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7221fc4d4b
* Delete unused code CryptoEngine::clearKeys() is not used in the code base, therefore this cleanup removes the code. It might give casual reviewers the impression, that keys are wiped. Since the code uses memset() which might be optimized away by the compiler, using the code might not even cause the memory to be wiped. * Update CryptoEngine.cpp Fix stray newline, this is the only thing that I can come up with that might confuse the linter. --------- Co-authored-by: Jason P <applewiz@mac.com>
267 lines
8.6 KiB
C++
267 lines
8.6 KiB
C++
#include "CryptoEngine.h"
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// #include "NodeDB.h"
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#include "architecture.h"
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#if !(MESHTASTIC_EXCLUDE_PKI)
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#include "NodeDB.h"
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#include "aes-ccm.h"
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#include "meshUtils.h"
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#include <Crypto.h>
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#include <Curve25519.h>
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#include <RNG.h>
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#include <SHA256.h>
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#if !(MESHTASTIC_EXCLUDE_PKI_KEYGEN)
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#if !defined(ARCH_STM32WL)
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#define CryptRNG RNG
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#endif
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/**
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* Create a public/private key pair with Curve25519.
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*
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* @param pubKey The destination for the public key.
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* @param privKey The destination for the private key.
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*/
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void CryptoEngine::generateKeyPair(uint8_t *pubKey, uint8_t *privKey)
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{
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// Mix in any randomness we can, to make key generation stronger.
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CryptRNG.begin(optstr(APP_VERSION));
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if (myNodeInfo.device_id.size == 16) {
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CryptRNG.stir(myNodeInfo.device_id.bytes, myNodeInfo.device_id.size);
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}
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auto noise = random();
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CryptRNG.stir((uint8_t *)&noise, sizeof(noise));
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LOG_DEBUG("Generate Curve25519 keypair");
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Curve25519::dh1(public_key, private_key);
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memcpy(pubKey, public_key, sizeof(public_key));
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memcpy(privKey, private_key, sizeof(private_key));
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}
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/**
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* regenerate a public key with Curve25519.
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*
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* @param pubKey The destination for the public key.
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* @param privKey The source for the private key.
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*/
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bool CryptoEngine::regeneratePublicKey(uint8_t *pubKey, uint8_t *privKey)
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{
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if (!memfll(privKey, 0, sizeof(private_key))) {
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Curve25519::eval(pubKey, privKey, 0);
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if (Curve25519::isWeakPoint(pubKey)) {
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LOG_ERROR("PKI key generation failed. Specified private key results in a weak");
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memset(pubKey, 0, 32);
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return false;
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}
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memcpy(private_key, privKey, sizeof(private_key));
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memcpy(public_key, pubKey, sizeof(public_key));
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} else {
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LOG_WARN("X25519 key generation failed due to blank private key");
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return false;
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}
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return true;
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}
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#endif
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/**
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* Encrypt a packet's payload using a key generated with Curve25519 and SHA256
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* for a specific node.
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*
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* @param toNode The MeshPacket `to` field.
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* @param fromNode The MeshPacket `from` field.
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* @param remotePublic The remote node's Curve25519 public key.
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* @param packetId The MeshPacket `id` field.
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* @param numBytes Number of bytes of plaintext in the bytes buffer.
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* @param bytes Buffer containing plaintext input.
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* @param bytesOut Output buffer to be populated with encrypted ciphertext.
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*/
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bool CryptoEngine::encryptCurve25519(uint32_t toNode, uint32_t fromNode, meshtastic_UserLite_public_key_t remotePublic,
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uint64_t packetNum, size_t numBytes, const uint8_t *bytes, uint8_t *bytesOut)
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{
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uint8_t *auth;
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long extraNonceTmp = random();
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auth = bytesOut + numBytes;
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memcpy((uint8_t *)(auth + 8), &extraNonceTmp,
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sizeof(uint32_t)); // do not use dereference on potential non aligned pointers : *extraNonce = extraNonceTmp;
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LOG_DEBUG("Random nonce value: %d", extraNonceTmp);
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if (remotePublic.size == 0) {
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LOG_DEBUG("Node %d or their public_key not found", toNode);
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return false;
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}
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if (!setDHPublicKey(remotePublic.bytes)) {
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return false;
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}
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hash(shared_key, 32);
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initNonce(fromNode, packetNum, extraNonceTmp);
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// Calculate the shared secret with the destination node and encrypt
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printBytes("Attempt encrypt with nonce: ", nonce, 13);
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printBytes("Attempt encrypt with shared_key starting with: ", shared_key, 8);
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aes_ccm_ae(shared_key, 32, nonce, 8, bytes, numBytes, nullptr, 0, bytesOut,
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auth); // this can write up to 15 bytes longer than numbytes past bytesOut
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memcpy((uint8_t *)(auth + 8), &extraNonceTmp,
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sizeof(uint32_t)); // do not use dereference on potential non aligned pointers : *extraNonce = extraNonceTmp;
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return true;
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}
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/**
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* Decrypt a packet's payload using a key generated with Curve25519 and SHA256
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* for a specific node.
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*
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* @param fromNode The MeshPacket `from` field.
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* @param remotePublic The remote node's Curve25519 public key.
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* @param packetId The MeshPacket `id` field.
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* @param numBytes Number of bytes of ciphertext in the bytes buffer.
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* @param bytes Buffer containing ciphertext input.
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* @param bytesOut Output buffer to be populated with decrypted plaintext.
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*/
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bool CryptoEngine::decryptCurve25519(uint32_t fromNode, meshtastic_UserLite_public_key_t remotePublic, uint64_t packetNum,
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size_t numBytes, const uint8_t *bytes, uint8_t *bytesOut)
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{
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const uint8_t *auth = bytes + numBytes - 12; // set to last 8 bytes of text?
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uint32_t extraNonce; // pointer was not really used
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memcpy(&extraNonce, auth + 8,
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sizeof(uint32_t)); // do not use dereference on potential non aligned pointers : (uint32_t *)(auth + 8);
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LOG_INFO("Random nonce value: %d", extraNonce);
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if (remotePublic.size == 0) {
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LOG_DEBUG("Node or its public key not found in database");
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return false;
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}
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// Calculate the shared secret with the sending node and decrypt
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if (!setDHPublicKey(remotePublic.bytes)) {
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return false;
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}
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hash(shared_key, 32);
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initNonce(fromNode, packetNum, extraNonce);
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printBytes("Attempt decrypt with nonce: ", nonce, 13);
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printBytes("Attempt decrypt with shared_key starting with: ", shared_key, 8);
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return aes_ccm_ad(shared_key, 32, nonce, 8, bytes, numBytes - 12, nullptr, 0, auth, bytesOut);
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}
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void CryptoEngine::setDHPrivateKey(uint8_t *_private_key)
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{
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memcpy(private_key, _private_key, 32);
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}
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/**
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* Hash arbitrary data using SHA256.
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*
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* @param bytes
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* @param numBytes
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*/
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void CryptoEngine::hash(uint8_t *bytes, size_t numBytes)
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{
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SHA256 hash;
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size_t posn;
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uint8_t size = numBytes;
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uint8_t inc = 16;
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hash.reset();
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for (posn = 0; posn < size; posn += inc) {
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size_t len = size - posn;
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if (len > inc)
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len = inc;
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hash.update(bytes + posn, len);
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}
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hash.finalize(bytes, 32);
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}
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void CryptoEngine::aesSetKey(const uint8_t *key_bytes, size_t key_len)
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{
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delete aes;
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aes = nullptr;
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if (key_len != 0) {
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aes = new AESSmall256();
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aes->setKey(key_bytes, key_len);
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}
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}
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void CryptoEngine::aesEncrypt(uint8_t *in, uint8_t *out)
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{
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aes->encryptBlock(out, in);
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}
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bool CryptoEngine::setDHPublicKey(uint8_t *pubKey)
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{
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uint8_t local_priv[32];
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memcpy(shared_key, pubKey, 32);
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memcpy(local_priv, private_key, 32);
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// Calculate the shared secret with the specified node's public key and our private key
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// This includes an internal weak key check, which among other things looks for an all 0 public key and shared key.
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if (!Curve25519::dh2(shared_key, local_priv)) {
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LOG_WARN("Curve25519DH step 2 failed!");
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return false;
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}
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return true;
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}
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#endif
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concurrency::Lock *cryptLock;
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void CryptoEngine::setKey(const CryptoKey &k)
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{
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LOG_DEBUG("Use AES%d key!", k.length * 8);
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key = k;
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}
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/**
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* Encrypt a packet
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*
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* @param bytes is updated in place
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*/
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void CryptoEngine::encryptPacket(uint32_t fromNode, uint64_t packetId, size_t numBytes, uint8_t *bytes)
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{
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if (key.length > 0) {
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initNonce(fromNode, packetId);
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if (numBytes <= MAX_BLOCKSIZE) {
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encryptAESCtr(key, nonce, numBytes, bytes);
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} else {
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LOG_ERROR("Packet too large for crypto engine: %d. noop encryption!", numBytes);
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}
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}
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}
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void CryptoEngine::decrypt(uint32_t fromNode, uint64_t packetId, size_t numBytes, uint8_t *bytes)
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{
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// For CTR, the implementation is the same
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encryptPacket(fromNode, packetId, numBytes, bytes);
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}
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// Generic implementation of AES-CTR encryption.
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void CryptoEngine::encryptAESCtr(CryptoKey _key, uint8_t *_nonce, size_t numBytes, uint8_t *bytes)
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{
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delete ctr;
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ctr = nullptr;
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if (_key.length == 16)
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ctr = new CTR<AES128>();
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else
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ctr = new CTR<AES256>();
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ctr->setKey(_key.bytes, _key.length);
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static uint8_t scratch[MAX_BLOCKSIZE];
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memcpy(scratch, bytes, numBytes);
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memset(scratch + numBytes, 0,
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sizeof(scratch) - numBytes); // Fill rest of buffer with zero (in case cypher looks at it)
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ctr->setIV(_nonce, 16);
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ctr->setCounterSize(4);
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ctr->encrypt(bytes, scratch, numBytes);
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}
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/**
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* Init our 128 bit nonce for a new packet
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*/
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void CryptoEngine::initNonce(uint32_t fromNode, uint64_t packetId, uint32_t extraNonce)
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{
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memset(nonce, 0, sizeof(nonce));
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// use memcpy to avoid breaking strict-aliasing
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memcpy(nonce, &packetId, sizeof(uint64_t));
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memcpy(nonce + sizeof(uint64_t), &fromNode, sizeof(uint32_t));
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if (extraNonce)
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memcpy(nonce + sizeof(uint32_t), &extraNonce, sizeof(uint32_t));
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}
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#ifndef HAS_CUSTOM_CRYPTO_ENGINE
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CryptoEngine *crypto = new CryptoEngine;
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#endif
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