Please Please help with this API : CertFindCertificateInStore

[dimsumZ]

can somebody please help me with the "CertFindCertificateInStore" API? I want to use it in VB but I can only find C samples in MSDN. THANKS VERY MUCH!

[dimsumZ]

any body please?

[Merrion]

C declaration:

WINCRYPT32API
PCCERT_CONTEXT
WINAPI
CertFindCertificateInStore(
    IN HCERTSTORE hCertStore,
    IN DWORD dwCertEncodingType,
    IN DWORD dwFindFlags,
    IN DWORD dwFindType,
    IN const void *pvFindPara,
    IN PCCERT_CONTEXT pPrevCertContext
    );

which is documented on this MSDN page and is exported by Crypt32.lib...

Therefore in VB this would be:

Private Type CERT_CONTEXT 
    dwCertEncodingType As Long
    pbCertEncoded As Long '<-Pointer to byte...
    cbCertEncoded As Long
    pCertInfo As Long '<--Pointer to CERT_INFO  
    hCertStore As Long
End Type
 
Private Declare Function CertFindCertificateInStore Lib "Crypt32.dll" ( ByVal hCertStore As Long , _
                            ByVal dwCertEncodingType As Long, _ 
                            ByVal dwFindFlags As Long, _ 
                            ByVal dwFindType As Long, _ 
                            ByVal pvFindPara As Long, 
                            pPrevCertContext As CERT_CONTEXT ) As Long 
 
Private Declare Function CertFindCertificateInStoreByLong Lib "Crypt32.dll" _ 
Alias "CertFindCertificateInStore "( ByVal hCertStore As Long , _
                            ByVal dwCertEncodingType As Long, _ 
                            ByVal dwFindFlags As Long, _ 
                            ByVal dwFindType As Long, _ 
                            ByVal pvFindPara As Long, 
                            ByVal pPrevCertContext As Long ) As Long

Hope this helps...
Duncan

[dimsumZ]

Let me try try , thanks Merrion

[dimsumZ]

I have finished the following types declarations :

' Converted from c structs

Type CRYPT_INTEGER_BLOB
    cbData As Long
    pbData() As Byte
End Type

Type CERT_NAME_BLOB
    cbData As Long
    pbData() As Byte
End Type

Type CRYPT_OBJID_BLOB
    cbData As Long
    pbData() As Byte
End Type

Type CRYPT_BIT_BLOB
    cbData As Long
    pbData() As Byte
    cUnusedBits As Long
End Type

Type CERT_EXTENSION
    pszObjId As String
    fCritical As Boolean
    Value As CRYPT_OBJID_BLOB
End Type

Type CRYPT_ALGORITHM_IDENTIFIER
    pszObjId As String
    Parameters As CRYPT_OBJID_BLOB
End Type

Type CERT_PUBLIC_KEY_INFO
    Algorithm As CRYPT_ALGORITHM_IDENTIFIER
    PublicKey As CRYPT_BIT_BLOB
End Type

Type CERT_INFO
    dwVersion As Long
    SerialNumber As CRYPT_INTEGER_BLOB
    SignatureAlgorithm As CRYPT_ALGORITHM_IDENTIFIER
    Issuer As CERT_NAME_BLOB
    NotBefore As Date
    NotAfter As Date
    Subject As CERT_NAME_BLOB
    SubjectPublicKeyInfo As CERT_PUBLIC_KEY_INFO
    IssuerUniqueId As CRYPT_BIT_BLOB
    SubjectUniqueId As CRYPT_BIT_BLOB
    cExtension As Long
    rgExtension As CERT_EXTENSION
End Type

Public Type CERT_CONTEXT
    dwCertEncodingType As Long
    pbCertEncoded As Byte
    cbCertEncoded As Long
    pCertInfo As CERT_INFO
    hCertStore As Long
End Type

It will be better if i can find C type mapping to Visual Basics...

[dimsumZ]

My target is find user's cert to use private to encrypt data, by now i only can do 2 steps :

1. Get CSP context
2. Get System Store handler
3. (stucked) Find certificate in store

Code as follows :

private sub Form_Load()

' Get CSP context
Dim context_Handler As Long
CryptAcquireContext context_Handler, "administrator", _
"Microsoft Base Cryptographic Provider v1.0", 1, 0

' Get System Store handler, can use MY or CA or ROOT or SPC
Dim system_Store_Handler as Long
system_Store_Handler = CertOpenSystemStore(context_Handler, "MY")

' This is the hard part... Find cert in store
Dim i as Long
Dim j As CERT_CONTEXT
    
i = CertFindCertificateInStore( _
        CLng(system_Store_Handler), _
        CLng(MY_ENCODING_TYPE), _
        0, _
        CLng(CERT_FIND_ANY), _
        "", _
        j)
' always get 0, help

End Sub

[dimsumZ]

API declarations :

Public Declare Function CryptAcquireContext Lib "advapi32.dll" Alias "CryptAcquireContextA" _
    (ByRef phProv As Long, _
    ByVal pszContainer As String, _
    ByVal pszProvider As String, _
    ByVal dwProvType As Long, _
    ByVal dwFlags As Long) As Long

Public Declare Function CertOpenSystemStore Lib "Crypt32" Alias "CertOpenSystemStoreA" ( _
    hCryptProv As Long, _
    szSubsystemProtocol As String) As Long

Public Declare Function CertFindCertificateInStore Lib "Crypt32" ( _
    hCertStore As Long, _
    dwCertEncodingType As Long, _
    dwFindFlags As Long, _
    dwFindType As Long, _
    pvFindPara As String, _
    pPrevCertContext As CERT_CONTEXT _
) As Long

Any Hints Please?

[Merrion]

The first time you call CertFindCertificateInStore you need to pass NULL in pPrevContext - which is why you need the CertFindCertificateInStoreByLong Alias.

Dim i as Long
Dim j As CERT_CONTEXT
    
i = CertFindCertificateInStoreByLong( _
        CLng(system_Store_Handler), _
        CLng(MY_ENCODING_TYPE), _
        0, _
        CLng(CERT_FIND_ANY), _
        "", _
        vbNull) '<--This must be null the first time...
 
'\\ i now points to a memory address...you need to use RTLMovememory to get the data thence...

I usually ALIAS RtlMovememory to prevent GPFs - for CERT_CONTEXT it woulkd be thus:

Private Declare Sub CopyMemoryCERT_CONTEXT Lib "kernel32" Alias "RtlMoveMemory" (Destination As CERT_CONTEXT, ByVal Source As Long, ByVal Length As Long)
Private Declare Function IsBadReadPtr Lib "kernel32" (ByVal lp As Long, ByVal ucb As Long) As Long
Private Declare Function IsBadWritePtr Lib "kernel32" (ByVal lp As Long, ByVal ucb As Long) As Long

which you would add to your code thus:

'...
If Not IsBadReadPtr(i, Len(j)) Then
   Call CopyMemoryCERT_CONTEXT(j,i,Len(j))
End If

HTH,
Duncan

[dimsumZ]

Many thanks, Merrion!