SemaphoreAccessRule Class

Definition

Namespace:

System.Security.AccessControl

Assembly:

System.Threading.AccessControl.dll

Source:

SemaphoreSecurity.cs

Represents a set of access rights allowed or denied for a user or group. This class cannot be inherited.

public ref class SemaphoreAccessRule sealed : System::Security::AccessControl::AccessRule

public sealed class SemaphoreAccessRule : System.Security.AccessControl.AccessRule

type SemaphoreAccessRule = class
    inherit AccessRule

Public NotInheritable Class SemaphoreAccessRule
Inherits AccessRule

Inheritance

Object

AuthorizationRule

AccessRule

SemaphoreAccessRule

Examples

The following code example demonstrates the separation between Allow rules and Deny rules, and shows the combination of rights in compatible rules. The example creates a SemaphoreSecurity object, adds rules that allow and deny various rights for the current user, and displays the resulting pair of rules. The example then allows new rights for the current user and displays the result, showing that the new rights are merged with the existing Allow rule.

Note

This example does not attach the security object to a Semaphore object. Examples that attach security objects can be found in Semaphore.GetAccessControl and Semaphore.SetAccessControl.

using System;
using System.Threading;
using System.Security.AccessControl;
using System.Security.Principal;

public class Example
{
    public static void Main()
    {
        // Create a string representing the current user.
        string user = Environment.UserDomainName + "\\" + 
            Environment.UserName;

        // Create a security object that grants no access.
        SemaphoreSecurity mSec = new SemaphoreSecurity();

        // Add a rule that grants the current user the 
        // right to enter or release the semaphore.
        SemaphoreAccessRule rule = new SemaphoreAccessRule(user, 
            SemaphoreRights.Synchronize | SemaphoreRights.Modify, 
            AccessControlType.Allow);
        mSec.AddAccessRule(rule);

        // Add a rule that denies the current user the 
        // right to change permissions on the semaphore.
        rule = new SemaphoreAccessRule(user, 
            SemaphoreRights.ChangePermissions, 
            AccessControlType.Deny);
        mSec.AddAccessRule(rule);

        // Display the rules in the security object.
        ShowSecurity(mSec);

        // Add a rule that allows the current user the 
        // right to read permissions on the semaphore. This rule
        // is merged with the existing Allow rule.
        rule = new SemaphoreAccessRule(user, 
            SemaphoreRights.ReadPermissions, 
            AccessControlType.Allow);
        mSec.AddAccessRule(rule);

        ShowSecurity(mSec);
    }

    private static void ShowSecurity(SemaphoreSecurity security)
    {
        Console.WriteLine("\r\nCurrent access rules:\r\n");

        foreach(SemaphoreAccessRule ar in 
            security.GetAccessRules(true, true, typeof(NTAccount)))
        {
            Console.WriteLine("        User: {0}", ar.IdentityReference);
            Console.WriteLine("        Type: {0}", ar.AccessControlType);
            Console.WriteLine("      Rights: {0}", ar.SemaphoreRights);
            Console.WriteLine();
        }
    }
}

/*This code example produces output similar to following:

Current access rules:

        User: TestDomain\TestUser
        Type: Deny
      Rights: ChangePermissions

        User: TestDomain\TestUser
        Type: Allow
      Rights: Modify, Synchronize


Current access rules:

        User: TestDomain\TestUser
        Type: Deny
      Rights: ChangePermissions

        User: TestDomain\TestUser
        Type: Allow
      Rights: Modify, ReadPermissions, Synchronize
 */

Imports System.Threading
Imports System.Security.AccessControl
Imports System.Security.Principal

Public Class Example

    Public Shared Sub Main()

        ' Create a string representing the current user.
        Dim user As String = Environment.UserDomainName _ 
            & "\" & Environment.UserName

        ' Create a security object that grants no access.
        Dim mSec As New SemaphoreSecurity()

        ' Add a rule that grants the current user the 
        ' right to enter or release the semaphore.
        Dim rule As New SemaphoreAccessRule(user, _
            SemaphoreRights.Synchronize _
            Or SemaphoreRights.Modify, _
            AccessControlType.Allow)
        mSec.AddAccessRule(rule)

        ' Add a rule that denies the current user the 
        ' right to change permissions on the semaphore.
        rule = New SemaphoreAccessRule(user, _
            SemaphoreRights.ChangePermissions, _
            AccessControlType.Deny)
        mSec.AddAccessRule(rule)

        ' Display the rules in the security object.
        ShowSecurity(mSec)

        ' Add a rule that allows the current user the 
        ' right to read permissions on the semaphore. This 
        ' rule is merged with the existing Allow rule.
        rule = New SemaphoreAccessRule(user, _
            SemaphoreRights.ReadPermissions, _
            AccessControlType.Allow)
        mSec.AddAccessRule(rule)

        ShowSecurity(mSec)

    End Sub 

    Private Shared Sub ShowSecurity(ByVal security As SemaphoreSecurity)
        Console.WriteLine(vbCrLf & "Current access rules:" & vbCrLf)

        For Each ar As SemaphoreAccessRule In _
            security.GetAccessRules(True, True, GetType(NTAccount))

            Console.WriteLine("        User: {0}", ar.IdentityReference)
            Console.WriteLine("        Type: {0}", ar.AccessControlType)
            Console.WriteLine("      Rights: {0}", ar.SemaphoreRights)
            Console.WriteLine()
        Next

    End Sub
End Class 

'This code example produces output similar to following:
'
'Current access rules:
'
'        User: TestDomain\TestUser
'        Type: Deny
'      Rights: ChangePermissions
'
'        User: TestDomain\TestUser
'        Type: Allow
'      Rights: Modify, Synchronize
'
'
'Current access rules:
'
'        User: TestDomain\TestUser
'        Type: Deny
'      Rights: ChangePermissions
'
'        User: TestDomain\TestUser
'        Type: Allow
'      Rights: Modify, ReadPermissions, Synchronize

Remarks

The SemaphoreAccessRule class is one of a set of classes that the .NET Framework provides for managing Windows access control security on named system semaphores. For an overview of these classes, and their relationship to the underlying Windows access control structures, see SemaphoreSecurity.

Note

Windows access control security is meaningful only for named system semaphores. If a Semaphore object represents a local semaphore, access control is irrelevant.

To get a list of the rules currently applied to a named semaphore, use the Semaphore.GetAccessControl method to get a SemaphoreSecurity object, then use its GetAccessRules method to obtain a collection of SemaphoreAccessRule objects.

SemaphoreAccessRule objects do not map one-to-one with access control entries in the underlying discretionary access control list (DACL). When you get the set of all access rules for a semaphore, the set contains the minimum number of rules currently required to express all the access control entries.

Note

The underlying access control entries change as you apply and remove rules. The information in rules is merged if possible, to maintain the smallest number of access control entries. Thus, when you read the current list of rules, it might not look exactly like the list of all the rules you have added.

Use SemaphoreAccessRule objects to specify access rights to allow or deny to a user or group. A SemaphoreAccessRule object always represents either allowed access or denied access, never both.

To apply a rule to a named system semaphore, use the Semaphore.GetAccessControl method to get the SemaphoreSecurity object. Modify the SemaphoreSecurity object by using its methods to add the rule, and then use the Semaphore.SetAccessControl method to reattach the security object.

Important

Changes you make to a SemaphoreSecurity object do not affect the access levels of the named semaphore until you call the Semaphore.SetAccessControl method to assign the altered security object to the named semaphore.

SemaphoreAccessRule objects are immutable. Security for a semaphore is modified using the methods of the SemaphoreSecurity class to add or remove rules; as you do this, the underlying access control entries are modified.

Constructors

SemaphoreAccessRule(IdentityReference, SemaphoreRights, AccessControlType)	Initializes a new instance of the SemaphoreAccessRule class, specifying the user or group the rule applies to, the access rights, and whether the specified access rights are allowed or denied.
SemaphoreAccessRule(String, SemaphoreRights, AccessControlType)	Initializes a new instance of the SemaphoreAccessRule class, specifying the name of the user or group the rule applies to, the access rights, and whether the specified access rights are allowed or denied.

Properties

AccessControlType	Gets the AccessControlType value associated with this AccessRule object. (Inherited from AccessRule)
AccessMask	Gets the access mask for this rule. (Inherited from AuthorizationRule)
IdentityReference	Gets the IdentityReference to which this rule applies. (Inherited from AuthorizationRule)
InheritanceFlags	Gets the value of flags that determine how this rule is inherited by child objects. (Inherited from AuthorizationRule)
IsInherited	Gets a value indicating whether this rule is explicitly set or is inherited from a parent container object. (Inherited from AuthorizationRule)
PropagationFlags	Gets the value of the propagation flags, which determine how inheritance of this rule is propagated to child objects. This property is significant only when the value of the InheritanceFlags enumeration is not None. (Inherited from AuthorizationRule)
SemaphoreRights	Gets the rights allowed or denied by the access rule.

Methods

Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)

See also

• SemaphoreSecurity