rpc: add /check_tx endpoint (#5017)

Closes #4549

CHANGELOG_PENDING.md

@@ -87,6 +87,7 @@ Friendly reminder, we have a [bug bounty program](https://hackerone.com/tendermi
 - [rpc] \#4979 Support EXISTS operator in `/tx_search` query (@melekes)
 - [p2p] \#4981 Expose `SaveAs` func on NodeKey (@melekes)
 - [evidence] [#4821](https://github.com/tendermint/tendermint/pull/4821) Amnesia evidence can be detected, verified and committed (@cmwaters)
+- [rpc] \#5017 Add `/check_tx` endpoint to check transactions without executing them or adding them to the mempool (@melekes)
 
 ### IMPROVEMENTS:
 

light/rpc/client.go

@@ -144,6 +144,10 @@ func (c *Client) NumUnconfirmedTxs() (*ctypes.ResultUnconfirmedTxs, error) {
 	return c.next.NumUnconfirmedTxs()
 }
 
+func (c *Client) CheckTx(tx types.Tx) (*ctypes.ResultCheckTx, error) {
+	return c.next.CheckTx(tx)
+}
+
 func (c *Client) NetInfo() (*ctypes.ResultNetInfo, error) {
 	return c.next.NetInfo()
 }

mempool/clist_mempool.go

@@ -706,9 +706,9 @@ func (cache *mapTxCache) Push(tx types.Tx) bool {
 
 	if cache.list.Len() >= cache.size {
 		popped := cache.list.Front()
-		poppedTxHash := popped.Value.([sha256.Size]byte) //nolint:staticcheck // SA5011: possible nil pointer dereference
-		delete(cache.cacheMap, poppedTxHash)
 		if popped != nil {
+			poppedTxHash := popped.Value.([sha256.Size]byte)
+			delete(cache.cacheMap, poppedTxHash)
 			cache.list.Remove(popped)
 		}
 	}

node/node.go

@@ -958,7 +958,8 @@ func (n *Node) ConfigureRPC() error {
 		return fmt.Errorf("can't get pubkey: %w", err)
 	}
 	rpccore.SetEnvironment(&rpccore.Environment{
-		ProxyAppQuery: n.proxyApp.Query(),
+		ProxyAppQuery:   n.proxyApp.Query(),
+		ProxyAppMempool: n.proxyApp.Mempool(),
 
 		StateDB:        n.stateDB,
 		BlockStore:     n.blockStore,

proxy/app_conn.go

@@ -27,6 +27,7 @@ type AppConnMempool interface {
 	Error() error
 
 	CheckTxAsync(types.RequestCheckTx) *abcicli.ReqRes
+	CheckTxSync(types.RequestCheckTx) (*types.ResponseCheckTx, error)
 
 	FlushAsync() *abcicli.ReqRes
 	FlushSync() error
@@ -125,6 +126,10 @@ func (app *appConnMempool) CheckTxAsync(req types.RequestCheckTx) *abcicli.ReqRe
 	return app.appConn.CheckTxAsync(req)
 }
 
+func (app *appConnMempool) CheckTxSync(req types.RequestCheckTx) (*types.ResponseCheckTx, error) {
+	return app.appConn.CheckTxSync(req)
+}
+
 //------------------------------------------------
 // Implements AppConnQuery (subset of abcicli.Client)
 

rpc/client/http/http.go

@@ -288,6 +288,15 @@ func (c *baseRPCClient) NumUnconfirmedTxs() (*ctypes.ResultUnconfirmedTxs, error
 	return result, nil
 }
 
+func (c *baseRPCClient) CheckTx(tx types.Tx) (*ctypes.ResultCheckTx, error) {
+	result := new(ctypes.ResultCheckTx)
+	_, err := c.caller.Call("check_tx", map[string]interface{}{"tx": tx}, result)
+	if err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
 func (c *baseRPCClient) NetInfo() (*ctypes.ResultNetInfo, error) {
 	result := new(ctypes.ResultNetInfo)
 	_, err := c.caller.Call("net_info", map[string]interface{}{}, result)

rpc/client/interface.go

@@ -115,6 +115,7 @@ type EventsClient interface {
 type MempoolClient interface {
 	UnconfirmedTxs(limit *int) (*ctypes.ResultUnconfirmedTxs, error)
 	NumUnconfirmedTxs() (*ctypes.ResultUnconfirmedTxs, error)
+	CheckTx(tx types.Tx) (*ctypes.ResultCheckTx, error)
 }
 
 // EvidenceClient is used for submitting an evidence of the malicious

rpc/client/local/local.go

@@ -104,6 +104,10 @@ func (c *Local) NumUnconfirmedTxs() (*ctypes.ResultUnconfirmedTxs, error) {
 	return core.NumUnconfirmedTxs(c.ctx)
 }
 
+func (c *Local) CheckTx(tx types.Tx) (*ctypes.ResultCheckTx, error) {
+	return core.CheckTx(c.ctx, tx)
+}
+
 func (c *Local) NetInfo() (*ctypes.ResultNetInfo, error) {
 	return core.NetInfo(c.ctx)
 }

rpc/client/mock/client.go

@@ -110,6 +110,10 @@ func (c Client) BroadcastTxSync(tx types.Tx) (*ctypes.ResultBroadcastTx, error)
 	return core.BroadcastTxSync(&rpctypes.Context{}, tx)
 }
 
+func (c Client) CheckTx(tx types.Tx) (*ctypes.ResultCheckTx, error) {
+	return core.CheckTx(&rpctypes.Context{}, tx)
+}
+
 func (c Client) NetInfo() (*ctypes.ResultNetInfo, error) {
 	return core.NetInfo(&rpctypes.Context{})
 }

rpc/client/rpc_test.go

@@ -392,6 +392,20 @@ func TestNumUnconfirmedTxs(t *testing.T) {
 	mempool.Flush()
 }
 
+func TestCheckTx(t *testing.T) {
+	mempool := node.Mempool()
+
+	for _, c := range GetClients() {
+		_, _, tx := MakeTxKV()
+
+		res, err := c.CheckTx(tx)
+		require.NoError(t, err)
+		assert.Equal(t, abci.CodeTypeOK, res.Code)
+
+		assert.Equal(t, 0, mempool.Size(), "mempool must be empty")
+	}
+}
+
 func TestTx(t *testing.T) {
 	// first we broadcast a tx
 	c := getHTTPClient()

rpc/core/env.go

@@ -67,7 +67,8 @@ type peers interface {
 // to be setup once during startup.
 type Environment struct {
 	// external, thread safe interfaces
-	ProxyAppQuery proxy.AppConnQuery
+	ProxyAppQuery   proxy.AppConnQuery
+	ProxyAppMempool proxy.AppConnMempool
 
 	// interfaces defined in types and above
 	StateDB        dbm.DB

rpc/core/mempool.go

@@ -150,3 +150,14 @@ func NumUnconfirmedTxs(ctx *rpctypes.Context) (*ctypes.ResultUnconfirmedTxs, err
 		Total:      env.Mempool.Size(),
 		TotalBytes: env.Mempool.TxsBytes()}, nil
 }
+
+// CheckTx checks the transaction without executing it. The transaction won't
+// be added to the mempool either.
+// More: https://docs.tendermint.com/master/rpc/#/Tx/check_tx
+func CheckTx(ctx *rpctypes.Context, tx types.Tx) (*ctypes.ResultCheckTx, error) {
+	res, err := env.ProxyAppMempool.CheckTxSync(abci.RequestCheckTx{Tx: tx})
+	if err != nil {
+		return nil, err
+	}
+	return &ctypes.ResultCheckTx{ResponseCheckTx: *res}, nil
+}

rpc/core/routes.go

@@ -22,6 +22,7 @@ var Routes = map[string]*rpc.RPCFunc{
 	"block_by_hash":        rpc.NewRPCFunc(BlockByHash, "hash"),
 	"block_results":        rpc.NewRPCFunc(BlockResults, "height"),
 	"commit":               rpc.NewRPCFunc(Commit, "height"),
+	"check_tx":             rpc.NewRPCFunc(CheckTx, "tx"),
 	"tx":                   rpc.NewRPCFunc(Tx, "hash,prove"),
 	"tx_search":            rpc.NewRPCFunc(TxSearch, "query,prove,page,per_page,order_by"),
 	"validators":           rpc.NewRPCFunc(Validators, "height,page,per_page"),

rpc/core/types/responses.go

@@ -174,6 +174,11 @@ type ResultBroadcastTxCommit struct {
 	Height    int64                  `json:"height"`
 }
 
+// ResultCheckTx wraps abci.ResponseCheckTx.
+type ResultCheckTx struct {
+	abci.ResponseCheckTx
+}
+
 // Result of querying for a tx
 type ResultTx struct {
 	Hash     bytes.HexBytes         `json:"hash"`

rpc/swagger/swagger.yaml

@@ -153,6 +153,39 @@ paths:
             application/json:
               schema:
                 $ref: "#/components/schemas/ErrorResponse"
+  /check_tx:
+    get:
+      summary: Checks the transaction without executing it.
+      tags:
+        - Tx
+      operationId: broadcast_tx_commit
+      description: |
+        The transaction won't be added to the mempool.
+
+        Please refer to
+        https://docs.tendermint.com/master/tendermint-core/using-tendermint.html#formatting
+        for formatting/encoding rules.
+      parameters:
+        - in: query
+          name: tx
+          required: true
+          schema:
+            type: string
+            example: "785"
+          description: The transaction
+      responses:
+        200:
+          description: ABCI application's CheckTx response
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/CheckTxResponse"
+        500:
+          description: empty error
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/ErrorResponse"
   /subscribe:
     get:
       summary: Subscribe for events via WebSocket.
@@ -2923,6 +2956,72 @@ components:
         jsonrpc:
           type: "string"
           example: "2.0"
+    CheckTxResponse:
+      type: object
+      required:
+        - "error"
+        - "result"
+        - "id"
+        - "jsonrpc"
+      properties:
+        error:
+          type: "string"
+          example: ""
+        result:
+          required:
+            - "log"
+            - "data"
+            - "code"
+          properties:
+            code:
+              type: "string"
+              example: "0"
+            data:
+              type: "string"
+              example: ""
+            log:
+              type: "string"
+              example: ""
+            info:
+              type: "string"
+              example: ""
+            gas_wanted:
+              type: "string"
+              example: "1"
+            gas_used:
+              type: "string"
+              example: "0"
+            events:
+              type: "array"
+              x-nullable: true
+              items:
+                type: "object"
+                properties:
+                  type:
+                    type: "string"
+                    example: "app"
+                  attributes:
+                    type: "array"
+                    x-nullable: false
+                    items:
+                      type: "object"
+                      properties:
+                        key:
+                          type: "string"
+                          example: "Y3JlYXRvcg=="
+                        value:
+                          type: "string"
+                          example: "Q29zbW9zaGkgTmV0b3dva28="
+            codespace:
+              type: "string"
+              example: "bank"
+          type: "object"
+        id:
+          type: "number"
+          example: 0
+        jsonrpc:
+          type: "string"
+          example: "2.0"
     BroadcastTxResponse:
       type: object
       required: