# DAuth Access Delegation Standard

# 简要说明

DAuth is a standard interface for accessing authorization delegation between smart contracts and users.

# 摘要

The DAuth protocol defines a set of standard API allowing identity delegations between smart contracts without the user's private key. Identity delegations include accessing and operating a user's data and assets contained in the delegated contracts.

# 动机

The inspiration for designing DAuth comes from OAuth protocol that is extensively used in web applications. But unlike the centralized authorization of OAuth, DAuth works in a distributed manner, thus providing much more reliability and generality.

# 规范

Rationale

Resource owner: the authorizer

Resource contract: the contract providing data and operators

API: the resource contract APIs that the grantee contract can invoke

Client contract: the grantee contract using authorization to access and operate the data

Grantee request: the client contract calls the resource contract with the authorizer authorization

AuthInfo

struct AuthInfo {
    string[] funcNames;
    uint expireAt;
}

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Required - The struct contains user authorization information

funcNames: a list of function names callable by the granted contract
expireAt: the authorization expire timestamp in seconds

userAuth

mapping(address => mapping(address => AuthInfo)) userAuth;

Required - userAuth maps (authorizer address, grantee contract address) pair to the user’s authorization AuthInfo object

callableFuncNames

string[] callableFuncNames;

Required - All methods that are allowed other contracts to call

The callable function MUST verify the grantee’s authorization

updateCallableFuncNames

function updateCallableFuncNames(string _invokes) public returns (bool success);

Optional - Update the callable function list for the client contract by the resource contract's administrator

_invokes: the invoke methods that the client contract can call
return: Whether the callableFuncNames is updated or not
This method MUST return success or throw, no other outcomes can be possible

verify

function verify(address _authorizer, string _invoke) internal returns (bool success);

Required - check the invoke method authority for the client contract

_authorizer: the user address that the client contract agents
_invoke: the invoke method that the client contract wants to call
return: Whether the grantee request is authorized or not
This method MUST return success or throw, no other outcomes can be possible

grant

function grant(address _grantee, string _invokes, uint _expireAt) public returns (bool success);

Required - delegate a client contract to access the user's resource

_grantee: the client contract address
_invokes: the callable methods that the client contract can access. It is a string which contains all function names split by spaces
_expireAt: the authorization expire timestamp in seconds
return: Whether the grant is successful or not
This method MUST return success or throw, no other outcomes can be possible
A successful grant MUST fire the Grant event(defined below)

regrant

function regrant(address _grantee, string _invokes, uint _expireAt) public returns (bool success);

Optional - alter a client contract's delegation

revoke

function revoke(address _grantee) public returns (bool success);

Required - delete a client contract's delegation

_grantee: the client contract address
return: Whether the revoke is successful or not
A successful revoke MUST fire the Revoke event(defined below).

Grant

event Grant(address _authorizer, address _grantee, string _invokes, uint _expireAt);

This event MUST trigger when the authorizer grant a new authorization when grant or regrant processes successfully

Revoke

event Revoke(address _authorizer, address _grantee);

This event MUST trigger when the authorizer revoke a specific authorization successfully

Callable Resource Contract Functions

All public or external functions that are allowed the grantee to call MUST use overload to implement two functions: The First one is the standard method that the user invokes directly, the second one is the grantee methods of the same function name with one more authorizer address parameter.

Example:

function approve(address _spender, uint256 _value) public returns (bool success) {
    return _approve(msg.sender, _spender, _value);
}

function approve(address _spender, uint256 _value, address _authorizer) public returns (bool success) {
    verify(_authorizer, "approve");

    return _approve(_authorizer, _spender, _value);
}

function _approve(address sender, address _spender, uint256 _value) internal returns (bool success) {
    allowed[sender][_spender] = _value;
    emit Approval(sender, _spender, _value);
    return true;
}

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# 原理阐述

Current Limitations

The current design of many smart contracts only considers the user invokes the smart contract functions by themselves using the private key. However, in some case, the user wants to delegate other client smart contracts to access and operate their data or assets in the resource smart contract. There isn’t a common protocol to provide a standard delegation approach.

Rationale

On the Ethereum platform, all storage is transparent and the msg.sender is reliable. Therefore, the DAuth don't need an access_token like OAuth. DAuth just recodes the users' authorization for the specific client smart contract's address. It is simple and reliable on the Ethereum platform.

# 向后兼容

This EIP introduces no backward compatibility issues. In the future, the new version protocol has to keep these interfaces.

# 实现

Following is the DAuth Interface implementation. Furthermore, the example implementations of EIP20 Interface and ERC-DAuth Interface are also provided. Developers can easily implement their own contracts with ERC-DAuth Interface and other EIP.

ERC-DAuth Interface implementation is available at:

https://github.com/DIA-Network/ERC-DAuth/blob/master/ERC-DAuth-Interface.sol
Example implementation with EIP20 Interface and ERC-DAuth Interface is available at:

https://github.com/DIA-Network/ERC-DAuth/blob/master/eip20-dauth-example/EIP20DAuth.sol