Decision Files

Expressions

The simplest expression would be a comparison of two A-V pairs with one relative operator. You can use relative and Boolean operators to create an expression with various combinations of A-V pairs and comparisons. The following operators may be used:

You can also use parentheses to nest expressions, and line breaks are not significant.

For example, suppose you wanted to control access according to the dial-in phone number and time called. The following table illustrates some possible expressions:

Your expressions may be as short or as long as you like. Since only one group match can be made for each request, you may want to use shorter expressions and manage each distinct decision (DNIS routing, dynamic access control, membership in groups, etc.) in a separate file; however, it would be possible to create a single file with longer expressions that covered a wide range of decision criteria.

Specifying Attributes in Group Entries

You can create decision groups for provisioning with the A-V pairs that may be used in a user profile for session logging with accounting attributes, refer to Chapter 7 “Logging and Monitoring ”. In addition, you can use the following attributes to define a group condition or reply.

Using Indirection

You may also use indirection to compare or assign attribute values to each other. Follow a Test Operator $Value$Pos$Len syntax, where Test is the attribute to check or assign a value to, and Value is the attribute with the value to check against or assign to the Test attribute; Operator is the relative or Boolean operator to use. $Pos and $Len are optional parameters that allow you to test or assign a substring of the specified Value attribute. Pos indicates the index position in the attribute's value to begin the substring and if specified Len determines the length.

When used in the condition section of a group entry, indirection checks values. When used in the reply section, it assigns a value. For example, in an expression Port-Id <= $Port-Limit would only allow access to users who access the server through ports that don't exceed the limit set in their profile. As a reply item Decision = $Interlink-Proxy-Action would assign the current FSM event to the Decision attribute.

	NOTE: Test = $Value$Pos$Len will add a new A-V pair to the request. It will not update an existing pair. For example, when the request includes a Test = "String" A-V pair, the expression Test = $Test$2$3 will append Test = "rin" to the request, which results in both Test = "String" and Test = "rin" in the request. Because the left-side attribute is handled differently than the right-side attribute value, multiple attributes in a request can cause some unexpected indirection results. Each instance of the left-side attribute is AND'd, but only the value of the right-side attribute's last instance is used. For example, the expression Test < $Test would evaluate to FALSE as (Test1 < 1) && (Test2 < 1) when the request contains the A-V pairs Test1 = 1 and Test2 = 2.

Example Group Entries

The HP-UX AAA server includes two sample decision files:

DNIS.grp for DNIS Routing

This example shows a simple DNIS routing scheme. Refer to Chapter 7 “Logging and Monitoring ” for an example of a modified radius.fsm file that will work with this decision file.

1 Group Controlled-Access { 2 Condition { 3 (Calling-Station-Id = 1234567890) || 4 (Called-Station-Id = 8005551212) 5 } 6 Reply { 7 Authentication-Type = radius 8 Server-Name = flatland.com 9 Server-Port = 1812 10 Decision = Forward 11 } 12 } 13 Group Denied-Access { 14 Condition { 15 Called-Station-Id = 8001234567 16 } 17 Reply { 18 Authentication-Type = blackhole 19 Decision = Abandon 20 } 21 } 22 Group NORMAL { 23 Reply { 24 Decision = $Interlink-Proxy-Action 25 } 26 }

Line 1

Names the first group entry Controlled-Access.

Lines 2 to 5

If the user calls from 1234567890, or calls into 8005551212, the user belongs to this group.

Lines 7 to 9

The Authentication-Type attribute indicates that requests from members of this group should be proxied. The Server-Name and Server-Port attributes specify flatland.com:1812 as the remote server that should receive the proxied request.

Line 10

The Decision attribute returns the Forward value to the FSM as an event. The radius.fsm file must be modified to recognize this event and to call the RADIUS module when it occurs, refer to Chapter 7 “Logging and Monitoring ”.

Line 13

Names the second group entry Denied-Access.

Lines 14 to 16

If the user calls into 8001234567, the user belongs to this group.

Lines 18

The Authentication-Type attribute indicates that the request should be ignored.

Line 19

The Decision attribute returns the Abandon value to the FSM as an event. The radius.fsm file must be modified to recognize this event to end the request when it occurs, refer to Chapter 7 “Logging and Monitoring ”.

Line 22

Names the third group Normal. Since this group entry does not include a condition section, all requests that have not been matched to the previous two groups will be matched to this group.

Line 24

This line uses indirection to pass the current event ($Interlink-Proxy-Action) to the FSM, so the server will handle the request as if DNIS routing did not occur.

DAC.grp for Dynamic Access Control

This example shows a simple DAC decision scheme based on the value of an Access-Group attribute.

• Allow access to users in the weekday group during a weekday

• Allow access to users in the daytime group during the day

• Allow access to users in the nighttime group during the night

• Otherwise, deny access to users

Refer to Chapter 7 “Logging and Monitoring ” for an example of a modified radius.fsm file that will work with this decision file. In addition, this decision file would only work if the Access-Group attribute were added to the dictionary and added to user profiles as a configuration item, refer to “dictionary ”.

1 Group Weekday-Access { 2 Condition { 3 (Access-Group = weekday) && 4 ((Day-Of-Week >= Monday) && (Day-Of-Week <= Friday)) 5 } 6 Reply { 7 Decision = ACK 8 Reply-Message = "Weekday access allowed" 9 } 10 } 11 Group Daytime-Access { 12 Condition { 13 (Access-Group = daytime) && 14 ((Time-Of-Day >= 06:00) && (Time-Of-Day <= 20:00)) 15 } 16 Reply { 17 Decision = ACK 18 Reply-Message = "Daytime access allowed" 19 } 20 } 21 Group Nighttime-Access { 22 Condition { 23 (Access-Group = nighttime) && 24 ((Time-Of-Day < 06:00) || (Time-Of-Day > 20:00)) 25 } 26 Reply { 27 Decision = ACK 28 Reply-Message = "Nighttime access allowed" 29 } 30 } 31 Group Denied-by-timed-access { 32 Reply { 33 Decision = NAK 34 Reply-Message = "Time-Based access denied" 35 } 36 }

Line 1

Names the first group entry Weekday-Access.

Lines 2 to 5

If the user belongs to the weekday access group and calls on a weekday they belong to this group.

Line 7

The Decision attribute returns the ACK value to the FSM as an event, which will accept the request.

Line 8

Specifies a message that will be sent back to the user.

Lines 11 to 30

Define the second and third groups with a structure similar to the first group entry.

Line 31

Names the fourth group Denied-by-time-access. Since this group entry does not include a condition section, all requests that have not been matched to the previous two groups will be matched to this group.

Line 33

The Decision attribute returns the NAK value to the FSM as an event, which will reject the request.

Line 34

Specifies a message that will be sent back to the user.