Fires if a password is needed to open an encrypted file.
The 'callback' is called when the 'FilePasswordNeeded' event is emited.
The argument 'e' has the following properties:
e.fileName e.password e.resultCode
This event fires when the encrypted file specified by FileName is being opened if a valid password has not been provided (either directly, or via the DefaultFilePassword property or CacheFilePassword method). This event will not fire if a valid password has already been provided, or if the file specified by FileName does not exist in the vault.
To allow access to the specified file, set the Password parameter to the correct password.
To prevent access to the specified file, return the CBFSSTORAGE_ERR_INVALID_PASSWORD error code via ResultCode.
Note that this event can be fired on different threads, and possibly even on several threads concurrently. As an alternative to handling this event, applications can provide a default file encryption password using the DefaultFilePassword property, and/or call the CacheFilePassword method (before a file is opened) to specify a one-time-use password.
The ResultCode parameter will always be 0 when the event is fired. If the event cannot be handled in a "successful" manner for some reason (e.g., a resource isn't available, security checks failed, etc.), set it to a non-zero value to report an appropriate error. Please refer to the Error Reporting and Handling topic for more information.
Note: when a storage is opened concurrently in read-only mode by several applications using CBDrive or CBMemDrive class, the event will fire only in the first application. To prevent such a situation, always open a vault in read-write mode.