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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Elliptic Curve (Russian) Digital Signature Algorithm for Cryptographic API
4 *
5 * Copyright (c) 2019 Vitaly Chikunov <[email protected]>
6 *
7 * References:
8 * GOST 34.10-2018, GOST R 34.10-2012, RFC 7091, ISO/IEC 14888-3:2018.
9 *
10 * Historical references:
11 * GOST R 34.10-2001, RFC 4357, ISO/IEC 14888-3:2006/Amd 1:2010.
12 *
13 * This program is free software; you can redistribute it and/or modify it
14 * under the terms of the GNU General Public License as published by the Free
15 * Software Foundation; either version 2 of the License, or (at your option)
16 * any later version.
17 */
18
19#include <linux/module.h>
20#include <linux/crypto.h>
21#include <crypto/sig.h>
22#include <crypto/streebog.h>
23#include <crypto/internal/ecc.h>
24#include <crypto/internal/sig.h>
25#include <linux/oid_registry.h>
26#include "ecrdsa_params.asn1.h"
27#include "ecrdsa_pub_key.asn1.h"
28#include "ecrdsa_defs.h"
29
30#define ECRDSA_MAX_SIG_SIZE (2 * 512 / 8)
31#define ECRDSA_MAX_DIGITS (512 / 64)
32
33struct ecrdsa_ctx {
34 enum OID algo_oid; /* overall public key oid */
35 enum OID curve_oid; /* parameter */
36 enum OID digest_oid; /* parameter */
37 const struct ecc_curve *curve; /* curve from oid */
38 unsigned int digest_len; /* parameter (bytes) */
39 const char *digest; /* digest name from oid */
40 unsigned int key_len; /* @key length (bytes) */
41 const char *key; /* raw public key */
42 struct ecc_point pub_key;
43 u64 _pubp[2][ECRDSA_MAX_DIGITS]; /* point storage for @pub_key */
44};
45
46static const struct ecc_curve *get_curve_by_oid(enum OID oid)
47{
48 switch (oid) {
49 case OID_gostCPSignA:
50 case OID_gostTC26Sign256B:
51 return &gost_cp256a;
52 case OID_gostCPSignB:
53 case OID_gostTC26Sign256C:
54 return &gost_cp256b;
55 case OID_gostCPSignC:
56 case OID_gostTC26Sign256D:
57 return &gost_cp256c;
58 case OID_gostTC26Sign512A:
59 return &gost_tc512a;
60 case OID_gostTC26Sign512B:
61 return &gost_tc512b;
62 /* The following two aren't implemented: */
63 case OID_gostTC26Sign256A:
64 case OID_gostTC26Sign512C:
65 default:
66 return NULL;
67 }
68}
69
70static int ecrdsa_verify(struct crypto_sig *tfm,
71 const void *src, unsigned int slen,
72 const void *digest, unsigned int dlen)
73{
74 struct ecrdsa_ctx *ctx = crypto_sig_ctx(tfm);
75 unsigned int ndigits = dlen / sizeof(u64);
76 u64 r[ECRDSA_MAX_DIGITS]; /* witness (r) */
77 u64 _r[ECRDSA_MAX_DIGITS]; /* -r */
78 u64 s[ECRDSA_MAX_DIGITS]; /* second part of sig (s) */
79 u64 e[ECRDSA_MAX_DIGITS]; /* h \mod q */
80 u64 *v = e; /* e^{-1} \mod q */
81 u64 z1[ECRDSA_MAX_DIGITS];
82 u64 *z2 = _r;
83 struct ecc_point cc = ECC_POINT_INIT(s, e, ndigits); /* reuse s, e */
84
85 /*
86 * Digest value, digest algorithm, and curve (modulus) should have the
87 * same length (256 or 512 bits), public key and signature should be
88 * twice bigger.
89 */
90 if (!ctx->curve ||
91 !ctx->digest ||
92 !src ||
93 !digest ||
94 !ctx->pub_key.x ||
95 dlen != ctx->digest_len ||
96 dlen != ctx->curve->g.ndigits * sizeof(u64) ||
97 ctx->pub_key.ndigits != ctx->curve->g.ndigits ||
98 dlen * 2 != slen ||
99 WARN_ON(slen > ECRDSA_MAX_SIG_SIZE) ||
100 WARN_ON(dlen > STREEBOG512_DIGEST_SIZE))
101 return -EBADMSG;
102
103 vli_from_be64(s, src, ndigits);
104 vli_from_be64(r, src + ndigits * sizeof(u64), ndigits);
105
106 /* Step 1: verify that 0 < r < q, 0 < s < q */
107 if (vli_is_zero(r, ndigits) ||
108 vli_cmp(r, ctx->curve->n, ndigits) >= 0 ||
109 vli_is_zero(s, ndigits) ||
110 vli_cmp(s, ctx->curve->n, ndigits) >= 0)
111 return -EKEYREJECTED;
112
113 /* Step 2: calculate hash (h) of the message (passed as input) */
114 /* Step 3: calculate e = h \mod q */
115 vli_from_le64(e, digest, ndigits);
116 if (vli_cmp(e, ctx->curve->n, ndigits) >= 0)
117 vli_sub(e, e, ctx->curve->n, ndigits);
118 if (vli_is_zero(e, ndigits))
119 e[0] = 1;
120
121 /* Step 4: calculate v = e^{-1} \mod q */
122 vli_mod_inv(v, e, ctx->curve->n, ndigits);
123
124 /* Step 5: calculate z_1 = sv \mod q, z_2 = -rv \mod q */
125 vli_mod_mult_slow(z1, s, v, ctx->curve->n, ndigits);
126 vli_sub(_r, ctx->curve->n, r, ndigits);
127 vli_mod_mult_slow(z2, _r, v, ctx->curve->n, ndigits);
128
129 /* Step 6: calculate point C = z_1P + z_2Q, and R = x_c \mod q */
130 ecc_point_mult_shamir(&cc, z1, &ctx->curve->g, z2, &ctx->pub_key,
131 ctx->curve);
132 if (vli_cmp(cc.x, ctx->curve->n, ndigits) >= 0)
133 vli_sub(cc.x, cc.x, ctx->curve->n, ndigits);
134
135 /* Step 7: if R == r signature is valid */
136 if (!vli_cmp(cc.x, r, ndigits))
137 return 0;
138 else
139 return -EKEYREJECTED;
140}
141
142int ecrdsa_param_curve(void *context, size_t hdrlen, unsigned char tag,
143 const void *value, size_t vlen)
144{
145 struct ecrdsa_ctx *ctx = context;
146
147 ctx->curve_oid = look_up_OID(value, vlen);
148 if (ctx->curve_oid == OID__NR)
149 return -EINVAL;
150 ctx->curve = get_curve_by_oid(ctx->curve_oid);
151 return 0;
152}
153
154/* Optional. If present should match expected digest algo OID. */
155int ecrdsa_param_digest(void *context, size_t hdrlen, unsigned char tag,
156 const void *value, size_t vlen)
157{
158 struct ecrdsa_ctx *ctx = context;
159 int digest_oid = look_up_OID(value, vlen);
160
161 if (digest_oid != ctx->digest_oid)
162 return -EINVAL;
163 return 0;
164}
165
166int ecrdsa_parse_pub_key(void *context, size_t hdrlen, unsigned char tag,
167 const void *value, size_t vlen)
168{
169 struct ecrdsa_ctx *ctx = context;
170
171 ctx->key = value;
172 ctx->key_len = vlen;
173 return 0;
174}
175
176static u8 *ecrdsa_unpack_u32(u32 *dst, void *src)
177{
178 memcpy(dst, src, sizeof(u32));
179 return src + sizeof(u32);
180}
181
182/* Parse BER encoded subjectPublicKey. */
183static int ecrdsa_set_pub_key(struct crypto_sig *tfm, const void *key,
184 unsigned int keylen)
185{
186 struct ecrdsa_ctx *ctx = crypto_sig_ctx(tfm);
187 unsigned int ndigits;
188 u32 algo, paramlen;
189 u8 *params;
190 int err;
191
192 err = asn1_ber_decoder(&ecrdsa_pub_key_decoder, ctx, key, keylen);
193 if (err < 0)
194 return err;
195
196 /* Key parameters is in the key after keylen. */
197 params = ecrdsa_unpack_u32(&paramlen,
198 ecrdsa_unpack_u32(&algo, (u8 *)key + keylen));
199
200 if (algo == OID_gost2012PKey256) {
201 ctx->digest = "streebog256";
202 ctx->digest_oid = OID_gost2012Digest256;
203 ctx->digest_len = 256 / 8;
204 } else if (algo == OID_gost2012PKey512) {
205 ctx->digest = "streebog512";
206 ctx->digest_oid = OID_gost2012Digest512;
207 ctx->digest_len = 512 / 8;
208 } else
209 return -ENOPKG;
210 ctx->algo_oid = algo;
211
212 /* Parse SubjectPublicKeyInfo.AlgorithmIdentifier.parameters. */
213 err = asn1_ber_decoder(&ecrdsa_params_decoder, ctx, params, paramlen);
214 if (err < 0)
215 return err;
216 /*
217 * Sizes of algo (set in digest_len) and curve should match
218 * each other.
219 */
220 if (!ctx->curve ||
221 ctx->curve->g.ndigits * sizeof(u64) != ctx->digest_len)
222 return -ENOPKG;
223 /*
224 * Key is two 256- or 512-bit coordinates which should match
225 * curve size.
226 */
227 if ((ctx->key_len != (2 * 256 / 8) &&
228 ctx->key_len != (2 * 512 / 8)) ||
229 ctx->key_len != ctx->curve->g.ndigits * sizeof(u64) * 2)
230 return -ENOPKG;
231
232 ndigits = ctx->key_len / sizeof(u64) / 2;
233 ctx->pub_key = ECC_POINT_INIT(ctx->_pubp[0], ctx->_pubp[1], ndigits);
234 vli_from_le64(ctx->pub_key.x, ctx->key, ndigits);
235 vli_from_le64(ctx->pub_key.y, ctx->key + ndigits * sizeof(u64),
236 ndigits);
237
238 if (ecc_is_pubkey_valid_partial(ctx->curve, &ctx->pub_key))
239 return -EKEYREJECTED;
240
241 return 0;
242}
243
244static unsigned int ecrdsa_key_size(struct crypto_sig *tfm)
245{
246 struct ecrdsa_ctx *ctx = crypto_sig_ctx(tfm);
247
248 /*
249 * Verify doesn't need any output, so it's just informational
250 * for keyctl to determine the key bit size.
251 */
252 return ctx->pub_key.ndigits * sizeof(u64) * BITS_PER_BYTE;
253}
254
255static unsigned int ecrdsa_max_size(struct crypto_sig *tfm)
256{
257 struct ecrdsa_ctx *ctx = crypto_sig_ctx(tfm);
258
259 return 2 * ctx->pub_key.ndigits * sizeof(u64);
260}
261
262static struct sig_alg ecrdsa_alg = {
263 .verify = ecrdsa_verify,
264 .set_pub_key = ecrdsa_set_pub_key,
265 .key_size = ecrdsa_key_size,
266 .max_size = ecrdsa_max_size,
267 .base = {
268 .cra_name = "ecrdsa",
269 .cra_driver_name = "ecrdsa-generic",
270 .cra_priority = 100,
271 .cra_module = THIS_MODULE,
272 .cra_ctxsize = sizeof(struct ecrdsa_ctx),
273 },
274};
275
276static int __init ecrdsa_mod_init(void)
277{
278 return crypto_register_sig(&ecrdsa_alg);
279}
280
281static void __exit ecrdsa_mod_fini(void)
282{
283 crypto_unregister_sig(&ecrdsa_alg);
284}
285
286module_init(ecrdsa_mod_init);
287module_exit(ecrdsa_mod_fini);
288
289MODULE_LICENSE("GPL");
290MODULE_AUTHOR("Vitaly Chikunov <[email protected]>");
291MODULE_DESCRIPTION("EC-RDSA generic algorithm");
292MODULE_ALIAS_CRYPTO("ecrdsa");
293MODULE_ALIAS_CRYPTO("ecrdsa-generic");