How to configure Jet 4.0 to prevent unsafe functions from running in Access 2000 and Access 2002 (239482)

SUMMARY

The Microsoft Jet 4.0 database engine permits you to call unsafe Microsoft Visual Basic for Applications functions through the Microsoft Jet Expression Service. The Jet Expression Service is used to evaluate expressions in forms, in reports, and in queries.

For example, the following SQL statement may cause all files to be deleted from the current folder on your computer:

SELECT Shell("Cmd /c del *.*") As c1 From Customers

Note The Shell command in this example works in Microsoft Windows NT. You must modify the command as follows for the command to work on a computer that is running Microsoft Windows 95 or Microsoft Windows 98:

SELECT Shell("Command.com /c del *.*") As c1 From Customers

The security risk occurs when expressions contain Visual Basic for Applications commands that can do damage to the computer that is running the query, such as Shell commands to delete files or to format the computer.

IN THIS TASK

• Introduction
• Understand how to enable or how to disable Sandbox mode
• Implement Sandbox mode operations
  • Use Sandbox mode operations with Jet 4.0 Service Pack 3 and later
  • Understand Visual Basic for Applications functions that cause errors when called from a Jet query or an Access property when using Jet 4.0 Service Pack 8

INTRODUCTION

The evaluation of expressions is a behavior that is desirable in many circumstances. However, if part of the expression contains a Shell command, the Shell command is parsed and then executed on the computer.

You can use Sandbox mode to block such operations. However, the default for Jet 4.0 Sandbox mode is not to enable Sandbox mode for queries that are run in Microsoft Access. Sandbox mode is enabled for all other non-Access applications, such as Open Database Connectivity (ODBC).

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Understand how to enable or how to disable Sandbox mode

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

You can enable Sandbox mode for non-Access applications. To do this, you must install Microsoft Jet 4.0 Service Pack 3 (SP3) or later. After you install this update, the next time that you run Jet a new registry key is added to the registry. This new registry key prevents this type of possible 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 Jet 4.0 Service Pack, click the following article number to view the article in the Microsoft Knowledge Base: To make your system more resistant to malicious attacks, and at the same time make it possible for older applications to keep running, the operation of Sandbox mode changed in Jet 4.0 Service Pack 8 so that Sandbox mode is completely under your control.

You can set the key to the following values, with 0 (zero) being the most permissive and 3 being the 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.

After you enable Sandbox mode, and then you try to use the unsafe Visual Basic for Applications functions in a Jet 4.0 query, you receive the following error message:

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Implement Sandbox mode operations

How you can implement Sandbox mode is extended in Jet 4.0 Service Pack 8 to be more compatible with Access databases. Previous implementations of Sandbox mode were too restrictive for most Access applications. Starting with Jet 4.0 Service Pack 8, the enhanced Sandbox mode continues to block unsafe Visual Basic for Applications functions, but Jet 4.0 Service Pack 8 now permits the execution of user-defined functions.

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Use Sandbox mode operations with Jet 4.0 Service Pack 3 and later

You can use the following list of functions 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

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Understand Visual Basic for Applications functions that cause errors when called from a Jet query or an Access property when using Jet 4.0 Service Pack 8

The following Visual Basic for Applications functions will cause an error when the functions are called from an expression in a Jet query or from an Access property:

AppActivate	Beep	Calendar	CallByName	ChDir
ChDrive	Command	Command$	CreateObject	CurDir
CurDir$	DeleteSetting	DoEvents	Environ	Environ$
EOF	Err	FileAttr	FileCopy	FileDateTime
FileLen	FreeFile	GetAllSettings	GetAttr	GetObject
GetSetting	Input	Input$	InputB	InputB$
Kill	Load	Loc	LOF	Randomize
Reset	SaveSetting	Seek	SendKeys	SetAttr
Shell	Spc	Tab	Unload	UserForms
Width

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