DOCUMENT:Q239482 24-JUN-2002 [odbc] TITLE :ACC2000: Jet 4.0 Expression Can Execute Unsafe VBA Functions PRODUCT :Open Database Connectivity (ODBC) PROD/VER::4.0 OPER/SYS: KEYWORDS:kbdta ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Access 2000 - Microsoft ODBC Driver for Access, version 4.0 - Microsoft Office 2000 Professional ------------------------------------------------------------------------------- Moderate: Requires basic macro, coding, and interoperability skills. This article applies only to a Microsoft Access database (.mdb). For a Microsoft Access 2002 version of this article, see Q294698. SYMPTOMS ======== Using Jet 4.x, a user is able to call unsafe Visual Basic for Applications functions in query statements from Microsoft Access. For example, the following statement would result in all files being deleted from a computer's current folder: SELECT Shell("Cmd /c del *.*") As c1 From Customers NOTE: The Shell command in this example works in Microsoft Windows NT. The command would have to be modified as follows to work on a computer running Microsoft Windows 95/98: SELECT Shell("Command.com /c del *.*") As c1 From Customers The security risk occurs when expressions contain Visual Basic for Application commands that can be harmful to a computer running the query, for example, Shell commands to delete files or format the computer. CAUSE ===== Jet queries can contain Visual Basic for Applications expressions. These are evaluated during query execution, a behavior that is desirable in many circumstances. However, if part of the query contains the Shell command, it is parsed and executed on the computer. You can block such operations (which is called "Sandbox mode"). However, by default in Microsoft Jet 4.0, Sandbox mode is not enabled for queries that are run in Microsoft Access. It is enabled for all other non-Access applications, such as ODBC. RESOLUTION ========== In order to enable Sandbox mode for non-Access applications, install Microsoft Jet 4.0 Service Pack 3 (SP3) or later. After installing this update, the next time that you run Jet, a new registry key is added to the registry. You can use this new registry key to prevent this type of security risk. The following is the registry key that is added: \\HKEY_LOCAL_MACHINE\Software\Microsoft\Jet\4.0\engines\SandboxMode For additional information about how to obtain the latest Microsoft Jet 4.0 Service Pack, click the article number below to view the article in the Microsoft Knowledge Base: Q239114 ACC2000: Updated Version of Microsoft Jet 4.0 Available in Download Center To make your system more resistant to malicious attacks while at the same time making it possible for older applications to keep running, the operation of the Sandbox mode has changed in the Jet update so that it is fully under your control. You can set the key to the following values, with 0 (zero) being most permissive and 3 being least permissive: +---------------------------------------------------------------------------------------------------------------------------+ | Setting | Description | +---------------------------------------------------------------------------------------------------------------------------+ | 0 | Sandbox mode is disabled at all times. | +---------------------------------------------------------------------------------------------------------------------------+ | 1 | Sandbox mode is used for Access applications, but not for non-Access Applications. | +---------------------------------------------------------------------------------------------------------------------------+ | 2 | Sandbox mode is used for non-Access applications, but not for Access Applications. (This is the default value.) | +---------------------------------------------------------------------------------------------------------------------------+ | 3 | Sandbox mode is used at all times. | +---------------------------------------------------------------------------------------------------------------------------+ STATUS ====== Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. MORE INFORMATION ================ With Sandbox mode enabled, if you try to use Visual Basic for Applications functions in a Jet 4.0 query that are not considered safe, you receive the following error message: JET_errExprUnknownFunction Sandbox Mode Operations Allowed ------------------------------- The following is a list of functions that you can use in Jet queries when Sandbox mode is enabled. Any functions that do not appear in the list are not available in Sandbox mode. +----------------------------------------------------------------------+ | ABS | array | ASC | ASCB | ASCW | ATN | +----------------------------------------------------------------------+ | CBOOL | CBYTE | CCUR | CDATE | CDBL | choose | +----------------------------------------------------------------------+ | CHR | CHR$ | CHRB | CHRB$ | CHRW | CHRW$ | +----------------------------------------------------------------------+ | CINT | CLNG | COS | CSNG | CSTR | CVAR | +----------------------------------------------------------------------+ | CvDate | CVErr | date | DATE$ | DATEADD | dateDiff | +----------------------------------------------------------------------+ | datePart | DATESERIAL | DATEVALUE | day | DDB | error | +----------------------------------------------------------------------+ | error$ | EXP | fix | format | format$ | fv | +----------------------------------------------------------------------+ | hex | hex$ | HOUR | IIF | IMEStatus | inStr | +----------------------------------------------------------------------+ | INT | IPMT | IRR | isDate | isEmpty | ISERROR | +----------------------------------------------------------------------+ | isNull | isNumeric | isObject | lCase | lCase$ | LEFT | +----------------------------------------------------------------------+ | LEFT$ | LEFTB | LEFTB$ | LEN | LENB | LOG | +----------------------------------------------------------------------+ | lTrim | lTrim$ | MID | MID$ | MIDB | MIDB$ | +----------------------------------------------------------------------+ | MINUTE | MIRR | MONTH | NOW | NPER | NPV | +----------------------------------------------------------------------+ | oct | oct$ | partition | PMT | PPMT | PV | +----------------------------------------------------------------------+ | QBColor | RATE | RGB | RIGHT | RIGHT$ | RIGHTB | +----------------------------------------------------------------------+ | RIGHTB$ | rnd | round | rTrim | rTrim$ | SECOND | +----------------------------------------------------------------------+ | sgn | SIN | SLN | space | space$ | sqr | +----------------------------------------------------------------------+ | str | str$ | strComp | strConv | string | string$ | +----------------------------------------------------------------------+ | switch | SYD | TAN | TIME | TIME$ | timer | +----------------------------------------------------------------------+ | timeSerial | TIMEVALUE | TRIM | TRIM$ | typeName | uCase | +----------------------------------------------------------------------+ | uCase$ | val | varType | WEEKDAY | YEAR | | +----------------------------------------------------------------------+ Additional query words: pra ====================================================================== Keywords : kbdta Technology : kbOfficeSearch kbAudDeveloper kbAccessSearch kbAccess2000 kbOffice2000Search kbAccess2000Search kbOffice2000 kbODBCSearch kbODBCAccess400 Version : :4.0 Issue type : kbbug Solution Type : kbfix ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2002.