Database query built from user-controlled sources¶

ID: swift/sql-injection
Kind: path-problem
Security severity: 8.8
Severity: error
Precision: high
Tags:
   - security
   - external/cwe/cwe-089
Query suites:
   - swift-code-scanning.qls
   - swift-security-extended.qls
   - swift-security-and-quality.qls

Click to see the query in the CodeQL repository

If a database query (such as a SQL query) is built from user-provided data without sufficient sanitization, a user may be able to run malicious database queries. An attacker can craft the part of the query they control to change the overall meaning of the query.

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 without sufficient sanitization.

Example¶

In the following example, a SQL query is prepared using string interpolation to directly include a user-controlled value userControlledString in the query. An attacker could craft userControlledString to change the overall meaning of the SQL query.

let unsafeQuery = "SELECT * FROM users WHERE username='\(userControlledString)'" // BAD

try db.execute(unsafeQuery)

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

let safeQuery = "SELECT * FROM users WHERE username=?"

let stmt = try db.prepare(safeQuery, userControlledString) // GOOD
try stmt2.run()

References¶

Wikipedia: SQL injection.
OWASP: SQL Injection Prevention Cheat Sheet.
Common Weakness Enumeration: CWE-89.