Reduce m2pack client hot-path overhead

src/PackLib/M2Pack.cpp

@@ -190,24 +190,19 @@ bool CM2Pack::ValidateManifest()
 bool CM2Pack::DecryptEntryPayload(const TM2PackEntry& entry, std::vector<uint8_t>& decrypted, CBufferPool* pPool)
 {
 	const uint64_t begin = sizeof(TM2PackHeader) + entry.data_offset;
-	const auto* ciphertext = reinterpret_cast<const uint8_t*>(m_file.data() + begin);
+	const auto* ciphertext = reinterpret_cast<const unsigned char*>(m_file.data() + begin);
-
-	std::vector<uint8_t> ciphertext_copy;
 	if (pPool)
 	{
-		ciphertext_copy = pPool->Acquire(entry.stored_size);
+		decrypted = pPool->Acquire(entry.stored_size);
 	}
-	ciphertext_copy.resize(entry.stored_size);
-	memcpy(ciphertext_copy.data(), ciphertext, entry.stored_size);
-
 	decrypted.resize(entry.stored_size);
 	unsigned long long written = 0;
 	if (crypto_aead_xchacha20poly1305_ietf_decrypt(
 		decrypted.data(),
 		&written,
 		nullptr,
-		ciphertext_copy.data(),
+		ciphertext,
-		ciphertext_copy.size(),
+		entry.stored_size,
 		reinterpret_cast<const unsigned char*>(entry.path.data()),
 		entry.path.size(),
 		entry.nonce.data(),
@@ -215,16 +210,12 @@ bool CM2Pack::DecryptEntryPayload(const TM2PackEntry& entry, std::vector<uint8_t
 	{
 		if (pPool)
 		{
-			pPool->Release(std::move(ciphertext_copy));
+			pPool->Release(std::move(decrypted));
 		}
 		return false;
 	}
 
 	decrypted.resize(static_cast<std::size_t>(written));
-	if (pPool)
-	{
-		pPool->Release(std::move(ciphertext_copy));
-	}
 	return true;
 }
 
@@ -253,6 +244,10 @@ bool CM2Pack::GetFileWithPool(const TM2PackEntry& entry, std::vector<uint8_t>& r
 		result.resize(entry.original_size);
 		ZSTD_DCtx* dctx = GetThreadLocalZstdContext();
 		size_t written = ZSTD_decompressDCtx(dctx, result.data(), result.size(), compressed.data(), compressed.size());
+		if (pPool)
+		{
+			pPool->Release(std::move(compressed));
+		}
 		if (ZSTD_isError(written) || written != entry.original_size)
 		{
 			TraceError("CM2Pack::GetFileWithPool: zstd failed for '%s'", entry.path.c_str());
@@ -262,10 +257,19 @@ bool CM2Pack::GetFileWithPool(const TM2PackEntry& entry, std::vector<uint8_t>& r
 	}
 
 	default:
+		if (pPool)
+		{
+			pPool->Release(std::move(compressed));
+		}
 		TraceError("CM2Pack::GetFileWithPool: unsupported compression %u for '%s'", entry.compression, entry.path.c_str());
 		return false;
 	}
 
+	if (!ShouldVerifyM2PackPlaintextHash())
+	{
+		return true;
+	}
+
 	std::array<uint8_t, M2PACK_HASH_SIZE> plain_hash {};
 	crypto_generichash(
 		plain_hash.data(),

src/PackLib/M2PackRuntimeKeyProvider.cpp

@@ -1,6 +1,7 @@
 #include "M2PackRuntimeKeyProvider.h"
 
 #include <algorithm>
+#include <cctype>
 #include <cstring>
 #include <string>
 
@@ -18,6 +19,7 @@ constexpr const char* M2PACK_ENV_MASTER_KEY = "M2PACK_MASTER_KEY_HEX";
 constexpr const char* M2PACK_ENV_PUBLIC_KEY = "M2PACK_SIGN_PUBKEY_HEX";
 constexpr const char* M2PACK_ENV_MAP_NAME = "M2PACK_KEY_MAP";
 constexpr const char* M2PACK_ENV_KEY_ID = "M2PACK_KEY_ID";
+constexpr const char* M2PACK_ENV_STRICT_HASH = "M2PACK_STRICT_HASH";
 
 #pragma pack(push, 1)
 struct M2PackSharedKeys
@@ -38,6 +40,7 @@ struct RuntimeKeyState
 	std::array<uint8_t, M2PACK_PUBLIC_KEY_SIZE> public_key {};
 	bool runtime_master_key = false;
 	bool runtime_public_key = false;
+	bool verify_plaintext_hash = false;
 	bool initialized = false;
 };
 
@@ -100,6 +103,31 @@ uint32_t ParseUInt32(const std::string& value)
 	}
 }
 
+bool ParseBoolFlag(std::string value, bool& out)
+{
+	value.erase(std::remove_if(value.begin(), value.end(), [](unsigned char ch) {
+		return std::isspace(ch) != 0;
+	}), value.end());
+
+	std::transform(value.begin(), value.end(), value.begin(), [](unsigned char ch) {
+		return static_cast<char>(std::tolower(ch));
+	});
+
+	if (value == "1" || value == "true" || value == "yes" || value == "on")
+	{
+		out = true;
+		return true;
+	}
+
+	if (value == "0" || value == "false" || value == "no" || value == "off")
+	{
+		out = false;
+		return true;
+	}
+
+	return false;
+}
+
 const std::array<uint8_t, M2PACK_PUBLIC_KEY_SIZE>* FindCompiledPublicKey(uint32_t keyId)
 {
 	for (std::size_t i = 0; i < M2PACK_SIGN_KEY_IDS.size(); ++i)
@@ -191,6 +219,19 @@ void ApplyCommandLineOption(const std::string& key, const std::string& value)
 		LoadFromSharedMapping(value);
 		return;
 	}
+
+	if (key == "--m2pack-strict-hash")
+	{
+		bool enabled = false;
+		if (ParseBoolFlag(value, enabled))
+		{
+			g_state.verify_plaintext_hash = enabled;
+		}
+		else
+		{
+			TraceError("Invalid value for --m2pack-strict-hash");
+		}
+	}
 }
 
 } // namespace
@@ -201,6 +242,9 @@ bool InitializeM2PackRuntimeKeyProvider(const char* commandLine)
 		return true;
 
 	g_state = RuntimeKeyState {};
+#ifdef _DEBUG
+	g_state.verify_plaintext_hash = true;
+#endif
 
 	const std::string mapName = GetEnvString(M2PACK_ENV_MAP_NAME);
 	if (!mapName.empty())
@@ -240,6 +284,16 @@ bool InitializeM2PackRuntimeKeyProvider(const char* commandLine)
 			TraceError("Invalid M2PACK_SIGN_PUBKEY_HEX value");
 	}
 
+	const std::string envStrictHash = GetEnvString(M2PACK_ENV_STRICT_HASH);
+	if (!envStrictHash.empty())
+	{
+		bool enabled = false;
+		if (ParseBoolFlag(envStrictHash, enabled))
+			g_state.verify_plaintext_hash = enabled;
+		else
+			TraceError("Invalid M2PACK_STRICT_HASH value");
+	}
+
 	int argc = 0;
 	PCHAR* argv = CommandLineToArgv(const_cast<PCHAR>(commandLine ? commandLine : ""), &argc);
 	if (argv)
@@ -247,6 +301,31 @@ bool InitializeM2PackRuntimeKeyProvider(const char* commandLine)
 		for (int i = 0; i < argc; ++i)
 		{
 			const std::string key = argv[i];
+			if (key == "--m2pack-strict-hash")
+			{
+				bool enabled = true;
+				if (i + 1 < argc)
+				{
+					const std::string next = argv[i + 1];
+					if (!next.starts_with("--"))
+					{
+						if (!ParseBoolFlag(next, enabled))
+						{
+							TraceError("Invalid value for --m2pack-strict-hash");
+						}
+						else
+						{
+							g_state.verify_plaintext_hash = enabled;
+						}
+						++i;
+						continue;
+					}
+				}
+
+				g_state.verify_plaintext_hash = enabled;
+				continue;
+			}
+
 			if ((key == "--m2pack-key-hex" || key == "--m2pack-pubkey-hex" || key == "--m2pack-key-map" || key == "--m2pack-key-id") && i + 1 < argc)
 			{
 				ApplyCommandLineOption(key, argv[i + 1]);
@@ -268,6 +347,11 @@ bool InitializeM2PackRuntimeKeyProvider(const char* commandLine)
 		Tracef("M2Pack runtime key provider: no runtime master key available; .m2p loading will be denied\n");
 	}
 
+	if (g_state.verify_plaintext_hash)
+	{
+		Tracef("M2Pack runtime key provider: plaintext hash verification enabled\n");
+	}
+
 	g_state.initialized = true;
 	return true;
 }
@@ -311,3 +395,8 @@ bool IsM2PackUsingRuntimePublicKey()
 {
 	return g_state.runtime_public_key;
 }
+
+bool ShouldVerifyM2PackPlaintextHash()
+{
+	return g_state.verify_plaintext_hash;
+}

src/PackLib/M2PackRuntimeKeyProvider.h

@@ -12,3 +12,4 @@ bool HasM2PackRuntimeMasterKey();
 bool HasM2PackRuntimeKeysForArchiveLoad(uint32_t keyId);
 bool IsM2PackUsingRuntimeMasterKey();
 bool IsM2PackUsingRuntimePublicKey();
+bool ShouldVerifyM2PackPlaintextHash();