Knockknock mac program5/30/2023 ![]() There are some more rules required that prevent such scans of the full port range and so after some more rules the full port knocking ruleset looks like shown in the following screenshot:Īfter each rule where a door can be opened there is another drop-rule that will match for all other ports than the one which is required to access the next door. These rules so far enable a port knocking feature where a «brute forcing» is still possible as a source IP could scan all the ports multiple times until the actual GlobalProtect ports are opened. So I specified the different groups with the negate option for the source IPs. In addition, the first rule only has to match if the source IP has not already arrived at one of the other doors. In these six rules, I specified the different dynamic address groups as source. After each port the next door will be opened. As I wanted five doors to be opened I need only for these five different rules where I specify different ports that need to be knocked on. The next step is to create the required security policy rules to configure this port knocking access. ![]() For example, for the group Gr_Door_1_opened the tag «Door 1» is used as filter and so on: With these tags I created dynamic address groups for each of these tags:įor every one of these dynamic address groups there is the one matching tag criteria. So I started with creating some tag objects which I will use later: If this port is not guessed correctly at the first try, the IP will be locked out to make it virtually impossible to brute force this port knocking mechanism. I wanted to implement a mechanism that there is only one guess for the port which will be knocked on. This chance is low enough to me so I went this way with a little adjustment. I wanted to have five stages or doors that need to be opened prior to being able to establish a VPN connection. So, I brought this theory to the next level. So right know the chance for a successful attack is 1:131072 (65536 tcp ports and 65536 TCP ports) or actually pretty much higher as really only a simple port scan is required. Unfortunately this was still not secure enough to me as a port scan of all TCP and UDP ports is done pretty fast and after that also an attacked would be able to reach my GlobalProtect Gateway IP-even though the attacker still has no credentials to access the internal network with a VPN tunnel. So far, pretty easy: I send a TCP-SYN to a specific port and after that I am able to connect withGlobalProtect. ![]() On this rule, I configured a logforwardingprofile with a built in action to tag the source IP which is then added to an address group that is allowed to connect to GlobalProtect. I created a deny firewallrule with a specific port and my GlobalProtect Gateway IP as Destination IP. In the past, I used the built in actions in log-forwarding profiles (logforwardingprofile) to dynamically add some IPs to special decryption rules where the cert validation was disabled, so I started with this here too. With this in mind I searched for a way to implement that. At the beginning, I wrote the keyword port knocking. Prior to this idea, I was working with geolocations but even this restriction was not good enough for me (a very paranoid person in some situations). I don’t want this VPN gateway to be discoverable by anyone. In my example I will secure my global protect access. Even if you're not looking for this creative solution, this post offers ideas and possibilities when using a Palo Alto firewall (and might lead to even better use cases). This access is not detectable by any scans-which happen continuously in the internet (for example from shodan.io or actual threat actors)-and at the same time, it's easy to use and enables access from anywhere sans an IP address. With features included in PAN-OS without any additional subscription, it is possible to secure a critical access. If this sounds familiar to you, then this post is for you. ![]() This blog was written by Cyber Elite member you ever seen a port-knocking feature on other firewalls or router vendors and were looking for something similar on Palo Alto Networks? Or were you searching for a way to secure and emergency access to a critical server, or even to the firewall interface over the internet-but you don't want to expose this to the complete internet, Actually, you don’t want do expose it at all. ![]()
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