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Avoiding SQL injection risk

You can avoid an SQL injection risk by providing SQL parameter values as sql package function arguments. Many functions in the sql package provide parameters for the SQL statement and for values to be used in that statement’s parameters (others provide a parameter for a prepared statement and parameters).

Code in the following example uses the ? symbol as a placeholder for the id parameter, which is provided as a function argument:

// Correct format for executing an SQL statement with parameters.
rows, err := db.Query("SELECT * FROM user WHERE id = ?", id)

sql package functions that perform database operations create prepared statements from the arguments you supply. At run time, the sql package turns the SQL statement into a prepared statement and sends it along with the parameter, which is separate.

Note: Parameter placeholders vary depending on the DBMS and driver you’re using. For example, pq driver for Postgres accepts a placeholder form such as $1 instead of ?.

You might be tempted to use a function from the fmt package to assemble the SQL statement as a string with parameters included – like this:

// SECURITY RISK!
rows, err := db.Query(fmt.Sprintf("SELECT * FROM user WHERE id = %s", id))

This is not secure! When you do this, Go assembles the entire SQL statement, replacing the %s format verb with the parameter value, before sending the full statement to the DBMS. This poses an SQL injection risk because the code’s caller could send an unexpected SQL snippet as the id argument. That snippet could complete the SQL statement in unpredictable ways that are dangerous to your application.

For example, by passing a certain %s value, you might end up with something like the following, which could return all user records in your database:

SELECT * FROM user WHERE id = 1 OR 1=1;