vpnnotify is a tool that will send a user a slack message when they connect to a VPN session. The goal of this tool is to let people know when connections are initiated on their behalf -- with the goal being that if a connection occurs without the user knowing, they could contact their CIRT.

vpnnotify builds off of the support OpenVPN has for a client connect script. This script will run when a client successfully connects to the VPN. OpenVPN exposes several environment variables for the script it runs to use. The ones vpnnotify currently uses are common_name (the login name) and untrusted_ip (the IP of the connection).

There are many improvements that could be made to vpnnotify -- as it is, we know that this is fairly environment specific. We open sourced in hopes that we could help level up other security operations teams and make another tool that would contribute to the community.

In order to use vpnnotify you'll need to have the following:

• LDAP server with the slackUser object class
• Redis to store last logged in state
• OpenVPN - we've tested with 2.3.12 and later
• FQDNs that have either dev or prod in them as an indicator of environment

This adds a SlackName attribute to a record. If you use OpenLDAP with LDIF configuration, this schema LDIF will work:

dn: cn=slackuser,cn=schema,cn=config
objectClass: olcSchemaConfig
cn: slackuser
olcAttributeTypes: ( 1.3.6.1.4.1.48697.1.2.1.3.1 NAME 'slackName' DESC 'Slack
  at-name' EQUALITY caseIgnoreMatch SUBSTR caseIgnoreSubstringsMatch
  SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 SINGLE-VALUE)
olcObjectClasses: ( 1.3.6.1.4.1.48697.1.2.1.4.1 NAME 'slackUser' DESC 'Slack
  User' SUP top AUXILIARY MUST (slackName) )

Building vpnnotify is as easy as running go build. You could use FPM to make it into a package that could install to /usr/bin, if you wanted.

vpnnotify uses a configuration file which is, by default, in /etc/vpnnotify.json. You can override this with the VPNNOTIFY_CONFIG environment variable.

Here's a sample configuration file:

{
  "GeoIPEnabled": true,
  "GeoIPPath": "/opt/GeoLite2-City_20170502/GeoLite2-City.mmdb",
  "LDAPBaseDN": "dc=cool,dc=io",
  "LDAPPort": 389,
  "LDAPServer": "ldap.cool.io",
  "LDAPSkipVerify": false,
  "LDAPUserAttrib": "uid",
  "RedisDB": 0,
  "RedisPassword": "seCretsRc00l",
  "RedisPort": 6379,
  "RedisServer": "redis.cool.io",
  "RedisTLS": true,
  "RenotifyTime": 7200,
  "SlackKey": "xozz-blah-moreblah",
  "TemplatePath": "/etc/vpnnotify.msg"
}

This is where you actually put the message that will be sent via Slack. Here's a sample message template:

You just started a VPN session into *{{.Env}}* from {{.IP}}{{if eq .GeoIP true}} ({{if ne .City ""}}{{.City}}, {{end}}{{if ne .State ""}}{{.State}},{{end}}{{if ne .Country ""}} {{.Country}}{{end}}){{end}}. If this wasn't you, please reach out to ops immediately.

There aren't a lot of variables to use in the template. Here's what is available right now:

Set client-connect = /path/to/vpnnotify in your OpenVPN config. That's it.

You can run vpnnotify locally. On the command line, run VPNNOTIFY_CONFIG=./vpnnotify.json common_name=username untrusted_ip=8.8.8.8 ./vpnnotify which will simulate username logging into the VPN from 8.8.8.8.

When you test, you may want to set RenotifyTime shorter, depending on what you're testing.

There are a few things we know could use some improvement:

• We currently infer environment based on the OpenVPN host's hostname - maybe this should be done via the configuration file? (ideal for first time contributors!)
• We alert on the positive condition (known user successfully connects). What about users who don't have the slackUser attribute? Are there other negative conditions we're missing?
• vpnnotify is fairly unsophisticated. Some statistical analysis would be extremely helpful in dialing down "alert fatigue" with the caveat that any statistical analysis should not require too much "extra" to run

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