Practice · 1 of 4
Parameterize the Query
LoginQuery(sql) builds a login lookup by pasting the username into
the query text — the classic injection. Write
Solution.BuildLoginQuery(string username) returning the safe pair
(sql, parameterValue):
``csharp
public static class Solution
{
public static (string Sql, string Value) BuildLoginQuery(string username);
}
`
Contract, graded through the provided CjQuery engine (which mimics a real
driver: placeholders mean "data", pasted text means "query"):
- the SQL contains a @p0 placeholder — the username never appears in the
SQL text,
- the username travels as the parameter value,
- CjQuery.MatchedUsers(sql, value) returns 1 for a normal username and
for the injection attempt "' OR '1'='1"` — the attack must be treated as
just a (nonexistent) username, never as "match everything".
Back to lesson: Practice: Security Practice: Barriers at the Boundary