3.3 Interaction with X.509 Certificate Enrollment Policy
This section describes the fourth phase in MDE device enrollment: interacting with the X.509 Certificate Enrollment Policy Protocol [MS-XCEP] to obtain the certificate policies. The following diagram highlights this phase.
Figure 7: MDE device enrollment: getting the certificate policies
The X.509 Certificate Enrollment Policy Protocol [MS-XCEP] enables a client to request certificate enrollment policies from a server. The communication is initiated by the enrollment client request to the server for the certificate enrollment policies. The server authenticates the client, validates the request, and returns a response with a collection of certificate enrollment policy objects. As described in section 3.2, the enrollment client uses the certificate enrollment policies to complete the enrollment process [MS-WSTEP]. MDE uses the policies to allow the ES to specify the hash algorithm and key length as described in the following section.
MDE implements the authentication provisions in WS-Security 2004 [WSS] to enable the ES [MS-XCEP] to authenticate the GetPolicies requestor [MS-XCEP]. This section defines the schema used to express the credential descriptor for the credential type. The security token credential is provided in a request message using the <wsse:BinarySecurityToken> element [WSS]. The security token is retrieved as described in section 3.2. The authentication information is as follows:
wsse:Security: MDE implements the <wsse:Security> element defined in [WSS] section 5. The <wsse:Security> element MUST be a child of the <s:Header> element (see [MS-XCEP] section 4).
wsse:BinarySecurityToken: MDE implements the <wsse:BinarySecurityToken> element defined in [WSS] section 6.3. The <wsse:BinarySecurityToken> element MUST be included as a child of the <wsse:Security> element in the SOAP header.
As was described in section 3.2, inclusion of the <wsse:BinarySecurityToken> element is opaque to the enrollment client and the client does not interpret the string and inclusion of the element is agreed upon by the STS (as identified in the DS <AuthenticationServiceUrl> element of <DiscoveryResponse> (section 18.104.22.168.3.2)) and the ES.
The <wsse:BinarySecurityToken> element contains a base64-encoded string. The enrollment client uses the security token received from the STS and base64-encodes the token to populate the <wsse:BinarySecurityToken> element.
<wsse:BinarySecurityToken> ValueType attribute MUST be
<wsse:BinarySecurityToken> EncodingType attribute MUST be