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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 <botan/ffi.h>
#include "hash_botan.hpp"
#include "ecdh.h"
#include "ecdh_utils.h"
#include "symmetric.h"
#include "types.h"
#include "utils.h"
#include "mem.h"
#include "bn.h"
// 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 uint8_t * other_info,
size_t other_info_size,
const ec_curve_desc_t *curve_desc,
const pgp_mpi_t * ec_pubkey,
const botan_privkey_t ec_prvkey,
const pgp_hash_alg_t hash_alg)
{
const uint8_t *p = ec_pubkey->mpi;
uint8_t p_len = ec_pubkey->len;
if (curve_desc->rnp_curve_id == PGP_CURVE_25519) {
if ((p_len != 33) || (p[0] != 0x40)) {
return false;
}
p++;
p_len--;
}
rnp::secure_array<uint8_t, MAX_CURVE_BYTELEN * 2 + 1> s;
botan_pk_op_ka_t op_key_agreement = NULL;
bool ret = false;
char kdf_name[32] = {0};
size_t s_len = s.size();
if (botan_pk_op_key_agreement_create(&op_key_agreement, ec_prvkey, "Raw", 0) ||
botan_pk_op_key_agreement(op_key_agreement, s.data(), &s_len, p, p_len, NULL, 0)) {
goto end;
}
snprintf(
kdf_name, sizeof(kdf_name), "SP800-56A(%s)", rnp::Hash_Botan::name_backend(hash_alg));
ret = !botan_kdf(
kdf_name, kek, kek_len, s.data(), s_len, NULL, 0, other_info, other_info_size);
end:
return ret && !botan_pk_op_key_agreement_destroy(op_key_agreement);
}
static bool
ecdh_load_public_key(botan_pubkey_t *pubkey, const pgp_ec_key_t *key)
{
bool res = false;
const ec_curve_desc_t *curve = get_curve_desc(key->curve);
if (!curve) {
RNP_LOG("unknown curve");
return false;
}
if (curve->rnp_curve_id == PGP_CURVE_25519) {
if ((key->p.len != 33) || (key->p.mpi[0] != 0x40)) {
return false;
}
rnp::secure_array<uint8_t, 32> pkey;
memcpy(pkey.data(), key->p.mpi + 1, 32);
return !botan_pubkey_load_x25519(pubkey, pkey.data());
}
if (!mpi_bytes(&key->p) || (key->p.mpi[0] != 0x04)) {
RNP_LOG("Failed to load public key");
return false;
}
botan_mp_t px = NULL;
botan_mp_t py = NULL;
const size_t curve_order = BITS_TO_BYTES(curve->bitlen);
if (botan_mp_init(&px) || botan_mp_init(&py) ||
botan_mp_from_bin(px, &key->p.mpi[1], curve_order) ||
botan_mp_from_bin(py, &key->p.mpi[1 + curve_order], curve_order)) {
goto end;
}
if (!(res = !botan_pubkey_load_ecdh(pubkey, px, py, curve->botan_name))) {
RNP_LOG("failed to load ecdh public key");
}
end:
botan_mp_destroy(px);
botan_mp_destroy(py);
return res;
}
static bool
ecdh_load_secret_key(botan_privkey_t *seckey, const pgp_ec_key_t *key)
{
const ec_curve_desc_t *curve = get_curve_desc(key->curve);
if (!curve) {
return false;
}
if (curve->rnp_curve_id == PGP_CURVE_25519) {
if (key->x.len != 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.mpi[31 - i];
}
return !botan_privkey_load_x25519(seckey, prkey.data());
}
bignum_t *x = NULL;
if (!(x = mpi2bn(&key->x))) {
return false;
}
bool res = !botan_privkey_load_ecdh(seckey, BN_HANDLE_PTR(x), curve->botan_name);
bn_free(x);
return res;
}
rnp_result_t
ecdh_validate_key(rnp::RNG *rng, const pgp_ec_key_t *key, bool secret)
{
botan_pubkey_t bpkey = NULL;
botan_privkey_t bskey = NULL;
rnp_result_t ret = RNP_ERROR_BAD_PARAMETERS;
const ec_curve_desc_t *curve_desc = get_curve_desc(key->curve);
if (!curve_desc) {
return RNP_ERROR_NOT_SUPPORTED;
}
if (!ecdh_load_public_key(&bpkey, key) ||
botan_pubkey_check_key(bpkey, rng->handle(), 0)) {
goto done;
}
if (!secret) {
ret = RNP_SUCCESS;
goto done;
}
if (!ecdh_load_secret_key(&bskey, key) ||
botan_privkey_check_key(bskey, rng->handle(), 0)) {
goto done;
}
ret = RNP_SUCCESS;
done:
botan_privkey_destroy(bskey);
botan_pubkey_destroy(bpkey);
return ret;
}
rnp_result_t
ecdh_encrypt_pkcs5(rnp::RNG * rng,
pgp_ecdh_encrypted_t * out,
const uint8_t *const in,
size_t in_len,
const pgp_ec_key_t * key,
const pgp_fingerprint_t &fingerprint)
{
botan_privkey_t eph_prv_key = NULL;
rnp_result_t ret = RNP_ERROR_GENERIC;
uint8_t other_info[MAX_SP800_56A_OTHER_INFO];
uint8_t kek[32] = {0}; // Size of SHA-256 or smaller
// 'm' is padded to the 8-byte granularity
uint8_t m[MAX_SESSION_KEY_SIZE];
const size_t m_padded_len = ((in_len / 8) + 1) * 8;
if (!key || !out || !in || (in_len > sizeof(m))) {
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
const ec_curve_desc_t *curve_desc = get_curve_desc(key->curve);
if (!curve_desc) {
RNP_LOG("unsupported curve");
return RNP_ERROR_NOT_SUPPORTED;
}
// +8 because of AES-wrap adds 8 bytes
if (ECDH_WRAPPED_KEY_SIZE < (m_padded_len + 8)) {
return RNP_ERROR_BAD_PARAMETERS;
}
// See 13.5 of RFC 4880 for definition of other_info_size
const size_t other_info_size = curve_desc->OIDhex_len + 46;
const size_t kek_len = pgp_key_size(key->key_wrap_alg);
size_t tmp_len = kdf_other_info_serialize(
other_info, curve_desc, fingerprint, key->kdf_hash_alg, key->key_wrap_alg);
if (tmp_len != other_info_size) {
RNP_LOG("Serialization of other info failed");
return RNP_ERROR_GENERIC;
}
if (!strcmp(curve_desc->botan_name, "curve25519")) {
if (botan_privkey_create(&eph_prv_key, "Curve25519", "", rng->handle())) {
goto end;
}
} else {
if (botan_privkey_create(
&eph_prv_key, "ECDH", curve_desc->botan_name, rng->handle())) {
goto end;
}
}
if (!compute_kek(kek,
kek_len,
other_info,
other_info_size,
curve_desc,
&key->p,
eph_prv_key,
key->kdf_hash_alg)) {
RNP_LOG("KEK computation failed");
goto end;
}
memcpy(m, in, in_len);
if (!pad_pkcs7(m, m_padded_len, in_len)) {
// Should never happen
goto end;
}
out->mlen = sizeof(out->m);
#if defined(CRYPTO_BACKEND_BOTAN3)
char name[8];
snprintf(name, sizeof(name), "AES-%zu", 8 * kek_len);
if (botan_nist_kw_enc(name, 0, m, m_padded_len, kek, kek_len, out->m, &out->mlen)) {
#else
if (botan_key_wrap3394(m, m_padded_len, kek, kek_len, out->m, &out->mlen)) {
#endif
goto end;
}
/* we need to prepend 0x40 for the x25519 */
if (key->curve == PGP_CURVE_25519) {
out->p.len = sizeof(out->p.mpi) - 1;
if (botan_pk_op_key_agreement_export_public(
eph_prv_key, out->p.mpi + 1, &out->p.len)) {
goto end;
}
out->p.mpi[0] = 0x40;
out->p.len++;
} else {
out->p.len = sizeof(out->p.mpi);
if (botan_pk_op_key_agreement_export_public(eph_prv_key, out->p.mpi, &out->p.len)) {
goto end;
}
}
// All OK
ret = RNP_SUCCESS;
end:
botan_privkey_destroy(eph_prv_key);
return ret;
}
rnp_result_t
ecdh_decrypt_pkcs5(uint8_t * out,
size_t * out_len,
const pgp_ecdh_encrypted_t *in,
const pgp_ec_key_t * key,
const pgp_fingerprint_t & fingerprint)
{
if (!out_len || !in || !key || !mpi_bytes(&key->x)) {
return RNP_ERROR_BAD_PARAMETERS;
}
const ec_curve_desc_t *curve_desc = get_curve_desc(key->curve);
if (!curve_desc) {
RNP_LOG("unknown curve");
return RNP_ERROR_NOT_SUPPORTED;
}
const pgp_symm_alg_t wrap_alg = key->key_wrap_alg;
const pgp_hash_alg_t kdf_hash = key->kdf_hash_alg;
/* Ensure that AES is used for wrapping */
if ((wrap_alg != PGP_SA_AES_128) && (wrap_alg != PGP_SA_AES_192) &&
(wrap_alg != PGP_SA_AES_256)) {
RNP_LOG("non-aes wrap algorithm");
return RNP_ERROR_NOT_SUPPORTED;
}
// See 13.5 of RFC 4880 for definition of other_info_size
uint8_t other_info[MAX_SP800_56A_OTHER_INFO];
const size_t other_info_size = curve_desc->OIDhex_len + 46;
const size_t tmp_len =
kdf_other_info_serialize(other_info, curve_desc, fingerprint, kdf_hash, wrap_alg);
if (other_info_size != tmp_len) {
RNP_LOG("Serialization of other info failed");
return RNP_ERROR_GENERIC;
}
botan_privkey_t prv_key = NULL;
if (!ecdh_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;
rnp::secure_array<uint8_t, MAX_SESSION_KEY_SIZE> deckey;
size_t deckey_len = deckey.size();
size_t offset = 0;
rnp_result_t ret = RNP_ERROR_GENERIC;
/* 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,
other_info_size,
curve_desc,
&in->p,
prv_key,
kdf_hash)) {
goto end;
}
#if defined(CRYPTO_BACKEND_BOTAN3)
char name[8];
snprintf(name, sizeof(name), "AES-%zu", 8 * kek_len);
if (botan_nist_kw_dec(
name, 0, in->m, in->mlen, kek.data(), kek_len, deckey.data(), &deckey_len)) {
#else
if (botan_key_unwrap3394(
in->m, in->mlen, kek.data(), kek_len, deckey.data(), &deckey_len)) {
#endif
goto end;
}
if (!unpad_pkcs7(deckey.data(), deckey_len, &offset)) {
goto end;
}
if (*out_len < offset) {
ret = RNP_ERROR_SHORT_BUFFER;
goto end;
}
*out_len = offset;
memcpy(out, deckey.data(), *out_len);
ret = RNP_SUCCESS;
end:
botan_privkey_destroy(prv_key);
return ret;
}