Running SQL Server Agent jobs on demand by unauthorized users

http://giladka8.blogspot.sg/2012/05/running-sql-server-agent-jobs-on-demand.html

PROBLEM

You configure some SQL Server Agent jobs to run schedule maintenance tasks, but there is sometimes the need for these tasks to be executed on demand.
You want other users just to run the job, without modifying it.
For those users SQL Server Agent node in Object Explorer is not visible because they have minimum permissions (no SQLAgentOperatorRole)

SOLUTION
Use database impersonation by using EXECUTE AS

USE [master]

GO

CREATE LOGIN [runSqlAgentJobsLogin] WITH PASSWORD=N'123%123',DEFAULT_DATABASE=[master], CHECK_EXPIRATION=OFF, CHECK_POLICY=ON

GO

USE [msdb]

GO

CREATE USER [runSqlAgentJobsLogin] FOR LOGIN [runSqlAgentJobsLogin]

GO

EXEC sp_addrolemember N'SQLAgentOperatorRole', N'runSqlAgentJobsLogin'

GO

CREATE PROCEDURE [RUN_BACKUP_SP] WITH EXECUTE AS 'runSqlAgentJobsLogin'

AS

EXEC sp_start_job @JOB_NAME = 'My_Backup'

GO

GRANT EXECUTE ON [MSDB].[DBO].[RUN_BACKUP_SP] TO [DOMAIN\User]

GO

Now, connect as an unauthorized user to one of the databases and run the following. The user can only run the procedure that runs the job, he cannot see the job or modify it

EXEC [MSDB].[DBO].[RUN_BACKUP_SP]