bugfix: make Sep10Challenge.verifyTransactionSignatures resilient a…

…gainst account IDs that are not compliant with ed25519 (#440)

### What
Make `Sep10Challenge.verifyTransactionSignatures` resilient against account IDs that are not compliant with ed25519. If a non-compliant account was provided in the list of signers, this account is simply ignored.

Accounts whose ID is not a valid ed25519 public key won't have a signing key, so they can't have signed the challenge transaction.

After the `Sep10Challenge.verifyTransactionSignatures` method finds the intersection between `account IDs that signed the transaction` ∩ `signers provided in the list`, it will return to the caller and the number of accounts and their weight will be verified accordingly.

### Why

Close #439.

CHANGELOG.md

@@ -4,6 +4,10 @@ As this project is pre 1.0, breaking changes may happen for minor version bumps.
 
 ## Pending
 
+## 0.34.1
+
+* Fix the `Sep10Challenge.verifyTransactionSignatures` method to handle/ignore signers that are not ed25519 compliant. ([#440](https://github.com/stellar/java-stellar-sdk/pull/440))
+
 ## 0.34.0
 * Add memo to `Sep10Challenge.newChallenge()` and `Sep10Challenge.readChallengeTransaction`. ([#435](https://github.com/stellar/java-stellar-sdk/pull/435))
 

build.gradle

@@ -13,7 +13,7 @@ plugins {
 }
 
 sourceCompatibility = 1.6
-version = '0.34.0'
+version = '0.34.1'
 group = 'stellar'
 jar.enabled = false
 

src/main/java/org/stellar/sdk/Sep10Challenge.java

@@ -552,7 +552,12 @@ private static Set<String> verifyTransactionSignatures(Transaction transaction,
     }
 
     for (String signer : signers) {
-      KeyPair keyPair = KeyPair.fromAccountId(signer);
+      KeyPair keyPair;
+      try {
+        keyPair = KeyPair.fromAccountId(signer);
+      } catch (RuntimeException e) {
+        continue;
+      }
       SignatureHint hint = keyPair.getSignatureHint();
 
       for (Signature signature : signatures.get(hint)) {

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

@@ -69,7 +69,7 @@ public void testChallenge() throws InvalidSep10ChallengeException {
   }
 
   @Test
-  public void testNewChallengeRejectsMuxedClientAccount() throws InvalidSep10ChallengeException {
+  public void testNewChallengeRejectsMuxedClientAccount() {
     try {
       KeyPair server = KeyPair.random();
 
@@ -1608,6 +1608,38 @@ public void testVerifyChallengeTransactionThresholdValidServerAndMultipleClientK
     assertEquals(new HashSet<String>(Arrays.asList(masterClient.getAccountId(), signerClient1.getAccountId())), signersFound);
   }
 
+  @Test
+  public void testVerifyChallengeTransactionWithAccountIdNonCompliantWithEd25519() throws IOException, InvalidSep10ChallengeException {
+    Network network = Network.TESTNET;
+    KeyPair server = KeyPair.random();
+    KeyPair masterClient = KeyPair.random();
+    long now = System.currentTimeMillis() / 1000L;
+    long end = now + 300;
+    TimeBounds timeBounds = new TimeBounds(now, end);
+    String domainName = "example.com";
+    String webAuthDomain = "example.com";
+
+    Transaction transaction = Sep10Challenge.newChallenge(
+        server,
+        network,
+        masterClient.getAccountId(),
+        domainName,
+        webAuthDomain,
+        timeBounds
+    );
+
+    transaction.sign(masterClient);
+
+    Set<Sep10Challenge.Signer> signers = new HashSet<Sep10Challenge.Signer>(Arrays.asList(
+        new Sep10Challenge.Signer(masterClient.getAccountId(), 2),
+        new Sep10Challenge.Signer("GA2T6GR7VXXXBETTERSAFETHANSORRYXXXPROTECTEDBYLOBSTRVAULT", 1)
+    ));
+
+    int threshold = 2;
+    Set<String> signersFound = Sep10Challenge.verifyChallengeTransactionThreshold(transaction.toEnvelopeXdrBase64(), server.getAccountId(), network, domainName, webAuthDomain, threshold, signers);
+    assertEquals(new HashSet<String>(Collections.singletonList(masterClient.getAccountId())), signersFound);
+  }
+
   @Test
   public void testVerifyChallengeTransactionThresholdValidServerAndMultipleClientKeyMeetingThresholdSomeUnusedIgnorePreauthTxHashAndXHash() throws IOException, InvalidSep10ChallengeException {
     Network network = Network.TESTNET;