[TASK] Update LedgerEthChromeApp with Cross-Extension-Messaging

[ghost]

re #4060 (was #717)

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Goal

Allow bidirectional communication between MetaMask and Ledger Eth Wallet Chrome App, using Cross-Extension-Messaging (CEM) as described in:

• https://developer.chrome.com/extensions/messaging#external
• Possibly already implemented/allowed within MetaMask
  • similar/equal: Extension-to-extension communication (see Doc: extension-to-extension provider connections #4322 / Allow other extensions to connect #3997)

CEM works for "Chrome Apps", too":

• "Sends a single message to event listeners within your extension/app or a different extension/app."
• https://developer.chrome.com/extensions/runtime#method-sendMessage

Sequence

• Metamask Creates a Transaction
• Requests Signature from Ledger (ledger-extension provides api via CEM)
• Ledger-Extension communicates with Ledger, user signs
• MetaMask gets the signed transaction via CEM
• MetaMask continues as usual

PoC

An extension/app which simulates the Ledger part, just to proof that CEM can handle the above sequence

Implementation

• Update the Ledger Eth App (strange: written in Scala) with an Interface:
  • https://github.com/LedgerHQ/ledger-wallet-ethereum-chrome
• This app can be then installed by the users (possible name: LedgerEthMetaMask App)
• LedgerHQ can possibly accept the new app in its standard-distribution

Resources

• https://github.com/GoogleChrome/chrome-app-samples/tree/master/samples/messaging
• https://www.ledgerwallet.com/apps/ethereum
• https://github.com/LedgerHQ/ledger-wallet-api/blob/develop/doc-api-ETH.md

LEGACY SOFTWARE

This is legacy software, will be replaced by

• the desktop-app (https://github.com/LedgerHQ/ledger-live-desktop)
• the new js-interfaces (working directly with ledger): https://github.com/LedgerHQ/ledgerjs

[danfinlay]

Wouldn't this require the ledger having a browser extension of its own?

Would that extension not have the same problems connecting over the U2F protocol?

Are they maybe using a native app to connect to the extension?

This feature has been merged into master, and should be deployed to production by the end of the day:
#3997

[ghost]

This works with chrome apps, too, I've updated the text.

This should be the way to go.

#3997 is based on Cross-Extension-Messaging?

(Sidenote: I'm currently off-code, and I must stay off-code to keep my architectural thinking/creativity up. I usually have only one of the two (coding/architecture) abilities on "super-flow". Thus depending here totally on team-work, which seems to mean that I depend on the code-level work of e.g. jamespic. If this does not makes sense, just ignore this sidenote)

[ghost]

@danfinlay although this would work, it's (soon-to-be) legacy-software. I'm closing as "wontfix". There is another path which uses the latest ledger software (e.g. no legacy, no need to dig into Scala etc.).

[danfinlay]

Looks like the same situation for Trezor. They now have a native app to connect to.

[ghost]

With Ledger, we have still an option (or even two) to avoid the Native App (thus MetaMask can work with Ledger without having to open the Native App). See within #4060, should be the final path now.