X509Extension Class
Represents an X509 extension.
System.Security.Cryptography::AsnEncodedData
System.Security.Cryptography.X509Certificates::X509Extension
System.Security.Cryptography.X509Certificates::X509BasicConstraintsExtension
System.Security.Cryptography.X509Certificates::X509EnhancedKeyUsageExtension
System.Security.Cryptography.X509Certificates::X509KeyUsageExtension
System.Security.Cryptography.X509Certificates::X509SubjectKeyIdentifierExtension
Assembly: System (in System.dll)
The X509Extension type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | X509Extension() | Initializes a new instance of the X509Extension class. |
![]() | X509Extension(AsnEncodedData, Boolean) | Initializes a new instance of the X509Extension class. |
![]() | X509Extension(Oid, array<Byte>, Boolean) | Initializes a new instance of the X509Extension class. |
![]() | X509Extension(String, array<Byte>, Boolean) | Initializes a new instance of the X509Extension class. |
| Name | Description | |
|---|---|---|
![]() | 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.) |
| Name | Description | |
|---|---|---|
![]() | CopyFrom | Copies the extension properties of the specified AsnEncodedData object. (Overrides AsnEncodedData::CopyFrom(AsnEncodedData).) |
![]() | Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() | Format | Returns a formatted version of the Abstract Syntax Notation One (ASN.1)-encoded data as a string. (Inherited from AsnEncodedData.) |
![]() | GetHashCode | Serves as a hash function for a particular type. (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.) |
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.
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." ); } }
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
