All posts by ryan@dss-i.com

Upgrading Splunk Add Ons

This topic comes up every now and then working with customers and partners deploying and upgrading add ons for Splunk does not have to be hard there are a few rules to live by. I’m going to use Splunk_TA_Windows 5.0.1 in this walk through. This upgrade has some specific guidance in addition to the usual steps. As can often be the case with software correcting issues can require additional work for compatibility.

Upgrading things to do first

Be proactive read the docs

In the release notes Splunk advises that sourcetypes will change. Two new source types “EventLog” and “XMLEventLog” will replace all previous event log specific source types. The source will indicate the specific log used which is consistent with most other source/sourcetypes use in Splunk. Sourcetype is a structure and source is an instance of the structure for a specific host. As instructed review custom searches and eventypes and update to utilize source rather than sourcetype.

Review the additional changes in the docs determine if any apply to your environment.

Review local changes

Identify any search time local changes made to the sourcetypes managed by the add-on in question. In most cases these will located in the $SPLUNK_HOME/etc/apps/Splunk_TA_windows/local folder however in some cases you may find them in $SPLUNK_HOME/etc/apps/Splunk_TA_windows/search. Review and compare to the latest version of the add on, confirm they can or should remain at upgrade time.

Identify any index time local changes made to the sourcetypes managed by the add on in most cases these can be found in the cluster master $SPLUNK_HOME/etc/master-apps/Splunk_TA_windows/local however in some organizations customizations are made in another custom app. If you have inherited this environment be sure to consider how others may have made customizations before you.

While this post is specific to Splunk_TA_windows most steps do apply to any add-on deployment.

Installing the upgrade

The first step when possible is to test in a non production environment, in many cases the only complete environment is Production care should be taken and changes should be made in off hours.

Search Heads (non clustered)

Repeat on each search head

  1. Backup the current app from by copying Splunk_TA_windows to a safe location
  2. Install the app using the CLI or app browser “install from file”
  3. Restart the search head
  4. Verify any custom dashboards or alert searches continue as expected

Search Heads (clustered)

Repeat on each search head cluster

  1. Backup the current app from by copying Splunk_TA_windows to a safe location on a search head cluster member
  2. (ES Only) For a ES Search head cluster only remove the Splunk_TA_Windows from shcluster/apps on the deployer and apply the new bundle to the cluster using the preserve-lookups option as documented in the Enterprise Security documentation
  3. Verify Splunk_TA_Windows is removed from the peers
  4. Expand Splunk_TA_Windows into shcluster/apps
  5. Apply the new bundle using preserve-lookups if ES

Indexers

  1. Expand Splunk_TA_Windows in a temporary location, remove the following files
    1. <app>/bin
    2. <app>/default/eventgen.conf
    3. <app>/default/inputs.conf
    4. <app>/default/wmi.conf
    5. <app>/default/indexes.conf
  2. Splunk has removed all index definitions from this add-on in accordance with best practices and app verification requirements. Review the indexes in use and ensure the indexes have been re-defined according to your environments requirements.
  3. Verify the organizations indexes.conf contains all required indexes
  4. Deploy the updated add-on via master-apps for clustered indexers (automatic rolling restart) or to apps on all non clustered indexers and restart.

Intermediate Heavy Forwarders

  1. Expand Splunk_TA_Windows in a temporary location, remove the following files
    1. <app>/bin
    2. <app>/default/eventgen.conf
    3. <app>/default/inputs.conf
    4. <app>/default/wmi.conf
    5. <app>/default/indexes.conf
  2. Deploy to apps on all instances and restart

Collecting Forwarders using the deployment server

  1. Review all deployment-apps/*/local/inputs.conf applied to windows systems as follows.
    1. Ensure index is specified on each utilized input
    2. Ensure disabled=false is specified on each utilized input
    3. If no inputs.conf is found “demo defaults” has been utilized up to this point. Copy Splunk_TA_windows/default/inputs to Splunk_TA_windows/local and review stanzas to determine which should remain enabled
    4. Backup deployment-apps/Splunk_TA_windows to a safe location and remove
    5. Expand Splunk_TA_windows to deployment-apps.
    6. Reload the deployment server
  2. Verify no “missing index” messages appear in the cluster if so identify the incorrectly configured input and redeploy
  3. Verify no new use of last change or main index if so identify the incorrectly configured input and redeploy.
  4. Repeat verification of searches and alerts as above.

 

Identifying obvious sourcetype problems in Splunk

This is a short one, on boarding data into any system is great making it identifiable and usable by the end users thats even more important. In Splunk source, sourcetype, and index are the most basic bits of metadata available to users and often they work with only these three because its just so easy. When our upstream sources don’t set these values correctly it can stress the environment because we are doing unnecessary  work like “line merging” and our users can’d find data. Using Splunk logs we can see where this may be happening and start to fix it. This search will identify suspect sourcetypes. Review the onboarding of each identified to make it better.

index=_internal source="*metrics.log" sourcetype=splunkd group=per_sourcetype_thruput
| eval sourcetype_error=if(match(series,"^[\$\%\#]"),"__Invalid_char",sourcetype_error)
| eval sourcetype_error=if(isnull(series) OR st="" ,"__Invalid_null",sourcetype_error)
| eval sourcetype_error=if(match(series,"^\/"),"__Invalid_usedpath",sourcetype_error)
| eval sourcetype_error=if(match(series,"^\d+\.\d+\.\d+\.\d+"),"__Invalid_used_IP",sourcetype_error)
| eval sourcetype_error=if(match(series,"\s"),"__Invalid_space",sourcetype_error)
| eval sourcetype_error=if(like(series,"%small"),"__Invalid_too_small",sourcetype_error)
| eval sourcetype_error=if(match(series,"\d+"),"__Invalid_numeric",sourcetype_error)
| eval sourcetype_error=if(match(series,"\-\d"),"__Invalid_learnednum",sourcetype_error)
| eval sourcetype_error=if(match(series,"\-error"),"__Invalid_learnederror",sourcetype_error)
| eval sourcetype_error=if(match(series,"\*"),"__Invalid_asterisk",sourcetype_error)
| eval sourcetype_error=if(match(series,"\.\w{1,4}$"),"__Invalid_filename",sourcetype_error)
| eval sourcetype_error=if(match(series,"[\.\-]log$"),"__Invalid_autousinglogfilename",sourcetype_error)
| eval sourcetype_error=if(match(series,"^![\w\_\-\:]+$"),"__Invalid_nonsourcetype_errorndardform",sourcetype_error)
| search sourcetype_error=*
| stats sum(kb) as kb avg(kbps) as kbps_avg avg(eps) as eps_avg sum(ev) as ev values(sourcetype_error) by series
| eval mb=round(kb/1024,2)
| fields - kb
| sort limit=0 -mb

Code as snippet https://bitbucket.org/snippets/rfaircloth-splunk/Benb45

Protecting ATMs from the two arm bandits

Jackpot ATM style

According to Krebs two arm bandits are about to hit the jack pot on American ATMS, also known as ABM machines out side of the US. Like most security issues its an arms race, did you know ATM machines have holes in the bottom so crooks can’t fill them with water and blow up the door without damaging the cash? Well they started out solid someone noticed that flaw and exploited it we learned and got better.

Just before Y2K and in the years after banking systems moved from proprietary operating systems and applications, custom interfaces and hardware to Windows based “open” systems with vendor agnostic drivers and tools allowing for innovation and cost reduction. This change swapped out custom controller cards for “USB” devices, Bisync serial for TCP over ethernet, wifi, 4G, PPP. The builders of these new networks didn’t have much experience in network security and left open many many doors. The physical design protects you card number and pin but left the cash open. To keep service costs low the PC components are in a section of the machine called the “hood” and can be serviced without opening the safe and exposing the cash. This is a great design from the perspective of PC service. It also ensure the safety of the repair tech as they can not access the bulk cash there is no reason to rob them at gun point. Great but we still have a problem. The USB and network interfaced are now protected by a 4-6 pin basic lock, all the keys in a region are the same because keeping track of keys are hard. Protecting from a breach from a physical attacker is something the design precludes so we could die on this hill but we can’t take it, what can we do?

You have Splunk! you also have a remote CCTV system (nvr) or physical alarm what if we pull this data together build a threat model and respond faster.

  • Monitor “motion” events from the NVR system
    • Identify cameras indicating motion front and back of the ATM
      • ATM ID
      • Front/Back
      • Duration of Motion
    • Motion in back of more than n seconds and motion in front of more than x seconds without y duration alert
  • Monitor the network switch/wifi
    • map switch/ap events where the port/connection disconnects to the ATM ID
  • Monitor the _internal source from the installed UF silence of more than n seconds
  • Use the UF to monitor for XFS events via ETW or windows events
    • Hood open
    • Dispenser disconnect
    • New Device
  • Install Splunk Stream to monitor TLS/HTTPS aggregate by certificate ID every 5 min. Map src to atm ID alert if the presented cert changes for the Authorization Server
  • Using XYGate monitor your Switch (base24/efunds) or SyncSort (Z/OS based custom) monitor for dispenser totals mismatch for the ATM ID

Summarize each of the alerts above using | collect normalizing based on ATM ID. Use Splunk built in alert function to notify ATM OPS and physical security on any occurrence of 3 or more in 15 min, tune for false positives.

Lets Encrypt and get an A for A Great Splunk TLS config

Setting up SSL/TLS on Splunk doesn’t have to be super hard or costly. While running Splunk in cloud providers has many benefits there are some hassles like provisioning certificates we can better manage using let’s encrypt. This method of installing browser trusted certificates can help to keep your administrative costs down in large Splunk deployments such as MssP services.

Expanding on prior work https://www.splunk.com/blog/2016/08/12/secure-splunk-web-in-five-minutes-using-lets-encrypt.html

NGINX

First we are going to install NGINX we will use this as a front end reverse proxy. Why, we can renew our certs with minimal own time in the future, OCSP stapling (improved page load times) and other things (future posts)

#centos

yum install nginx

#ubuntu

apt-get install nginx

Second setup a new vhost for the splunk reverse proxy. Any request to http will be redirected to https except for requests related to certificate management.

map $uri $redirect_https {

    /.well-known/                      0;

    default                            1;

}

server {

    listen       80;

    server_name  hf-scan.splunk.example.com;

    root /usr/share/nginx/html;

    if ($redirect_https = 1) {

       return 301 https://$server_name$request_uri;

    }

#    return       301 $scheme://hf-scan.splunk.example.com$request_uri;

}

server {

    

    listen 443 ssl http2;

    server_name hf-scan.splunk.example.com;

    root /usr/share/nginx/html;

    index index.html index.htm;

   location / {

        proxy_pass_request_headers on;

        proxy_set_header x-real-IP $remote_addr;

        proxy_set_header x-forwarded-for $proxy_add_x_forwarded_for;

        proxy_set_header host $host;

        proxy_pass https://127.0.0.1:8000;

        add_header Strict-Transport-Security “max-age=31536000; includeSubDomains” always;

      }

    

    

    ssl_certificate     /etc/letsencrypt/live/hf-scan.splunk.example.com/fullchain.pem;

    ssl_certificate_key /etc/letsencrypt/live/hf-scan.splunk.example.com/privkey.pem;

    ssl_protocols       TLSv1.2;

    ssl_ciphers         HIGH:!aNULL:!MD5;

    ssl_dhparam /etc/nginx/ssl/dhparam.pem;

    ssl_session_cache shared:SSL:50m;

    ssl_session_timeout 1d;

    ssl_session_tickets off;

    ssl_prefer_server_ciphers on;

    ssl_stapling on;

    ssl_stapling_verify on;

    resolver 8.8.8.8 8.8.4.4 valid=300s;

    resolver_timeout 5s;

    add_header Strict-Transport-Security “max-age=31536000; includeSubDomains” always;

}

Setup a deploy hook script this will prepare the cert files as splunk needs them and will also be used on renewal. Save this script as /etc/letsencrypt/renewal-hooks/deploy/splunk.sh

#!/bin/bash
#deploy to /etc/letsencrypt/renewal-hooks/deploy/splunk.sh
#when requesting a cert add "--deploy-hook /etc/letsencrypt/renewal-hooks/deploy/splunk.sh" to the command
dir=/opt/splunk/etc/auth/ssl
if [[ ! -e $dir ]]; then
    mkdir -p $dir
elif [[ ! -d $dir ]]; then
    echo "$dir already exists but is not a directory" 1>&2
fi
openssl rsa -aes256 -in $RENEWED_LINEAGE/privkey.pem -out $dir/protected.pem -passout pass:password
if [[ ! -f $dir/protected.pem ]]; then
    exit 1
fi
cat $dir/protected.pem $RENEWED_LINEAGE/fullchain.pem > $dir/server.pem
cp $RENEWED_LINEAGE/fullchain.pem $dir/
cp $RENEWED_LINEAGE/privkey.pem $dir/
chown splunk:splunk $dir/*
systemctl restart splunk

Request the certificate note correct the webroot folder for your platform and the certificate with the fqdn of your server

certbot certonly –webroot -w /var/www/html –hsts -d hf-scan.splunk.example.com –noninteractive –agree-tos –email your@example.com –deploy-hook /etc/letsencrypt/renewal-hooks/deploy/splunk.sh

Setup Splunk

Update /opt/splunk/etc/system/local/web.conf

[settings]

enableSplunkWebSSL = true

#sendStrictTransportSecurityHeader = true

sslVersions = tls1.2

cipherSuite = TLSv1.2:!NULL-SHA256:!AES128-SHA256:!ADH-AES128-SHA256:!ADH-AES256-SHA256:!ADH-AES128-GCM-SHA256:!ADH-AES256-GCM-SHA384

privKeyPath =  /opt/splunk/etc/auth/ssl/privkey.pem

caCertPath = /opt/splunk/etc/auth/ssl/fullchain.pem

Update /opt/splunk/etc/system/local/server.conf

[general]

serverName = hf-scan.splunk.example.com

[sslConfig]

sslVersions = tls1.2

sslVersionsForClient = tls1.2

serverCert = $SPLUNK_HOME/etc/auth/ssl/server.pem

sslRootCAPath = $SPLUNK_HOME/etc/auth/ssl/fullchain.pem

dhFile = /opt/splunk/etc/auth/ssl/dhparam.pem

sendStrictTransportSecurityHeader = true

allowSslCompression = false

cipherSuite = TLSv1.2:!NULL-SHA256:!AES128-SHA256:!ADH-AES128-SHA256:!ADH-AES256-SHA256:!ADH-AES128-GCM-SHA256:!ADH-AES256-GCM-SHA384

useClientSSLCompression = false

useSplunkdClientSSLCompression = false

Test

  • Option 1 SSL labs, limited to port 443 (don’t forget about 8089)
  • Option 2 testssl.sh CLI based doesn’t share data no letter grade (management likes letters)
  • Option 3 High Tech Bridge https://www.htbridge.com/ssl allows testing multiple ports similar coverage to ssllabs less well known

Renew certs

Setup a cron job to run the following command at least once per week in your scheduled change window. If a certificate renewal is required splunk will be restarted

certbot renew –webroot  -w /usr/share/nginx/html

Can we even patch this Spectre/Meltdown oh and AV also

Isn’t it great when things are in meltdown and you can’t patch yet because your waiting on another patch?

Microsoft has stated you can’t patch until AV goes first

http://www.zdnet.com/article/windows-meltdown-spectre-fix-how-to-check-if-your-av-is-blocking-microsoft-patch/

https://support.microsoft.com/en-us/help/4072699/january-3-2018-windows-security-updates-and-antivirus-software

Bottom line if your AV vendor hasn’t update to set this registry to give the update permissions to install or you don’t use AV and instead use an application whitelist approach for security the patch won’t apply. You can use splunk to track down hosts that will refuse to apply the patch by adding this monitor to splunk and well Splunking the results

Key="HKEY_LOCAL_MACHINE" Subkey="SOFTWARE\Microsoft\Windows\CurrentVersion\QualityCompat" Value="cadca5fe-87d3-4b96-b7fb-a231484277cc" Type="REG_DWORD”
Data="0x00000000

Add the following to the inputs.conf applied to all windows system and ensure the server class is set to restart the UF and happy Splunking

 

[WinRegMon://HKLMSoftwareMSWindowsQualityCompat]
index = epintel
baseline = 1
disabled = 0
hive = \\REGISTRY\\MACHINE\\Software\\Microsoft\\Windows\\CurrentVersion\\QualityCompat\\.*
proc = .*
type = delete|create|set|rename

Tuning Splunk when max concurrent searches are reached

Your searches are queued but you have cores, memory and IO to spare? Tuning your limits can allow Splunk to utilize “more” of your hardware when scaled up instances are in use.

Warnings

This approach is NOT  useful when searches run LONG. If regular searches such as datamodel acceleration, summary and reporting searches are not completing inside of the expected/required time constraints this information could make the symptoms worse.

This approach is useful when searches consistently execute faster than the required times for datamodel acceleration, summary and reporting and additional searches are queued while the utilization of cpu, memory, storage IOPS, storage bandwidth are well below the validated capacity of the infrastructure.

 

Details

First in all certain versions of Splunk apply the following setting to disable a feature that can slow search initialization.

$SPLUNK_HOME/etc/local/limits.conf

$SPLUNK_HOME/etc/master-apps/_cluster/local/limits.conf

[search]
#Splunk version >=6.5.0 <6.5.6
#Splunk version >=6.6.0 <6.6.3
#Not required >7.0.0
#SPL-136845 Review future release notes to determine if this can be reverted to auto
max_searches_per_process = 1

On the search head only where DMA is utilized (ES) update the following

$SPLUNK_HOME/etc/local/limits.conf

#this is useful when you have ad-hoc to spare but are skipping searches (ES I'm looking at you) or other 
# home grown or similar things
[scheduler]
max_searches_perc = 75
auto_summary_perc = 100

Evaluate the load percentage on the search heads and indexers including memory, cpu utilized and memory utilized.  We can increase the value of base_max_searches in increments of 10 to allow more concurrent searches per SH until one of the following occurs

  • CPU or memory utilization is 60% on IDX or SH
  • IOPS or storage throughput hits  ceiling and no longer increases  decrease the system is fully utilized to prevent failure due to unexpected load decrement the base_max_searches value by 10 and confirm IOPS is no longer constant.
  • Skipping /queuing no longer occurs (increase by 1-3 additional units from this point to provide some “head room”
#limits.conf set SH only
[search]
#base value is 6 increase by 10 until utilization on IDX or SH is at 60% CPU/memory starting with 20
#base_max_searches = TBD

Outage due to DDOS

The sites been down for a few days, BlueHost has been suffering from a DDOS on at least one of the sites they host. My site shared infrastructure. for $3.95 a month I don’t expect too much but having some ability to move sites to new hosts would be nice.  Anyways, I’m up on Azure now until I decide if I want to be my own webmaster or revert to paying someone else to pretend to worry about things like that.  On the plus side of things, the outage forced me to update the site infrastructure. Now using certificates from Let’s Encrypt.  If you have CLI access to your apache hosted site, super easy and free to enable good encryption.

sudo certbot –apache -d www.rfaircloth.com -d rfaircloth.com -d rfaircloth.westus.cloudapp.azure.com –must-staple –redirect   –hsts   –uir –rsa 4096

What’s in a URL now you can Splunk that

Hunting we find URLs in logs both email and proxy that are interesting all the time. What will that URL return, if it redirects where is it going and what kind of content questions you might be asking. If you are not asking them now is the time to start. I’ve released a new add on to Splunk Base, a little adaptive response action that can be used with just Splunk Enterprise OR Splunk Enterprise Security to collect and index information about those URLs.

https://splunkbase.splunk.com/app/3630/

How to enable the Alexa Domain list in ES 4.7

This post is short and sweet, in ES 4.7 the Alexa download is not enabled by default enabling and using this list which can be very valuable in domain/fqdn based analysis is a simple two step process

  1. Navigate to Enterprise Security –> Configure –> Threat Intelligence Downloads
    1. Find Alexa
    2. Click enable
  2. Navigate to Splunk Settings –> Search Reports and Alerts
    1. Select “All” from the app drop down
    2. Search for “Threat – Alexa Top Sites – Lookup Gen
    3. Click Edit under actions and then enable
    4. Optional Click Edit under actions again and cron schedule, Set the task to daily execution 03:00 with an auto window. This reduces the chances the list will not be updated if skipped due to search head maintenance.
    5. Optional the OOB gen search creates a large dispatch directory entry which is not desirable on search head clusters or where disk space is premium such as public clouds. Update the search as follow (appending the stats count) to prevent creation of a result set on the search head | inputthreatlist alexa_top_one_million_sites fieldnames=”rank,domain” | outputlookup alexa_lookup_by_stra | stats count
    6. Click “Run” to build the list so you can have it right now