template down below:
vCenterAlarmPolling

 

Additional findings:
Ther can occure problems if there are different addresses used to connect to the vcenter (eg. 127.0.0.1, loclahost, vcenterhostname, …)
It seems that the vCenter creates a sperate datacenter instance for every connection, so if you use the three examples from abovve you will end up creating three instances and mess up the script.

 

If special characters want to be passed to the powershellscript (e.g. special chars in passwords ord login with administrator@vsphere.local) the “UnsafeUserParameters=1” – parameter from the zabbix-agent.conf needs to be set to 1. (default value is 0)

Putty – Terminal “halts/freezes” after CTRL+S

Did you ever work with vi/nano (whatever)  and wanted to save a file?
If you are not that hardcore a linux person who does everything on a terminal and also works with Windows, you know that it is always a good idea to press CTRL+S once in a while to save your progress.

I press this shortcut automatically and it even happens to me while working on a putty session, which results in a “freezed” terminal session.
The reason for this behavior is that ctrl+s sends “XOFF” and putty stopps displaying any output, but still accepts keystrokes.

But its also easy to disable XOFF again – just press CTRL+Q and putty will continue to show your output on the screen. 🙂