A1 Injection
This page was based on OWASP reference materials.
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Injection flaws, such as SQL, OS, and LDAP injection occur when untrusted data is sent to an interpreter as part of a command or query. The attacker's attacker’s hostile data can trick the interpreter into executing unintended commands or accessing data without proper authorization.
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SQL Injection Prevention Cheat Sheet
1. Prepared Statements (with Parameterized Queries)
The following code example uses a PreparedStatement, Java's Java’s implementation of a parameterized query, to execute the same database query.
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1.1. Safe Java Prepared Statement ExampleThe following code example uses a PreparedStatement, Java's implementation of a parameterized query, to execute the same database query.
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String custname = request.getParameter("customerName"); // This should REALLY be validated too
// perform input validation to detect attacks
String query = "SELECT account_balance FROM user_data WHERE user_name = ? ";
PreparedStatement pstmt = connection.prepareStatement( query );
pstmt.setString( 1, custname);
ResultSet results = pstmt.executeQuery( );
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h5. 1.2. Hibernate Query Language (HQL) Prepared Statement (Named Parameters) Examples
First is an unsafe HQL Statement
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Query unsafeHQLQuery = session.createQuery("from Inventory where productID='"userSuppliedParameter"'");
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Here is a safe version of the same query using named parameters:
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Defense Option 3: White List Input Validation
Various parts of SQL queries aren't legal locations for the use of bind variables, such as the names of tables or columns, and the sort order indicator (ASC or DESC). In such situations, input validation or query redesign is the most appropriate defense. For the names of tables or columns, ideally those values come from the code, and not from user parameters. But if user parameter values are used to make different for table names and column names, then the parameter values should be mapped to the legal/expected table or column names to make sure unvalidated user input doesn't end up in the query. Please note, this is a symptom of poor design and a full re-write should be considered if time allows. Here is an example of table name validation.
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String tableName;
switch(PARAM):
case "Value1": tableName = "fooTable";
break;
case "Value2": tableName = "barTable";
break;
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default : throw new InputValidationException("unexpected value provided for table name");
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The tableName can then be directly appended to the SQL query since it is now known to be one of the legal and expected values for a table name in this query. Keep in mind that generic table validation functions can lead to data loss as table names are used in queries where they are not expected.
For something simple like a sort order, it would be best if the user supplied input is converted to a boolean, and then that boolean is used to select the safe value to append to the query. This is a very standard need in dynamic query creation. For example:
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public String someMethod(boolean sortOrder) {
String SQLquery = "some SQL ... order by Salary " + (sortOrder ? "ASC" : "DESC");
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Any time user input can be converted to a non-String, like a date, numeric, boolean, enumerated type, etc. before it is appended to a query, or used to select a value to append to the query, this ensures it is safe to do so.
Input validation is also recommended as a secondary defense in ALL cases, even when using bind variables as is discussed later in this article. More techniques on how to implement strong white list input validation is described in the Input Validation Cheat Sheet.
Defense Option 4: Escaping All User Supplied Input
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https://www.securecoding.cert.org/confluence/display/java/IDS51-J.+Properly+encode+or+escape+output3.1 Use ESAPI database encoders for:
https://owasp-esapi-java.googlecode.com/svn/trunk_doc/latest/org/owasp/esapi/codecs/Codec.html
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To minimize the potential damage of a successful SQL injection attack, you should minimize the privileges assigned to every database account in your environment. Do not assign DBA or admin type access rights to your application accounts. We understand that this is easy, and everything just 'works' ‘works’ when you do it this way, but it is very dangerous. Start from the ground up to determine what access rights your application accounts require, rather than trying to figure out what access rights you need to take away. Make sure that accounts that only need read access are only granted read access to the tables they need access to. If an account only needs access to portions of a table, consider creating a view that limits access to that portion of the data and assigning the account access to the view instead, rather than the underlying table. Rarely, if ever, grant create or delete access to database accounts.
If you adopt a policy where you use stored procedures everywhere, and don't don’t allow application accounts to directly execute their own queries, then restrict those accounts to only be able to execute the stored procedures they need. Don't Don’t grant them any rights directly to the tables in the database.
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The safest way to prevent XXE is always to disable DTDs (External Entities) completely. Depending on the parser, the method should be similar to the following:factory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);Disabling DTDs also makes the parser secure against denial of services (DOS) attacks such as Billion Laughs. If it is not possible to disable DTDs completely, then external entities and external doctypes must be disabled in the way that's that’s specific to each parser.
Detailed XXE Prevention guidance for a number of languages and commonly used XML parsers in those languages is provided below.
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- OWASP Top 10 2013 A1-Injection
- OWASP SQL Injection Prevention Cheat Sheet
- LDAP Injection Prevention
- XPath Injection Prevention
- Interpreter Injection
- OWASP Injection Flaws Article
- ESAPI Encoder API
- ESAPI Input Validation API
- ASVS: Output Encoding/Escaping Requirements (V6)
- OWASP Testing Guide: Chapter on SQL Injection Testing
- OWASP Code Review Guide: Chapter on SQL Injection
- OWASP Code Review Guide: Command Injection
- CWE Entry 77 on Command Injection
- CWE Entry 89 on SQL Injection
Videos:
Basic SQL Injection:
http://www.youtube.com/watch?v=pypTYPaU7mM
https://www.youtube.com/watch?v=02mLrFVzIYU&list=PLoyY7ZjHtUUVLs2fy-ctzZDSPpawuQ28d
Advanced SQL by Joe McCray: