Accessing a hash API

[TheCite]

I am trying to make a function to hash passwords with. Here is the
code:
Option Compare Database
Option Explicit

'function declarations
Private Declare Function CryptAcquireContext Lib "advapi32.dll" Alias
"CryptAcquireContextA" (ByRef phProv As Long, ByVal pszContainer As
Any, ByVal pszProvider As Any, ByVal dwProvType As Long, ByVal dwFlags
As Long) As Long
Private Declare Function CryptCreateHash Lib "advapi32.dll" (ByVal
hProv As Long, ByVal Algid As Long, ByVal mhSessionKey As Long, ByVal
dwFlags As Long, ByRef phHash As Long) As Long
Private Declare Function CryptHashData Lib "advapi32.dll" (ByVal hHash
As Long, ByVal pbData As String, 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, ByRef pbData As Any, ByVal
dwDataLen As Long, ByVal dwFlags As Long) As Long
Private Declare Function CryptDestroyHash Lib "advapi32.dll" (ByVal
hHash As Long) As Long
Private Declare Function CryptReleaseContext Lib "advapi32.dll" (ByVal
hProv As Long, ByVal dwFlags As Long) As Long

'hash type constants
Const PROV_RSA_FULL As Long = 1
Const CALG_MD5 As Long = 32771 'ALG_CLASS_HASH Or ALG_TYPE_ANY Or
ALG_SID_MD5
Const ALG_CLASS_HASH As Long = 32768
Const ALG_TYPE_ANY As Long = 0
Const ALG_SID_MD5 As Long = 3

'parameter retrieval types
Const HP_HASHVAL As Long = 2
Const HP_HASHSIZE As Long = 4

'errors
Const ERROR_INVALID_HANDLE As Long = 6
Const ERROR_INVALID_PARAMETER As Long = 87
Const ERROR_MORE_DATA As Long = 234
Const NTE_BAD_FLAGS As Long = &H80090009
Const NTE_BAD_TYPE As Long = &H8009000A
Const NTE_BAD_UID As Long = &H80090001
Const NTE_BAD_HASH As Long = &H80090002

Function Hash(strIn As String) As String

Dim hCryptProv As Long
Dim hHash As Long
Dim dwHashLength As Long
Dim pbHashedData As String

If CryptAcquireContext(hCryptProv, 0&, 0&, PROV_RSA_FULL, 0) = 0
Then GoTo ExitHash 'get a context for hashes
If CryptCreateHash(hCryptProv, CALG_MD5, 0, 0, hHash) = 0 Then
GoTo ExitHash 'create an empty hash
If CryptHashData(hHash, strIn, Len(strIn) + 1, 0) = 0 Then GoTo
ExitHash 'put the password into the hash

dwHashLength = 0
If CryptGetHashParam(hHash, HP_HASHSIZE, 0&, dwHashLength, 0) = 0
Then GoTo ExitHash 'retrieve the length
pbHashedData = String$(dwHashLength, vbNullChar) 'make a string
filled w/ null chars

If CryptGetHashParam(hHash, HP_HASHVAL, pbHashedData,
dwHashLength, 0) = 0 Then GoTo ExitHash 'retrieve the hashed value

ExitHash:
If hHash Then CryptDestroyHash hHash
If hCryptProv Then CryptReleaseContext hCryptProv, 0

End Function
Anyhow, when I try to get the hashed value's length, the function
returns false, indicating an error. I checked the Err.LastDllError in
the debug window, and I got 87 (ERROR_INVALID_PARAMETER). Can someone
tell me what I did wrong?

[CDMAPoster]

On Jul 25, 5:40 pm, TheCite <[e-mail]:

I am trying to make a function to hash passwords with. Here is the
code:
Option Compare Database
Option Explicit

'function declarations
Private Declare Function CryptAcquireContext Lib "advapi32.dll" Alias
"CryptAcquireContextA" (ByRef phProv As Long, ByVal pszContainer As
Any, ByVal pszProvider As Any, ByVal dwProvType As Long, ByVal dwFlags
As Long) As Long
Private Declare Function CryptCreateHash Lib "advapi32.dll" (ByVal
hProv As Long, ByVal Algid As Long, ByVal mhSessionKey As Long, ByVal
dwFlags As Long, ByRef phHash As Long) As Long
Private Declare Function CryptHashData Lib "advapi32.dll" (ByVal hHash
As Long, ByVal pbData As String, 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, ByRef pbData As Any, ByVal
dwDataLen As Long, ByVal dwFlags As Long) As Long
Private Declare Function CryptDestroyHash Lib "advapi32.dll" (ByVal
hHash As Long) As Long
Private Declare Function CryptReleaseContext Lib "advapi32.dll" (ByVal
hProv As Long, ByVal dwFlags As Long) As Long

'hash type constants
Const PROV_RSA_FULL As Long = 1
Const CALG_MD5 As Long = 32771 'ALG_CLASS_HASH Or ALG_TYPE_ANY Or
ALG_SID_MD5
Const ALG_CLASS_HASH As Long = 32768
Const ALG_TYPE_ANY As Long = 0
Const ALG_SID_MD5 As Long = 3

'parameter retrieval types
Const HP_HASHVAL As Long = 2
Const HP_HASHSIZE As Long = 4

'errors
Const ERROR_INVALID_HANDLE As Long = 6
Const ERROR_INVALID_PARAMETER As Long = 87
Const ERROR_MORE_DATA As Long = 234
Const NTE_BAD_FLAGS As Long = &H80090009
Const NTE_BAD_TYPE As Long = &H8009000A
Const NTE_BAD_UID As Long = &H80090001
Const NTE_BAD_HASH As Long = &H80090002

Function Hash(strIn As String) As String

Dim hCryptProv As Long
Dim hHash As Long
Dim dwHashLength As Long
Dim pbHashedData As String

If CryptAcquireContext(hCryptProv, 0&, 0&, PROV_RSA_FULL, 0) = 0
Then GoTo ExitHash 'get a context for hashes
If CryptCreateHash(hCryptProv, CALG_MD5, 0, 0, hHash) = 0 Then
GoTo ExitHash 'create an empty hash
If CryptHashData(hHash, strIn, Len(strIn) + 1, 0) = 0 Then GoTo
ExitHash 'put the password into the hash

dwHashLength = 0
If CryptGetHashParam(hHash, HP_HASHSIZE, 0&, dwHashLength, 0) = 0
Then GoTo ExitHash 'retrieve the length
pbHashedData = String$(dwHashLength, vbNullChar) 'make a string
filled w/ null chars

If CryptGetHashParam(hHash, HP_HASHVAL, pbHashedData,
dwHashLength, 0) = 0 Then GoTo ExitHash 'retrieve the hashed value

ExitHash:
If hHash Then CryptDestroyHash hHash
If hCryptProv Then CryptReleaseContext hCryptProv, 0

End Function
Anyhow, when I try to get the hashed value's length, the function
returns false, indicating an error. I checked the Err.LastDllError in
the debug window, and I got 87 (ERROR_INVALID_PARAMETER). Can someone
tell me what I did wrong?

This newsgroup is for questions about the Access database program sold
by Microsoft. Anyway,

In CryptGetHashParam you should use ByRef instead of ByVal here:

ByRef dwDataLen As Long

because CryptGetHashParam needs to retrieve this value when pdwDataLen
(dwHashLength) is too small. ByVal forces the 0 value to remain
static.

Note: Be sure to check out the entry for CryptGetHashParam in the
Win32 SDK Reference Help.

James A. Fortune
CD********@FortuneJames.com