test(eip8141): pin blob-carrying frame-tx signature-hash coverage

Author: Marchhill

src/Nethermind/Nethermind.Core.Test/Encoding/FrameTxDecoderTests.cs

@@ -109,6 +109,30 @@ public void ComputeSigHash_FrameFieldChanges_HashChanges()
         Assert.That(FrameTxSigHash.ComputeValue(second), Is.Not.EqualTo(FrameTxSigHash.ComputeValue(first)));
     }
 
+    [Test]
+    public void ComputeSigHash_MaxFeePerBlobGasChanges_HashChanges()
+    {
+        // The blob fields are the last two elements of the signing preimage (matching EELS #3047's
+        // FrameTransaction layout); the signature must commit to them.
+        Transaction first = CreateFrameTx();
+        first.MaxFeePerBlobGas = 7;
+        Transaction second = CreateFrameTx();
+        second.MaxFeePerBlobGas = 8;
+
+        Assert.That(FrameTxSigHash.ComputeValue(second), Is.Not.EqualTo(FrameTxSigHash.ComputeValue(first)));
+    }
+
+    [Test]
+    public void ComputeSigHash_BlobVersionedHashesChange_HashChanges()
+    {
+        Transaction first = CreateFrameTx();
+        first.BlobVersionedHashes = [FilledBytes(32, 0x01)];
+        Transaction second = CreateFrameTx();
+        second.BlobVersionedHashes = [FilledBytes(32, 0x02)];
+
+        Assert.That(FrameTxSigHash.ComputeValue(second), Is.Not.EqualTo(FrameTxSigHash.ComputeValue(first)));
+    }
+
     private static IEnumerable<TestCaseData> RoundtripCases()
     {
         yield return new TestCaseData(CreateFrameTx()).SetName("Roundtrip_MinimalSingleFrame");

src/Nethermind/Nethermind.Evm.Test/FrameTxSignatureValidatorTests.cs

@@ -49,6 +49,36 @@ public void Validate_Secp256k1SignsCanonicalHashWithExplicitSigner_ReturnsTrue()
         Assert.That(error, Is.Null);
     }
 
+    [Test]
+    public void Validate_Secp256k1BlobCarryingTx_ReturnsTrueAndResolvesSigner()
+    {
+        // A blob-carrying frame tx: the blob fields are in the sig-hash preimage (EIP-8141 /
+        // EELS #3047), so a signature computed over that hash validates and resolves the signer.
+        Transaction tx = CreateFrameTx();
+        tx.MaxFeePerBlobGas = 3;
+        tx.BlobVersionedHashes = [BlobVersionedHash(0x01), BlobVersionedHash(0x02)];
+        tx.FrameSignatures = [Secp256k1Entry(tx, TestItem.PrivateKeyB, signer: TestItem.PrivateKeyB.Address)];
+
+        Assert.That(Validate(tx, out string? error), Is.True);
+        Assert.That(error, Is.Null);
+    }
+
+    [Test]
+    public void Validate_BlobFieldTamperedAfterSigning_ReturnsFalse()
+    {
+        // The signature commits to the blob fields; mutating one after signing must invalidate it,
+        // proving the sig-hash preimage covers max_fee_per_blob_gas and blob_versioned_hashes.
+        Transaction tx = CreateFrameTx();
+        tx.MaxFeePerBlobGas = 3;
+        tx.BlobVersionedHashes = [BlobVersionedHash(0x01)];
+        tx.FrameSignatures = [Secp256k1Entry(tx, TestItem.PrivateKeyB, signer: TestItem.PrivateKeyB.Address)];
+
+        tx.BlobVersionedHashes = [BlobVersionedHash(0x02)];
+
+        Assert.That(Validate(tx, out string? error), Is.False);
+        Assert.That(error, Is.EqualTo(FrameTxSignatureValidator.InvalidSignature));
+    }
+
     [Test]
     public void Validate_Secp256k1WithAbsentSigner_ResolvesToTxSender()
     {
@@ -327,6 +357,13 @@ private static byte[] ToVrs(Signature signature)
         return bytes;
     }
 
+    private static byte[] BlobVersionedHash(byte fill)
+    {
+        byte[] hash = new byte[Hash256.Size];
+        hash.AsSpan().Fill(fill);
+        return hash;
+    }
+
     private static byte[] Pad32(byte[] value)
     {
         if (value.Length == 32) return value;