I'm building a C application, and for the first time using the MySQL API. I did a little research before I began building my application and stumbled upon this SO question, which talks about not putting user data directly into queries and instead using prepared statements to overcome the possibility of SQL injection - which is just fine and dandy.
I've come round to actually coding my application and I feel like I want to slit my wrists. I haven't used prepared statements before (it's so different to what I'm used to doing normally in my other favourite language, PHP - I'm so used to just writing SQL and escaping data). It so happens that I've also stumbled across the function mysql_real_escape_string. My question is - is it just as safe to escape data in an SQL query (an example below) as it is in a prepared statement?
mysql_real_escape_string(dbc, sBuf, sUserInputData, strlen(sUserInputData));
sprintf(sQuery, "SELECT * FROM `sessions` WHERE `SessionID`='%s';", sBuf);
Related
I find the tightly integrated SQL statement detection in IntelliJ Idea very handy, especially when I want to perform refactoring on a table or a procedure. It will automatically go through my code and adjust the SQL query strings I have which can save me a ton of time.
The problem I am having is that when I create the String using String.format, it will not detect it.
Here are some examples of what it looks like when it works:
And here are some screenshots of what it looks like when it isn't detecting the SQL statements.
Notice how it colors the string when it detects that its a SQL statement and that it's just green when it does not detect that it's a SQL statement.
So when I create the string using the format method - which makes it easier to keep the strings organized and much more readable in general - Idea won't detect the string as a SQL statement, and thus it won't connect it to the tables and procedures I'm accessing which makes refactoring a pain in the arse sometimes.
Does anyone know how I can teach Idea about SQL statement detection within the String.format context?
Thank you,
Mike Sims
According to Node.js' mysql package documentation:
In order to avoid SQL Injection attacks, you should always escape any user provided data before using it inside a SQL query. You can do so using the mysql.escape(), connection.escape() or pool.escape() methods.
I cannot find any documentation / reference to using prepared statements with mysql, except for in a reference to using '?' characters. It states the following:
Alternatively, you can use ? characters as placeholders for values you would like to have escaped...
This looks similar to prepared statements in MySQL, however it really
just uses the same connection.escape() method internally.
From my experience with talking to other developers, the general consensus in the developer community is that prepared statements are the ONLY safe way to perform mysql queries from Node.js however, as you can see with the mysql package, there is no obvious support for prepared statements. However, it is indicated that their method for avoiding SQL injection is via the usage of the escape functions.
My Question:
Are the escape functions in the mysql package sufficient enough to securely query a mysql database (without the use of prepared statements)?
Escaping is actually just as safe as using parameterized queries, if you do it consistently.
But it's recommended to use parameters because it makes your code simpler. Therefore developers are probably more likely to do it.
If the Node.js library makes it just as convenient as parameters, but implements it internally by modifying query strings, replacing the ? marks with the parameter values, then you're good.
For what it's worth, Python's MySQL driver does this too, and also PHP's PDO extension when the "emulate prepares" option is in effect. As long as those libraries are well-tested, it should be safe.
FWIW, both escaping and parameters is limited in SQL injection prevention, because in both cases, you can only protect values that you would combine with your SQL query. You cannot protect identifiers (like table names, or column names), or SQL keywords, or expressions, etc. In these cases, just be careful that you have vetted any dynamic content before combining it with your SQL query.
See also:
Preventing SQL injection in Node.js
Difference between real_escape_string and prepare()?
I need to convince someone that he needs to sanitize the user input in addition to the user of stored procedures. well I know I sound crazy but I do not feel comfortable enough with store procedures only. My first reason is that I am able to cause errors in the stored procedure but because of the fact that the application itself handles errors such that error messages are coded it is difficult for outside to understand the what there are. but I still think that this is not secure.
Does any one has a suggestion ? or am I wrong to doubt stored procedures?
No it's not safe on it's own. You can also do in a stored procedure something like this:
SET #sql = 'Select * from products where name like ''' +#spinput+''' ';
exec(#sql);
With the wrong value in #spinput you can inject code.
However you can write stored procedures that are safe against sql injection.
Even if you use proper parameters, you can still mess with the database. You could insert a script that goes in as a parameter, but when it's displayed on a web page starts doing something it shouldn't. Use parameters to ensure your database is used as intended, but also sanitize the output later - never trust user-entered data.
Using stored procedures normally protects against SQL injection, but is not the only solution to prevent SQL injections, and it doesn't protect against all forms of SQL injection.
It's not the stored procedure itself that makes the big difference, but parameterised queries, which is the most common way to call a stored procedure. By putting the values used by the query in parameters, you let the database library handle them instead of having to escape them correctly yourself.
It's possible to write code that is safe against SQL injections without using parameterised queries, but it's difficult. You have to know exactly what characters you need to escape in a string for the specific database that you are using, and if you get it wrong you are pretty much as unprotected as if you didn't know about SQL injections at all.
If you use parameterised queries, then the step of sending the values into the database is safe from SQL injection, but the query itself might not be. If the query generates and executes SQL code itself, you have the same problem with escaping strings correctly. It's however not so usual to create SQL code in the SQL code, and if you do it you are very aware of that you are doing it.
I have a website using mySQL database and I want to do common tasks like add users, modify their info, etc. I can do it perfectly with regular queries. Im using prepared statements to increment security.
Should I use stored procedures to increment the security or the results will be the same? I though that may be using stored procedures I can restrict the direct interaction that a possible attacker could have with the real query. I'm wrong?
I guess it would depend on what language youre using. Using a prepared statement with a sql string that contains all of the sql to be executed, or using a prepared statement with a sql string that executes a stored procedure are going to be about equivalent in most languages. The language should take care of the security around the prepared statement. C# for example will validate the input, so sql injection vulnerabilities are greatly reduced unless your prepared statement is written so poorly that feeding it bad (but expected, ie, 1 vs 0) variables will dramatically change the result set. Other languages may not provide the same level of validation though, so there may be an advantage depending on exactly what your stored proc looks like.
Using a stored procedure is better for maintainability, but there are not many scenarios where its going to provide any sort of change in security level, assuming the program is properly designed to begin with. The only example i can think of off the top of my head would be a stored procedure that takes raw sql strings from user input, and then executes that sql against the db. This is actually less secure than using a prepared statement unless you went to great lengths to validate the acceptable input, in which case you better have a really good reason for using such a stored proc in the first place.
Basically, what I'm saying boils down to the fact that you're going to need to read the documentation for your language about prepared statements, and determine what vulnerabilities, if any, using prepared statements may have, and whether or not those can be eliminated in your specific scenario by switching to a prepared statement that calls out a stored procedure instead of executing a sql query directly.
The results would be the same (assuming that you set your stored procedure up right).
there appears to be a pretty good write up on it here. Though I would never suggest you try to escape user input yourself. (They mention this as option 3)
I'm trying to find some way to obfuscate SQL code in MySQL.
In the Oracle databases exists the "wrap" funcionality, but I didn't found some similar. Some ideas?
The final goal is that the client has some difficuties to understand the code.
I think MySQL do not have the ability to obfuscate the code. You can encapsulate the whole SQL query code by creating a STORED PROCEDURE, although not encapsulated but at least your whole SQL query is not shown when used inside your code (PHP, .Net, and the like...).
MySQL does not have any obfuscation abilities - you could write some code that would be confusing to read by having some other table with defined values that you could use IF statements against to make your code difficult to read...
SELECT co1, co2, IF(3 > 18, co3, '') AS co3 FROM table INNER JOIN...
etc... or using COUNTs as parameters in conditional statements is as best as you're going to get (obviously performance may become an issue depending on how "obfuscated").