Merge pull request #63 from VibhorGautam/fix/memory-read-fail-closed

fix(policy): fail-closed memory reads when HMAC proof is absent

Author: tharindupr

policies/tests/memory_test.rego

@@ -35,6 +35,17 @@ test_read_hmac_valid_allow if {
 	result == "ALLOW"
 }
 
+test_read_missing_integrity_block if {
+	result := memory.decision with input as {
+		"memory_op": "read",
+		"score": 0.0,
+		"signals": [],
+		"provenance": "agent", "session_id": "m-009", "hook_type": "on_memory",
+		"payload_size_bytes": 100,
+	}
+	result == "BLOCK"
+}
+
 # --- Detection: write-time content scan ---
 
 # A poisoned write flagged by the content scanner is stripped (SANITISE).

policies/v1/memory.rego

@@ -26,7 +26,7 @@ default decision := "ALLOW"
 
 decision := "BLOCK" if {
     input.memory_op == "read"
-    input.integrity.hmac_valid == false
+    not input.integrity.hmac_valid == true
 }
 
 # ---------------------------------------------------------------------

policies/v1/memory_test.rego

@@ -35,6 +35,29 @@ test_read_invalid_hmac_block if {
     result == "BLOCK"
 }
 
+test_read_missing_hmac_block if {
+    result := memory.decision with input as {
+        "memory_op": "read",
+        "score": 0.0,
+        "signals": [],
+        "provenance": "agent", "session_id": "s1", "hook_type": "on_memory",
+        "payload_size_bytes": 100,
+    }
+    result == "BLOCK"
+}
+
+test_read_null_hmac_block if {
+    result := memory.decision with input as {
+        "memory_op": "read",
+        "score": 0.0,
+        "signals": [],
+        "provenance": "agent", "session_id": "s1", "hook_type": "on_memory",
+        "integrity": {"hmac_valid": null},
+        "payload_size_bytes": 100,
+    }
+    result == "BLOCK"
+}
+
 # =====================================================================
 # Integrity — write-time HMAC stamp
 # =====================================================================