@actual-app/sync-server's missing authorization on GET /secret/:name allows non-admin OpenID users to enumerate admin-configured bank-sync secrets

Summary

In @actual-app/sync-server, the GET /secret/:name endpoint (app-secrets.js:53) checks only that the caller has a valid session — it does not verify the caller is an admin. The sibling POST /secret/ handler does enforce an admin check in OpenID mode, exposing an authorization asymmetry. Any authenticated non-admin (BASIC) user in OpenID multi-user deployments can probe the secrets store and learn which admin-managed bank-sync integrations have been configured (existence, not values). This includes integration credentials that are not otherwise observable to non-admins, such as simplefin_accessKey, pluggyai_clientSecret, pluggyai_itemIds, and the gocardless_* secrets.

Details

packages/sync-server/src/app-secrets.js mounts validateSessionMiddleware at the router level (line 15), so all handlers inherit only "must be authenticated." The POST handler then explicitly upgrades to an admin check when the active auth method is openid:

// app-secrets.js:17-46
app.post('/', async (req, res) => {
  // ... look up active auth method ...
  if (method === 'openid') {
    const canSaveSecrets = isAdmin(res.locals.user_id);
    if (!canSaveSecrets) {
      res.status(403).send({
        status: 'error',
        reason: 'not-admin',
        details: 'You have to be admin to set secrets',
      });
      return;
    }
  }
  secretsService.set(name, value);
  // ...
});

The sibling GET handler skips both the method check and the admin check entirely:

// app-secrets.js:53-61
app.get('/:name', async (req, res) => {
  const name = req.params.name;
  const keyExists = secretsService.exists(name);
  if (keyExists) {
    res.sendStatus(204);
  } else {
    res.status(404).send('key not found');
  }
});

The intent — visible from the POST handler's "You have to be admin to set secrets" — is that this store holds admin-managed credentials. The valid secret names enumerated in services/secrets-service.js (SecretName) are: gocardless_secretId, gocardless_secretKey, simplefin_token, simplefin_accessKey, pluggyai_clientId, pluggyai_clientSecret, pluggyai_itemIds.

In OpenID mode, BASIC users obtain valid sessions through packages/sync-server/src/accounts/openid.ts:264-274 — either auto-created (userCreationMode=login) or pre-provisioned by the admin (userCreationMode=manual). With that BASIC session token they can hit GET /secret/:name and distinguish 204 (configured) from 404 (missing), enumerating each admin-managed secret name. Some signals (simplefin_token existence, pluggyai_clientId existence) are already coarsely observable via the unauthenticated bank-sync status endpoints (app-simplefin.js:18, app-pluggyai.js:18); the rest (simplefin_accessKey, pluggyai_clientSecret, pluggyai_itemIds, both gocardless_* secrets) are not otherwise probeable.

This is structurally identical to the previously reported missing-admin-check on GET /admin/users/ (app-admin.js:28): a POST sibling enforces admin authorization while the GET sibling omits it.

PoC

Pre-requisites:

• Server is configured for OpenID multi-user mode (ACTUAL_OPENID_ENFORCE=true or auth method is openid).
• An admin has configured one or more bank-sync integrations.
• The attacker is any authenticated BASIC user (auto-created via userCreationMode=login, or admin-provisioned in the default manual mode).

Step 1 — capture a BASIC user's session token in $TOKEN (standard OpenID login flow, no admin role required).

Step 2 — probe each admin-managed secret name:

for name in gocardless_secretId gocardless_secretKey \
            simplefin_token simplefin_accessKey \
            pluggyai_clientId pluggyai_clientSecret pluggyai_itemIds; do
  status=$(curl -s -o /dev/null -w '%{http_code}' \
           -H "X-ACTUAL-TOKEN: $TOKEN" \
           https://actual.example.com/secret/$name)
  echo "$name -> $status"   # 204 = configured, 404 = missing
done

Step 3 — confirm the asymmetry by attempting to write a secret (correctly rejected for non-admins):

curl -s -H "X-ACTUAL-TOKEN: $TOKEN" \
     -H 'Content-Type: application/json' \
     -d '{"name":"pluggyai_itemIds","value":"x"}' \
     https://actual.example.com/secret/
# {"status":"error","reason":"not-admin","details":"You have to be admin to set secrets"}

The POST returns 403 not-admin; the GET returns 204/404 unauthenticated-against-role.

Impact

• A non-admin authenticated user in OpenID multi-user mode can enumerate which admin-managed bank-sync integrations the deployment uses.
• This reveals whether GoCardless, SimpleFIN, and/or Pluggy AI are configured, and which auxiliary credentials the admin has set (e.g. simplefin_accessKey, pluggyai_clientSecret, pluggyai_itemIds) — none of which are otherwise observable to non-admins.
• The disclosure is existence-only; secret values are not returned. Impact is limited to recon useful for targeted follow-on attacks (e.g. credential phishing, picking which integration to attack on a separate vulnerability).
• No integrity or availability impact.

Recommended Fix

Mirror the POST handler's admin gate on the GET handler. Minimal patch in packages/sync-server/src/app-secrets.js:

app.get('/:name', async (req, res) => {
  let method;
  try {
    const result = getAccountDb().first(
      'SELECT method FROM auth WHERE active = 1',
    );
    method = result?.method;
  } catch (error) {
    console.error('Failed to fetch auth method:', error);
    return res.status(500).send({
      status: 'error',
      reason: 'database-error',
      details: 'Failed to validate authentication method',
    });
  }

  if (method === 'openid' && !isAdmin(res.locals.user_id)) {
    return res.status(403).send({
      status: 'error',
      reason: 'not-admin',
      details: 'You have to be admin to read secret status',
    });
  }

  const name = req.params.name;
  const keyExists = secretsService.exists(name);
  if (keyExists) {
    res.sendStatus(204);
  } else {
    res.status(404).send('key not found');
  }
});

Consider factoring the method-lookup + admin-check into a shared helper used by both POST and GET to prevent the same asymmetry from recurring. Also consider restricting :name to the SecretName enum so unrelated probing is rejected up front.