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qemu/crypto/akcipher-nettle.c.inc
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Jamin Lin f1846a5c6c crypto/akcipher: Support ECDSA sign/verify with nettle 
Implement ECDSA signing and verification for the nettle/hogweed backend,
for the prime256v1 (NIST P-256) and secp384r1 (NIST P-384) curves.
A public key (Qx || Qy) is loaded into an ecc_point for verify;
a private key (the scalar d) into an ecc_scalar for sign,
using nettle's ecdsa_sign() / ecdsa_verify().

The encrypt/decrypt driver ops return an error.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20260901085238.995968-4-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
2026-09-05 07:05:11 +02:00

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/*
* QEMU Crypto akcipher algorithms
*
* Copyright (c) 2022 Bytedance
* Author: lei he <helei.sig11@bytedance.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
*/
#include <nettle/rsa.h>
#include <nettle/ecdsa.h>
#include <nettle/ecc-curve.h>
#include <nettle/ecc.h>
#include <nettle/bignum.h>
#include "qemu/osdep.h"
#include "qemu/host-utils.h"
#include "crypto/akcipher.h"
#include "crypto/random.h"
#include "qapi/error.h"
#include "system/cryptodev.h"
#include "rsakey.h"
typedef struct QCryptoNettleRSA {
QCryptoAkCipher akcipher;
struct rsa_public_key pub;
struct rsa_private_key priv;
QCryptoRSAPaddingAlgo padding_alg;
QCryptoHashAlgo hash_alg;
} QCryptoNettleRSA;
static void qcrypto_nettle_rsa_free(QCryptoAkCipher *akcipher)
{
QCryptoNettleRSA *rsa = (QCryptoNettleRSA *)akcipher;
if (!rsa) {
return;
}
rsa_public_key_clear(&rsa->pub);
rsa_private_key_clear(&rsa->priv);
g_free(rsa);
}
static QCryptoAkCipher *qcrypto_nettle_rsa_new(
const QCryptoAkCipherOptionsRSA *opt,
QCryptoAkCipherKeyType type,
const uint8_t *key, size_t keylen,
Error **errp);
static QCryptoAkCipher *qcrypto_nettle_ecdsa_new(
const QCryptoAkCipherOptionsECDSA *opt,
QCryptoAkCipherKeyType type,
const uint8_t *key, size_t keylen,
Error **errp);
QCryptoAkCipher *qcrypto_akcipher_new(const QCryptoAkCipherOptions *opts,
QCryptoAkCipherKeyType type,
const uint8_t *key, size_t keylen,
Error **errp)
{
switch (opts->alg) {
case QCRYPTO_AK_CIPHER_ALGO_RSA:
return qcrypto_nettle_rsa_new(&opts->u.rsa, type, key, keylen, errp);
case QCRYPTO_AK_CIPHER_ALGO_ECDSA:
return qcrypto_nettle_ecdsa_new(&opts->u.ecdsa, type, key, keylen,
errp);
default:
error_setg(errp, "Unsupported algorithm: %u", opts->alg);
return NULL;
}
return NULL;
}
static void qcrypto_nettle_rsa_set_akcipher_size(QCryptoAkCipher *akcipher,
int key_size)
{
akcipher->max_plaintext_len = key_size;
akcipher->max_ciphertext_len = key_size;
akcipher->max_signature_len = key_size;
akcipher->max_dgst_len = key_size;
}
static int qcrypt_nettle_parse_rsa_private_key(QCryptoNettleRSA *rsa,
const uint8_t *key,
size_t keylen,
Error **errp)
{
g_autoptr(QCryptoAkCipherRSAKey) rsa_key = qcrypto_akcipher_rsakey_parse(
QCRYPTO_AK_CIPHER_KEY_TYPE_PRIVATE, key, keylen, errp);
if (!rsa_key) {
return -1;
}
nettle_mpz_init_set_str_256_u(rsa->pub.n, rsa_key->n.len, rsa_key->n.data);
nettle_mpz_init_set_str_256_u(rsa->pub.e, rsa_key->e.len, rsa_key->e.data);
nettle_mpz_init_set_str_256_u(rsa->priv.d, rsa_key->d.len, rsa_key->d.data);
nettle_mpz_init_set_str_256_u(rsa->priv.p, rsa_key->p.len, rsa_key->p.data);
nettle_mpz_init_set_str_256_u(rsa->priv.q, rsa_key->q.len, rsa_key->q.data);
nettle_mpz_init_set_str_256_u(rsa->priv.a, rsa_key->dp.len,
rsa_key->dp.data);
nettle_mpz_init_set_str_256_u(rsa->priv.b, rsa_key->dq.len,
rsa_key->dq.data);
nettle_mpz_init_set_str_256_u(rsa->priv.c, rsa_key->u.len, rsa_key->u.data);
if (!rsa_public_key_prepare(&rsa->pub)) {
error_setg(errp, "Failed to check RSA key");
return -1;
}
/**
* Since in the kernel's unit test, the p, q, a, b, c of some
* private keys is 0, only the simplest length check is done here
*/
if (rsa_key->p.len > 1 &&
rsa_key->q.len > 1 &&
rsa_key->dp.len > 1 &&
rsa_key->dq.len > 1 &&
rsa_key->u.len > 1) {
if (!rsa_private_key_prepare(&rsa->priv)) {
error_setg(errp, "Failed to check RSA key");
return -1;
}
} else {
rsa->priv.size = rsa->pub.size;
}
qcrypto_nettle_rsa_set_akcipher_size(
(QCryptoAkCipher *)rsa, rsa->priv.size);
return 0;
}
static int qcrypt_nettle_parse_rsa_public_key(QCryptoNettleRSA *rsa,
const uint8_t *key,
size_t keylen,
Error **errp)
{
g_autoptr(QCryptoAkCipherRSAKey) rsa_key = qcrypto_akcipher_rsakey_parse(
QCRYPTO_AK_CIPHER_KEY_TYPE_PUBLIC, key, keylen, errp);
if (!rsa_key) {
return -1;
}
nettle_mpz_init_set_str_256_u(rsa->pub.n, rsa_key->n.len, rsa_key->n.data);
nettle_mpz_init_set_str_256_u(rsa->pub.e, rsa_key->e.len, rsa_key->e.data);
if (!rsa_public_key_prepare(&rsa->pub)) {
error_setg(errp, "Failed to check RSA key");
return -1;
}
qcrypto_nettle_rsa_set_akcipher_size(
(QCryptoAkCipher *)rsa, rsa->pub.size);
return 0;
}
static void wrap_nettle_random_func(void *ctx, size_t len, uint8_t *out)
{
qcrypto_random_bytes(out, len, &error_abort);
}
static int qcrypto_nettle_rsa_encrypt(QCryptoAkCipher *akcipher,
const void *data, size_t data_len,
void *enc, size_t enc_len,
Error **errp)
{
QCryptoNettleRSA *rsa = (QCryptoNettleRSA *)akcipher;
mpz_t c;
int ret = -1;
if (data_len > rsa->pub.size) {
error_setg(errp, "Plaintext length %zu is greater than key size: %zu",
data_len, rsa->pub.size);
return ret;
}
if (enc_len < rsa->pub.size) {
error_setg(errp, "Ciphertext buffer length %zu is less than "
"key size: %zu", enc_len, rsa->pub.size);
return ret;
}
/* Nettle do not support RSA encryption without any padding */
switch (rsa->padding_alg) {
case QCRYPTO_RSA_PADDING_ALGO_RAW:
error_setg(errp, "RSA with raw padding is not supported");
break;
case QCRYPTO_RSA_PADDING_ALGO_PKCS1:
mpz_init(c);
if (rsa_encrypt(&rsa->pub, NULL, wrap_nettle_random_func,
data_len, (uint8_t *)data, c) != 1) {
error_setg(errp, "Failed to encrypt");
} else {
nettle_mpz_get_str_256(enc_len, (uint8_t *)enc, c);
ret = nettle_mpz_sizeinbase_256_u(c);
}
mpz_clear(c);
break;
default:
error_setg(errp, "Unknown padding");
}
return ret;
}
static int qcrypto_nettle_rsa_decrypt(QCryptoAkCipher *akcipher,
const void *enc, size_t enc_len,
void *data, size_t data_len,
Error **errp)
{
QCryptoNettleRSA *rsa = (QCryptoNettleRSA *)akcipher;
mpz_t c;
int ret = -1;
if (enc_len > rsa->priv.size) {
error_setg(errp, "Ciphertext length %zu is greater than key size: %zu",
enc_len, rsa->priv.size);
return ret;
}
switch (rsa->padding_alg) {
case QCRYPTO_RSA_PADDING_ALGO_RAW:
error_setg(errp, "RSA with raw padding is not supported");
break;
case QCRYPTO_RSA_PADDING_ALGO_PKCS1:
nettle_mpz_init_set_str_256_u(c, enc_len, enc);
if (!rsa_decrypt(&rsa->priv, &data_len, (uint8_t *)data, c)) {
error_setg(errp, "Failed to decrypt");
} else {
ret = data_len;
}
mpz_clear(c);
break;
default:
error_setg(errp, "Unknown padding algorithm: %d", rsa->padding_alg);
}
return ret;
}
static int qcrypto_nettle_rsa_sign(QCryptoAkCipher *akcipher,
const void *data, size_t data_len,
void *sig, size_t sig_len, Error **errp)
{
QCryptoNettleRSA *rsa = (QCryptoNettleRSA *)akcipher;
int ret = -1, rv;
mpz_t s;
/**
* The RSA algorithm cannot be used for signature/verification
* without padding.
*/
if (rsa->padding_alg == QCRYPTO_RSA_PADDING_ALGO_RAW) {
error_setg(errp, "Try to make signature without padding");
return ret;
}
if (data_len > rsa->priv.size) {
error_setg(errp, "Data length %zu is greater than key size: %zu",
data_len, rsa->priv.size);
return ret;
}
if (sig_len < rsa->priv.size) {
error_setg(errp, "Signature buffer length %zu is less than "
"key size: %zu", sig_len, rsa->priv.size);
return ret;
}
mpz_init(s);
switch (rsa->hash_alg) {
case QCRYPTO_HASH_ALGO_MD5:
rv = rsa_md5_sign_digest(&rsa->priv, data, s);
break;
case QCRYPTO_HASH_ALGO_SHA1:
rv = rsa_sha1_sign_digest(&rsa->priv, data, s);
break;
case QCRYPTO_HASH_ALGO_SHA256:
rv = rsa_sha256_sign_digest(&rsa->priv, data, s);
break;
case QCRYPTO_HASH_ALGO_SHA512:
rv = rsa_sha512_sign_digest(&rsa->priv, data, s);
break;
default:
error_setg(errp, "Unknown hash algorithm: %d", rsa->hash_alg);
goto cleanup;
}
if (rv != 1) {
error_setg(errp, "Failed to make signature");
goto cleanup;
}
nettle_mpz_get_str_256(sig_len, (uint8_t *)sig, s);
ret = nettle_mpz_sizeinbase_256_u(s);
cleanup:
mpz_clear(s);
return ret;
}
static int qcrypto_nettle_rsa_verify(QCryptoAkCipher *akcipher,
const void *sig, size_t sig_len,
const void *data, size_t data_len,
Error **errp)
{
QCryptoNettleRSA *rsa = (QCryptoNettleRSA *)akcipher;
int ret = -1, rv;
mpz_t s;
/**
* The RSA algorithm cannot be used for signature/verification
* without padding.
*/
if (rsa->padding_alg == QCRYPTO_RSA_PADDING_ALGO_RAW) {
error_setg(errp, "Try to verify signature without padding");
return ret;
}
if (data_len > rsa->pub.size) {
error_setg(errp, "Data length %zu is greater than key size: %zu",
data_len, rsa->pub.size);
return ret;
}
if (sig_len < rsa->pub.size) {
error_setg(errp, "Signature length %zu is greater than key size: %zu",
sig_len, rsa->pub.size);
return ret;
}
nettle_mpz_init_set_str_256_u(s, sig_len, sig);
switch (rsa->hash_alg) {
case QCRYPTO_HASH_ALGO_MD5:
rv = rsa_md5_verify_digest(&rsa->pub, data, s);
break;
case QCRYPTO_HASH_ALGO_SHA1:
rv = rsa_sha1_verify_digest(&rsa->pub, data, s);
break;
case QCRYPTO_HASH_ALGO_SHA256:
rv = rsa_sha256_verify_digest(&rsa->pub, data, s);
break;
case QCRYPTO_HASH_ALGO_SHA512:
rv = rsa_sha512_verify_digest(&rsa->pub, data, s);
break;
default:
error_setg(errp, "Unsupported hash algorithm: %d", rsa->hash_alg);
goto cleanup;
}
if (rv != 1) {
error_setg(errp, "Failed to verify signature");
goto cleanup;
}
ret = 0;
cleanup:
mpz_clear(s);
return ret;
}
QCryptoAkCipherDriver nettle_rsa = {
.encrypt = qcrypto_nettle_rsa_encrypt,
.decrypt = qcrypto_nettle_rsa_decrypt,
.sign = qcrypto_nettle_rsa_sign,
.verify = qcrypto_nettle_rsa_verify,
.free = qcrypto_nettle_rsa_free,
};
static QCryptoAkCipher *qcrypto_nettle_rsa_new(
const QCryptoAkCipherOptionsRSA *opt,
QCryptoAkCipherKeyType type,
const uint8_t *key, size_t keylen,
Error **errp)
{
QCryptoNettleRSA *rsa = g_new0(QCryptoNettleRSA, 1);
rsa->padding_alg = opt->padding_alg;
rsa->hash_alg = opt->hash_alg;
rsa->akcipher.driver = &nettle_rsa;
rsa_public_key_init(&rsa->pub);
rsa_private_key_init(&rsa->priv);
switch (type) {
case QCRYPTO_AK_CIPHER_KEY_TYPE_PRIVATE:
if (qcrypt_nettle_parse_rsa_private_key(rsa, key, keylen, errp) != 0) {
goto error;
}
break;
case QCRYPTO_AK_CIPHER_KEY_TYPE_PUBLIC:
if (qcrypt_nettle_parse_rsa_public_key(rsa, key, keylen, errp) != 0) {
goto error;
}
break;
default:
error_setg(errp, "Unknown akcipher key type %d", type);
goto error;
}
return (QCryptoAkCipher *)rsa;
error:
qcrypto_nettle_rsa_free((QCryptoAkCipher *)rsa);
return NULL;
}
/*
* ECDSA support (sign and verify)
*
* Keys and signatures use raw big-endian formats:
* - public key: Qx || Qy, each 'coord_len' bytes
* - private key: the scalar d, 'coord_len' bytes
* - signature: r || s, each 'coord_len' bytes
* - the input to sign/verify is a raw message digest
*/
typedef struct QCryptoNettleECDSA {
QCryptoAkCipher akcipher;
QCryptoAkCipherKeyType type;
struct ecc_point pub;
struct ecc_scalar priv;
QCryptoCurveID curve_id;
} QCryptoNettleECDSA;
static const struct ecc_curve *qcrypto_nettle_ecdsa_curve(
QCryptoCurveID curve_id)
{
switch (curve_id) {
case QCRYPTO_CURVE_ID_PRIME256V1:
return nettle_get_secp_256r1();
case QCRYPTO_CURVE_ID_SECP384R1:
return nettle_get_secp_384r1();
default:
return NULL;
}
}
static size_t qcrypto_nettle_ecdsa_coord_len(QCryptoCurveID curve_id)
{
switch (curve_id) {
case QCRYPTO_CURVE_ID_PRIME256V1:
return 32;
case QCRYPTO_CURVE_ID_SECP384R1:
return 48;
default:
return 0;
}
}
static void qcrypto_nettle_ecdsa_free(QCryptoAkCipher *akcipher)
{
QCryptoNettleECDSA *ecdsa = (QCryptoNettleECDSA *)akcipher;
if (!ecdsa) {
return;
}
if (ecdsa->type == QCRYPTO_AK_CIPHER_KEY_TYPE_PRIVATE) {
ecc_scalar_clear(&ecdsa->priv);
} else {
ecc_point_clear(&ecdsa->pub);
}
g_free(ecdsa);
}
static int qcrypto_nettle_ecdsa_encrypt(QCryptoAkCipher *akcipher,
const void *in, size_t in_len,
void *out, size_t out_len,
Error **errp)
{
error_setg(errp, "ECDSA does not support encryption");
return -1;
}
static int qcrypto_nettle_ecdsa_decrypt(QCryptoAkCipher *akcipher,
const void *in, size_t in_len,
void *out, size_t out_len,
Error **errp)
{
error_setg(errp, "ECDSA does not support decryption");
return -1;
}
static int qcrypto_nettle_ecdsa_sign(QCryptoAkCipher *akcipher,
const void *in, size_t in_len,
void *out, size_t out_len,
Error **errp)
{
QCryptoNettleECDSA *ecdsa = (QCryptoNettleECDSA *)akcipher;
size_t coord_len = qcrypto_nettle_ecdsa_coord_len(ecdsa->curve_id);
struct dsa_signature sig;
if (ecdsa->type != QCRYPTO_AK_CIPHER_KEY_TYPE_PRIVATE) {
error_setg(errp, "ECDSA sign requires a private key");
return -1;
}
if (in_len == 0 || in_len > akcipher->max_dgst_len) {
error_setg(errp, "Invalid digest length %zu", in_len);
return -1;
}
if (out_len < coord_len * 2) {
error_setg(errp, "Signature buffer length %zu is less than %zu",
out_len, coord_len * 2);
return -1;
}
dsa_signature_init(&sig);
ecdsa_sign(&ecdsa->priv, NULL, wrap_nettle_random_func, in_len, in, &sig);
/* output is r || s, each zero-padded to the curve size */
nettle_mpz_get_str_256(coord_len, out, sig.r);
nettle_mpz_get_str_256(coord_len, (uint8_t *)out + coord_len, sig.s);
dsa_signature_clear(&sig);
return coord_len * 2;
}
static int qcrypto_nettle_ecdsa_verify(QCryptoAkCipher *akcipher,
const void *in, size_t in_len,
const void *in2, size_t in2_len,
Error **errp)
{
QCryptoNettleECDSA *ecdsa = (QCryptoNettleECDSA *)akcipher;
size_t coord_len = qcrypto_nettle_ecdsa_coord_len(ecdsa->curve_id);
struct dsa_signature sig;
int ret = -1;
if (ecdsa->type != QCRYPTO_AK_CIPHER_KEY_TYPE_PUBLIC) {
error_setg(errp, "ECDSA verify requires a public key");
return ret;
}
/* signature is r || s */
if (in_len != coord_len * 2) {
error_setg(errp, "Signature length %zu is not %zu",
in_len, coord_len * 2);
return ret;
}
if (in2_len == 0 || in2_len > akcipher->max_dgst_len) {
error_setg(errp, "Invalid digest length %zu", in2_len);
return ret;
}
dsa_signature_init(&sig);
nettle_mpz_set_str_256_u(sig.r, coord_len, in);
nettle_mpz_set_str_256_u(sig.s, coord_len, (const uint8_t *)in + coord_len);
if (ecdsa_verify(&ecdsa->pub, in2_len, in2, &sig) == 1) {
ret = 0;
} else {
error_setg(errp, "Failed to verify signature");
}
dsa_signature_clear(&sig);
return ret;
}
QCryptoAkCipherDriver nettle_ecdsa = {
.encrypt = qcrypto_nettle_ecdsa_encrypt,
.decrypt = qcrypto_nettle_ecdsa_decrypt,
.sign = qcrypto_nettle_ecdsa_sign,
.verify = qcrypto_nettle_ecdsa_verify,
.free = qcrypto_nettle_ecdsa_free,
};
static QCryptoAkCipher *qcrypto_nettle_ecdsa_new(
const QCryptoAkCipherOptionsECDSA *opt,
QCryptoAkCipherKeyType type,
const uint8_t *key, size_t keylen,
Error **errp)
{
QCryptoNettleECDSA *ecdsa;
const struct ecc_curve *curve = qcrypto_nettle_ecdsa_curve(opt->curve_id);
size_t coord_len = qcrypto_nettle_ecdsa_coord_len(opt->curve_id);
mpz_t x;
mpz_t y;
if (!curve || coord_len == 0) {
error_setg(errp, "Unsupported curve id: %u", opt->curve_id);
return NULL;
}
switch (type) {
case QCRYPTO_AK_CIPHER_KEY_TYPE_PUBLIC:
if (keylen != coord_len * 2) {
error_setg(errp, "Public key length %zu is not %zu",
keylen, coord_len * 2);
return NULL;
}
break;
case QCRYPTO_AK_CIPHER_KEY_TYPE_PRIVATE:
if (keylen != coord_len) {
error_setg(errp, "Private key length %zu is not %zu",
keylen, coord_len);
return NULL;
}
break;
default:
error_setg(errp, "Unknown akcipher key type %d", type);
return NULL;
}
ecdsa = g_new0(QCryptoNettleECDSA, 1);
ecdsa->akcipher.driver = &nettle_ecdsa;
ecdsa->type = type;
ecdsa->curve_id = opt->curve_id;
ecdsa->akcipher.max_dgst_len = coord_len;
ecdsa->akcipher.max_signature_len = coord_len * 2;
if (type == QCRYPTO_AK_CIPHER_KEY_TYPE_PUBLIC) {
/* public key: Qx || Qy */
ecc_point_init(&ecdsa->pub, curve);
mpz_init(x);
mpz_init(y);
nettle_mpz_set_str_256_u(x, coord_len, key);
nettle_mpz_set_str_256_u(y, coord_len,
(const uint8_t *)key + coord_len);
if (!ecc_point_set(&ecdsa->pub, x, y)) {
error_setg(errp, "Invalid ECDSA public key (not on curve)");
mpz_clear(x);
mpz_clear(y);
qcrypto_nettle_ecdsa_free((QCryptoAkCipher *)ecdsa);
return NULL;
}
mpz_clear(x);
mpz_clear(y);
} else {
/* private key: the scalar d */
ecc_scalar_init(&ecdsa->priv, curve);
mpz_init(x);
nettle_mpz_set_str_256_u(x, coord_len, key);
if (!ecc_scalar_set(&ecdsa->priv, x)) {
error_setg(errp, "Invalid ECDSA private key");
mpz_clear(x);
qcrypto_nettle_ecdsa_free((QCryptoAkCipher *)ecdsa);
return NULL;
}
mpz_clear(x);
}
return (QCryptoAkCipher *)ecdsa;
}
bool qcrypto_akcipher_supports(QCryptoAkCipherOptions *opts)
{
switch (opts->alg) {
case QCRYPTO_AK_CIPHER_ALGO_RSA:
switch (opts->u.rsa.padding_alg) {
case QCRYPTO_RSA_PADDING_ALGO_PKCS1:
switch (opts->u.rsa.hash_alg) {
case QCRYPTO_HASH_ALGO_MD5:
case QCRYPTO_HASH_ALGO_SHA1:
case QCRYPTO_HASH_ALGO_SHA256:
case QCRYPTO_HASH_ALGO_SHA512:
return true;
default:
return false;
}
case QCRYPTO_RSA_PADDING_ALGO_RAW:
default:
return false;
}
break;
case QCRYPTO_AK_CIPHER_ALGO_ECDSA:
switch (opts->u.ecdsa.curve_id) {
case QCRYPTO_CURVE_ID_PRIME256V1:
case QCRYPTO_CURVE_ID_SECP384R1:
return true;
default:
return false;
}
default:
return false;
}
}
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