I am trying to build a scenario that would allow me to expose additional data from a server (for case-demo purposes). The server calls a vulnerable SQL code:
EXEC my_storeProc '12345'
where "12345" (not the single quotes) is the parameter. This performs a SELECT statement. I would like to eliminate this execution and instead call my own select statement, however the server side code will only accept the first select statement called, contained within the aforementioned EXEC call. Calling the second statement is easy:
EXEC my_storeProc '12345 ' select * from MySecondTable--
(the -- at the end will block the closing single quote added by the server to prevent errors). My problem is that although there are 2 select statements, the server will only parse the first one. Is there a way to cancel the first EXEC call without throwing an error so that the second one would be taken instead? Perhaps even a UNION but there isn't much I can do with only one variable open to exploit (variable being 12345 in this case).
You have to think of how it will be executed, specifically you want it called so it doesn't raise an exception and put the kabosh on the whole statement. You can't set the result to always true with a proc call, so there is no real way escape the proc. Instead, you'll want to slip a second command in, Your desired code looks like;
exec my_Storeproc '1234'; select * from mysecondtable
So we need to close the quotes, and make a new statement. That would mean the string with the insert needs to be;
1234'; select * from mysecondtable where 1 = '1
There is a flaw in this, whatever command you are executing is not being returned to the UI. To get the data you'll have to add a server connection to the second command.
To make the second command unnecessary you would have to inject code into the proc, which is a non starter since the proc is already complied and sql injection relies on confusing the compiler as to what is data and what is commands. For a more verbose explanation of that check out this answer:
https://security.stackexchange.com/a/25710
I was not able to solve this by myself so I hope I didn't miss any similar post here and I'm not wasting your time.
What I want is to identify (get a list) of all strings used in SQL Server code.
Example:
select 'WordToCatch1' as 'Column1'
from Table1
where Column2 = 'WordToCatch2'
If you put above code to SSMS all three words in apostrophes will be red but only words 'WordToCatch1' and 'WordToCatch2' are "real" strings used in code.
My goal is to find all those "real" strings in any code.
For example if I will have stored procedure 10k rows long it would be impossible to search them manually so I want something what will find all those "real" strings for me and return a list of them or something.
Thanks in advance!
The trouble is, Column1 is nothing particular different compared to WordToCatch1 and WordToCatch2 - not unless you parse the SQL yourself. You could modify your query to take the quotes away from Column1 and it will show up coloured black.
I guess a simple regex will show up all identifiers after an AS keyword, which would be easier than fully parsing SQL, if all the unwanted strings are like that, and its not just an example.
I have a case statement that will set a varchar variable #stored_proc_name to the name of a procedure that I want to call later on. One of the procedures I want to call takes a varchar as an argument (and also an int). How do I do this? Currently what I have is this
SELECT #stored_proc_name = CASE #p_process_name
WHEN 'misdate' THEN 'findb..sp_cycle_date_daily'
WHEN 'balpremmis' THEN 'findb..pc_bal_writ_prem'
WHEN 'ursctl' THEN 'MIS_feeds..pc_mis_update_feed_control "URSPO", 1'
ELSE NULL
END
EXECUTE #stored_proc_name
The last one is my procedure that takes arguments, where "URSPO" should be the first, and 1 is the int. It is running on SQL server 2k8 (I think I remember some difference with single vs. double quotes between this and older versions). Is what I have correct? I admit that I haven't tested it yet, but it is a part of a huge process that I really don't want to kick off right now.
Thank for any help!
To escape a single quote inside a string literal, use a double quote like below. See the Constants section in the BOL for more information:
select ' '' ' -- creates a string containing a space, a single quote, and another space
In your example, this would be the string:
'MIS_feeds..pc_mis_update_feed_control ''URSPO'', 1'
If you were going to use this string in a LIKE expression, you might want to refer to this question.
And if you were going to build a string to be a SQL identifier, you might want to escape it using the QUOTENAME function.
You can use the code below:
set quoted_identifier off;
Select "'Hi'"
quoted_identifiere will enable you to use ", instead of ';
My co-worker is being unsafe with his code and is allowing a user to upload an SQL file to be run on the server.
He strips out any key words in the file such as "EXEC", "DROP", "UPDATE", "INSERT", "TRUNC"
I want to show him the error of his ways by exploiting his EXEC ( #sql )
My first attempt will be with 'EXEXECEC (N''SELECT ''You DRDROPOPped the ball Bob!'')'
But he might filter that all out in a loop.
Is there a way I can exploit my co-worker's code? Or is filtering out the key words enough?
Edit: I got him to check in his code. If the code contains a keyword he does not execute it. I'm still trying to figure out how to exploit this using the binary conversion.
Tell your co-worker he's a moron.
Do an obfuscated SQL query, something like:
select #sql = 0x44524f5020426f627350616e7473
This will need some tweaking depending on what the rest of the code looks like, but the idea is to encode your code in hex and execute it (or rather, let it be executed). There are other ways to obfuscate code to be injected.
You've got a huge security hole there. And the funny part is, this is not even something that needs to be reinvented. The proper way to stop such things from happening is to create and use an account with the correct permissions (eg: can only perform select queries on tables x, y and z).
Have a look at ASCII Encoded/Binary attacks ...
should convince your friend he is doomed.. ;)
And here some help on how to encode the strings ..
Converting a String to HEX in SQL
I have recently taken on a project in which I need to integrate with PHP/SQL Server. I am looking for the quickest and easiest function to prevent SQL injection on SQL Server as I prefer MySQL and do not anticipate many more SQL Server related projects.
Is this function sufficient?
$someVal = mssql_escape($_POST['someVal']);
$query = "INSERT INTO tblName SET field = $someVal";
mssql_execute($query);
function mssql_escape($str) {
return str_replace("'", "''", $str);
}
If not, what additional steps should I take?
EDIT:
I am running on a Linux server - sqlsrv_query() only works if your hosting environment is windows
The best option: do not use SQL statements that get concatenated together - use parametrized queries.
E.g. do not create something like
string stmt = "INSERT INTO dbo.MyTable(field1,field2) VALUES(" + value1 + ", " + value2 + ")"
or something like that and then try to "sanitize" it by replacing single quotes or something - you'll never catch everything, someone will always find a way around your "safe guarding".
Instead, use:
string stmt = "INSERT INTO dbo.MyTable(field1,field2) VALUES(#value1, #value2)";
and then set the parameter values before executing this INSERT statement. This is really the only reliable way to avoid SQL injection - use it!
UPDATE: how to use parametrized queries from PHP - I found something here - does that help at all?
$tsql = "INSERT INTO DateTimeTable (myDate, myTime,
myDateTimeOffset, myDatetime2)
VALUES (?, ?, ?, ?)";
$params = array(
date("Y-m-d"), // Current date in Y-m-d format.
"15:30:41.987", // Time as a string.
date("c"), // Current date in ISO 8601 format.
date("Y-m-d H:i:s.u") // Current date and time.
);
$stmt = sqlsrv_query($conn, $tsql, $params);
So it seems you can't use "named" parameters like #value1, #value2, but instead you just use question marks ? for each parameter, and you basically just create a parameter array which you then pass into the query.
This article Accessing SQL Server Databases with PHP might also help - it has a similar sample of how to insert data using the parametrized queries.
UPDATE: after you've revealed that you're on Linux, this approach doesn't work anymore. Instead, you need to use an alternate library in PHP to call a database - something like PDO.
PDO should work both on any *nix type operating system, and against all sorts of databases, including SQL Server, and it supports parametrized queries, too:
$db = new PDO('your-connection-string-here');
$stmt = $db->prepare("SELECT priv FROM testUsers WHERE username=:username AND password=:password");
$stmt->bindParam(':username', $user);
$stmt->bindParam(':password', $pass);
$stmt->execute();
No, it's not sufficient. To my knowledge, string replacement can never really be sufficient in general (on any platform).
To prevent SQL injection, all queries need to be parameterized - either as parameterized queries or as stored procedures with parameters.
In these cases, the database calling library (i.e. ADO.NET and SQL Command) sends the parameters separately from the query and the server applies them, which eliminates the ability for the actual SQL to be altered in any way. This has numerous benefits besides injection, which include code page issues and date conversion issues - for that matter any conversions to string can be problematic if the server does not expect them done the way the client does them.
I partially disagree with other posters. If you run all your parameters through a function that double the quotes, this should prevent any possible injection attack. Actually in practice the more frequent problem is not deliberate sabotague but queries that break because a value legitimately includes a single quote, like a customer named "O'Hara" or a comment field of "Don't call Sally before 9:00". Anyway, I do escapes like this all the time and have never had a problem.
One caveat: On some database engines, there could be other dangerous characters besides a single quote. The only example I know is Postgres, where the backslash is magic. In this case your escape function must also double backslashes. Check the documentation.
I have nothing against using prepared statements, and for simple cases, where the only thing that changes is the value of the parameter, they are an excellent solution. But I routinely find that I have to build queries in pieces based on conditions in the program, like if parameter X is not null then not only do I need to add it to the where clause but I also need an additional join to get to the value I really need to test. Prepared statements can't handle this. You could, of course, build the SQL in pieces, turn it into a prepared statement, and then supply the parameters. But this is just a pain for no clear gain.
These days I mostly code in Java that allows functions to be overloaded, that is, have multiple implementations depending on the type of the passed in parameter. So I routine write a set of functions that I normally name simply "q" for "quote", that return the given type, suitably quoted. For strings, it doubles any quote marks, then slaps quote marks around the whole thing. For integers it just returns the string representation of the integer. For dates it converts to the JDBC (Java SQL) standard date format, which the driver is then supposed to convert to whatever is needed for the specific database being used. Etc. (On my current project I even included array as a passed in type, which I convert to a format suitable for use in an IN clause.) Then every time I want to include a field in a SQL statement, I just write "q(x)". As this is slapping quotes on when necessary, I don't need the extra string manipulation to put on quotes, so it's probably just as easy as not doing the escape.
For example, vulnerable way:
String myquery="select name from customer where customercode='"+custcode+"'";
Safe way:
String myquery="select name from customer where customercode="+q(custcode);
The right way is not particularly more to type than the wrong way, so it's easy to get in a good habit.
String replacement to escape quotes IS sufficient to prevent SQL injection attack vectors.
This only applies to SQL Server when QUOTED_IDENTIFIER is ON, and when you don't do something stoopid to your escaped string, such as truncating it or translating your Unicode string to an 8-bit string after escaping. In particular, you need to make sure QUOTED_IDENTIFIER is set to ON. Usually that's the default, but it may depend on the library you are using in PHP to access MSSQL.
Parameterization is a best practice, but there is nothing inherently insecure about escaping quotes to prevent SQL injection, with due care.
The rel issue with escaping strings is not the efficacy of the replacement, it is the potential for forgetting to do the replacement every time.
That said, your code escapes the value, but does not wrap the value in quotes. You need something like this instead:
function mssql_escape($str) {
return "N'" + str_replace("'", "''", $str) + "'";
}
The N above allows you to pass higher Unicode characters. If that's not a concern (i.e., your text fields are varchar rather than nvarchar), you can remove the N.
Now, if you do this, there are some caveats:
You need to make DAMNED SURE you call mssql_escape for every string value. And therein lies the rub.
Dates and GUID values also need escaping in the same manner.
You should validate numeric values, or at least escape them as well using the same function (MSSQL will cast the string to the appropriate numeric type).
Again, like others have said, parameterized queries are safer--not because escaping quotes doesn't work (it does except as noted above), but because it's easier to visually make sure you didn't forget to escape something.