fix: sign legacy second signature over the signed transaction hash

src/Transactions/Deserializer.php

@@ -76,7 +76,9 @@ public function deserialize(): AbstractTransaction
             $data['s'] = $this->parseHex($decodedRlp[8]);
         }
 
-        // TODO: second signature handling
+        if (count($decodedRlp) === 10) {
+            $data['legacySecondSignature'] = $this->parseHex($decodedRlp[9]);
+        }
 
         $transaction = $this->guessTransactionFromData($data);
 

src/Transactions/Types/AbstractTransaction.php

@@ -16,9 +16,15 @@
 use BitWasp\Bitcoin\Crypto\EcAdapter\Signature\CompactSignatureInterface;
 use BitWasp\Buffertools\Buffer;
 use BitWasp\Buffertools\BufferInterface;
+use kornrunner\Keccak;
 
 abstract class AbstractTransaction
 {
+    /**
+     * 0x8f ‖ "MAINSAIL_LSS_V1".
+     */
+    private const LEGACY_SECOND_SIGNATURE_DOMAIN = '8f4d41494e5341494c5f4c53535f5631';
+
     public array $data;
 
     public Buffer $serialized;
@@ -60,9 +66,13 @@ public function sign(PrivateKey $privateKey): static
 
     public function legacySecondSign(PrivateKey $privateKey): static
     {
-        $hash = $this->hash(skipSignature: true);
+        if (! isset($this->data['v'], $this->data['r'], $this->data['s']) || $this->data['v'] === '') {
+            throw new \RuntimeException('Transaction must be signed before adding a legacy second signature');
+        }
+
+        $hash = Keccak::hash(hex2bin(self::LEGACY_SECOND_SIGNATURE_DOMAIN.$this->hash()->getHex()), 256);
 
-        $this->data['legacySecondSignature'] = $privateKey->signToEcdsa($hash);
+        $this->data['legacySecondSignature'] = $privateKey->signToEcdsa(Buffer::hex($hash));
 
         return $this;
     }

src/Utils/TransactionUtils.php

@@ -18,8 +18,9 @@ class TransactionUtils
      *
      * @param array $transaction The transaction data.
      * @param bool $skipSignature
+     * @param bool $skipLegacySecondSignature
      */
-    public static function toBuffer(array $transaction, bool $skipSignature = false): Buffer
+    public static function toBuffer(array $transaction, bool $skipSignature = false, bool $skipLegacySecondSignature = false): Buffer
     {
         $fields = [
             self::toBeArray(isset($transaction['nonce']) ? $transaction['nonce'] : 0),
@@ -34,10 +35,10 @@ public static function toBuffer(array $transaction, bool $skipSignature = false)
 
         if (! $skipSignature && isset($transaction['v'], $transaction['r'], $transaction['s']) && $transaction['v'] !== '') {
             $fields[] = self::toBeArray($transaction['v'] + Network::get()->chainId() * 2 + 35);
-            $fields[] = '0x'.$transaction['r'];
-            $fields[] = '0x'.$transaction['s'];
+            $fields[] = self::stripLeadingZeroBytes($transaction['r']);
+            $fields[] = self::stripLeadingZeroBytes($transaction['s']);
 
-            if (isset($transaction['legacySecondSignature'])) {
+            if (isset($transaction['legacySecondSignature']) && ! $skipLegacySecondSignature) {
                 $fields[] = '0x'.$transaction['legacySecondSignature'];
             }
         } else {
@@ -47,8 +48,6 @@ public static function toBuffer(array $transaction, bool $skipSignature = false)
             $fields[] = self::toBeArray(0);
         }
 
-        // TODO: second signature handling
-
         $encoded = RlpEncoder::encode($fields);
 
         return new Buffer(hex2bin(substr($encoded, 2)));
@@ -62,13 +61,22 @@ public static function toBuffer(array $transaction, bool $skipSignature = false)
      */
     public static function toHash(array $transaction, bool $skipSignature = false): BufferInterface
     {
-        $encoding = self::toBuffer($transaction, $skipSignature);
+        // The transaction hash never covers the legacy second signature
+        $encoding = self::toBuffer($transaction, $skipSignature, skipLegacySecondSignature: true);
 
         $keccak = Keccak::hash($encoding->getBinary(), 256);
 
         return Buffer::hex($keccak);
     }
 
+    /**
+     * Strips the leading zero bytes so `r` and `s` are encoded as minimal integers.
+     */
+    private static function stripLeadingZeroBytes(string $hex): string
+    {
+        return '0x'.preg_replace('/^(00)+/', '', $hex);
+    }
+
     /**
      * Converts a big integer to a big-endian byte array.
      *

tests/Unit/Transactions/LegacySecondSignatureTest.php

@@ -0,0 +1,67 @@
+<?php
+
+declare(strict_types=1);
+
+use ArkEcosystem\Crypto\Configuration\Network;
+use ArkEcosystem\Crypto\Identities\PrivateKey;
+use ArkEcosystem\Crypto\Networks\Testnet;
+use ArkEcosystem\Crypto\Transactions\Deserializer;
+use ArkEcosystem\Crypto\Transactions\Types\Transfer;
+
+// Test vector from the Mainsail LSS v1 spec, built for chain 10_000
+beforeEach(function () {
+    $this->fixture = $this->getTransactionFixture('evm_call', 'transfer-legacy-second-signature-vector');
+
+    Network::set(new class($this->fixture['chainId']) extends Testnet {
+        public function __construct(private readonly int $id)
+        {
+            parent::__construct();
+        }
+
+        public function chainId(): int
+        {
+            return $this->id;
+        }
+    });
+
+    $this->unsignedData = array_diff_key($this->fixture['data'], array_flip(['legacySecondSignature', 'hash']));
+});
+
+it('should sign the hash of the signed transaction with the second key', function () {
+    $transaction = new Transfer($this->unsignedData);
+
+    $transaction->sign(PrivateKey::fromHex($this->fixture['privateKey']));
+
+    expect($transaction->serialize()->getHex())->toBe($this->fixture['signed']);
+    expect($transaction->hash()->getHex())->toBe($this->fixture['data']['hash']);
+
+    $transaction->legacySecondSign(PrivateKey::fromHex($this->fixture['secondPrivateKey']));
+
+    expect($transaction->data['legacySecondSignature'])->toBe($this->fixture['data']['legacySecondSignature']);
+    expect($transaction->serialize()->getHex())->toBe($this->fixture['serialized']);
+    expect($transaction->hash()->getHex())->toBe($this->fixture['data']['hash']);
+});
+
+it('should use a 0 or 1 recovery id', function () {
+    $transaction = new Transfer($this->unsignedData);
+
+    $transaction->sign(PrivateKey::fromHex($this->fixture['privateKey']));
+    $transaction->legacySecondSign(PrivateKey::fromHex($this->fixture['secondPrivateKey']));
+
+    expect(substr($transaction->data['legacySecondSignature'], -2))->toBeIn(['00', '01']);
+});
+
+it('should require the primary signature first', function () {
+    $transaction = new Transfer($this->unsignedData);
+
+    $transaction->legacySecondSign(PrivateKey::fromHex($this->fixture['secondPrivateKey']));
+})->throws(RuntimeException::class, 'Transaction must be signed before adding a legacy second signature');
+
+it('should deserialize and hash only the first 9 fields', function () {
+    $transaction = Deserializer::new($this->fixture['serialized'])->deserialize();
+
+    expect($transaction->data['legacySecondSignature'])->toBe($this->fixture['data']['legacySecondSignature']);
+    expect($transaction->data['hash'])->toBe($this->fixture['data']['hash']);
+    expect($transaction->serialize()->getHex())->toBe($this->fixture['serialized']);
+    expect($transaction->verify())->toBeTrue();
+});

tests/fixtures/transactions/evm_call/transfer-legacy-second-signature-vector.json

@@ -0,0 +1,17 @@
+{
+	"chainId": 10000,
+	"privateKey": "314f59dbc54460b18fc036d67dac36ad6e1fa1c3c0e0b3427a84e43faabfcecb",
+	"secondPrivateKey": "4427335cab240f6cc651b1df5ce5ff489c5a0bcb952507b542afe8f6c90e98e7",
+	"data": {
+		"nonce": "0",
+		"gasPrice": "5000000000",
+		"gasLimit": "21000",
+		"to": "0x0DFeDD974c2e58Dc8E292ec159d1DC9AdeaFb1C0",
+		"value": "1000000000000000000",
+		"data": "",
+		"legacySecondSignature": "ea77adb968255ec1570c0e48cede8cceec3a9aff29e9dac1c53c2a6de4f2a18740df289edfcdfe97a189975cba8945334e5f230d66232751e468c5500dbe7dec01",
+		"hash": "27af7a389f34f32569c90815ced4e23e8770eb2d77ace6f29dabec1a10bef205"
+	},
+	"signed": "f86e8085012a05f200825208940dfedd974c2e58dc8e292ec159d1dc9adeafb1c0880de0b6b3a764000080824e44a00f4f4ac7f1effa669ea1a8970ed37f367e4aa0b549636619feead2d4a2408ffca04492af59379f74385bd951d229456b3b23ead33ce1d10106535c6830a688733d",
+	"serialized": "f8b18085012a05f200825208940dfedd974c2e58dc8e292ec159d1dc9adeafb1c0880de0b6b3a764000080824e44a00f4f4ac7f1effa669ea1a8970ed37f367e4aa0b549636619feead2d4a2408ffca04492af59379f74385bd951d229456b3b23ead33ce1d10106535c6830a688733db841ea77adb968255ec1570c0e48cede8cceec3a9aff29e9dac1c53c2a6de4f2a18740df289edfcdfe97a189975cba8945334e5f230d66232751e468c5500dbe7dec01"
+}

tests/fixtures/transactions/evm_call/transfer-legacy-second-signature.json

@@ -10,10 +10,10 @@
 		"v": 0,
 		"r": "a1f79cb40a4bb409d6cebd874002ceda3ec0ccb614c1d8155f5c2f7f798135f9",
 		"s": "2d2ef517aaf6feed747385e260c206f46b2ce9d6b2a585427a111685a097bd79",
-		"legacySecondSignature": "094b33b2d10c4d48cff9a9b10f79990c9a902a762b00d2f2a4d2ddad7823b59332b2da193265068c67cefea9ca8bc84e47acec406f3300a0a10b77a56ea8c18801",
+		"legacySecondSignature": "a7576f15a3eb2b4cb54b83e97d25b70c88efb63c783120b81ab0eb4a958631d444347954726642779f019de3db05f568e78915b7f9cf319f7deb093353fa245b01",
 		"senderPublicKey": "0243333347c8cbf4e3cbc7a96964181d02a2b0c854faa2fef86b4b8d92afcf473d",
 		"from": "0x1E6747BEAa5B4076a6A98D735DF8c35a70D18Bdd",
 		"hash": "a39435ec5de418e77479856d06a653efc171afe43e091472af22ee359eeb83be"
 	},
-	"serialized": "f8ad0185012a05f200825208946f0182a0cc707b055322ccf6d4cb6a5aff1aeb228405f5e10080825c6ba0a1f79cb40a4bb409d6cebd874002ceda3ec0ccb614c1d8155f5c2f7f798135f9a02d2ef517aaf6feed747385e260c206f46b2ce9d6b2a585427a111685a097bd79b841094b33b2d10c4d48cff9a9b10f79990c9a902a762b00d2f2a4d2ddad7823b59332b2da193265068c67cefea9ca8bc84e47acec406f3300a0a10b77a56ea8c18801"
+	"serialized": "f8ad0185012a05f200825208946f0182a0cc707b055322ccf6d4cb6a5aff1aeb228405f5e10080825c6ba0a1f79cb40a4bb409d6cebd874002ceda3ec0ccb614c1d8155f5c2f7f798135f9a02d2ef517aaf6feed747385e260c206f46b2ce9d6b2a585427a111685a097bd79b841a7576f15a3eb2b4cb54b83e97d25b70c88efb63c783120b81ab0eb4a958631d444347954726642779f019de3db05f568e78915b7f9cf319f7deb093353fa245b01"
 }