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

4 files changed, 44 insertions, 1 deletions

diff --git a/common/types.go b/common/types.go
index bd15c5b..1bda164 100644
--- a/common/types.go
+++ b/common/types.go
@@ -1,6 +1,23 @@
 // Copyright 2018 The dexon-consensus-core Authors
 // This file is part of the dexon-consensus-core library.
 //
+// The dexon-consensus-core library is free software: you can redistribute it
+// and/or modify it under the terms of the GNU Lesser General Public License as
+// published by the Free Software Foundation, either version 3 of the License,
+// or (at your option) any later version.
+//
+// The dexon-consensus-core library is distributed in the hope that it will be
+// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
+// General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the dexon-consensus-core library. If not, see
+// <http://www.gnu.org/licenses/>.
+
+// Copyright 2018 The dexon-consensus-core Authors
+// This file is part of the dexon-consensus-core library.
+//
 // The dexon-consensus-core library is free software: you can redistribute it and/or
 // modify it under the terms of the GNU Lesser General Public License as
 // published by the Free Software Foundation, either version 3 of the License,
@@ -41,6 +58,11 @@ func (h Hash) Equal(hp Hash) bool {
 	return h == hp
 }
 
+// Less compares if current hash is lesser.
+func (h Hash) Less(hp Hash) bool {
+	return bytes.Compare(h[:], hp[:]) < 0
+}
+
 // MarshalText implements the encoding.TextMarhsaler interface.
 func (h Hash) MarshalText() ([]byte, error) {
 	result := make([]byte, hex.EncodedLen(HashLength))
@@ -58,7 +80,7 @@ func (h *Hash) UnmarshalText(text []byte) error {
 type Hashes []Hash
 
 func (hs Hashes) Len() int           { return len(hs) }
-func (hs Hashes) Less(i, j int) bool { return bytes.Compare(hs[i][:], hs[j][:]) < 0 }
+func (hs Hashes) Less(i, j int) bool { return hs[i].Less(hs[j]) }
 func (hs Hashes) Swap(i, j int)      { hs[i], hs[j] = hs[j], hs[i] }
 
 // SortedHashes is a slice of hashes sorted in ascending order.
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)