Aalto University autumn 2012 Outline Single signon OpenId SAML and Shibboleth Corporate IAM Strong identity 2 Single signon SSO Users have too many user accounts Cannot remember the passwords ID: 526988
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Slide1
Identity management
Aalto
University
,
autumn
2012Slide2
Outline
Single sign-on
OpenId
SAML and ShibbolethCorporate IAMStrong identity
2Slide3
Single sign-on (SSO)
Users have too many user accounts
Cannot remember the passwords
Service access slow and inconvenientForgotten, unmanaged accounts are a security risk Need for an SSO solution
SSO types:
Pseudo-SSO
: separate authentication to each service; client software manages the credentials and hides the login from userProxy-based SSO: pseudo-SSO implemented in a proxy; proxy in the network manages user credentials and hides the login details from the client True SSO: user authenticates to a separate authentication service, which asserts user identity to other servicesFederated SSO: authentication between administrative domainsMain problem with SSO systems: there’re so many of them
3Slide4
OpenId
4Slide5
OpenId architecture
Standard for SSO to web sites
http://openid.net/developers/specs/
End user creates an OpenId (=identity) at some
OpenId provider (OP)
End user registers the OpenId at various
relaying parties (RP) i.e. web sitesEnd user authenticates to RP with the help of OPThe end user needs a web browser i.e. user agent (UA)5Slide6
OpenId 2.0 protocol
Identifier is an
HTTP URL
(or XRI): gives the OP addresse.g. username.myopenid.com, https://me.yahoo.com/usernameDirect messages use HTTP POST
Indirect messages use
HTTP GET and Redirect
Data fields sent as URL parameters via the browserMethod of user authentication not specified; typically a password6Slide7
OpenId 2.0 security
Approval /failure message from OP to RP is authenticated with a MAC and timestamp
RP can either establish a MAC key with Diffie-Hellman (step 3) or ask OP to verify the MAC for it (step 7)
TLS is not required by OpenId spec but needed for real security:RP must authenticate OP in the Diffie-Hellman or direct verification stepUA must authenticate OP before user types in the password
TLS can be used between UA and RP to protect service access (Q: does it matter?)
User must pay attention:
Check https and the OP name in the browser address bar before typing in the passwordCheck RP name on OP login page before approving login7Slide8
OpenId notes
What does “open” mean?
Anyone can become an identity provider
User can choose any identity providerServices accept the identity chosen by the userWorks on any web browser without proprietary softwareIn practice, not always so open:
RP policy may determine which OPs are accepted
OP policy may determine which RPs are accepted
For privacy, user-provided id may just point to OP without identifying the usere.g. https://www.google.com/accounts/o8/idOpenId specification is poorly writtenAssumes the reader knows previous versionsUses XRI, Yadis and XRDS
: very complex and incomplete specifications
Security not obvious:
Focus on implementation, not on secure protocol design
Vague security claims especially when used without TLS
8Slide9
SAML and
Shibboleth
9Slide10
SAML 2.0 architecture
Security assertion markup language (SAML 2.0)
OASIS standard
(combines ideas from SAML 1.1, Liberty Alliance identity-federation framework 1.2, and Shibboleth 1.3)Service provider (SP) and
identity provider (
IdP
) establish a trust relation by exchanging metadataPrincipal (= user, subject) registers with the IdPPrincipal authenticates to IdP and then to SP
10Slide11
SAML
SAML is a complex family of protocols:
Assertions
are statements by IdP about a principal, written in XMLProtocols define message flows for requesting assertions
Bindings
define how protocol messages are transported over HTTP, SOAP etc.
Profiles define useful combinations of assertions, protocols and bindingsMetadata defines trust relationsUnlike OpenId, SAML is based on contractual relationsMetadata must be first exchanged between IdP and SPFederation may set rules for its member IdPs and SPs
User cannot decide which id to use where
Typical profile
:
SAML web browser SSO profile
11Slide12
SAML web browser SSO profile
IdP
-initiated
or SP-initiated SSO: User first logs into the IdP, or first connects to SP
Bindings
to HTTP messages
Redirect: message from SP to IdP is sent in GET URL via browser, with help of HTTP redirectionPOST: message between SP and IdP is sent in HTTP form via browser, submitted by user click or scriptArtifact: reference to message is sent in GET URL via browser, with the help of HTTP redirection, and the actual message is retrieved directly from senderSOAP binding not used in this profile
12Slide13
SAML web browser SSO profile
Protocol for SP-initiated SSP:
AuthnRequest and Response
How to send these messages over HTTP? Need to choose bindings; 6 different combinations13Slide14
SAML web browser SSO profile
Example:
redirect-artifact binding
: SP sends <AuthnRequest> to IdP in GET URL with HTTP redirectIdP sends an artifact to SP in GET URL with HTTP redirectSP retrieves <Response> from
IdP
with artifact resolution protocol
14Slide15
SAML security
Response must be signed by
IdP
TSL needed for all connections:Protects password; protects secrecy of user attributes; prevents redirections to wrong siteAttributes in the Response are signed by IdP
15Slide16
Shibboleth 2
Open-source implementation of SAML 2.0 for web
SSO
(wiki)Developed by the Internet 2 projectUsed mainly in research and educational institutions; many other commercial and open-source SAML implementation exist
If
SP supports multiple
IdPs, SP-initiated authentication goes via the where are you from (WAYF) pageOne more step of redirection for the AuthnRequestFederation is a group of IdPs
and SPs that
share
metadata
in one signed file
agree on an
attribute schema
agree on
CA
for TLS
have a
service agreement
that sets out rules for the federation
e.g.
Haka federation
16Slide17
Sessions in Shibboleth
Shibboleth implements two kinds of sessions:
IdP
session between browser and the IdP (IdP
cookies)
user only needs to type in password onceSP session between browser and each SP (SP cookies)Additional application sessions:Web middleware incl. PHP, JSP and ASP.NET implements sessions using
cookies, URL or web form)
Applications
may set their own cookies
No
single
logout
Logging out of SP does not usually log the user out of the
IdP
can log back to SP without password
Logging out of
IdP
does not log the user out of SPs
Logging out of one SO does not log the user out of other SPs
Application sessions complicate the situation further
Shibboleth logout behavior is hard to understand
17Slide18
SAML attributes
In addition to user identity, <Response> from
IdP
to SP contains user attributes Attributes sent to each SP are selected based on attribute filters in metadataExample: cn = Tuomas Aura
o =
Teknillinen
korkeakoulu eduPersonAffiliation = employee;faculty;memberTry https://rr.funet.fi/haka/ User attributes are personal data For legal reasons,
IdP
needs user confirmation before transferring attributes to SP
the annoying check box after
IdP
login
18Slide19
Corporate IAM
19Slide20
Corporate IAM
Federated identity and authentication is not sufficient:
Need to
configure access permissions for users in the servicesNeed to monitor access control state in the systemNeed to revoke access rights
Identity and access management (IAM)
systems
Define roles and groups for the organization Enable centralized role assignment, revocation and monitoringExample:student enrolls to university, then becomes employee, then graduates, finally leaves employmentCentral IAM server and IAM agent at each supported service more expensive to develop and deploy than federated authentication
20Slide21
21
[Internet 2 Middleware Initiative]Slide22
Strong
identity
22Slide23
Strong authentication
Goal:
authentication equivalent to verifying national identity card or passport
Why is it needed?Initial id check when registering new users, e.g. students enrolling to universityRequired by law for access to government services and personal information Increasing trust in commercial online transactions — but this has long since been solved in other waysWhy not use OpenId or SAML?
OpenId allows user to choose identifier
no secure link to a real person
SAML works internally in organizations and between organizations that have a contract not for new, open online services23Slide24
Finnish electronic identity card
Finnish identity cards (
HST-
kortti) have a smartcard chip with three key pairsSignature, encryption and authentication keyshttp://www.fineid.fi/ Keys are certified by the national population register (VRK)Has not gained popularity; few people have an id card; even fewer ever use it for electronic authentication
Why?
24Slide25
Tupas authentication
Tupas
uses bank accounts for strong authentication
Defined by Federation of Finnish Financial Serviceshttp://www.fkl.fi/teemasivut/sahkoinen_asiointi/tupas/ Developed from online the payment system (commonly used in Finland for online purchases)
User authentication with one-time passwords
Advantage: everyone has a bank account, and banks are required to know the identity of their customers
no cost for identity proofingExample: https://password.aalto.fi/ 25Slide26
Tupas authentication
Three-corner authentication model
: user, user’s bank, online service
Each service must set up a shared key with each bank Smaller banks are not supported by all online services
26Slide27
Mobile signature
Mobile phone operators install a
signature key on the SIM
ETSI standard, developed from earlier “business SIM”No direct access from phone to signature key; signatures are requested via the operator’s mobile signature service provider (MSSP)
Advantages: everyone has a SIM card, and operators have 24/7 service for revocation
Four-corner authentication model
:Mobile operators have contracts with each otherEach service and user only needs to have a contract with one operatorDeployment and adoption has been slowRequires identity proofing i.e. checking if the subject identity before issuing the certificate (now done with Tupas in Finland)Operators want a fee for every transaction low number of transactions may not be a viable business
27Slide28
Reading material
Online
:
OpenId 2.0, http://openid.net/developers/specs/ SAML 2.0 Technical Overview, http://www.oasis-open.org/committees/download.php/27819/sstc-saml-tech-overview-2.0-cd-02.pdf
28Slide29
Exercises
How much security does OpenId exactly give if TLS is not used?
Learn about XRI name space and XRI discovery. If XRI is used as the user identifier in OpenId, how is the user supposed to authenticate the OP before typing in the password?
How much difference does it make to security and privacy if the user-provided id points to the OP without identifying the user, and the user identity is entered only at the OP site?Look at the Haka federation metadata for Shibboleth 2. How does this create trust between an IdP and SP? What ways are there to limit the trust?
Can you capture the AuthnRequest and Response messages when logging into Noppa? Which bindings are used?
Why exactly is TLS needed at each stage in SAML/Shibboleth authentication, or is it?
Compare the logout (and re-login) behavior of Noppa, Oodi and nelliportaali.fi. Which sessions get deleted, when and how?Despite similarities in the protocols, OpenId, SAML and Tupas have different goals and make different assumptions about the relations between entities. What differences are there?29