Fixed security hole in email address change flow

refs https://github.com/TryGhost/Ghost/security/advisories/GHSA-65p7-pjj8-ggmr

The email address change flow was built on top of the unauthenticated
signin/signup flow. This meant that ownership of the email being changed
wasn't verified and allowed a malicious actore to change the email
address of arbitrary accounts to an email address which they controlled.

We remove the ability to change email addresses from the signin/signup
flow and instead create a dedicated, authenticated flow for changing
email address.

ghost/members-api/lib/MembersAPI.js

@@ -156,8 +156,9 @@ module.exports = function MembersAPI({
     const memberController = new MemberController({
         memberRepository,
         StripePrice,
-        stripeAPIService,
-        tokenService
+        tokenService,
+        sendEmailWithMagicLink,
+        allowSelfSignup
     });
 
     const routerController = new RouterController({
@@ -356,6 +357,10 @@ module.exports = function MembersAPI({
             body.json(),
             (req, res) => MembersAnalyticsIngress.createEvents(req, res)
         ),
+        updateEmailAddress: Router().use(
+            body.json(),
+            (req, res) => memberController.updateEmailAddress(req, res)
+        ),
         updateSubscription: Router({mergeParams: true}).use(
             body.json(),
             (req, res) => memberController.updateSubscription(req, res)

ghost/members-api/lib/controllers/member.js

@@ -1,25 +1,57 @@
 const errors = require('@tryghost/ignition-errors');
 
+module.exports = class MemberController {
     /**
- * MemberController
- *
      * @param {object} deps
      * @param {any} deps.memberRepository
      * @param {any} deps.StripePrice
- * @param {any} deps.stripeApiService
      * @param {any} deps.tokenService
+     * @param {any} deps.sendEmailWithMagicLink
+     * @param {boolean} deps.allowSelfSignup
      */
-module.exports = class MemberController {
     constructor({
         memberRepository,
         StripePrice,
-        stripeAPIService,
-        tokenService
+        tokenService,
+        sendEmailWithMagicLink,
+        allowSelfSignup
     }) {
         this._memberRepository = memberRepository;
         this._StripePrice = StripePrice;
-        this._stripeApiService = stripeAPIService;
         this._tokenService = tokenService;
+        this._sendEmailWithMagicLink = sendEmailWithMagicLink;
+        this._allowSelfSignup = allowSelfSignup;
+    }
+
+    async updateEmailAddress(req, res) {
+        const identity = req.body.identity;
+        const email = req.body.email;
+        const options = {
+            forceEmailType: true
+        };
+
+        if (!identity) {
+            res.writeHead(403);
+            return res.end('No Permission.');
+        }
+
+        let tokenData = {};
+        try {
+            const member = await this._memberRepository.getByToken(identity);
+            tokenData.oldEmail = member.get('email');
+        } catch (err) {
+            res.writeHead(401);
+            res.end('Unauthorized.');
+        }
+
+        try {
+            await this._sendEmailWithMagicLink({email, tokenData, requestedType: 'updateEmail', options});
+            res.writeHead(201);
+            return res.end('Created.');
+        } catch (err) {
+            res.writeHead(500);
+            return res.end('Internal Server Error.');
+        }
     }
 
     async updateSubscription(req, res) {

ghost/members-api/lib/controllers/router.js

@@ -1,6 +1,5 @@
 const common = require('../../lib/common');
 const _ = require('lodash');
-const errors = require('@tryghost/ignition-errors');
 
 /**
  * RouterController
@@ -219,33 +218,22 @@ module.exports = class RouterController {
     }
 
     async sendMagicLink(req, res) {
-        const {email, emailType, oldEmail, requestSrc} = req.body;
-        let forceEmailType = false;
+        const {email, emailType, requestSrc} = req.body;
         if (!email) {
             res.writeHead(400);
             return res.end('Bad Request.');
         }
 
         try {
-            if (oldEmail) {
-                const existingMember = await this._memberRepository.get({email});
-                if (existingMember) {
-                    throw new errors.BadRequestError({
-                        message: 'This email is already associated with a member'
-                    });
-                }
-                forceEmailType = true;
-            }
-
             if (!this._allowSelfSignup) {
-                const member = oldEmail ? await this._memberRepository.get({oldEmail}) : await this._memberRepository.get({email});
+                const member = await this._memberRepository.get({email});
                 if (member) {
-                    const tokenData = _.pick(req.body, ['oldEmail']);
-                    await this._sendEmailWithMagicLink({email, tokenData, requestedType: emailType, requestSrc, options: {forceEmailType}});
+                    const tokenData = {};
+                    await this._sendEmailWithMagicLink({email, tokenData, requestedType: emailType, requestSrc});
                 }
             } else {
-                const tokenData = _.pick(req.body, ['labels', 'name', 'oldEmail']);
-                await this._sendEmailWithMagicLink({email, tokenData, requestedType: emailType, requestSrc, options: {forceEmailType}});
+                const tokenData = _.pick(req.body, ['labels', 'name']);
+                await this._sendEmailWithMagicLink({email, tokenData, requestedType: emailType, requestSrc});
             }
             res.writeHead(201);
             return res.end('Created.');