Voice of the DBA

Tag: security

  • Checking Permissions

    Someone posted this query recently:

    select a.*,name, b.* from sys.database_principals a, sys.database_permissions b

where permission_name = 'INSERT' and b.grantee_principal_id = a.principal_id

    That’s a little ugly, so let’s fix it:

    SELECT  a.name, a.principal_id, a.is_fixed_role
      , a.default_schema_name
      , b.permission_name, b.permission_name
      , b.state_desc
 FROM sys.database_principals a
  INNER JOIN sys.database_permissions b
  ON b.grantee_principal_id = a.principal_id
WHERE permission_name = 'INSERT'

    If you run this, you’ll get INSERT permissions in your database. In this case, the person had one row returned that had “public” in it, as shown.

    results1

    I normally don’t have permissions for public, but in this case I had run this first:

    GRANT INSERT ON Person.Address TO Public

    I don’t recommend permissions for public, and you really ought to run this on all your servers:

    SELECT a.name, a.principal_id, a.is_fixed_role
      , a.default_schema_name
      , b.permission_name, b.permission_name
      , b.state_desc
 FROM sys.database_principals a
  INNER JOIN sys.database_permissions b
  ON b.grantee_principal_id = a.principal_id
WHERE a.name = 'public' AND major_id > 0

    How do you find out which objects have permissions? There’s a clue in the last query. If you scroll across in the results, there’s a major_id column. You can use that to find the object.

    results2

    The OBJECT_NAME function is handy here, and it takes an object_id, which is the major_id. If I run this:

    SELECT OBJECT_NAME(85575343)

    I get “Address” back, which is the object I altered.

    And, of course, we need to clean up

    REVOKE INSERT ON Person.Address TO Public

  • Patch Week

    My email account started getting notices of Windows patches yesterday, indicating it’s patch week again. If you manage Windows devices, be sure you are aware of the patches that came out. The May Bulletin on Technet shows 2 issues, one critical, one important.

    I tend to apply patches late, probably a month after release, just to see if anyone reports an issue. It’s up to you, but be aware of the patches, and if you could be affected, make sure you test machines and then schedule the downtime.

  • Why Use the Principle of Least Privilege?

    This SQL Injection could be a problem in data entry

    SQL Injection is not the fault of the SQL Server. Brian Kelley pointed that out, and reminded me that SQL Injection isn’t an case of malformed SQL. It’s legitimate code, including SQL commands that we might use from any query connection, especially an administrative one. We regularly issue update and delete commands from our applications, and SQL Injection takes advantage of this to issue an update the we might not be expecting.

    Would you expect this input handwritten injection from an application? Or this table guessing attempt? You wouldn’t, but they can come through data entry in your application if the input isn’t well sanitized. Someone setting all your prices to $0.01 or all of your customers to “W3 0wnz U!” isn’t what you want to happen. You can’t necessarily prevent all of these patterns  or check for every permutation, but you can prevent things like ‘shutdown’ or ‘drop table’ from being run by your application. Even adding a new user to the database system isn’t something I would want to allow.

    Education is the key here. As Andy Leonard (blog | @AndyLeonard) would say, design patterns are important. When developers have an understanding of the issue, many of these things will be avoided. Having standard ways to begin building an application, checking for bad input, and setting up database users and permissions easily, should make this easy for anyone that wants to code against a database. We still have work to do here to build better frameworks, and ORM tools that require elevated permissions to the database are not the answer. They might become the answer, but they aren’t a better solution right now.

    Grant Fritchey wrote a nice piece about developers and DBAS, noting the need that we both have the same goals, but need to learn to communicate better.  This is one area where we ought to make an effort to communicate better, pass along education about security issues, and work to make life easier for developers to work with a database.

    That also means teaching them to work with the minimum privileges needed in order to make an application work, just in case someone plans on submitting some input you didn’t expect.

    Steve Jones

    The Voice of the DBA Podcasts

  • SQL Injection Everywhere

    I hope no one SQL Injects my washer

    I was doing the laundry the other day and thinking about SQL Injection. I have this fancy front load model that lets me load fabric softener and bleach into containers for release later, and it occurred to me that if my washing machine were connected to the Internet with some API, it’s possible someone could SQL Inject or buffer overrun a string that might release a stream of bleach into my colors.

    Not terribly dangerous, but it could be annoying, and it is exactly the type of hack some bored teenager would come up with. Then I started thinking about what else they might do. I wrote about the possibilities with cars recently, but what else could a hacker do in a connected world. What if someone could ignite my oven? Likely it wouldn’t do much more than cost me money. Turning up my fridge might make a mess of food, but not dangerous. However what if someone could turn off the lights when they saw you start running down the stairs?  That could be dangerous.

    What if they could remotely enable your sprinklers while you were at work. In some places that could result in a fine. Allowing that to happen a few times might get you arrested. Locking or unlocking your car doors (already a remote possibility) could endanger you. I’m sure there are more malicious possibilities I haven’t thought of, and as we move to a more connected world, I worry we will discover them only when some crime has been committed.

    I like the convenience of adding digital controls and remotes to more parts of our lives, but I do worry that we are doing so in a way that ignores security. Linking the convenience items of our lives to remote digital controls can be dangerous enough. Adding in more essential items, like heating, engines, etc., to the same control bus could be fatal.

    SQL Injection will likely be around for a long time, and it will get used in many new ways as more and more aspects of our lives are digitized. All developers should be aware of how an injection attack occurs, and code to be sure that we don’t allow any un-sanitized input into any of our databases, and that we also require separate authentication for the parts of a system that need more security.

    Steve Jones

    The Voice of the DBA Podcasts