In this lesson, we are going to talk
about User Input Sanitization,
and how to recommend appropriate remediation
after a pen test
for sanitizing user input and parameterizing queries.
First, let's define what we mean by user input sanitization.
User Input Sanitization is a security measure
that ensures all input data from users is clean, valid,
and safe before being processed by the application.
This process is crucial to prevent various types
of injection attacks like SQL injection
or cross-site scripting attacks
where malicious users can insert harmful
code into your system through these input fields.
The most basic aspect of input sanitization is
to treat all user input as untrusted
and potentially harmful.
This means you should always validate, filter,
and sanitize any data provided by users before processing it
or storing it in your database.
A key characteristic
of proper input sanitization involves both approved
and unapproved listing techniques.
Approved listing allows only certain characters
or patterns that are known
to be safe, while unapproved listing removes
or escapes characters that are known to be dangerous.
However, relying solely
on unapproved listing is often insufficient
because attackers may find ways to bypass the filters.
Now, let's dive deeper into how
to achieve an effective user input sanitization
with an example.
Imagine a simple login form
where users enter their username and password.
Instead of directly inserting these values into SQL query,
you should use parametrized queries or prepared statements.
This method ensures that user input is treated
as data rather than executable code,
thus preventing SQL injection attacks.
Let's take a look at this SQL statement here.
Let's go over what's happening.
The query is constructed
by directly concatenating user inputs, username,
and password into the SQL string.
This means that
whatever the user inputs is directly inserted
into the SQL query without any filtering or validation.
Why is this snippet of codes susceptible to SQL injection?
If an attacker inputs something like
username = '' OR '1' = '1'
and password = '' OR '1' = '1'
the query becomes the following.
This query will always return true
because 1=1 is always true,
allowing the attacker to bypass authentication
and gain unauthorized access to the database.
The correct code should look something like the following.
Here, the query uses parameterized inputs
where the placeholders question mark are used
for the username and password.
The actual value for a username
and password are supplied separately from the query itself,
typically through a prepared statement
and the programming language being used.
Parameterized queries ensure
that the user inputs are treated
as data rather than executable code.
The database engine recognizes the placeholders
and safely inserts the user inputs into the query.
This means that even if an attacker tries
to input a malicious string, it will be treated
as plain string rather than part
of the SQL code, effectively preventing the SQL attack.
So, how do you recommend appropriate remediation
after pen test for sanitizing user input
and parameterizing queries?
First, start by identifying all input points.
Review the application
to identify all user input points such
as forms, URL parameters, and API endpoints.
You can easily do this with a tool like SonarQube,
which will identify these less safe practices
and provide recommendations.
Second, implement input validation.
Ensure that all user inputs are validated
against expected patterns and formats.
Use approved listing techniques
to allow only known safe inputs.
Third, use parameterized queries.
Update your database queries
to use parameterized queries or prepare statements.
This prevents user inputs from being executed as code.
Four, sanitize output. Sanitize any data
before displaying it back to the user
to prevent a cross-site scripting attack.
Also, use the appropriate encoding functions
to escape special characters.
Conduct regular security testing.
We should always conduct regular security testing,
including automated scans and manual pen tests to identify
and address any new vulnerabilities.
And last but not least, provide user training.
Educate developers about secure coding practices
and the importance of input sanitization
and parameterize queries.
So remember, user input sanitization
and parameterize queries are essential practices
in securing your application against injection attacks.
Always validate, sanitize
and parameterize user inputs
to protect your system and data.
By following these recommendations,
you can effectively mitigate the risk identified
during the penetration test
and maintain a robust security posture.