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Maurice
d77f1c1758
POST /oauth/register refused every single-label private-use scheme, so an
MCP client registering workbuddy:// could not connect at all, while the
error it got back advertised "a private custom scheme" as supported.
The cause was two validators that had drifted apart, both of which run on
registration. The provider required a dot in the scheme name, which RFC
8252 section 7.1 only recommends and which protected nothing
(javascript.evil:// passed it). The service behind it had no
custom-scheme branch whatsoever and no [::1], which is what actually
answered the reporter's second symptom, and its localhost exemption was
not gated on http:. So javascript://localhost/%0aalert(1), blob:, about:,
ftp: and wss: were all accepted through the settings UI, and the consent
flow assigns the stored URI to window.location.href. Only the CSP stood
between that and a navigation. Both now decide through one policy in
oauth.helpers.ts.
Widening the scheme set means the deny-list has to carry its own weight:
it grows by the browser, extension and OS-handler schemes that were
previously blocked only as a side effect of the dot rule, including
ms-msdt (Follina) and the ms- namespace by prefix. intent: is denied,
because Chrome follows its embedded fallback URL, which turns it into an
open redirect the authorization server cannot inspect.
Fixing registration alone would have moved the reporter's [::1]:{port}
failure one step later: TREK matched redirect URIs byte for byte while
RFC 8252 section 7.3 frees the port for loopback, so a native client on
an OS-assigned port got a 302 to consent and then invalid_redirect_uri.
The matcher now relaxes the port, and only the port, for http loopback.
Stored URIs are never canonicalised, so the %3A round-trips untouched.
Note this tightens POST /api/oauth/clients for inputs it accepts today.
That is the security half of the change and applies at create time only,
so no already-registered client changes behaviour.
Closes #2227