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/*
* Copyright (c) 2018-2022 Yubico AB. All rights reserved.
* Use of this source code is governed by a BSD-style
* license that can be found in the LICENSE file.
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/obj_mac.h>
#include "fido.h"
#include "fido/rs256.h"
#if OPENSSL_VERSION_NUMBER >= 0x30000000
#define get0_RSA(x) EVP_PKEY_get0_RSA((x))
#else
#define get0_RSA(x) EVP_PKEY_get0((x))
#endif
#if defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x3050200fL
static EVP_MD *
rs256_get_EVP_MD(void)
{
const EVP_MD *from;
EVP_MD *to = NULL;
if ((from = EVP_sha256()) != NULL && (to = malloc(sizeof(*to))) != NULL)
memcpy(to, from, sizeof(*to));
return (to);
}
static void
rs256_free_EVP_MD(EVP_MD *md)
{
freezero(md, sizeof(*md));
}
#elif OPENSSL_VERSION_NUMBER >= 0x30000000
static EVP_MD *
rs256_get_EVP_MD(void)
{
return (EVP_MD_fetch(NULL, "SHA2-256", NULL));
}
static void
rs256_free_EVP_MD(EVP_MD *md)
{
EVP_MD_free(md);
}
#else
static EVP_MD *
rs256_get_EVP_MD(void)
{
const EVP_MD *md;
if ((md = EVP_sha256()) == NULL)
return (NULL);
return (EVP_MD_meth_dup(md));
}
static void
rs256_free_EVP_MD(EVP_MD *md)
{
EVP_MD_meth_free(md);
}
#endif /* LIBRESSL_VERSION_NUMBER */
static int
decode_bignum(const cbor_item_t *item, void *ptr, size_t len)
{
if (cbor_isa_bytestring(item) == false ||
cbor_bytestring_is_definite(item) == false ||
cbor_bytestring_length(item) != len) {
fido_log_debug("%s: cbor type", __func__);
return (-1);
}
memcpy(ptr, cbor_bytestring_handle(item), len);
return (0);
}
static int
decode_rsa_pubkey(const cbor_item_t *key, const cbor_item_t *val, void *arg)
{
rs256_pk_t *k = arg;
if (cbor_isa_negint(key) == false ||
cbor_int_get_width(key) != CBOR_INT_8)
return (0); /* ignore */
switch (cbor_get_uint8(key)) {
case 0: /* modulus */
return (decode_bignum(val, &k->n, sizeof(k->n)));
case 1: /* public exponent */
return (decode_bignum(val, &k->e, sizeof(k->e)));
}
return (0); /* ignore */
}
int
rs256_pk_decode(const cbor_item_t *item, rs256_pk_t *k)
{
if (cbor_isa_map(item) == false ||
cbor_map_is_definite(item) == false ||
cbor_map_iter(item, k, decode_rsa_pubkey) < 0) {
fido_log_debug("%s: cbor type", __func__);
return (-1);
}
return (0);
}
rs256_pk_t *
rs256_pk_new(void)
{
return (calloc(1, sizeof(rs256_pk_t)));
}
void
rs256_pk_free(rs256_pk_t **pkp)
{
rs256_pk_t *pk;
if (pkp == NULL || (pk = *pkp) == NULL)
return;
freezero(pk, sizeof(*pk));
*pkp = NULL;
}
int
rs256_pk_from_ptr(rs256_pk_t *pk, const void *ptr, size_t len)
{
EVP_PKEY *pkey;
if (len < sizeof(*pk))
return (FIDO_ERR_INVALID_ARGUMENT);
memcpy(pk, ptr, sizeof(*pk));
if ((pkey = rs256_pk_to_EVP_PKEY(pk)) == NULL) {
fido_log_debug("%s: rs256_pk_to_EVP_PKEY", __func__);
return (FIDO_ERR_INVALID_ARGUMENT);
}
EVP_PKEY_free(pkey);
return (FIDO_OK);
}
EVP_PKEY *
rs256_pk_to_EVP_PKEY(const rs256_pk_t *k)
{
RSA *rsa = NULL;
EVP_PKEY *pkey = NULL;
BIGNUM *n = NULL;
BIGNUM *e = NULL;
int ok = -1;
if ((n = BN_new()) == NULL || (e = BN_new()) == NULL)
goto fail;
if (BN_bin2bn(k->n, sizeof(k->n), n) == NULL ||
BN_bin2bn(k->e, sizeof(k->e), e) == NULL) {
fido_log_debug("%s: BN_bin2bn", __func__);
goto fail;
}
if ((rsa = RSA_new()) == NULL || RSA_set0_key(rsa, n, e, NULL) == 0) {
fido_log_debug("%s: RSA_set0_key", __func__);
goto fail;
}
/* at this point, n and e belong to rsa */
n = NULL;
e = NULL;
if (RSA_bits(rsa) != 2048) {
fido_log_debug("%s: invalid key length", __func__);
goto fail;
}
if ((pkey = EVP_PKEY_new()) == NULL ||
EVP_PKEY_assign_RSA(pkey, rsa) == 0) {
fido_log_debug("%s: EVP_PKEY_assign_RSA", __func__);
goto fail;
}
rsa = NULL; /* at this point, rsa belongs to evp */
ok = 0;
fail:
if (n != NULL)
BN_free(n);
if (e != NULL)
BN_free(e);
if (rsa != NULL)
RSA_free(rsa);
if (ok < 0 && pkey != NULL) {
EVP_PKEY_free(pkey);
pkey = NULL;
}
return (pkey);
}
int
rs256_pk_from_RSA(rs256_pk_t *pk, const RSA *rsa)
{
const BIGNUM *n = NULL;
const BIGNUM *e = NULL;
const BIGNUM *d = NULL;
int k;
if (RSA_bits(rsa) != 2048) {
fido_log_debug("%s: invalid key length", __func__);
return (FIDO_ERR_INVALID_ARGUMENT);
}
RSA_get0_key(rsa, &n, &e, &d);
if (n == NULL || e == NULL) {
fido_log_debug("%s: RSA_get0_key", __func__);
return (FIDO_ERR_INTERNAL);
}
if ((k = BN_num_bytes(n)) < 0 || (size_t)k > sizeof(pk->n) ||
(k = BN_num_bytes(e)) < 0 || (size_t)k > sizeof(pk->e)) {
fido_log_debug("%s: invalid key", __func__);
return (FIDO_ERR_INTERNAL);
}
if ((k = BN_bn2bin(n, pk->n)) < 0 || (size_t)k > sizeof(pk->n) ||
(k = BN_bn2bin(e, pk->e)) < 0 || (size_t)k > sizeof(pk->e)) {
fido_log_debug("%s: BN_bn2bin", __func__);
return (FIDO_ERR_INTERNAL);
}
return (FIDO_OK);
}
int
rs256_pk_from_EVP_PKEY(rs256_pk_t *pk, const EVP_PKEY *pkey)
{
const RSA *rsa;
if (EVP_PKEY_base_id(pkey) != EVP_PKEY_RSA ||
(rsa = get0_RSA(pkey)) == NULL)
return (FIDO_ERR_INVALID_ARGUMENT);
return (rs256_pk_from_RSA(pk, rsa));
}
int
rs256_verify_sig(const fido_blob_t *dgst, EVP_PKEY *pkey,
const fido_blob_t *sig)
{
EVP_PKEY_CTX *pctx = NULL;
EVP_MD *md = NULL;
int ok = -1;
if (EVP_PKEY_base_id(pkey) != EVP_PKEY_RSA) {
fido_log_debug("%s: EVP_PKEY_base_id", __func__);
goto fail;
}
if ((md = rs256_get_EVP_MD()) == NULL) {
fido_log_debug("%s: rs256_get_EVP_MD", __func__);
goto fail;
}
if ((pctx = EVP_PKEY_CTX_new(pkey, NULL)) == NULL ||
EVP_PKEY_verify_init(pctx) != 1 ||
EVP_PKEY_CTX_set_rsa_padding(pctx, RSA_PKCS1_PADDING) != 1 ||
EVP_PKEY_CTX_set_signature_md(pctx, md) != 1) {
fido_log_debug("%s: EVP_PKEY_CTX", __func__);
goto fail;
}
if (EVP_PKEY_verify(pctx, sig->ptr, sig->len, dgst->ptr,
dgst->len) != 1) {
fido_log_debug("%s: EVP_PKEY_verify", __func__);
goto fail;
}
ok = 0;
fail:
EVP_PKEY_CTX_free(pctx);
rs256_free_EVP_MD(md);
return (ok);
}
int
rs256_pk_verify_sig(const fido_blob_t *dgst, const rs256_pk_t *pk,
const fido_blob_t *sig)
{
EVP_PKEY *pkey;
int ok = -1;
if ((pkey = rs256_pk_to_EVP_PKEY(pk)) == NULL ||
rs256_verify_sig(dgst, pkey, sig) < 0) {
fido_log_debug("%s: rs256_verify_sig", __func__);
goto fail;
}
ok = 0;
fail:
EVP_PKEY_free(pkey);
return (ok);
}
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