Fvm: impl VerifyConsensusFault

chain/vm/fvm.go

@@ -1,10 +1,16 @@
 package vm
 
 import (
+	"bytes"
 	"context"
 
+	"github.com/filecoin-project/lotus/chain/state"
+	cbor "github.com/ipfs/go-ipld-cbor"
+
+	"github.com/filecoin-project/go-address"
 	"github.com/filecoin-project/go-state-types/abi"
 	"github.com/filecoin-project/go-state-types/exitcode"
+	"github.com/filecoin-project/lotus/lib/sigs"
 
 	"golang.org/x/xerrors"
 
@@ -13,20 +19,209 @@ import (
 	ffi "github.com/filecoin-project/filecoin-ffi"
 	ffi_cgo "github.com/filecoin-project/filecoin-ffi/cgo"
 
+	"github.com/filecoin-project/lotus/chain/actors/adt"
+	"github.com/filecoin-project/lotus/chain/actors/builtin/miner"
 	"github.com/filecoin-project/lotus/chain/types"
 	"github.com/ipfs/go-cid"
 )
 
 var _ VMI = (*FVM)(nil)
+var _ ffi_cgo.Externs = (*FvmExtern)(nil)
 
 type FvmExtern struct {
 	Rand
 	blockstore.Blockstore
+	epoch   abi.ChainEpoch
+	lbState LookbackStateGetter
+	base    cid.Cid
+}
+
+// Similar to the one in syscalls.go used by the Lotus VM, except it never errors
+// Errors are logged and "no fault" is returned, which is functionally what go-actors does anyway
+func (x *FvmExtern) VerifyConsensusFault(ctx context.Context, a, b, extra []byte) *ffi_cgo.ConsensusFaultWithGas {
+	ret := &ffi_cgo.ConsensusFaultWithGas{
+		// TODO: is this gonna be a problem on the receiving end? should we return address.NewIDAddress(0) instead?
+		Target: address.Undef,
+		Type:   ffi_cgo.ConsensusFaultNone,
+	}
+
+	// Note that block syntax is not validated. Any validly signed block will be accepted pursuant to the below conditions.
+	// Whether or not it could ever have been accepted in a chain is not checked/does not matter here.
+	// for that reason when checking block parent relationships, rather than instantiating a Tipset to do so
+	// (which runs a syntactic check), we do it directly on the CIDs.
+
+	// (0) cheap preliminary checks
+
+	// can blocks be decoded properly?
+	var blockA, blockB types.BlockHeader
+	if decodeErr := blockA.UnmarshalCBOR(bytes.NewReader(a)); decodeErr != nil {
+		log.Info("invalid consensus fault: cannot decode first block header: %w", decodeErr)
+		return ret
+	}
+
+	if decodeErr := blockB.UnmarshalCBOR(bytes.NewReader(b)); decodeErr != nil {
+		log.Info("invalid consensus fault: cannot decode second block header: %w", decodeErr)
+		return ret
+	}
+
+	// Commented out from the Lotus VM code: FvmExtern only supports v14 and onwards
+	// workaround chain halt
+	//if build.IsNearUpgrade(blockA.Height, build.UpgradeOrangeHeight) {
+	//	return nil, xerrors.Errorf("consensus reporting disabled around Upgrade Orange")
+	//}
+	//if build.IsNearUpgrade(blockB.Height, build.UpgradeOrangeHeight) {
+	//	return nil, xerrors.Errorf("consensus reporting disabled around Upgrade Orange")
+	//}
+
+	// are blocks the same?
+	if blockA.Cid().Equals(blockB.Cid()) {
+		log.Info("invalid consensus fault: submitted blocks are the same")
+		return ret
+	}
+	// (1) check conditions necessary to any consensus fault
+
+	// were blocks mined by same miner?
+	if blockA.Miner != blockB.Miner {
+		log.Info("invalid consensus fault: blocks not mined by the same miner")
+		return ret
+	}
+
+	ret.Target = blockA.Miner
+
+	// block a must be earlier or equal to block b, epoch wise (ie at least as early in the chain).
+	if blockB.Height < blockA.Height {
+		log.Info("invalid consensus fault: first block must not be of higher height than second")
+		return ret
+	}
+
+	ret.Epoch = blockB.Height
+
+	faultType := ffi_cgo.ConsensusFaultNone
+
+	// (2) check for the consensus faults themselves
+	// (a) double-fork mining fault
+	if blockA.Height == blockB.Height {
+		faultType = ffi_cgo.ConsensusFaultDoubleForkMining
+	}
+
+	// (b) time-offset mining fault
+	// strictly speaking no need to compare heights based on double fork mining check above,
+	// but at same height this would be a different fault.
+	if types.CidArrsEqual(blockA.Parents, blockB.Parents) && blockA.Height != blockB.Height {
+		faultType = ffi_cgo.ConsensusFaultTimeOffsetMining
+	}
+
+	// (c) parent-grinding fault
+	// Here extra is the "witness", a third block that shows the connection between A and B as
+	// A's sibling and B's parent.
+	// Specifically, since A is of lower height, it must be that B was mined omitting A from its tipset
+	//
+	//      B
+	//      |
+	//  [A, C]
+	var blockC types.BlockHeader
+	if len(extra) > 0 {
+		if decodeErr := blockC.UnmarshalCBOR(bytes.NewReader(extra)); decodeErr != nil {
+			log.Info("invalid consensus fault: cannot decode extra: %w", decodeErr)
+			// just to match Lotus VM consensus, zero out any already-set faults
+			faultType = ffi_cgo.ConsensusFaultNone
+			return ret
+		}
+
+		if types.CidArrsEqual(blockA.Parents, blockC.Parents) && blockA.Height == blockC.Height &&
+			types.CidArrsContains(blockB.Parents, blockC.Cid()) && !types.CidArrsContains(blockB.Parents, blockA.Cid()) {
+			faultType = ffi_cgo.ConsensusFaultParentGrinding
+		}
+	}
+
+	// (3) return if no consensus fault by now
+	if faultType == ffi_cgo.ConsensusFaultNone {
+		log.Info("invalid consensus fault: no fault detected")
+		return ret
+	}
+
+	// else
+	// (4) expensive final checks
+
+	// check blocks are properly signed by their respective miner
+	// note we do not need to check extra's: it is a parent to block b
+	// which itself is signed, so it was willingly included by the miner
+	gasUsed, sigErr := x.VerifyBlockSig(ctx, &blockA)
+	ret.GasUsed += gasUsed
+	if sigErr != nil {
+		log.Info("invalid consensus fault: cannot verify first block sig: %w", sigErr)
+		return ret
+	}
+
+	gasUsed, sigErr = x.VerifyBlockSig(ctx, &blockB)
+	ret.GasUsed += gasUsed
+	if sigErr != nil {
+		log.Info("invalid consensus fault: cannot verify second block sig: %w", sigErr)
+		return ret
+	}
+
+	ret.Type = faultType
+
+	return ret
+}
+
+func (x *FvmExtern) VerifyBlockSig(ctx context.Context, blk *types.BlockHeader) (int64, error) {
+	waddr, gasUsed, err := x.workerKeyAtLookback(ctx, blk.Miner, blk.Height)
+	if err != nil {
+		return gasUsed, err
+	}
+
+	return gasUsed, sigs.CheckBlockSignature(ctx, blk, waddr)
 }
 
-func (x *FvmExtern) VerifyConsensusFault(ctx context.Context, h1, h2, extra []byte) (*ffi_cgo.ConsensusFault, error) {
-	// TODO
-	panic("unimplemented")
+func (x *FvmExtern) workerKeyAtLookback(ctx context.Context, minerId address.Address, height abi.ChainEpoch) (address.Address, int64, error) {
+	// Commented out from the Lotus VM code: FvmExtern only supports v14 and onwards
+	//if x.networkVersion >= network.Version7 && height < x.epoch-policy.ChainFinality {
+	//	return address.Undef, xerrors.Errorf("cannot get worker key (currEpoch %d, height %d)", ss.epoch, height)
+	//}
+
+	gasUsed := int64(0)
+	gasAdder := func(gc GasCharge) {
+		// technically not overflow safe, but that's fine
+		gasUsed += gc.Total()
+	}
+
+	cstWithoutGas := cbor.NewCborStore(x.Blockstore)
+	cbb := &gasChargingBlocks{gasAdder, PricelistByEpoch(x.epoch), x.Blockstore}
+	cstWithGas := cbor.NewCborStore(cbb)
+
+	lbState, err := x.lbState(ctx, height)
+	if err != nil {
+		return address.Undef, gasUsed, err
+	}
+	// get appropriate miner actor
+	act, err := lbState.GetActor(minerId)
+	if err != nil {
+		return address.Undef, gasUsed, err
+	}
+
+	// use that to get the miner state
+	mas, err := miner.Load(adt.WrapStore(ctx, cstWithGas), act)
+	if err != nil {
+		return address.Undef, gasUsed, err
+	}
+
+	info, err := mas.Info()
+	if err != nil {
+		return address.Undef, gasUsed, err
+	}
+
+	stateTree, err := state.LoadStateTree(cstWithoutGas, x.base)
+	if err != nil {
+		return address.Undef, gasUsed, err
+	}
+
+	raddr, err := ResolveToKeyAddr(stateTree, cstWithGas, info.Worker)
+	if err != nil {
+		return address.Undef, gasUsed, err
+	}
+
+	return raddr, gasUsed, nil
 }
 
 type FVM struct {
@@ -35,7 +230,7 @@ type FVM struct {
 
 func NewFVM(ctx context.Context, opts *VMOpts) (*FVM, error) {
 	fvm, err := ffi.CreateFVM(0,
-		&FvmExtern{Rand: opts.Rand, Blockstore: opts.Bstore},
+		&FvmExtern{Rand: opts.Rand, Blockstore: opts.Bstore, lbState: opts.LookbackState, base: opts.StateBase, epoch: opts.Epoch},
 		opts.Epoch, opts.BaseFee, opts.FilVested, opts.NetworkVersion, opts.StateBase,
 	)
 	if err != nil {