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CertControlStore function

The CertControlStore function allows an application to be notified when there is a difference between the contents of a cached store in use and the contents of that store as it is persisted to storage. Differences can occur as another process makes a change that affects the store as it is persisted.

The CertControlStore function can be used to synchronize a cached store, if necessary, and provides a means to commit changes made in the cached store to persisted storage.

Syntax


BOOL WINAPI CertControlStore(
  _In_  HCERTSTORE hCertStore,
  _In_  DWORD dwFlags,
  _In_  DWORD dwCtrlType,
  _In_  const void *pvCtrlPara
);

Parameters

hCertStore [in]

Handle of the certificate store.

dwFlags [in]

If the dwCtrlType parameter is set to CERT_STORE_CTRL_COMMIT, this parameter can be one of the following values.

ValueMeaning
CERT_STORE_CTRL_COMMIT_FORCE_FLAG

Forces the contents of the cache memory store to be copied to permanent storage even if the cache has not been changed.

CERT_STORE_CTRL_COMMIT_CLEAR_FLAG

Inhibits the copying of the contents of the cache memory store to permanent storage even when the store is closed.

CERT_STORE_CTRL_INHIBIT_DUPLICATE_HANDLE_FLAG

Inhibits a duplicate handle of the event HANDLE. If this flag is set, CertControlStore with CERT_STORE_CTRL_CANCEL_NOTIFY passed must be called for this event HANDLE before closing the hCertStore handle.

 

If dwCtrlType is set to CERT_STORE_CTRL_NOTIFY_CHANGE or CERT_STORE_CTRL_RESYNC, the dwFlags parameter is not used and must be set to zero.

dwCtrlType [in]

Control action to be taken by CertControlStore. The interpretations of pvCtrlPara and dwFlags depend on the value of dwCtrlType. Currently, the following actions are defined.

ValueMeaning
CERT_STORE_CTRL_RESYNC

The cached store is resynchronized and made to match the persisted store.

CERT_STORE_CTRL_NOTIFY_CHANGE

A signal is returned in the space pointed to by pvCtrlPara to indicate that the current contents of the cached store differ from the store's persisted state.

CERT_STORE_CTRL_COMMIT

Any changes made to the cached store are copied to persisted storage. If no changes were made since the cached store was opened or since the last commit, the call is ignored. The call is also ignored if the store provider is a provider that automatically persists changes immediately.

CERT_STORE_CTRL_AUTO_RESYNC

At the start of every enumeration or find store call, a check is made to determine whether a change has been made in the store. If the store has changed, a re-synchronization is done. This check is only done on first enumeration or find calls, when the pPrevContext is NULL.

The pvCtrPara member is not used and must be set to NULL.

CERT_STORE_CTRL_CANCEL_NOTIFY

Cancels notification signaling of the event HANDLE passed in a previous CERT_STORE_CTRL_NOTIFY_CHANGE or CERT_STORE_CTRL_RESYNC. The pvCtrlPara parameter points to the event HANDLE to be canceled.

 

pvCtrlPara [in]

If dwCtrlType is CERT_STORE_NOTIFY_CHANGE, pvCtrlPara is set to the address of a handle where the system signals the notification change event when a change from the persisted state of the store is detected. The handle must be initialized with a call to the function CreateEvent. The pvCtrlPara parameter can be set to NULL for registry-based stores. If pvCtrlPara is NULL, an internal notification change event is created and registered to be signaled. Using the internal notification change event allows resynchronization operations only if the store was changed.

If dwCtrlType is CERT_STORE_CTRL_RESYNC, set pvCtrlPara to the address of the event handle to be signaled on the next change in the persisted store. Typically, this address is the address of the event handle passed with CERT_STORE_CTRL_NOTIFY_CHANGE during initialization. The event handle passed is rearmed. If pvCtrlPara is set to NULL, no event is rearmed.

If dwCtrlType CERT_STORE_CTRL_COMMIT, pvCtrlPara is not used and must be set to NULL.

Return value

If the function succeeds, the function returns nonzero.

If the function fails, it returns zero. For extended error information, call GetLastError.

If dwCtrlType is CERT_STORE_NOTIFY_CHANGE, the function returns nonzero if a handle for the event signal was successfully set up. The function returns zero if the event handle was not set up.

If dwCtrlType is CERT_STORE_CTRL_RESYNC, the function returns nonzero if the resynchronization succeeded. The function returns zero if the resynchronization failed.

If dwCtrlType is CERT_STORE_CTRL_COMMIT, the function returns nonzero to indicate the successful completion of the commit to persisted storage. The function returns zero if the commit failed.

Some providers might not support specific control types. In these cases, CertControlStore returns zero and GetLastError is set to the ERROR_NOT_SUPPORTED code.

Remarks

Resynchronization of a store can be done at any time. It need not follow a signaled notification change event.

CERT_STORE_CTRL_NOTIFY_CHANGE is supported on registry-based store providers by using the RegNotifyChangeKeyValue function.

CertControlStore using CERT_STORE_CTRL_NOTIFY_CHANGE is called once for each event handle to be passed with CERT_STORE_CTRL_RESYNC. These calls using CERT_STORE_CTRL_NOTIFY_CHANGE must be made after each event is created and not after an event has been signaled.

Examples

The following example shows allowing an application to be notified when there is a difference between the contents of a cached store in use and the contents of that store as it is persisted to storage. For the full example including the complete context for this example, see Example C Program: Setting and Getting Certificate Store Properties.



//--------------------------------------------------------------------
// Declare and initialize variables.

HCERTSTORE hCertStore;     // Original certificate store
HANDLE     hEvent;
BOOL       fSignal;

//--------------------------------------------------------------------
// Initialize an event.

if(hEvent = CreateEvent(
    NULL,
    FALSE,          // Manual reset is FALSE
    FALSE,          // The initial state of the event is FALSE
    NULL))
{
     printf("An event has been created. \n");
}
else
{
     printf("The event was not created. \n");
     exit(1);
}

//--------------------------------------------------------------------
// Open the MY certificate store. 

if ( hCertStore = CertOpenStore(
    CERT_STORE_PROV_SYSTEM,
    0,
    NULL,
    CERT_SYSTEM_STORE_CURRENT_USER,
    L"MY"))
{
    printf("The MY store is open. \n");
}
else
{
    printf("The MY store did not open. \n");
    exit(1);
}

//--------------------------------------------------------------------
//  Call CertControlStore the first time with 
//  CERT_CONTROL_STORE_NOTIFY_CHANGE.

if(CertControlStore(
    hCertStore,                        //  The store to be controlled
    0,                                 //  Not used 
    CERT_STORE_CTRL_NOTIFY_CHANGE,     //  Control action type
    &hEvent))                          //  Points to the event handle
                           //  When a change is detected,
                           //  a signal is written to the 
                    //  memory location pointed to by
                    //  hHandle.
{
    printf("Notify change worked. \n");
}
else
{
    printf("Notify change failed. \n");
    exit(1);
}

//--------------------------------------------------------------------
// Wait for the store to change.

fSignal = (WAIT_OBJECT_0 == WaitForSingleObjectEx(
    hEvent,
    1000,        // Number of milliseconds to wait;
            // Use INFINITE to wait indefinitely for
            // a change
    FALSE));

if (fSignal)
{

//--------------------------------------------------------------------
// The store has changed.
// Call the function a second time with CERT_STORE_CTRL_RESYNC.

    if(CertControlStore(
        hCertStore,             // The store to be controlled
        0,                      // Not used
        CERT_STORE_CTRL_RESYNC, // Control action type
        &hEvent))               // The handle of the event 
                                // to be rearmed

    printf("Resynchronization worked. \n");
    
    else
    {
        printf("Resynchronization failed. \n");
        exit(1);
    }
}
else
{
      printf("The store was not changed. \n");
      printf("Resynchronization was not needed. \n");
}

// Release the handle to the store.

if(CertCloseStore(hCertStore,
                   0))
{
        printf("The MY store was closed. \n");
}
else
{
        printf("An error occurred. The MY store was not closed. \n");
}


Requirements

Minimum supported client

Windows XP [desktop apps only]

Minimum supported server

Windows Server 2003 [desktop apps only]

Header

Wincrypt.h

Library

Crypt32.lib

DLL

Crypt32.dll

See also

Certificate Store Functions
CreateEvent
WaitForSingleObjectEx

 

 

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