DSRoles

A DSAuthority for up to 256 roles

A role-driven authority for ds-auth which facilitates access to lists of user roles and capabilities. Works as a set of lookup tables for the canCall function to provide boolean answers as to whether a user is authorized to call a given function at given address.

The ability to check permissions in constant time is entirely due to the artificial constraint on the number of roles. 256 was chosen because this lets us abuse the large word size and cheap bitwise operations.

In the context of providing authority for DSAuth, a user is the msg.sender. DSRoles provides 3 different ways of permitting/forbidding function call access to users, with root access being the most permissive:

1. Root Users - any users added to the _root_users whitelist will be authorized to call any function regardless of what roles or capabilities might be defined.

2. Public Capabilities - public capabilities are global capabilities which apply to all users and take precedence over any user specific role-capabilities which might be defined.

3. Role Capabilities - capabilities which are associated with a particular role. Role capabilities are only checked if the user does not have root access and the capability is not public.

Roles are assigned to users by number:

uint8 owner_role = 0;
uint8 user_role = 1;

setUserRole(owner_address, owner_role, true);
setUserRole(user_address, user_role, true);

Capabilities can be assigned to anyone (public) or to a role permitting/forbidding access to a particular function at a given address:

address target = 0x123;  // code address

bytes4 withdraw_sig = bytes4(sha3("withdrawAll()"));
setRoleCapability(owner_role, target, withdraw_sig, true);
setRoleCapability(user_role, target, withdraw_sig, false);

bytes4 deposit_sig = bytes4(sha3("deposit(uint256)"));
setRoleCapability(user_role, target, deposit_sig, true);

Actions

setRootUser

grant root access to a given user (requires auth)

setUserRole

assign a role to given user (requires auth)

setPublicCapability

set public permissions for a given capability (requires auth)

setRoleCapability

set a capability for a given role (requires auth)