From 3f344aee55350cc51904673a1f18f658269b89f8 Mon Sep 17 00:00:00 2001
From: Preston Van Loon <preston@prysmaticlabs.com>
Date: Mon, 16 Dec 2019 00:52:20 -0600
Subject: [PATCH] add a few fuzz tests (#4291)

---
 beacon-chain/core/blocks/BUILD.bazel          |  2 +
 beacon-chain/core/blocks/block_operations.go  |  4 ++
 .../core/blocks/block_operations_fuzz_test.go | 37 +++++++++++++++++++
 beacon-chain/core/helpers/attestation.go      |  6 ---
 4 files changed, 43 insertions(+), 6 deletions(-)
 create mode 100644 beacon-chain/core/blocks/block_operations_fuzz_test.go

diff --git a/beacon-chain/core/blocks/BUILD.bazel b/beacon-chain/core/blocks/BUILD.bazel
index 45166b769..af4e970cb 100644
--- a/beacon-chain/core/blocks/BUILD.bazel
+++ b/beacon-chain/core/blocks/BUILD.bazel
@@ -37,6 +37,7 @@ go_test(
     name = "go_default_test",
     size = "medium",
     srcs = [
+        "block_operations_fuzz_test.go",
         "block_operations_test.go",
         "block_test.go",
         "eth1_data_test.go",
@@ -51,6 +52,7 @@ go_test(
         "//shared/testutil:go_default_library",
         "//shared/trieutil:go_default_library",
         "@com_github_gogo_protobuf//proto:go_default_library",
+        "@com_github_google_gofuzz//:go_default_library",
         "@com_github_prysmaticlabs_ethereumapis//eth/v1alpha1:go_default_library",
         "@com_github_prysmaticlabs_go_bitfield//:go_default_library",
         "@com_github_prysmaticlabs_go_ssz//:go_default_library",
diff --git a/beacon-chain/core/blocks/block_operations.go b/beacon-chain/core/blocks/block_operations.go
index bf8abfb76..6dc710474 100644
--- a/beacon-chain/core/blocks/block_operations.go
+++ b/beacon-chain/core/blocks/block_operations.go
@@ -548,6 +548,10 @@ func ProcessAttestationNoVerify(ctx context.Context, beaconState *pb.BeaconState
 	ctx, span := trace.StartSpan(ctx, "core.ProcessAttestationNoVerify")
 	defer span.End()
 
+	if att == nil || att.Data == nil || att.Data.Target == nil {
+		return nil, errors.New("nil attestation data target")
+	}
+
 	data := att.Data
 	if data.Target.Epoch != helpers.PrevEpoch(beaconState) && data.Target.Epoch != helpers.CurrentEpoch(beaconState) {
 		return nil, fmt.Errorf(
diff --git a/beacon-chain/core/blocks/block_operations_fuzz_test.go b/beacon-chain/core/blocks/block_operations_fuzz_test.go
new file mode 100644
index 000000000..eab8e8ad6
--- /dev/null
+++ b/beacon-chain/core/blocks/block_operations_fuzz_test.go
@@ -0,0 +1,37 @@
+package blocks_test
+
+import (
+	"context"
+	"testing"
+
+	fuzz "github.com/google/gofuzz"
+	eth "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/blocks"
+	ethereum_beacon_p2p_v1 "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
+)
+
+func TestFuzzProcessAttestation_10000(t *testing.T) {
+	fuzzer := fuzz.NewWithSeed(0)
+	ctx := context.Background()
+	state := &ethereum_beacon_p2p_v1.BeaconState{}
+	att := &eth.Attestation{}
+
+	for i := 0; i < 10000; i++ {
+		fuzzer.Fuzz(state)
+		fuzzer.Fuzz(att)
+		_, _ = blocks.ProcessAttestationNoVerify(ctx, state, att)
+	}
+}
+
+func TestFuzzProcessBlockHeader_10000(t *testing.T) {
+	fuzzer := fuzz.NewWithSeed(0)
+	state := &ethereum_beacon_p2p_v1.BeaconState{}
+	block := &eth.BeaconBlock{}
+
+	for i := 0; i < 10000; i++ {
+		fuzzer.Fuzz(state)
+		fuzzer.Fuzz(block)
+		_, _ = blocks.ProcessBlockHeader(state, block)
+	}
+}
+
diff --git a/beacon-chain/core/helpers/attestation.go b/beacon-chain/core/helpers/attestation.go
index da1999216..e0df4d249 100644
--- a/beacon-chain/core/helpers/attestation.go
+++ b/beacon-chain/core/helpers/attestation.go
@@ -14,12 +14,6 @@ import (
 )
 
 var (
-	// ErrAttestationDataSlotNilState is returned when a nil state argument
-	// is provided to AttestationDataSlot.
-	ErrAttestationDataSlotNilState = errors.New("nil state provided for AttestationDataSlot")
-	// ErrAttestationDataSlotNilData is returned when a nil attestation data
-	// argument is provided to AttestationDataSlot.
-	ErrAttestationDataSlotNilData = errors.New("nil data provided for AttestationDataSlot")
 	// ErrAttestationAggregationBitsOverlap is returned when two attestations aggregation
 	// bits overlap with each other.
 	ErrAttestationAggregationBitsOverlap = errors.New("overlapping aggregation bits")