One read of a device's link: state::credentials, with the client's seal

Five places read the server address and token straight from sync_state:
sharing, autosync, sync_unlink, update's download token, and the ffi. Reading it
raw is how Android came to send its sealed token to the share routes (#5381).
state::credentials(conn, seal) now holds that read. With a seal it opens the token
(open_token), and without one (the desktop keeps it plain) it returns it as stored.
Every site calls it.

DRY pass #2, batch 1, F1 (#5372).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/ffi/src/lib.rs

@@ -753,14 +753,8 @@ impl Inkwell {
     /// it (`state::open_token`), so the app asks to sign in again.
     fn credentials(&self) -> Result<(String, String), CoreError> {
         let conn = self.db.conn().map_err(CoreError::store)?;
-        let current = state::read(&conn).map_err(CoreError::store)?;
-        let (Some(url), Some(stored)) = (current.server_url, current.device_token) else {
-            return Err(CoreError::NotLinked);
-        };
-        match state::open_token(&conn, &stored, &self.seal).map_err(CoreError::store)? {
-            Some(token) => Ok((url, token)),
-            None => Err(CoreError::NotLinked),
-        }
+        let link = state::credentials(&conn, Some(&self.seal)).map_err(CoreError::store)?;
+        link.ok_or(CoreError::NotLinked)
     }
 
     /// Persist a fresh link, adopting the server's retention window at the same time

core/src/sync/sharing.rs

@@ -6,10 +6,10 @@
 //! the server's answer so the card's chip changes at once rather than at the next
 //! sync (which brings the same value).
 //!
-//! The server address and token come from the CALLER, never from the store here.
-//! A stored token may be sealed (Android keeps it under a Keystore key, see
-//! `state::TokenSeal`), and only the caller holds the seal that opens it. Reading it
-//! here sent `sealed:…` as the bearer token, and every share call was refused (#5381).
+//! The server address and token come from the CALLER, read with
+//! `state::credentials` and the caller's seal. A stored token may be sealed
+//! (Android keeps it under a Keystore key), and reading it raw here sent `sealed:…`
+//! as the bearer token, so every share call was refused (#5381).
 
 use rusqlite::params;
 
@@ -22,17 +22,12 @@ use crate::local::Db;
 pub const NEEDS_SERVER: &str =
     "Sharing is between people on a server. Link this device to one in Sync to share notes.";
 
-/// The server address and token AS STORED, or [`NEEDS_SERVER`].
-///
-/// Only for a client that stores its token plain, as the desktop does. A client
-/// with a seal opens the token itself (`state::open_token`) and passes that.
+/// The link to share over, or [`NEEDS_SERVER`]. For a client that keeps its token
+/// plain, as the desktop does; one with a seal reads `state::credentials` itself.
 pub fn stored_link(db: &Db) -> Result<(String, String), String> {
     let conn = db.conn()?;
-    let link = state::read(&conn).map_err(|e| e.to_string())?;
-    match (link.server_url, link.device_token) {
-        (Some(url), Some(token)) => Ok((url, token)),
-        _ => Err(NEEDS_SERVER.to_string()),
-    }
+    let link = state::credentials(&conn, None).map_err(|e| e.to_string())?;
+    link.ok_or_else(|| NEEDS_SERVER.to_string())
 }
 
 /// Set the local note's `shared` flag from the server's list of its shares. Not a

core/src/sync/state.rs

@@ -175,6 +175,27 @@ pub fn open_token(
     Ok(Some(stored.to_string()))
 }
 
+/// The server address and the token to send it, or None when this device isn't
+/// linked. The ONE read of a link for a call to the server: every client goes
+/// through here, so none can send a token as stored when it is sealed (#5381).
+///
+/// With a `seal`, the stored token is opened ([`open_token`]); a client without one
+/// (the desktop keeps its token plain) passes None and gets it as stored.
+pub fn credentials(
+    conn: &Connection,
+    seal: Option<&dyn TokenSeal>,
+) -> rusqlite::Result<Option<(String, String)>> {
+    let link = read(conn)?;
+    let (Some(url), Some(stored)) = (link.server_url, link.device_token) else {
+        return Ok(None);
+    };
+    let token = match seal {
+        Some(seal) => open_token(conn, &stored, seal)?,
+        None => Some(stored),
+    };
+    Ok(token.map(|token| (url, token)))
+}
+
 /// Replace the stored token alone, leaving the server and cursor as they are.
 fn store_token(conn: &Connection, token: Option<&str>) -> rusqlite::Result<()> {
     conn.execute(

desktop/src-tauri/src/autosync.rs

@@ -176,8 +176,7 @@ fn backoff(failures: u32) -> Duration {
 /// The server URL and token, or None when this device isn't linked.
 fn credentials(db: &Db) -> Result<Option<(String, String)>, String> {
     let conn = db.conn()?;
-    let current = state::read(&conn).map_err(|e| e.to_string())?;
-    Ok(current.server_url.zip(current.device_token))
+    state::credentials(&conn, None).map_err(|e| e.to_string())
 }
 
 /// What is waiting to be sent, as [`push::pending_fingerprint`] sees it. A store

desktop/src-tauri/src/commands/sync.rs

@@ -136,8 +136,7 @@ pub async fn sync_unlink(db: State<'_, Db>) -> Result<UnlinkResult, String> {
     // the UI.
     let link = {
         let conn = db.conn()?;
-        let current = state::read(&conn).map_err(|e| e.to_string())?;
-        current.server_url.zip(current.device_token)
+        state::credentials(&conn, None).map_err(|e| e.to_string())?
     };
     let revoked = match &link {
         Some((base_url, token)) => client::revoke_self(base_url, token).await,

desktop/src-tauri/src/update.rs

@@ -343,13 +343,10 @@ fn read_source(db: &Db) -> Result<Source, String> {
 /// the link is the one credential this app already holds for it.
 fn token_for(db: &Db, base: &str) -> Result<Option<String>, String> {
     let conn = db.conn()?;
-    let link = state::read(&conn).map_err(|e| e.to_string())?;
-    let linked = link.server_url.as_deref().and_then(normalize_server);
-    if linked.as_deref() == Some(base) {
-        Ok(link.device_token)
-    } else {
-        Ok(None)
-    }
+    let Some((url, token)) = state::credentials(&conn, None).map_err(|e| e.to_string())? else {
+        return Ok(None);
+    };
+    Ok((normalize_server(&url).as_deref() == Some(base)).then_some(token))
 }
 
 /// An updater pointed at `source`, carrying `token` when there is one. The plugin