consensus/clique, core: chain maker clique + error tests

consensus/clique/clique.go

@@ -93,27 +93,33 @@ var (
 
 	// errMissingSignature is returned if a block's extra-data section doesn't seem
 	// to contain a 65 byte secp256k1 signature.
-	errMissingSignature = errors.New("extra-data 65 byte suffix signature missing")
+	errMissingSignature = errors.New("extra-data 65 byte signature suffix missing")
 
 	// errExtraSigners is returned if non-checkpoint block contain signer data in
 	// their extra-data fields.
 	errExtraSigners = errors.New("non-checkpoint block contains extra signer list")
 
 	// errInvalidCheckpointSigners is returned if a checkpoint block contains an
-	// invalid list of signers (i.e. non divisible by 20 bytes, or not the correct
-	// ones).
+	// invalid list of signers (i.e. non divisible by 20 bytes).
 	errInvalidCheckpointSigners = errors.New("invalid signer list on checkpoint block")
 
+	// errMismatchingCheckpointSigners is returned if a checkpoint block contains a
+	// list of signers different than the one the local node calculated.
+	errMismatchingCheckpointSigners = errors.New("mismatching signer list on checkpoint block")
+
 	// errInvalidMixDigest is returned if a block's mix digest is non-zero.
 	errInvalidMixDigest = errors.New("non-zero mix digest")
 
 	// errInvalidUncleHash is returned if a block contains an non-empty uncle list.
 	errInvalidUncleHash = errors.New("non empty uncle hash")
 
-	// errInvalidDifficulty is returned if the difficulty of a block is not either
-	// of 1 or 2, or if the value does not match the turn of the signer.
+	// errInvalidDifficulty is returned if the difficulty of a block neither 1 or 2.
 	errInvalidDifficulty = errors.New("invalid difficulty")
 
+	// errWrongDifficulty is returned if the difficulty of a block doesn't match the
+	// turn of the signer.
+	errWrongDifficulty = errors.New("wrong difficulty")
+
 	// ErrInvalidTimestamp is returned if the timestamp of a block is lower than
 	// the previous block's timestamp + the minimum block period.
 	ErrInvalidTimestamp = errors.New("invalid timestamp")
@@ -122,8 +128,12 @@ var (
 	// be modified via out-of-range or non-contiguous headers.
 	errInvalidVotingChain = errors.New("invalid voting chain")
 
-	// errUnauthorized is returned if a header is signed by a non-authorized entity.
-	errUnauthorized = errors.New("unauthorized")
+	// errUnauthorizedSigner is returned if a header is signed by a non-authorized entity.
+	errUnauthorizedSigner = errors.New("unauthorized signer")
+
+	// errRecentlySigned is returned if a header is signed by an authorized entity
+	// that already signed a header recently, thus is temporarily not allowed to.
+	errRecentlySigned = errors.New("recently signed")
 
 	// errWaitTransactions is returned if an empty block is attempted to be sealed
 	// on an instant chain (0 second period). It's important to refuse these as the
@@ -205,6 +215,9 @@ type Clique struct {
 	signer common.Address // Ethereum address of the signing key
 	signFn SignerFn       // Signer function to authorize hashes with
 	lock   sync.RWMutex   // Protects the signer fields
+
+	// The fields below are for testing only
+	fakeDiff bool // Skip difficulty verifications
 }
 
 // New creates a Clique proof-of-authority consensus engine with the initial
@@ -359,7 +372,7 @@ func (c *Clique) verifyCascadingFields(chain consensus.ChainReader, header *type
 		}
 		extraSuffix := len(header.Extra) - extraSeal
 		if !bytes.Equal(header.Extra[extraVanity:extraSuffix], signers) {
-			return errInvalidCheckpointSigners
+			return errMismatchingCheckpointSigners
 		}
 	}
 	// All basic checks passed, verify the seal and return
@@ -481,23 +494,25 @@ func (c *Clique) verifySeal(chain consensus.ChainReader, header *types.Header, p
 		return err
 	}
 	if _, ok := snap.Signers[signer]; !ok {
-		return errUnauthorized
+		return errUnauthorizedSigner
 	}
 	for seen, recent := range snap.Recents {
 		if recent == signer {
 			// Signer is among recents, only fail if the current block doesn't shift it out
 			if limit := uint64(len(snap.Signers)/2 + 1); seen > number-limit {
-				return errUnauthorized
+				return errRecentlySigned
 			}
 		}
 	}
 	// Ensure that the difficulty corresponds to the turn-ness of the signer
-	inturn := snap.inturn(header.Number.Uint64(), signer)
-	if inturn && header.Difficulty.Cmp(diffInTurn) != 0 {
-		return errInvalidDifficulty
-	}
-	if !inturn && header.Difficulty.Cmp(diffNoTurn) != 0 {
-		return errInvalidDifficulty
+	if !c.fakeDiff {
+		inturn := snap.inturn(header.Number.Uint64(), signer)
+		if inturn && header.Difficulty.Cmp(diffInTurn) != 0 {
+			return errWrongDifficulty
+		}
+		if !inturn && header.Difficulty.Cmp(diffNoTurn) != 0 {
+			return errWrongDifficulty
+		}
 	}
 	return nil
 }
@@ -613,7 +628,7 @@ func (c *Clique) Seal(chain consensus.ChainReader, block *types.Block, results c
 		return err
 	}
 	if _, authorized := snap.Signers[signer]; !authorized {
-		return errUnauthorized
+		return errUnauthorizedSigner
 	}
 	// If we're amongst the recent signers, wait for the next block
 	for seen, recent := range snap.Recents {