How Can SQL Injection Occur in INSERT Statements, Even with User Comments, and How Can It Be Prevented?

SQL Injection on INSERT Statement with Comments

When developing web applications, it's crucial to protect against SQL injections, even with supposedly safe operations like INSERT statements that include user input.

In this specific scenario, where a survey web form contains text boxes for comments, SQL injection can indeed occur if the comment input is not handled securely. Consider a user submitting the following malicious comment:

'); DELETE FROM users; --

If the SQL statement for inserting this comment is constructed naively, it could result in an unauthorized deletion of all user records:

INSERT INTO COMMENTS VALUES(123, '"); DELETE FROM users; -- ');

To prevent such attacks, it's essential to use parameterized SQL statements, which do not concatenate user input into the query string. In .NET 2.0, you can utilize the SqlCommand class with parameters. For instance:

string comment = "..."; // User input
int id = 123;
string sql = "INSERT INTO COMMENTS (ID, Comment) VALUES (@id, @comment)";
SqlCommand command = new SqlCommand(sql, connection);
command.Parameters.AddWithValue("@id", id);
command.Parameters.AddWithValue("@comment", comment);
command.ExecuteNonQuery();

• The @id and @comment parameters act as placeholders for the values that will be inserted.
• The AddWithValue method automatically handles parameter escaping and ensures that malicious input is not interpreted as SQL commands.

By employing parameterized SQL statements, you can maintain good coding practices, protect against SQL injections, and prevent unauthorized data manipulation on your survey web page.

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