MetaMask/Partner Snaps - FilSnap

1 Executive Summary

This report presents the results of our engagement with Protocol Labs to review their FilSnap MetaMask Snap.

The review was conducted over two weeks, from August 14, 2023, to August 18, 2023, by Dominik Muhs. A total of five person-days were spent.

Most notably, two critical issues have been identified regarding displaying Markdown-rendered dialogues and the programmatic handling of private key information. Furthermore, two major findings present security considerations for the configuration functionality and the user signature confirmation dialogue lacking origin information.

A follow-up assessment has been conducted from October 2, 2023 to October 3, 2023 by Dominik Muhs. A total of two person-days were spent.

2 Scope

Our review initially focused on the commit hash 5c5e6ad523d198d12bdd2057028dad429435bc6f. In the follow-up assessment, the fixes were verified against the commit hash 8374e6aea59941d98bf29ca5e902df9eebf919f0. The list of files in scope for both engagements can be found in the Appendix.

One day after the scheduled verification deadline, the development team submitted commit 6ddb227738ed3aa041c18131eee65a98e17acdf4, fixing issue 4.4 completely. This change has been added to the report.

2.1 Objectives

Together with the Protocol Labs 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 System Overview

4 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.

const conf = await snapDialog(ctx.snap, {
  type: 'confirmation',
  content: panel([
    heading(`Send ${Token.fromAttoFIL(message.value).toFIL().toString()} to`),
    copyable(message.to),
    divider(),
    heading('Details'),
    text(
      `Gas _(estimated)_: **${gas.toFIL().toFormat({
        decimalPlaces: ctx.config.unit?.decimals,
        suffix: ` ${ctx.config.unit?.symbol}`,
      })}**`
    ),
    text(
      `Total _(amount + gas)_: **${total.toFIL().toFormat({
        decimalPlaces: ctx.config.unit?.decimals,
        suffix: ` ${ctx.config.unit?.symbol}`,
      })}**`
    ),
  ]),
})

export async function exportPrivateKey(
  ctx: SnapContext
): Promise<ExportPrivateKeyResponse> {
  const conf = await snapDialog(ctx.snap, {
    type: 'confirmation',
    content: panel([heading(`Do you want to export your private key?`)]),
  })

  if (conf) {
    return {
      result: base64pad.encode(ctx.account.privateKey),
      error: null,
    }
  }
  return serializeError('User denied private key export')
}

type ConfigureParams = {
    derivationPath?: string | undefined;
    rpc?: {
        url: string;
        token: string;
    } | undefined;
    network?: "mainnet" | "testnet" | undefined;
    unit?: {
        symbol: string;
        decimals: number;
        image?: string | undefined;
        customViewUrl?: string | undefined;
    } | undefined;
}

const conf = await snapDialog(ctx.snap, {
  type: 'confirmation',
  content: panel([
    heading(`Send ${Token.fromAttoFIL(message.value).toFIL().toString()} to`),
    copyable(message.to),
    divider(),
    heading('Details'),
    text(
      `Gas _(estimated)_: **${gas.toFIL().toFormat({
        decimalPlaces: ctx.config.unit?.decimals,
        suffix: ` ${ctx.config.unit?.symbol}`,
      })}**`
    ),
    text(
      `Total _(amount + gas)_: **${total.toFIL().toFormat({
        decimalPlaces: ctx.config.unit?.decimals,
        suffix: ` ${ctx.config.unit?.symbol}`,
      })}**`
    ),
  ]),
})

const res = await this.fetch(this.api, {
  method: 'POST',
  headers: this.headers,
  body: JSON.stringify({
    jsonrpc: '2.0',
    method,
    params,
    id: 1,
  }),
})

const context: SnapContext = {
  config,
  rpc,
  account,
  snap,
}

Appendix 1 - Files in Scope

This audit covered the following files:

The follow-up assessment covered the following files:

Appendix 2 - Disclosure

Consensys Diligence (“CD”) typically receives compensation from one or more clients (the “Clients”) for performing the analysis contained in these reports (the “Reports”). The Reports may be distributed through other means, including via Consensys publications and other distributions.

The Reports are not an endorsement or indictment of any particular project or team, and the Reports do not guarantee the security of any particular project. This Report does not consider, and should not be interpreted as considering or having any bearing on, the potential economics of a token, token sale or any other product, service or other asset. Cryptographic tokens are emergent technologies and carry with them high levels of technical risk and uncertainty. No Report provides any warranty or representation to any third party in any respect, including regarding the bug-free nature of code, the business model or proprietors of any such business model, and the legal compliance of any such business. No third party should rely on the Reports in any way, including for the purpose of making any decisions to buy or sell any token, product, service or other asset. Specifically, for the avoidance of doubt, this Report does not constitute investment advice, is not intended to be relied upon as investment advice, is not an endorsement of this project or team, and it is not a guarantee as to the absolute security of the project. CD owes no duty to any third party by virtue of publishing these Reports.

A.2.1 Purpose of Reports

The Reports and the analysis described therein are created solely for Clients and published with their consent. The scope of our review is limited to a review of code and only the code we note as being within the scope of our review within this report. Any Solidity code itself presents unique and unquantifiable risks as the Solidity language itself remains under development and is subject to unknown risks and flaws. The review does not extend to the compiler layer, or any other areas beyond specified code that could present security risks. Cryptographic tokens are emergent technologies and carry with them high levels of technical risk and uncertainty. In some instances, we may perform penetration testing or infrastructure assessments depending on the scope of the particular engagement.

CD makes the Reports available to parties other than the Clients (i.e., “third parties”) on its website. CD hopes that by making these analyses publicly available, it can help the blockchain ecosystem develop technical best practices in this rapidly evolving area of innovation.

A.2.2 Links to Other Web Sites from This Web Site

You may, through hypertext or other computer links, gain access to web sites operated by persons other than Consensys and CD. Such hyperlinks are provided for your reference and convenience only, and are the exclusive responsibility of such web sites’ owners. You agree that Consensys and CD are not responsible for the content or operation of such Web sites, and that Consensys and CD shall have no liability to you or any other person or entity for the use of third party Web sites. Except as described below, a hyperlink from this web Site to another web site does not imply or mean that Consensys and CD endorses the content on that Web site or the operator or operations of that site. You are solely responsible for determining the extent to which you may use any content at any other web sites to which you link from the Reports. Consensys and CD assumes no responsibility for the use of third-party software on the Web Site and shall have no liability whatsoever to any person or entity for the accuracy or completeness of any outcome generated by such software.

A.2.3 Timeliness of Content

The content contained in the Reports is current as of the date appearing on the Report and is subject to change without notice unless indicated otherwise, by Consensys and CD.