What is an SQL injection? Provide an example of a vulnerable query and methods of protection.

SQL injection is a vulnerability where an attacker can inject malicious SQL code into a database query through user input. This can lead to unauthorized access, modification, or deletion of data.

Example of a vulnerable query in Go:

username := r.FormValue("username")
query := fmt.Sprintf("SELECT * FROM users WHERE username = '%s'", username)
rows, err := db.Query(query)

If the user enters username as ' OR '1'='1, the query becomes:

SELECT * FROM users WHERE username = '' OR '1'='1'

which returns all records.

Protection methods:

• Using prepared statements with parameterization:

stmt, err := db.Prepare("SELECT * FROM users WHERE username = ?")
rows, err := stmt.Query(username)

• Validation and escaping of user input.
• Using ORMs that automatically protect against injections.
• Limiting database access rights.

Thus, the main protection is query parameterization, which separates SQL code from data.