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Passive SSL

This app has been archived. Learn more about app archiving.
This app is NOT supported by Splunk. Please read about what that means for you here.
CIRCL Passive SSL is a database storing historical X.509 certificates seen per IP address. The Passive SSL historical data is indexed per IP address, which makes it searchable for incident handlers, security analysts or researchers.

This is a scripted lookup to query this database directly from Splunk.


To use the CIRCL Passive SSL service, you will be required to have a valid account which should be asked to the CIRCL directly through the following page https://www.circl.lu/services/passive-ssl/.

Detailled information about the service can also be found on the above page.

App Setup

After downloading this app, install it like any other app, either through the WebUI, either through the command line, it's up to you.

Then, you will need to edit the file pssl_lookup.py located in $SPLUNK_HOME/etc/apps/pssl/bin/

You only need to edit this file to configure your service account. For example, if your account username is "John" and your password is "1234567", proceed as follow:

Change this:

username = "<YOUR USERNAME>"

password = "<YOUR PASSWORD>"

To this:

username = "John"

password = "1234567"

Save and quit. You are done with the setup!


This app provides two scripted lookups :

  • `pssl_resolve(hostname)`

This lookup is a simple and naive hostname resolver to get the IPv4 address of the provided hostname. In case of failure, None is returned.

It's not directly linked to the Passive SSL service offered by CIRCL, but quite mandatory practically speaking because the Passive SSL service only works with IPv4 addresses as input.

The lookup notation is as follow:

... | lookup pssl_resolve_lookup domain as <your_field>

  • `pssl(cidr)`

This lookup is what will query the CIRCL Passive SSL service. As input you can have either an IPv4 or either a CIDR notation (ex: Note that at this moment the API do not handle mask lower than /23.

The lookup notation is as follow:

... | lookup pssl_lookup cidr as <your_field>


In this example, we will assume Proxy logs. Those logs will contains a field named cs_method describing the HTTP method used and cs_uri which contains the requested page.

The query will be the following:

  1. Filter the sourcetype to only consider log lines using the CONNECT method, relevant of SSL connections.
  2. Drop every fields except the field cs_uri which contains the url destination
  3. Dedup the destinations url using the stats command
  4. Parse the destinations url using UTBox (ut_parse_simple, see below)
  5. Drop every fields except the field ut_netloc created by UTBox
  6. Remove the potential port specification using rtrim()
  7. Resolve the domain name to an IPv4 address
  8. Filter out domain that are not resolved
  9. Query the CIRCL Passive SSL database using the resolved IPv4
  10. Finally, display the results in a table.

The query:

sourcetype="proxy" cs_method="CONNECT" cs_uri=* NOT cs_uri=-

| fields cs_uri

| stats count by cs_uri

| `ut_parse_simple(cs_uri)`

| fields ut_netloc

| eval netloc=rtrim(ut_netloc, ": 0123456789")

| `pssl_resolve(netloc)`

| search ip != None

| `pssl(ip)`

| table netloc ip circl_pssl


  • Steps 7 and 9 can significally slow down your whole query as each time an event enter those lookups, a query to Internet is made.

  • UTBox is available here: https://splunkbase.splunk.com/app/2734/

Release Notes

Version 1.0
June 26, 2015

Created by Splunk Security Practice


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