export: Don't leak writeable pad ID when exporting

Co-authored-by: Richard Hansen <rhansen@rhansen.org>

CHANGELOG.md

@@ -1,5 +1,19 @@
 # Next Release
 
+### Security fixes
+
+* Fixed leak of the writable pad ID when exporting from the pad's read-only ID.
+  This only matters if you treat the writeable pad IDs as secret (e.g., you are
+  not using [ep_padlist2](https://www.npmjs.com/package/ep_padlist2)) and you
+  share the pad's read-only ID with untrusted users. Instead of treating
+  writeable pad IDs as secret, you are encouraged to take advantage of
+  Etherpad's authentication and authorization mechanisms (e.g., use
+  [ep_openid_connect](https://www.npmjs.com/package/ep_openid_connect) with
+  [ep_readonly_guest](https://www.npmjs.com/package/ep_readonly_guest), or write
+  your own
+  [authentication](https://etherpad.org/doc/v1.8.14/#index_authenticate) and
+  [authorization](https://etherpad.org/doc/v1.8.14/#index_authorize) plugins).
+
 ### Compatibility changes
 
 * For plugin authors:

src/node/handler/ExportHandler.js

@@ -56,14 +56,14 @@ exports.doExport = async (req, res, padId, readOnlyId, type) => {
   // if this is a plain text export, we can do this directly
   // We have to over engineer this because tabs are stored as attributes and not plain text
   if (type === 'etherpad') {
-    const pad = await exportEtherpad.getPadRaw(padId);
+    const pad = await exportEtherpad.getPadRaw(padId, readOnlyId);
     res.send(pad);
   } else if (type === 'txt') {
     const txt = await exporttxt.getPadTXTDocument(padId, req.params.rev);
     res.send(txt);
   } else {
     // render the html document
-    let html = await exporthtml.getPadHTMLDocument(padId, req.params.rev);
+    let html = await exporthtml.getPadHTMLDocument(padId, req.params.rev, readOnlyId);
 
     // decide what to do with the html export
 

src/node/utils/ExportEtherpad.js

@@ -19,23 +19,18 @@
 const db = require('../db/DB');
 const hooks = require('../../static/js/pluginfw/hooks');
 
-exports.getPadRaw = async (padId) => {
+exports.getPadRaw = async (padId, readOnlyId) => {
-  const padKey = `pad:${padId}`;
+  const keyPrefixRead = `pad:${padId}`;
-  const padcontent = await db.get(padKey);
+  const keyPrefixWrite = readOnlyId ? `pad:${readOnlyId}` : keyPrefixRead;
+  const padcontent = await db.get(keyPrefixRead);
 
-  const records = [padKey];
+  const keySuffixes = [''];
-  for (let i = 0; i <= padcontent.head; i++) {
+  for (let i = 0; i <= padcontent.head; i++) keySuffixes.push(`:revs:${i}`);
-    records.push(`${padKey}:revs:${i}`);
+  for (let i = 0; i <= padcontent.chatHead; i++) keySuffixes.push(`:chat:${i}`);
-  }
-
-  for (let i = 0; i <= padcontent.chatHead; i++) {
-    records.push(`${padKey}:chat:${i}`);
-  }
 
   const data = {};
-  for (const key of records) {
+  for (const keySuffix of keySuffixes) {
-    // For each piece of info about a pad.
+    const entry = data[keyPrefixWrite + keySuffix] = await db.get(keyPrefixRead + keySuffix);
-    const entry = data[key] = await db.get(key);
 
     // Get the Pad Authors
     if (entry.pool && entry.pool.numToAttrib) {
@@ -50,7 +45,7 @@ exports.getPadRaw = async (padId) => {
           if (authorEntry) {
             data[`globalAuthor:${authorId}`] = authorEntry;
             if (authorEntry.padIDs) {
-              authorEntry.padIDs = padId;
+              authorEntry.padIDs = readOnlyId || padId;
             }
           }
         }
@@ -63,7 +58,8 @@ exports.getPadRaw = async (padId) => {
   const prefixes = await hooks.aCallAll('exportEtherpadAdditionalContent');
   await Promise.all(prefixes.map(async (prefix) => {
     const key = `${prefix}:${padId}`;
-    data[key] = await db.get(key);
+    const writeKey = readOnlyId ? `${prefix}:${readOnlyId}` : key;
+    data[writeKey] = await db.get(key);
   }));
 
   return data;

src/node/utils/ExportHtml.js

@@ -457,7 +457,7 @@ const getHTMLFromAtext = async (pad, atext, authorColors) => {
   return pieces.join('');
 };
 
-exports.getPadHTMLDocument = async (padId, revNum) => {
+exports.getPadHTMLDocument = async (padId, revNum, readOnlyId) => {
   const pad = await padManager.getPad(padId);
 
   // Include some Styles into the Head for Export
@@ -475,7 +475,7 @@ exports.getPadHTMLDocument = async (padId, revNum) => {
 
   return eejs.require('ep_etherpad-lite/templates/export_html.html', {
     body: html,
-    padId: Security.escapeHTML(padId),
+    padId: Security.escapeHTML(readOnlyId || padId),
     extraCSS: stylesForExportCSS,
   });
 };