Opt-in account exposure

Simple summary

This proposal describes a communication protocol between dapps and Ethereum-enabled DOM environments that allows the Ethereum-enabled DOM environment to choose what information to supply the dapp with and when.

Abstract

The previous generation of Ethereum-enabled DOM environments follows a pattern of injecting a provider populated with accounts without user consent. This puts users of such environments at risk because malicious websites can use these accounts to view detailed account information and to arbitrarily initiate unwanted transactions on a user's behalf.

This proposal outlines a protocol in which Ethereum-enabled DOM environments can choose to expose no accounts until the user approves account access.

Specification

Concepts

RFC-2119

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119.

eth_requestAccounts

Providers exposed by Ethereum-enabled DOM environments define a new RPC method: eth_requestAccounts. Calling this method may trigger a user interface that allows the user to approve or reject account access for a given dapp. This method returns a Promise that is resolved with an Array of accounts or is rejected with an Error if accounts are not available.

ethereum.send('eth_requestAccounts'): Promise<Array<string>>

Provider#enable (DEPRECATED)

Note: This method is deprecated in favor of the RPC method eth_requestAccounts.

Providers exposed by Ethereum-enabled DOM environments define a new RPC method: ethereum.enable(). Calling this method triggers a user interface that allows the user to approve or reject account access for a given dapp. This method returns a Promise that is resolved with an Array of accounts if the user approves access or rejected with an Error if the user rejects access.

ethereum.enable(): Promise<any>

Protocol

Legacy dapp initialization

START dapp
IF web3 is defined
    CONTINUE dapp
IF web3 is undefined
    STOP dapp

Proposed dapp initialization

START dapp
IF provider is defined
    REQUEST[1] account access
    IF user approves
        RESOLVE[2] account access
        CONTINUE dapp
    IF user rejects
        REJECT[3] account access
        STOP dapp
IF provider is undefined
    STOP dapp

[1] REQUEST

Dapps MUST request accounts by calling the eth_requestAccounts RPC method on the provider exposed at window.ethereum. Calling this method MAY trigger a user interface that allows the user to approve or reject account access for a given dapp. This method MUST return a Promise that is resolved with an array of one or more user accounts or rejected if no accounts are available (e.g., the user rejected account access).

[2] RESOLVE

The Promise returned when calling the eth_requestAccounts RPC method MUST be resolved with an Array of user accounts.

[3] REJECT

The Promise returned when calling the eth_requestAccounts RPC method MUST be rejected with an informative Error if no accounts are available for any reason.

Example initialization

try {
    // Request account access if needed
    const accounts = await ethereum.send('eth_requestAccounts');
    // Accounts now exposed, use them
    ethereum.send('eth_sendTransaction', { from: accounts[0], /* ... */ })
} catch (error) {
    // User denied account access
}

Constraints

• Browsers MUST expose a provider at window.ethereum .
• Browsers MUST define an eth_requestAccounts RPC method.
• Browsers MAY wait for a user interaction before resolving/rejecting the eth_requestAccounts promise.
• Browsers MUST include at least one account if the eth_requestAccounts promise is resolved.
• Browsers MUST reject the promise with an informative error if no accounts are available.

Rationale

The pattern of automatic account exposure followed by the previous generation of Ethereum-enabled DOM environments fails to protect user privacy and fails to maintain safe user experience: untrusted websites can both view detailed account information and arbitrarily initiate transactions on a user's behalf. Even though most users may reject unsolicited transactions on untrusted websites, a protocol for account access should make such unsolicited requests impossible.

This proposal establishes a new pattern wherein dapps must request access to user accounts. This protocol directly strengthens user privacy by allowing the browser to hide user accounts and preventing unsolicited transaction requests on untrusted sites.

Immediate value-add

• Users can reject account access on untrusted sites to hide accounts.
• Users can reject account access on untrusted sites to prevent unsolicited transactions.

Long-term value-add

• Dapps could request specific account information based on user consent.
• Dapps could request specific user information based on user consent (uPort, DIDs).
• Dapps could request a specific network based on user consent.
• Dapps could request multiple instances of the above based on user consent.

Backwards compatibility

This proposal impacts dapp developers and requires that they request access to user accounts following the protocol outlined above. Similarly, this proposal impacts dapp browser developers and requires that they only expose user accounts following the protocol defined above.

Implementation

The MetaMask team has implemented the strategy described above.

Copyright

Copyright and related rights waived via CC0.