X509Extension Class
Definition
Important
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Represents an X509 extension.
public ref class X509Extension : System::Security::Cryptography::AsnEncodedDatapublic class X509Extension : System.Security.Cryptography.AsnEncodedDatatype X509Extension = class
inherit AsnEncodedDataPublic Class X509Extension
Inherits AsnEncodedData- Inheritance
- Derived
Examples
The following code example demonstrates using the X509Extension class.
#using <System.dll>
#using <system.security.dll>
using namespace System;
using namespace System::Security::Cryptography;
using namespace System::Security::Cryptography::X509Certificates;
int main()
{
try
{
X509Store^ store = gcnew X509Store( L"MY",StoreLocation::CurrentUser );
store->Open( static_cast<OpenFlags>(OpenFlags::ReadOnly | OpenFlags::OpenExistingOnly) );
X509Certificate2Collection^ collection = dynamic_cast<X509Certificate2Collection^>(store->Certificates);
for ( int i = 0; i < collection->Count; i++ )
{
System::Collections::IEnumerator^ myEnum = collection[ i ]->Extensions->GetEnumerator();
while ( myEnum->MoveNext() )
{
X509Extension^ extension = safe_cast<X509Extension^>(myEnum->Current);
Console::WriteLine( L"{0}({1})", extension->Oid->FriendlyName, extension->Oid->Value );
if ( extension->Oid->FriendlyName == L"Key Usage" )
{
X509KeyUsageExtension^ ext = dynamic_cast<X509KeyUsageExtension^>(extension);
Console::WriteLine( ext->KeyUsages );
}
if ( extension->Oid->FriendlyName == L"Basic Constraints" )
{
X509BasicConstraintsExtension^ ext = dynamic_cast<X509BasicConstraintsExtension^>(extension);
Console::WriteLine( ext->CertificateAuthority );
Console::WriteLine( ext->HasPathLengthConstraint );
Console::WriteLine( ext->PathLengthConstraint );
}
if ( extension->Oid->FriendlyName == L"Subject Key Identifier" )
{
X509SubjectKeyIdentifierExtension^ ext = dynamic_cast<X509SubjectKeyIdentifierExtension^>(extension);
Console::WriteLine( ext->SubjectKeyIdentifier );
}
if ( extension->Oid->FriendlyName == L"Enhanced Key Usage" )
{
X509EnhancedKeyUsageExtension^ ext = dynamic_cast<X509EnhancedKeyUsageExtension^>(extension);
OidCollection^ oids = ext->EnhancedKeyUsages;
System::Collections::IEnumerator^ myEnum1 = oids->GetEnumerator();
while ( myEnum1->MoveNext() )
{
Oid^ oid = safe_cast<Oid^>(myEnum1->Current);
Console::WriteLine( L"{0}({1})", oid->FriendlyName, oid->Value );
}
}
}
}
store->Close();
}
catch ( CryptographicException^ )
{
Console::WriteLine( L"Information could not be written out for this certificate." );
}
}
using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
public class CertSelect
{
public static void Main()
{
try
{
X509Store store = new X509Store("MY", StoreLocation.CurrentUser);
store.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);
X509Certificate2Collection collection = (X509Certificate2Collection)store.Certificates;
for (int i = 0; i < collection.Count; i++)
{
foreach (X509Extension extension in collection[i].Extensions)
{
Console.WriteLine(extension.Oid.FriendlyName + "(" + extension.Oid.Value + ")");
if (extension.Oid.FriendlyName == "Key Usage")
{
X509KeyUsageExtension ext = (X509KeyUsageExtension)extension;
Console.WriteLine(ext.KeyUsages);
}
if (extension.Oid.FriendlyName == "Basic Constraints")
{
X509BasicConstraintsExtension ext = (X509BasicConstraintsExtension)extension;
Console.WriteLine(ext.CertificateAuthority);
Console.WriteLine(ext.HasPathLengthConstraint);
Console.WriteLine(ext.PathLengthConstraint);
}
if (extension.Oid.FriendlyName == "Subject Key Identifier")
{
X509SubjectKeyIdentifierExtension ext = (X509SubjectKeyIdentifierExtension)extension;
Console.WriteLine(ext.SubjectKeyIdentifier);
}
if (extension.Oid.FriendlyName == "Enhanced Key Usage")
{
X509EnhancedKeyUsageExtension ext = (X509EnhancedKeyUsageExtension)extension;
OidCollection oids = ext.EnhancedKeyUsages;
foreach (Oid oid in oids)
{
Console.WriteLine(oid.FriendlyName + "(" + oid.Value + ")");
}
}
}
}
store.Close();
}
catch (CryptographicException)
{
Console.WriteLine("Information could not be written out for this certificate.");
}
}
}
Imports System.Security.Cryptography
Imports System.Security.Cryptography.X509Certificates
Module CertSelect
Sub Main()
Try
Dim store As New X509Store("MY", StoreLocation.CurrentUser)
store.Open(OpenFlags.ReadOnly Or OpenFlags.OpenExistingOnly)
Dim collection As X509Certificate2Collection = CType(store.Certificates, X509Certificate2Collection)
For i As Integer = 0 To collection.Count - 1
Dim extension As X509Extension
For Each extension In collection(i).Extensions
Console.WriteLine(extension.Oid.FriendlyName + "(" + extension.Oid.Value + ")")
If extension.Oid.FriendlyName = "Key Usage" Then
Dim ext As X509KeyUsageExtension = CType(extension, X509KeyUsageExtension)
Console.WriteLine(ext.KeyUsages)
End If
If extension.Oid.FriendlyName = "Basic Constraints" Then
Dim ext As X509BasicConstraintsExtension = CType(extension, X509BasicConstraintsExtension)
Console.WriteLine(ext.CertificateAuthority)
Console.WriteLine(ext.HasPathLengthConstraint)
Console.WriteLine(ext.PathLengthConstraint)
End If
If extension.Oid.FriendlyName = "Subject Key Identifier" Then
Dim ext As X509SubjectKeyIdentifierExtension = CType(extension, X509SubjectKeyIdentifierExtension)
Console.WriteLine(ext.SubjectKeyIdentifier)
End If
If extension.Oid.FriendlyName = "Enhanced Key Usage" Then
Dim ext As X509EnhancedKeyUsageExtension = CType(extension, X509EnhancedKeyUsageExtension)
Dim oids As OidCollection = ext.EnhancedKeyUsages
Dim oid As Oid
For Each oid In oids
Console.WriteLine(oid.FriendlyName + "(" + oid.Value + ")")
Next oid
End If
Next extension
Next i
store.Close()
Catch
Console.WriteLine("Information could not be written out for this certificate.")
End Try
End Sub
End Module
Remarks
X509 extensions are dynamic, extended properties that can be added to an X509 certificate and changed. The X509Extension class can be used to create extensions that are associated with a certificate but are not part of a certificate as issued by a certification authority (CA).
In its most basic form, an X509 extension has an object identifier (OID), a Boolean value describing whether the extension is considered critical or not, and ASN-encoded data. Custom extensions can be registered in a CryptoConfig file.
The.NET Framework includes implementations of several common X509 extensions:
X509KeyUsageExtension. Describes the key usages of a certificate.
X509BasicConstraintsExtension. Describes the constraints for a certificate.
X509EnhancedKeyUsageExtension. Describes the enhanced key usages of a certificate.
X509SubjectKeyIdentifierExtension. Describes the key identifier. For example, used with XMLDSIG.
Constructors
| X509Extension() |
Initializes a new instance of the X509Extension class. |
| X509Extension(AsnEncodedData, Boolean) |
Initializes a new instance of the X509Extension class. |
| X509Extension(Oid, Byte[], Boolean) |
Initializes a new instance of the X509Extension class. |
| X509Extension(Oid, ReadOnlySpan<Byte>, Boolean) |
Initializes a new instance of the X509Extension class. |
| X509Extension(String, Byte[], Boolean) |
Initializes a new instance of the X509Extension class. |
| X509Extension(String, ReadOnlySpan<Byte>, Boolean) |
Initializes a new instance of the X509Extension class. |
Properties
| Critical |
Gets a Boolean value indicating whether the extension is critical. |
| Oid |
Gets or sets the Oid value for an AsnEncodedData object. (Inherited from AsnEncodedData) |
| RawData |
Gets or sets the Abstract Syntax Notation One (ASN.1)-encoded data represented in a byte array. (Inherited from AsnEncodedData) |
Methods
| CopyFrom(AsnEncodedData) |
Copies the extension properties of the specified AsnEncodedData object. |
| Equals(Object) |
Determines whether the specified object is equal to the current object. (Inherited from Object) |
| Format(Boolean) |
Returns a formatted version of the Abstract Syntax Notation One (ASN.1)-encoded data as a string. (Inherited from AsnEncodedData) |
| 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) |
