1 /* SPDX-License-Identifier: GPL-2.0-or-later */
3 * SM2 asymmetric public-key algorithm
4 * as specified by OSCCA GM/T 0003.1-2012 -- 0003.5-2012 SM2 and
5 * described at https://tools.ietf.org/html/draft-shen-sm2-ecdsa-02
7 * Copyright (c) 2020, Alibaba Group.
8 * Authors: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
11 #include <linux/module.h>
12 #include <linux/mpi.h>
13 #include <crypto/internal/akcipher.h>
14 #include <crypto/akcipher.h>
15 #include <crypto/hash.h>
16 #include <crypto/sm3_base.h>
17 #include <crypto/rng.h>
18 #include <crypto/sm2.h>
19 #include "sm2signature.asn1.h"
21 #define MPI_NBYTES(m) ((mpi_get_nbits(m) + 7) / 8)
23 struct ecc_domain_parms {
24 const char *desc; /* Description of the curve. */
25 unsigned int nbits; /* Number of bits. */
26 unsigned int fips:1; /* True if this is a FIPS140-2 approved curve */
28 /* The model describing this curve. This is mainly used to select
31 enum gcry_mpi_ec_models model;
33 /* The actual ECC dialect used. This is used for curve specific
34 * optimizations and to select encodings etc.
36 enum ecc_dialects dialect;
38 const char *p; /* The prime defining the field. */
39 const char *a, *b; /* The coefficients. For Twisted Edwards
40 * Curves b is used for d. For Montgomery
41 * Curves (a,b) has ((A-2)/4,B^-1).
43 const char *n; /* The order of the base point. */
44 const char *g_x, *g_y; /* Base point. */
45 unsigned int h; /* Cofactor. */
48 static const struct ecc_domain_parms sm2_ecp = {
52 .model = MPI_EC_WEIERSTRASS,
53 .dialect = ECC_DIALECT_STANDARD,
54 .p = "0xfffffffeffffffffffffffffffffffffffffffff00000000ffffffffffffffff",
55 .a = "0xfffffffeffffffffffffffffffffffffffffffff00000000fffffffffffffffc",
56 .b = "0x28e9fa9e9d9f5e344d5a9e4bcf6509a7f39789f515ab8f92ddbcbd414d940e93",
57 .n = "0xfffffffeffffffffffffffffffffffff7203df6b21c6052b53bbf40939d54123",
58 .g_x = "0x32c4ae2c1f1981195f9904466a39c9948fe30bbff2660be1715a4589334c74c7",
59 .g_y = "0xbc3736a2f4f6779c59bdcee36b692153d0a9877cc62a474002df32e52139f0a0",
63 static int sm2_ec_ctx_init(struct mpi_ec_ctx *ec)
65 const struct ecc_domain_parms *ecp = &sm2_ecp;
70 p = mpi_scanval(ecp->p);
71 a = mpi_scanval(ecp->a);
72 b = mpi_scanval(ecp->b);
76 x = mpi_scanval(ecp->g_x);
77 y = mpi_scanval(ecp->g_y);
83 ec->Q = mpi_point_new(0);
87 /* mpi_ec_setup_elliptic_curve */
88 ec->G = mpi_point_new(0);
90 mpi_point_release(ec->Q);
96 mpi_set_ui(ec->G->z, 1);
99 ec->n = mpi_scanval(ecp->n);
101 mpi_point_release(ec->Q);
102 mpi_point_release(ec->G);
107 ec->name = ecp->desc;
108 mpi_ec_init(ec, ecp->model, ecp->dialect, 0, p, a, b);
123 static void sm2_ec_ctx_deinit(struct mpi_ec_ctx *ec)
127 memset(ec, 0, sizeof(*ec));
130 /* RESULT must have been initialized and is set on success to the
131 * point given by VALUE.
133 static int sm2_ecc_os2ec(MPI_POINT result, MPI value)
140 n = MPI_NBYTES(value);
141 buf = kmalloc(n, GFP_KERNEL);
145 rc = mpi_print(GCRYMPI_FMT_USG, buf, n, &n, value);
150 if (n < 1 || ((n - 1) % 2))
152 /* No support for point compression */
158 x = mpi_read_raw_data(buf + 1, n);
161 y = mpi_read_raw_data(buf + 1 + n, n);
167 mpi_set(result->x, x);
168 mpi_set(result->y, y);
169 mpi_set_ui(result->z, 1);
181 struct sm2_signature_ctx {
186 int sm2_get_signature_r(void *context, size_t hdrlen, unsigned char tag,
187 const void *value, size_t vlen)
189 struct sm2_signature_ctx *sig = context;
194 sig->sig_r = mpi_read_raw_data(value, vlen);
201 int sm2_get_signature_s(void *context, size_t hdrlen, unsigned char tag,
202 const void *value, size_t vlen)
204 struct sm2_signature_ctx *sig = context;
209 sig->sig_s = mpi_read_raw_data(value, vlen);
216 static int sm2_z_digest_update(struct shash_desc *desc,
217 MPI m, unsigned int pbytes)
219 static const unsigned char zero[32];
223 in = mpi_get_buffer(m, &inlen, NULL);
227 if (inlen < pbytes) {
228 /* padding with zero */
229 crypto_sm3_update(desc, zero, pbytes - inlen);
230 crypto_sm3_update(desc, in, inlen);
231 } else if (inlen > pbytes) {
232 /* skip the starting zero */
233 crypto_sm3_update(desc, in + inlen - pbytes, pbytes);
235 crypto_sm3_update(desc, in, inlen);
242 static int sm2_z_digest_update_point(struct shash_desc *desc,
243 MPI_POINT point, struct mpi_ec_ctx *ec, unsigned int pbytes)
251 if (!mpi_ec_get_affine(x, y, point, ec) &&
252 !sm2_z_digest_update(desc, x, pbytes) &&
253 !sm2_z_digest_update(desc, y, pbytes))
261 int sm2_compute_z_digest(struct crypto_akcipher *tfm,
262 const unsigned char *id, size_t id_len,
263 unsigned char dgst[SM3_DIGEST_SIZE])
265 struct mpi_ec_ctx *ec = akcipher_tfm_ctx(tfm);
267 unsigned char entl[2];
268 SHASH_DESC_ON_STACK(desc, NULL);
271 if (id_len > (USHRT_MAX / 8) || !ec->Q)
274 bits_len = (uint16_t)(id_len * 8);
275 entl[0] = bits_len >> 8;
276 entl[1] = bits_len & 0xff;
278 pbytes = MPI_NBYTES(ec->p);
280 /* ZA = H256(ENTLA | IDA | a | b | xG | yG | xA | yA) */
282 crypto_sm3_update(desc, entl, 2);
283 crypto_sm3_update(desc, id, id_len);
285 if (sm2_z_digest_update(desc, ec->a, pbytes) ||
286 sm2_z_digest_update(desc, ec->b, pbytes) ||
287 sm2_z_digest_update_point(desc, ec->G, ec, pbytes) ||
288 sm2_z_digest_update_point(desc, ec->Q, ec, pbytes))
291 crypto_sm3_final(desc, dgst);
294 EXPORT_SYMBOL(sm2_compute_z_digest);
296 static int _sm2_verify(struct mpi_ec_ctx *ec, MPI hash, MPI sig_r, MPI sig_s)
299 struct gcry_mpi_point sG, tP;
301 MPI x1 = NULL, y1 = NULL;
309 /* r, s in [1, n-1] */
310 if (mpi_cmp_ui(sig_r, 1) < 0 || mpi_cmp(sig_r, ec->n) > 0 ||
311 mpi_cmp_ui(sig_s, 1) < 0 || mpi_cmp(sig_s, ec->n) > 0) {
315 /* t = (r + s) % n, t == 0 */
316 mpi_addm(t, sig_r, sig_s, ec->n);
317 if (mpi_cmp_ui(t, 0) == 0)
320 /* sG + tP = (x1, y1) */
322 mpi_ec_mul_point(&sG, sig_s, ec->G, ec);
323 mpi_ec_mul_point(&tP, t, ec->Q, ec);
324 mpi_ec_add_points(&sG, &sG, &tP, ec);
325 if (mpi_ec_get_affine(x1, y1, &sG, ec))
328 /* R = (e + x1) % n */
329 mpi_addm(t, hash, x1, ec->n);
333 if (mpi_cmp(t, sig_r))
339 mpi_point_free_parts(&sG);
340 mpi_point_free_parts(&tP);
348 static int sm2_verify(struct akcipher_request *req)
350 struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
351 struct mpi_ec_ctx *ec = akcipher_tfm_ctx(tfm);
352 unsigned char *buffer;
353 struct sm2_signature_ctx sig;
357 if (unlikely(!ec->Q))
360 buffer = kmalloc(req->src_len + req->dst_len, GFP_KERNEL);
364 sg_pcopy_to_buffer(req->src,
365 sg_nents_for_len(req->src, req->src_len + req->dst_len),
366 buffer, req->src_len + req->dst_len, 0);
370 ret = asn1_ber_decoder(&sm2signature_decoder, &sig,
371 buffer, req->src_len);
376 hash = mpi_read_raw_data(buffer + req->src_len, req->dst_len);
380 ret = _sm2_verify(ec, hash, sig.sig_r, sig.sig_s);
390 static int sm2_set_pub_key(struct crypto_akcipher *tfm,
391 const void *key, unsigned int keylen)
393 struct mpi_ec_ctx *ec = akcipher_tfm_ctx(tfm);
397 /* include the uncompressed flag '0x04' */
398 a = mpi_read_raw_data(key, keylen);
403 rc = sm2_ecc_os2ec(ec->Q, a);
409 static unsigned int sm2_max_size(struct crypto_akcipher *tfm)
411 /* Unlimited max size */
415 static int sm2_init_tfm(struct crypto_akcipher *tfm)
417 struct mpi_ec_ctx *ec = akcipher_tfm_ctx(tfm);
419 return sm2_ec_ctx_init(ec);
422 static void sm2_exit_tfm(struct crypto_akcipher *tfm)
424 struct mpi_ec_ctx *ec = akcipher_tfm_ctx(tfm);
426 sm2_ec_ctx_deinit(ec);
429 static struct akcipher_alg sm2 = {
430 .verify = sm2_verify,
431 .set_pub_key = sm2_set_pub_key,
432 .max_size = sm2_max_size,
433 .init = sm2_init_tfm,
434 .exit = sm2_exit_tfm,
437 .cra_driver_name = "sm2-generic",
439 .cra_module = THIS_MODULE,
440 .cra_ctxsize = sizeof(struct mpi_ec_ctx),
444 static int sm2_init(void)
446 return crypto_register_akcipher(&sm2);
449 static void sm2_exit(void)
451 crypto_unregister_akcipher(&sm2);
454 subsys_initcall(sm2_init);
455 module_exit(sm2_exit);
457 MODULE_LICENSE("GPL");
458 MODULE_AUTHOR("Tianjia Zhang <tianjia.zhang@linux.alibaba.com>");
459 MODULE_DESCRIPTION("SM2 generic algorithm");
460 MODULE_ALIAS_CRYPTO("sm2-generic");