// Copyright 2017 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#include <cstring>
#include <cryptopp/aes.h>
#include <cryptopp/ccm.h>
#include <cryptopp/filters.h>
#include <cryptopp/md5.h>
#include <cryptopp/modes.h>
#include "core/hle/service/nwm/nwm_uds.h"
#include "core/hle/service/nwm/uds_data.h"
#include "core/hw/aes/key.h"
namespace Service {
namespace NWM {
using MacAddress = std::array<u8, 6>;
/*
* Generates a SNAP-enabled 802.2 LLC header for the specified protocol.
* @returns a buffer with the bytes of the generated header.
*/
static std::vector<u8> GenerateLLCHeader(EtherType protocol) {
LLCHeader header{};
header.protocol = static_cast<u16>(protocol);
std::vector<u8> buffer(sizeof(header));
memcpy(buffer.data(), &header, sizeof(header));
return buffer;
}
/*
* Generates a Nintendo UDS SecureData header with the specified parameters.
* @returns a buffer with the bytes of the generated header.
*/
static std::vector<u8> GenerateSecureDataHeader(u16 data_size, u8 channel, u16 dest_node_id,
u16 src_node_id, u16 sequence_number) {
SecureDataHeader header{};
header.protocol_size = data_size + sizeof(SecureDataHeader);
// Note: This size includes everything except the first 4 bytes of the structure,
// reinforcing the hypotheses that the first 4 bytes are actually the header of
// another container protocol.
header.securedata_size = data_size + sizeof(SecureDataHeader) - 4;
// Frames sent by the emulated application are never UDS management frames
header.is_management = 0;
header.data_channel = channel;
header.sequence_number = sequence_number;
header.dest_node_id = dest_node_id;
header.src_node_id = src_node_id;
std::vector<u8> buffer(sizeof(header));
memcpy(buffer.data(), &header, sizeof(header));
return buffer;
}
/*
* Calculates the CTR used for the AES-CTR process that calculates
* the CCMP crypto key for data frames.
* @returns The CTR used for data frames crypto key generation.
*/
static std::array<u8, CryptoPP::MD5::DIGESTSIZE> GetDataCryptoCTR(const NetworkInfo& network_info) {
DataFrameCryptoCTR data{};
data.host_mac = network_info.host_mac_address;
data.wlan_comm_id = network_info.wlan_comm_id;
data.id = network_info.id;
data.network_id = network_info.network_id;
std::array<u8, CryptoPP::MD5::DIGESTSIZE> hash;
CryptoPP::MD5().CalculateDigest(hash.data(), reinterpret_cast<u8*>(&data), sizeof(data));
return hash;
}
/*
* Generates the key used for encrypting the 802.11 data frames generated by UDS.
* @returns The key used for data frames crypto.
*/
static std::array<u8, CryptoPP::AES::BLOCKSIZE> GenerateDataCCMPKey(
const std::vector<u8>& passphrase, const NetworkInfo& network_info) {
// Calculate the MD5 hash of the input passphrase.
std::array<u8, CryptoPP::MD5::DIGESTSIZE> passphrase_hash;
CryptoPP::MD5().CalculateDigest(passphrase_hash.data(), passphrase.data(), passphrase.size());
std::array<u8, CryptoPP::AES::BLOCKSIZE> ccmp_key;
// The CCMP key is the result of encrypting the MD5 hash of the passphrase with AES-CTR using
// keyslot 0x2D.
using CryptoPP::AES;
std::array<u8, CryptoPP::MD5::DIGESTSIZE> counter = GetDataCryptoCTR(network_info);
std::array<u8, AES::BLOCKSIZE> key = HW::AES::GetNormalKey(HW::AES::KeySlotID::UDSDataKey);
CryptoPP::CTR_Mode<AES>::Encryption aes;
aes.SetKeyWithIV(key.data(), AES::BLOCKSIZE, counter.data());
aes.ProcessData(ccmp_key.data(), passphrase_hash.data(), passphrase_hash.size());
return ccmp_key;
}
/*
* Generates the Additional Authenticated Data (AAD) for an UDS 802.11 encrypted data frame.
* @returns a buffer with the bytes of the AAD.
*/
static std::vector<u8> GenerateCCMPAAD(const MacAddress& sender, const MacAddress& receiver,
const MacAddress& bssid, u16 frame_control) {
// Reference: IEEE 802.11-2007
// 8.3.3.3.2 Construct AAD (22-30 bytes)
// The AAD is constructed from the MPDU header. The AAD does not include the header Duration
// field, because the Duration field value can change due to normal IEEE 802.11 operation (e.g.,
// a rate change during retransmission). For similar reasons, several subfields in the Frame
// Control field are masked to 0.
struct {
u16_be FC; // MPDU Frame Control field
MacAddress A1;
MacAddress A2;
MacAddress A3;
u16_be SC; // MPDU Sequence Control field
} aad_struct{};
constexpr u16 AADFrameControlMask = 0x8FC7;
aad_struct.FC = frame_control & AADFrameControlMask;
aad_struct.SC = 0;
bool to_ds = (frame_control & (1 << 0)) != 0;
bool from_ds = (frame_control & (1 << 1)) != 0;
// In the 802.11 standard, ToDS = 1 and FromDS = 1 is a valid configuration,
// however, the 3DS doesn't seem to transmit frames with such combination.
ASSERT_MSG(to_ds != from_ds, "Invalid combination");
// The meaning of the address fields depends on the ToDS and FromDS fields.
if (from_ds) {
aad_struct.A1 = receiver;
aad_struct.A2 = bssid;
aad_struct.A3 = sender;
}
if (to_ds) {
aad_struct.A1 = bssid;
aad_struct.A2 = sender;
aad_struct.A3 = receiver;
}
std::vector<u8> aad(sizeof(aad_struct));
std::memcpy(aad.data(), &aad_struct, sizeof(aad_struct));
return aad;
}
/*
* Decrypts the payload of an encrypted 802.11 data frame using the specified key.
* @returns The decrypted payload.
*/
static std::vector<u8> DecryptDataFrame(const std::vector<u8>& encrypted_payload,
const std::array<u8, CryptoPP::AES::BLOCKSIZE>& ccmp_key,
const MacAddress& sender, const MacAddress& receiver,
const MacAddress& bssid, u16 sequence_number,
u16 frame_control) {
// Reference: IEEE 802.11-2007
std::vector<u8> aad = GenerateCCMPAAD(sender, receiver, bssid, frame_control);
std::vector<u8> packet_number{0,
0,
0,
0,
static_cast<u8>((sequence_number >> 8) & 0xFF),
static_cast<u8>(sequence_number & 0xFF)};
// 8.3.3.3.3 Construct CCM nonce (13 bytes)
std::vector<u8> nonce;
nonce.push_back(0); // priority
nonce.insert(nonce.end(), sender.begin(), sender.end()); // Address 2
nonce.insert(nonce.end(), packet_number.begin(), packet_number.end()); // PN
try {
CryptoPP::CCM<CryptoPP::AES, 8>::Decryption d;
d.SetKeyWithIV(ccmp_key.data(), ccmp_key.size(), nonce.data(), nonce.size());
d.SpecifyDataLengths(aad.size(), encrypted_payload.size() - 8, 0);
CryptoPP::AuthenticatedDecryptionFilter df(
d, nullptr, CryptoPP::AuthenticatedDecryptionFilter::MAC_AT_END |
CryptoPP::AuthenticatedDecryptionFilter::THROW_EXCEPTION);
// put aad
df.ChannelPut(CryptoPP::AAD_CHANNEL, aad.data(), aad.size());
// put cipher with mac
df.ChannelPut(CryptoPP::DEFAULT_CHANNEL, encrypted_payload.data(),
encrypted_payload.size() - 8);
df.ChannelPut(CryptoPP::DEFAULT_CHANNEL,
encrypted_payload.data() + encrypted_payload.size() - 8, 8);
df.ChannelMessageEnd(CryptoPP::AAD_CHANNEL);
df.ChannelMessageEnd(CryptoPP::DEFAULT_CHANNEL);
df.SetRetrievalChannel(CryptoPP::DEFAULT_CHANNEL);
int size = df.MaxRetrievable();
std::vector<u8> pdata(size);
df.Get(pdata.data(), size);
return pdata;
} catch (CryptoPP::Exception&) {
LOG_ERROR(Service_NWM, "failed to decrypt");
}
return {};
}
/*
* Encrypts the payload of an 802.11 data frame using the specified key.
* @returns The encrypted payload.
*/
static std::vector<u8> EncryptDataFrame(const std::vector<u8>& payload,
const std::array<u8, CryptoPP::AES::BLOCKSIZE>& ccmp_key,
const MacAddress& sender, const MacAddress& receiver,
const MacAddress& bssid, u16 sequence_number,
u16 frame_control) {
// Reference: IEEE 802.11-2007
std::vector<u8> aad = GenerateCCMPAAD(sender, receiver, bssid, frame_control);
std::vector<u8> packet_number{0,
0,
0,
0,
static_cast<u8>((sequence_number >> 8) & 0xFF),
static_cast<u8>(sequence_number & 0xFF)};
// 8.3.3.3.3 Construct CCM nonce (13 bytes)
std::vector<u8> nonce;
nonce.push_back(0); // priority
nonce.insert(nonce.end(), sender.begin(), sender.end()); // Address 2
nonce.insert(nonce.end(), packet_number.begin(), packet_number.end()); // PN
try {
CryptoPP::CCM<CryptoPP::AES, 8>::Encryption d;
d.SetKeyWithIV(ccmp_key.data(), ccmp_key.size(), nonce.data(), nonce.size());
d.SpecifyDataLengths(aad.size(), payload.size(), 0);
CryptoPP::AuthenticatedEncryptionFilter df(d);
// put aad
df.ChannelPut(CryptoPP::AAD_CHANNEL, aad.data(), aad.size());
df.ChannelMessageEnd(CryptoPP::AAD_CHANNEL);
// put plaintext
df.ChannelPut(CryptoPP::DEFAULT_CHANNEL, payload.data(), payload.size());
df.ChannelMessageEnd(CryptoPP::DEFAULT_CHANNEL);
df.SetRetrievalChannel(CryptoPP::DEFAULT_CHANNEL);
int size = df.MaxRetrievable();
std::vector<u8> cipher(size);
df.Get(cipher.data(), size);
return cipher;
} catch (CryptoPP::Exception&) {
LOG_ERROR(Service_NWM, "failed to encrypt");
}
return {};
}
std::vector<u8> GenerateDataPayload(const std::vector<u8>& data, u8 channel, u16 dest_node,
u16 src_node, u16 sequence_number) {
std::vector<u8> buffer = GenerateLLCHeader(EtherType::SecureData);
std::vector<u8> securedata_header =
GenerateSecureDataHeader(data.size(), channel, dest_node, src_node, sequence_number);
buffer.insert(buffer.end(), securedata_header.begin(), securedata_header.end());
buffer.insert(buffer.end(), data.begin(), data.end());
return buffer;
}
} // namespace NWM
} // namespace Service
