Executing code dynamically is security sensitive. It has led in the past to the following vulnerabilities:
Some APIs enable the execution of dynamic code by providing it as strings at runtime. These APIs might be useful in some very specific
meta-programming use-cases. However most of the time their use is frowned upon as they also increase the risk of Injected Code. Such attacks can either run on the server or in the client (exemple:
XSS attack) and have a huge impact on an application’s security.
Both EXECUTE( ... ) and EXEC( ... ) execute as a command the string passed as an argument. They are safe only if the
argument is composed of constant character string expressions. But if the command string is dynamically built using external parameters, then it is
considered very dangerous because executing a random string allows the execution of arbitrary code.
This rule marks for review each occurrence of EXEC and EXECUTE. This rule does not detect code injections. It only
highlights the use of APIs which should be used sparingly and very carefully. The goal is to guide security code reviews.
Ask Yourself Whether
- the executed code may come from an untrusted source and hasn’t been sanitized.
- you really need to run code dynamically.
There is a risk if you answered yes to any of those questions.
Recommended Secure Coding Practices
The best solution is to not run code provided by an untrusted source. If you really need to build a command string using external parameters, you
should use EXEC sp_executesql instead.
Do not try to create a blacklist of dangerous code. It is impossible to cover all attacks that way.
Sensitive Code Example
CREATE PROCEDURE USER_BY_EMAIL(@email VARCHAR(255)) AS
BEGIN
EXEC('USE AuthDB; SELECT id FROM user WHERE email = ''' + @email + ''' ;'); -- Sensitive: could inject code using @email
END
Compliant Solution
CREATE PROCEDURE USER_BY_EMAIL(@email VARCHAR(255)) AS
BEGIN
EXEC sp_executesql 'USE AuthDB; SELECT id FROM user WHERE email = @user_email;',
'@user_email VARCHAR(255)',
@user_email = @email;
END
See
