fix(rpc): guard TxsResults length before indexing by block tx position

CHANGELOG.md

@@ -12,6 +12,7 @@
 
 ### Bug fixes
 
+* [#2175](https://github.com/crypto-org-chain/cronos/pull/2175) fix(rpc): guard `TxsResults` length before indexing by block tx position.
 * [#2176](https://github.com/crypto-org-chain/cronos/pull/2176) fix(app): retry block list decryption instead of caching the blob before it is applied.
 * [#2155](https://github.com/crypto-org-chain/cronos/pull/2155) fix(mempool): size tx-cache-size and max-tx-bytes from mempool config directly.
 * [#2169](https://github.com/crypto-org-chain/cronos/pull/2169) fix(cronos): add safe multiply int check during voucher conversion to EVM coins.

x/cronos/rpc/api.go

@@ -86,6 +86,16 @@ func NewCronosAPI(
 	}
 }
 
+func checkTxsResultsLength(block *coretypes.ResultBlock, blockResults *coretypes.ResultBlockResults) error {
+	if len(blockResults.TxsResults) != len(block.Block.Txs) {
+		return fmt.Errorf(
+			"mismatched tx results length at height %d: block has %d txs, but got %d tx results",
+			block.Block.Height, len(block.Block.Txs), len(blockResults.TxsResults),
+		)
+	}
+	return nil
+}
+
 func (api *CronosAPI) getBlockDetail(blockNrOrHash rpctypes.BlockNumberOrHash) (
 	resBlock *coretypes.ResultBlock,
 	blockNumber int64,
@@ -94,22 +104,24 @@ func (api *CronosAPI) getBlockDetail(blockNrOrHash rpctypes.BlockNumberOrHash) (
 	baseFee *big.Int,
 	err error,
 ) {
-	var blockNum rpctypes.BlockNumber
 	resBlock, err = api.getBlock(blockNrOrHash)
 	if err != nil {
 		api.logger.Debug("block not found", "height", blockNrOrHash, "error", err.Error())
-		return resBlock, blockNumber, blockHash, blockRes, baseFee, err
+		return nil, 0, "", nil, nil, err
 	}
 	blockNumber = resBlock.Block.Height
 	blockHash = common.BytesToHash(resBlock.Block.Header.Hash()).Hex()
 	blockRes, err = api.backend.TendermintBlockResultByNumber(&blockNumber)
 	if err != nil {
-		api.logger.Debug("failed to retrieve block results", "height", blockNum, "error", err.Error())
-		return resBlock, blockNumber, blockHash, blockRes, baseFee, err
+		api.logger.Debug("failed to retrieve block results", "height", blockNumber, "error", err.Error())
+		return nil, 0, "", nil, nil, err
+	}
+	if err = checkTxsResultsLength(resBlock, blockRes); err != nil {
+		return nil, 0, "", nil, nil, err
 	}
 	baseFee, err = api.backend.BaseFee(blockRes)
 	if err != nil {
-		return resBlock, blockNumber, blockHash, blockRes, baseFee, err
+		return nil, 0, "", nil, nil, err
 	}
 	return resBlock, blockNumber, blockHash, blockRes, baseFee, err
 }

x/cronos/rpc/api_test.go

@@ -0,0 +1,81 @@
+package rpc
+
+import (
+	"testing"
+
+	abci "github.com/cometbft/cometbft/abci/types"
+	coretypes "github.com/cometbft/cometbft/rpc/core/types"
+	cmttypes "github.com/cometbft/cometbft/types"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+)
+
+func newResBlock(t *testing.T, numTxs int) *coretypes.ResultBlock {
+	t.Helper()
+	txs := make(cmttypes.Txs, numTxs)
+	for i := range txs {
+		txs[i] = cmttypes.Tx{byte(i)}
+	}
+	return &coretypes.ResultBlock{
+		Block: &cmttypes.Block{
+			Header: cmttypes.Header{Height: 100},
+			Data:   cmttypes.Data{Txs: txs},
+		},
+	}
+}
+
+func newBlockRes(t *testing.T, numResults int) *coretypes.ResultBlockResults {
+	t.Helper()
+	results := make([]*abci.ExecTxResult, numResults)
+	for i := range results {
+		results[i] = &abci.ExecTxResult{}
+	}
+	return &coretypes.ResultBlockResults{TxsResults: results}
+}
+
+type CheckTxsResultsLengthTestSuite struct {
+	suite.Suite
+}
+
+func TestCheckTxsResultsLengthTestSuite(t *testing.T) {
+	suite.Run(t, new(CheckTxsResultsLengthTestSuite))
+}
+
+func (s *CheckTxsResultsLengthTestSuite) TestCheckTxsResultsLength() {
+	testCases := []struct {
+		name    string
+		numTxs  int
+		numRes  int
+		wantErr string
+	}{
+		{
+			name:   "matching lengths returns no error",
+			numTxs: 3,
+			numRes: 3,
+		},
+		{
+			name:    "fewer tx results than txs returns error instead of panicking",
+			numTxs:  3,
+			numRes:  2,
+			wantErr: "mismatched tx results length at height 100: block has 3 txs, but got 2 tx results",
+		},
+		{
+			name:    "more tx results than txs returns error",
+			numTxs:  2,
+			numRes:  3,
+			wantErr: "mismatched tx results length at height 100: block has 2 txs, but got 3 tx results",
+		},
+	}
+
+	for _, tc := range testCases {
+		s.Run(tc.name, func() {
+			t := s.T()
+			err := checkTxsResultsLength(newResBlock(t, tc.numTxs), newBlockRes(t, tc.numRes))
+			if tc.wantErr == "" {
+				require.NoError(t, err)
+				return
+			}
+			require.EqualError(t, err, tc.wantErr)
+		})
+	}
+}