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/*-
* Copyright (c) 2017-2022 Ribose Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <string.h>
#include <cassert>
#include <botan/ffi.h>
#include "hash_botan.hpp"
#include "botan_utils.hpp"
#include "ecdh.h"
#include "ec.h"
#include "ecdh_utils.h"
#include "symmetric.h"
#include "types.h"
#include "utils.h"
#include "mem.h"
namespace pgp {
namespace ecdh {
// Produces kek of size kek_len which corresponds to length of wrapping key
static bool
compute_kek(uint8_t * kek,
size_t kek_len,
const std::vector<uint8_t> &other_info,
const ec::Curve * curve_desc,
const mpi & ec_pubkey,
const rnp::botan::Privkey & ec_prvkey,
const pgp_hash_alg_t hash_alg)
{
auto * p = ec_pubkey.data();
size_t p_len = ec_pubkey.size();
if (curve_desc->rnp_curve_id == PGP_CURVE_25519) {
if ((p_len != 33) || (p[0] != 0x40)) {
return false;
}
p++;
p_len--;
}
rnp::secure_bytes s(MAX_CURVE_BYTELEN * 2 + 1, 0);
size_t s_len = s.size();
rnp::botan::op::KeyAgreement op;
if (botan_pk_op_key_agreement_create(&op.get(), ec_prvkey.get(), "Raw", 0) ||
botan_pk_op_key_agreement(op.get(), s.data(), &s_len, p, p_len, NULL, 0)) {
return false;
}
char kdf_name[32] = {0};
snprintf(
kdf_name, sizeof(kdf_name), "SP800-56A(%s)", rnp::Hash_Botan::name_backend(hash_alg));
return !botan_kdf(
kdf_name, kek, kek_len, s.data(), s_len, NULL, 0, other_info.data(), other_info.size());
}
static bool
load_public_key(rnp::botan::Pubkey &pubkey, const ec::Key &key)
{
auto curve = ec::Curve::get(key.curve);
if (!curve) {
RNP_LOG("unknown curve");
return false;
}
if (curve->rnp_curve_id == PGP_CURVE_25519) {
if ((key.p.size() != 33) || (key.p[0] != 0x40)) {
return false;
}
rnp::secure_array<uint8_t, 32> pkey;
memcpy(pkey.data(), key.p.data() + 1, 32);
return !botan_pubkey_load_x25519(&pubkey.get(), pkey.data());
}
if (!key.p.size() || (key.p[0] != 0x04)) {
RNP_LOG("Failed to load public key");
return false;
}
const size_t curve_order = curve->bytes();
if (key.p.size() != 2 * curve_order + 1) {
RNP_LOG("Invalid ECDH public key length");
return false;
}
rnp::bn px(&key.p[1], curve_order);
rnp::bn py(&key.p[1 + curve_order], curve_order);
if (!px || !py) {
return false;
}
if (!botan_pubkey_load_ecdh(&pubkey.get(), px.get(), py.get(), curve->botan_name)) {
return true;
}
RNP_LOG("failed to load ecdh public key");
return false;
}
static bool
load_secret_key(rnp::botan::Privkey &seckey, const ec::Key &key)
{
auto curve = ec::Curve::get(key.curve);
if (!curve) {
return false;
}
if (curve->rnp_curve_id == PGP_CURVE_25519) {
if (key.x.size() != 32) {
RNP_LOG("wrong x25519 key");
return false;
}
/* need to reverse byte order since in mpi we have big-endian */
rnp::secure_array<uint8_t, 32> prkey;
for (int i = 0; i < 32; i++) {
prkey[i] = key.x[31 - i];
}
return !botan_privkey_load_x25519(&seckey.get(), prkey.data());
}
rnp::bn bx(key.x);
return bx && !botan_privkey_load_ecdh(&seckey.get(), bx.get(), curve->botan_name);
}
rnp_result_t
validate_key(rnp::RNG &rng, const ec::Key &key, bool secret)
{
auto curve_desc = ec::Curve::get(key.curve);
if (!curve_desc) {
return RNP_ERROR_NOT_SUPPORTED;
}
rnp::botan::Pubkey bpkey;
if (!load_public_key(bpkey, key) || botan_pubkey_check_key(bpkey.get(), rng.handle(), 0)) {
return RNP_ERROR_BAD_PARAMETERS;
}
if (!secret) {
return RNP_SUCCESS;
}
rnp::botan::Privkey bskey;
if (!load_secret_key(bskey, key) ||
botan_privkey_check_key(bskey.get(), rng.handle(), 0)) {
return RNP_ERROR_BAD_PARAMETERS;
}
return RNP_SUCCESS;
}
rnp_result_t
encrypt_pkcs5(rnp::RNG &rng, Encrypted &out, const rnp::secure_bytes &in, const ec::Key &key)
{
if (in.size() > MAX_SESSION_KEY_SIZE) {
return RNP_ERROR_BAD_PARAMETERS;
}
const size_t m_padded_len = ((in.size() / 8) + 1) * 8;
// +8 because of AES-wrap adds 8 bytes
if (ECDH_WRAPPED_KEY_SIZE < (m_padded_len + 8)) {
return RNP_ERROR_BAD_PARAMETERS;
}
#if !defined(ENABLE_SM2)
if (key.curve == PGP_CURVE_SM2_P_256) {
RNP_LOG("SM2 curve support is disabled.");
return RNP_ERROR_NOT_IMPLEMENTED;
}
#endif
auto curve_desc = ec::Curve::get(key.curve);
if (!curve_desc) {
RNP_LOG("unsupported curve");
return RNP_ERROR_NOT_SUPPORTED;
}
// See 13.5 of RFC 4880 for definition of other_info size
const size_t kek_len = pgp_key_size(key.key_wrap_alg);
auto other_info =
kdf_other_info_serialize(*curve_desc, out.fp, key.kdf_hash_alg, key.key_wrap_alg);
assert(other_info.size() == curve_desc->OID.size() + 46);
rnp::botan::Privkey eph_prv_key;
int res = 0;
if (!strcmp(curve_desc->botan_name, "curve25519")) {
res = botan_privkey_create(&eph_prv_key.get(), "Curve25519", "", rng.handle());
} else {
res = botan_privkey_create(
&eph_prv_key.get(), "ECDH", curve_desc->botan_name, rng.handle());
}
if (res) {
return RNP_ERROR_GENERIC;
}
uint8_t kek[32] = {0}; // Size of SHA-256 or smaller
if (!compute_kek(
kek, kek_len, other_info, curve_desc, key.p, eph_prv_key, key.kdf_hash_alg)) {
RNP_LOG("KEK computation failed");
return RNP_ERROR_GENERIC;
}
// 'm' is padded to the 8-byte granularity
rnp::secure_bytes m = in;
pad_pkcs7(m, m_padded_len - m.size());
size_t mlen = ECDH_WRAPPED_KEY_SIZE;
out.m.resize(ECDH_WRAPPED_KEY_SIZE);
#if defined(CRYPTO_BACKEND_BOTAN3)
char name[16];
snprintf(name, sizeof(name), "AES-%zu", 8 * kek_len);
if (botan_nist_kw_enc(name, 0, m.data(), m.size(), kek, kek_len, out.m.data(), &mlen)) {
#else
if (botan_key_wrap3394(m.data(), m.size(), kek, kek_len, out.m.data(), &mlen)) {
#endif
return RNP_ERROR_GENERIC;
}
out.m.resize(mlen);
/* export ephemeral public key */
out.p.resize(MAX_CURVE_BYTELEN * 2 + 1);
size_t plen = out.p.size();
/* we need to prepend 0x40 for the x25519 */
if (key.curve == PGP_CURVE_25519) {
plen--;
if (botan_pk_op_key_agreement_export_public(
eph_prv_key.get(), out.p.data() + 1, &plen)) {
return RNP_ERROR_GENERIC;
}
out.p[0] = 0x40;
out.p.resize(plen + 1);
} else {
if (botan_pk_op_key_agreement_export_public(eph_prv_key.get(), out.p.data(), &plen)) {
return RNP_ERROR_GENERIC;
}
out.p.resize(plen);
}
// All OK
return RNP_SUCCESS;
}
rnp_result_t
decrypt_pkcs5(rnp::secure_bytes &out, const Encrypted &in, const ec::Key &key)
{
if (!key.x.size()) {
return RNP_ERROR_BAD_PARAMETERS;
}
auto curve_desc = ec::Curve::get(key.curve);
if (!curve_desc) {
RNP_LOG("unknown curve");
return RNP_ERROR_NOT_SUPPORTED;
}
auto wrap_alg = key.key_wrap_alg;
auto kdf_hash = key.kdf_hash_alg;
/* Ensure that AES is used for wrapping */
if (!pgp_is_sa_aes(wrap_alg)) {
RNP_LOG("non-aes wrap algorithm");
return RNP_ERROR_NOT_SUPPORTED;
}
// See 13.5 of RFC 4880 for definition of other_info_size
auto other_info = kdf_other_info_serialize(*curve_desc, in.fp, kdf_hash, wrap_alg);
assert(other_info.size() == curve_desc->OID.size() + 46);
rnp::botan::Privkey prv_key;
if (!load_secret_key(prv_key, key)) {
RNP_LOG("failed to load ecdh secret key");
return RNP_ERROR_GENERIC;
}
// Size of SHA-256 or smaller
rnp::secure_array<uint8_t, MAX_SYMM_KEY_SIZE> kek;
/* Security: Always return same error code in case compute_kek,
* botan_key_unwrap3394 or unpad_pkcs7 fails
*/
size_t kek_len = pgp_key_size(wrap_alg);
if (!compute_kek(kek.data(), kek_len, other_info, curve_desc, in.p, prv_key, kdf_hash)) {
return RNP_ERROR_GENERIC;
}
size_t deckey_len = MAX_SESSION_KEY_SIZE;
out.resize(deckey_len);
#if defined(CRYPTO_BACKEND_BOTAN3)
char name[16];
snprintf(name, sizeof(name), "AES-%zu", 8 * kek_len);
if (botan_nist_kw_dec(
name, 0, in.m.data(), in.m.size(), kek.data(), kek_len, out.data(), &deckey_len)) {
#else
if (botan_key_unwrap3394(
in.m.data(), in.m.size(), kek.data(), kek_len, out.data(), &deckey_len)) {
#endif
return RNP_ERROR_GENERIC;
}
out.resize(deckey_len);
if (!unpad_pkcs7(out)) {
return RNP_ERROR_GENERIC;
}
return RNP_SUCCESS;
}
} // namespace ecdh
} // namespace pgp