1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Copyright (c) 2021 IBM Corporation
4 */
5
6#include <linux/module.h>
7#include <crypto/internal/ecc.h>
8#include <crypto/internal/sig.h>
9#include <crypto/ecdh.h>
10#include <crypto/sha2.h>
11#include <crypto/sig.h>
12
13struct ecc_ctx {
14 unsigned int curve_id;
15 const struct ecc_curve *curve;
16
17 bool pub_key_set;
18 u64 x[ECC_MAX_DIGITS]; /* pub key x and y coordinates */
19 u64 y[ECC_MAX_DIGITS];
20 struct ecc_point pub_key;
21};
22
23static int _ecdsa_verify(struct ecc_ctx *ctx, const u64 *hash, const u64 *r, const u64 *s)
24{
25 const struct ecc_curve *curve = ctx->curve;
26 unsigned int ndigits = curve->g.ndigits;
27 u64 s1[ECC_MAX_DIGITS];
28 u64 u1[ECC_MAX_DIGITS];
29 u64 u2[ECC_MAX_DIGITS];
30 u64 x1[ECC_MAX_DIGITS];
31 u64 y1[ECC_MAX_DIGITS];
32 struct ecc_point res = ECC_POINT_INIT(x1, y1, ndigits);
33
34 /* 0 < r < n and 0 < s < n */
35 if (vli_is_zero(vli: r, ndigits) || vli_cmp(left: r, right: curve->n, ndigits) >= 0 ||
36 vli_is_zero(vli: s, ndigits) || vli_cmp(left: s, right: curve->n, ndigits) >= 0)
37 return -EBADMSG;
38
39 /* hash is given */
40 pr_devel("hash : %016llx %016llx ... %016llx\n",
41 hash[ndigits - 1], hash[ndigits - 2], hash[0]);
42
43 /* s1 = (s^-1) mod n */
44 vli_mod_inv(result: s1, input: s, mod: curve->n, ndigits);
45 /* u1 = (hash * s1) mod n */
46 vli_mod_mult_slow(result: u1, left: hash, right: s1, mod: curve->n, ndigits);
47 /* u2 = (r * s1) mod n */
48 vli_mod_mult_slow(result: u2, left: r, right: s1, mod: curve->n, ndigits);
49 /* res = u1*G + u2 * pub_key */
50 ecc_point_mult_shamir(result: &res, x: u1, p: &curve->g, y: u2, q: &ctx->pub_key, curve);
51
52 /* res.x = res.x mod n (if res.x > order) */
53 if (unlikely(vli_cmp(res.x, curve->n, ndigits) == 1))
54 /* faster alternative for NIST p521, p384, p256 & p192 */
55 vli_sub(result: res.x, left: res.x, right: curve->n, ndigits);
56
57 if (!vli_cmp(left: res.x, right: r, ndigits))
58 return 0;
59
60 return -EKEYREJECTED;
61}
62
63/*
64 * Verify an ECDSA signature.
65 */
66static int ecdsa_verify(struct crypto_sig *tfm,
67 const void *src, unsigned int slen,
68 const void *digest, unsigned int dlen)
69{
70 struct ecc_ctx *ctx = crypto_sig_ctx(tfm);
71 size_t bufsize = ctx->curve->g.ndigits * sizeof(u64);
72 const struct ecdsa_raw_sig *sig = src;
73 u64 hash[ECC_MAX_DIGITS];
74
75 if (unlikely(!ctx->pub_key_set))
76 return -EINVAL;
77
78 if (slen != sizeof(*sig))
79 return -EINVAL;
80
81 if (bufsize > dlen)
82 bufsize = dlen;
83
84 ecc_digits_from_bytes(in: digest, nbytes: bufsize, out: hash, ndigits: ctx->curve->g.ndigits);
85
86 return _ecdsa_verify(ctx, hash, r: sig->r, s: sig->s);
87}
88
89static int ecdsa_ecc_ctx_init(struct ecc_ctx *ctx, unsigned int curve_id)
90{
91 ctx->curve_id = curve_id;
92 ctx->curve = ecc_get_curve(curve_id);
93 if (!ctx->curve)
94 return -EINVAL;
95
96 return 0;
97}
98
99
100static void ecdsa_ecc_ctx_deinit(struct ecc_ctx *ctx)
101{
102 ctx->pub_key_set = false;
103}
104
105static int ecdsa_ecc_ctx_reset(struct ecc_ctx *ctx)
106{
107 unsigned int curve_id = ctx->curve_id;
108 int ret;
109
110 ecdsa_ecc_ctx_deinit(ctx);
111 ret = ecdsa_ecc_ctx_init(ctx, curve_id);
112 if (ret == 0)
113 ctx->pub_key = ECC_POINT_INIT(ctx->x, ctx->y,
114 ctx->curve->g.ndigits);
115 return ret;
116}
117
118/*
119 * Set the public ECC key as defined by RFC5480 section 2.2 "Subject Public
120 * Key". Only the uncompressed format is supported.
121 */
122static int ecdsa_set_pub_key(struct crypto_sig *tfm, const void *key,
123 unsigned int keylen)
124{
125 struct ecc_ctx *ctx = crypto_sig_ctx(tfm);
126 unsigned int digitlen, ndigits;
127 const unsigned char *d = key;
128 int ret;
129
130 ret = ecdsa_ecc_ctx_reset(ctx);
131 if (ret < 0)
132 return ret;
133
134 if (keylen < 1 || ((keylen - 1) & 1) != 0)
135 return -EINVAL;
136 /* we only accept uncompressed format indicated by '4' */
137 if (d[0] != 4)
138 return -EINVAL;
139
140 keylen--;
141 digitlen = keylen >> 1;
142
143 ndigits = DIV_ROUND_UP(digitlen, sizeof(u64));
144 if (ndigits != ctx->curve->g.ndigits)
145 return -EINVAL;
146
147 d++;
148
149 ecc_digits_from_bytes(in: d, nbytes: digitlen, out: ctx->pub_key.x, ndigits);
150 ecc_digits_from_bytes(in: &d[digitlen], nbytes: digitlen, out: ctx->pub_key.y, ndigits);
151
152 ret = ecc_is_pubkey_valid_full(curve: ctx->curve, pk: &ctx->pub_key);
153
154 ctx->pub_key_set = ret == 0;
155
156 return ret;
157}
158
159static void ecdsa_exit_tfm(struct crypto_sig *tfm)
160{
161 struct ecc_ctx *ctx = crypto_sig_ctx(tfm);
162
163 ecdsa_ecc_ctx_deinit(ctx);
164}
165
166static unsigned int ecdsa_key_size(struct crypto_sig *tfm)
167{
168 struct ecc_ctx *ctx = crypto_sig_ctx(tfm);
169
170 return ctx->curve->nbits;
171}
172
173static unsigned int ecdsa_digest_size(struct crypto_sig *tfm)
174{
175 /*
176 * ECDSA key sizes are much smaller than RSA, and thus could
177 * operate on (hashed) inputs that are larger than the key size.
178 * E.g. SHA384-hashed input used with secp256r1 based keys.
179 * Return the largest supported hash size (SHA512).
180 */
181 return SHA512_DIGEST_SIZE;
182}
183
184static int ecdsa_nist_p521_init_tfm(struct crypto_sig *tfm)
185{
186 struct ecc_ctx *ctx = crypto_sig_ctx(tfm);
187
188 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P521);
189}
190
191static struct sig_alg ecdsa_nist_p521 = {
192 .verify = ecdsa_verify,
193 .set_pub_key = ecdsa_set_pub_key,
194 .key_size = ecdsa_key_size,
195 .digest_size = ecdsa_digest_size,
196 .init = ecdsa_nist_p521_init_tfm,
197 .exit = ecdsa_exit_tfm,
198 .base = {
199 .cra_name = "ecdsa-nist-p521",
200 .cra_driver_name = "ecdsa-nist-p521-generic",
201 .cra_priority = 100,
202 .cra_module = THIS_MODULE,
203 .cra_ctxsize = sizeof(struct ecc_ctx),
204 },
205};
206
207static int ecdsa_nist_p384_init_tfm(struct crypto_sig *tfm)
208{
209 struct ecc_ctx *ctx = crypto_sig_ctx(tfm);
210
211 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P384);
212}
213
214static struct sig_alg ecdsa_nist_p384 = {
215 .verify = ecdsa_verify,
216 .set_pub_key = ecdsa_set_pub_key,
217 .key_size = ecdsa_key_size,
218 .digest_size = ecdsa_digest_size,
219 .init = ecdsa_nist_p384_init_tfm,
220 .exit = ecdsa_exit_tfm,
221 .base = {
222 .cra_name = "ecdsa-nist-p384",
223 .cra_driver_name = "ecdsa-nist-p384-generic",
224 .cra_priority = 100,
225 .cra_module = THIS_MODULE,
226 .cra_ctxsize = sizeof(struct ecc_ctx),
227 },
228};
229
230static int ecdsa_nist_p256_init_tfm(struct crypto_sig *tfm)
231{
232 struct ecc_ctx *ctx = crypto_sig_ctx(tfm);
233
234 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P256);
235}
236
237static struct sig_alg ecdsa_nist_p256 = {
238 .verify = ecdsa_verify,
239 .set_pub_key = ecdsa_set_pub_key,
240 .key_size = ecdsa_key_size,
241 .digest_size = ecdsa_digest_size,
242 .init = ecdsa_nist_p256_init_tfm,
243 .exit = ecdsa_exit_tfm,
244 .base = {
245 .cra_name = "ecdsa-nist-p256",
246 .cra_driver_name = "ecdsa-nist-p256-generic",
247 .cra_priority = 100,
248 .cra_module = THIS_MODULE,
249 .cra_ctxsize = sizeof(struct ecc_ctx),
250 },
251};
252
253static int ecdsa_nist_p192_init_tfm(struct crypto_sig *tfm)
254{
255 struct ecc_ctx *ctx = crypto_sig_ctx(tfm);
256
257 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P192);
258}
259
260static struct sig_alg ecdsa_nist_p192 = {
261 .verify = ecdsa_verify,
262 .set_pub_key = ecdsa_set_pub_key,
263 .key_size = ecdsa_key_size,
264 .digest_size = ecdsa_digest_size,
265 .init = ecdsa_nist_p192_init_tfm,
266 .exit = ecdsa_exit_tfm,
267 .base = {
268 .cra_name = "ecdsa-nist-p192",
269 .cra_driver_name = "ecdsa-nist-p192-generic",
270 .cra_priority = 100,
271 .cra_module = THIS_MODULE,
272 .cra_ctxsize = sizeof(struct ecc_ctx),
273 },
274};
275static bool ecdsa_nist_p192_registered;
276
277static int __init ecdsa_init(void)
278{
279 int ret;
280
281 /* NIST p192 may not be available in FIPS mode */
282 ret = crypto_register_sig(alg: &ecdsa_nist_p192);
283 ecdsa_nist_p192_registered = ret == 0;
284
285 ret = crypto_register_sig(alg: &ecdsa_nist_p256);
286 if (ret)
287 goto nist_p256_error;
288
289 ret = crypto_register_sig(alg: &ecdsa_nist_p384);
290 if (ret)
291 goto nist_p384_error;
292
293 ret = crypto_register_sig(alg: &ecdsa_nist_p521);
294 if (ret)
295 goto nist_p521_error;
296
297 ret = crypto_register_template(tmpl: &ecdsa_x962_tmpl);
298 if (ret)
299 goto x962_tmpl_error;
300
301 ret = crypto_register_template(tmpl: &ecdsa_p1363_tmpl);
302 if (ret)
303 goto p1363_tmpl_error;
304
305 return 0;
306
307p1363_tmpl_error:
308 crypto_unregister_template(tmpl: &ecdsa_x962_tmpl);
309
310x962_tmpl_error:
311 crypto_unregister_sig(alg: &ecdsa_nist_p521);
312
313nist_p521_error:
314 crypto_unregister_sig(alg: &ecdsa_nist_p384);
315
316nist_p384_error:
317 crypto_unregister_sig(alg: &ecdsa_nist_p256);
318
319nist_p256_error:
320 if (ecdsa_nist_p192_registered)
321 crypto_unregister_sig(alg: &ecdsa_nist_p192);
322 return ret;
323}
324
325static void __exit ecdsa_exit(void)
326{
327 crypto_unregister_template(tmpl: &ecdsa_x962_tmpl);
328 crypto_unregister_template(tmpl: &ecdsa_p1363_tmpl);
329
330 if (ecdsa_nist_p192_registered)
331 crypto_unregister_sig(alg: &ecdsa_nist_p192);
332 crypto_unregister_sig(alg: &ecdsa_nist_p256);
333 crypto_unregister_sig(alg: &ecdsa_nist_p384);
334 crypto_unregister_sig(alg: &ecdsa_nist_p521);
335}
336
337module_init(ecdsa_init);
338module_exit(ecdsa_exit);
339
340MODULE_LICENSE("GPL");
341MODULE_AUTHOR("Stefan Berger <stefanb@linux.ibm.com>");
342MODULE_DESCRIPTION("ECDSA generic algorithm");
343MODULE_ALIAS_CRYPTO("ecdsa-nist-p192");
344MODULE_ALIAS_CRYPTO("ecdsa-nist-p256");
345MODULE_ALIAS_CRYPTO("ecdsa-nist-p384");
346MODULE_ALIAS_CRYPTO("ecdsa-nist-p521");
347MODULE_ALIAS_CRYPTO("ecdsa-generic");
348

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source code of linux/crypto/ecdsa.c