From c5e87d05adf69a1e15440e5f81622450190c4fc7 Mon Sep 17 00:00:00 2001 From: Ricardo Guilherme Schmidt Date: Wed, 8 Jan 2020 23:59:47 -0300 Subject: [PATCH] Automatically merged updates to draft EIP(s) 1077 (#2454) Hi, I'm a bot! This change was automatically merged because: - It only modifies existing Draft or Last Call EIP(s) - The PR was approved or written by at least one author of each modified EIP - The build is passing --- EIPS/eip-1077.md | 258 ++++++++++++++++++++++++----------------------- 1 file changed, 134 insertions(+), 124 deletions(-) diff --git a/EIPS/eip-1077.md b/EIPS/eip-1077.md index 73a7800df7919f..d63e7f39fb8751 100644 --- a/EIPS/eip-1077.md +++ b/EIPS/eip-1077.md @@ -1,107 +1,159 @@ --- eip: 1077 -title: Executable Signed Messages refunded by the contract +title: Gas relay for contract calls author: Alex Van de Sande , Ricardo Guilherme Schmidt (@3esmit) discussions-to: https://ethereum-magicians.org/t/erc1077-and-1078-the-magic-of-executable-signed-messages-to-login-and-do-actions/351 status: Draft type: Standards Track category: ERC created: 2018-05-04 -requires: 725, 191 +requires: 20, 191, 1271, 1344 --- + ## Simple Summary -Allowing users to sign messages to show intent of execution, but allowing a third party relayer to execute them is an emerging pattern being used in many projects. Standardizing a common format for them, as well as a way in which the user allows the transaction to be paid in tokens, gives app developers a lot of flexibility and can become the main way in which app users interact with the Blockchain. +A standard interface for gas abstraction in top of smart contracts. + +Allows users to offer [EIP-20] token for paying the gas used in a call. ## Abstract -User pain points: +A main barrier for adoption of DApps is the requirement of multiple tokens for executing in chain actions. Allowing users to sign messages to show intent of execution, but allowing a third party relayer to execute them can circumvent this problem, while ETH will always be required for ethereum transactions, it's possible for smart contract to take [EIP-191] signatures and forward a payment incentive to an untrusted party with ETH for executing the transaction. -* users don't want to think about ether -* users don't want to think about backing up private keys or seed phrases -* users want to be able to pay for transactions using what they already have on the system, be apple pay, xbox points or even a credit card -* Users don’t want to sign a new transaction at every move -* Users don’t want to download apps/extensions (at least on the desktop) to connect to their apps +## Motivation -App developer pain points: -* Many apps use their own token and would prefer to use those as the main accounting -* Apps want to be able to have apps in multiple platforms without having to share private keys between devices or have to spend transaction costs moving funds between them -* Token developers want to be able for their users to be able to move funds and pay fees in the token -* While the system provides fees and incentives for miners, there are no inherent business model for wallet developers (or other apps that initiate many transactions) +Standardizing a common format for them, as well as a way in which the user allows the transaction to be paid in tokens, gives app developers a lot of flexibility and can become the main way in which app users interact with the Blockchain. + + +## Specification + +### Methods + +#### executeGasRelay + +Executes `_execData` with current `lastNonce()` and pays `msg.sender` the gas used in specified `_gasToken`. + +```solidity +function executeGasRelay(bytes calldata _execData, uint256 _gasPrice, uint256 _gasLimit, address _gasToken, bytes calldata _signature) external; +``` + +### executeGasRelayMsg + +Returns the `executeGasRelay` message used for signing messages.. + +```solidity +function executeGasRelayMsg(uint256 _nonce, bytes memory _execData, uint256 _gasPrice, uint256 _gasLimit, address _gasToken, address _gasRelayer) public pure returns (bytes memory); +``` + +#### executeGasRelayERC191Msg + +Returns the [EIP-191] of `executeGasRelayMsg` used for signing messages and for verifying the execution. + +```solidity +function executeGasRelayERC191Msg(uint256 _nonce, bytes memory _execData, uint256 _gasPrice, uint256 _gasLimit, address _gasToken, address _gasRelayer) public view returns (bytes memory); +``` + +#### lastNonce + +Returns the current nonce for the gas relayed messages. -Using signed messages, specially combined with an identity contract that holds funds, and multiple disposable ether-less keys that can sign on its behalf, solves many of these pain points. +```solidity +function lastNonce() public returns (uint nonce); +``` -### Implementation +### Signed Message -The signed messages require the following fields: +The signed message require the following fields: -* To: the target contract the transaction will be executed upon -* From: the account that will be executed on behalf of -* Value: the amount in ether to be sent -* Data: the bytecode to be executed -* Nonce: a nonce *or* a timestamp -* GasToken: a token in which the gas will be paid (leave 0 for ether) -* Gasprice: the gas price (paid in the selected token) -* GasLimit: the maximum gas to be paid +* Nonce: A nonce *or* a timestamp; +* Execute Data: the bytecode to be executed by the account contract; +* Gas Price: The gas price (paid in the selected token); +* Gas Limit: The gas reserved to the relayed execution; +* Gas Token: A token in which the gas will be paid (leave 0 for ether); +* Gas Relayer: the authorized relayer for this message. #### Signing the message -In order to be compliant, the transaction **MUST** request to sign a messageHash that is a concatenation of multiple fields, plus one final field `extraData` that can be left blank but is added for forward compatibility. +The message **MUST** be signed as [EIP-191] standard, and the called contract m**MUST**ust also implement [EIP-1271] which must validate the signed messages. -The fields **MUST** be concatenated in this order: +Messages **MUST** be signed by the owner of the account contract executing. If the owner is a contract, it must implement [EIP-1271] interface and forward validation to it. +In order to be compliant, the transaction **MUST** request to sign a "messageHash" that is a concatenation of multiple fields. + +The fields **MUST** be constructed as this method: + +The first and second fields are to make it [EIP-191] compliant. Starting a transaction with `byte(0x19)` ensure the signed data from being a [valid ethereum transaction](https://github.com/ethereum/wiki/wiki/RLP). The second argument is a version control byte. The third being the validator address (the account contract address) according to version 0 of [EIP-191]. The remaining arguments being the application specific data for the gas relay: chainID as per [EIP-1344], execution nonce, execution data, agreed gas Price, gas limit of gas relayed call, gas token to pay back and gas relayer authorized to receive reward. + +The [EIP-191] message must be constructed as following: ```solidity keccak256( - byte(0x19), - byte(0), - from, - to, - value, - dataHash, - nonce, - gasPrice, - gasLimit, - gasToken, - callPrefix, - operationType, - extraHash -); + abi.encodePacked( + byte(0x19), //ERC-191 - the initial 0x19 byte + byte(0x0), //ERC-191 - the version byte + address(this), //ERC-191 - version data (validator address) + chainID, + bytes4( + keccak256("executeGasRelay(uint256,bytes,uint256,uint256,address,address)") + ), + _nonce, + _execData, + _gasPrice, + _gasLimit, + _gasToken, + _gasRelayer + ) +) ``` -The first and second fields are to make it [ERC191](https://eips.ethereum.org/EIPS/eip-191) compliant. Starting a transaction with byte(0x19) ensure the signed data from being a [valid ethereum transaction](https://github.com/ethereum/wiki/wiki/RLP). The second argument is a version control byte. +## Rationale -The `from` field will always be the contract executing the code (`address(this)`), and the `callPrefix` is the 4 byte standard prefix of the function to be called in the `from` contract. This guarantees that a signed message can be only executed in a single instance. - -`operationType` type will define what sort of operation will be executed (in assembly): 0 for a standard `call`, 1 for a `DelegateCall` and 0 for a `create` opcode. These can be extended in the future. +User pain points: -#### Backwards and forwards capability: +* users don't want to think about ether +* users don't want to think about backing up private keys or seed phrases +* users want to be able to pay for transactions using what they already have on the system, be apple pay, xbox points or even a credit card +* Users don’t want to sign a new transaction at every move +* Users don’t want to download apps/extensions (at least on the desktop) to connect to their apps -Not all executable signed messages contracts will have the same requirements, therefore some fields are optional. Fields `byte(0x19)`, `byte(0)`, `from`, `to`, `value`, `dataHash` are **obligatory** while `nonce`, `gasPrice`, `gasLimit`, `gasToken`, `callPrefix`, `operationType` are optional, but must be hashed in this order. +App developer pain points: +* Many apps use their own token and would prefer to use those as the main accounting +* Apps want to be able to have apps in multiple platforms without having to share private keys between devices or have to spend transaction costs moving funds between them +* Token developers want to be able for their users to be able to move funds and pay fees in the token +* While the system provides fees and incentives for miners, there are no inherent business model for wallet developers (or other apps that initiate many transactions) -Regardless of which fields you use, in your contract you **must** accept an extraHash that is always hashed at the end. This is done to increase future compatibility of the standard: solidity's keccak treats `keccak(a, b, c, d, e, f)` as identical to `keccak(a, b, concat(c, d, e, f)`. therefore by adding an extra field in the end that can be ignored by your contract, you allow it to be compatible with the same standard as other message standards that use it to sign it. +Using signed messages, specially combined with an account contract that holds funds, and multiple disposable ether-less keys that can sign on its behalf, solves many of these pain points. +### Multiple signatures -#### Multiple signatures +More than one signed transaction with the same parameter can be executed by this function at the same time, by passing all signatures in the `messageSignatures` field. That field will split the signature in multiple 72 character individual signatures and evaluate each one. This is used for cases in which one action might require the approval of multiple parties, in a single transaction. -If multiple signatures are required, then all signed messageHashes should then be *ordered by account* and sent to the receiving contract which then will execute the following actions: +If multiple signatures are required, then all signatures should then be *ordered by account* and the account contract should implement signatures checks locally (`JUMP`) on [EIP-1271] interface which might forward (`STATIC_CALL`) the [EIP-1271] signature check to owner contract. -#### keep track of nonces: +### Keep track of nonces: +Note that `executeGasRelay` function does not take a `_nonce` as parameter. The contract knows what is the current nonce, and can only execute the transactions in order, therefore there is no reason Nonces work similarly to normal ethereum transactions: a transaction can only be executed if it matches the last nonce + 1, and once a transaction has occurred, the `lastNonce` will be updated to the current one. This prevents transactions to be executed out of order or more than once. -Contracts should accept transactions without nonce (nonce = 0). The contract then must keep the full hash of the transaction to prevent it from being replayed. This option allows contracts to have more flexibilities as you can sign a transaction that can be executed out of order or not at all, but it uses more memory for each transaction. It can be used, for instance, for transactions that the user wants to schedule in the future but cannot know its future nonce, or transactions that are made for state channel contracts that are not guaranteed to be executed or are only executed when there's some dispute. - -### execute transaction +Contracts may accept transactions without nonce (nonce = 0). The contract then must keep the full hash of the transaction to prevent it from being replayed. This would allows contracts to have more flexibilities as you can sign a transaction that can be executed out of order or not at all, but it uses more memory for each transaction. It can be used, for instance, for transactions that the user wants to schedule in the future but cannot know its future nonce, or transactions that are made for state channel contracts that are not guaranteed to be executed or are only executed when there's some dispute. -The contract must then verify the signatures of the accounts and check if the public keys match accounts that are authorized to do what they intend to do: depending on the contract implementation, some contracts might require multiple key signatures, other might have specific actions few accounts are authorized to do. +### Execute transaction -If an identity, then, the contract should implement ERC725 identity management levels: a key must be at least an `action` key to have authorization to demand any call to external contracts, and a `management` key to demand calls to the contract itself. +After signature validation, the evaluation of `_execBytes` is up to the account contract implementation, it's role of the wallet to properly use the account contract and it's gas relay method. +A common pattern is to expose an interface which can be only called by the contract itself. The `_execBytes` could entirely forward the call in this way, as example: `address(this).call.gas(_gasLimit)(_execData);` +Where `_execData` could call any method of the contract itself, for example: -If the signing accounts are authorized to do so, the contract must execute the requested action. If the current contract is the same as `from` field, then if can simply execute the actions by calling `_to.call.value(_value)(_data)`. +- `call(address to, uint256 value, bytes data)`: allow any type of ethereum call be performed; +- `create(uint256 value, bytes deployData)`: allows create contract +- `create2(uint256 value, bytes32 salt, bytes deployData)`: allows create contract with deterministic address +- `approveAndCall(address token, address to, uint256 value, bytes data)`: allows safe approve and call of an ERC20 token. +- `delegatecall(address codeBase, bytes data)`: allows executing code stored on other contract +- `changeOwner(address newOwner)`: Some account contracts might allow change of owner +- `foo(bytes bar)`: Some account contracts might have custom methods of any format. -How the contract interprets the intended action depends on its purpose. For instance a token contract can decide to implement it in a way that interprets all actions as token transfers, and uses the `value` to mean token value and `bytecode` as the data to pass to the recipient contract +The standardization of account contracts is not scope of this ERC, and is presented here only for illustration on possible implementations. +Using a self call to evaluate `_execBytes` is not mandatory, depending on the account contract logic, the evaluation could be done locally. ### Gas accounting and refund @@ -113,65 +165,29 @@ If the executed transaction fails internally, nonces should still be updated and Contracts are not obligated to support ether or any other token they don’t want and can be implemented to only accept refunds in a few tokens of their choice. -**Deployers of transactions have no guarantees that the contract they are interacting with correctly implements the standard and they will be reimbursed for gas, so they should maintain their own white/blacklists of contracts to support, as well as keep track of which tokens and for which gasPrice they’re willing to deploy transactions.** - -### Supported functions - -` -executeSigned( - address to, - address from, - uint256 value, - bytes data, - uint nonce, - uint gasPrice, - uint gasLimit, - address gasToken, - operationType, - extraHash, - bytes messageSignatures) -` - -Executes the signed message. Execution usually means that a contract will execute a `call` to the `to` address, with `value` amount of ether and `data` as its data. But in some special cases, a token can decide instead to interpret it specifically as executing a `transferAndCall(to,from,data)` or the equivalent. +### Usage examples -More than one signed transaction with the same parameter can be executed by this function at the same time, by passing all signatures in the `messageSignatures` field. That field will split the signature in multiple 72 character individual signatures and evaluate each one. This is used for cases in which one action might require the approval of multiple parties, in a single transaction. - -` -gasEstimate( - address to, - address from, - uint256 value, - bytes data, - uint nonce, - uint gasPrice, - uint gasLimit, - address gasToken, - operationType, - extraHash - bytes messageSignatures) - returns ( - bool canExecute, - uint gasCost) -` -A read only function that checks if the transaction will be executable and how much gas it’s expected to cost. - -`lastNonce() public returns (uint nonce)` -`lastTimestamp() public returns (uint nonce)` +This scheme opens up a great deal of possibilities on interaction as well as different experiments on business models: -Both are simple read only functions that return the last used Nonce and last used timestamp. +* Apps can create individual identities contract for their users which holds the actual funds and then create a different private key for each device they log into. Other apps can use the same identity and just ask to add permissioned public keys to manage the device, so that if one individual key is lost, no ether is lost. +* An app can create its own token and only charge their users in its internal currency for any ethereum transaction. The currency units can be rounded so it looks more similar to to actual amount of transactions: a standard transaction always costs 1 token, a very complex transaction costs exactly 2, etc. Since the app is the issuer of the transactions, they can do their own Sybil verifications and give a free amount of currency units to new users to get them started. +* A game company creates games with a traditional monthly subscription, either by credit card or platform-specific microtransactions. Private keys never leave the device and keep no ether and only the public accounts are sent to the company. The game then signs transactions on the device with gas price 0, sends them to the game company which checks who is an active subscriber and batches all transactions and pays the ether themselves. If the company goes bankrupt, the gamers themselves can set up similar subscription systems or just increase the gas price. End result is a **ethereum based game in which gamers can play by spending apple, google or xbox credits**. +* A standard token is created that doesn’t require its users to have ether, and instead allows tokens to be transferred by paying in tokens. A wallet is created that signs messages and send them via whisper to the network, where other nodes can compete to download the available transactions, check the current gas price, and select those who are paying enough tokens to cover the cost. **The result is a token that the end users never need to keep any ether and can pay fees in the token itself.** +* A DAO is created with a list of accounts of their employees. Employees never need to own ether, instead they sign messages, send them to whisper to a decentralized list of relayers which then deploy the transactions. The DAO contract then checks if the transaction is valid and sends ether to the deployers. Employees have an incentive not to use too many of the companies resources because they’re identifiable. The result is that the users of the DAO don't need to keep ether, and **the contract ends up paying for it's own gas usage**. -`requiredSignatures(uint type) returns (uint)` +## Backwards Compatibility -A function which returns the amount of signatures that are required for a given type of action (types being 1 = Management and 2 = Action). +There is no issues with backwards compatibility, however for future upgrades, as `_execData` contains arbitrary data evaluated by the account contract, it's up to the contract to handle properly this data and therefore contracts can gas relay any behavior with the current interface. -`event ExecutedSigned(bytes32 signHash, uint nonce, bool success);` +## Test Cases -Whenever a new transaction is executed it **must** emit an event with the signHash, nonce and either the transaction was successfully executed or not. Apps that are waiting for a transaction to be executed should subscribe to the identity and watch this event to see if their transaction was successful. If a different signHash is executed with an equal or higher nonce, it means that your transaction has been replaced. +TBD ## Implementation -One initial implementation of such a contract can be found at [the Identity Gas Relay at the Status repository](https://github.com/status-im/contracts/blob/73-economic-abstraction/contracts/identity/IdentityGasRelay.sol) -## Similar implementations +One initial implementation of such a contract can be found at [Status.im account-contracts repository](https://github.com/status-im/account-contracts/blob/develop/contracts/account/AccountGasAbstract.sol) + +### Similar implementations The idea of using signed messages as executable intent has been around for a while and many other projects are taking similar approaches, which makes it a great candidate for a standard that guarantees interoperability: @@ -187,26 +203,20 @@ The idea of using signed messages as executable intent has been around for a whi Swarm city uses a similar proposition for etherless transactions, called [Gas Station Service](https://github.com/swarmcity/SCLabs-gasstation-service), but it's a different approach. Instead of using signed messages, a traditional ethereum transaction is signed on an etherless account, the transaction is then sent to a service that immediately sends the exact amount of ether required and then publishes the transaction. +## Security Considerations -## Areas for improvements +Deployers of transactions (relayers) should be able to call untrusted contracts, which provides no guarantees that the contract they are interacting with correctly implements the standard and they will be reimbursed for gas. To prevent being fooled by bad implementations, relayers must **estimate the outcome of a transaction**, and only include/sign transactions which have a desired outcome. -This ERC inherits all it's permission systems from ERC720 Identity, which has very basic levels of authorization (can call contract itself, can make external calls, cannot make any calls) and a simple generic multisig. Ideally we need a more comprehensive standard for authorizations, that enables, for instance, that a single key can only make calls to a specific contract, or specific functions. Also, the amount of signatures required to do an action could be variable, maybe a single key could have a limit on how much value it can spend in a single day, requiring more signatures to move higher amounts (how to properly measure the value of a token or NFT transfer is another matter entirely). - -## Usage examples - -This scheme opens up a great deal of possibilities on interaction as well as different experiments on business models: - -* Apps can create individual identities contract for their users which holds the actual funds and then create a different private key for each device they log into. Other apps can use the same identity and just ask to add permissioned public keys to manage the device, so that if one individual key is lost, no ether is lost. -* An app can create its own token and only charge their users in its internal currency for any ethereum transaction. The currency units can be rounded so it looks more similar to to actual amount of transactions: a standard transaction always costs 1 token, a very complex transaction costs exactly 2, etc. Since the app is the issuer of the transactions, they can do their own Sybil verifications and give a free amount of currency units to new users to get them started. -* A game company creates games with a traditional monthly subscription, either by credit card or platform-specific microtransactions. Private keys never leave the device and keep no ether and only the public accounts are sent to the company. The game then signs transactions on the device with gas price 0, sends them to the game company which checks who is an active subscriber and batches all transactions and pays the ether themselves. If the company goes bankrupt, the gamers themselves can set up similar subscription systems or just increase the gas price. End result is a **ethereum based game in which gamers can play by spending apple, google or xbox credits**. -* A standard token is created that doesn’t require its users to have ether, and instead allows tokens to be transferred by paying in tokens. A wallet is created that signs messages and send them via whisper to the network, where other nodes can compete to download the available transactions, check the current gas price, and select those who are paying enough tokens to cover the cost. **The result is a token that the end users never need to keep any ether and can pay fees in the token itself.** -* A DAO is created with a list of accounts of their employees. Employees never need to own ether, instead they sign messages, send them to whisper to a decentralized list of relayers which then deploy the transactions. The DAO contract then checks if the transaction is valid and sends ether to the deployers. Employees have an incentive not to use too many of the companies resources because they’re identifiable. The result is that the users of the DAO don't need to keep ether, and **the contract ends up paying for it's own gas usage**. - -### References - -* [Universal Logins talk at UX Unconf, Toronto](https://www.youtube.com/watch?v=qF2lhJzngto) +Is also interest of relayers to maintaining a private reputation of contracts they interact with, as well as keep track of which tokens and for which `gasPrice` they’re willing to deploy transactions. ## Copyright Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/). +## References + +* [Universal Logins talk at UX Unconf, Toronto](https://www.youtube.com/watch?v=qF2lhJzngto) +[EIP-20]: https://eips.ethereum.org/EIPS/eip-20 +[EIP-191]: https://eips.ethereum.org/EIPS/eip-191 +[EIP-1271]: https://eips.ethereum.org/EIPS/eip-1271 +[EIP-1344]: https://eips.ethereum.org/EIPS/eip-1344