Allow TRMNL install_success to rebind uuid on an existing token

src/auth/trmnlAuth.ts

@@ -36,10 +36,12 @@ export const requireTrmnlAuth: RequestHandler = async (req: Request, res: Respon
   }
 
   // Strip 'Bearer ' and only hash token
+  // Bearer token is unique to user + plugin - the users `access_token`
+  // we must persist this token as it we'll use it to authenticate the screen generation requests from TRMNL
   const tokenHash = sha256(auth.slice(7).trim())
 
   if (!(await isKnownTokenHash(tokenHash))) {
-    logger.info(`[AUTH] Unrecognized TRMNL token hash - ${req.originalUrl}`)
+    logger.warn(`[AUTH] Unrecognized TRMNL token hash - ${req.originalUrl}`)
     logger.debug(tokenHash)
     res.status(401).json({ error: 'Unauthorized', message: 'Access Denied'})
     return
@@ -88,7 +90,9 @@ export const requireTrmnlUuidMatch: RequestHandler = async (req: Request, res: R
   }
 
   if (bound !== uuid) {
-    logger.warn(`[AUTH] token/uuid mismatch for ${tokenHash} - ${req.originalUrl}`)
+    logger.warn(
+      `[AUTH] token/uuid mismatch for ${tokenHash} - bound=${bound} presented=${uuid} - ${req.originalUrl}`
+    )
     res.status(401).json({ error: 'Unauthorized', message: 'Unauthorized access' })
     return
   }

src/utils/dbConnector.ts

@@ -79,6 +79,8 @@ export async function storeTrmnlToken(tokenHash: string) {
   ).run(tokenHash, Date.now())
 }
 
+// access tokens are sha256 hashed before storage in DB for security
+// this checks if we've seen this hash before
 export async function isKnownTokenHash(tokenHash: string): Promise<boolean> {
   const db = getDb()
   logger.debug('[ DB ] Check if we know this incoming token hash')
@@ -95,6 +97,7 @@ export async function isKnownTokenHash(tokenHash: string): Promise<boolean> {
   return !!row && row.revoked_at == null
 }
 
+// Update the last_seen_at timestamp for a given token hash
 export async function touchTrmnlToken(tokenHash: string) {
   const db = getDb()
   logger.info('[ DB ] Refreshing user token')
@@ -107,6 +110,7 @@ export async function touchTrmnlToken(tokenHash: string) {
   ).run(Date.now(), tokenHash)
 }
 
+// based on the access token (unique to user + plugin, hashed) get the user uuid that's bound to it, if any
 export function getUserUuidByTokenHash(tokenHash: string): string | null {
   const db = getDb()
   logger.info('[ DB ] Retrieving UUID for hash: ', tokenHash)
@@ -123,7 +127,8 @@ export function getUserUuidByTokenHash(tokenHash: string): string | null {
   return row?.user_uuid ?? null
 }
 
-// bind once: only set if currently null/empty
+// Holding a valid, recognized access token is the actual proof of identity here (see requireTrmnlAuth),
+// so a fresh install_success call is trusted to (re)bind the uuid rather than being locked to whatever was first recorded.
 export function bindUserUuidToToken(tokenHash: string, userUuid: string) {
   const db = getDb()
   logger.info(`[ DB ] Binding user to ${tokenHash}`)
@@ -132,11 +137,11 @@ export function bindUserUuidToToken(tokenHash: string, userUuid: string) {
     update trmnl_connections
     set user_uuid = ?
     where access_token_hash = ?
-      and (user_uuid is null or user_uuid = '')
   `
   ).run(userUuid, tokenHash)
 }
 
+// remove outdated hashed access tokens from the database (revoked or stale)
 export function pruneStaleTokens() {
   const db = getDb()
   const now = Date.now()