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/*
WhatsApp plugin for Miranda NG
Copyright © 2019-22 George Hazan
WANoise class implementation
*/
#include "stdafx.h"
static uint8_t intro_header[] = {87, 65, 6, DICT_VERSION};
static uint8_t noise_init[] = "Noise_XX_25519_AESGCM_SHA256\0\0\0\0";
WANoise::WANoise(WhatsAppProto *_ppro) :
ppro(_ppro)
{
salt.assign(noise_init, 32);
encKey.assign(noise_init, 32);
decKey.assign(noise_init, 32);
// generate ephemeral keys: public & private
ec_key_pair *pKeys;
curve_generate_key_pair(ppro->m_signalStore.CTX(), &pKeys);
auto *pPubKey = ec_key_pair_get_public(pKeys);
ephemeral.pub.assign(pPubKey->data, sizeof(pPubKey->data));
auto *pPrivKey = ec_key_pair_get_private(pKeys);
ephemeral.priv.assign(pPrivKey->data, sizeof(pPrivKey->data));
ec_key_pair_destroy((signal_type_base*)pKeys);
// prepare hash
memcpy(hash, noise_init, 32);
updateHash(intro_header, 4);
updateHash(ephemeral.pub.data(), ephemeral.pub.length());
}
/////////////////////////////////////////////////////////////////////////////////////////
// libsignal data initialization
void WANoise::init()
{
// no data? generate them
if (ppro->getDword(DBKEY_REG_ID, 0xFFFF) == 0xFFFF) {
// generate registration id
uint32_t regId;
Utils_GetRandom(®Id, sizeof(regId));
ppro->setDword(DBKEY_REG_ID, regId & 0x3FFF);
// generate secret key
uint8_t secretKey[32];
Utils_GetRandom(secretKey, sizeof(secretKey));
db_set_blob(0, ppro->m_szModuleName, DBKEY_SECRET_KEY, secretKey, sizeof(secretKey));
// generate noise keys (private & public)
ec_key_pair *pKeys;
curve_generate_key_pair(ppro->m_signalStore.CTX(), &pKeys);
auto *pPubKey = ec_key_pair_get_public(pKeys);
db_set_blob(0, ppro->m_szModuleName, DBKEY_NOISE_PUB, pPubKey->data, sizeof(pPubKey->data));
auto *pPrivKey = ec_key_pair_get_private(pKeys);
db_set_blob(0, ppro->m_szModuleName, DBKEY_NOISE_PRIV, pPrivKey->data, sizeof(pPrivKey->data));
ec_key_pair_destroy((signal_type_base *)pKeys);
}
noiseKeys.pub = ppro->getBlob(DBKEY_NOISE_PUB);
noiseKeys.priv = ppro->getBlob(DBKEY_NOISE_PRIV);
}
void WANoise::finish()
{
deriveKey("", 0, encKey, decKey);
readCounter = writeCounter = 0;
memset(hash, 0, sizeof(hash));
bInitFinished = true;
}
void WANoise::deriveKey(const void *pData, size_t cbLen, MBinBuffer &write, MBinBuffer &read)
{
size_t outlen = 64;
uint8_t out[64];
HKDF(EVP_sha256(), salt.data(), (int)salt.length(), (BYTE *)pData, (int)cbLen, (BYTE *)"", 0, out, outlen);
write.assign(out, 32);
read.assign(out + 32, 32);
}
void WANoise::mixIntoKey(const void *n, const void *p)
{
uint8_t tmp[32];
curve25519_donna((unsigned char *)tmp, (const unsigned char *)n, (const unsigned char *)p);
deriveKey(tmp, sizeof(tmp), salt, encKey);
decKey.assign(encKey.data(), encKey.length());
readCounter = writeCounter = 0;
}
MBinBuffer WANoise::decrypt(const void *pData, size_t cbLen)
{
uint8_t iv[12];
generateIV(iv, (bInitFinished) ? readCounter : writeCounter);
MBinBuffer res;
if (!bInitFinished)
res = aesDecrypt(EVP_aes_256_gcm(), decKey.data(), iv, pData, cbLen, hash, sizeof(hash));
else
res = aesDecrypt(EVP_aes_256_gcm(), decKey.data(), iv, pData, cbLen);
updateHash(pData, cbLen);
return res;
}
size_t WANoise::decodeFrame(const uint8_t *&p, size_t &cbLen)
{
if (cbLen < 3)
return 0;
size_t payloadLen = 0;
for (int i = 0; i < 3; i++) {
payloadLen <<= 8;
payloadLen += p[i];
}
// ppro->debugLogA("got payload of size %d", payloadLen);
cbLen -= 3;
if (payloadLen > cbLen) {
ppro->debugLogA("payload length %d exceeds capacity %d", payloadLen, cbLen);
return 0;
}
p += 3;
return payloadLen;
}
MBinBuffer WANoise::encodeFrame(const void *pData, size_t cbLen)
{
MBinBuffer res;
if (!bSendIntro) {
bSendIntro = true;
res.append(intro_header, 4);
}
uint8_t buf[3];
size_t foo = cbLen;
for (int i = 0; i < 3; i++) {
buf[2 - i] = foo & 0xFF;
foo >>= 8;
}
res.append(buf, 3);
res.append(pData, cbLen);
return res;
}
MBinBuffer WANoise::encrypt(const void *pData, size_t cbLen)
{
uint8_t iv[12];
generateIV(iv, writeCounter);
MBinBuffer res;
uint8_t outbuf[1024 + 64];
int enc_len = 0, final_len = 0;
EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
EVP_EncryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, encKey.data(), iv);
if (!bInitFinished)
EVP_EncryptUpdate(ctx, NULL, &enc_len, hash, sizeof(hash));
for (size_t len = 0; len < cbLen; len += 1024) {
size_t portionSize = cbLen - len;
EVP_EncryptUpdate(ctx, outbuf, &enc_len, (BYTE *)pData + len, (int)min(portionSize, 1024));
res.append(outbuf, enc_len);
}
EVP_EncryptFinal_ex(ctx, outbuf, &final_len);
if (final_len)
res.append(outbuf, final_len);
uint8_t tag[16];
EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, sizeof(tag), tag);
res.append(tag, sizeof(tag));
EVP_CIPHER_CTX_free(ctx);
updateHash(res.data(), res.length());
return res;
}
void WANoise::updateHash(const void *pData, size_t cbLen)
{
if (bInitFinished)
return;
SHA256_CTX ctx;
SHA256_Init(&ctx);
SHA256_Update(&ctx, hash, sizeof(hash));
SHA256_Update(&ctx, pData, cbLen);
SHA256_Final(hash, &ctx);
}
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