Note 7 oauth bearer tokens can be used with

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NOTE 7: OAuth bearer tokens can be used with signalling protocols that supports the Authorization header defined in RFC 2617 [13], for example SIP and HTTP. 4. Validation of security token at eP-CSCF 4.1 General : An example realisation of this step is as follows: The eP-CSCF extracts the authorization token and validates it in some unspecified manner ensuring that only an authorized source can have generated the authorization token. If the authorization token is valid the eP-CSCF obtains the associated authorization information, including the IMPI and IMPU assigned to the user by the WWSF, the WWSF identity, and the authorization token scope. The eP-CSCF verifies that the scope includes the value "webrtc-ims-client-access-to-ims". NOTE 8: Under certain assumptions, the eP-CSCF can also verify that the IMPI, if it exists at all in the IMS, belongs to an IMS subscription in the pool of IMS subscriptions assigned to the WWSF.Such an assumption would be e.g. that the IMPIs from the pool of IMS subscriptions assigned to the WWSF have a special form, and the IMS provider does not assign IMPIs of this form to any other WWSF. However, the IMPU would not have to follow the same special format as the IMPI. If the validation fails in some respect, the eP-CSCF declines the register request, closes the web socket and aborts the procedure. Example of OAuth 2.0 : Identical to 4.1. NOTE 9: The value "webrtc-ims-client-access-to-ims" is just a placeholder. The final syntax will be defined in the stage 3 specification. From the beginning of step 5 until the end of step 7, the text in the present subclause X.4.2.3 is normative. 5. REGISTER request (eP-CSCF to S-CSCF) 5.1 General : The eP-CSCF proceeds if the previous step has provided it with IMPI, IMPU(s) of the user requesting registration, an assurance that the user is authorised to use this IMPI and IMPU, and an identity of the WWSF and WAF. Then, the eP-CSCF generates a TNA Authorization header and forwards the request to the S-CSCF (via the I-CSCF). The format of the TNA Authorization header is specified in TS 24.292, Clause 6.2 [15], and contains, among others, the IMPI assigned to the user, an integrity-protected directive set to auth-done, and an empty response directive. Example of OAuth 2.0 : Identical to 5.1. 5.2 Case of WAF located in third party domain : In this case, in addition to step 5.1, , if the eP-CSCF cannot not verify in step 4 that the IMPI, if it exists at all, belongs to an IMS subscription in the pool of IMS subscriptions assigned to the WWSF then the eP-CSCF includes the identity of the authorization entity. 6. Cx: S-CSCF Registration Notification 6.1 General : Based on the presence of the "integrity-protected" directive set to indicate that authentication has already been performed, the S-CSCF knows that the user’s authorization has already been validated by the Trusted Node. The S- 3GPP 3GPP TS 33.203 V12.67.0 (2014-0609) 142 Release 12
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CSCF informs the HSS that the user has been registered. Upon being requested by the S-CSCF, the HSS will also include the user profile in the response sent to the S-CSCF. For detailed message flows see TS 29.228 [16].
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