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linux-sg2042/crypto/sm2.c

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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* SM2 asymmetric public-key algorithm
* as specified by OSCCA GM/T 0003.1-2012 -- 0003.5-2012 SM2 and
* described at https://tools.ietf.org/html/draft-shen-sm2-ecdsa-02
*
* Copyright (c) 2020, Alibaba Group.
* Authors: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
*/
#include <linux/module.h>
#include <linux/mpi.h>
#include <crypto/internal/akcipher.h>
#include <crypto/akcipher.h>
#include <crypto/hash.h>
#include <crypto/sm3_base.h>
#include <crypto/rng.h>
#include <crypto/sm2.h>
#include "sm2signature.asn1.h"
#define MPI_NBYTES(m) ((mpi_get_nbits(m) + 7) / 8)
struct ecc_domain_parms {
const char *desc; /* Description of the curve. */
unsigned int nbits; /* Number of bits. */
unsigned int fips:1; /* True if this is a FIPS140-2 approved curve */
/* The model describing this curve. This is mainly used to select
* the group equation.
*/
enum gcry_mpi_ec_models model;
/* The actual ECC dialect used. This is used for curve specific
* optimizations and to select encodings etc.
*/
enum ecc_dialects dialect;
const char *p; /* The prime defining the field. */
const char *a, *b; /* The coefficients. For Twisted Edwards
* Curves b is used for d. For Montgomery
* Curves (a,b) has ((A-2)/4,B^-1).
*/
const char *n; /* The order of the base point. */
const char *g_x, *g_y; /* Base point. */
unsigned int h; /* Cofactor. */
};
static const struct ecc_domain_parms sm2_ecp = {
.desc = "sm2p256v1",
.nbits = 256,
.fips = 0,
.model = MPI_EC_WEIERSTRASS,
.dialect = ECC_DIALECT_STANDARD,
.p = "0xfffffffeffffffffffffffffffffffffffffffff00000000ffffffffffffffff",
.a = "0xfffffffeffffffffffffffffffffffffffffffff00000000fffffffffffffffc",
.b = "0x28e9fa9e9d9f5e344d5a9e4bcf6509a7f39789f515ab8f92ddbcbd414d940e93",
.n = "0xfffffffeffffffffffffffffffffffff7203df6b21c6052b53bbf40939d54123",
.g_x = "0x32c4ae2c1f1981195f9904466a39c9948fe30bbff2660be1715a4589334c74c7",
.g_y = "0xbc3736a2f4f6779c59bdcee36b692153d0a9877cc62a474002df32e52139f0a0",
.h = 1
};
static int sm2_ec_ctx_init(struct mpi_ec_ctx *ec)
{
const struct ecc_domain_parms *ecp = &sm2_ecp;
MPI p, a, b;
MPI x, y;
int rc = -EINVAL;
p = mpi_scanval(ecp->p);
a = mpi_scanval(ecp->a);
b = mpi_scanval(ecp->b);
if (!p || !a || !b)
goto free_p;
x = mpi_scanval(ecp->g_x);
y = mpi_scanval(ecp->g_y);
if (!x || !y)
goto free;
rc = -ENOMEM;
/* mpi_ec_setup_elliptic_curve */
ec->G = mpi_point_new(0);
if (!ec->G)
goto free;
mpi_set(ec->G->x, x);
mpi_set(ec->G->y, y);
mpi_set_ui(ec->G->z, 1);
rc = -EINVAL;
ec->n = mpi_scanval(ecp->n);
if (!ec->n) {
mpi_point_release(ec->G);
goto free;
}
ec->h = ecp->h;
ec->name = ecp->desc;
mpi_ec_init(ec, ecp->model, ecp->dialect, 0, p, a, b);
rc = 0;
free:
mpi_free(x);
mpi_free(y);
free_p:
mpi_free(p);
mpi_free(a);
mpi_free(b);
return rc;
}
static void sm2_ec_ctx_deinit(struct mpi_ec_ctx *ec)
{
mpi_ec_deinit(ec);
memset(ec, 0, sizeof(*ec));
}
/* RESULT must have been initialized and is set on success to the
* point given by VALUE.
*/
static int sm2_ecc_os2ec(MPI_POINT result, MPI value)
{
int rc;
size_t n;
unsigned char *buf;
MPI x, y;
n = MPI_NBYTES(value);
buf = kmalloc(n, GFP_KERNEL);
if (!buf)
return -ENOMEM;
rc = mpi_print(GCRYMPI_FMT_USG, buf, n, &n, value);
if (rc)
goto err_freebuf;
rc = -EINVAL;
if (n < 1 || ((n - 1) % 2))
goto err_freebuf;
/* No support for point compression */
if (*buf != 0x4)
goto err_freebuf;
rc = -ENOMEM;
n = (n - 1) / 2;
x = mpi_read_raw_data(buf + 1, n);
if (!x)
goto err_freebuf;
y = mpi_read_raw_data(buf + 1 + n, n);
if (!y)
goto err_freex;
mpi_normalize(x);
mpi_normalize(y);
mpi_set(result->x, x);
mpi_set(result->y, y);
mpi_set_ui(result->z, 1);
rc = 0;
mpi_free(y);
err_freex:
mpi_free(x);
err_freebuf:
kfree(buf);
return rc;
}
struct sm2_signature_ctx {
MPI sig_r;
MPI sig_s;
};
int sm2_get_signature_r(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct sm2_signature_ctx *sig = context;
if (!value || !vlen)
return -EINVAL;
sig->sig_r = mpi_read_raw_data(value, vlen);
if (!sig->sig_r)
return -ENOMEM;
return 0;
}
int sm2_get_signature_s(void *context, size_t hdrlen, unsigned char tag,
const void *value, size_t vlen)
{
struct sm2_signature_ctx *sig = context;
if (!value || !vlen)
return -EINVAL;
sig->sig_s = mpi_read_raw_data(value, vlen);
if (!sig->sig_s)
return -ENOMEM;
return 0;
}
static int sm2_z_digest_update(struct shash_desc *desc,
MPI m, unsigned int pbytes)
{
static const unsigned char zero[32];
unsigned char *in;
unsigned int inlen;
in = mpi_get_buffer(m, &inlen, NULL);
if (!in)
return -EINVAL;
if (inlen < pbytes) {
/* padding with zero */
crypto_sm3_update(desc, zero, pbytes - inlen);
crypto_sm3_update(desc, in, inlen);
} else if (inlen > pbytes) {
/* skip the starting zero */
crypto_sm3_update(desc, in + inlen - pbytes, pbytes);
} else {
crypto_sm3_update(desc, in, inlen);
}
kfree(in);
return 0;
}
static int sm2_z_digest_update_point(struct shash_desc *desc,
MPI_POINT point, struct mpi_ec_ctx *ec, unsigned int pbytes)
{
MPI x, y;
int ret = -EINVAL;
x = mpi_new(0);
y = mpi_new(0);
if (!mpi_ec_get_affine(x, y, point, ec) &&
!sm2_z_digest_update(desc, x, pbytes) &&
!sm2_z_digest_update(desc, y, pbytes))
ret = 0;
mpi_free(x);
mpi_free(y);
return ret;
}
int sm2_compute_z_digest(struct crypto_akcipher *tfm,
const unsigned char *id, size_t id_len,
unsigned char dgst[SM3_DIGEST_SIZE])
{
struct mpi_ec_ctx *ec = akcipher_tfm_ctx(tfm);
uint16_t bits_len;
unsigned char entl[2];
SHASH_DESC_ON_STACK(desc, NULL);
unsigned int pbytes;
if (id_len > (USHRT_MAX / 8) || !ec->Q)
return -EINVAL;
bits_len = (uint16_t)(id_len * 8);
entl[0] = bits_len >> 8;
entl[1] = bits_len & 0xff;
pbytes = MPI_NBYTES(ec->p);
/* ZA = H256(ENTLA | IDA | a | b | xG | yG | xA | yA) */
sm3_base_init(desc);
crypto_sm3_update(desc, entl, 2);
crypto_sm3_update(desc, id, id_len);
if (sm2_z_digest_update(desc, ec->a, pbytes) ||
sm2_z_digest_update(desc, ec->b, pbytes) ||
sm2_z_digest_update_point(desc, ec->G, ec, pbytes) ||
sm2_z_digest_update_point(desc, ec->Q, ec, pbytes))
return -EINVAL;
crypto_sm3_final(desc, dgst);
return 0;
}
EXPORT_SYMBOL(sm2_compute_z_digest);
static int _sm2_verify(struct mpi_ec_ctx *ec, MPI hash, MPI sig_r, MPI sig_s)
{
int rc = -EINVAL;
struct gcry_mpi_point sG, tP;
MPI t = NULL;
MPI x1 = NULL, y1 = NULL;
mpi_point_init(&sG);
mpi_point_init(&tP);
x1 = mpi_new(0);
y1 = mpi_new(0);
t = mpi_new(0);
/* r, s in [1, n-1] */
if (mpi_cmp_ui(sig_r, 1) < 0 || mpi_cmp(sig_r, ec->n) > 0 ||
mpi_cmp_ui(sig_s, 1) < 0 || mpi_cmp(sig_s, ec->n) > 0) {
goto leave;
}
/* t = (r + s) % n, t == 0 */
mpi_addm(t, sig_r, sig_s, ec->n);
if (mpi_cmp_ui(t, 0) == 0)
goto leave;
/* sG + tP = (x1, y1) */
rc = -EBADMSG;
mpi_ec_mul_point(&sG, sig_s, ec->G, ec);
mpi_ec_mul_point(&tP, t, ec->Q, ec);
mpi_ec_add_points(&sG, &sG, &tP, ec);
if (mpi_ec_get_affine(x1, y1, &sG, ec))
goto leave;
/* R = (e + x1) % n */
mpi_addm(t, hash, x1, ec->n);
/* check R == r */
rc = -EKEYREJECTED;
if (mpi_cmp(t, sig_r))
goto leave;
rc = 0;
leave:
mpi_point_free_parts(&sG);
mpi_point_free_parts(&tP);
mpi_free(x1);
mpi_free(y1);
mpi_free(t);
return rc;
}
static int sm2_verify(struct akcipher_request *req)
{
struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
struct mpi_ec_ctx *ec = akcipher_tfm_ctx(tfm);
unsigned char *buffer;
struct sm2_signature_ctx sig;
MPI hash;
int ret;
if (unlikely(!ec->Q))
return -EINVAL;
buffer = kmalloc(req->src_len + req->dst_len, GFP_KERNEL);
if (!buffer)
return -ENOMEM;
sg_pcopy_to_buffer(req->src,
sg_nents_for_len(req->src, req->src_len + req->dst_len),
buffer, req->src_len + req->dst_len, 0);
sig.sig_r = NULL;
sig.sig_s = NULL;
ret = asn1_ber_decoder(&sm2signature_decoder, &sig,
buffer, req->src_len);
if (ret)
goto error;
ret = -ENOMEM;
hash = mpi_read_raw_data(buffer + req->src_len, req->dst_len);
if (!hash)
goto error;
ret = _sm2_verify(ec, hash, sig.sig_r, sig.sig_s);
mpi_free(hash);
error:
mpi_free(sig.sig_r);
mpi_free(sig.sig_s);
kfree(buffer);
return ret;
}
static int sm2_set_pub_key(struct crypto_akcipher *tfm,
const void *key, unsigned int keylen)
{
struct mpi_ec_ctx *ec = akcipher_tfm_ctx(tfm);
MPI a;
int rc;
ec->Q = mpi_point_new(0);
if (!ec->Q)
return -ENOMEM;
/* include the uncompressed flag '0x04' */
rc = -ENOMEM;
a = mpi_read_raw_data(key, keylen);
if (!a)
goto error;
mpi_normalize(a);
rc = sm2_ecc_os2ec(ec->Q, a);
mpi_free(a);
if (rc)
goto error;
return 0;
error:
mpi_point_release(ec->Q);
ec->Q = NULL;
return rc;
}
static unsigned int sm2_max_size(struct crypto_akcipher *tfm)
{
/* Unlimited max size */
return PAGE_SIZE;
}
static int sm2_init_tfm(struct crypto_akcipher *tfm)
{
struct mpi_ec_ctx *ec = akcipher_tfm_ctx(tfm);
return sm2_ec_ctx_init(ec);
}
static void sm2_exit_tfm(struct crypto_akcipher *tfm)
{
struct mpi_ec_ctx *ec = akcipher_tfm_ctx(tfm);
sm2_ec_ctx_deinit(ec);
}
static struct akcipher_alg sm2 = {
.verify = sm2_verify,
.set_pub_key = sm2_set_pub_key,
.max_size = sm2_max_size,
.init = sm2_init_tfm,
.exit = sm2_exit_tfm,
.base = {
.cra_name = "sm2",
.cra_driver_name = "sm2-generic",
.cra_priority = 100,
.cra_module = THIS_MODULE,
.cra_ctxsize = sizeof(struct mpi_ec_ctx),
},
};
static int sm2_init(void)
{
return crypto_register_akcipher(&sm2);
}
static void sm2_exit(void)
{
crypto_unregister_akcipher(&sm2);
}
subsys_initcall(sm2_init);
module_exit(sm2_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Tianjia Zhang <tianjia.zhang@linux.alibaba.com>");
MODULE_DESCRIPTION("SM2 generic algorithm");
MODULE_ALIAS_CRYPTO("sm2-generic");
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