cmd, core, eth, els, params: disallow setheads below genesis, tweaks

core/genesis.go

@@ -269,8 +269,7 @@ func (e *GenesisMismatchError) Error() string {
 
 // ChainOverrides contains the changes to chain config.
 type ChainOverrides struct {
-	OverrideTerminalTotalDifficulty       *big.Int
-	OverrideTerminalTotalDifficultyPassed *bool
+	OverrideShanghai *big.Int
 }
 
 // SetupGenesisBlock writes or updates the genesis block in db.
@@ -296,15 +295,11 @@ func SetupGenesisBlockWithOverride(db ethdb.Database, triedb *trie.Database, gen
 	}
 	applyOverrides := func(config *params.ChainConfig) {
 		if config != nil {
-			if overrides != nil && overrides.OverrideTerminalTotalDifficulty != nil {
-				config.TerminalTotalDifficulty = overrides.OverrideTerminalTotalDifficulty
-			}
-			if overrides != nil && overrides.OverrideTerminalTotalDifficultyPassed != nil {
-				config.TerminalTotalDifficultyPassed = *overrides.OverrideTerminalTotalDifficultyPassed
+			if overrides != nil && overrides.OverrideShanghai != nil {
+				config.ShanghaiTime = overrides.OverrideShanghai
 			}
 		}
 	}
-
 	// Just commit the new block if there is no stored genesis block.
 	stored := rawdb.ReadCanonicalHash(db, 0)
 	if (stored == common.Hash{}) {

core/headerchain.go

@@ -578,6 +578,19 @@ func (hc *HeaderChain) SetHeadWithTimestamp(time uint64, updateFn UpdateHeadBloc
 // setHead rewinds the local chain to a new head block or a head timestamp.
 // Everything above the new head will be deleted and the new one set.
 func (hc *HeaderChain) setHead(headBlock uint64, headTime uint64, updateFn UpdateHeadBlocksCallback, delFn DeleteBlockContentCallback) {
+	// Sanity check that there's no attempt to undo the genesis block. This is
+	// a fairly synthetic case where someone enables a timestamp based fork
+	// below the genesis timestamp. It's nice to not allow that instead of the
+	// entire chain getting deleted.
+	if headTime > 0 && hc.genesisHeader.Time > headTime {
+		// Note, a critical error is quite brutal, but we should really not reach
+		// this point. Since pre-timestamp based forks it was impossible to have
+		// a fork before block 0, the setHead would always work. With timestamp
+		// forks it becomes possible to specify below the genesis. That said, the
+		// only time we setHead via timestamp is with chain config changes on the
+		// startup, so failing hard there is ok.
+		log.Crit("Rejecting genesis rewind via timestamp", "target", headTime, "genesis", hc.genesisHeader.Time)
+	}
 	var (
 		parentHash common.Hash
 		batch      = hc.chainDb.NewBatch()