ICertificatePolicy Interface


Validates a server certificate.

Namespace:   System.Net
Assembly:  System (in System.dll)

Public Interface ICertificatePolicy

The ICertificatePolicy interface is used to provide custom security certificate validation for an application. The default policy is to allow valid certificates, as well as valid certificates that have expired. To change this policy, implement the ICertificatePolicy interface with a different policy, and then assign that policy to ServicePointManager.CertificatePolicy.

ICertificatePolicy uses the Security Support Provider Interface (SSPI). For more information, see the SSPI documentation on MSDN.

The following example creates a certificate policy that returns false for any certificate problem and prints a message that indicates the problem on the console. The CertificateProblem enum defines SSPI constants for certificate problems, and the private GetProblemMessage method creates a printable message about the problem.

Public Enum CertificateProblem As Long
    CertEXPIRED                   = 2148204801    ' 0x800B0101
    CertVALIDITYPERIODNESTING     = 2148204802    ' 0x800B0102
    CertROLE                      = 2148204803    ' 0x800B0103
    CertPATHLENCONST              = 2148204804    ' 0x800B0104
    CertCRITICAL                  = 2148204805    ' 0x800B0105
    CertPURPOSE                   = 2148204806    ' 0x800B0106
    CertISSUERCHAINING            = 2148204807    ' 0x800B0107
    CertMALFORMED                 = 2148204808    ' 0x800B0108
    CertUNTRUSTEDROOT             = 2148204809    ' 0x800B0109
    CertCHAINING                  = 2148204810    ' 0x800B010A
    CertREVOKED                   = 2148204812    ' 0x800B010C
    CertUNTRUSTEDTESTROOT         = 2148204813    ' 0x800B010D       
    CertREVOCATION_FAILURE        = 2148204814    ' 0x800B010E
    CertCN_NO_MATCH               = 2148204815    ' 0x800B010F
    CertWRONG_USAGE               = 2148204816    ' 0x800B0110
    CertUNTRUSTEDCA               = 2148204818     ' 0x800B0112
End Enum

Public Class MyCertificateValidation
    Implements ICertificatePolicy

    ' Default policy for certificate validation.
    Public Shared DefaultValidate As Boolean = False    

    Public Function CheckValidationResult(srvPoint As ServicePoint, _
       cert As X509Certificate, request As WebRequest, problem As Integer) _
       As Boolean Implements ICertificatePolicy.CheckValidationResult

        Dim ValidationResult As Boolean = False
        Console.WriteLine(("Certificate Problem with accessing " & _
        Console.Write("Problem code 0x{0:X8},", CInt(problem))
        Console.WriteLine(GetProblemMessage(CType(problem, _

        ValidationResult = DefaultValidate
        Return ValidationResult
    End Function    

    Private Function GetProblemMessage(Problem As CertificateProblem) As String
        Dim ProblemMessage As String = ""
        Dim problemList As New CertificateProblem()
        Dim ProblemCodeName As String = System.Enum.GetName( _
           problemList.GetType(), Problem)
        If Not (ProblemCodeName Is Nothing) Then
            ProblemMessage = ProblemMessage + "-Certificateproblem:" & _
            ProblemMessage = "Unknown Certificate Problem"
        End If
        Return ProblemMessage
    End Function
End Class

.NET Framework
Available since 1.1
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