1 files changed, 106 insertions, 0 deletions
diff --git a/src/core/hle/service/nfc/common/amiibo_crypto.h b/src/core/hle/service/nfc/common/amiibo_crypto.h
new file mode 100644
index 000000000..bf3044ed9
--- /dev/null
+++ b/src/core/hle/service/nfc/common/amiibo_crypto.h
@@ -0,0 +1,106 @@
+// SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <array>
+
+#include "core/hle/service/nfp/nfp_types.h"
+
+struct mbedtls_md_context_t;
+
+namespace Service::NFP::AmiiboCrypto {
+// Byte locations in Service::NFP::NTAG215File
+constexpr std::size_t HMAC_DATA_START = 0x8;
+constexpr std::size_t SETTINGS_START = 0x2c;
+constexpr std::size_t WRITE_COUNTER_START = 0x29;
+constexpr std::size_t HMAC_TAG_START = 0x1B4;
+constexpr std::size_t UUID_START = 0x1D4;
+constexpr std::size_t DYNAMIC_LOCK_START = 0x208;
+
+using HmacKey = std::array<u8, 0x10>;
+using DrgbOutput = std::array<u8, 0x20>;
+
+struct HashSeed {
+    u16_be magic;
+    std::array<u8, 0xE> padding;
+    NFC::UniqueSerialNumber uid_1;
+    u8 nintendo_id_1;
+    NFC::UniqueSerialNumber uid_2;
+    u8 nintendo_id_2;
+    std::array<u8, 0x20> keygen_salt;
+};
+static_assert(sizeof(HashSeed) == 0x40, "HashSeed is an invalid size");
+
+struct InternalKey {
+    HmacKey hmac_key;
+    std::array<char, 0xE> type_string;
+    u8 reserved;
+    u8 magic_length;
+    std::array<u8, 0x10> magic_bytes;
+    std::array<u8, 0x20> xor_pad;
+};
+static_assert(sizeof(InternalKey) == 0x50, "InternalKey is an invalid size");
+static_assert(std::is_trivially_copyable_v<InternalKey>, "InternalKey must be trivially copyable.");
+
+struct CryptoCtx {
+    std::array<char, 480> buffer;
+    bool used;
+    std::size_t buffer_size;
+    s16 counter;
+};
+
+struct DerivedKeys {
+    std::array<u8, 0x10> aes_key;
+    std::array<u8, 0x10> aes_iv;
+    std::array<u8, 0x10> hmac_key;
+};
+static_assert(sizeof(DerivedKeys) == 0x30, "DerivedKeys is an invalid size");
+
+/// Validates that the amiibo file is not corrupted
+bool IsAmiiboValid(const EncryptedNTAG215File& ntag_file);
+
+/// Validates that the amiibo file is not corrupted
+bool IsAmiiboValid(const NTAG215File& ntag_file);
+
+/// Converts from encrypted file format to encoded file format
+NTAG215File NfcDataToEncodedData(const EncryptedNTAG215File& nfc_data);
+
+/// Converts from encoded file format to encrypted file format
+EncryptedNTAG215File EncodedDataToNfcData(const NTAG215File& encoded_data);
+
+/// Returns password needed to allow write access to protected memory
+u32 GetTagPassword(const TagUuid& uuid);
+
+// Generates Seed needed for key derivation
+HashSeed GetSeed(const NTAG215File& data);
+
+// Middle step on the generation of derived keys
+std::vector<u8> GenerateInternalKey(const InternalKey& key, const HashSeed& seed);
+
+// Initializes mbedtls context
+void CryptoInit(CryptoCtx& ctx, mbedtls_md_context_t& hmac_ctx, const HmacKey& hmac_key,
+                const std::vector<u8>& seed);
+
+// Feeds data to mbedtls context to generate the derived key
+void CryptoStep(CryptoCtx& ctx, mbedtls_md_context_t& hmac_ctx, DrgbOutput& output);
+
+// Generates the derived key from amiibo data
+DerivedKeys GenerateKey(const InternalKey& key, const NTAG215File& data);
+
+// Encodes or decodes amiibo data
+void Cipher(const DerivedKeys& keys, const NTAG215File& in_data, NTAG215File& out_data);
+
+/// Loads both amiibo keys from key_retail.bin
+bool LoadKeys(InternalKey& locked_secret, InternalKey& unfixed_info);
+
+/// Returns true if key_retail.bin exist
+bool IsKeyAvailable();
+
+/// Decodes encrypted amiibo data returns true if output is valid
+bool DecodeAmiibo(const EncryptedNTAG215File& encrypted_tag_data, NTAG215File& tag_data);
+
+/// Encodes plain amiibo data returns true if output is valid
+bool EncodeAmiibo(const NTAG215File& tag_data, EncryptedNTAG215File& encrypted_tag_data);
+
+} // namespace Service::NFP::AmiiboCrypto