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Subject: Re: [security-services] Tech Overview outstanding issues
On 9/29/06, Eve L. Maler <Eve.Maler@sun.com> wrote: > > Tom, thanks for offering a detailed code example! I think an > SP-initiated SSO flow would be most common and most welcome. I > might also reprise it somewhat in the introductory material, unless > people think that having two examples for similar stuff that differ > only in unimportant details is useful. Attached is an SSO flow with hand-crafted example code. Comments are welcome. Tom Scavo NCSA/University of Illinois ------------------------------------------------------ SAML V2.0 Web Browser SSO Profile This is a possible deployment of the SAML V2.0 Web Browser SSO Profile where the service provider (SP) and the identity provider (IdP) use the HTTP Redirect and HTTP POST bindings, respectively. The message flow begins with a request for a secured resource at the SP. 1) Request the target resource at the SP The client requests a target resource at the service provider: https://sp.org/myresource The service provider performs a security check on behalf of the target resource. If a valid security context at the service provider already exists, skip steps 2--7. 2) Redirect to the Single Sign-on (SSO) Service at the IdP The service provider redirects the client to the Single Sign-on (SSO) Service at the identity provider. A RelayState parameter and a SAMLRequest parameter are appended to the redirect URL. The value of the SAMLRequest parameter is a URL-encoded string constructed from the following request: <samlp:AuthnRequest xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol" ID="identifier_1" Version="2.0" IssueInstant="2004-12-05T09:21:59Z" AssertionConsumerServiceIndex="1"> <saml:Issuer>https://sp.org/SAML2</saml:Issuer> <samlp:NameIDPolicy AllowCreate="true" Format="urn:oasis:names:tc:SAML:2.0:nameid-format:transient"/> </samlp:AuthnRequest> Before the <samlp:AuthnRequest> element is URL-encoded and appended to the redirect URL, it is first deflated and base64-encoded (in that order). 3) Request the SSO Service at the IdP The client requests the SSO service at the identity provider: https://idp.org/SAML2/SSO/Redirect?SAMLRequest=request&RelayState=token where token is an opaque reference to state information maintained at the service provider and request is the encoded <samlp:AuthnRequest> element from step 2. The SSO service processes the AuthnRequest (by URL-decoding, base64-decoding and inflating, in that order) and performs a security check. If the user does not have a valid security context, the identity provider identifies the user (details omitted). 4) Respond with an HTML form The SSO service validates the request and responds with a document containing an HTML form: <form method="post" action="https://sp.org/SAML2/SSO/POST" ...> <input type="hidden" name="SAMLResponse" value="response" /> <input type="hidden" name="RelayState" value="token" /> ... <input type="submit" value="Submit" /> </form> The value of the RelayState parameter has been preserved from step 3. The value of the SAMLResponse parameter is the base64 encoding of the following <samlp:Response> element: <samlp:Response xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol" ID="identifier_2" InResponseTo="identifier_1" Version="2.0" IssueInstant="2004-12-05T09:22:05Z" Destination="https://sp.org/SAML2/SSO/POST"> <saml:Issuer>https://idp.org/SAML2</saml:Issuer> <!-- a POSTed response MUST be signed --> <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">...</ds:Signature> <samlp:Status> <samlp:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success"/> </samlp:Status> <saml:Assertion xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" ID="identifier_3" Version="2.0" IssueInstant="2004-12-05T09:22:05Z"> <saml:Issuer>https://idp.org/SAML2</saml:Issuer> <!-- a Subject element is required --> <saml:Subject> <saml:NameID Format="urn:oasis:names:tc:SAML:2.0:nameid-format:transient"> 3f7b3dcf-1674-4ecd-92c8-1544f346baf8 </saml:NameID> <saml:SubjectConfirmation Method="urn:oasis:names:tc:SAML:2.0:cm:bearer"> <saml:SubjectConfirmationData InResponseTo="identifier_1" Recipient="https://sp.org/SAML2/SSO/POST" NotOnOrAfter="2004-12-05T09:27:05Z"/> </saml:SubjectConfirmation> </saml:Subject> <saml:Conditions NotBefore="2004-12-05T09:17:05Z" NotOnOrAfter="2004-12-05T09:27:05Z"> <saml:AudienceRestriction> <saml:Audience>https://sp.org/SAML2</saml:Audience> </saml:AudienceRestriction> </saml:Conditions> <saml:AuthnStatement AuthnInstant="2004-12-05T09:22:00Z" SessionIndex="identifier_3"> <saml:AuthnContext> <saml:AuthnContextClassRef> urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport </saml:AuthnContextClassRef> </saml:AuthnContext> </saml:AuthnStatement> </saml:Assertion> </samlp:Response> 5) Request the Assertion Consumer Service at the SP The client issues a POST request to the assertion consumer service at the service provider. 6) Redirect to the target resource The assertion consumer service processes the response, creates a security context at the service provider and redirects the client to the target resource. 7) Request the target resource at the SP again The client requests the target resource at the service provider (again): https://sp.org/myresource 8) Respond with requested resource Since a security context exists, the service provider returns the resource to the client.
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