silkpre: be defensive

ethereum · Jul 28, 2023 · 0fdcdfd · 0fdcdfd
1 parent 1717844
commit 0fdcdfd
Showing 1 changed file with 8 additions and 4 deletions.
diff --git a/test/state/precompiles_silkpre.cpp b/test/state/precompiles_silkpre.cpp
@@ -14,14 +14,18 @@ namespace
 ExecutionResult execute(const uint8_t* input, size_t input_size, uint8_t* output_buf,
     [[maybe_unused]] size_t max_output_size, PrecompileId id) noexcept
 {
-    const auto index = static_cast<size_t>(id) - 1;
+    const auto index = stdx::to_underlying(id) - 1;
     const auto [output, output_size] = kSilkpreContracts[index].run(input, input_size);
     if (output == nullptr)
         return {EVMC_PRECOMPILE_FAILURE, 0};
+
+    // Check if max_output_size computed by analysis match the computed result.
     assert(output_size <= max_output_size);
-    std::memcpy(output_buf, output, output_size);
-    std::free(output);
-    return {EVMC_SUCCESS, output_size};
+
+    auto trimmed_output_size = std::min(output_size, max_output_size);
+    std::memcpy(output_buf, output, trimmed_output_size);
+    std::free(output);  // Free output allocation (required by silkpre API).
+    return {EVMC_SUCCESS, trimmed_output_size};
 }
 }  // namespace