Add `go-fuzz`

:broom:

.changeset/large-falcons-remain.md

+---
+'@eth-optimism/contracts-bedrock': patch
+---
+
+Adds a go package to generate fuzz inputs for the Bedrock contract tests.

go.work

@@ -19,6 +19,7 @@ use (
 	./op-proposer
 	./op-service
 	./proxyd
+	./packages/contracts-bedrock/go-fuzz
 )
 
 replace github.com/ethereum/go-ethereum v1.10.26 => github.com/ethereum-optimism/op-geth v0.0.0-20221205191237-0678a130d790

packages/contracts-bedrock/.gitignore

@@ -10,3 +10,4 @@ src/contract-artifacts.ts
 tmp-artifacts
 deployments/mainnet-forked
 deploy-config/mainnet-forked.json
+go-fuzz/fuzz

packages/contracts-bedrock/go-fuzz/README.md

+# `go-fuzz`
+
+A lightweight input fuzzing utility used for testing various Bedrock contracts.
+
+<pre>
+├── go-fuzz
+│   ├── <a href="./cmd">cmd</a>: `go-fuzz`'s binary
+│   └── <a href="./trie">trie</a>: Utility for generating random merkle trie roots / inclusion proofs
+</pre>
+
+## Usage
+
+To generate an abi-encoded fuzz case, pass in a mode via the `-m` flag as well as an optional variant via the `-v` flag.
+
+### Available Modes
+
+#### `trie`
+
+> **Note**
+> Variant required for `trie` mode.
+
+| Variant                       | Description                                                                                                                               |
+| ----------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------- |
+| `valid`                       | Generate a test case with a valid proof of inclusion for the k/v pair in the trie.                                                        |
+| `extra_proof_elems`           | Generate an invalid test case with an extra proof element attached to an otherwise valid proof of inclusion for the passed k/v.           |
+| `corrupted_proof`             | Generate an invalid test case where the proof is malformed.                                                                               |
+| `invalid_data_remainder`      | Generate an invalid test case where a random element of the proof has more bytes than the length designates within the RLP list encoding. |
+| `invalid_large_internal_hash` | Generate an invalid test case where a long proof element is incorrect for the root.                                                       |
+| `invalid_internal_node_hash`  | Generate an invalid test case where a small proof element is incorrect for the root.                                                      |
+| `prefixed_valid_key`          | Generate a valid test case with a key that has been given a random prefix                                                                 |
+| `empty_key`                   | Generate a valid test case with a proof of inclusion for an empty key.                                                                    |
+| `partial_proof`               | Generate an invalid test case with a partially correct proof                                                                              |

packages/contracts-bedrock/go-fuzz/cmd/fuzz.go

+package main
+
+import (
+	"flag"
+	"log"
+
+	t "github.com/ethereum-optimism/optimism/packages/contracts-bedrock/go-fuzz/trie"
+)
+
+// Mode enum
+const (
+	// Enables the `trie` fuzzer
+	trie string = "trie"
+)
+
+func main() {
+	mode := flag.String("m", "", "Fuzzer mode")
+	variant := flag.String("v", "", "Mode variant")
+	flag.Parse()
+
+	if len(*mode) < 1 {
+		log.Fatal("Must pass a mode for the fuzzer!")
+	}
+
+	switch *mode {
+	case trie:
+		t.FuzzTrie(*variant)
+	default:
+		log.Fatal("Invalid mode!")
+	}
+}

packages/contracts-bedrock/go-fuzz/go.mod

+module github.com/ethereum-optimism/optimism/packages/contracts-bedrock/go-fuzz
+
+go 1.19
+
+require github.com/ethereum/go-ethereum v1.10.26
+
+require (
+	github.com/StackExchange/wmi v0.0.0-20180116203802-5d049714c4a6 // indirect
+	github.com/VictoriaMetrics/fastcache v1.6.0 // indirect
+	github.com/btcsuite/btcd/btcec/v2 v2.2.0 // indirect
+	github.com/cespare/xxhash/v2 v2.1.1 // indirect
+	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.0.1 // indirect
+	github.com/go-ole/go-ole v1.2.1 // indirect
+	github.com/go-stack/stack v1.8.0 // indirect
+	github.com/golang/snappy v0.0.4 // indirect
+	github.com/mattn/go-runewidth v0.0.9 // indirect
+	github.com/olekukonko/tablewriter v0.0.5 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/prometheus/tsdb v0.7.1 // indirect
+	github.com/shirou/gopsutil v3.21.4-0.20210419000835-c7a38de76ee5+incompatible // indirect
+	github.com/syndtr/goleveldb v1.0.1-0.20210819022825-2ae1ddf74ef7 // indirect
+	github.com/tklauser/go-sysconf v0.3.5 // indirect
+	github.com/tklauser/numcpus v0.2.2 // indirect
+	golang.org/x/crypto v0.0.0-20210921155107-089bfa567519 // indirect
+	golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a // indirect
+)

packages/contracts-bedrock/go-fuzz/trie/trie.go

+package trie
+
+import (
+	"crypto/rand"
+	"fmt"
+	"log"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/accounts/abi"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/ethereum/go-ethereum/ethdb/memorydb"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/trie"
+)
+
+// Variant enum
+const (
+	// Generate a test case with a valid proof of inclusion for the k/v pair in the trie.
+	valid string = "valid"
+	// Generate an invalid test case with an extra proof element attached to an otherwise
+	// valid proof of inclusion for the passed k/v.
+	extraProofElems = "extra_proof_elems"
+	// Generate an invalid test case where the proof is malformed.
+	corruptedProof = "corrupted_proof"
+	// Generate an invalid test case where a random element of the proof has more bytes than the
+	// length designates within the RLP list encoding.
+	invalidDataRemainder = "invalid_data_remainder"
+	// Generate an invalid test case where a long proof element is incorrect for the root.
+	invalidLargeInternalHash = "invalid_large_internal_hash"
+	// Generate an invalid test case where a small proof element is incorrect for the root.
+	invalidInternalNodeHash = "invalid_internal_node_hash"
+	// Generate a valid test case with a key that has been given a random prefix
+	prefixedValidKey = "prefixed_valid_key"
+	// Generate a valid test case with a proof of inclusion for an empty key.
+	emptyKey = "empty_key"
+	// Generate an invalid test case with a partially correct proof
+	partialProof = "partial_proof"
+)
+
+// Generate an abi-encoded `trieTestCase` of a specified variant
+func FuzzTrie(variant string) {
+	if len(variant) < 1 {
+		log.Fatal("Must pass a variant to the trie fuzzer!")
+	}
+
+	var testCase trieTestCase
+	switch variant {
+	case valid:
+		testCase = genTrieTestCase(false)
+		break
+	case extraProofElems:
+		testCase = genTrieTestCase(false)
+		// Duplicate the last element of the proof
+		testCase.Proof = append(testCase.Proof, [][]byte{testCase.Proof[len(testCase.Proof)-1]}...)
+		break
+	case corruptedProof:
+		testCase = genTrieTestCase(false)
+
+		// Re-encode a random element within the proof
+		idx := randRange(0, int64(len(testCase.Proof)))
+		encoded, _ := rlp.EncodeToBytes(testCase.Proof[idx])
+		testCase.Proof[idx] = encoded
+		break
+	case invalidDataRemainder:
+		testCase = genTrieTestCase(false)
+
+		// Alter true length of random proof element by appending random bytes
+		// Do not update the encoded length
+		idx := randRange(0, int64(len(testCase.Proof)))
+		bytes := make([]byte, randRange(1, 512))
+		rand.Read(bytes)
+		testCase.Proof[idx] = append(testCase.Proof[idx], bytes...)
+		break
+	case invalidLargeInternalHash:
+		testCase = genTrieTestCase(false)
+
+		// Clobber 4 bytes within a list element of a random proof element
+		// TODO: Improve this by decoding the proof elem and choosing random
+		// bytes to overwrite.
+		idx := randRange(1, int64(len(testCase.Proof)))
+		b := make([]byte, 4)
+		rand.Read(b)
+		testCase.Proof[idx] = append(
+			testCase.Proof[idx][:20],
+			append(
+				b,
+				testCase.Proof[idx][24:]...,
+			)...,
+		)
+
+		break
+	case invalidInternalNodeHash:
+		testCase = genTrieTestCase(false)
+		// Assign the last proof element to an encoded list containing a
+		// random 29 byte value
+		b := make([]byte, 29)
+		rand.Read(b)
+		e, _ := rlp.EncodeToBytes(b)
+		testCase.Proof[len(testCase.Proof)-1] = append([]byte{0xc0 + 30}, e...)
+		break
+	case prefixedValidKey:
+		testCase = genTrieTestCase(false)
+
+		bytes := make([]byte, randRange(1, 16))
+		rand.Read(bytes)
+		testCase.Key = append(bytes, testCase.Key...)
+		break
+	case emptyKey:
+		testCase = genTrieTestCase(true)
+		break
+	case partialProof:
+		testCase = genTrieTestCase(false)
+
+		// Cut the proof in half
+		proofLen := len(testCase.Proof)
+		newProof := make([][]byte, proofLen/2)
+		for i := 0; i < proofLen/2; i++ {
+			newProof[i] = testCase.Proof[i]
+		}
+
+		testCase.Proof = newProof
+		break
+	default:
+		log.Fatal("Invalid variant passed to trie fuzzer!")
+	}
+
+	// Print encoded test case with no newline so that foundry's FFI can read the output
+	fmt.Print(testCase.AbiEncode())
+}
+
+// Generate a random test case for Bedrock's MerkleTrie verifier.
+func genTrieTestCase(selectEmptyKey bool) trieTestCase {
+	// Create an empty merkle trie
+	memdb := memorydb.New()
+	randTrie := trie.NewEmpty(trie.NewDatabase(memdb))
+
+	// Get a random number of elements to put into the trie
+	randN := randRange(2, 1024)
+	// Get a random key/value pair to generate a proof of inclusion for
+	randSelect := randRange(0, randN)
+
+	// Create a fixed-length key as well as a randomly-sized value
+	// We create these out of the loop to reduce mem allocations.
+	randKey := make([]byte, 32)
+	randValue := make([]byte, randRange(2, 1024))
+
+	// Randomly selected key/value for proof generation
+	var key []byte
+	var value []byte
+
+	// Add `randN` elements to the trie
+	for i := int64(0); i < randN; i++ {
+		// Randomize the contents of `randKey` and `randValue`
+		rand.Read(randKey)
+		rand.Read(randValue)
+
+		// Clear the selected key if `selectEmptyKey` is true
+		if i == randSelect && selectEmptyKey {
+			randKey = make([]byte, 0)
+		}
+
+		// Insert the random k/v pair into the trie
+		if err := randTrie.TryUpdate(randKey, randValue); err != nil {
+			log.Fatal("Error adding key-value pair to trie")
+		}
+
+		// If this is our randomly selected k/v pair, store it in `key` & `value`
+		if i == randSelect {
+			key = randKey
+			value = randValue
+		}
+	}
+
+	// Generate proof for `key`'s inclusion in our trie
+	var proof proofList
+	if err := randTrie.Prove(key, 0, &proof); err != nil {
+		log.Fatal("Error creating proof for randomly selected key's inclusion in generated trie")
+	}
+
+	// Create our test case with the data collected
+	testCase := trieTestCase{
+		Root:  randTrie.Hash(),
+		Key:   key,
+		Value: value,
+		Proof: proof,
+	}
+
+	return testCase
+}
+
+// Represents a test case for bedrock's `MerkleTrie.sol`
+type trieTestCase struct {
+	Root  common.Hash
+	Key   []byte
+	Value []byte
+	Proof [][]byte
+}
+
+// Tuple type to encode `TrieTestCase`
+var (
+	trieTestCaseTuple, _ = abi.NewType("tuple", "TrieTestCase", []abi.ArgumentMarshaling{
+		{Name: "root", Type: "bytes32"},
+		{Name: "key", Type: "bytes"},
+		{Name: "value", Type: "bytes"},
+		{Name: "proof", Type: "bytes[]"},
+	})
+
+	encoder = abi.Arguments{
+		{Type: trieTestCaseTuple},
+	}
+)
+
+// Encodes the trieTestCase as the `trieTestCaseTuple`.
+func (t *trieTestCase) AbiEncode() string {
+	// Encode the contents of the struct as a tuple
+	packed, err := encoder.Pack(&t)
+	if err != nil {
+		log.Fatalf("Error packing TrieTestCase: %v", err)
+	}
+
+	// Remove the pointer and encode the packed bytes as a hex string
+	return hexutil.Encode(packed[32:])
+}
+
+// Helper that generates a cryptographically secure random 64-bit integer
+// between the range [min, max)
+func randRange(min int64, max int64) int64 {
+	r, err := rand.Int(rand.Reader, new(big.Int).Sub(new(big.Int).SetInt64(max), new(big.Int).SetInt64(min)))
+	if err != nil {
+		log.Fatal("Failed to generate random number within bounds")
+	}
+
+	return (new(big.Int).Add(r, new(big.Int).SetInt64(min))).Int64()
+}
+
+// Custom type to write the generated proof to
+type proofList [][]byte
+
+func (n *proofList) Put(key []byte, value []byte) error {
+	*n = append(*n, value)
+	return nil
+}
+
+func (n *proofList) Delete(key []byte) error {
+	panic("not supported")
+}