tests: cover room packet matching and size-checked ZSTD decompression

Assisted-by: Claude Opus 5.5 (investigation and implementation)

1 files changed, 59 insertions, 0 deletions

diff --git a/src/tests/common/zstd_compression.cpp b/src/tests/common/zstd_compression.cpp
new file mode 100644
index 0000000000..6996f2e1ac
--- /dev/null
+++ b/src/tests/common/zstd_compression.cpp
@@ -0,0 +1,59 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include <array>
+#include <vector>
+
+#include <catch2/catch_test_macros.hpp>
+
+#include "common/common_types.h"
+#include "common/zstd_compression.h"
+
+namespace {
+
+std::vector<u8> Compress(const std::vector<u8>& data) {
+    return Common::Compression::CompressDataZSTDDefault(data.data(), data.size());
+}
+
+} // namespace
+
+TEST_CASE("ZSTD frames within the size limit decompress", "[common][zstd]") {
+    const std::vector<u8> data(100, 0x5a);
+    const auto compressed = Compress(data);
+
+    const auto result = Common::Compression::TryDecompressDataZSTD(compressed, data.size());
+    REQUIRE(result.has_value());
+    REQUIRE(*result == data);
+    REQUIRE(Common::Compression::DecompressDataZSTD(compressed) == data);
+
+    const auto empty = Common::Compression::TryDecompressDataZSTD(Compress({}), 0);
+    REQUIRE(empty.has_value());
+    REQUIRE(empty->empty());
+}
+
+TEST_CASE("ZSTD frames over the size limit are rejected", "[common][zstd]") {
+    const std::vector<u8> data(100, 0x5a);
+    const auto compressed = Compress(data);
+    REQUIRE_FALSE(Common::Compression::TryDecompressDataZSTD(compressed, data.size() - 1));
+}
+
+TEST_CASE("Invalid ZSTD frames are rejected without throwing", "[common][zstd]") {
+    const std::array<u8, 1> one_byte{0x01};
+    const std::array<u8, 5> bad_magic{0x01, 0x02, 0x03, 0x04, 0x05};
+    REQUIRE_FALSE(Common::Compression::TryDecompressDataZSTD(one_byte, 0x10000));
+    REQUIRE_FALSE(Common::Compression::TryDecompressDataZSTD(bad_magic, 0x10000));
+    REQUIRE(Common::Compression::DecompressDataZSTD(one_byte).empty());
+
+    // The header declares the size, but the data after it is cut off
+    std::vector<u8> truncated = Compress(std::vector<u8>(100, 0x5a));
+    truncated.pop_back();
+    REQUIRE_FALSE(Common::Compression::TryDecompressDataZSTD(truncated, 0x10000));
+}
+
+TEST_CASE("ZSTD frames without a declared size are rejected", "[common][zstd]") {
+    // Magic number, a frame header without the content size, then one raw 3-byte last block
+    const std::array<u8, 12> frame{0x28, 0xb5, 0x2f, 0xfd, 0x00, 0x00,
+                                   0x19, 0x00, 0x00, 'a',  'b',  'c'};
+    REQUIRE_FALSE(Common::Compression::TryDecompressDataZSTD(frame, 0x10000));
+    REQUIRE(Common::Compression::DecompressDataZSTD(frame).empty());
+}