Rules

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Rules

Rules are used frequently in Untangle and many other firewalls. Rules are very powerful, but can sometimes be difficult to configure. This documentation describes how rules work and gives some basic examples and some common mistakes to avoid. Many applications use rules like Firewall, Captive Portal, Application Control, Bandwidth Control, etc. All of these rules essentially share the same logic.

Basics

Rules are configured by the user to categorize and act upon traffic. For example, Firewall uses rules to determine whether to block or pass traffic. Bandwidth Control uses rules to determine how to prioritize a session.

Rules are evaluated in order from top to bottom against sessions (not packets!). If a rule matches then the action from that rule is performed and no more rules are evaluated. If no matching rule is found the behavior is defined by the application, which is usually doing nothing.

This is similar to other firewalls. Untangle rules are "quick" rules which means the first match is always used. Unlike some other firewalls, Untangle evaluates against sessions, not packets. This means that the "Source Address" will be the initiator of the session and the "Destination Address" will be the server address the client is connecting to, and the same is true for "Source Port" and "Destination Port."

Each rule has several properties:

  • An enable checkbox
  • A name/description
  • A set of conditions
  • An action or set of actions
Rule Anatomy

The enable checkbox determines if the rule is evaluated. If the enable checkbox is not checked, the rule is simply skipped.

The description is for the user to document what the rule does. It is highly suggested to give the rule a meaningful name. Trying to troubleshoot a set of rules all named "[no description]" can be extremely difficult.

The set of conditions is the description of the traffic that should match the rule. If all of the conditions are true for the given session then the rules matches. This is discussed in more details in the next section.

The action or set of actions configures what action is performed if the rule matches. This is dependent on the application. For example, in Firewall it determines whether to block or pass the session and additionally if it should be flagged.

Conditions

Conditions define which sessions will match the rule. If and only if all of the conditions match, the rule is considered a match. Conditions can also be inverted by selecting "is NOT" in the dropdown, effectively inverting when it matches. Destination Port "is NOT" "80" matches on all ports except port 80.

Lets take a simple example: We want to block TCP traffic to port 80 on a server. There is a web service running on that server that you don't want to allow access to. First, create a rule and check the enable checkbox and give it a reasonably descriptive name like "blocking TCP port 80 to serverX." Now you will need to add some conditions that match only the traffic you want to block. So in this example will will add:

  • Protocol is TCP
  • Destination Address is 1.2.3.4 (The IP address of the server)
  • Destination Port is 80

Finally, set the action to block and flag, and click "Done" and "Apply". Since all conditions must be true this rule will block TCP traffic to 1.2.3.4 port 80 only and nothing else.

Rule Conditions

There are many conditions available to carefully define precise sets of traffic. The following Table defines the list of conditions.

Each condition has several properties:

  • Name - The Name of the condition
  • Syntax - The accepted Syntax of the condition. If editing through the UI, some conditions have custom editors to help you craft conditions, others are just a text field.
  • Availability - The Availability is the availability of that matcher at various times. Some conditions, like Destination Address, are always known and can always be used to match. Other conditions, like Application Control: Application, are only known after the session is created and some data flows and Application Control is able to identify the application. These type conditions are 'deep session' conditions because they are not able to be evaluated at session creation time, only after some data flows. As such they are not available in rules that are evaluated at session creation time, like Firewall and Captive Portal.
  • Reliability - The Reliability is a "reliability" of that condition. True means it is 100% reliable. False means it is 99% or less reliable. For example, some conditions, like Destination Port, are always known and thus matching on Destination Port is 100% reliable. Other conditions, like Client Hostname, only match if the hostname for the client hostname is known. Hostname is determined through many ways, including DNS and DHCP. If all of these methods fail then it is entirely possible that the hostname of a server is "foo" but Untangle has not been able to determine this and as such a Client Hostname is "foo" condition will not match. This column is there purely as a warning that users in these cases must be aware of when conditions might deliver false negatives.

Condition List

Name Syntax Function Availability Reliability
Destination Address IP Matcher Matches if value matches the Destination/Server Address of the session. (after NAT/port forwarding) all True
Destination Port Int Matcher Matches if value matches the Destination/Server Port of the session. (after NAT/port forwarding) all True
Destination Interface checkboxes Matches if value matches the Destination/Server Interface of the session. (after routing/port forwarding) all True
Destined Local boolean Matches if the session is destined to one of Untangle's IP addresses. all True
Source Address IP Matcher Matches if value matches the Source/Client Address of the session. (before NAT/port forwarding) all True
Source Port Port Matcher Matches if value matches the Source/Client Port of the session. (before NAT/port forwarding) hidden True
Source Interface checkboxes Matches if value matches the Source/Client Interface of the session. (before routing/port forwarding) all True
Protocol checkboxes Matches if value matches the Protocol of the session. all True
Tagged Glob Matcher Matches if session is tagged with matching tag all True
Client Tagged Glob Matcher Matches if client of the session is tagged with matching tag all True
Server Tagged Glob Matcher Matches if server of the session is tagged with matching tag all True
Username User Matcher Matches if value matches the username associated with the Client IP in the Host table. all False
Host Hostname Glob Matcher Matches if value matches the hostname associated with the Local Address in the Host table. all False
Client Hostname Glob Matcher Matches if value matches the hostname associated with the Client IP in the Host table. all False
Server Hostname Glob Matcher Matches if value matches the hostname associated with the Server IP in the Host table. all False
Client MAC Address Glob Matcher Matches if value matches the MAC address associated with the Client IP in the ARP table. all False
Server MAC Address Glob Matcher Matches if value matches the MAC address associated with the Server IP in the ARP table. all False
Client MAC Vendor Glob Matcher Matches if value matches the device manufacturer. This is identified using the Client IP's MAC address in the ARP table and OUI Lookup. all False
Server MAC Vendor Glob Matcher Matches if value matches the device manufacturer. This is identified using the Server IP's MAC address in the ARP table and OUI Lookup. all False
Host has no Quota boolean Matches if the local address has no quota all True
User has no Quota boolean Matches if the username has no quota all True
Client has no Quota boolean Matches if the client has no quota hidden True
Server has no Quota boolean Matches if the server has no quota hidden True
Host has Exceeded Quota boolean Matches if the local address has exceeded their quota all True
User has Exceeded Quota boolean Matches if the user has exceeded their quota all True
Client has Exceeded Quota boolean Matches if the client has exceeded their quota hidden True
Server has Exceeded Quota boolean Matches if the server has exceeded their quota hidden True
Host Quota Attainment Int Matcher Matches the local address quota used to quota size ratio (">1" means over quota, ">.5" means over 50% used, etc) all True
User Quota Attainment Int Matcher Matches the username quota used to quota size ratio (">1" means over quota, ">.5" means over 50% used, etc) all True
Client Quota Attainment Int Matcher Matches the client quota used to quota size ratio (">1" means over quota, ">.5" means over 50% used, etc) hidden True
Server Quota Attainment Int Matcher Matches the server quota used to quota size ratio (">1" means over quota, ">.5" means over 50% used. etc) hidden True
HTTP: Hostname Glob Matcher Matches if the value matches the hostname specified in the HTTP session deep sessions False
HTTP: Referer Glob Matcher Matches if the value matches the referer string specified in the HTTP header deep sessions False
HTTP: URI Glob Matcher Matches if the value matches the latest URI specified in the HTTP session deep sessions False
HTTP: URL URL Matcher Matches if the value matches the latest URL (hostname+URI) specified in the HTTP session deep sessions False
HTTP: Content Type Glob Matcher Matches the content-type of the latest content in the HTTP session deep sessions False
HTTP: Content Length Int Matcher Matches if Int Matcher matches the content length specified in the latest HTTP response deep sessions False
HTTP: Request Method Glob Matcher Matches if the value matches the HTTP request method of the requested URL. Standard request methods include GET, POST, HEAD, OPTIONS, PUT, DELETE, TRACE, and CONNECT. deep sessions False
HTTP: Request File Path Glob Matcher Matches if the value matches the entire file path of the requested URL. This is everything including and after the first slash character following the host name or address. (e.g. /some/location/mypage.html) deep sessions False
HTTP: Request File Name Glob Matcher Matches if the value matches the file name of the requested URL. This is everything after the final slash character of the request. (e.g. mypage.html) deep sessions False
HTTP: Request File Extension Glob Matcher Matches if the value matches the file extension of the requested URL. This is everything after following the dot after the final slash character of the request. (e.g. html) deep sessions False
HTTP: Response Content Type Glob Matcher Matches if the value matches the content or MIME type reported in the server response. deep sessions False
HTTP: Response File Name Glob Matcher Matches if the value matches the file name returned in the server response. deep sessions False
HTTP: Response File Extension Glob Matcher Matches if the value matches the file extension returned in the server response. This is everything after (but not including) the final dot of the file name. deep sessions False
HTTP: Client User Agent Glob Matcher Matches if the value matches the User Agent string for the client in the Host table all False
Application Control: Application Glob Matcher Matches if the value matches the Application determined by Application Control deep sessions False
Application Control: Category Glob Matcher Matches if the value matches the Category of the Application determined by Application Control deep sessions False
Application Control: Protochain Glob Matcher Matches if the value matches the Protochain determined by Application Control deep sessions False
Application Control: Detail Glob Matcher Matches if the value matches the Detail of the Application determined by Application Control deep sessions False
Application Control: Confidence Int Matcher Matches if Int Matcher matches the confidence rating determined by Application Control deep sessions False
Application Control: Productivity Int Matcher Matches if Int Matcher matches the productivity rating determined by Application Control deep sessions False
Application Control: Risk Int Matcher Matches if Int Matcher matches the risk rating determined by Application Control deep sessions False
Application Control Lite: Signature Glob Matcher Matches if the value matches the Signature determined by Application Control Lite deep sessions False
Application Control Lite: Category Glob Matcher Matches if the value matches the Category of the Signature determined by Application Control Lite deep sessions False
Application Control Lite: Description Glob Matcher Matches if the value matches the Description of the Signature determined by Application Control Lite deep sessions False
Web Filter: Category Glob Matcher Matches if the value matches the Category determined by Web Filter deep sessions False
Web Filter: Category Description Glob Matcher Matches if the value matches the Description of the Category determined by Web Filter deep sessions False
Web Filter: Site is Flagged boolean Matches if the latest request in this session was flagged by Web Filter deep sessions False
Directory Connector: User in Group Group Matcher Matches if the username associated with the client in the Host Table is in the specified group(s) all False
SSL Inspector: SNI Host Name Glob Matcher Matches if the value matches the Server Name Indication (SNI) host name included by the client in the initial session request. deep sessions False
SSL Inspector: Certificate Subject Glob Matcher Matches if the value matches the Subject DN in the SSL certificate received from the external server. all False
SSL Inspector: Certificate Issuer Glob Matcher Matches if the value matches the Issuer DN in the SSL certificate received from the external server. all False
Time of Day Time of Day Matcher Matches times of day. all True
Day of Week Day of Week Matcher Matches days of the week. all True
Remote Host Country Glob Matcher Matches if value matches the country associated with the remote IP. all False
Client Country Glob Matcher Matches if value matches the country associated with the Client IP. all False
Server Country Glob Matcher Matches if value matches the country associated with the Server IP. all False

Order

As discussed above, the order of rules is very important. Often users want to do very complex tasks that can be difficult or impossible with a single rule. In these cases, multiple rules is useful. For example, assume you want to use Firewall to block all traffic to a server (1.2.3.4) except port 80 traffic or from the admin IP (192.168.1.100) to RDP (port 3389).

Doing this in one rule would be difficult (actually impossible in this case), but it is quite easy using several rules: First, create a rule to just block all traffic to the server IP, 1.2.3.4. Above that rule create a rule that passes all traffic from the admin IP, 192.168.1.100, to the server IP where Destination Port == "3389", and another rule that passes all traffic to 1.2.3.4 with Destination Port == "80." This set of three rules does exactly what we describe above and effects no other traffic.

Rule Anatomy

Common Mistakes

This is a list of common mistakes to avoid.

Conditions must ALL match

In order for a rule to match, ALL conditions must match. In some cases you may want to add a rule that just passes all traffic to and from an IP. Users sometimes will create a pass rule with two conditions:

  • Destination Address is "1.2.3.4"
  • Source Address is "1.2.3.4"

This rule will never match anything because it will only match traffic where the destination address is 1.2.3.4 AND the source address is 1.2.3.4 (a session destined to itself). If you want to match when the destination address is 1.2.3.4 OR the source address is 1.2.3.4, then you must create two separate rules, one for the destination address and one for the source address.

Rule Order

Occasionally, you will add a rule and not understand why it is not working as intended. Often we find that there was a rule above that was matching the session before the desired rule. For example, just adding a rule to the bottom often isn't sufficient, you must find the appropriate place in your ruleset to place the new rule.

To do so simply logically evaluate the rules in your head starting at the top to find the appropriate place for your rule. Also use the event log to run several tests to see how the session was handled in the event log and adjust your ruleset accordingly.