ABAC XacmlPolicy attribute dictionary helper method (#492)

* ABAC XacmlPolicy attribute dictionary helper method
#474

As part of the integration with OED/DD (Digitalt dødsbo) as a new external role provider, an easy way to analyse and extract all attributeIds and values from a XacmlPolicy is needed.
This will be used to evaluate whether or not the policy contains a subject attribute for an OED/DD role code, and since it's populated to the XacmlPolicy object it will be cached along side policy itself.

The logic can later be reused by the resource-registry which will need same logic for analysing the policy for building rolecode register and required validation logic when publishing a resource.

* fixed inconsistent Collection -> ICollection datatype usage

* simplified complexity of dictionary builder

* Increment ABAC package version to 0.0.6

---------

Co-authored-by: Jon Kjetil Øye <acn-joye@ai-dev.no>

src/Altinn.Authorization.ABAC/Altinn.Authorization.ABAC.csproj

@@ -3,14 +3,14 @@
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
     <OutputType>Library</OutputType>
-    <AssemblyVersion>0.0.0.5</AssemblyVersion>
-    <FileVersion>0.0.0.5</FileVersion>
+    <AssemblyVersion>0.0.0.6</AssemblyVersion>
+    <FileVersion>0.0.0.6</FileVersion>
     <!-- SonarCloud requires a ProjectGuid to separate projects. -->
     <ProjectGuid>{C9ABF5DB-928C-4280-B587-13E6DCE010BC}</ProjectGuid>
 
     <!-- NuGet package properties -->
     <PackageId>Altinn.Authorization.ABAC</PackageId>
-    <PackageVersion>0.0.5</PackageVersion>
+    <PackageVersion>0.0.6</PackageVersion>
     <PackageTags>Altinn;Authorization;ABAC</PackageTags>
     <Description>
       Attribute Based Access Control library for .Net Core implementing XACML 3.0 xml and JSON Profile.

src/Altinn.Authorization.ABAC/Xacml/XacmlPolicy.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Linq;
+using Altinn.Authorization.ABAC.Constants;
 using Altinn.Authorization.ABAC.Utils;
 
 namespace Altinn.Authorization.ABAC.Xacml
@@ -96,6 +98,8 @@ public class XacmlPolicy
 
         private readonly ICollection<XacmlVariableDefinition> variableDefinitions = new Collection<XacmlVariableDefinition>();
 
+        private readonly IDictionary<string, IDictionary<string, ICollection<string>>> categoryAttributes = new Dictionary<string, IDictionary<string, ICollection<string>>>();
+
         private XacmlTarget target;
         private Uri policyId;
         private Uri ruleCombiningAlgId;
@@ -308,6 +312,44 @@ public ICollection<XacmlAdviceExpression> AdviceExpressions
             }
         }
 
+        /// <summary>
+        /// Returns a dictionary of all unique attribute ids and a collection of all their values, which exists across all rules in the policy, for a given match attribute category.
+        /// </summary>
+        /// <param name="matchAttributeCategory">The Xacml match attribute category to collect attributes values of</param>
+        /// <returns>Dictionary of attribute ids and list of values</returns>
+        public IDictionary<string, ICollection<string>> GetAttributeDictionaryByCategory(string matchAttributeCategory)
+        {
+            if (categoryAttributes.ContainsKey(matchAttributeCategory))
+            {
+                return categoryAttributes[matchAttributeCategory];
+            }
+
+            IDictionary<string, ICollection<string>> categoryAttributeDict = new Dictionary<string, ICollection<string>>();
+            categoryAttributes.Add(matchAttributeCategory, categoryAttributeDict);
+
+            foreach (XacmlRule r in Rules.Where(r => r.Target != null))
+            {
+                foreach (XacmlAnyOf anyOf in r.Target.AnyOf)
+                {
+                    foreach (XacmlAllOf allOf in anyOf.AllOf)
+                    {
+                        foreach (XacmlMatch xacmlMatch in allOf.Matches.Where(xm => xm.AttributeDesignator.Category.Equals(matchAttributeCategory)))
+                        {
+                            string attributeId = xacmlMatch.AttributeDesignator.AttributeId.AbsoluteUri;
+                            if (!categoryAttributeDict.ContainsKey(attributeId))
+                            {
+                                categoryAttributeDict.Add(attributeId, new Collection<string>());
+                            }
+
+                            categoryAttributeDict[attributeId].Add(xacmlMatch.AttributeValue.Value);
+                        }
+                    }
+                }
+            }
+
+            return categoryAttributes[matchAttributeCategory];
+        }
+
         /// <summary>
         /// The namespaces used in Policy
         /// </summary>