aboutsummaryrefslogtreecommitdiff
path: root/crypto/ecrdsa.c
blob: 6a3fd09057d0c96de203837f1006d7dc431bce7e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
// SPDX-License-Identifier: GPL-2.0+
/*
 * Elliptic Curve (Russian) Digital Signature Algorithm for Cryptographic API
 *
 * Copyright (c) 2019 Vitaly Chikunov <vt@altlinux.org>
 *
 * References:
 * GOST 34.10-2018, GOST R 34.10-2012, RFC 7091, ISO/IEC 14888-3:2018.
 *
 * Historical references:
 * GOST R 34.10-2001, RFC 4357, ISO/IEC 14888-3:2006/Amd 1:2010.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 */

#include <linux/module.h>
#include <linux/crypto.h>
#include <crypto/streebog.h>
#include <crypto/internal/akcipher.h>
#include <crypto/akcipher.h>
#include <linux/oid_registry.h>
#include <linux/scatterlist.h>
#include "ecrdsa_params.asn1.h"
#include "ecrdsa_pub_key.asn1.h"
#include "ecc.h"
#include "ecrdsa_defs.h"

#define ECRDSA_MAX_SIG_SIZE (2 * 512 / 8)
#define ECRDSA_MAX_DIGITS (512 / 64)

struct ecrdsa_ctx {
	enum OID algo_oid; /* overall public key oid */
	enum OID curve_oid; /* parameter */
	enum OID digest_oid; /* parameter */
	const struct ecc_curve *curve; /* curve from oid */
	unsigned int digest_len; /* parameter (bytes) */
	const char *digest; /* digest name from oid */
	unsigned int key_len; /* @key length (bytes) */
	const char *key; /* raw public key */
	struct ecc_point pub_key;
	u64 _pubp[2][ECRDSA_MAX_DIGITS]; /* point storage for @pub_key */
};

static const struct ecc_curve *get_curve_by_oid(enum OID oid)
{
	switch (oid) {
	case OID_gostCPSignA:
	case OID_gostTC26Sign256B:
		return &gost_cp256a;
	case OID_gostCPSignB:
	case OID_gostTC26Sign256C:
		return &gost_cp256b;
	case OID_gostCPSignC:
	case OID_gostTC26Sign256D:
		return &gost_cp256c;
	case OID_gostTC26Sign512A:
		return &gost_tc512a;
	case OID_gostTC26Sign512B:
		return &gost_tc512b;
	/* The following two aren't implemented: */
	case OID_gostTC26Sign256A:
	case OID_gostTC26Sign512C:
	default:
		return NULL;
	}
}

static int ecrdsa_verify(struct akcipher_request *req)
{
	struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
	struct ecrdsa_ctx *ctx = akcipher_tfm_ctx(tfm);
	unsigned char sig[ECRDSA_MAX_SIG_SIZE];
	unsigned char digest[STREEBOG512_DIGEST_SIZE];
	unsigned int ndigits = req->dst_len / sizeof(u64);
	u64 r[ECRDSA_MAX_DIGITS]; /* witness (r) */
	u64 _r[ECRDSA_MAX_DIGITS]; /* -r */
	u64 s[ECRDSA_MAX_DIGITS]; /* second part of sig (s) */
	u64 e[ECRDSA_MAX_DIGITS]; /* h \mod q */
	u64 *v = e;		  /* e^{-1} \mod q */
	u64 z1[ECRDSA_MAX_DIGITS];
	u64 *z2 = _r;
	struct ecc_point cc = ECC_POINT_INIT(s, e, ndigits); /* reuse s, e */

	/*
	 * Digest value, digest algorithm, and curve (modulus) should have the
	 * same length (256 or 512 bits), public key and signature should be
	 * twice bigger.
	 */
	if (!ctx->curve ||
	    !ctx->digest ||
	    !req->src ||
	    !ctx->pub_key.x ||
	    req->dst_len != ctx->digest_len ||
	    req->dst_len != ctx->curve->g.ndigits * sizeof(u64) ||
	    ctx->pub_key.ndigits != ctx->curve->g.ndigits ||
	    req->dst_len * 2 != req->src_len ||
	    WARN_ON(req->src_len > sizeof(sig)) ||
	    WARN_ON(req->dst_len > sizeof(digest)))
		return -EBADMSG;

	sg_copy_to_buffer(req->src, sg_nents_for_len(req->src, req->src_len),
			  sig, req->src_len);
	sg_pcopy_to_buffer(req->src,
			   sg_nents_for_len(req->src,
					    req->src_len + req->dst_len),
			   digest, req->dst_len, req->src_len);

	vli_from_be64(s, sig, ndigits);
	vli_from_be64(r, sig + ndigits * sizeof(u64), ndigits);

	/* Step 1: verify that 0 < r < q, 0 < s < q */
	if (vli_is_zero(r, ndigits) ||
	    vli_cmp(r, ctx->curve->n, ndigits) == 1 ||
	    vli_is_zero(s, ndigits) ||
	    vli_cmp(s, ctx->curve->n, ndigits) == 1)
		return -EKEYREJECTED;

	/* Step 2: calculate hash (h) of the message (passed as input) */
	/* Step 3: calculate e = h \mod q */
	vli_from_le64(e, digest, ndigits);
	if (vli_cmp(e, ctx->curve->n, ndigits) == 1)
		vli_sub(e, e, ctx->curve->n, ndigits);
	if (vli_is_zero(e, ndigits))
		e[0] = 1;

	/* Step 4: calculate v = e^{-1} \mod q */
	vli_mod_inv(v, e, ctx->curve->n, ndigits);

	/* Step 5: calculate z_1 = sv \mod q, z_2 = -rv \mod q */
	vli_mod_mult_slow(z1, s, v, ctx->curve->n, ndigits);
	vli_sub(_r, ctx->curve->n, r, ndigits);
	vli_mod_mult_slow(z2, _r, v, ctx->curve->n, ndigits);

	/* Step 6: calculate point C = z_1P + z_2Q, and R = x_c \mod q */
	ecc_point_mult_shamir(&cc, z1, &ctx->curve->g, z2, &ctx->pub_key,
			      ctx->curve);
	if (vli_cmp(cc.x, ctx->curve->n, ndigits) == 1)
		vli_sub(cc.x, cc.x, ctx->curve->n, ndigits);

	/* Step 7: if R == r signature is valid */
	if (!vli_cmp(cc.x, r, ndigits))
		return 0;
	else
		return -EKEYREJECTED;
}

int ecrdsa_param_curve(void *context, size_t hdrlen, unsigned char tag,
		       const void *value, size_t vlen)
{
	struct ecrdsa_ctx *ctx = context;

	ctx->curve_oid = look_up_OID(value, vlen);
	if (!ctx->curve_oid)
		return -EINVAL;
	ctx->curve = get_curve_by_oid(ctx->curve_oid);
	return 0;
}

/* Optional. If present should match expected digest algo OID. */
int ecrdsa_param_digest(void *context, size_t hdrlen, unsigned char tag,
			const void *value, size_t vlen)
{
	struct ecrdsa_ctx *ctx = context;
	int digest_oid = look_up_OID(value, vlen);

	if (digest_oid != ctx->digest_oid)
		return -EINVAL;
	return 0;
}

int ecrdsa_parse_pub_key(void *context, size_t hdrlen, unsigned char tag,
			 const void *value, size_t vlen)
{
	struct ecrdsa_ctx *ctx = context;

	ctx->key = value;
	ctx->key_len = vlen;
	return 0;
}

static u8 *ecrdsa_unpack_u32(u32 *dst, void *src)
{
	memcpy(dst, src, sizeof(u32));
	return src + sizeof(u32);
}

/* Parse BER encoded subjectPublicKey. */
static int ecrdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,
			      unsigned int keylen)
{
	struct ecrdsa_ctx *ctx = akcipher_tfm_ctx(tfm);
	unsigned int ndigits;
	u32 algo, paramlen;
	u8 *params;
	int err;

	err = asn1_ber_decoder(&ecrdsa_pub_key_decoder, ctx, key, keylen);
	if (err < 0)
		return err;

	/* Key parameters is in the key after keylen. */
	params = ecrdsa_unpack_u32(&paramlen,
			  ecrdsa_unpack_u32(&algo, (u8 *)key + keylen));

	if (algo == OID_gost2012PKey256) {
		ctx->digest	= "streebog256";
		ctx->digest_oid	= OID_gost2012Digest256;
		ctx->digest_len	= 256 / 8;
	} else if (algo == OID_gost2012PKey512) {
		ctx->digest	= "streebog512";
		ctx->digest_oid	= OID_gost2012Digest512;
		ctx->digest_len	= 512 / 8;
	} else
		return -ENOPKG;
	ctx->algo_oid = algo;

	/* Parse SubjectPublicKeyInfo.AlgorithmIdentifier.parameters. */
	err = asn1_ber_decoder(&ecrdsa_params_decoder, ctx, params, paramlen);
	if (err < 0)
		return err;
	/*
	 * Sizes of algo (set in digest_len) and curve should match
	 * each other.
	 */
	if (!ctx->curve ||
	    ctx->curve->g.ndigits * sizeof(u64) != ctx->digest_len)
		return -ENOPKG;
	/*
	 * Key is two 256- or 512-bit coordinates which should match
	 * curve size.
	 */
	if ((ctx->key_len != (2 * 256 / 8) &&
	     ctx->key_len != (2 * 512 / 8)) ||
	    ctx->key_len != ctx->curve->g.ndigits * sizeof(u64) * 2)
		return -ENOPKG;

	ndigits = ctx->key_len / sizeof(u64) / 2;
	ctx->pub_key = ECC_POINT_INIT(ctx->_pubp[0], ctx->_pubp[1], ndigits);
	vli_from_le64(ctx->pub_key.x, ctx->key, ndigits);
	vli_from_le64(ctx->pub_key.y, ctx->key + ndigits * sizeof(u64),
		      ndigits);

	if (ecc_is_pubkey_valid_partial(ctx->curve, &ctx->pub_key))
		return -EKEYREJECTED;

	return 0;
}

static unsigned int ecrdsa_max_size(struct crypto_akcipher *tfm)
{
	struct ecrdsa_ctx *ctx = akcipher_tfm_ctx(tfm);

	/*
	 * Verify doesn't need any output, so it's just informational
	 * for keyctl to determine the key bit size.
	 */
	return ctx->pub_key.ndigits * sizeof(u64);
}

static void ecrdsa_exit_tfm(struct crypto_akcipher *tfm)
{
}

static struct akcipher_alg ecrdsa_alg = {
	.verify		= ecrdsa_verify,
	.set_pub_key	= ecrdsa_set_pub_key,
	.max_size	= ecrdsa_max_size,
	.exit		= ecrdsa_exit_tfm,
	.base = {
		.cra_name	 = "ecrdsa",
		.cra_driver_name = "ecrdsa-generic",
		.cra_priority	 = 100,
		.cra_module	 = THIS_MODULE,
		.cra_ctxsize	 = sizeof(struct ecrdsa_ctx),
	},
};

static int __init ecrdsa_mod_init(void)
{
	return crypto_register_akcipher(&ecrdsa_alg);
}

static void __exit ecrdsa_mod_fini(void)
{
	crypto_unregister_akcipher(&ecrdsa_alg);
}

module_init(ecrdsa_mod_init);
module_exit(ecrdsa_mod_fini);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Vitaly Chikunov <vt@altlinux.org>");
MODULE_DESCRIPTION("EC-RDSA generic algorithm");
MODULE_ALIAS_CRYPTO("ecrdsa-generic");