Pithos browser app plan: pithos.silentmode.st, sign-in only, remember allowed

app.pithos.sia would still be served from the shared navigate.st origin
outside Theseus, so the app gets its own name on silentmode.st.

DESIGN-web-app.md

@@ -1,6 +1,6 @@
 # Pithos in the browser (plan)
 
-Status: plan, 2026-10-05. Nothing built yet.
+Status: plan, 2026-10-05. Nothing built yet. Decided: `https://pithos.silentmode.st`, sign-in only, "Remember on this device" allowed.
 
 ## Goal
 
@@ -14,8 +14,15 @@ hands over to the local Pithos ("Open my Pithos", port 47621).
 
 ## Where it lives: its own origin
 
-**`https://s3.silentmode.st/app`**, served by the hosted gateway.
+**`https://pithos.silentmode.st`**: a vhost of its own that serves the app
+files and forwards `/hosted/v1/*`, `/api/*` and the S3 paths to the hosted
+gateway (127.0.0.1:8720), so the page and the API share one origin.
 
+- Not `app.pithos.sia` either: outside Theseus BNS names are paths of
+  navigate.st (and BNS folds subdomains into the parent name's folder), so
+  the origin would still be navigate.st. Per-name origins on navigate.st
+  (`<name>.navigate.st`, wildcard certificate) would fix that for every BNS
+  site; a separate project.
 - Not on `navigate.st/bns/pithos.sia/app`: every BNS site served through
   navigate.st shares the origin `navigate.st`, so any other `.sia`/`.bch` site
   could open the app's window (same origin) and read the keys out of it, or
@@ -25,7 +32,7 @@ hands over to the local Pithos ("Open my Pithos", port 47621).
 - `pithos.sia/app` keeps its meaning: in Theseus it is the full app (the
   add-on answers it); in any other browser the website's app-address hint
   gets a third button, "Open in the browser app", linking to
-  `https://s3.silentmode.st/app`.
+  `https://pithos.silentmode.st`.
 - Strict CSP (`default-src 'self'`, `connect-src 'self'`, no inline script,
   `frame-ancestors 'none'`), no third-party scripts, files served by the
   gateway from `Pithos/web/` (versioned with Pithos).
@@ -56,9 +63,10 @@ Two kinds of key, both loaded from a file (drag and drop or picker) or pasted:
    gateway.
 
 Keys live **in memory only** by default; closing the tab signs out.
-Optional "Remember on this device": the key file is wrapped with a
+"Remember on this device" (allowed): the key file is wrapped with a
 passphrase (PBKDF2-SHA256 600k + AES-GCM, as Save credentials… does) in
-IndexedDB on the gateway origin. Sign out wipes it and calls
+IndexedDB on the pithos.silentmode.st origin; the next visit asks for the
+passphrase only. Sign out wipes it and calls
 `DELETE` on the session.
 
 ## Crypto in the page
@@ -92,13 +100,18 @@ in `Pithos/web/lib/`, sharing test vectors with the Node versions.
 
 Later: the docked music player, offline cache, PWA install.
 
-## Gateway changes (Pithos/hosted)
+## Server changes
 
-- Serve `GET /app`, `/app/*` (static files, strict CSP, long cache with
-  versioned names), before the S3/auth routing.
-- Nothing else: same origin, so no CORS. The S3 path rules stay as they are
-  (owner keys raw-proxied to s3d; grant keys checked by `rules.js`).
-- Rate limits already in place for sign-in apply.
+- DNS `pithos.silentmode.st` → the VPS; certificate; an Angie vhost that
+  serves `Pithos/web/` at `/` (strict CSP, versioned file names, long cache)
+  and proxies `/hosted/v1/`, `/api/` and S3 requests to 127.0.0.1:8720.
+- The gateway must accept that Host for SigV4: the page signs requests for
+  host `pithos.silentmode.st`; owner keys go raw to s3d, which checks the
+  signature over the Host it receives, so the vhost passes `Host` through
+  unchanged and `publicUrl`-based checks (challenge message) need the second
+  name (the challenge text names the URL the client signed in at).
+- No CORS: same origin. Path rules unchanged (owner keys raw-proxied to s3d;
+  grant keys checked by `rules.js`). Sign-in rate limits apply.
 
 ## Phases
 
@@ -111,8 +124,8 @@ Later: the docked music player, offline cache, PWA install.
 
 ## Open questions
 
-- Is `s3.silentmode.st/app` the address, or a dedicated `pithos.silentmode.st`
-  (same design, another certificate and vhost)?
-- Should the browser app also sign up new accounts (BNS signature / invite),
-  or only sign in to accounts made in Pithos?
-- "Remember on this device": allow it, or always ask for the key file?
+- Decided 2026-10-05: `pithos.silentmode.st`; sign-in only (accounts are
+  made in Pithos); "Remember on this device" allowed (passphrase-wrapped).
+- Still open: does s3d accept SigV4 for a Host other than the one it was set
+  up with? (It checks the signature over whatever Host arrives, so it should;
+  verify in phase 2.)