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Content for  TS 33.434  Word version:  16.0.0

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5  ProceduresWord‑p. 9

5.1  Security for the SEAL interfaces

5.1.1  Security for the Application plane interfaces

5.1.1.1  SEAL-X1

As defined in TS 23.434, the SEAL-X1 reference point, exists between the key management server and the group management server and uses HTTP-1 as defined in TS 23.434 for the transport and routing of security related information to the group management server. The SEAL-X1 shall be protected using HTTPS as defined in [3], [4] and [5]. The profile for TLS implementation and usage shall follow the provisions given in TS 33.310, annex E.
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5.1.1.2  SEAL-X2

The SEAL-X2 reference point enables the group management server to interact with the location management server as defined in TS 23.434. The SEAL-X2 shall be protected using HTTPS as defined in [3], [4] and [5]. The profile for TLS implementation and usage shall follow the provisions given in TS 33.310, annex E.

5.1.1.3  IM-UU

IM-UU reference point is used between the identity management client and the identity management server. The IM-UU between the Identity Management client and the Identity management server shall be protected using HTTPS as defined in [3], [4] and [5]. The profile for TLS implementation and usage shall follow the provisions given in TS 33.310, annex E.

5.1.1.4  KM-UU and KM-S

The KM-UU and the KM-S are direct HTTP connections between the Key Management Server and Key Management Client and shall be protected using HTTP over TLS as defined in [3], [4] and [5]. The profile for TLS implementation and usage shall follow the provisions given in TS 33.310, annex E.

5.1.1.5  SEAL-UU

A SEAL client interacts with a SEAL server over the generic SEAL-UU reference point as defined in TS 23.434. The protection of this interface shall be supported according to NDS/IP as specified in TS 33.210.

5.1.1.6  VAL-UU

The VAL client interacts with VAL server over VAL-UU reference point as defined in TS 23.434. The protection of this interface shall be supported according to NDS/IP as specified in TS 33.210.

5.1.1.7  SEAL-C

The VAL client interacts with a SEAL client over the SEAL-C reference point as defined in TS 23.434. This reference point resides fully within the UE and therefore, security of this interface is left to the manufacturer and is out of scope for the present document.

5.1.1.8  SEAL-S

The VAL server interacts with SEAL server over SEAL-S reference point as defined in TS 23.434. The protection of this interface shall be supported according to NDS/IP as specified in TS 33.210.

5.1.1.9  SEAL-EWord‑p. 10
A SEAL server interacts with another SEAL server over SEAL-E reference point as defined in TS 23.434. The protection of this interface shall be supported according to NDS/IP as specified in TS 33.210.

5.1.2  Security for the Signalling control plane interfaces

5.1.2.1  Security for HTTP interfaces

In order to authenticate the HTTP-1 reference point, authentication mechanisms shall be performed between the HTTP client and VAL UE using either certificate based authentication or pre-shared key based authentication. Certificate based authentication shall follow in annex B of TS 33.222, and the profiles given in TS 33.310. The usage of pre-shared key based ciphersuites is specified in the TLS profile given in TS 33.310, annex E.
The HTTP-1 reference point exists between the VAL UE and the HTTP proxy. The HTTP-2 exists between the HTTP proxy and HTTP server. The HTTP-3 reference point exists between the HTTP proxies in different networks. The HTTP interfaces shall be protected using TLS. The profile for TLS implementation and usage shall follow the provisions given in TS 33.310, annex E.
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5.1.3  Security for the network domain interfaces

A VAL UE shall perform the authentication and security mechanisms as specified in TS 33.501 for 5G network access security.
To ensure security of the interfaces between network entities within a trusted domain and between trusted domains, TS 33.210 shall be applied to secure signalling messages on the reference points unless specified otherwise. SEG as specified in TS 33.210 may be used in the trusted domain to terminate the IPsec tunnel.
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5.2  User authentication and authorization

5.2.1  VAL user authentication

Figure 5.2.3-1 shows the Identity Management functional model which consists of the SEAL Identity Management Server (SIM-S) and SEAL Identity Management Client (SIM-C) of the UE. The IM-UU reference point between the SIM-S and SIM-C shall provide the interface for user authentication and shall support OpenID Connect 1.0 [5] and OAuth 2.0 [9], [10] to obtain an access token for the VAL UE.
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5.2.2  SEAL service authorization

SEAL Service Authorization procedure shall validate the VAL user to access authorized VAL services. In order to gain access to VAL services, the SEAL client shall present an access token to the SEAL server for each service of interest. If the access token is valid, then the UE shall be granted to use the service.

5.2.3  Identity management functional model

The SEAL Identity Management Server (SIM-S) and the SEAL Identity Management Client (SIM-C) provide the endpoints for VAL user authentication as shown in the SEAL Identity Management functional model in figure 5.2.3-1.
The reference point IM-UU utilizes Uu reference point as described in TS 23.401 and TS 23.501. IM-UU shall support OpenID Connect 1.0 [5] and OAuth 2.0 [9] for VAL user authentication.
[not reproduced yet]
Figure 5.2.3-1: Functional model for SEAL Identity Management
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In order to support VAL user authentication, the SIM-S shall be provisioned with the VAL user ID and VAL service IDs (usage of VAL user ID and VAL service ID is described in clause 7 of TS 23.434). A mapping between the VAL user ID and VAL service ID(s) shall be created and maintained in the SIM-S. When a VAL user wishes to authenticate for the VAL services, the VAL user ID and credentials are provided via the UE Identity management client to the SIM-S as per OpenID Connect 1.0 [5]. The SIM-S receives and shall verify the VAL user ID and credentials. If verification is successful, then the SIM-S returns an ID token, refresh token and access token to the UE Identity management client. The SIM-C shall learn the user's VAL service ID(s) from the ID token. Table A shows the SEAL specific tokens and their usage.
Token Type
Consumer of the Token
Description

ID token
VAL UE client(s)
Contains the VAL service ID for at least one authorized VAL service.
Access token
SKM-S, SEAL service server(s)
Short-lived token (definable in the SIM-S) that conveys the UE's identity. This token contains the VAL service ID for at least one authorized service.
Refresh token
SIM-S (Authorization Server)
Allows VAL UE to obtain a new access token without forcing user to log in again.

To support the VAL service identity functional model, the VAL service ID(s):
  • Shall be provisioned into the SEAL Identity management database and mapped to VAL UE IDs.
  • Shall be provisioned into the SEAL Key management server (S-KMS) and mapped to UE specific key material.
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5.2.4  Authentication frameworkWord‑p. 11
Figure 5.2.4-1 describes the VAL Authentication Framework using the OpenID Connect protocol. It describes the steps by which a VAL UE authenticates to the SIM-S, resulting in a set of credentials delivered to the UE uniquely identifying the VAL service ID(s). The authentication framework supports extensible user authentication solutions based on the VAL service provider policy (shown as step 3). User authentication methods in support of step 3 (e.g. biometrics, secureID, etc.) are possible but not defined here.
[not reproduced yet]
Figure 5.2.4-1: OpenID Connect (OIDC) flow supporting VAL user authentication
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Step 1.
VAL UE establishes a secure tunnel with the SIM-S.
Step 2.
VAL UE sends an OpenID Connect Authentication Request to the SIM-S. The request may contain an indication of authentication methods supported by the UE.
Step 3.
User Authentication is performed between VAL UE and the SIM-S.
Step 4.
SIM-S sends an OpenID Connect Authentication Response to the UE containing an authorization code.
Step 5.
UE sends an OpenID Connect Token Request to the SIM-S, passing the authorization code.
Step 6.
SIM-S sends an OpenID Connect Token Response to the UE containing an ID token and an access token (each which uniquely identify the user of the VAL service). The ID token is consumed by the UE to personalize the VAL client for the VAL user, and the access token is used by the UE to communicate and authorize the identity of the VAL user to the VAL server(s) and the VAL services.
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5.2.5  Authorization frameworkWord‑p. 12
Authorization framework is shown in figure 5.2.5-1. A secure HTTP tunnel using HTTPS between VAL UE and VAL server shall be established before SEAL service authorization. Subsequent SEAL service authorization messaging make use of this tunnel. The service clients in the VAL UE present the access tokens to the SEAL service server over HTTP. The SEAL service server authorizes the user for the requested services on if the access token is valid. The procedures may be repeated as necessary to obtain additional SEAL user authorizations.
[not reproduced yet]
Figure 5.2.5-1: VAL User Service Authorization
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After the VAL UE establishing a secure connection with the VAL server, the VAL UE sends an HTTP message containing the access token to the VAL server where service authorization is requested. The VAL server receives the message, validates the access token. If the access token is valid, The VAL server positively acknowledges the request. The VAL server may provide service related information to the VAL UE at this time.

5.3  SEAL key management procedureWord‑p. 13

5.3.1  General

To enable security for SEAL services, a SEAL KM client (located in either a SEAL UE or VAL server) may request key material applicable to a particular SEAL service, VAL client or user.
Prior to making a key management request to the SEAL KMS (SKM-S), the VAL client or VAL user shall be authenticated by the SEAL identity management service (clause 5.2). In addition, secure connections shall be established between the SEAL client and the SKM-S (reference point KM-UU) and the VAL server and the SKM-S (reference point KM-S) prior to any associated key management requests.
As a result of the SEAL identity management authentication procedure, an access token scoped for key management services is provisioned to the SEAL UE. This access token is provided with each and every key management request to the SKM-S.
A VAL server is provisioned with an access token scoped for SEAL key management services and is provided with each and every key management request to the SKM-S. The method for provisioning this access token into the VAL server is out of scope of the present document.
Figure 5.3.1-1 shows the SEAL key management procedure. A SKM client may send a SEAL KM Request message to the SKM-S. The SKM-S validates and processes the request and responds with a SEAL KM Response message. The response contains key management material specific to the SEAL service or the VAL server request, or alternatively, an error code if the SKM-S encounters a failure condition.
[not reproduced yet]
Figure 5.3.1-1: SEAL key management procedure
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The procedure in figure 5.3.1-1 is described here:
Step 1.
The SKM-C establishes a direct HTTPS connection to the SKM-S. Steps 2 and 3 are within this secure connection.
Step 2.
The SKM-C sends a SEAL KM Request message to the SKM-S. The request contains the authorization credentials obtained during authentication and message content specified in clause 5.3.2.
Step 3.
The SKM-S authorizes the request and if valid, sends a SEAL KM Response message containing the requested key material (or error code) as specified in clause 5.3.3.
As a successful result of this procedure, the VAL UE or VAL Server has securely obtained service specific key material for use within the VAL system.
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5.3.2  SEAL KM Request messageWord‑p. 14
A SKM-C may send a SEAL KM Request message to the SKM-S. This request shall be protected (via the HTTPS tunnel) and shall contain the access token acquired during the SEAL identity management authentication procedure (clause 5.2).
The content of the SEAL KM Request is shown in table 5.3.2-1.
Name
Description

Version
The version number of the SEAL key management request (0.0.0).
SKmsUri
The URI of the SKM-S to which the request is sent.
ServiceID
A string representing the VAL service/application related to the VAL client request.
ClientID
(Optional) A string representing the client. See note.
DeviceID
(Optional) A string representing the device. See note.
UserID
(Optional) A string representing the user. See note.
Date/Time
The Date and Time of the request. This number represents the number of seconds from 1970-01-01T0:0:0Z as measured in UTC.


The identities listed in table 5.3.2-1 map to SEAL identities defined in TS 23.434. Namely, the ServiceID maps to the VAL service identity (VAL service ID), the ClientID maps to the VAL client, the DeviceID maps to the VAL UE identity (VAL UE ID), and the UserID maps to the VAL user identity (VAL user ID).
Upon receipt of a SEAL KM Request message, the SKM-S shall verify that:
  • the access token is valid;
  • the signature is valid;
  • the SKmsUri is the SKM-S URI of the target SEAL KMS; and
  • the Date/Time is within a recent time window (e.g. 5 seconds).
If valid, the request is accepted and processed by the SKM-S. Any combination of ClientID, DeviceID, ServiceID and UserID may be present in the SEAL KM Request message. This combination may be used by the KMS to identify a specific key material record. Each key management record may be unique to a VAL application or VAL service. The format and content of a key management record is defined and securely provisioned into the SEAL KMS by the VAL application or VAL service owner/operator. The method used to provision the VAL service or VAL application key material into the KMS is out of scope for the present document. The method used to organize, manage, and maintain VAL service or VAL application key material within the KMS is out of scope of the present document.
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5.3.3  SEAL KM Response message

The SEAL KM Response message is sent to the SKM-C in response to a SEAL KM Request message.
A successful SEAL key management procedure results in a SEAL KM Response message which typically includes a payload containing key management information uniquely applicable to the requested service, client or user. If an error occurs, an error code may be returned in the SEAL KM Response message.
The SEAL KM Response message shall be protected in transit via the HTTPS tunnel. The Payload within a SEAL KM Response message may be protected end-to-end between the SKM-C and SKM-S depending on the applicability of the underlying VAL service making the request. The method for securing a Payload end-to-end between the SKM-C and the SKM-S is outside the scope of the present document. The key material contents provided in a Payload are defined by the underlying VAL service and are outside the scope of the present document.
The content of a SEAL KM Response message is shown in table 5.3.3-1.
Name
Description

UserUri
URI of the user for which the response is intended.
SKmsUri
The URI of the SKM-S sending the response.
ServiceID
A string representing the VAL service/application related to the VAL client request. This is the same field as received in the SEAL KM Request message.
SKmsID
(Optional) The ID of the SKM-S providing the response message.
ClientID
(Optional) A string representing the client (see note)
DeviceID
(Optional) A string representing the device (see note)
UserID
(Optional) A string representing the user. (see note)
Date/Time
The Date and Time of the response. This number represents the number of seconds from 1970-01-01T0:0:0Z as measured in UTC.
ErrorCode
(Optional) Reason code indicating the failure of the requested action. If not present, the key management request is assumed to be successful.
Payload
(Optional) Key management payload specific to the VAL user, client or application. This field may not be present if 1) an error occurs or 2) if the request does not require a payload.


The identities listed in table 5.3.3-1 are described in clause 5.3.2.
The selection of the key material returned in the Payload of a SEAL KM Response message is determined by the ServiceID and (optionally) the ClientID, DeviceID or UserID. The combination of the ServiceID with the ClientID, DeviceID or UserID allows the VAL service to request a more specific set of key material.
For example, if a ClientID is included in the SEAL KM Request message, the KMS may return a Payload that contains a set of client specific key material applicable to the ClientID within the requesting VAL service (ServiceID). If the DeviceID is included, the KMS may return a Payload that contains device specific key material applicable to the DeviceID within the requesting VAL service (ServiceID). If the UserID is included, the KMS may return a Payload that contains user specific key material applicable to that UserID within the requesting VAL service (ServiceID).
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5.4  Security procedures for interconnectionWord‑p. 15
Interconnection between a primary VAL system and a partner VAL system is specified in TS 23.434.
A VAL client shall perform user authorization only to VAL servers within their own VAL system. When communication is required by a VAL client from another interconnected VAL system, user authorization takes place in the serving VAL system and follows the VAL user service authorization procedures as defined in clause 5.2.
VAL systems should protect themselves at the system border from external attackers.
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