Database query built from user-controlled sources¶

Recommendation¶

Most database connector libraries offer a way to safely embed untrusted data into a query using query parameters or prepared statements. You should use these features to build queries, rather than string concatenation or similar methods. You can also escape (sanitize) user-controlled strings so that they can be included directly in an SQL command. A library function should be used for escaping, because this approach is only safe if the escaping function is robust against all possible inputs.

Example¶

In the following examples, an SQL query is prepared using string formatting to directly include a user-controlled value remote_controlled_string. An attacker could craft remote_controlled_string to change the overall meaning of the SQL query.

// with SQLx

let unsafe_query = format!("SELECT * FROM people WHERE firstname='{remote_controlled_string}'");

let _ = conn.execute(unsafe_query.as_str()).await?; // BAD (arbitrary SQL injection is possible)

let _ = sqlx::query(unsafe_query.as_str()).fetch_all(&mut conn).await?; // BAD (arbitrary SQL injection is possible)

A better way to do this is with a prepared statement, binding remote_controlled_string to a parameter of that statement. An attacker who controls remote_controlled_string now cannot change the overall meaning of the query.

// with SQLx

let prepared_query = "SELECT * FROM people WHERE firstname=?";

let _ = sqlx::query(prepared_query_1).bind(&remote_controlled_string).fetch_all(&mut conn).await?; // GOOD (prepared statement with bound parameter)

References¶

• Wikipedia: SQL injection.

• OWASP: SQL Injection Prevention Cheat Sheet.

• Common Weakness Enumeration: CWE-89.