# x/auth

The `x/auth` module is responsible for specifying the base transaction and
account types for an application, as well as AnteHandler and authentication logic.

## Usage

1. Import the module.

   ```go
   import (
       "github.com/cosmos/cosmos-sdk/x/auth"
   )
   ```

2. Add `AppModuleBasic` to your `ModuleBasics`.

    ```go
    var (
      ModuleBasics = module.NewBasicManager(
        // ...
        auth.AppModuleBasic{},
      }
    )
    ```

3. Create the module's parameter subspace in your application constructor.

   ```go
   func NewApp(...) *App {
     // ...
     app.subspaces[auth.ModuleName] = app.ParamsKeeper.Subspace(auth.DefaultParamspace)
   }
   ```

4. Create the keeper.

   ```go
   func NewApp(...) *App {
      // ...
      app.AccountKeeper = auth.NewAccountKeeper(
       app.cdc, keys[auth.StoreKey], app.subspaces[auth.ModuleName], auth.ProtoBaseAccount,
      )
   }
   ```

5. Add the `x/auth` module to the app's `ModuleManager`.

   ```go
   func NewApp(...) *App {
     // ...
     app.mm = module.NewManager(
       // ...
       auth.NewAppModule(app.AccountKeeper),
       // ...
     )
   }
   ```

6. Set the `x/auth` module genesis order.

   ```go
   func NewApp(...) *App {
     // ...
     app.mm.SetOrderInitGenesis(..., auth.ModuleName, ...)
   }
   ```

7. Add the `x/auth` module to the simulation manager (if you have one set).

   ```go
   func NewApp(...) *App {
     // ...
     app.sm = module.NewSimulationManager(
       // ...
       auth.NewAppModule(app.AccountKeeper),
       // ...
     )
   }

8. Set the `AnteHandler` if you're using the default provided by `x/auth`. Note,
the default `AnteHandler` provided by the `x/auth` module depends on the `x/supply`
module.

   ```go
   func NewApp(...) *App {
     app.SetAnteHandler(ante.NewAnteHandler(
       app.AccountKeeper,
       app.SupplyKeeper,
       auth.DefaultSigVerificationGasConsumer,
     ))
   }
   ```

### Vesting Accounts

The `x/auth` modules also defines a few standard vesting account types under the
`vesting` sub-package. In order to get your application to automatically support
these in terms of encoding and decoding, you must register the types with your
application Amino codec.

Where ever you define the application `Codec`, be sure to register types via:

```go
import (
    "github.com/cosmos/cosmos-sdk/x/auth/vesting"
)

func MakeCodec() *codec.Codec {
  var cdc = codec.New()
  
  // ...
  vesting.RegisterCodec(cdc)
  // ...
  
  return cdc
}
```

## Genesis

The `x/auth` module defines its genesis state as follows:

```go
type GenesisState struct {
  Params   Params                   `json:"params" yaml:"params"`
  Accounts exported.GenesisAccounts `json:"accounts" yaml:"accounts"`
}
```

Which relies on the following types:

```go
type Account interface {
  GetAddress() sdk.AccAddress
  SetAddress(sdk.AccAddress) error
  GetPubKey() crypto.PubKey
  SetPubKey(crypto.PubKey) error
  GetAccountNumber() uint64
  SetAccountNumber(uint64) error
  GetSequence() uint64
  SetSequence(uint64) error
  GetCoins() sdk.Coins
  SetCoins(sdk.Coins) error
  SpendableCoins(blockTime time.Time) sdk.Coins
  String() string
}

type Params struct {
  MaxMemoCharacters      uint64 `json:"max_memo_characters" yaml:"max_memo_characters"`
  TxSigLimit             uint64 `json:"tx_sig_limit" yaml:"tx_sig_limit"`
  TxSizeCostPerByte      uint64 `json:"tx_size_cost_per_byte" yaml:"tx_size_cost_per_byte"`
  SigVerifyCostED25519   uint64 `json:"sig_verify_cost_ed25519" yaml:"sig_verify_cost_ed25519"`
  SigVerifyCostSecp256k1 uint64 `json:"sig_verify_cost_secp256k1" yaml:"sig_verify_cost_secp256k1"`
}
```

## Client

### CLI

The `x/auth` module provides various auxiliary CLI commands and a few that are
part of the module itself via the `ModuleManager`. The commands that are part of
the module itself are defined below:

1. Query an account.

   ```shell
   app q auth account [address] [...flags]
   ```

2. Sign an unsigned transaction using a single signature.

   ```shell
   app tx auth sign [file]
   ```

3. Sign an unsigned transaction using a multisig.

   ```shell
   app tx auth multisign [file] [name] [[signature]...]
   ```

### REST

The `x/auth` module provides various auxiliary REST handlers and a few that are
part of the module itself via the `ModuleManager`. The endpoints that are part of
the module itself are defined below:

1. Query an account.

   | Method | Path                     |
   | :----- | :----------------------- |
   | `GET` | `/auth/accounts/{address}` |