SQL Injection Vulnerability in Rails

https://groups.google.com/group/rubyonrails-security/browse_thread/thread/7546a238e1962f59

by speleding • 14 years ago

163 49 14 years ago

groups.google.com

danso3• 14 years ago

Is there an example of what this special hash looks like? E resulting hash that is, not necessarily the attack that leads to its construction.

amalag• 14 years ago

Seems they would be close enough that they didn't want to share it. Trying to avoid too many script kiddie attacks on unpatched rails servers.

sanxiyn• 14 years ago

Yes. If you look at attached patches, they include this special hash in the test case.

danso3• 14 years ago

Ah thanks. Sorry, am reading from an iOS device and reflexively ignore all Download links at first.

benmmurphy• 14 years ago

http://blog.pentesterlab.com/2012/06/cve-2012-2661-exploitat...

since it is already public i'm thinking of adding my own write up

speleding2• 14 years ago

I don't believe in security through obscurity but I really think the author of that blog post is not doing the world a favor by explaining how to use this bug with URI encoded copy/paste examples for every script kiddie to use, less than 24 hours after it hit.

Anyway, the gist is: if you have an unpatched rails server stop reading this, you need to upgrade RIGHT AWAY.

tptacek2• 14 years ago

How'd you find this? It's a good one.

mikexstudios• 14 years ago

https://rubyonrails-security.googlegroups.com/attach/fc2da6c...

Scroll down to test_where_error.

purephase• 14 years ago

Good to know. Thanks for sharing.

julian37• 14 years ago

Makes me consider to start always casting URL query parameters as a defensive measure, regardless of this specific vulnerability being patched.

michiel3• 14 years ago

This is probably a best practice you could learn yourself to implement every time you know for sure you don't want a GET/POST variable to be a hash/array. This can also prevent other application errors when someone passes a hash/array which is used somewhere in the code where it is expected to be a string or something.

mseebach2• 14 years ago

I'm not terribly familiar with the Rails feature in question, but it seems to me that GET/POST params should never be interpreted automatically. Parsing a param into any other type than a string should be explicit.

joevandyk2• 14 years ago

A better solution would be to have a way to indicate "this parameter needs to be this type".

params[:id] could be a string, integer, hash, or array when accessed in the controller actions.

revetkn• 14 years ago

> A better solution would be to have a way to indicate "this parameter needs to be this type".

If only there were some kind of concept of typing, perhaps enforced by the language and statically applied, which would eliminate this class of error entirely...boy, that would be helpful in larger systems.

joevandyk2• 14 years ago

It's not just query parameters. Could be post params as well.

sparknlaunch• 14 years ago

In laymen terms what does this mean? I understood SQL injections are one of the most common forms of attack, therefore why has this happened on such a popular framework? Is it user error or rails error?

danso3• 14 years ago

Appears to be Rails error. ActiveRecord provides a convenient method for accessing the database layer. Part of the convenience is that thhe method handles the sanitizing part...something which, when people have to write out themselves, tend to slip up on a rare (but too often) occasion.

The bug reportedly occurs by sending this method a specifically crafted input, which bypasses the sanitization that prevents injection.

So devs who have placed their trust in the ActiveRecord method now have compromised systems

Morg5• 14 years ago

As usual, when you trust a piece of code without reading the source, the fail will be strong.

This is like java's GUID that are random but not unique, etc. you can't guess it from the function name or description, you need to know the internal process to know how it's going to explode and when.

sce• 14 years ago

This only applies to ActiveRecord, I wonder if e.g. DataMapper is vulnerable in a similar way.

snyff2• 14 years ago

So far, I don't think DataMapper is vulnerable. The mapping is not done in the same way (datamapper use hard coded properties).

As an example, the following

  User.all(':email '=> {':id' => '1"'})

will throw

  ArgumentError: condition ":email " does not map to a property or relationship in User
  because of the space before any SQL request is performed.

and

  User.all(':email '=> {':id' => '1"'})

will create the following query:

   Query	SELECT `id`, `email`, `password` FROM `users` WHERE `email` IN ('[":id", "1\""]') ORDER BY `id`
   120602  8:41:03	    3 Quit

fendale3• 14 years ago

Sigh - why oh why doesn't Rails use bind variables? Just about every DBMS I have used supports them (Sqlite, Mysql, Oracle, Sybase I know for sure) and if you correctly bind the variables into the query, fears about SQL Injection pretty much disappear.

Then there is performance - in Oracle bind variables are essential for scalability. I read somewhere that Mysql performs better without bind variables.

For most databases by caching prepared statement handles and binding / executing that handle many times, it will perform better than handling many one off queries. I have benchmarked a 20% improvement in throughput on Oracle by making just that change (which is a one liner in the JDBC driver).

judofyr• 14 years ago

This has nothing to do with bind variables. It was not a bug in how variables were bound/escaped. The bug was that Rails treated a variable (which sometimes is a user input) as a column name in certain cases.

fendale3• 14 years ago

I admit I had not read the actual bug report before I commented, but I just did and it reads:

>Impacted code directly passes request params to the `where` method of an ActiveRecord class like this: Post.where(:id => params[:id]).all >An attacker can make a request that causes `params[:id]` to return a specially crafted hash that will cause the WHERE clause of the SQL statement to query an arbitrary table with some value.

For me that is a classic SQL injection attack that can be avoided 100% of the time if you use bind variables for all user input into an SQL query.

Rails doesn't use bind variables - it uses something that looks similar, but it is actually rails code that escapes and concatenates the user input into the query string before executing it. This bug was in that escaping code. However, if Rails correctly bound the inputs to all queries (which is pretty easy to do) then this escaping code could be removed totally and this problem would never have appeared.

Morg5• 14 years ago

Well maybe you should check that again.

Your approach sounds like you should have stored procs instead. Using prepared statements or variable binding to fight SQL injections is not the best idea, although its widespread.

In most cases where you want a prepared statement, you'd be better off using a stored proc, as you'll skip the expensive optimization every single time.

MySQL is not even a real RDBMS (no ACID, no triggers, fail APIs, etc.), anyone using it should switch to PostgreSQL yesterday unless their data really doesn't matter.

SQL injections are 100% avoided by user input control in the application, and the simplest way is to escape all escape characters, that may require reading a bit of doc but w/e.

ironchef• 14 years ago

"Your approach sounds like you should have stored procs instead." Not necessarily. As one moves towards stored procs, it becomes more common to place business logic in said stored procs. This tends to go against MVC and also limits some scaling options (as your business logic then is executing in your DB). They also often will tie you to a singular DB...making moving DBs more painful.

"Using prepared statements or variable binding to fight SQL injections is not the best idea, although its widespread." I read it not as _the_ best idea, but as yet another layer to potentially catch something. Belt _and_ suspenders if you will.

Don't get me wrong. I'm not saying prepared statements are the greatest thing since sliced bread; however, in oracle or postgresql backed apps, they're a best practice to investigate.

sk5t• 14 years ago

I am weary of reading that every RDBMS does an expensive query-plan calculation on every non-sproc DML... maybe you know of a few that behave this way, but there are plenty that don't.

Alternately, suppose one would like to use SQLite with a competent ORM--what's the harm in that?

fendale3• 14 years ago

> Using prepared statements or variable binding to fight SQL injections is not the best idea

What is the best idea then? If you bind variables to SQL statements, you are SQL injection safe 100% of the time. There is no crafty input sequence that can fool anything.

> In most cases where you want a prepared statement, you'd be better off using a stored proc, as you'll skip the expensive optimization every single time.

I am only qualified to speak about Oracle which is a DB I know extremely well. A query is a query, whether it comes from Java, Perl, Ruby or inside of a stored proc. If you prepare a statement once, and then cache that handle and execute it many times, you optimize the query one time. Also in Oracle, if you prepare-bind-execute one time only, the next time you do the same sequence of steps you Oracle doesn't have to optimize the query again - it can spot it is the same as a previous query and short circuit the process.

Mysql I think doesn't cache SQL statements for later reuse like Oracle, which is why binding isn't as important for performance (in Oracle, not bind queries is a pretty good way to bring the database to its knees) - but its still essential for security.

> SQL injections are 100% avoided by user input control in the application, and the simplest way is to escape all escape characters

What this bug has just proven, is that this escaping is not all that easy - crafty attackers can come up will all sorts of strings that seem to work around the escaping time and time again.

rabidsnail• 14 years ago

I'm surprised more type system nazis haven't come out of the woodwork. This is one of the few serious production bugs that actually would have been caught by static typing.

papsosouid• 14 years ago

>few

Well, at least you're funny.

drivebyacct2• 14 years ago

I liked the part where you insult and slander those of us that appreciate typing and also call out (just one of many) reasons why can be a "good thing".

lsb• 14 years ago

> type system nazis

As a general rule of thumb, unless you mean to say that Hindley-Milner causes genocide, say "sticklers", or "evangelists", or "fanbois" even.

klodolph• 14 years ago

How do I read this? I just get a "sign in" wall... like all other "Google Groups" posts.

Daniel_Newby• 14 years ago

IIRC Google gets confused if you were once logged in. Either log in or delete your Google cookies.

LogicX• 14 years ago

Anyone using Nginx naxsi module to protect against this? https://code.google.com/p/naxsi/

sams99• 14 years ago

prepared statements often eliminate this vector ... the thing is, mysql2 the most popular db access gem for rails does not even implement prepared statements, and AR does not have a mechanism to send these to a db.

In an ideal world the app passes the db gem 'select * from posts where Id = ?', [1] and then the gem takes care of preparing and executing. In all the real world web apps I have seen the number of "distinct" SQL statements they need to run are quite low (in the 100s) so preparing is a no brainer.

I do not see this at all as a Ruby problem it has nothing to do with dynamic typing, I see it as a problem approach to db access. I believe Sequel (another less popular db gem for Ruby) is not even theoretically prone to these kind of issues.

SQL Injection Vulnerability in Rails

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