[msg] Fix counter init. (#12948)

project-chip · Mar 25, 2022 · 1724178 · 1724178
1 parent ddfbda5
commit 1724178
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Showing 3 changed files with 18 additions and 17 deletions.
diff --git a/src/transport/MessageCounter.cpp b/src/transport/MessageCounter.cpp
@@ -29,7 +29,7 @@ namespace chip {
 
 void GlobalUnencryptedMessageCounter::Init()
 {
-    value = Crypto::GetRandU32();
+    mValue = Crypto::GetRandU32();
 }
 
 CHIP_ERROR GlobalEncryptedMessageCounter::Init()

diff --git a/src/transport/MessageCounter.h b/src/transport/MessageCounter.h
@@ -56,20 +56,20 @@ class MessageCounter
 class GlobalUnencryptedMessageCounter : public MessageCounter
 {
 public:
-    GlobalUnencryptedMessageCounter() : value(0) {}
+    GlobalUnencryptedMessageCounter() : mValue(0) {}
 
     void Init();
 
     Type GetType() override { return GlobalUnencrypted; }
-    uint32_t Value() override { return value; }
+    uint32_t Value() override { return mValue; }
     CHIP_ERROR Advance() override
     {
-        ++value;
+        ++mValue;
         return CHIP_NO_ERROR;
     }
 
 private:
-    uint32_t value;
+    uint32_t mValue;
 };
 
 class GlobalEncryptedMessageCounter : public MessageCounter
@@ -88,44 +88,45 @@ class GlobalEncryptedMessageCounter : public MessageCounter
 #else
     struct FakePersistedCounter
     {
-        FakePersistedCounter() : value(0) {}
+        FakePersistedCounter() : mValue(0) {}
         CHIP_ERROR Init(chip::Platform::PersistedStorage::Key aId, uint32_t aEpoch) { return CHIP_NO_ERROR; }
 
-        uint32_t GetValue() { return value; }
+        uint32_t GetValue() { return mValue; }
         CHIP_ERROR Advance()
         {
-            ++value;
+            ++mValue;
             return CHIP_NO_ERROR;
         }
 
     private:
-        uint32_t value;
+        uint32_t mValue;
     } persisted;
 #endif
 };
 
 class LocalSessionMessageCounter : public MessageCounter
 {
 public:
-    static constexpr uint32_t kInitialValue                 = 1;         ///< Used for initializing peer counter
+    static constexpr uint32_t kInitialSyncValue             = 0;         ///< Used for initializing peer counter
     static constexpr uint32_t kMessageCounterRandomInitMask = 0x0FFFFFF; ///< 28-bit mask
 
     /**
-     * Initialize a local message counter with random value between [0, 2^28-1]. This increases the difficulty of traffic analysis
-     * attacks by making it harder to determine how long a particular session has been open.
+     * Initialize a local message counter with random value between [1, 2^28]. This increases the difficulty of traffic analysis
+     * attacks by making it harder to determine how long a particular session has been open. The initial counter is always 1 or
+     * higher to guarantee first message is always greater than initial peer counter set to 0.
      */
-    LocalSessionMessageCounter() { value = Crypto::GetRandU32() & kMessageCounterRandomInitMask; }
+    LocalSessionMessageCounter() { mValue = (Crypto::GetRandU32() & kMessageCounterRandomInitMask) + 1; }
 
     Type GetType() override { return Session; }
-    uint32_t Value() override { return value; }
+    uint32_t Value() override { return mValue; }
     CHIP_ERROR Advance() override
     {
-        ++value;
+        ++mValue;
         return CHIP_NO_ERROR;
     }
 
 private:
-    uint32_t value;
+    uint32_t mValue;
 };
 
 } // namespace chip
diff --git a/src/transport/PairingSession.h b/src/transport/PairingSession.h
@@ -86,7 +86,7 @@ class DLL_EXPORT PairingSession
     virtual uint32_t GetPeerCounter()
     {
         // TODO(#6652): This is a stub implementation, should be replaced by the real one when CASE and PASE is completed
-        return LocalSessionMessageCounter::kInitialValue;
+        return LocalSessionMessageCounter::kInitialSyncValue;
     }
 
     /**