Статьи Королевства Дельфи


Просмотрщик событий из журнала событий Windows. - часть 3


В принципе уже видно, что для открытия и работы с журналом нам необходимо получить на него указатель передав в функцию в качестве параметра наименование одного из трех журналов. А затем считывать записи в буфер и форматировать их. Как видно буфер который заполняет функция имеет структуру EVENTLOGRECORD.

typedef struct _EVENTLOGRECORD { DWORD Length; DWORD Reserved; DWORD RecordNumber; DWORD TimeGenerated; DWORD TimeWritten; DWORD EventID; WORD EventType; WORD NumStrings; WORD EventCategory; WORD ReservedFlags; DWORD ClosingRecordNumber; DWORD StringOffset; DWORD UserSidLength; DWORD UserSidOffset; DWORD DataLength; DWORD DataOffset; // // Then follow: // // TCHAR SourceName[] // TCHAR Computername[] // SID UserSid // TCHAR Strings[] // BYTE Data[] // CHAR Pad[] // DWORD Length; // } EVENTLOGRECORD, *PEVENTLOGRECORD;

Members
LengthSpecifies the length, in bytes, of this event record. Note that this value is stored at both ends of the entry to ease moving forward or backward through the log. The length includes any pad bytes inserted at the end of the record for DWORD alignment. ReservedReserved RecordNumberContains a record number that can be used with the EVENTLOG_SEEK_READ flag passed in a call to the ReadEventLog function to begin reading at a specified record. TimeGeneratedThe time at which this entry was submitted. This time is measured in the number of seconds elapsed since 00:00:00 January 1, 1970, Universal Coordinated Time. TimeWrittenSpecifies the time at which this entry was received by the service to be written to the logfile. This time is measured in the number of seconds elapsed since 00:00:00 January 1, 1970, Universal Coordinated Time. EventID Specifies the event. This is specific to the source that generated the event log entry, and is used, together with SourceName, to identify a message in a message file that is presented to the user while viewing the log. EventTypeSpecifies the type of event. This member can be one of the following values.

ValueMeaning EVENTLOG_ERROR_TYPEError event EVENTLOG_WARNING_TYPEWarning event EVENTLOG_INFORMATION_TYPEInformation event EVENTLOG_AUDIT_SUCCESSSuccess Audit event EVENTLOG_AUDIT_FAILUREFailure Audit event For more information, see Event Types. NumStringsSpecifies the number of strings present in the log (at the position indicated by StringOffset). These strings are merged into the message before it is displayed to the user. EventCategorySpecifies a subcategory for this event. This subcategory is source specific. ReservedFlagsReserved ClosingRecordNumberReserved StringOffsetSpecifies the offset of the strings within this event log entry. UserSidLengthSpecifies the length, in bytes, of the UserSid member. This value can be zero if no security identifier was provided. UserSidOffsetSpecifies the offset of the security identifier (SID) within this event record. To obtain the user name for this SID, use the LookAccountSid function. DataLength Specifies the length, in bytes, of the event-specific data (at the position indicated by DataOffset). DataOffsetSpecifies the offset of the event-specific information within this event record. This information could be something specific (a disk driver might log the number of retries, for example), followed by binary information specific to the event being logged and to the source that generated the entry. SourceName Contains the variable-length null-terminated string specifying the name of the source (application, service, driver, subsystem) that generated the entry. This is the name used to retrieve from the registry the name of the file containing the message strings for this source. It is used, together with the event identifier, to get the message string that describes this event. ComputernameContains the variable-length null-terminated string specifying the name of the computer that generated this event. There may also be some pad bytes after this field to ensure that the UserSid is aligned on a DWORD boundary. UserSidSpecifies the security identifier of the active user at the time this event was logged. This member may be empty if the UserSidLength member is zero. Remarks
  • The defined members are followed by the replacement strings for the message identified by the event identifier, the binary information, some pad bytes to make sure the full entry is on a DWORD boundary, and finally the length of the log entry again. Because the strings and the binary information can be of any length, no structure members are defined to reference them.
  • The event identifier together with SourceName and a language identifier identify a message string that describes the event in more detail. The strings are used as replacement strings and are merged into the message string to make a complete message. The message strings are contained in a message file specified in the source entry in the registry. To obtain the appropriate message string from the message file, load the message file with the LoadLibraryEx function and use the FormatMessage function.
  • The binary information is information that is specific to the event. It could be the contents of the processor registers when a device driver got an error, a dump of an invalid packet that was received from the network, a dump of all the structures in a program (when the data area was detected to be corrupt), and so on. This information should be useful to the writer of the device driver or the application in tracking down bugs or unauthorized breaks into the application.
Как видно структура содержит несколько полей, некоторые из которых необходимо тоже форматировать. Для идентификации пользователя используеться функция LookAccountSid. А описание свойства (event) содержит лишь параметры для детального описания сообщения, которое форматируется с помощью функции FormatMessage. Схему форматирования иллюстрирует следующая диаграмма:




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