Web Site Security

1. Web Site Security Representation and Management of Data on the Web

2. We all know this page...

3. Would we want all to know this page?

4. Problem • Want to restrict access to certain Web pages • Must answer the following questions • Which pages should be restricted? • Who should access restricted pages? • How should users be authenticated? • Should Authentication data be Encrypted?

5. Authentication Methods • Several security methods are used: • Declarative Security • Use security mechanisms provided by the server • BASIC and FORM-based will be discussed • Programmatic Security • Security is handled by the Web application programs

6. Declarative Security • Advantage: Application programs (i.e. JSP and Servlets) do not have to do anything special • Advantage: security holes due to bugs are less probable • Disadvantage: Server specific process • Disadvantage: All or nothing security • users can or cannot see the page • sometimes, what we really want is the page content to be dependent on the user

7. Programmatic Security • Advantage: Not server specific • Advantage: Very flexible • Disadvantage: A lot of work to program + all Servlets and JSP have to cooperate for this to work • Disadvantage: Programmer's bugs may lead to security holes

8. GET E.xsl OK + Content Declarative Security: BASIC Realm A /a/A.html /a/B.jsp Realm B /b/C.css E.xsl /b/D.xml F.xml

9. GET /a/B.jsp 401 + Basic realm="A" Declarative Security: BASIC Realm A /a/A.html /a/B.jsp Realm B /b/C.css E.xsl /b/D.xml F.xml

10. GET /a/B.jsp + user:pass OK + Content Declarative Security: BASIC Realm A /a/A.html /a/B.jsp Realm B /b/C.css E.xsl /b/D.xml F.xml

11. GET /a/A.html + user:pass OK + Content Declarative Security: BASIC Realm A /a/A.html /a/B.jsp Realm B /b/C.css E.xsl /b/D.xml F.xml

12. Declarative Security: BASIC • To restrict a set of pages for certain users, the server designates a realm name for these pages and defines the authorized users (usernames and passwords) • When a page is requested without correct authentication information, the server returns a 401 (Unauthorized) response, with the "WWW-Authenticate" header like the following: WWW-Authenticate:Basic realm="realm-name"

13. Declarative Security: BASIC • The browser then prompts the user for a username and a password, and sends them in the "Authorization" header: Authorization:Basicusername:password • The string username:password is trivially encoded (everyone can decode it...) • Through the session, the browser automatically sends the latter authorization header when requesting files under the latter request's directory or when asked to authenticate in the same realm An Example

14. BASIC method in Tomcat • Set up usernames, passwords and roles • Tell the server that your application is using BASIC authentication, and designate a realm name to the application • Specify which URLs should be restricted to which roles

15. 1. Defining Usernames, Passwords, and Roles Define users, passwords and roles in the file $CATALINA_BASE/conf/tomcat-users.xml <tomcat-users> <role rolename="special"/> [more roles...] <user username="snoopy" password="snoopass" roles="special"/> [more users...] </tomcat-users>

16. 2. Tell the Server to use BASIC Security + Define a Realm Name Add to the application's web.xmlthe login method (BASIC) and your chosen realm name <login-config> <auth-method>BASIC</auth-method>     <realm-name>Special Managers</realm-name> </login-config>

17. 3. Define the restrictions in web.xml <security-constraint> <web-resource-collection> <web-resource-name>restricted one</web-resource-name> <url-pattern>/restricted1/*</url-pattern> </web-resource-collection> <web-resource-collection> <web-resource-name>restricted two</web-resource-name> <url-pattern>/restricted2/*</url-pattern> </web-resource-collection>

18. <auth-constraint> <role-name>special</role-name> </auth-constraint> </security-constraint> <login-config>...</login-config> <security-role> <role-name>special</role-name> </security-role>  

21. Custom Error Pages • The default 401-designated error page is returned with the unauthorized response of the server • A 401 page is not shown by the browser, unless • The user cancels the authentication • The page is returned without WWW-Authenticate • In Tomcat, you can define an application-specific error page, however the WWW-Authenticateheader must be added explicitly

22. A Custom Error Page Example Add to the application's web.xml the following: <error-page> <error-code>401</error-code> <location>/error401.jsp</location> </error-page>

23. A Custom Error Page Example (cont) error401.jsp <% response.setHeader ("WWW-Authenticate", "Basic realm=\"Special Managers\""); %> <HTML> <HEAD> <TITLE>Unauthorized</TITLE> </HEAD> <BODY bgcolor="yellow"> <CENTER> <H1>Go away! You are not authorized!!</H1> </CENTER> </BODY> </HTML>

26. Declarative Security: FORM • In the BASIC method, it is the browser's responsibility to get the login and password from its user, and to send it throughout the session • In the FORM method, this responsibility is the server's, while the browser is not aware of the fact that restricted pages are accessed

27. Declarative Security: FORM (cont) • In the first request to a restricted page, the server forwards the request to a login page • Using the form in the login page, the user submits its login and password to a special URL of the server, and the latter stores the information in the session object • On subsequent requests, the server checks the session to see if it contains suitable authentication, in which case the required page is returned

28. Add to web.xml <login-config> <auth-method>FORM</auth-method> <form-login-config> <form-login-page>/admin/login.jsp </form-login-page> <form-error-page>/admin/login-error.html </form-error-page> </form-login-config> </login-config>

29. Create A Login Page myApp/admin/login.jsp <HTML> <HEAD><TITLE>Login</TITLE></HEAD> <BODY BGCOLOR="yellow"><H1>Log In</H1> <H2>Sorry, you must log in before accessing this resource.</H2> <FORM ACTION="<%= response.encodeURL("j_security_check") %>" METHOD="POST"> <TABLE SUMMARY="login form"> <TR><TD>User name:<TD><INPUT TYPE="TEXT" NAME="j_username"> <TR><TD>Password:<TD><INPUT TYPE="PASSWORD" NAME="j_password"> <TR><TD><INPUT TYPE="SUBMIT" VALUE="Log In"> </TABLE> </FORM> </BODY> </HTML>

30. Create a Login-Error Page myApp/admin/login-error.html <HTML> <HEAD> <TITLE>Unauthorized</TITLE> </HEAD> <BODY bgcolor="yellow"> <CENTER> <H1>Go away! You are not authorized!!</H1> </CENTER> </BODY> </HTML>

34. Adding Some Programmatic Security • So far, all or nothing: • can see page or • can't see page • Sometimes we want to allow page content to be dependant on the authorization of the user • Use the following request methods to control content restriction: • boolean isUserInRole(String role) • String getRemoteUser()

35. Example <security-constraint> <web-resource-collection> <web-resource-name>salary</web-resource-name> <url-pattern>/salary.jsp</url-pattern> </web-resource-collection> <auth-constraint> <role-name>executive</role-name> <role-name>employees</role-name> </auth-constraint> </security-constraint>

36. Example (cont) salary.jsp <HTML> <HEAD><TITLE>Average Salary</TITLE></HEAD> <BODY> <H2>Employee average salary: 3895NIS</H2> <% if(request.isUserInRole("executive")) { %> <H2>Executive average salary: 42764NIS</H2> <% } %> </BODY> </HTML>

41. Important: Disable the Servlet Invoker • You protect certain URLs in the application • The http://host/prefix/servlet/Name format of the Servlet invoker will probably not match the patterns of the protected URLs • Thus, the security restrictions are bypassed if the invoker is enabled • For this reasons (and others), the invoker should not be used in published applications

42. SSL Connections

43. Security on the Internet • The Internet is used to transmit sensitive data from clients to servers and vice versa • User passwords • Credit card numbers • Private client data on remote servers (e.g. Banks) • However, data packets are read by several computers on the way from the client to the server and vice versa • Routers, proxies, etc.

44. Security on the Internet (cont) • The following should be provided: • Only the server can read the client requests • Only the client can read the server's responses • Only the client can send requests on behalf of itself • Only the server can send responses on behalf of itself • In short, no one should be able to interfere in the interaction, either be reading the transferred data or by impersonating to one of the sides

45. Symmetric and Asymmetric Keys • Data can be encrypted and decrypted using keys, which are simply large numbers • Symmetric keys: the same key is used for both encoding and decoding of the message • Asymmetric keys: one key is used to encode the message, and another is used to decode it • It is considered practically impossible to decode a message without knowing the decoding key

46. The RSA Cryptography System • RSA was developed in 1977 by Ron Rivest, Adi Shamir and Leonard Adleman • It is the based on the asymmetric key mechanism: • Each participant has a private key and a public key • The public key is known to all and the private key is kept in secret within its owner • Asymmetric keys: the public key is the encoding key and the private key is the decoding key

47. Secure Connection: A Naive Approach • Consider the following protocol: • Server and Client send their public keys to each other • Data is encrypted using the public key of the receiver • What is wrong with this protocol? • Decryption methods (public keys) are known to everyone - everyone can impersonate the participants • A participant cannot tell whether its received key was indeed sent by the other participant

48. SSL Connections • The SSL (Secure Socket Layer) protocol is used to manage security of message transmission on the Internet • Data encryption and decryption is based on symmetric and asymmetric keys • The HTTPS (HTTP over Ssl) protocol is actually the HTTP protocol above SSL transportation

49. SSL in the Network Layers Email Protocols HTTP SSL TCP/IP

50. hello + SSL settings SSL Settings + Certificate The SSL Handshake 1. Client gets the Server's certificate Is this a good certificate? Client Server