PWINBIO_VERIFY_CALLBACK callback function (winbio.h)

Called by the Windows Biometric Framework to return results from the asynchronous WinBioVerifyWithCallback function. The client application must implement this function.

Syntax

PWINBIO_VERIFY_CALLBACK PwinbioVerifyCallback;

void PwinbioVerifyCallback(
  [in, optional] PVOID VerifyCallbackContext,
  [in]           HRESULT OperationStatus,
  [in]           WINBIO_UNIT_ID UnitId,
  [in]           BOOLEAN Match,
  [in]           WINBIO_REJECT_DETAIL RejectDetail
)
{...}

Parameters

[in, optional] VerifyCallbackContext

Pointer to a buffer defined by the application and passed to the VerifyCallbackContext parameter of the WinBioVerifyWithCallback function. The buffer is not modified by the framework or the biometric unit. Your application can use the data to help it determine what actions to perform or to maintain additional information about the biometric capture.

[in] OperationStatus

Error code returned by the capture operation.

[in] UnitId

Biometric unit ID number.

[in] Match

A Boolean value that specifies whether the captured sample matched the user identity specified by the Identity parameter.

[in] RejectDetail

Additional information about the failure, if any, to perform the operation. For more information, see Remarks.

Return value

None

Remarks

Currently, the Windows Biometric Framework supports only fingerprint readers. Therefore, if an operation fails and returns additional information in a WINBIO_REJECT_DETAIL constant, it will be one of the following values:

• WINBIO_FP_TOO_HIGH
• WINBIO_FP_TOO_LOW
• WINBIO_FP_TOO_LEFT
• WINBIO_FP_TOO_RIGHT
• WINBIO_FP_TOO_FAST
• WINBIO_FP_TOO_SLOW
• WINBIO_FP_POOR_QUALITY
• WINBIO_FP_TOO_SKEWED
• WINBIO_FP_TOO_SHORT
• WINBIO_FP_MERGE_FAILURE

Examples

The following function calls WinBioVerifyWithCallback to asynchronously determine whether a biometric sample matches the logged on identity of the current user. The callback routine, VerifyCallback, and a helper function, GetCurrentUserIdentity, are also included. Link to the Winbio.lib static library and include the following header files:

• Windows.h
• Stdio.h
• Conio.h
• Winbio.h

HRESULT VerifyWithCallback(BOOL bCancel, WINBIO_BIOMETRIC_SUBTYPE subFactor)
{
    // Declare variables.
    HRESULT hr = S_OK;
    WINBIO_SESSION_HANDLE sessionHandle = NULL;
    WINBIO_UNIT_ID unitId = 0;
    WINBIO_REJECT_DETAIL rejectDetail = 0;
    WINBIO_IDENTITY identity = {0};

    // Find the identity of the user.
    hr = GetCurrentUserIdentity( &identity );
    if (FAILED(hr))
    {
        wprintf_s(L"\n User identity not found. hr = 0x%x\n", hr);
        goto e_Exit;
    }

    // Connect to the system pool. 
    hr = WinBioOpenSession( 
            WINBIO_TYPE_FINGERPRINT,    // Service provider
            WINBIO_POOL_SYSTEM,         // Pool type
            WINBIO_FLAG_DEFAULT,        // Configuration and access
            NULL,                       // Array of biometric unit IDs
            0,                          // Count of biometric unit IDs
            NULL,                       // Database ID
            &sessionHandle              // [out] Session handle
            );
    if (FAILED(hr))
    {
        wprintf_s(L"\n WinBioOpenSession failed. hr = 0x%x\n", hr);
        goto e_Exit;
    }

    // Verify a biometric sample asynchronously.
    wprintf_s(L"\n Calling WinBioVerifyWithCallback.\n");
    hr = WinBioVerifyWithCallback(
            sessionHandle,              // Open session handle
            &identity,                  // User SID or GUID
            subFactor,                  // Sample sub-factor
            VerifyCallback,             // Callback function
            NULL                        // Optional context
            );
    if (FAILED(hr))
    {
        wprintf_s(L"\n WinBioVerifyWithCallback failed. hr = 0x%x\n", hr);
        goto e_Exit;
    }
    wprintf_s(L"\n Swipe the sensor ...\n");

    // Cancel the identification if the bCancel flag is set.
    if (bCancel)
    {
        wprintf_s(L"\n Starting CANCEL timer...\n");
        Sleep( 7000 );

        wprintf_s(L"\n Calling WinBioCancel\n");
        hr = WinBioCancel( sessionHandle );
        if (FAILED(hr))
        {
            wprintf_s(L"\n WinBioCancel failed. hr = 0x%x\n", hr);
            goto e_Exit;
        }
    }

    // Wait for the asynchronous identification process to complete 
    // or be canceled.
    hr = WinBioWait( sessionHandle );
    if (FAILED(hr))
    {
        wprintf_s(L"\n WinBioWait failed. hr = 0x%x\n", hr);
    }

e_Exit:
    if (sessionHandle != NULL)
    {
        WinBioCloseSession(sessionHandle);
        sessionHandle = NULL;
    }

    wprintf_s(L"\n Hit any key to continue...");
    _getch();

    return hr;
}

//------------------------------------------------------------------------
// The following function is the callback for WinBioVerifyWithCallback.
// The function filters the response from the biometric subsystem and 
// writes a result to the console window.
// 
VOID CALLBACK VerifyCallback(
  __in_opt PVOID VerifyCallbackContext,
  __in HRESULT OperationStatus,
  __in WINBIO_UNIT_ID UnitId,
  __in BOOLEAN Match,
  __in WINBIO_REJECT_DETAIL RejectDetail
  )
{
    UNREFERENCED_PARAMETER(VerifyCallbackContext);
    UNREFERENCED_PARAMETER(Match);

    wprintf_s(L"\n VerifyCallback executing");
    wprintf_s(L"\n Swipe processed for unit ID %d\n", UnitId);

    // The identity could not be verified.
    if (FAILED(OperationStatus))
    {
        wprintf_s(L"\n Verification failed for the following reason:");
        if (OperationStatus == WINBIO_E_NO_MATCH)
        {
            wprintf_s(L"\n No match.\n");
        }
        else if (OperationStatus == WINBIO_E_BAD_CAPTURE)
        {
            wprintf_s(L"\n Bad capture.\n ");
            wprintf_s(L"\n Bad capture; reason: %d\n", RejectDetail);
        }
        else
        {
            wprintf_s(L"VerifyCallback failed.");
            wprintf_s(L"OperationStatus = 0x%x\n", OperationStatus); 
        }
        goto e_Exit;
    }

    // The user identity was verified.
    wprintf_s(L"\n Fingerprint verified:\n");

e_Exit:
    return;
}

//------------------------------------------------------------------------
// The following function retrieves the identity of the current user.
// This is a helper function and is not part of the Windows Biometric
// Framework API.
//
HRESULT GetCurrentUserIdentity(__inout PWINBIO_IDENTITY Identity)
{
    // Declare variables.
    HRESULT hr = S_OK;
    HANDLE tokenHandle = NULL;
    DWORD bytesReturned = 0;
    struct{
        TOKEN_USER tokenUser;
        BYTE buffer[SECURITY_MAX_SID_SIZE];
    } tokenInfoBuffer;

    // Zero the input identity and specify the type.
    ZeroMemory( Identity, sizeof(WINBIO_IDENTITY));
    Identity->Type = WINBIO_ID_TYPE_NULL;

    // Open the access token associated with the
    // current process
    if (!OpenProcessToken(
            GetCurrentProcess(),            // Process handle
            TOKEN_READ,                     // Read access only
            &tokenHandle))                  // Access token handle
    {
        DWORD win32Status = GetLastError();
        wprintf_s(L"Cannot open token handle: %d\n", win32Status);
        hr = HRESULT_FROM_WIN32(win32Status);
        goto e_Exit;
    }

    // Zero the tokenInfoBuffer structure.
    ZeroMemory(&tokenInfoBuffer, sizeof(tokenInfoBuffer));

    // Retrieve information about the access token. In this case,
    // retrieve a SID.
    if (!GetTokenInformation(
            tokenHandle,                    // Access token handle
            TokenUser,                      // User for the token
            &tokenInfoBuffer.tokenUser,     // Buffer to fill
            sizeof(tokenInfoBuffer),        // Size of the buffer
            &bytesReturned))                // Size needed
    {
        DWORD win32Status = GetLastError();
        wprintf_s(L"Cannot query token information: %d\n", win32Status);
        hr = HRESULT_FROM_WIN32(win32Status);
        goto e_Exit;
    }

    // Copy the SID from the tokenInfoBuffer structure to the
    // WINBIO_IDENTITY structure. 
    CopySid(
        SECURITY_MAX_SID_SIZE,
        Identity->Value.AccountSid.Data,
        tokenInfoBuffer.tokenUser.User.Sid
        );

    // Specify the size of the SID and assign WINBIO_ID_TYPE_SID
    // to the type member of the WINBIO_IDENTITY structure.
    Identity->Value.AccountSid.Size = GetLengthSid(tokenInfoBuffer.tokenUser.User.Sid);
    Identity->Type = WINBIO_ID_TYPE_SID;

e_Exit:

    if (tokenHandle != NULL)
    {
        CloseHandle(tokenHandle);
    }

    return hr;
}

Requirements