test(vm): add boundary and edge case tests for eip-7823 modexp limit

- baseLen == 1024 boundary value should succeed
- baseLen == 1025 just over limit should fail
- oversized expLen only should fail
- oversized modLen only should fail
- all limits exceeded with osaka disabled should succeed

Author: ouy95917

framework/src/test/java/org/tron/common/runtime/vm/AllowTvmOsakaTest.java

@@ -12,29 +12,66 @@
 @Slf4j
 public class AllowTvmOsakaTest extends VMTestBase {
 
+  private static final PrecompiledContracts.PrecompiledContract modExp =
+      new PrecompiledContracts.ModExp();
+
+  private static byte[] toLenBytes(int value) {
+    byte[] b = new byte[32];
+    b[28] = (byte) ((value >> 24) & 0xFF);
+    b[29] = (byte) ((value >> 16) & 0xFF);
+    b[30] = (byte) ((value >> 8) & 0xFF);
+    b[31] = (byte) (value & 0xFF);
+    return b;
+  }
+
   @Test
   public void testEIP7823() {
     ConfigLoader.disable = true;
     VMConfig.initAllowTvmOsaka(1);
 
     try {
-      byte[] baseLen = new byte[32];
-      byte[] expLen = new byte[32];
-      byte[] modLen = new byte[32];
-
-      PrecompiledContracts.PrecompiledContract modExp = new PrecompiledContracts.ModExp();
+      // all-zero lengths: should succeed
+      Pair<Boolean, byte[]> result = modExp.execute(
+          ByteUtil.merge(toLenBytes(0), toLenBytes(0), toLenBytes(0)));
+      Assert.assertTrue(result.getLeft());
 
-      // Valid lens: all zeros (0 <= 1024)
-      Pair<Boolean, byte[]> result = modExp.execute(ByteUtil.merge(baseLen, expLen, modLen));
+      // baseLen == 1024: boundary, should succeed
+      result = modExp.execute(
+          ByteUtil.merge(toLenBytes(1024), toLenBytes(0), toLenBytes(0)));
       Assert.assertTrue(result.getLeft());
 
-      // Invalid lens: baseLen = 0x01000000... = 16777216 > 1024
-      baseLen[0] = 0x01;
-      result = modExp.execute(ByteUtil.merge(baseLen, expLen, modLen));
+      // baseLen == 1025: just over the limit, should fail
+      result = modExp.execute(
+          ByteUtil.merge(toLenBytes(1025), toLenBytes(0), toLenBytes(0)));
+      Assert.assertFalse(result.getLeft());
+
+      // oversized expLen only: should fail
+      result = modExp.execute(
+          ByteUtil.merge(toLenBytes(0), toLenBytes(1025), toLenBytes(0)));
+      Assert.assertFalse(result.getLeft());
+
+      // oversized modLen only: should fail
+      result = modExp.execute(
+          ByteUtil.merge(toLenBytes(0), toLenBytes(0), toLenBytes(1025)));
       Assert.assertFalse(result.getLeft());
     } finally {
       VMConfig.initAllowTvmOsaka(0);
       ConfigLoader.disable = false;
     }
   }
+
+  @Test
+  public void testEIP7823DisabledShouldPass() {
+    ConfigLoader.disable = true;
+    VMConfig.initAllowTvmOsaka(0);
+
+    try {
+      // all limits exceeded while osaka is disabled: should succeed (no restriction)
+      Pair<Boolean, byte[]> result = modExp.execute(
+          ByteUtil.merge(toLenBytes(2048), toLenBytes(2048), toLenBytes(2048)));
+      Assert.assertTrue(result.getLeft());
+    } finally {
+      ConfigLoader.disable = false;
+    }
+  }
 }