1. Authentication and Identity Management

2. Ideally – Who you are Practically – Something you know (e.g., password) – Something you have (e.g., badge) – Something about you (e.g., fingerprint) Basis for Authentication

3. Password Authentication Alice inputs her password, computer verifies this against list of passwords If computer is broken into, hackers can learn everybody’s passwords – Use one-way functions, store the result for every valid password – Perform one-way function on input, compare result against the list

4. Password Authentication Hackers can compile a list of frequently used passwords, apply one-way function to each and store them in a table – dictionary attack Host adds random salt to password, applies one-way function to that and stores result and salt value – Randomly generated, unique and long enough

5. Password Authentication Someone sniffing on the network can learn the password Lamport hash or S-KEY – time-varying password – To set-up the system, Alice enters random number R – Host calculates x 0= h(R), x 1= h(h(R)), x 2= h(h(h(R))),..., x 100 – Alice keeps this list, host sets her password to x 101 – Alice logs on with x 100, host verifies h(x 100 )=x 101, resets password to x 100 – Next time Alice logs on with x 99

6. Password Authentication Someone sniffing on the network can learn the password – Host keeps a file of every user’s public key – Users keep their private keys – When Alice attempts to log on, host sends her a random number R – Alice encrypts R with her private key and sends to host – Host can now verify her identity by decrypting the message and retrieving R

7. Key Distribution – Confidentiality not needed for public key – Can be obtained ahead of time Performance – Slower than conventional cryptography – Implementations used for key distribution, then use conventional crypto for data encryption Trusted third party still needed – To certify public key – To manage revocation Public Key Authentication

8. Passport Shibboleth Single Sign-On

9. Goal is single sign-on – Solves problem of weak or repeated user/pass combinations Implemented via redirections – Users authenticate themselves to a common server, which gives them tickets – Similar flavor to Kerberos but different environment – many organizations Widely deployed by Microsoft – Designed to use existing technologies in servers/browsers (HTTP redirect, SSL, cookies, Javascript) Passport

10. Client (browser), merchant (Web server), Passport login server Passport server maintains authentication info for client – Gives merchant access when permitted by client Divides client data into profile (address) and wallet (credit card) How Passport Works David P. Kormann and Aviel D. Rubin, Risks of the Passport Single Signon Protocol, Computer Networks, Elsevier Science Press, volume 33, pages 51-58, 2000.

11. How Passport Works David P. Kormann and Aviel D. Rubin, Risks of the Passport Single Signon Protocol, Computer Networks, Elsevier Science Press, volume 33, pages 51-58, 2000. SSL Token = 3DES encrypted authentication info using key merchant shares with passport server Also set cookie at browser (passport)

12. User interface is confusing and may misrepresent the reality – user may log out from a server but not from the Passport or vice versa Single key is used to encrypt cookies for all clients Cookies stay on machine, can be stolen – No authenticator (timestamp) like in Kerberos, enables reuse by others Some Problems with Passport David P. Kormann and Aviel D. Rubin, Risks of the Passport Single Signon Protocol, Computer Networks, Elsevier Science Press, volume 33, pages 51-58, 2000. Read more at http://avirubin.com/passport.html

13. Placed into browser cache by servers to store state about this particular user – Contain any information that server wants to remember about the user as name/value pairs – May contain expiration time – May persist across browser instances Returned to server in clear on new access Only those cookies created for the server’s domain are sent to the server – May not be created by this server Usually used for persistent sign in, shopping cart, user preferences How Cookies Work

14. User logs in using her user/pass – Server sets a cookie with some info – username, password, session ID … – Any future accesses return this info to the server who uses it for authentication (equivalent to user/pass) – Once user signs out the cookie is deleted and the session closed at the server Problems – Cookies can be sniffed, remain on the browser because user did not sign out, be stolen by cross-site scripting or via DNS poisoning Solutions: – Send cookies over SSL, use timed cookies, secure code, bind cookies to IP address of the client, encrypt cookies … Cookies for Authentication Learn more at: http://cookies.lcs.mit.edu/pubs/webauth:tr.pdf http://cookies.lcs.mit.edu/pubs/webauth:tr.pdf

15. Service Provider – Browser goes to Resource Manager who uses WAYF, and user’s Attribute Requester, and decides whether to grant access. “Where are you from” (WAYF) service – Redirects to correct servers Federation to form trusted relationships between providers Federated Identity - Shibboleth

16. 6. I know you now. Redirect to SP, with a handle for user 8. Based on attribute values, allow access to resource Identity Provider (IdP) Web Site Service Provider (SP) Web Site 1. User requests resource 2. I don’t know you, or where you are from LDAP WAYF 3. Where are you from? 4. Redirect to IdP for your org 5. I don’t know you. Authenticate using your org’s web login 1 2 3 4 5 7 7. I don’t know your attributes. Ask the IdP (peer to peer) 6 Client Web Browser 8 Source: Kathryn Huxtable khuxtable@ku.edu 10 June 2005khuxtable@ku.edu

17. Cards – Mag stripe (= password) – Smart card, USB key – Time-varying password Issues – How to validate – How to read (i.e. infrastructure) Something You Have

18. Biometrics – Measures some physical attribute Iris scan Fingerprint Picture Voice Issues – How to prevent spoofing – What if spoofing is possible? No way to obtain new credentials Something About You

19. Require at least two of the classes we mentioned, e.g. – Smart card plus PIN – RSA SecurID plus password – Biometric and password Multi-factor Authentication

20. Authorization and Policy

21. Is principal P permitted to perform action A on object O? – Authorization system will provide yes/no answer Authorization

22. Who is permitted to perform which actions on what objects? Access Control Matrix (ACM) – Columns indexed by principal – Rows indexed by objects – Elements are arrays of permissions indexed by action In practice, ACMs are abstract objects – Huge and sparse – Possibly distributed Access Control

23. Example ACM File/UserTomDickHarry Readme.txtread read, write passwordswrite Term.exeread, write, execute

24. Access Control Lists (ACLs) – For each object, list principals and actions permitted on that object – Corresponds to rows of ACM Instantiations of ACMs File Readme.txtTom: read, Dick: read, Harry: read, write passwordsHarry: write Term.exeTom: read, write, execute

25. Capabilities – For each principal, list objects and actions permitted for that principal – Corresponds to columns of ACM The Unix file system is an example of…? Instantiations of ACMs User TomReadme.txt: read, Term.exe: read, write, execute DickReadme.txt: read HarryReadme.txt: read, write; passwords: write

26. Discretionary Mandatory Rule-based Role-based Originator-controlled Types of Access Control

27. Owners control access to objects Access permissions based on identity of subject/object E.g., access to health information Discretionary Access Control

28. Rules set by the system, cannot be overriden by owners Each object has a classification and each subject has a clearance (unclassified, classified, secret, top-secret) Rules speak about how to match categories and classifications – Access is granted on a match Mandatory Access Control

29. Ability to access objects depends on one’s role in the organization Roles of a user can change – Restrictions may limit holding multiple roles simultaneously or within a session, or over longer periods. – Supports separation of roles Maps to organization structure Role-Based Access Control

30. Final goal of security – Determine whether to allow an operation Depends upon – Policy – Authentication Authorization

31. Policy defines what is allowed and how the system and security mechanisms should act Policy is enforced by mechanism which interprets it, e.g. – Firewalls – IDS – Access control lists Implemented as – Software (which must be implemented correctly and without vulnerabilities) Policy

32. Focuses on controlled access to classified information and on confidentiality – No concern about integrity The model is a formal state transition model of computer security policy – Describes a set of access control rules which use security classification on objects and clearances for subjects To determine if a subject can access an object – Combine mandatory and discretionary AC (ACM) – Compare object’s classification with subject’s clearance (Top Secret, Secret, Confid., Unclass.) – Allow access if ACM and level check say it’s OK Policy models: Bell-LaPadula

33. Mandatory access control rules: – a subject at a given clearance may not read an object at a higher classification (no read-up) – a subject at a given clearance must not write to any object at a lower classification (no write-down). Trusted subjects – the “no write-down” rule does not apply to them – Transfer info from high clearance to low clearance Policy models: Bell-LaPadula

34. Only concerned about integrity – a subject at a given clearance may not write an object at a higher classification (no write-up) – a subject at a given clearance must not read any object at a lower classification (no read-down) Reverse from Bell-LaPadula – as if content with lower integrity pollutes subjects at higher integrity Policy models: Biba

35. Today’s security tools work with no coordinated policy – Firewalls and Virtual Private Networks – Authentication and Public Key Infrastructure – Intrusion Detection and limited response We need better coordination – Not just who can access what, but policy says what kind of encryption to use, when to notify IDS Tools should implement coordinated policies – Policies originate from multiple sources – Policies should adapt to dynamic threat conditions – Policies should adapt to dynamic policy changes Security > Mix Of Point Solutions

36. SECURITY AUDIT RECORDS GAA: Generic Authentication and Authorization Architecture INTRUSION DETECTION UNDER ATTACK GAA API EACL... Authentication Databases Web Servers Firewalls IPSec …

37. Focus integration efforts on authorization and the management of policies used in the authorization decision – Applications shouldn’t care about authentication or identity Separate policy from mechanism – Authorization may be easier to integrate with applications – Hide the calls to individual security services E.g. key management, authentication, encryption, audit GAA: Integration Through Authorization

38. Positive and negative access right Conditions on each rule - evaluated in a given order – Pre-conditions What must be true in order to grant request – Request-result These conditions must be activated regardless of whether the access is granted or not – Mid-conditions What must be true during execution of requested operation – Post-conditions What must be true on completion of requested operation. GAA: Extended ACLs

39. From http://gost.isi.edu/info/gaaapi/eacl.htmlhttp://gost.isi.edu/info/gaaapi/eacl.html – Tom cannot login to the host – Logins from the specified IP address range are permitted, using either X509 or Kerberos for authentication if previous login attempts <= 3. If the request fails, the number of the failed logins should be updated. The connection duration < 8 h. – Anyone, without authentication, can check the status of the host if his IP is in specified range – Host shut downs are permitted, using Kerberos for authentication. On success, the user ID must be logged. On failure, the sysadmin is sent an e-mail Sample EACL

40. Phases of Condition Evaluation GAA-API a.isi.edu, connect, Tom gaa_check_authorization() T/F/U System State EACL gaa_get_object_policy_info() gaa_post_execution_actions() T/F/U gaa_execution_control() T/F/U

41. Dynamic policy evaluation enables response to attacks: – Lockdown system if attack is detected – Establish quarantines by changing policy to establish isolated virtual networks dynamically – Allow increased access between coalition members as new coalitions are formed or membership changes to respond to unexpected events What Dynamic Policies Enable

42. Scenario - LockDown  You have an isolated local area network with mixed access to web services (some clients authenticated, some not).

43. Scenario - LockDown  You have an isolated local area network with mixed access to web services (some clients authenticated, some not).  You need to allow incoming authenticated SSH or IPSec connections.

44. You have an isolated local area network with mixed access to web services (some clients authenticated, some not). You need to allow incoming authenticated SSH or IPSec connections. When such connections are active, you want to lock down your servers and require stronger authentication and confidentiality protection on all accesses within the network. Scenario - LockDown