Boolean based Blind SQL Injection

Blind SQL Injection happens when:

There is a SQL injection vulnerability,

BUT the application does not show any SQL errors or query outputs directly.

In this case, an attacker has to ask questions to the database and observe how the server behaves to extract information bit by bit.

There are two main types:

Boolean-based blind SQLi (based on true/false responses)

Time-based blind SQLi (based on delay in server response)

Real-World Example Setup Imagine a product page with a URL like:

bash Copy Edit http://victim.com/product.php?id=5 and the vulnerable backend PHP code:

php Copy Edit <?php $id = $_GET['id']; $query = "SELECT * FROM products WHERE id = '$id'"; $result = mysqli_query($conn, $query); if (mysqli_num_rows($result) > 0) { // Display the product details $row = mysqli_fetch_assoc($result); echo "Product Name: " . $row['name']; } else { echo "No product found."; } ?> Problems:

No sanitization

User input directly used in SQL query

BUT importantly:

The page only says "Product found" or "No product found"

It does NOT show any SQL error messages or database outputs!

Boolean-Based Blind SQL Injection Basic Attack Idea: Inject a condition that changes the page behavior depending on TRUE or FALSE.

Example payload:

bash Copy Edit http://victim.com/product.php?id=5' AND 1=1 -- 1=1 is TRUE.

So the product page loads normally.

Payload to test FALSE:

bash Copy Edit http://victim.com/product.php?id=5' AND 1=2 -- 1=2 is FALSE.

The page now says "No product found".

Extracting Data Step by Step We can guess characters one by one.

Example: Try to extract the first letter of the database name:

sql Copy Edit ' AND SUBSTRING(database(),1,1)='a' -- URL encoded:

bash Copy Edit http://victim.com/product.php?id=5'%20AND%20SUBSTRING(database(),1,1)='a'%20--+ If the first letter is 'a', page shows "Product found".

Otherwise, "No product found".

We can automate this with a tool like SQLMap, or manually brute-force character by character.