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#include "CryptoEngine.h"
// #include "NodeDB.h"
#include "architecture.h"
#include <memory>
#if !(MESHTASTIC_EXCLUDE_PKI)
#include "HardwareRNG.h"
#include "NodeDB.h"
#include "aes-ccm.h"
#include "meshUtils.h"
#include <Crypto.h>
#include <Curve25519.h>
#include <RNG.h>
#include <SHA256.h>
#if !(MESHTASTIC_EXCLUDE_PKI_KEYGEN)
#if !defined(ARCH_STM32WL)
#define CryptRNG RNG
#endif
/**
* Create a public/private key pair with Curve25519.
*
* @param pubKey The destination for the public key.
* @param privKey The destination for the private key.
*/
void CryptoEngine::generateKeyPair(uint8_t *pubKey, uint8_t *privKey)
{
// Mix in any randomness we can, to make key generation stronger.
CryptRNG.begin(optstr(APP_VERSION));
uint8_t hardwareEntropy[64] = {0};
if (HardwareRNG::fill(hardwareEntropy, sizeof(hardwareEntropy), true)) {
CryptRNG.stir(hardwareEntropy, sizeof(hardwareEntropy));
} else {
LOG_WARN("Hardware entropy unavailable, falling back to software RNG");
}
memset(hardwareEntropy, 0, sizeof(hardwareEntropy));
if (myNodeInfo.device_id.size == 16) {
CryptRNG.stir(myNodeInfo.device_id.bytes, myNodeInfo.device_id.size);
}
auto noise = random();
CryptRNG.stir((uint8_t *)&noise, sizeof(noise));
LOG_DEBUG("Generate Curve25519 keypair");
Curve25519::dh1(public_key, private_key);
memcpy(pubKey, public_key, sizeof(public_key));
memcpy(privKey, private_key, sizeof(private_key));
}
/**
* regenerate a public key with Curve25519.
*
* @param pubKey The destination for the public key.
* @param privKey The source for the private key.
*/
bool CryptoEngine::regeneratePublicKey(uint8_t *pubKey, uint8_t *privKey)
{
if (!memfll(privKey, 0, sizeof(private_key))) {
Curve25519::eval(pubKey, privKey, 0);
if (Curve25519::isWeakPoint(pubKey)) {
LOG_ERROR("PKI key generation failed. Specified private key results in a weak");
memset(pubKey, 0, 32);
return false;
}
memcpy(private_key, privKey, sizeof(private_key));
memcpy(public_key, pubKey, sizeof(public_key));
} else {
LOG_WARN("X25519 key generation failed due to blank private key");
return false;
}
return true;
}
#endif
/**
* Encrypt a packet's payload using a key generated with Curve25519 and SHA256
* for a specific node.
*
* @param toNode The MeshPacket `to` field.
* @param fromNode The MeshPacket `from` field.
* @param remotePublic The remote node's Curve25519 public key.
* @param packetId The MeshPacket `id` field.
* @param numBytes Number of bytes of plaintext in the bytes buffer.
* @param bytes Buffer containing plaintext input.
* @param bytesOut Output buffer to be populated with encrypted ciphertext.
*/
bool CryptoEngine::encryptCurve25519(uint32_t toNode, uint32_t fromNode, meshtastic_UserLite_public_key_t remotePublic,
uint64_t packetNum, size_t numBytes, const uint8_t *bytes, uint8_t *bytesOut)
{
uint8_t *auth;
long extraNonceTmp = random();
auth = bytesOut + numBytes;
memcpy((uint8_t *)(auth + 8), &extraNonceTmp,
sizeof(uint32_t)); // do not use dereference on potential non aligned pointers : *extraNonce = extraNonceTmp;
LOG_DEBUG("Random nonce value: %d", extraNonceTmp);
if (remotePublic.size == 0) {
LOG_DEBUG("Node %d or their public_key not found", toNode);
return false;
}
if (!setDHPublicKey(remotePublic.bytes)) {
return false;
}
hash(shared_key, 32);
initNonce(fromNode, packetNum, extraNonceTmp);
// Calculate the shared secret with the destination node and encrypt
printBytes("Attempt encrypt with nonce: ", nonce, 13);
printBytes("Attempt encrypt with shared_key starting with: ", shared_key, 8);
aes_ccm_ae(shared_key, 32, nonce, 8, bytes, numBytes, nullptr, 0, bytesOut,
auth); // this can write up to 15 bytes longer than numbytes past bytesOut
memcpy((uint8_t *)(auth + 8), &extraNonceTmp,
sizeof(uint32_t)); // do not use dereference on potential non aligned pointers : *extraNonce = extraNonceTmp;
return true;
}
/**
* Decrypt a packet's payload using a key generated with Curve25519 and SHA256
* for a specific node.
*
* @param fromNode The MeshPacket `from` field.
* @param remotePublic The remote node's Curve25519 public key.
* @param packetId The MeshPacket `id` field.
* @param numBytes Number of bytes of ciphertext in the bytes buffer.
* @param bytes Buffer containing ciphertext input.
* @param bytesOut Output buffer to be populated with decrypted plaintext.
*/
bool CryptoEngine::decryptCurve25519(uint32_t fromNode, meshtastic_UserLite_public_key_t remotePublic, uint64_t packetNum,
size_t numBytes, const uint8_t *bytes, uint8_t *bytesOut)
{
const uint8_t *auth = bytes + numBytes - 12; // set to last 8 bytes of text?
uint32_t extraNonce; // pointer was not really used
memcpy(&extraNonce, auth + 8,
sizeof(uint32_t)); // do not use dereference on potential non aligned pointers : (uint32_t *)(auth + 8);
LOG_INFO("Random nonce value: %d", extraNonce);
if (remotePublic.size == 0) {
LOG_DEBUG("Node or its public key not found in database");
return false;
}
// Calculate the shared secret with the sending node and decrypt
if (!setDHPublicKey(remotePublic.bytes)) {
return false;
}
hash(shared_key, 32);
initNonce(fromNode, packetNum, extraNonce);
printBytes("Attempt decrypt with nonce: ", nonce, 13);
printBytes("Attempt decrypt with shared_key starting with: ", shared_key, 8);
return aes_ccm_ad(shared_key, 32, nonce, 8, bytes, numBytes - 12, nullptr, 0, auth, bytesOut);
}
void CryptoEngine::setDHPrivateKey(uint8_t *_private_key)
{
memcpy(private_key, _private_key, 32);
}
/**
* Hash arbitrary data using SHA256.
*
* @param bytes
* @param numBytes
*/
void CryptoEngine::hash(uint8_t *bytes, size_t numBytes)
{
SHA256 hash;
size_t posn;
uint8_t size = numBytes;
uint8_t inc = 16;
hash.reset();
for (posn = 0; posn < size; posn += inc) {
size_t len = size - posn;
if (len > inc)
len = inc;
hash.update(bytes + posn, len);
}
hash.finalize(bytes, 32);
}
void CryptoEngine::aesSetKey(const uint8_t *key_bytes, size_t key_len)
{
aes = nullptr;
if (key_len != 0) {
aes = std::unique_ptr<AESSmall256>(new AESSmall256());
aes->setKey(key_bytes, key_len);
}
}
void CryptoEngine::aesEncrypt(uint8_t *in, uint8_t *out)
{
aes->encryptBlock(out, in);
}
bool CryptoEngine::setDHPublicKey(uint8_t *pubKey)
{
uint8_t local_priv[32];
memcpy(shared_key, pubKey, 32);
memcpy(local_priv, private_key, 32);
// Calculate the shared secret with the specified node's public key and our private key
// This includes an internal weak key check, which among other things looks for an all 0 public key and shared key.
if (!Curve25519::dh2(shared_key, local_priv)) {
LOG_WARN("Curve25519DH step 2 failed!");
return false;
}
return true;
}
#endif
concurrency::Lock *cryptLock;
void CryptoEngine::setKey(const CryptoKey &k)
{
LOG_DEBUG("Use AES%d key!", k.length * 8);
key = k;
}
/**
* Encrypt a packet
*
* @param bytes is updated in place
*/
void CryptoEngine::encryptPacket(uint32_t fromNode, uint64_t packetId, size_t numBytes, uint8_t *bytes)
{
if (key.length > 0) {
initNonce(fromNode, packetId);
if (numBytes <= MAX_BLOCKSIZE) {
encryptAESCtr(key, nonce, numBytes, bytes);
} else {
LOG_ERROR("Packet too large for crypto engine: %d. noop encryption!", numBytes);
}
}
}
void CryptoEngine::decrypt(uint32_t fromNode, uint64_t packetId, size_t numBytes, uint8_t *bytes)
{
// For CTR, the implementation is the same
encryptPacket(fromNode, packetId, numBytes, bytes);
}
// Generic implementation of AES-CTR encryption.
void CryptoEngine::encryptAESCtr(CryptoKey _key, uint8_t *_nonce, size_t numBytes, uint8_t *bytes)
{
std::unique_ptr<CTRCommon> ctr;
if (_key.length == 16)
ctr = std::unique_ptr<CTRCommon>(new CTR<AES128>());
else
ctr = std::unique_ptr<CTRCommon>(new CTR<AES256>());
ctr->setKey(_key.bytes, _key.length);
static uint8_t scratch[MAX_BLOCKSIZE];
memcpy(scratch, bytes, numBytes);
memset(scratch + numBytes, 0,
sizeof(scratch) - numBytes); // Fill rest of buffer with zero (in case cypher looks at it)
ctr->setIV(_nonce, 16);
ctr->setCounterSize(4);
ctr->encrypt(bytes, scratch, numBytes);
}
/**
* Init our 128 bit nonce for a new packet
*/
void CryptoEngine::initNonce(uint32_t fromNode, uint64_t packetId, uint32_t extraNonce)
{
memset(nonce, 0, sizeof(nonce));
// use memcpy to avoid breaking strict-aliasing
memcpy(nonce, &packetId, sizeof(uint64_t));
memcpy(nonce + sizeof(uint64_t), &fromNode, sizeof(uint32_t));
if (extraNonce)
memcpy(nonce + sizeof(uint32_t), &extraNonce, sizeof(uint32_t));
}
#ifndef HAS_CUSTOM_CRYPTO_ENGINE
CryptoEngine *crypto = new CryptoEngine;
#endif