From 8335b0ef0333e0e7e7204182783fa05cc93dff7d Mon Sep 17 00:00:00 2001
From: Moxie Marlinspike <moxie@thoughtcrime.org>
Date: Mon, 6 Apr 2015 12:28:16 -0700
Subject: Throw NoSessionException in GroupCipher decrypt()

---
 .../libaxolotl/groups/GroupCipher.java             | 12 ++++++++---
 .../libaxolotl/groups/GroupCipherTest.java         | 24 ++++++++++++++++++++++
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/java/src/main/java/org/whispersystems/libaxolotl/groups/GroupCipher.java b/java/src/main/java/org/whispersystems/libaxolotl/groups/GroupCipher.java
index 55e261ac..cac2ccd8 100644
--- a/java/src/main/java/org/whispersystems/libaxolotl/groups/GroupCipher.java
+++ b/java/src/main/java/org/whispersystems/libaxolotl/groups/GroupCipher.java
@@ -102,7 +102,7 @@ public class GroupCipher {
    * @throws DuplicateMessageException
    */
   public byte[] decrypt(byte[] senderKeyMessageBytes)
-      throws LegacyMessageException, DuplicateMessageException, InvalidMessageException
+      throws LegacyMessageException, DuplicateMessageException, InvalidMessageException, NoSessionException
   {
     return decrypt(senderKeyMessageBytes, new NullDecryptionCallback());
   }
@@ -123,11 +123,17 @@ public class GroupCipher {
    * @throws DuplicateMessageException
    */
   public byte[] decrypt(byte[] senderKeyMessageBytes, DecryptionCallback callback)
-      throws LegacyMessageException, InvalidMessageException, DuplicateMessageException
+      throws LegacyMessageException, InvalidMessageException, DuplicateMessageException,
+             NoSessionException
   {
     synchronized (LOCK) {
       try {
-        SenderKeyRecord  record           = senderKeyStore.loadSenderKey(senderKeyId);
+        SenderKeyRecord record = senderKeyStore.loadSenderKey(senderKeyId);
+
+        if (record.isEmpty()) {
+          throw new NoSessionException("No sender key for: " + senderKeyId);
+        }
+
         SenderKeyMessage senderKeyMessage = new SenderKeyMessage(senderKeyMessageBytes);
         SenderKeyState   senderKeyState   = record.getSenderKeyState(senderKeyMessage.getKeyId());
 
diff --git a/tests/src/test/java/org/whispersystems/libaxolotl/groups/GroupCipherTest.java b/tests/src/test/java/org/whispersystems/libaxolotl/groups/GroupCipherTest.java
index 32fcc652..aad8b083 100644
--- a/tests/src/test/java/org/whispersystems/libaxolotl/groups/GroupCipherTest.java
+++ b/tests/src/test/java/org/whispersystems/libaxolotl/groups/GroupCipherTest.java
@@ -18,6 +18,30 @@ public class GroupCipherTest extends TestCase {
   private static final AxolotlAddress SENDER_ADDRESS = new AxolotlAddress("+14150001111", 1);
   private static final SenderKeyName  GROUP_SENDER   = new SenderKeyName("nihilist history reading group", SENDER_ADDRESS);
 
+  public void testNoSession() throws InvalidMessageException, LegacyMessageException, NoSessionException, DuplicateMessageException {
+    InMemorySenderKeyStore aliceStore = new InMemorySenderKeyStore();
+    InMemorySenderKeyStore bobStore   = new InMemorySenderKeyStore();
+
+    GroupSessionBuilder aliceSessionBuilder = new GroupSessionBuilder(aliceStore);
+    GroupSessionBuilder bobSessionBuilder   = new GroupSessionBuilder(bobStore);
+
+    GroupCipher aliceGroupCipher = new GroupCipher(aliceStore, GROUP_SENDER);
+    GroupCipher bobGroupCipher   = new GroupCipher(bobStore, GROUP_SENDER);
+
+    SenderKeyDistributionMessage sentAliceDistributionMessage     = aliceSessionBuilder.create(GROUP_SENDER);
+    SenderKeyDistributionMessage receivedAliceDistributionMessage = new SenderKeyDistributionMessage(sentAliceDistributionMessage.serialize());
+
+//    bobSessionBuilder.process(GROUP_SENDER, receivedAliceDistributionMessage);
+
+    byte[] ciphertextFromAlice = aliceGroupCipher.encrypt("smert ze smert".getBytes());
+    try {
+      byte[] plaintextFromAlice  = bobGroupCipher.decrypt(ciphertextFromAlice);
+      throw new AssertionError("Should be no session!");
+    } catch (NoSessionException e) {
+      // good
+    }
+  }
+
   public void testBasicEncryptDecrypt()
       throws LegacyMessageException, DuplicateMessageException, InvalidMessageException, NoSessionException
   {
-- 
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