Hardening: API request handling, random IDs, and plugin loading (#7906)

* Hardening: API request handling, token generation, and plugin loading

- pad_utils.randomString: generate the random IDs via crypto.getRandomValues
  (CSPRNG) instead of Math.random.
- OAuth2Provider: constant-time password comparison and a uniform failure delay
  on the OIDC interaction login; own-property user lookup.
- API.appendChatMessage: require the pad to already exist (getPadSafe),
  consistent with the other content API methods.
- RestAPI /api/2: forward only the authorization header rather than merging all
  request headers into the API field set.
- LinkInstaller: validate plugin dependency names before building filesystem
  paths from them.
- admin file server: return a generic error message and log details server-side.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Address review: timingSafeEqual on raw bytes; align /api/2 auth fallback

- OAuth2Provider.constantTimeEquals: compare raw UTF-8 bytes with
  crypto.timingSafeEqual instead of hashing them first. Resolves the CodeQL
  "password hash with insufficient computational effort" alert while keeping a
  content-independent comparison (length difference is covered by the uniform
  failure delay).
- RestAPI /api/2: fall back to the authorization header whenever the field is
  falsy (not only null), matching the openapi.ts handler so the two routers
  authenticate identically (Qodo).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* appendChatMessage: throw explicit error instead of getPadSafe (review)

Per review: replace the getPadSafe(padID, true) existence check with an
explicit `throw new CustomError('padID does not exist', 'apierror')` so chat
messages can't create pads, without fetching the pad.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/node/db/API.ts

@@ -414,7 +414,13 @@ exports.appendChatMessage = async (padID: string, text: string|object, authorID:
     time = Date.now();
   }
 
-  // @TODO - missing getPadSafe() call ?
+  // Reject messages addressed to a pad that doesn't exist. Without this check
+  // the downstream padManager.getPad() would create the pad on demand with
+  // default content, so the documented {code:1,"padID does not exist"} result
+  // would never be returned.
+  if (!await padManager.doesPadExists(padID)) {
+    throw new CustomError('padID does not exist', 'apierror');
+  }
 
   // save chat message to database and send message to all connected clients
   await padMessageHandler.sendChatMessageToPadClients(new ChatMessage(text, authorID, time), padID);

src/node/handler/RestAPI.ts

@@ -1471,7 +1471,15 @@ export const expressCreateServer = async (hookName: string, {app}: ArgsExpressTy
       }
     }
 
-    const fields = Object.assign({}, headers, params, query, formData);
+    // Merge with clear precedence: body > query > path params, matching the
+    // openapi.ts handler. Forward only the authorization header explicitly
+    // instead of merging all request headers into the field set.
+    const fields = Object.assign({}, params, query, formData);
+    if (headers && headers.authorization) {
+      // Match the openapi.ts handler: fall back to the header whenever the
+      // field value is falsy (absent or empty), not only when it is null.
+      fields.authorization = fields.authorization || headers.authorization;
+    }
 
     if (mapping.has(method) && pathToFunction in mapping.get(method)!) {
       const {apiVersion, functionName} = mapping.get(method)![pathToFunction]!

src/node/hooks/express/admin.ts

@@ -66,8 +66,11 @@ exports.expressCreateServer = (hookName: string, args: ArgsExpressType, cb: Func
       // read file from file system
       fs.readFile(pathname, function (err, data) {
         if (err) {
+          // Log the detailed error server-side; return a generic message to the
+          // client rather than echoing the filesystem error.
+          console.error(`admin: error reading ${pathname}: ${err}`);
           res.statusCode = 500;
-          res.end(`Error getting the file: ${err}.`);
+          res.end('Error getting the file.');
         } else {
           let dataToSend:Buffer|string = data
           // if the file is found, set Content-type and send data

src/node/security/OAuth2Provider.ts

@@ -9,6 +9,21 @@ import express from 'express';
 import {format} from 'url'
 import {ParsedUrlQuery} from "node:querystring";
 import {MapArrayType} from "../types/MapType";
+import crypto from "node:crypto";
+
+// Small fixed delay applied to every failed interactive login, mirroring
+// webaccess.authnFailureDelayMs, so failures take a consistent amount of time.
+const OAUTH_LOGIN_FAILURE_DELAY_MS = 1000;
+
+// Constant-time string comparison using crypto.timingSafeEqual. Unequal-length
+// inputs short-circuit to false (that length difference is covered by the
+// uniform failure delay below). The raw bytes are compared directly — the
+// values are not hashed/stored, this only avoids a content-dependent compare.
+const constantTimeEquals = (a: string, b: string): boolean => {
+    const ba = Buffer.from(String(a), 'utf8');
+    const bb = Buffer.from(String(b), 'utf8');
+    return ba.length === bb.length && crypto.timingSafeEqual(ba, bb);
+};
 
 const configuration: Configuration = {
     scopes: ['openid', 'profile', 'email'],
@@ -171,21 +186,28 @@ export const expressCreateServer = async (hookName: string, args: ArgsExpressTyp
                             admin: boolean;
                         }
                     }
-                    const usersArray1 = Object.keys(users).map((username) => ({
-                        username,
-                        ...users[username]
-                    }));
-                    const account = usersArray1.find((user) => user.username === login as unknown as string && user.password === password as unknown as string);
+                    const loginStr = String(login ?? '');
+                    const passwordStr = String(password ?? '');
+                    // Look up by own property only, then compare the password
+                    // with constantTimeEquals.
+                    const user = Object.prototype.hasOwnProperty.call(users, loginStr)
+                        ? users[loginStr] : undefined;
+                    const passwordOk = user != null &&
+                        constantTimeEquals(passwordStr, String(user.password));
+                    const account = passwordOk ? {username: loginStr, ...user} : undefined;
                     if (!account) {
+                        // Apply the failure delay and stop here (explicit break)
+                        // so a failed login never reaches the grant branch.
+                        await new Promise((resolve) =>
+                            setTimeout(resolve, OAUTH_LOGIN_FAILURE_DELAY_MS));
                         res.setHeader('Content-Type', 'application/json');
                         res.end(JSON.stringify({error: "Invalid login"}));
+                        break;
                     }
 
-                    if (account) {
-                        await oidc.interactionFinished(req, res, {
-                            login: {accountId: account.username}
-                        }, {mergeWithLastSubmission: false});
-                    }
+                    await oidc.interactionFinished(req, res, {
+                        login: {accountId: account.username}
+                    }, {mergeWithLastSubmission: false});
                     break;
                 }
                 case 'consent': {