fix(reality): make the REALITY target check usable on a private network (#6242)

* fix(reality): make the REALITY target check usable on a private network

The probe dials through netsafe.SSRFGuardedDialContext, so a fronting service
reachable only inside the deployment (a Docker service name, a LAN address)
always failed with "blocked private/internal address": the inbound itself
works, because the guard sits in the probe path only, so the panel reported a
red verdict on a healthy configuration. Instead of a panel-wide setting that
lifts the guard for good, the guard is now lifted per probe and only after the
operator confirms the local-network warning in a modal; the verdict keeps
privateTarget set, so a passing local check stays a warning rather than a
green success.

The probe also sent the target host as SNI. Clients dial the target but send a
name from serverNames, so a fronting proxy answered with its default
certificate — a Traefik front reached as "traefik" reported "certificate is
valid for <hash>.traefik.default, not traefik" on a deployment whose clients
get a valid chain. The panel now sends the first configured serverName as SNI
and the certificate is verified against it; empty serverNames keeps the old
fallback. The reported target stays the dialled address, so a passing check no
longer rewrites the target field with the SNI host.

The result panel reports what was actually seen: the SNI used, the certificate
subject/issuer and its expiry stay visible when the chain is untrusted (with
"Not trusted" appended) instead of being replaced by that verdict alone.
Certificate names are copied into the SNI field only when the chain verified —
the names on a proxy's default certificate would otherwise become the SNI of
the next check.

The bulk/CIDR scanner keeps the guard unconditionally: honouring the opt-in
there would turn it into an internal network scanner.

* fix(reality): recover from a stale SNI and report a refused address reliably

Review follow-up on the REALITY target check.

The probe sends the stored serverNames as SNI, and the panel only wrote names
back when the whole chain verified, so switching Target while the SNI field
still held the previous target's names failed every rescan: the new target's
real names came back from the probe but were discarded with the verdict. The
certificate is now checked in two steps — chain first, then the name — and a
trusted chain presented for other names is enough for the panel to offer those
names, so the next scan passes. Picking a row in the bulk scanner replaces the
names outright, since keeping the previous target's SNI leaves a REALITY config
that cannot work.

SSRFGuardedDialContext kept the refusal only in lastErr, so on a dual-stack
name a refused private address followed by a failing public one lost the
sentinel and the panel silently skipped the confirmation. The refusal is now
tracked separately and reported alongside the last dial error.

Honouring the opt-in is logged with the target and the resolved address, since
it bypasses the SSRF guard on an authenticated endpoint. The read-only SNI row
in the result is labelled "SNI used" so it no longer collides with the SNI
field below it, and the comment blocks are back within the 2-line limit.

---------

Co-authored-by: Claude <noreply@anthropic.com>

frontend/src/pages/api-docs/endpoints.ts

@@ -521,9 +521,12 @@ export const sections: readonly Section[] = [
       {
         method: 'POST',
         path: '/panel/api/server/scanRealityTarget',
-        summary: 'Run a live TLS 1.3 probe against a candidate REALITY target and return a feasibility verdict (TLS 1.3 + h2 + X25519 + trusted certificate) plus the certificate SAN DNS names.',
+        summary: 'Run a live TLS 1.3 probe against a candidate REALITY target and return a feasibility verdict (TLS 1.3 + h2 + X25519 + trusted certificate) plus the certificate SAN DNS names. A target on a private/loopback address is reported with privateTarget=true and probed only when allowPrivate is set.',
         params: [
           { name: 'target', in: 'body (form)', type: 'string', desc: 'Candidate target as host or host:port (default port 443), e.g. www.cloudflare.com:443.' },
+          { name: 'sni', in: 'body (form)', type: 'string', optional: true, desc: 'SNI the handshake sends and the certificate is verified against (the inbound serverNames). Defaults to the target host, which a fronting proxy answers with its default certificate.' },
+          { name: 'xver', in: 'body (form)', type: 'number', optional: true, desc: 'PROXY protocol version the target expects (matches the inbound xver). 0 = none.' },
+          { name: 'allowPrivate', in: 'body (form)', type: 'boolean', optional: true, desc: 'Probe a private/internal/loopback target (LAN, Docker service name). Default false (SSRF guard blocks it and the response sets privateTarget=true).' },
         ],
         body: 'target=www.cloudflare.com:443',
         responseSchema: 'RealityScanResult',