[TASK] Implement mm-ledger-gateway

[ghost]

affects #4060

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(draft)

Problem

USB access is not allowed for extensions, thus the Ledger hw-wallet cannot be accessed directly by MetaMask.

Solution Summary

• Implement a "mini-metamask" within a chrome app, which accesses the ledger device directly
• Only the minimal functionality needed is implemented
• Allow the metamask-extension to connect to this "mini-metamask" chrome app

Solution Details

This solution does not depend on the Ledger Native app. MetaMask would be able to communicate directly to the Ledger-Device, by using only the mm-ledger-gateway.

A) ledgerjs

The relevant ledger libraries:

Preferred Path (Latest Ledger code, no native-code or desktop-app needed)

• https://github.com/LedgerHQ/ledgerjs
• https://github.com/LedgerHQ/ledgerjs/tree/master/packages/hw-app-eth
• https://github.com/LedgerHQ/ledgerjs/blob/master/docs/ethereum_ledger_integration.md

A.1) mm-ledger-u2f-gateway Chrome App

• Chrome App can access U2F and works with cross-extension-messaging

• Within this Chrome App, Implement a provider:

  • https://github.com/LedgerHQ/ledgerjs/blob/master/docs/ethereum_ledger_integration.md
  • allow only MM to access this app

• The provider is then accessed by MM using the same technique as here:

  • Allow other extensions to connect #3997
  • https://developer.chrome.com/extensions/messaging#external

The eth-ledger-keyring depends-on/accesses the mm-ledger-u2f-gateway

User Manual: "If you want to interface Ledger, you have to install additionally the mm-ledger-u2f-gateway Chrome App

A.2) mm-ledger-u2f-gateway IFRAME

Same as above, but uses an IFRAME and (mm-extension-) internal-messaging

(no additional installation steps needed)

Further alternatives

xyz = any applicable alternative transport

• mm-ledger-xyz-gateway Chrome-App or IFRAME

End Notes

The same Solution-Path should be applicable to other hw-wallets (including Trezor, for a more direct interfacing-approach than #4625)

[ghost]

The "A.2) mm-ledger-u2f-gateway IFRAME" was implemented within #5050

[ethanfrey]

Curious about the solution using chrome apps, as they seem to be deprecated... https://9to5google.com/2017/12/06/google-chrome-apps-dead-web-store/

But I guess the iframe solution won in the end

[ghost]

@ethanfrey , I somewhere saw that the end-of-life for chrome-apps was extended. Additionally, A.1 and A.2 use essentially the same messaging-technique, thus code produced for A.1 could be reusable for a A.2 implementation.

Both A.1 and A.2 implementations are not the final ones. They are just kind of workarounds, until a direct-access-layer (U2F or WebUSB) for browser-extensions is provided by the browsers.

(feel free to contact me via info at lazaridis.com, here @ MetaMask the things are done/closed)