core,triedb: prevent debug_setHead from rewinding below oldest available state block

core/blockchain.go

@@ -2819,3 +2819,8 @@ func (bc *BlockChain) GetTrieFlushInterval() time.Duration {
 func (bc *BlockChain) StateSizer() *state.SizeTracker {
 	return bc.stateSizer
 }
+
+// FreezerTailBlock returns the block number of the oldest state in the freezer.
+func (bc *BlockChain) FreezerTailBlock() (uint64, error) {
+	return bc.triedb.FreezerTailBlock()
+}

eth/api_backend.go

@@ -19,6 +19,7 @@ package eth
 import (
 	"context"
 	"errors"
+	"fmt"
 	"math/big"
 	"time"
 
@@ -61,9 +62,16 @@ func (b *EthAPIBackend) CurrentBlock() *types.Header {
 	return b.eth.blockchain.CurrentBlock()
 }
 
-func (b *EthAPIBackend) SetHead(number uint64) {
+func (b *EthAPIBackend) SetHead(number uint64) error {
+	tailBlock, err := b.eth.blockchain.FreezerTailBlock()
+	if err != nil {
+		return err
+	}
+	if number < tailBlock {
+		return fmt.Errorf("cannot rewind to block %d, oldest available state is at block %d", number, tailBlock)
+	}
 	b.eth.handler.downloader.Cancel()
-	b.eth.blockchain.SetHead(number)
+	return b.eth.blockchain.SetHead(number)
 }
 
 func (b *EthAPIBackend) HeaderByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Header, error) {

internal/ethapi/api.go

@@ -1933,8 +1933,7 @@ func (api *DebugAPI) SetHead(number hexutil.Uint64) error {
 	if header.Number.Uint64() <= uint64(number) {
 		return errors.New("not allowed to rewind to a future block")
 	}
-	api.b.SetHead(uint64(number))
-	return nil
+	return api.b.SetHead(uint64(number))
 }
 
 // NetAPI offers network related RPC methods

internal/ethapi/api_test.go

@@ -487,7 +487,7 @@ func (b testBackend) RPCGasCap() uint64                        { return 10000000
 func (b testBackend) RPCEVMTimeout() time.Duration             { return time.Second }
 func (b testBackend) RPCTxFeeCap() float64                     { return 0 }
 func (b testBackend) UnprotectedAllowed() bool                 { return false }
-func (b testBackend) SetHead(number uint64)                    {}
+func (b testBackend) SetHead(number uint64) error              { return nil }
 func (b testBackend) HeaderByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Header, error) {
 	if number == rpc.LatestBlockNumber {
 		return b.chain.CurrentBlock(), nil

internal/ethapi/backend.go

@@ -55,7 +55,7 @@ type Backend interface {
 	UnprotectedAllowed() bool     // allows only for EIP155 transactions.
 
 	// Blockchain API
-	SetHead(number uint64)
+	SetHead(number uint64) error
 	HeaderByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Header, error)
 	HeaderByHash(ctx context.Context, hash common.Hash) (*types.Header, error)
 	HeaderByNumberOrHash(ctx context.Context, blockNrOrHash rpc.BlockNumberOrHash) (*types.Header, error)

internal/ethapi/transaction_args_test.go

@@ -336,7 +336,7 @@ func (b *backendMock) RPCGasCap() uint64                 { return 0 }
 func (b *backendMock) RPCEVMTimeout() time.Duration      { return time.Second }
 func (b *backendMock) RPCTxFeeCap() float64              { return 0 }
 func (b *backendMock) UnprotectedAllowed() bool          { return false }
-func (b *backendMock) SetHead(number uint64)             {}
+func (b *backendMock) SetHead(number uint64) error       { return nil }
 func (b *backendMock) HeaderByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Header, error) {
 	return nil, nil
 }

triedb/database.go

@@ -384,3 +384,12 @@ func (db *Database) SnapshotCompleted() bool {
 	}
 	return pdb.SnapshotCompleted()
 }
+
+// FrezzerTailBlock returns the block number of the oldest state in the freezer.
+func (db *Database) FreezerTailBlock() (uint64, error) {
+	pdb, ok := db.backend.(*pathdb.Database)
+	if !ok {
+		return 0, nil
+	}
+	return pdb.FreezerTailBlock()
+}

triedb/pathdb/database.go

@@ -692,3 +692,28 @@ func (db *Database) SnapshotCompleted() bool {
 	}
 	return db.tree.bottom().genComplete()
 }
+
+// FreezerTailBlock returns the block number of the oldest state in the freezer.
+func (db *Database) FreezerTailBlock() (uint64, error) {
+	freezer := db.stateFreezer
+	if freezer == nil {
+		return 0, errors.New("freezer is not available")
+	}
+
+	tailID, err := freezer.Tail()
+	if err != nil {
+		return 0, err
+	}
+
+	// No state has been persistent, return the genesis block number.
+	if tailID == 0 {
+		return 0, nil
+	}
+
+	blob := rawdb.ReadStateHistoryMeta(freezer, tailID+1)
+	var m meta
+	if err := m.decode(blob); err != nil {
+		return 0, err
+	}
+	return m.block, nil
+}