How to create an application role on SQL Server 2000 from within Visual FoxPro

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SUMMARY

Under some conditions, a database administrator may wish to grant users access to data in a Microsoft SQL Server database through a specific application while restricting direct access to data, using another application (that is, Microsoft SQL Server Query Analyzer, Microsoft Excel, and so forth). Microsoft SQL Server 7.0 and SQL Server 2000 accommodates this situation through the use of application roles. Application roles may be used to grant specific access to data while preventing users from connecting to SQL Server using another application.

This article illustrates how to programmatically create and grant privileges to an application role on SQL Server 7.0 and SQL Server 2000 from within Microsoft Visual FoxPro.

MORE INFORMATION

The security system in Microsoft SQL Server is implemented at the level of the database. This is the best and most robust method for controlling user activities regardless of the application used to communicate with SQL Server. However, there may be situations requiring custom security controls to accommodate the special requirements of an individual application. This is especially true when dealing with complex databases and databases with large tables.

The fundamental differences between standard and application roles are:
  • Application roles contain no members. Users, Microsoft Windows NT(r) groups, and roles cannot be added to application roles; the permissions of the application role are gained when the application role is activated for the user's connection through a specific application(s). A user's association with an application role is due to being capable of running an application that activates the role, rather than being a member of the role.
  • Application roles are inactive by default and require a password to be activated by using the sp_setapprole system stored procedure. The password can be provided by the user, for example, through an application prompt, but it is more likely that the password is incorporated within the application. The password can be encrypted as it is sent to SQL Server.
  • When an application role is activated for a connection by the application, the connection permanently loses all permissions applied to the login, user account, or other groups or database roles in all databases for the duration of the connection. The connection gains the permissions associated with the application role for the database in which the application role exists. Because application roles are applicable only to the database in which they exist, the connection can gain access to another database only by virtue of permissions granted to the guest user account in the other database. Therefore, if the guest user account does not exist in a database, the connection cannot gain access to that database. If the guest user account does exist in the database but permissions to access an object are not explicitly granted to guest, the connection cannot access that object regardless of who created the object. The permissions the user gained from the application role remain in effect until the connection logs out of SQL Server.
The sp_addapprole system stored procedure is used to implement an application role. The Transact SQL syntax for sp_addapprole is:
 sp_addapprole [@rolename =] 'role',
 [@password =] 'StrongPassword'
				
The @rolename argument is a character string for the name of the role. The role is a sysname with no default, that must be a valid identifier that does not already exist in the database.

@password is a character string password that must be passed to the sp_setapprole stored procedure and is required to activate the application role.

Only members of the db_owner and db_securityadmin fixed database roles can execute the sp_addapprole system stored procedure.

The application role is activated from an application with the sp_setapprole stored procedure. The Transact SQL syntax for sp_setapprole is:
    sp_setapprole [@rolename =] 'role' ,
    [@password =] {Encrypt N 'StrongPassword'} | 'StrongPassword'
    [,[@encrypt =] 'encrypt_style']
				
The @rolename argument is the name of the application role that is defined in the current database.

The @password argument is the password that is required to activate the application role. When using the Encrypt function, the password must be converted to a Unicode string by preceding the password with N.

The @encrypt argument specifies the encryption style used by password.

Any user can execute the sp_setapprole system stored procedure by providing the correct password for the role.

The following code example describes how to programmatically create and activate an application role from Visual FoxPro.

Note You must make sure that the user has the appropriate rights
PUBL gcSQLServer
LOCAL lcSQLDataPath, lcConnStr

*!* Insert your SQL Server name and DATA path here.
gcSQLServer = "sphinxsql"
lcSQLDataPath = "d:\mssql7\data\"




lcConnStr = "DRIVER=SQL Server;SERVER=" + gcSQLServer + ";DATABASE=MASTER;uid=UserNamesa;pwd=StrongPassword"
gnConnHandle = SQLSTRINGCONNECT(lcConnStr)

*!* Select the Master Database.
Use_Master=sqlexec(gnConnHandle,'USE MASTER')
IF Use_Master>0
	*!* Determine whether or not the database exists.
	*!* If not, create it.
	sqlcommand="SELECT * FROM SYSDATABASES WHERE NAME = 'TESTROLE'"
	nCheck_Db=sqlexec(gnConnHandle,sqlcommand,'check_db')
	IF RECCOUNT('check_db')<1
		*!* Create a 1 MB database with a 1 MB log file.
		sqlcommand="create database testrole "+ CHR(13) + ;
			"   on primary "+ CHR(13) + ;
			"      (name = 'appdata', "+ CHR(13) + ;
			"      filename = '" + lcSQLDataPath + "testrole.mdf', "+ CHR(13) + ;
			"      size = 1,  "+ CHR(13) + ;
			"      maxsize = 2, "+ CHR(13) + ;
			"      filegrowth = 512 kb) "+ CHR(13) + ;
			"      log on (name = 'applog', "+ CHR(13) + ;
			"      filename ='" + lcSQLDataPath + "testrole.ldf', "+ CHR(13) + ;
			"      size = 1, "+ CHR(13) + ;
			"      maxsize = 3, "+ CHR(13) + ;
			"      filegrowth = 512 kb) "
		nmake_data_file=sqlexec(gnConnHandle,sqlcommand)
	ENDIF
	*!* Use the database.
	nuse_testrole=sqlexec(gnConnHandle,'USE TESTROLE')
	*!* Determine whether or not the testing table exists.
	sqlcommand="SELECT * FROM SYSOBJECTS WHERE NAME='TESTING'"
	ncheck_tbl=sqlexec(gnConnHandle,sqlcommand,'systables')
	IF RECCOUNT('systables')=0
		*!* The table doesn't exist, so create it.
		sqlcommand="CREATE TABLE TESTING (CHARFLD CHAR(10) NULL) "
		nmake_table=sqlexec(gnConnHandle,sqlcommand)
	ENDIF

	*!* Add an application role.
	sqlcommand="SELECT * FROM SYSUSERS WHERE NAME = 'APPTEST'"
	nCheck_role=sqlexec(gnConnHandle,sqlcommand,'approles')
	IF RECCOUNT('approles')=0
		c_role_string="sp_addapprole @rolename = 'apptest', "+ CHR(13) + ;
			"@password = 'app_pwd'"
		check_role=sqlexec(gnConnHandle,c_role_string)
	ENDIF

	*!* Open a new connection to SQL Server and try to insert into the table.
	=check_app()

	*!* Grant All privileges on the testing table to the application role.
	c_grant_string="GRANT ALL ON TESTING TO apptest"
	check_grant=sqlexec(gnConnHandle,c_grant_string)

	*!* Open a new connection to SQL Server and try to insert into the table.
	=check_app()

ENDIF
=sqldisconn(gnConnHandle)

PROCEDURE check_app
	*!* The application role is only activated in this procedure because
	*!* this procedure has a separate connection to the server.
	*!* Create a New connection to SQL Server.
	lcConnStr = "DRIVER=SQL Server;SERVER=" + gcSQLServer + ";DATABASE=MASTER;uid=UserName;pwd=StrongPassword"
	gnconnhandleb=SQLSTRINGCONNECT(lcConnStr)
	*!* Use the database.
	gnselectdatabase=sqlexec(gnconnhandleb,'USE TESTROLE')
	IF gnselectdatabase>0
		*!* Activate the application role.
		gnsetrole=sqlexec(gnconnhandleb,"sp_setapprole 'apptest','app_pwd'")
		IF gnsetrole>0
			*!* Attempt to insert into the testing table.
			gninsert=sqlexec(gnconnhandleb,"INSERT INTO TESTING VALUES ('TEST')")
			IF gninsert>0
				WAIT WINDOW "The application has privileges to insert data into this table."
			ELSE
				WAIT WINDOW "The application was UNABLE to insert data into this table."
			ENDIF
		ENDIF
	ENDIF
	=sqldisconn(gnconnhandleb)


				
When the code is executed and check_app is called before the application role has been granted object permissions on the Testing table, a Wait window with the following message displays:
The application was unable to insert data into this table.
When the check_app procedure is called after the application role has been granted object permissions on the Testing table, a Wait window with the following message displays:
The application has privileges to insert data into this table.

Properties

Article ID: 243053 - Last Review: February 21, 2014 - Revision: 4.5
APPLIES TO
  • Microsoft Visual FoxPro 3.0 Standard Edition
  • Microsoft Visual FoxPro 3.0b Standard Edition
  • Microsoft Visual FoxPro 5.0 Standard Edition
  • Microsoft Visual FoxPro 5.0a
  • Microsoft Visual FoxPro 6.0 Professional Edition
  • Microsoft Visual FoxPro 7.0 Professional Edition
  • Microsoft Visual FoxPro 8.0 Professional Edition
  • Microsoft Visual FoxPro 9.0 Professional Edition
  • Microsoft SQL Server 7.0 Standard Edition
  • Microsoft SQL Server 2000 Standard Edition
Keywords: 
kbnosurvey kbarchive kbcodesnippet kbdatabase kbhowto kbsqlprog KB243053

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