Testing for Input Validation

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Data Validation Testing
The most common web application security weakness is the failure to properly validate input from the client or environment. This weakness leads to almost all of the major vulnerabilities in applications, such as interpreter injection, locale/Unicode attacks, file system attacks and buffer overflows. Data from any external entity/client should never be trusted for an external entity/client has every possibility to tamper with the data: "All Input is Evil" says Michael Howard in his famous book "Writing Secure Code". That's rule number one. The problem is that in a complex application the points of access for an attacker increase and it is easy that you forget to implement this rule. In this chapter we describe how to test all the possible forms of input validation to understand if the application is strong enough against any type of data input. We split Data Validation into this macro categories:

4.6.1 Cross site scripting We talk about Cross Site Scripting (XSS) testing when try to manipulate the parameters that the application receive in input. We find a XSS when the application doesn't validate our input and creates an output that we have built. A XSS breaks the following pattern: Input -> Output == cross-site scripting

4.6.1.1 HTTP Methods and XST Cross Site Tracing (XST) is a particular XSS testing inwhich we check that the web server is not configured to allow potentially dangerous HTTP commands (methods) and that XST is not possible. A XST breaks the following pattern: Input -> HTTP Methods == XST

4.6.2 SQL Injection We talk about SQL Injection testing when we try to inject a particular SQL query to the Back end DB whithout that the application make an appropriate data validation. The goal is to manipulate data in the database that represents the core of every company. An SQL Injection breaks the following pattern: Input -> Query SQL == SQL injection SQL Injection field comprises: 4.6.2.1 Stored procedure injection 4.6.2.2 Oracle Testing 4.6.2.3 MySQL Testing 4.6.2.4 SQL Server Testing

4.6.3 LDAP Injection LDAP Injection Testing is similar to SQL Injection Testing: the differences are that we use LDAP protocol instead of SQL and the target is an LDAP Server instead of an SQL Server. An LDAP Injection breaks the following pattern: Input -> Query LDAP == LDAP injection Input -> System == command injection 4.6.4 ORM Injection 4.6.5 XML Injection 4.6.6 SSI Injection 4.6.7 XPath Injection 4.6.8 IMAP/SMTP Injection 4.6.9 Code Injection 4.6.10 OS Commanding Input -> Fixed buffer or format string == overflow 4.6.11 Buffer overflow Testing 4.6.11.1 Heap overflow 4.6.11.2 Stack overflow 4.6.11.3 Format string

4.6.12 Incubated vulnerability testing Incubated testing is a complex testing that need more that one data valition vulnerability to work. In every pattern showed the data must be validated by the application before its trusted and processed. Our goal is to test if the application actually does what is meant to do and does not do what its not.