Add verify block signature function and unit test (#6166)

Part of https://github.com/ledgerwatch/erigon/issues/5965

See
https://github.com/ethereum/consensus-specs/blob/dev/specs/phase0/beacon-chain.md#beacon-chain-state-transition-function.

cmd/erigon-cl/core/transition/process_slots.go

@@ -3,6 +3,7 @@ package transition
 import (
 	"fmt"
 
+	"github.com/Giulio2002/bls"
 	"github.com/ledgerwatch/erigon/cl/cltypes"
 )
 
@@ -39,3 +40,12 @@ func (s *StateTransistor) processSlots(state *cltypes.BeaconState, slot uint64)
 	}
 	return nil
 }
+
+func (s *StateTransistor) verifyBlockSignature(state *cltypes.BeaconState, block *cltypes.SignedBeaconBlockBellatrix) (bool, error) {
+	proposer := state.Validators[block.Block.ProposerIndex]
+	signing_root, err := block.Block.Body.HashTreeRoot()
+	if err != nil {
+		return false, err
+	}
+	return bls.Verify(block.Signature[:], signing_root[:], proposer.PublicKey[:])
+}

cmd/erigon-cl/core/transition/process_slots_test.go

@@ -24,8 +24,34 @@ var (
 	blockHash43 = "3ff92b54cba8067044f6b6ca0a69c7a6344154de2a38742e7a89b1057877fffa"
 	stateHash44 = "81954d95a6452e516c076f3254424cac99ae3e8c757f33d8aacb97fd8ef02864"
 	blockHash44 = "3ff92b54cba8067044f6b6ca0a69c7a6344154de2a38742e7a89b1057877fffa"
+
+	testPubKey    = [48]byte{152, 250, 212, 202, 139, 152, 8, 45, 224, 234, 128, 186, 142, 67, 172, 78, 124, 69, 173, 39, 48, 98, 75, 146, 244, 131, 55, 15, 138, 170, 246, 81, 77, 88, 244, 114, 1, 47, 123, 123, 55, 174, 58, 139, 90, 249, 237, 19}
+	testSignature = [96]byte{141, 154, 97, 227, 33, 202, 245, 163, 252, 75, 124, 240, 197, 188, 117, 88, 146, 35, 171, 19, 247, 222, 208, 78, 160, 135, 37, 246, 251, 1, 170, 160, 121, 83, 11, 146, 207, 100, 82, 101, 243, 131, 17, 142, 201, 231, 170, 116, 5, 62, 23, 250, 166, 178, 120, 64, 214, 70, 122, 203, 30, 156, 153, 12, 69, 247, 193, 208, 73, 4, 245, 70, 97, 67, 42, 217, 30, 98, 191, 21, 190, 47, 168, 218, 36, 52, 59, 238, 88, 14, 100, 105, 16, 231, 157, 172}
+	badSignature  = [96]byte{182, 82, 244, 116, 233, 59, 56, 251, 52, 194, 122, 255, 161, 96, 204, 165, 43, 97, 19, 48, 130, 187, 17, 200, 223, 62, 114, 194, 225, 19, 242, 174, 224, 24, 188, 83, 118, 45, 23, 192, 205, 200, 47, 165, 212, 35, 193, 189, 10, 165, 161, 72, 81, 250, 195, 186, 174, 197, 26, 208, 165, 254, 31, 214, 135, 140, 129, 47, 211, 59, 87, 136, 55, 242, 93, 149, 128, 30, 84, 126, 182, 157, 70, 90, 68, 113, 7, 92, 70, 230, 164, 54, 120, 16, 180, 151}
+	testValidator = &cltypes.Validator{
+		PublicKey: testPubKey,
+	}
 )
 
+func getTestBeaconBlock() *cltypes.SignedBeaconBlockBellatrix {
+	return &cltypes.SignedBeaconBlockBellatrix{
+		Block: &cltypes.BeaconBlockBellatrix{
+			ProposerIndex: 0,
+			Body: &cltypes.BeaconBodyBellatrix{
+				Graffiti: make([]byte, 32),
+				SyncAggregate: &cltypes.SyncAggregate{
+					SyncCommiteeBits: make([]byte, 64),
+				},
+				ExecutionPayload: &cltypes.ExecutionPayload{
+					LogsBloom:     make([]byte, 256),
+					BaseFeePerGas: make([]byte, 32),
+				},
+			},
+		},
+		Signature: testSignature,
+	}
+}
+
 func getTestBeaconState() *cltypes.BeaconState {
 	return &cltypes.BeaconState{
 		BlockRoots:        make([][32]byte, 8192),
@@ -54,6 +80,12 @@ func getTestBeaconState() *cltypes.BeaconState {
 	}
 }
 
+func getTestBeaconStateWithValidator() *cltypes.BeaconState {
+	res := getTestBeaconState()
+	res.Validators = append(res.Validators, testValidator)
+	return res
+}
+
 func prepareNextBeaconState(t *testing.T, slots []uint64, stateHashs, blockHashs []string) *cltypes.BeaconState {
 	nextState := getTestBeaconState()
 	// Set slot to initial index.
@@ -217,3 +249,62 @@ func TestProcessSlots(t *testing.T) {
 		})
 	}
 }
+
+func TestVerifyBlockSignature(t *testing.T) {
+	badSigBlock := getTestBeaconBlock()
+	badSigBlock.Signature = badSignature
+	testCases := []struct {
+		description string
+		state       *cltypes.BeaconState
+		block       *cltypes.SignedBeaconBlockBellatrix
+		wantValid   bool
+		wantErr     bool
+	}{
+		{
+			description: "success",
+			state:       getTestBeaconStateWithValidator(),
+			block:       getTestBeaconBlock(),
+			wantErr:     false,
+			wantValid:   true,
+		},
+		{
+			description: "failure_empty_block",
+			state:       getTestBeaconStateWithValidator(),
+			block: &cltypes.SignedBeaconBlockBellatrix{
+				Block: &cltypes.BeaconBlockBellatrix{
+					Body: &cltypes.BeaconBodyBellatrix{},
+				},
+			},
+			wantErr: true,
+		},
+		{
+			description: "failure_bad_signature",
+			state:       getTestBeaconStateWithValidator(),
+			block:       badSigBlock,
+			wantErr:     false,
+			wantValid:   false,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			s := New(tc.state, testBeaconConfig, nil)
+			valid, err := s.verifyBlockSignature(tc.state, tc.block)
+			if tc.wantErr {
+				if err == nil {
+					t.Errorf("unexpected success, wanted error")
+				}
+				return
+			}
+			// Non-failure case.
+			if err != nil {
+				t.Errorf("unexpected error: %v", err)
+			}
+
+			// Confirm that validity matches what we expect.
+			if valid != tc.wantValid {
+				t.Errorf("unexpected difference in validity: want %v, got %v", tc.wantValid, valid)
+			}
+		})
+	}
+}