git / moonbite-core / src/crypto/chacha_poly_aead.cpp · raw

// Copyright (c) 2019 The Bitcoin Core developers// Distributed under the MIT software license, see the accompanying// file COPYING or http://www.opensource.org/licenses/mit-license.php.#include <crypto/chacha_poly_aead.h>#include <crypto/poly1305.h>#include <support/cleanse.h>#include <assert.h>#include <string.h>#include <cstdio>#include <limits>#ifndef HAVE_TIMINGSAFE_BCMPint timingsafe_bcmp(const unsigned char* b1, const unsigned char* b2, size_t n){    const unsigned char *p1 = b1, *p2 = b2;    int ret = 0;    for (; n > 0; n--)        ret |= *p1++ ^ *p2++;    return (ret != 0);}#endif // TIMINGSAFE_BCMPChaCha20Poly1305AEAD::ChaCha20Poly1305AEAD(const unsigned char* K_1, size_t K_1_len, const unsigned char* K_2, size_t K_2_len){    assert(K_1_len == CHACHA20_POLY1305_AEAD_KEY_LEN);    assert(K_2_len == CHACHA20_POLY1305_AEAD_KEY_LEN);    m_chacha_main.SetKey(K_1, CHACHA20_POLY1305_AEAD_KEY_LEN);    m_chacha_header.SetKey(K_2, CHACHA20_POLY1305_AEAD_KEY_LEN);    // set the cached sequence number to uint64 max which hints for an unset cache.    // we can't hit uint64 max since the rekey rule (which resets the sequence number) is 1GB    m_cached_aad_seqnr = std::numeric_limits<uint64_t>::max();}bool ChaCha20Poly1305AEAD::Crypt(uint64_t seqnr_payload, uint64_t seqnr_aad, int aad_pos, unsigned char* dest, size_t dest_len /* length of the output buffer for sanity checks */, const unsigned char* src, size_t src_len, bool is_encrypt){    // check buffer boundaries    if (        // if we encrypt, make sure the source contains at least the expected AAD and the destination has at least space for the source + MAC        (is_encrypt && (src_len < CHACHA20_POLY1305_AEAD_AAD_LEN || dest_len < src_len + POLY1305_TAGLEN)) ||        // if we decrypt, make sure the source contains at least the expected AAD+MAC and the destination has at least space for the source - MAC        (!is_encrypt && (src_len < CHACHA20_POLY1305_AEAD_AAD_LEN + POLY1305_TAGLEN || dest_len < src_len - POLY1305_TAGLEN))) {        return false;    }    unsigned char expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN];    memset(poly_key, 0, sizeof(poly_key));    m_chacha_main.SetIV(seqnr_payload);    // block counter 0 for the poly1305 key    // use lower 32bytes for the poly1305 key    // (throws away 32 unused bytes (upper 32) from this ChaCha20 round)    m_chacha_main.Seek(0);    m_chacha_main.Crypt(poly_key, poly_key, sizeof(poly_key));    // if decrypting, verify the tag prior to decryption    if (!is_encrypt) {        const unsigned char* tag = src + src_len - POLY1305_TAGLEN;        poly1305_auth(expected_tag, src, src_len - POLY1305_TAGLEN, poly_key);        // constant time compare the calculated MAC with the provided MAC        if (timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN) != 0) {            memory_cleanse(expected_tag, sizeof(expected_tag));            memory_cleanse(poly_key, sizeof(poly_key));            return false;        }        memory_cleanse(expected_tag, sizeof(expected_tag));        // MAC has been successfully verified, make sure we don't covert it in decryption        src_len -= POLY1305_TAGLEN;    }    // calculate and cache the next 64byte keystream block if requested sequence number is not yet the cache    if (m_cached_aad_seqnr != seqnr_aad) {        m_cached_aad_seqnr = seqnr_aad;        m_chacha_header.SetIV(seqnr_aad);        m_chacha_header.Seek(0);        m_chacha_header.Keystream(m_aad_keystream_buffer, CHACHA20_ROUND_OUTPUT);    }    // crypt the AAD (3 bytes message length) with given position in AAD cipher instance keystream    dest[0] = src[0] ^ m_aad_keystream_buffer[aad_pos];    dest[1] = src[1] ^ m_aad_keystream_buffer[aad_pos + 1];    dest[2] = src[2] ^ m_aad_keystream_buffer[aad_pos + 2];    // Set the playload ChaCha instance block counter to 1 and crypt the payload    m_chacha_main.Seek(1);    m_chacha_main.Crypt(src + CHACHA20_POLY1305_AEAD_AAD_LEN, dest + CHACHA20_POLY1305_AEAD_AAD_LEN, src_len - CHACHA20_POLY1305_AEAD_AAD_LEN);    // If encrypting, calculate and append tag    if (is_encrypt) {        // the poly1305 tag expands over the AAD (3 bytes length) & encrypted payload        poly1305_auth(dest + src_len, dest, src_len, poly_key);    }    // cleanse no longer required MAC and polykey    memory_cleanse(poly_key, sizeof(poly_key));    return true;}bool ChaCha20Poly1305AEAD::GetLength(uint32_t* len24_out, uint64_t seqnr_aad, int aad_pos, const uint8_t* ciphertext){    // enforce valid aad position to avoid accessing outside of the 64byte keystream cache    // (there is space for 21 times 3 bytes)    assert(aad_pos >= 0 && aad_pos < CHACHA20_ROUND_OUTPUT - CHACHA20_POLY1305_AEAD_AAD_LEN);    if (m_cached_aad_seqnr != seqnr_aad) {        // we need to calculate the 64 keystream bytes since we reached a new aad sequence number        m_cached_aad_seqnr = seqnr_aad;        m_chacha_header.SetIV(seqnr_aad);                                         // use LE for the nonce        m_chacha_header.Seek(0);                                                  // block counter 0        m_chacha_header.Keystream(m_aad_keystream_buffer, CHACHA20_ROUND_OUTPUT); // write keystream to the cache    }    // decrypt the ciphertext length by XORing the right position of the 64byte keystream cache with the ciphertext    *len24_out = (ciphertext[0] ^ m_aad_keystream_buffer[aad_pos + 0]) |                 (ciphertext[1] ^ m_aad_keystream_buffer[aad_pos + 1]) << 8 |                 (ciphertext[2] ^ m_aad_keystream_buffer[aad_pos + 2]) << 16;    return true;}