CSG 379 Midterm
====================================================

Karl Lieberherr                 October 2004

Question 1:
===========
19 UNKNOWNs, 3 points each

Consider the following class dictionary,
program, input and output:
Find the UNKNOWNs in the program.

The programs checks the simple Chinese Wall Policy
from hw 4.
Note that the class dictionary has been improved at several places.
It is recommended that you study the class dictionary carefully.
The key changes:
We can now deal with multiple transitions. The state also stores
the previous conflict of interest types.

Also note that the program executes multiple automata.

The following was used to compile:
dajc program.cd *.java *.trv

The following was used to run:
daj Main program.input


///////////////////////////////////////////////
// program.cd
// Security Automaton extended for Chinese Wall Policy
// for one subject

ChineseWallPolicyChecker = List(ChineseWallAutomaton) EOF.
ChineseWallAutomaton = "Chinese" "Wall" "automaton" AutomatonName 
  "currentState" <currentState> State
  ["startState" <startState> State] 
  ["transitions" <transition> List(Transition)]
  "groups" <groups> List(Group)
  "citypes" <citypes> List(CIType)
  "history" <history> List(Access).

State = <g_accesses> List(Group) <t_accesses> List(CIType).
Access = ObjektId "group" Group.
Group = GroupName ["citype" CIType].
CIType = CITypeName.

Transition = <newAccess> Access.
// has boolean exec() method that checks Chinese Wall Policy:
// newAccess.group gives group g1
// if g1 in ChineseWallPolicyChecker.currentState ok else
// if g1.citype is different from previous types ok else denied

ObjektId = Ident.
GroupName = Ident.
CITypeName = Ident.
AutomatonName = Ident.

List(S) ~ "(" {S} ")". 


///////////////////////////////////////////////
// Main.java
import edu.neu.ccs.demeter.*;
import java.io.File;

class Main {
  protected String s;
  public Main(String s) {
    super();
    this.s = s;
  }
  
  public static void main(String args[]) throws Exception {
    ChineseWallPolicyChecker m = 
      ChineseWallPolicyChecker.parse(new File(args[0]));
    m.UNKNOWN1();
    System.out.println("done");
  }
}

///////////////////////////////////////////////
// Execute.trv
aspect Execute{
  declare strategy: eachAutomaton: 
    "UNKNOWN2";
    declare traversal :
	   void execAutomata(): eachAutomaton(ExecVisitor);
  declare strategy: eachGroupName:
    "UNKNOWN3";
  declare traversal :
    CIType findCIType(String groupName): 
      eachGroupName(FindCIVisitor);
}
///////////////////////////////////////////////
// ExecVisitor.java
import edu.neu.ccs.demeter.*;
import java.io.File;
class FindCIVisitor {
  FindCIVisitor(String grpN){
    groupName = grpN;
  }
  String groupName;
  Group currentGroup;
  Group result;
  void before (Group host) {
    currentGroup = host;
  }
  void before (GroupName host) {
    if (host.ident.toString().equals(groupName)) {
      result = currentGroup;
    };
  }
  Object getReturnValue() {return result.cIType;}
}

class ExecVisitor {
  ChineseWallAutomaton current;
  void before (ChineseWallAutomaton host){
    UNKNOWN4;
    System.out.println();
    System.out.println(host.automatonName.ident + " automaton name ");
    System.out.println();
  }

  void before (Transition host){
    Group g1 = host.newAccess.group;
    Group_List cgl = 
      current.currentState.g_accesses;
    CIType_List ctl = 
      current.currentState.t_accesses;
    boolean ok = false;

    // cit will be defined and used only if not ok
    CIType cit = new CIType(null); 

    if (UNKNOWN5) {
      System.out.println(" ok: group found +++++++++++++ ");
      ok = true;
    } else { 
	System.out.println(" group NOT found "); 
	cit = UNKNOWN6.UNKNOWN7.UNKNOWN8
	  (g1.groupName.ident.toString());
	System.out.println(" search for CIType of group " +
	  g1.groupName.ident.toString()); 
	System.out.println(" found CIType = " +
	  cit.cITypeName.ident.toString()); 

        if (UNKNOWN9) {
	  System.out.println(" not ok: conflict of interest ");
	  ok = false;
        } else ok = true;
    }
    if (!ok) {
      System.out.println(" Chinese Wall Violation !!!!!!!! ");
    } else {
      int g_accessCount = cgl.size();
      System.out.println(g_accessCount + 
        " number of groups accessed in current state ");
      // add to lists
        cgl.add(new Group(g1.groupName,null));
	ctl.add(new CIType(cit.cITypeName));
      System.out.println(" added to current state ");
      g_accessCount = cgl.size();
      System.out.println(g_accessCount + 
        " number of groups accessed in next state ");
    }
  }
}
///////////////////////////////////////////////
// InterType.java
aspect InterType {
  public boolean Group.equals(Object g){
    System.out.println(" compare " + 
    UNKNOWN10.UNKNOWN11.UNKNOWN12.toString() 
    + " with " + 
    ((Group) g).UNKNOWN13.UNKNOWN14.toString());
    return (UNKNOWN15.UNKNOWN16.UNKNOWN17.toString().equals(
	       ((Group) g).UNKNOWN18.UNKNOWN19.toString()));
  }
  public boolean CIType.equals(Object g){
    System.out.println(" compare " + 
    this.cITypeName.ident.toString() 
    + " with " + 
    ((CIType) g).cITypeName.ident.toString());
    return (this.cITypeName.ident.toString().equals(
	       ((CIType) g).cITypeName.ident.toString()));
  }
}
///////////////////////////////////////////////
(
Chinese Wall automaton consultant_Mary
currentState
  (Shell) (Oil)
startState
  () ()
transitions
  (oid_research group Mobil x group UBS y group ZKB)
groups
  (Shell citype Oil Mobil citype Oil UBS citype Bank ZKB citype Bank)
citypes
  (Oil Bank)
history
  (oid1 group Shell oid2 group Shell oid3 group Shell)

Chinese Wall automaton consultant_John
currentState
  (Winterthur UBS) (Insurance Bank)
transitions
  (oid_research group AllState x group UBS) 
groups
  (AllState citype Insurance Winterthur citype Insurance UBS citype Bank)
citypes
  (Insurance Bank Retail WholeSale)
history
  (oid1 group Winterthur oid3 group UBS )

Chinese Wall automaton consultant_Karl
currentState
  (Shell) (Oil)
transitions
   (oid_research group Mobil x group Shell y group Shell z group Mobil)
groups
  (Shell citype Oil Mobil citype Oil UBS citype Bank)
citypes
  (Oil Bank)
history
  (oid1 group Shell oid2 group Shell oid3 group Shell)
)

///////////////////////////////////////////////
// output


consultant_Mary automaton name 

 compare Mobil with Shell
 group NOT found 
 search for CIType of group Mobil
 found CIType = Oil
 compare Oil with Oil
 not ok: conflict of interest 
 Chinese Wall Violation !!!!!!!! 
 compare UBS with Shell
 group NOT found 
 search for CIType of group UBS
 found CIType = Bank
 compare Bank with Oil
1 number of groups accessed in current state 
 added to current state 
2 number of groups accessed in next state 
 compare ZKB with Shell
 compare ZKB with UBS
 group NOT found 
 search for CIType of group ZKB
 found CIType = Bank
 compare Bank with Oil
 compare Bank with Bank
 not ok: conflict of interest 
 Chinese Wall Violation !!!!!!!! 

consultant_John automaton name 

 compare AllState with Winterthur
 compare AllState with UBS
 group NOT found 
 search for CIType of group AllState
 found CIType = Insurance
 compare Insurance with Insurance
 not ok: conflict of interest 
 Chinese Wall Violation !!!!!!!! 
 compare UBS with Winterthur
 compare UBS with UBS
 ok: group found +++++++++++++ 
2 number of groups accessed in current state 
 added to current state 
3 number of groups accessed in next state 

consultant_Karl automaton name 

 compare Mobil with Shell
 group NOT found 
 search for CIType of group Mobil
 found CIType = Oil
 compare Oil with Oil
 not ok: conflict of interest 
 Chinese Wall Violation !!!!!!!! 
 compare Shell with Shell
 ok: group found +++++++++++++ 
1 number of groups accessed in current state 
 added to current state 
2 number of groups accessed in next state 
 compare Shell with Shell
 ok: group found +++++++++++++ 
2 number of groups accessed in current state 
 added to current state 
3 number of groups accessed in next state 
 compare Mobil with Shell
 compare Mobil with Shell
 compare Mobil with Shell
 group NOT found 
 search for CIType of group Mobil
 found CIType = Oil
 compare Oil with Oil
 not ok: conflict of interest 
 Chinese Wall Violation !!!!!!!! 
done


Question 2:
===========
50 points

Simple role based access control statements
are described below. 
Design a RBAC policy language that can express those
statements and similar ones.
Turn in your class dictionary.

(
users (
  Ruth
  Karl
  )
roles (
  MeetingLeader transactions 
    (cancelMeeting removeAttendant)
  MeetingAttendant transactions (MinutesTaker)
  Clinician transactions 
    (openMedicalRecord getPatientConsent)
  Patient transactions 
    (accessMedicalHistory)
  Patient2 transactions 
    ()
  Patient3 
  )
subjects (
  Ruth current role MeetingLeader
    authorized (MeetingLeader MeetingAttendant)
  John current role Clinician
    authorized ()
  Julie current role MeetingAttendent
  )

users (
  )
roles (
  )
subjects (
  )
)

Question 3:
-----------
40 points

Discuss the advantages and disadvantages 
of AspectJ as a language for implementing 
security policies.



Question 4:
-----------
30 points

Our text book describes Principle 1:
Securing the Weakest Link.

Discuss a weak link in a system you know.
How can you control it?


Question 5:
-----------
Reduction
30 points

Consider the following problem (Non-Emptiness of Set Expressions):
Given is a set-theoretic expression in terms of set variables. 
Is there an assignment of sets to the set variables
so that the expression returns a non-empty set?

A set-theoretic expression has the following
class dictionary:

E : S | C.
S = <variable> Ident. 
C : Unary | Binary.
Unary = "!" E.
Binary = Op <args> List(E).
Op : Intersection | Union.
Intersection = "*".
Union = "+".
List(S) ~ {S}.

A set has the form List(Element), where 
Element = Ident. 

Show that if there is a polynomial algorithm for solving
Non-Emptiness of Set Expressions, then there is a polynomial
algorithm for satisfiability of boolean formulas.
Give the details of the translation in English.