payload signer signatures

CHANGELOG.md

@@ -18,6 +18,9 @@ As this project is pre 1.0, breaking changes may happen for minor version bumps.
   * deprecated `addTimeBounds()` use `addPreconditions()` instead
   * deprecated `setTimeout()` use `addPreconditions()` instead
   * deprecated `Transaction.Builder` use TransactionBuilder instead
+* org.stellar.sdk.Transaction
+  * `getSignatures()` returns an ImmutableList of signatures, do NOT add signatures to the collection returned.
+    use `addSignature(DecoratedSignature signature)` instead.
 
 ## 0.31.0
 

src/main/java/org/stellar/sdk/AbstractTransaction.java

@@ -1,7 +1,14 @@
 package org.stellar.sdk;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.io.BaseEncoding;
-import org.stellar.sdk.xdr.*;
+import org.stellar.sdk.xdr.DecoratedSignature;
+import org.stellar.sdk.xdr.Hash;
+import org.stellar.sdk.xdr.SignatureHint;
+import org.stellar.sdk.xdr.TransactionEnvelope;
+import org.stellar.sdk.xdr.TransactionSignaturePayload;
+import org.stellar.sdk.xdr.XdrDataInputStream;
+import org.stellar.sdk.xdr.XdrDataOutputStream;
 
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
@@ -75,14 +82,34 @@ public String hashHex() {
    */
   public abstract byte[] signatureBase();
 
+  /**
+   * Gets the Network string for this transaction.
+   *
+   * @return the Network string
+   */
   public Network getNetwork() {
     return mNetwork;
   }
 
+  /**
+   * Gets read only list(immutable) of the signatures on transaction.
+   *
+   * @return immutable list of signatures
+   */
   public List<DecoratedSignature> getSignatures() {
-    return mSignatures;
+    return ImmutableList.copyOf(mSignatures);
   }
 
+  /**
+   * Adds an additional signature to the transaction's existing list of signatures.
+   *
+   * @param signature the signature to add
+   */
+  public void addSignature(DecoratedSignature signature) {
+    mSignatures.add(signature);
+  }
+
+
   public abstract TransactionEnvelope toEnvelopeXdr();
 
   /**

src/main/java/org/stellar/sdk/KeyPair.java

@@ -9,8 +9,14 @@
 import net.i2p.crypto.eddsa.spec.EdDSANamedCurveTable;
 import net.i2p.crypto.eddsa.spec.EdDSAPrivateKeySpec;
 import net.i2p.crypto.eddsa.spec.EdDSAPublicKeySpec;
-
-import org.stellar.sdk.xdr.*;
+import org.stellar.sdk.xdr.DecoratedSignature;
+import org.stellar.sdk.xdr.PublicKey;
+import org.stellar.sdk.xdr.PublicKeyType;
+import org.stellar.sdk.xdr.SignatureHint;
+import org.stellar.sdk.xdr.SignerKey;
+import org.stellar.sdk.xdr.SignerKeyType;
+import org.stellar.sdk.xdr.Uint256;
+import org.stellar.sdk.xdr.XdrDataOutputStream;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
@@ -21,6 +27,7 @@
 import java.util.Arrays;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+import static java.lang.System.arraycopy;
 
 /**
  * Holds a Stellar keypair.
@@ -227,7 +234,9 @@ public byte[] sign(byte[] data) {
 
   /**
    * Sign the provided data with the keypair's private key and returns {@link DecoratedSignature}.
-   * @param data
+   *
+   * @param data the data to sign, typically the tx hash
+   * @return          DecoratedSignature
    */
   public DecoratedSignature signDecorated(byte[] data) {
     byte[] signatureBytes = this.sign(data);
@@ -241,6 +250,34 @@ public DecoratedSignature signDecorated(byte[] data) {
     return decoratedSignature;
   }
 
+  /**
+   * Sign the provided payload data for payload signer where the input is the data being signed.
+   * Per the <a href="https://github.com/stellar/stellar-protocol/blob/master/core/cap-0040.md#signature-hint" CAP-40 Signature spec</a>
+   * {@link DecoratedSignature}.
+   *
+   * @param signerPayload the payload signers raw data to sign
+   * @return          DecoratedSignature
+   */
+  public DecoratedSignature signPayloadDecorated(byte[] signerPayload) {
+    DecoratedSignature payloadSignature = signDecorated(signerPayload);
+
+    byte[] hint = new byte[4];
+
+    // copy the last four bytes of the payload into the new hint
+    if (signerPayload.length >= hint.length) {
+      arraycopy(signerPayload, signerPayload.length - hint.length, hint, 0, hint.length);
+    } else {
+      arraycopy(signerPayload, 0, hint, 0, signerPayload.length);
+    }
+
+    //XOR the new hint with this keypair's public key hint
+    for (int i = 0; i < hint.length; i++) {
+      hint[i] ^= payloadSignature.getHint().getSignatureHint()[i];
+    }
+    payloadSignature.getHint().setSignatureHint(hint);
+    return payloadSignature;
+  }
+
   /**
    * Verify the provided data and signature match this keypair's public key.
    * @param data The data that was signed.

src/test/java/org/stellar/sdk/KeyPairTest.java

@@ -2,11 +2,15 @@
 
 import org.junit.Assert;
 import org.junit.Test;
+import org.stellar.sdk.xdr.DecoratedSignature;
 
 import java.util.HashMap;
 import java.util.Map;
 
-import static org.junit.Assert.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 public class KeyPairTest {
 
@@ -86,4 +90,26 @@ public void testSignWithoutSecret() {
       assertEquals("KeyPair does not contain secret key. Use KeyPair.fromSecretSeed method to create a new KeyPair with a secret key.", e.getMessage());
     }
   }
+
+  @Test
+  public void testSignPayloadSigner() {
+    KeyPair keypair = KeyPair.fromSecretSeed(Util.hexToBytes(SEED));
+    // the hint from this keypair is [254,66,4,55]
+
+    byte[] payload = new byte[]{1,2,3,4,5};
+    DecoratedSignature sig = keypair.signPayloadDecorated(payload);
+    Assert.assertArrayEquals(sig.getHint().getSignatureHint(), new byte[]{(byte)(0xFF & 252), 65, 0, 50});
+
+  }
+
+  @Test
+  public void testSignPayloadSignerLessThanHint() {
+    KeyPair keypair = KeyPair.fromSecretSeed(Util.hexToBytes(SEED));
+    // the hint from this keypair is [254,66,4,55]
+
+    byte[] payload = new byte[]{1,2,3};
+    DecoratedSignature sig = keypair.signPayloadDecorated(payload);
+    // the hint could only be derived off of 3 bytes from payload
+    Assert.assertArrayEquals(sig.getHint().getSignatureHint(), new byte[]{(byte)(255), 64, 7, 55});
+  }
 }

src/test/java/org/stellar/sdk/Sep10ChallengeTest.java

@@ -3,6 +3,7 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.io.BaseEncoding;
 import org.junit.Test;
+import org.stellar.sdk.xdr.DecoratedSignature;
 import org.stellar.sdk.xdr.EnvelopeType;
 import org.stellar.sdk.xdr.TransactionEnvelope;
 
@@ -238,7 +239,9 @@ public void testReadChallengeTransactionRejectsMuxedClient() throws InvalidSep10
             .addPreconditions(transaction.getPreconditions())
             .build();
 
-    withMuxedClient.getSignatures().addAll(transaction.mSignatures);
+    for (DecoratedSignature signature : transaction.mSignatures) {
+      withMuxedClient.addSignature(signature);
+    }
 
     try {
       Sep10Challenge.readChallengeTransaction(

src/test/java/org/stellar/sdk/TransactionTest.java

@@ -2,6 +2,7 @@
 
 import com.google.common.io.BaseEncoding;
 import org.junit.Test;
+import org.stellar.sdk.xdr.DecoratedSignature;
 import org.stellar.sdk.xdr.EnvelopeType;
 import org.stellar.sdk.xdr.SignerKey;
 import org.stellar.sdk.xdr.XdrDataInputStream;
@@ -15,6 +16,7 @@
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 public class TransactionTest {
 
@@ -56,6 +58,36 @@ public void testParseV0Transaction() throws FormatException, IOException {
 
     }
 
+    @Test
+    public void testAddingSignaturesDirectly() {
+        KeyPair source = KeyPair.fromAccountId("GBBM6BKZPEHWYO3E3YKREDPQXMS4VK35YLNU7NFBRI26RAN7GI5POFBB");
+        KeyPair destination = KeyPair.fromAccountId("GDJJRRMBK4IWLEPJGIE6SXD2LP7REGZODU7WDC3I2D6MR37F4XSHBKX2");
+
+        Account account = new Account(source.getAccountId(), 0L);
+
+        Transaction transaction = new Transaction(
+                AccountConverter.disableMuxed(),
+                account.getAccountId(),
+                Transaction.MIN_BASE_FEE,
+                account.getIncrementedSequenceNumber(),
+                new org.stellar.sdk.Operation[]{new CreateAccountOperation.Builder(destination.getAccountId(), "2000").build()},
+                null,
+                new TransactionPreconditions(null, null, 0, 0, new ArrayList<SignerKey>(),null),
+                Network.PUBLIC
+        );
+
+        assertEquals(0, transaction.getSignatures().size());
+        try {
+            // should not be able to change the list of signatures directly
+            transaction.getSignatures().add(new DecoratedSignature());
+            fail();
+        } catch (UnsupportedOperationException ignored) {}
+
+        // should only be able to add signatures through interface
+        transaction.addSignature(new DecoratedSignature());
+        assertEquals(1, transaction.getSignatures().size());
+    }
+
     @Test
     public void testSha256HashSigning() throws FormatException {
         KeyPair source = KeyPair.fromAccountId("GBBM6BKZPEHWYO3E3YKREDPQXMS4VK35YLNU7NFBRI26RAN7GI5POFBB");