ACS System¶
About¶
WWIV now supports a simple expression language for supporting a basic Access Control System (ACS) to allow more fine grained access primitives for users on the BBS.
WWIV's ACS suppors the following objects:
| Name | Description |
|---|---|
| User | Provides attributes about the current user |
| System | Provides attributes about the bbs |
Syntax¶
The ACS language allows conditional attribute-based access control for WWIV BBS system
resources, such as message areas, conferences, file areas, chains, and menu items.
This allows the system to specify the conditions in a free-form DSL language that
determines if access is granted.
Language Elements¶
WWIV's ACS grammar is comprised of:
- Comparison Operators
- Logical Operators
- Object Attributes
- Expressions
Data Types¶
ACS support the following datatypes:
| Name | Description |
|---|---|
| Number | An integer value of 32 bits in size |
| String | A variable length set of CP437 characters |
| Boolean | Support either true of false. Convertible to Numbers as 0 and 1 |
| Ar | Contains the set of Ar values, supports equality checks against single Ar value specified as a string or character. |
Operators¶
OP ::= COMPARE_OP | LOGICAL_OP
Only Binary Operators are supported in ACS. The operators may be either a comparison operator or a logical operator.
Comparison Operators¶
LHS COMPARE_OP RHS
Comparison Operators are binary operators that compare the values of both operands and return a true or false boolean value.
WWIV ACS supports the following Comparison Operators with LHS as the Left
Hand Side operand and RHS as the right hand side operand:
| Name | Symbol | Description |
|---|---|---|
| Greater Than | > |
True if LHS > RHS |
| Greater Than or Equal | >= |
True if LHS >= RHS |
| Less Than | < |
True if LHS < RHS |
| Less Than or Equal | <= |
True if LHS <= RHS |
| Equal | == |
True if LHS == RHS |
| Not Equal | != |
True if LHS != RHS |
Example:
user.sl > 100
Logical Operators¶
LHS LOGICAL_OP RHS
The name logical comes from boolean logic, although the operands on either side of the operator may be an expression or type that evaluates independently to a boolean.
WWIV ACS supports the following Logical Operators:
| Name | Symbol | Description |
|---|---|---|
| AND | && |
Both operands must evaluate to true for the result to be true. |
| OR | || |
At least one operand must evaluate to true for the result to be true. |
Example:
user.sl > 100 || user.ar == 'A'
Expression¶
OP ::= COMPARE_OP | LOGICAL_OP
EXPRESSION ::= EXPRESSION (OP EXPRESSION)?
The language is designed to evaluate a single expression. An expression may be
a compound expression with multiple expressions combined using logical
AND && or OR || operators.
Object Attributes¶
WWIV ACS supports attributes in the form
Object.Attribute. For example "user.sl" is the current user's security level.
Note: Object and attribute names are case-insensitive, so
both user.name and USER.NAME are equivalent.
| Attribute | Description |
|---|---|
| user.sl | User's message area security level |
| user.dsl | User's download area security level |
| user.ar | Users' download area Access Rights/Flag |
| user.dar | Users' download area Access Rights |
| user.name | User's name or handle (not real name) |
WWIV Security Attributes¶
SL AND DSL¶
Security Level (SL) and Download Security Level (DSL) are the primary ways to secure functionality in WWIV. Historically new users will have SL and DSL of 10, then validated users get 20 or 50 depending on the setup. Many modern setups grant 20-50 on the first call so people can see more of the BBS without needing to call back.
AR AND DAR¶
AR and DAR allow access specific activities (subboards, download subboards, chains, etc) when other attributes (like age, or security level), wouldn't be the choice, as that may apply to many more BBS callers than needed.
For example: Let's say you have a group of OS/2 callers on your bbs, selecting them by age or security level (SL) would not be appropriate. This is where AR works perfectely. There are 16 AR and DAR flags (A-P) that you can add as arestriction using the ACS language and also then grant this AR or DAR to the BBS callers to grant access to this area.
You use the user editor to grant AR and DAR to callers, and using ACS, add a condition requiring it for an area in the BBS.
Examples¶
Grant access to users with SL of 100 or more or AR of 'A':
user.sl >= 100 || user.ar == 'A'
Grant access to users with SL of 20 or less, and also to Rushfan.
user.sl <= 20 || user.name == "Rushfan"