Avoid SQL injections

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Metadata

ID: python-security/variable-sql-statement-injection

Language: Python

Severity: Error

Category: Security

CWE: 89

Description

In Python, SQL injection is a code injection technique used to attack data-driven applications. This vulnerability occurs when an attacker can insert a SQL query through the input data from the client to the application. This is aimed at preventing SQL injection vulnerability.

Preventing SQL injections is critical because they can lead to the exposure of confidential information, loss of data integrity, and other serious database-related issues. If an attacker successfully performs a SQL injection, they might gain unauthorized access to sensitive data, including passwords, credit card numbers, or personal user information.

How to remediate

To avoid SQL injections, use parameterized queries or prepared statements instead of building SQL commands using string format or concatenation.

For example, instead of writing a query as:

cursor.execute("SELECT * FROM table WHERE column = '%s'" % value)

You can use

cursor.execute("SELECT * FROM table WHERE column = ?", (value,))

This way, the value is automatically escaped properly by the database driver, thus preventing SQL injection. Also, always validate and sanitize user inputs to ensure they do not contain SQL code.

Non-Compliant Code Examples

def add_product(db_connection, product: Product):
    cursor = db_connection.cursor()
    cursor.execute("INSERT INTO products (id, title) VALUES (NULL, '" + product.name+"');")
    db_connection.commit()

def db_init_users():

    users = [
        ('admin', 'SuperSecret'),
        ('elliot', '123123123'),
        ('tim', '12345678')
    ]

    conn = sqlite3.connect('db_users.sqlite')
    c = conn.cursor()
    c.execute("CREATE TABLE users (username text, password text, failures int, mfa_enabled int, mfa_secret text)")

    for u,p in users:
        c.execute("INSERT INTO users (username, password, failures, mfa_enabled, mfa_secret) VALUES ('%s', '%s', '%d', '%d', '%s')" %(u, p, 0, 0, ''))

    conn.commit()
    conn.close()

stmt = "UPDATE analysis_results SET running_time_sec='{0}' WHERE id={1}".format(nsec, id)

stmt = "UPDATE analysis_results SET running_time_sec='%s' WHERE id=%s" % (nsec, id)

stmt = "UPDATE analysis_results SET"\
        "running_time_sec='%s' WHERE id=%s" % nsec


v = "UPDATE bar SET plop={0}".format(plip)


v = f"DELETE FROM bar WHERE plop={bli}"

cursor.execute(f"DELETE FROM bar WHERE plop={bli}")

cursor.execute("DELETE FROM bar WHERE plop=%s", bli)

v = f"SELECT foo FROM bar WHERE plop={bli}"

v = "SELECT foo FROM bar WHERE plop={0}".format(bli)

v = "UPDATE bar SET plop={0}".format(plip)

cursor.execute("UPDATE bar SET plop={0}".format(plip))

cursor.execute("UPDATE `bar` SET plop={0}".format(plip))

def get_product_by_id(db_connection, product_id):
    cursor = db_connection.cursor()
    res = cursor.execute(f"SELECT id, title from products WHERE id={product_id}")
    data = res.fetchone()
    if data is not None:
        return Product(data[0], data[1])
    else:
        return None

def xss_reflected_page(request, app):
    search = request.args.get('search')

    products = app.db_helper.execute_read(
        f"SELECT * FROM products WHERE name LIKE :search",
        { 'search': f'%{search}%' }
    )

    products = list(
        map(
            lambda p: {
                'id': p[0],
                'name': p[1],
                'price': p[2]
            },
            products
        )
    )

    return render_template(
        'xss-reflected.html',
        products=products
    )

Compliant Code Examples

message = f"<@{user_id}> " + message

def function():
    tag_table = [
        row
        for row in session.execute(
            "SELECT * FROM report.timeseries_by_tag_schedule_tag where id = :id;", {"id": org_one_schedule.id}
        )
    ]

def db_init_users():

    users = [
        ('admin', 'SuperSecret'),
        ('elliot', '123123123'),
        ('tim', '12345678')
    ]

    conn = sqlite3.connect('db_users.sqlite')
    c = conn.cursor()

    for u,p in users:
        c.execute("INSERT INTO users (username, password, failures, mfa_enabled, mfa_secret) VALUES ('%s', '%s', '%d', '%d', '%s')", (u, p, 0, 0, ''))

    conn.commit()
    conn.close()

v = "SELECT foo FROM bar WHERE plop=%s"
cursor.execute(v, (my_valie))

cursor.execute("UPDATE `bar` SET foo=%s", ("baz"))