WinAPI CredEnumerate Marshal.PtrToStructure例外

Question

WinAPI関数を使用してVB.NetアプリケーションからWindows資格情報を列挙する際に問題があります。私のコードは以下の通りです。

<DllImport("advapi32.dll", SetLastError:=True, CharSet:=CharSet.Unicode)> 
Private Shared Function CredEnumerate(filter As String, flag As Integer, ByRef count As Integer, ByRef pCredentials As IntPtr) As Boolean 
End Function 

Public Enum CRED_PERSIST As UInteger 
    SESSION = 1 
    LOCAL_MACHINE = 2 
    ENTERPRISE = 3 
End Enum 

Public Enum CRED_TYPE As UInteger 
    GENERIC = 1 
    DOMAIN_PASSWORD = 2 
    DOMAIN_CERTIFICATE = 3 
    DOMAIN_VISIBLE_PASSWORD = 4 
    GENERIC_CERTIFICATE = 5 
    DOMAIN_EXTENDED = 6 
    MAXIMUM = 7 
    ' Maximum supported cred type 
    MAXIMUM_EX = (MAXIMUM + 1000) 
    ' Allow new applications to run on old OSes 
End Enum 

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Auto)> 
Public Structure CREDENTIAL_ATTRIBUTE 
    Private Keyword As String 
    Private Flags As UInteger 
    Private ValueSize As UInteger 
    Private Value As IntPtr 
End Structure 

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)> 
Private Class Credential 
    Public Flags As UInt32 
    Public Type As CRED_TYPE 
    Public TargetName As String 
    Public Comment As String 
    Public LastWritten As ComTypes.FILETIME 
    Public CredentialBlobSize As UInt32 
    Public CredentialBlob As IntPtr 
    Public Persist As CRED_PERSIST 
    Public AttributeCount As UInt32 
    Public Attributes As IntPtr 
    Public TargetAlias As String 
    Public UserName As String 
End Class 


Private Function GetCredentials() As Credential() 
    Dim count As Integer = 0 
    Dim pCredentials As IntPtr = IntPtr.Zero 
    Dim credentials As List(Of Credential) = New List(Of Credential) 
    Dim ret As Boolean = CredEnumerate(Nothing, 0, count, pCredentials) 
    If ret <> False Then 
     Dim p As IntPtr = pCredentials 
     For n As Integer = 0 To count - 1 
      If Marshal.SizeOf(p) = 4 Then 
       p = New IntPtr(p.ToInt32() + n) 
      Else 
       p = New IntPtr(p.ToInt64() + n) 
      End If 
      credentials.Add(Marshal.PtrToStructure(Marshal.ReadIntPtr(p), GetType(Credential))) 
     Next 
    End If 
    Return credentials.ToArray 
End Function 

Marshal.PtrToStructure機能は、任意の有用な情報なしSystem.ExecetionEngineExceptionをスローします。私は間違った資格の構造で疑いましたが、それは私には正しいようです。何が間違っているか分かっているなら、私はあなたの答えを待っています。 ありがとう

編集：@Zagglerのおかげで、ここに私の修正された機能が追加されました。しかし、構造全体が空です。 ここに新しい機能があります。

Private Function GetCredentials() As Credential() 
    Dim count As Integer = 0 
    Dim pCredentials As IntPtr = IntPtr.Zero 
    Dim credentials As List(Of Credential) = New List(Of Credential) 

    Dim ret As Boolean = CredEnumerate(Nothing, 0, count, pCredentials) 
    If ret <> False Then 
     Dim p As IntPtr = pCredentials 
     For n As Integer = 0 To count - 1 
      Dim cred As Credential = New Credential 
      Dim pnt As IntPtr = Marshal.AllocHGlobal(Marshal.SizeOf(cred)) 
      Try 

       If Marshal.SizeOf(p) = 4 Then 
        p = New IntPtr(p.ToInt32() + n) 
       Else 
        p = New IntPtr(p.ToInt64() + n) 
       End If 
       Marshal.StructureToPtr(cred, pnt, False) 
       credentials.Add(Marshal.PtrToStructure(pnt, GetType(Credential))) 

      Finally 
       Marshal.FreeHGlobal(pnt) 
      End Try 
     Next 
    End If 
    Return credentials.ToArray 
End Function 

Answer 1

あなたの最初の試みはよかったです。 AllocHGlobalとFreeHGlobalを使用しないでください。 Winapiはメモリを割り当てています。割り当てられたメモリを解放するためにCredFreeを検索します（構造体を整列した後）。

ポインタ演算に間違いがあります。ポインタサイズを増やす必要があります。

... 
Dim p As IntPtr = pCredentials 
For n As Integer = 0 To count - 1 
    credentials.Add(Marshal.PtrToStructure(Marshal.ReadIntPtr(p), GetType(Credential))) 
    p = p + IntPtr.Size 
Next 
... 

UInt32とUIntegerは同じであり、一貫性を保って選択してください。

Charset.Autoをすべて使用してみてください。動作しない場合は、Charset.Unicodeを試して、CredEnumerateW関数を使用してください。