Push Protocol Snap for MetaMask

1 Executive Summary

This report presents the results of our engagement with PushProtocol to review Snap v1, a MetaMask Snap for delivering channel notifications and chat notifications within metamask wallet.

The review was conducted from July 5, 2023 to July 6, 2023. A total of 2 person-days were spent.

2 Scope

The review focused on the commit hash c1636586dee1e43cd447f9c4ac03b0d776224f9c. The list of files in scope can be found in the Appendix.

The Technical Specification can be found here.

2.1 Verification Phase

Mitigations were reviewed from July 11, 2023 to July 13, 2023 focussing on the commit hash 1a6a32ef760088ca59f73e555f41b5b5d871f761.

Update 1:

The client provided commit hash 1a6a32ef760088ca59f73e555f41b5b5d871f761 for review addressing outstanding issues on July 14, 2023.

Update 2:

The client provided commit hash b40e141243c77bfd7ec109408b326607b19314c8 for review addressing outstanding issues on July 17, 2023.

2.2 Objectives

Together with the Push Protocol team, we identified the following priorities for our review:

1. Correctness of the implementation, consistent with the intended functionality and without unintended edge cases.
2. Identify vulnerabilities particular to the MetaMask Snaps SDK integration in coherence with the MetaMask Snap Threat Model describing a Snap as an extension of the MetaMask Wallet Trust Module.

3 Document Change Log

4 Snap Outline

• The snap stores addresses to be monitore and config settings in snap_manageState.
• The snap may interact with the following 3rd party service providers via the fetch() API:
  • https://backend-prod.epns.io/apis/v1/users/eip155:5:${address}/feeds
• Connected dapps can communicate with the snap via MetaMask snap RPC.
• The Snap registers a cronjob that fires every minute, fetching new notifications.

Note: Notification messages for all addresses are public. Anyone can subscribe to notifications sent to any address. The back-end API does not authenticate the requested address (signature). The wallet may require proof of ownership but this is only implemented in the front-end (dapp) and can easily be bypassed.

4.1 Capabilities

Details

👉 249 (lines of code)
[🚀 == Bundle == ]
    🔺 Error: Missing file "images/icon.svg".
    🔺 - package-lock missing
    🔺 - package.json: invalid license '(MIT-0 OR Apache-2.0)'
----%<---- raw permissions
🌐 : https://docs.metamask.io/snaps/reference/rpc-api/#wallet_requestsnaps
{
  snap_dialog: {},
  'endowment:rpc': { dapps: true, snaps: false },
  snap_notify: {},
  'endowment:cronjob': { jobs: [ [Object] ] },
  'endowment:network-access': {},
  snap_manageState: {},
  'endowment:ethereum-provider': {}
}
---->%---- raw permissions
🚜 [snap_dialog]
    ☝️ - snap_dialog - Displays a dialog in the MetaMask UI. There are three types of dialogs with different parameters and return types.
    ⚠️ - this method renders Markdown! check for ctrlchar/markdown/injection
       🔸  src/index.ts
       🔸  src/utils/fetchAddress.ts
🚜 [endowment:rpc]
    ❗- endowment:rpc.dapps - snap can communicate with websites/dapps; check origin for internal api calls!
       🔸  src/index.ts
🚜 [snap_notify]
    👌 - snap_notify - Displays a notification in MetaMask or natively in the browser. Snaps can trigger a short notification text for actionable or time sensitive information.
     ⚠️ - this method renders Markdown! check for ctrlchar/markdown/injection
       🔸  src/index.ts
🚜 [endowment:cronjob]
    ❗- endowment:cronjob.fireCronjob - fires every minute! (* * * * *)
       🔸  src/index.ts
🚜 [endowment:network-access]
    🌐 - endowment:network-access - snap can access internet
     ⚠️ - this method may leak information to external api
       🔸  src/index.ts
       🔸  src/utils/fetchnotifs.ts
🚜 [snap_manageState]
    🪤 - snap_manageState - snap can store up to 100mb (isolated)
       🔸  src/index.ts
       🔸  src/utils/toggleHelper.ts
       🔸  src/utils/fetchAddress.ts
🚜 [endowment:ethereum-provider]
    🔺 - endowment:ethereum-provider - snap can access ethereum API
    ⚠️ - check if the **snap code** (not site) actually accesses the global object 'window.ethereum'
       🔺 - superfluous permission: no reference to 'window.ethereum.*'!

4.2 Dependencies

🌲 - Package Depenencies:
      - ethers:5.7.2

5 Findings

Each issue has an assigned severity:

• Minor issues are subjective in nature. They are typically suggestions around best practices or readability. Code maintainers should use their own judgment as to whether to address such issues.
• Medium issues are objective in nature but are not security vulnerabilities. These should be addressed unless there is a clear reason not to.
• Major issues are security vulnerabilities that may not be directly exploitable or may require certain conditions in order to be exploited. All major issues should be addressed.
• Critical issues are directly exploitable security vulnerabilities that need to be fixed.

"endowment:ethereum-provider": {}

await window.ethereum?.request({
      method: "wallet_invokeSnap",
      params: {
        snapId: "local:http://localhost:8080",
        request: { method: 'hello', params: { address: "\nhi\nho" } },
      }})

export default function ConfirmButton() {
  const { address, isConnecting, isDisconnected } = useAccount();
  const defaultSnapOrigin = `local:http://localhost:8080`;

  const sendHello = async (address: string) => {
    await window.ethereum?.request({
      method: "wallet_invokeSnap",
      params: {
        snapId: defaultSnapOrigin,
        request: { method: 'hello', params: { address: address } },
      },
    });
  };

  const { data, isError, isLoading, isSuccess, signMessage } = useSignMessage({
    message:
      `Confirm your Address ${address}, \n this will be added to MetaMask for sending notifications`,
  });

  function sleep(ms: number) {
    return new Promise((resolve) => setTimeout(resolve, ms));
  }

  const confirmAddition=async()=>{
    signMessage();
    if(isSuccess){
      await sleep(5000);
      await sendHello(String(address));
    }
  }

await addAddress(request.params.address || "0x0");

await window.ethereum?.request({
      method: "wallet_invokeSnap",
      params: {
        snapId: "local:http://localhost:8080",
        request: { method: 'hello', params: { address: "Hi 🙌\n\n 🔸 **boom**" } },
      }})

export const getNotifications=async(address:string)=>{
    const url = `https://backend-prod.epns.io/apis/v1/users/eip155:5:${address}/feeds`;
    const response = await fetch(url, {
      method: 'get',
      headers: {
        'Content-Type': 'application/json',
      },
    });
    const data = await response.json();
    return data;
  }

export const popupHelper = (notifs: String[]) => {
  let msg = [];
  if (notifs.length > 0) {
    notifs.forEach((notif) => {
      let str = `\n🔔` + notif + "\n";
      msg.push(str);
    });
  }
  return msg;
};

const data = persistedData.addresses;
const popup = persistedData.popuptoggle;
let msg='';
for(let i = 0; i < data!.length; i++){
    msg = msg + '🔹' + data![i] + '\n';
}
return snap.request({
    method: 'snap_dialog',

Oops! Something went wrong.
Snap Error: 'Cannot read properties of null (reading 'addresses')'. Error Code: '-32603'

export const addAddress = async (address:string) => {

    const persistedData = await snap.request({
        method: 'snap_manageState',
        params: { operation: 'get' },
    });

    if(persistedData == null){
        const data = {
            addresses: [address],
            popuptoggle: 0,
        };
        await snap.request({
            method: 'snap_manageState',
            params: { operation: 'update', newState:data },
        });

export const onRpcRequest: OnRpcRequestHandler = async ({
  origin,
  request,
}) => {
  switch (request.method) {
    case "hello": {
      await addAddress(request.params.address || "0x0");
      await confirmAddress();
      break;
    }

let persistedData = await snap.request({
    method: 'snap_manageState',
    params: { operation: 'get' },
});

let popuptoggle = notifcount;

const data = {
    addresses: persistedData.addresses,
    popuptoggle: popuptoggle,
};

const { data, isError, isLoading, isSuccess, signMessage } = useSignMessage({
  message:
    `Confirm your Address ${address}, \n this will be added to MetaMask for sending notifications`,
});

Type '{ addresses: Json; popuptoggle: Number; }' is not assignable to type 'Record<string, Json>'.
  Property 'popuptoggle' is incompatible with index signature.
    Type 'Number' is not assignable to type 'Json'.
      Type 'Number' is not assignable to type '{ [prop: string]: Json; }'.
        Index signature for type 'string' is missing in type 'Number'.ts(2322)

let popuptoggle = notifcount;

const data = {
    addresses: persistedData.addresses,
    popuptoggle: popuptoggle,
};
await snap.request({
    method: 'snap_manageState',
    params: { operation: 'update', newState:data },
});

Variable 'msg' implicitly has an 'any[]' type.ts(7005)

export const fetchAllAddrNotifs = async () => {
    const addresses = await fetchAddress();
    let notifs:String[] = [];
    for(let i = 0; i < addresses.length; i++){

let persistedData = await snap.request({
  method: "snap_manageState",
  params: { operation: "get" },
});

let popuptoggle = Number(persistedData.popuptoggle) + msgs.length;

export default function ConfirmButton() {
  const { address, isConnecting, isDisconnected } = useAccount();
  const defaultSnapOrigin = `local:http://localhost:8080`;

export default function ReconnectButton() {

  const defaultSnapOrigin = `local:http://localhost:8080`;

export default function ReconnectButton() {

  const defaultSnapOrigin = `local:http://localhost:8080`;

"license": "(MIT-0 OR Apache-2.0)",

export const fetchAddress = async () => {
    const persistedData = await snap.request({
        method: 'snap_manageState',
        params: { operation: 'get' },
    });
    const addresses = persistedData!.addresses;
    return addresses;
};

export const filterNotifications=async(address:string)=>{
  let fetchedNotifications = await getNotifications(address);
  fetchedNotifications = fetchedNotifications?.feeds;
  let notiffeeds:String[] = [];
  const currentepoch:string = Math.floor(Date.now() / 1000).toString();
  if(fetchedNotifications.length > 0){
    for(let i = 0; i < fetchedNotifications.length; i++){
      let feedepoch = fetchedNotifications[i].payload.data.epoch;
      feedepoch = Number(feedepoch).toFixed(0);
      if(feedepoch > parseInt(currentepoch)-60) {              
        let msg = fetchedNotifications[i].payload.data.app+' : '+fetchedNotifications[i].payload.data.amsg;
        notiffeeds.push(msg);
      }
    }
  }
  notiffeeds = notiffeeds.reverse();
  return notiffeeds;

export const confirmAddress = async () => {
    const persistedData = await snap.request({
        method: 'snap_manageState',
        params: { operation: 'get' },
    });
    const data = persistedData.addresses;
    const popup = persistedData.popuptoggle;
    let msg='';

const {ethers} = require('ethers');

import { heading, panel, text } from "@metamask/snaps-ui";

extends: ['../../.eslintrc.js'],

⇒  npm run lint:eslint

> [email protected] lint:eslint
> eslint . --cache --ext js,ts


Oops! Something went wrong! :(

ESLint: 8.40.0

ESLint couldn't find the config "../../.eslintrc.js" to extend from. Please check that the name of the config is correct.

The config "../../.eslintrc.js" was referenced from the config file in "/Users/tintin/workspace/js/push-protocol-snaps/snap/.eslintrc.js".

"extends": "../../tsconfig.json",

let temp = await filterNotifications(addresses[i]);

case "hello": {

case "init": {

case "togglepopup": {

Appendix 1 - Files in Scope

Appendix 2 - Disclosure

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