core: Check sorted ack in sanity check (#173)

3 files changed, 21 insertions, 0 deletions

diff --git a/core/lattice-data.go b/core/lattice-data.go
index e5d173d..7eec7f2 100644
--- a/core/lattice-data.go
+++ b/core/lattice-data.go
@@ -40,6 +40,7 @@ var (
 	ErrForkBlock               = fmt.Errorf("fork block")
 	ErrNotAckParent            = fmt.Errorf("not ack parent")
 	ErrDoubleAck               = fmt.Errorf("double ack")
+	ErrAcksNotSorted           = fmt.Errorf("acks not sorted")
 	ErrInvalidBlockHeight      = fmt.Errorf("invalid block height")
 	ErrAlreadyInLattice        = fmt.Errorf("block already in lattice")
 	ErrIncorrectBlockTime      = fmt.Errorf("block timestampe is incorrect")
diff --git a/core/lattice.go b/core/lattice.go
index 530fbab..27d38d8 100644
--- a/core/lattice.go
+++ b/core/lattice.go
@@ -102,6 +102,15 @@ func (s *Lattice) SanityCheck(b *types.Block) (err error) {
 		err = ErrIncorrectHash
 		return
 	}
+	for i := range b.Acks {
+		if i == 0 {
+			continue
+		}
+		if !b.Acks[i-1].Less(b.Acks[i]) {
+			err = ErrAcksNotSorted
+			return
+		}
+	}
 	// Check the signer.
 	pubKey, err := crypto.SigToPub(b.Hash, b.Signature)
 	if err != nil {
diff --git a/core/lattice_test.go b/core/lattice_test.go
index 2115d1a..bf65684 100644
--- a/core/lattice_test.go
+++ b/core/lattice_test.go
@@ -220,6 +220,17 @@ func (s *LatticeTestSuite) TestSanityCheck() {
 	b.Signature, err = auth.prvKey.Sign(common.NewRandomHash())
 	req.NoError(err)
 	req.Equal(lattice.SanityCheck(b), ErrIncorrectSignature)
+	// A block with un-sorted acks should not pass sanity check.
+	b.Acks = common.NewSortedHashes(common.Hashes{
+		common.NewRandomHash(),
+		common.NewRandomHash(),
+		common.NewRandomHash(),
+		common.NewRandomHash(),
+		common.NewRandomHash(),
+	})
+	b.Acks[0], b.Acks[1] = b.Acks[1], b.Acks[0]
+	req.NoError(auth.SignBlock(b))
+	req.Equal(lattice.SanityCheck(b), ErrAcksNotSorted)
 	// A block with incorrect hash should not pass sanity check.
 	b.Hash = common.NewRandomHash()
 	req.Equal(lattice.SanityCheck(b), ErrIncorrectHash)