Add recipient checker logics to bank send (#526)

## Describe your changes and provide context
Allow checkers to be registered with bank send keeper so that certain
recipients can be blocked. For example, to block a temp address (created
by EVM module before address association) from receiving after its main
address is associated, one would register a checker as follows:
```
app.BankKeeper.RegisterRecipientChecker(func(ctx sdk.Context, recipient sdk.AccAddress) bool {
    castEvmAddress := common.BytesToAddress(recipient)
    _, isAssociated := app.EvmKeeper.GetSeiAddress(ctx, castEvmAddress)
    return !isAssociated
})
```

## Testing performed to validate your change
unit test

types/errors/errors.go

@@ -159,6 +159,9 @@ var (
 	// ErrEVMVMError defines an error for an evm vm error (eg. revert)
 	ErrEVMVMError = Register(RootCodespace, 45, "evm reverted")
 
+	// ErrInvalidRecipient defines an error for sending to disallowed recipients in bank
+	ErrInvalidRecipient = Register(RootCodespace, 46, "invalid bank recipient")
+
 	// ErrPanic is only set when we recover from a panic, so we know to
 	// redact potentially sensitive system info
 	ErrPanic = Register(UndefinedCodespace, 111222, "panic")

x/bank/keeper/keeper_test.go

@@ -1361,6 +1361,24 @@ func (suite *IntegrationTestSuite) TestSetDenomMetaData() {
 	suite.Require().Equal(metadata[1].GetDenomUnits()[1].GetAliases(), actualMetadata.GetDenomUnits()[1].GetAliases())
 }
 
+func (suite *IntegrationTestSuite) TestCanSendTo() {
+	app, ctx := suite.app, suite.ctx
+	badAddr := sdk.AccAddress([]byte("addr1_______________"))
+	goodAddr := sdk.AccAddress([]byte("addr2_______________"))
+	sourceAddr := sdk.AccAddress([]byte("addr3_______________"))
+	app.AccountKeeper.SetAccount(ctx, app.AccountKeeper.NewAccountWithAddress(ctx, badAddr))
+	app.AccountKeeper.SetAccount(ctx, app.AccountKeeper.NewAccountWithAddress(ctx, goodAddr))
+	app.AccountKeeper.SetAccount(ctx, app.AccountKeeper.NewAccountWithAddress(ctx, sourceAddr))
+	suite.Require().NoError(simapp.FundAccount(app.BankKeeper, ctx, sourceAddr, sdk.NewCoins(sdk.NewCoin("usei", sdk.NewInt(100)))))
+	checker := func(_ sdk.Context, addr sdk.AccAddress) bool { return !addr.Equals(badAddr) }
+	app.BankKeeper.RegisterRecipientChecker(checker)
+	amt := sdk.NewCoins(sdk.NewCoin("usei", sdk.NewInt(10)))
+	suite.Require().Nil(app.BankKeeper.SendCoins(ctx, sourceAddr, goodAddr, amt))
+	suite.Require().NotNil(app.BankKeeper.SendCoins(ctx, sourceAddr, badAddr, amt))
+	suite.Require().Nil(app.BankKeeper.SendCoinsAndWei(ctx, sourceAddr, goodAddr, sdk.OneInt(), sdk.ZeroInt()))
+	suite.Require().NotNil(app.BankKeeper.SendCoinsAndWei(ctx, sourceAddr, badAddr, sdk.OneInt(), sdk.ZeroInt()))
+}
+
 func (suite *IntegrationTestSuite) TestIterateAllDenomMetaData() {
 	app, ctx := suite.app, suite.ctx
 

x/bank/keeper/send.go

@@ -31,8 +31,11 @@ type SendKeeper interface {
 	IsSendEnabledCoins(ctx sdk.Context, coins ...sdk.Coin) error
 
 	BlockedAddr(addr sdk.AccAddress) bool
+	RegisterRecipientChecker(RecipientChecker)
 }
 
+type RecipientChecker = func(ctx sdk.Context, recipient sdk.AccAddress) bool
+
 var _ SendKeeper = (*BaseSendKeeper)(nil)
 var OneUseiInWei sdk.Int = sdk.NewInt(1_000_000_000_000)
 
@@ -47,20 +50,22 @@ type BaseSendKeeper struct {
 	paramSpace paramtypes.Subspace
 
 	// list of addresses that are restricted from receiving transactions
-	blockedAddrs map[string]bool
+	blockedAddrs      map[string]bool
+	recipientCheckers *[]RecipientChecker
 }
 
 func NewBaseSendKeeper(
 	cdc codec.BinaryCodec, storeKey sdk.StoreKey, ak types.AccountKeeper, paramSpace paramtypes.Subspace, blockedAddrs map[string]bool,
 ) BaseSendKeeper {
 
 	return BaseSendKeeper{
-		BaseViewKeeper: NewBaseViewKeeper(cdc, storeKey, ak),
-		cdc:            cdc,
-		ak:             ak,
-		storeKey:       storeKey,
-		paramSpace:     paramSpace,
-		blockedAddrs:   blockedAddrs,
+		BaseViewKeeper:    NewBaseViewKeeper(cdc, storeKey, ak),
+		cdc:               cdc,
+		ak:                ak,
+		storeKey:          storeKey,
+		paramSpace:        paramSpace,
+		blockedAddrs:      blockedAddrs,
+		recipientCheckers: &[]RecipientChecker{},
 	}
 }
 
@@ -232,6 +237,9 @@ func (k BaseSendKeeper) SubUnlockedCoins(ctx sdk.Context, addr sdk.AccAddress, a
 // AddCoins increase the addr balance by the given amt. Fails if the provided amt is invalid.
 // It emits a coin received event.
 func (k BaseSendKeeper) AddCoins(ctx sdk.Context, addr sdk.AccAddress, amt sdk.Coins, checkNeg bool) error {
+	if !k.CanSendTo(ctx, addr) {
+		return sdkerrors.ErrInvalidRecipient
+	}
 	if !amt.IsValid() {
 		return sdkerrors.Wrap(sdkerrors.ErrInvalidCoins, amt.String())
 	}
@@ -360,6 +368,9 @@ func (k BaseSendKeeper) SubWei(ctx sdk.Context, addr sdk.AccAddress, amt sdk.Int
 }
 
 func (k BaseSendKeeper) AddWei(ctx sdk.Context, addr sdk.AccAddress, amt sdk.Int) (err error) {
+	if !k.CanSendTo(ctx, addr) {
+		return sdkerrors.ErrInvalidRecipient
+	}
 	if amt.Equal(sdk.ZeroInt()) {
 		return nil
 	}
@@ -405,6 +416,19 @@ func (k BaseSendKeeper) SendCoinsAndWei(ctx sdk.Context, from sdk.AccAddress, to
 	return nil
 }
 
+func (k BaseSendKeeper) RegisterRecipientChecker(rc RecipientChecker) {
+	*k.recipientCheckers = append(*k.recipientCheckers, rc)
+}
+
+func (k BaseSendKeeper) CanSendTo(ctx sdk.Context, recipient sdk.AccAddress) bool {
+	for _, rc := range *k.recipientCheckers {
+		if !rc(ctx, recipient) {
+			return false
+		}
+	}
+	return true
+}
+
 func SplitUseiWeiAmount(amt sdk.Int) (sdk.Int, sdk.Int) {
 	return amt.Quo(OneUseiInWei), amt.Mod(OneUseiInWei)
 }