CryptGetHashParam
Mit der Funktion CryptGetHashParam lassen sich Eigenschaften eines Hash Objektes, nämlich der verwendete Algorithmus, Die Länge des erstellten Hashes, und der Hash Wert selbst ermitteln.
<<syntaxhighlight lang="vb">>Declare Function CryptGetHashParam Lib "advapi32.dll" ( _
ByVal hHash As Long, _ ByVal dwParam As Long, _ ByVal pbData As Long, _ ByRef pdwDataLen As Long, _ ByVal dwFlags As Long) As Long</<syntaxhighlight lang="vb">>
Parameter
hHash
- [in] Handle eines mit CryptCreateHash erstellten Hash Objekts.
dwParam
- [in] In diesem Parameter wird die Eigenschaft, die ausgelesen werden soll angegeben:
- HP_ALGID verwendeter Algorithmus
- HP_HASHSIZE Grösse des Hashwertes in Bytes
- HP_HASHVAL Hashwert
pbData
- [out] In diesem Buffer wird der jeweilige Eigenschaftswert zurückgegeben. Der Buffer muss vor dem Aufruf reserviert werden. Um die benötigte Grösse des Buffers zu ermitteln kann für diesen Parameter NULL übergeben werden, pdwDataLen erhält dann die Anzahl der benötigten Bytes.
pdwDataLen
- [in,out] Grösse des in pbData bereitgestellten Buffers in Bytes, nach der Rückkehr enthält diese Variable die tasächlich zurückgegebenen Bytes.
dwFlags
- [in] derzeit nicht verwendet, muss 0 sein.
Rückgabe(n)
Bei Erfolg wird ein Wert ungleich 0 zurückgegeben.
Beispiel
<<syntaxhighlight lang="vb">>Option Explicit
Private Declare Function CryptAcquireContext Lib "advapi32.dll" _
Alias "CryptAcquireContextA" ( _ ByRef phProv As Long, _ ByRef pszContainer As Any, _ ByVal pszProvider As String, _ ByVal dwProvType As Long, _ ByVal dwFlags As Long) As Long
Private Declare Function CryptReleaseContext Lib "advapi32.dll" ( _
ByVal hProv As Long, _ ByVal dwFlags As Long) As Long
Private Declare Function CryptCreateHash Lib "advapi32.dll" ( _
ByVal hProv As Long, _ ByVal AlgID As Long, _ ByVal hKey As Long, _ ByVal dwFlags As Long, _ ByRef phHash As Long) As Long
Private Declare Function CryptDestroyHash Lib "advapi32.dll" ( _
ByVal hHash As Long) As Long
Private Declare Function CryptHashData Lib "advapi32.dll" ( _
ByVal hHash As Long, _ ByVal pbData As Long, _ ByVal dwDataLen As Long, _ ByVal dwFlags As Long) As Long
Private Declare Function CryptGetHashParam Lib "advapi32.dll" ( _
ByVal hHash As Long, _ ByVal dwParam As Long, _ ByVal pbData As Long, _ ByRef pdwDataLen As Long, _ ByVal dwFlags As Long) As Long
Private Const MS_DEF_PROV As String = _
"Microsoft Base Cryptographic Provider v1.0"
Private Const PROV_RSA_FULL As Long = 1 Private Const CRYPT_VERIFYCONTEXT As Long = &HF0000000
Private Const HP_HASHVAL As Long = 2 Private Const HP_HASHSIZE As Long = 4
Const ALG_CLASS_KEY_EXCHANGE As Long = &HA000& Const ALG_CLASS_HASH As Long = &H8000& Const ALG_CLASS_DATA_ENCRYPT As Long = &H6000& Const ALG_CLASS_SIGNATURE As Long = &H2000& Const ALG_TYPE_STREAM As Long = &H800& Const ALG_TYPE_BLOCK As Long = &H600& Const ALG_TYPE_RSA As Long = &H400& Const ALG_TYPE_ANY As Long = 0 Const ALG_SID_RSA_ANY As Long = 0 Const ALG_SID_MD2 As Long = 1 Const ALG_SID_MD4 As Long = 2 Const ALG_SID_MD5 As Long = 3 Const ALG_SID_SHA As Long = 4 Const ALG_SID_SHA_256 As Long = 12 Const ALG_SID_SHA_384 As Long = 13 Const ALG_SID_SHA_512 As Long = 14 Const ALG_SID_RC4 As Long = 1 Const ALG_SID_DES As Long = 1 Const ALG_SID_RC2 As Long = 2 Const ALG_SID_3DES As Long = 3 Const ALG_SID_3DES_112 As Long = 9 Const ALG_SID_AES_128 As Long = 14 Const ALG_SID_AES_192 As Long = 15 Const ALG_SID_AES_256 As Long = 16 Const ALG_SID_AES As Long = 17
'Hash Algorithmen: Enum EnmHashAlgo
CALG_MD2 = (ALG_CLASS_HASH Or ALG_TYPE_ANY Or ALG_SID_MD2) CALG_MD4 = (ALG_CLASS_HASH Or ALG_TYPE_ANY Or ALG_SID_MD4) CALG_MD5 = (ALG_CLASS_HASH Or ALG_TYPE_ANY Or ALG_SID_MD5) CALG_SHA = (ALG_CLASS_HASH Or ALG_TYPE_ANY Or ALG_SID_SHA) CALG_SHA256 = (ALG_CLASS_HASH Or ALG_TYPE_ANY Or ALG_SID_SHA_256) CALG_SHA384 = (ALG_CLASS_HASH Or ALG_TYPE_ANY Or ALG_SID_SHA_384) CALG_SHA512 = (ALG_CLASS_HASH Or ALG_TYPE_ANY Or ALG_SID_SHA_512)
End Enum
Private Sub Command1_Click()
Dim sTestString As String Dim btData() As Byte Dim hCryptProv As Long Dim hHash As Long Dim cbHash As Long Dim x As Long Dim sHash As String sTestString = "Hello World!" 'in ANSI Bytefolge umwandeln: btData = StrConv(sTestString, <syntaxhighlight lang="vb">FromUnicode) 'Provider Kontext anfordern: If CryptAcquireContext(hCryptProv, ByVal 0, MS_DEF_PROV, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT) = 0 Then MsgBox "Kann MS Base Provider nicht finden!", <syntaxhighlight lang="vb">Exclamation, "Fehler:" 'Hash Objekt erstellen: ElseIf CryptCreateHash(hCryptProv, CALG_SHA, 0, 0, hHash) = 0 Then MsgBox "Kann Hash Objekt nicht erstellen!", <syntaxhighlight lang="vb">Exclamation, "Fehler:" 'daten ins Hash Objekt schreiben: ElseIf CryptHashData(hHash, VarPtr(btData(0)), UBound(btData) + 1, 0) = 0 Then MsgBox "Kann Daten nicht in Hash schreiben!", <syntaxhighlight lang="vb">Exclamation, "Fehler:" 'Grösse des Hashwertes ermitteln: ElseIf CryptGetHashParam(hHash, HP_HASHVAL, 0, cbHash, 0) = 0 Then MsgBox "Kann Daten nicht aus Hash auslesen!", <syntaxhighlight lang="vb">Exclamation, "Fehler:" Else 'Speicherreservieren und Hash abholen: ReDim btData(cbHash - 1) If CryptGetHashParam(hHash, HP_HASHVAL, VarPtr(btData(0)), cbHash, 0) = 0 Then MsgBox "Kann Daten nicht aus Hash auslesen!", <syntaxhighlight lang="vb">Exclamation, "Fehler:" Else 'Der Hash liegt nun in Byteform vor und wird nun in leserliche HEX Darstellung gebracht: For x = 0 To cbHash - 1 sHash = sHash & Right("0" & Hex(btData(x)), 2) Next MsgBox "Hash von " & sTestString & " ist: " & sHash, <syntaxhighlight lang="vb">Information, "Erfolgreich:" End If End If
If hHash <> 0 Then CryptDestroyHash hHash If hCryptProv <> 0 Then CryptReleaseContext hCryptProv, 0
End Sub</<syntaxhighlight lang="vb">>