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<html><head><meta http-equiv="content-type" content="text/html; charset=us-ascii"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">Hi Mike,<br>
<div><br><blockquote type="cite"><div>On Nov 9, 2022, at 7:39 AM, Michael Sweet <msweet@msweet.org> wrote:</div><br class="Apple-interchange-newline"><div>CAUTION: External Email<br><br><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(127, 127, 127, 1.0);"><b>From: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;">Michael Sweet <msweet@msweet.org><br></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(127, 127, 127, 1.0);"><b>Subject: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;"><b>Re: [IPP] Add "oauth-authorization-resource" attribute?</b><br></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(127, 127, 127, 1.0);"><b>Date: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;">November 9, 2022 at 7:39:14 AM MST<br></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(127, 127, 127, 1.0);"><b>To: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;">"Kennedy, Smith (Wireless & IPP Standards)" <smith.kennedy@hp.com><br></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif; color:rgba(127, 127, 127, 1.0);"><b>Cc: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;">PWG IPP Workgroup <ipp@pwg.org><br></span></div><br><br>Smith,<br><br><blockquote type="cite">On Nov 8, 2022, at 11:56 PM, Kennedy, Smith (Wireless & IPP Standards) <smith.kennedy@hp.com> wrote:<br>...<br>If an Authentication Service supports a certificate or some other more trustable artifact as a resource identifier, perhaps one provisioned to the printer at the time the printer is registered, that could improve the situation, right? I thought we discussed that at the August F2F.<br></blockquote><br>Yes, for authenticating the System/Printer/Proxy to the auth server - that's one of the things MS does for their Universal Print Service.<br><br>The point of the Client passing the printer-uri/system-uri when doing token exchange is to limit the potential exposure of credentials. The Client will have already validated the Printer's X.509 certificate when it connects to do a Get-Printer-Attributes, and then the authorization server can validate that the System/Printer/Proxy has registered *that* printer-uri/system-uri. That combined with the Client validating the oauth-authorization-server-uri value will minimize the likelihood of a breach.<br><br><blockquote type="cite">Regardless, I think that it would be better for the client to use the value provided by a purpose-defined but abstract attribute like "oauth-authorization-resource-id" instead of instructing or guiding clients to use "printer-uuid" or "printer-uri". The value held by "oauth-authorization-resource-id" could be a URI or a UUID (printer-uuid or some other UUID).<br></blockquote><br>There is no way to validate the value, so its use in securing the authorization token would be lost.<br><br>With the URI, the Client resolves the address, connects to the service, negotiates a secure connection via TLS, and is able to validate the server-side X.509 certificate against a trusted root CA (no self-signed certs if you are using OAuth!)<br></div></blockquote><div><br></div>Agree, but I don't think that eliminates the value that "oauth-authorization-resource-id" provides. The value held by "oauth-authorization-resource-id" could be whatever is needed to identify the resource to the Authentication Service. In some cases it may be "printer-uuid" or "printer-uri" or some unique value provisioned to the Printer by the Authentication Service during printer registration. Defining "oauth-authorization-resource-id" means we don't have to provide specific guidance as to what is provided in the OAuth 2.0 requests that require a resource ID to be specified as a parameter.</div><div><br></div><div>The Client is still free to compare the elements of "printer-uri" with the fields in the Printer's X.509 TLS certificate.</div><div><br></div></body></html>