Delete redundant token2author DB save

See:
https://github.com/ether/etherpad-lite/pull/4012#issuecomment-686005563
https://github.com/ether/etherpad-lite/issues/4006

src/node/db/AuthorManager.js

@@ -77,17 +77,6 @@ exports.createAuthorIfNotExistsFor = async function(authorMapper, name)
   return author;
 };
 
-/**
- * Sets the token <> AuthorID relationship.
- * Discussion at https://github.com/ether/etherpad-lite/issues/4006
- * @param {String} token The token (generated by a client)
- * @param {String} authorID The authorID (returned by the Security Manager)
- */
-exports.setToken2Author = async function(token, authorID)
-{
-  await db.set("token2author:"+token, authorID);
-}
-
 /**
  * Returns the AuthorID for a mapper. We can map using a mapperkey,
  * so far this is token2author and mapper2author

src/node/db/SecurityManager.js

@@ -30,10 +30,12 @@ var authLogger = log4js.getLogger("auth");
  * This function controlls the access to a pad, it checks if the user can access a pad.
  * @param padID the pad the user wants to access
  * @param sessionCookie the session the user has (set via api)
- * @param token a random token representing the author, of the form
- *              t.randomstring_of_lenght_20. The random string is generated by
- *              the client.
+ * @param token A random token representing the author, of the form t.randomstring_of_length_20.
+ *              The random string is generated by the client.
  *              Used for every pad in the web UI. Not used for the HTTP API.
+ *              If there is not already an author associated with this token, and access is not
+ *              denied, an author object will be created (including generating an author ID) and
+ *              saved in the DB.
  * @param password the password the user has given to access this pad, can be null
  * @return {accessStatus: grant|deny|wrongPassword|needPassword, authorID: a.xxxxxx})
  */

src/node/handler/PadMessageHandler.js

@@ -36,6 +36,7 @@ var hooks = require("ep_etherpad-lite/static/js/pluginfw/hooks.js");
 var channels = require("channels");
 var stats = require('../stats');
 var remoteAddress = require("../utils/RemoteAddress").remoteAddress;
+const assert = require('assert').strict;
 const nodeify = require("nodeify");
 const { RateLimiterMemory } = require('rate-limiter-flexible');
 
@@ -914,10 +915,14 @@ async function handleClientReady(client, message)
   // Get ro/rw id:s
   let padIds = await readOnlyManager.getIds(message.padId);
 
-  // check permissions
-
-  // Note: message.sessionID is an entierly different kind of
-  // session from the sessions we use here! Beware!
+  // Check permissions. Notes:
+  //   * If there is not already an author associated with the client-generated token, and access is
+  //     not denied, checkAccess will create an author object (including generating an author ID)
+  //     and save it in the DB.
+  //   * Tokens must be kept secret, otherwise users will able to impersonate each other (which
+  //     might allow them to gain privileges).
+  //   * message.sessionID is an entierly different kind of session from the sessions we use here!
+  //     Beware!
   // FIXME: Call our "sessions" "connections".
   // FIXME: Use a hook instead
   // FIXME: Allow to override readwrite access with readonly
@@ -933,19 +938,11 @@ async function handleClientReady(client, message)
   let author = statusObject.authorID;
 
   // get all authordata of this new user
+  assert(author);
   let value = await authorManager.getAuthor(author);
   let authorColorId = value.colorId;
   let authorName = value.name;
 
-  /*
-  * Here we know authorID, token and session.  We should ?always? store it..
-  * TODO: I fear that this might allow a user to pass a token for an authorID
-  * meaning that they could in theory "imitate" another author?
-  * Perhaps the fix to this is check to see if it exists first and if it
-  * does then abort..  Details: https://github.com/ether/etherpad-lite/issues/4006
-  */
-  await authorManager.setToken2Author(message.token, statusObject.authorID)
-
   // load the pad-object from the database
   let pad = await padManager.getPad(padIds.padId);