Concepts

Authorization and Grant

The x/authz module defines interfaces and messages grant authorizations to perform actions on behalf of one account to other accounts. The design is defined in the ADR 030.

A grant is an allowance to execute a Msg by the grantee on behalf of the granter. Authorization is an interface that must be implemented by a concrete authorization logic to validate and execute grants. Authorizations are extensible and can be defined for any Msg service method even outside of the module where the Msg method is defined. See the SendAuthorization example in the next section for more details.

Note: The authz module is different from the auth (authentication) module that is responsible for specifying the base transaction and account types.

+++ https://github.com/cosmos/cosmos-sdk/blob/v0.46.0-rc1/x/authz/authorizations.go#L11-L25

Built-in Authorizations

The Cosmos SDK x/authz module comes with following authorization types:

GenericAuthorization

GenericAuthorization implements the Authorization interface that gives unrestricted permission to execute the provided Msg on behalf of granter's account.

+++ https://github.com/cosmos/cosmos-sdk/blob/v0.46.0-rc1/proto/cosmos/authz/v1beta1/authz.proto#L13-L20

+++ https://github.com/cosmos/cosmos-sdk/blob/v0.46.0-rc1/x/authz/generic_authorization.go#L16-L29

msg stores Msg type URL.

SendAuthorization

SendAuthorization implements the Authorization interface for the cosmos.bank.v1beta1.MsgSend Msg. It takes a (positive) SpendLimit that specifies the maximum amount of tokens the grantee can spend. The SpendLimit is updated as the tokens are spent.

+++ https://github.com/cosmos/cosmos-sdk/blob/v0.46.0-rc1/proto/cosmos/bank/v1beta1/authz.proto#L10-L19

+++ https://github.com/cosmos/cosmos-sdk/blob/v0.46.0-rc1/x/bank/types/send_authorization.go#L23-L38

spend_limit keeps track of how many coins are left in the authorization.

StakeAuthorization

StakeAuthorization implements the Authorization interface for messages in the staking module. It takes an AuthorizationType to specify whether you want to authorise delegating, undelegating or redelegating (i.e. these have to be authorised seperately). It also takes a required MaxTokens that keeps track of a limit to the amount of tokens that can be delegated/undelegated/redelegated. If left empty, the amount is unlimited. Additionally, this Msg takes an AllowList or a DenyList, which allows you to select which validators you allow or deny grantees to stake with.

+++ https://github.com/cosmos/cosmos-sdk/blob/v0.46.0-rc1/proto/cosmos/staking/v1beta1/authz.proto#L10-L33

+++ https://github.com/cosmos/cosmos-sdk/blob/v0.46.0-rc1/x/staking/types/authz.go#L15-L35

Gas

In order to prevent DoS attacks, granting StakeAuthorizations with x/authz incurs gas. StakeAuthorization allows you to authorize another account to delegate, undelegate, or redelegate to validators. The authorizer can define a list of validators they allow or deny delegations to. The Cosmos SDK iterates over these lists and charge 10 gas for each validator in both of the lists.

Since the state maintaining a list for granter, grantee pair with same expiration, we are iterating over the list to remove the grant (incase of any revoke of paritcular msgType) from the list and we are charging 20 gas per iteration.

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