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/akcipher.h>
8 #include <crypto/internal/ecc.h>
9 #include <crypto/akcipher.h>
10 #include <crypto/ecdh.h>
11 #include <linux/asn1_decoder.h>
12 #include <linux/scatterlist.h>
13
14 #include "ecdsasignature.asn1.h"
15
16 struct ecc_ctx {
17 unsigned int curve_id;
18 const struct ecc_curve *curve;
19
20 bool pub_key_set;
21 u64 x[ECC_MAX_DIGITS]; /* pub key x and y coordinates */
22 u64 y[ECC_MAX_DIGITS];
23 struct ecc_point pub_key;
24 };
25
26 struct ecdsa_signature_ctx {
27 const struct ecc_curve *curve;
28 u64 r[ECC_MAX_DIGITS];
29 u64 s[ECC_MAX_DIGITS];
30 };
31
32 /*
33 * Get the r and s components of a signature from the X509 certificate.
34 */
35 static int ecdsa_get_signature_rs(u64 *dest, size_t hdrlen, unsigned char tag,
36 const void *value, size_t vlen, unsigned int ndigits)
37 {
38 size_t bufsize = ndigits * sizeof(u64);
39 ssize_t diff = vlen - bufsize;
40 const char *d = value;
41
42 if (!value || !vlen)
43 return -EINVAL;
44
45 /* diff = 0: 'value' has exacly the right size
46 * diff > 0: 'value' has too many bytes; one leading zero is allowed that
47 * makes the value a positive integer; error on more
48 * diff < 0: 'value' is missing leading zeros
49 */
50 if (diff > 0) {
51 /* skip over leading zeros that make 'value' a positive int */
52 if (*d == 0) {
53 vlen -= 1;
54 diff--;
55 d++;
56 }
57 if (diff)
58 return -EINVAL;
59 }
60 if (-diff >= bufsize)
61 return -EINVAL;
62
63 ecc_digits_from_bytes(d, vlen, dest, ndigits);
64
65 return 0;
66 }
67
68 int ecdsa_get_signature_r(void *context, size_t hdrlen, unsigned char tag,
69 const void *value, size_t vlen)
70 {
71 struct ecdsa_signature_ctx *sig = context;
72
73 return ecdsa_get_signature_rs(sig->r, hdrlen, tag, value, vlen,
74 sig->curve->g.ndigits);
75 }
76
77 int ecdsa_get_signature_s(void *context, size_t hdrlen, unsigned char tag,
78 const void *value, size_t vlen)
79 {
80 struct ecdsa_signature_ctx *sig = context;
81
82 return ecdsa_get_signature_rs(sig->s, hdrlen, tag, value, vlen,
83 sig->curve->g.ndigits);
84 }
85
86 static int _ecdsa_verify(struct ecc_ctx *ctx, const u64 *hash, const u64 *r, const u64 *s)
87 {
88 const struct ecc_curve *curve = ctx->curve;
89 unsigned int ndigits = curve->g.ndigits;
90 u64 s1[ECC_MAX_DIGITS];
91 u64 u1[ECC_MAX_DIGITS];
92 u64 u2[ECC_MAX_DIGITS];
93 u64 x1[ECC_MAX_DIGITS];
94 u64 y1[ECC_MAX_DIGITS];
95 struct ecc_point res = ECC_POINT_INIT(x1, y1, ndigits);
96
97 /* 0 < r < n and 0 < s < n */
98 if (vli_is_zero(r, ndigits) || vli_cmp(r, curve->n, ndigits) >= 0 ||
99 vli_is_zero(s, ndigits) || vli_cmp(s, curve->n, ndigits) >= 0)
100 return -EBADMSG;
101
102 /* hash is given */
103 pr_devel("hash : %016llx %016llx ... %016llx\n",
104 hash[ndigits - 1], hash[ndigits - 2], hash[0]);
105
106 /* s1 = (s^-1) mod n */
107 vli_mod_inv(s1, s, curve->n, ndigits);
108 /* u1 = (hash * s1) mod n */
109 vli_mod_mult_slow(u1, hash, s1, curve->n, ndigits);
110 /* u2 = (r * s1) mod n */
111 vli_mod_mult_slow(u2, r, s1, curve->n, ndigits);
112 /* res = u1*G + u2 * pub_key */
113 ecc_point_mult_shamir(&res, u1, &curve->g, u2, &ctx->pub_key, curve);
114
115 /* res.x = res.x mod n (if res.x > order) */
116 if (unlikely(vli_cmp(res.x, curve->n, ndigits) == 1))
117 /* faster alternative for NIST p521, p384, p256 & p192 */
118 vli_sub(res.x, res.x, curve->n, ndigits);
119
120 if (!vli_cmp(res.x, r, ndigits))
121 return 0;
122
123 return -EKEYREJECTED;
124 }
125
126 /*
127 * Verify an ECDSA signature.
128 */
129 static int ecdsa_verify(struct akcipher_request *req)
130 {
131 struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
132 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
133 size_t bufsize = ctx->curve->g.ndigits * sizeof(u64);
134 struct ecdsa_signature_ctx sig_ctx = {
135 .curve = ctx->curve,
136 };
137 u64 hash[ECC_MAX_DIGITS];
138 unsigned char *buffer;
139 int ret;
140
141 if (unlikely(!ctx->pub_key_set))
142 return -EINVAL;
143
144 buffer = kmalloc(req->src_len + req->dst_len, GFP_KERNEL);
145 if (!buffer)
146 return -ENOMEM;
147
148 sg_pcopy_to_buffer(req->src,
149 sg_nents_for_len(req->src, req->src_len + req->dst_len),
150 buffer, req->src_len + req->dst_len, 0);
151
152 ret = asn1_ber_decoder(&ecdsasignature_decoder, &sig_ctx,
153 buffer, req->src_len);
154 if (ret < 0)
155 goto error;
156
157 if (bufsize > req->dst_len)
158 bufsize = req->dst_len;
159
160 ecc_digits_from_bytes(buffer + req->src_len, bufsize,
161 hash, ctx->curve->g.ndigits);
162
163 ret = _ecdsa_verify(ctx, hash, sig_ctx.r, sig_ctx.s);
164
165 error:
166 kfree(buffer);
167
168 return ret;
169 }
170
171 static int ecdsa_ecc_ctx_init(struct ecc_ctx *ctx, unsigned int curve_id)
172 {
173 ctx->curve_id = curve_id;
174 ctx->curve = ecc_get_curve(curve_id);
175 if (!ctx->curve)
176 return -EINVAL;
177
178 return 0;
179 }
180
181
182 static void ecdsa_ecc_ctx_deinit(struct ecc_ctx *ctx)
183 {
184 ctx->pub_key_set = false;
185 }
186
187 static int ecdsa_ecc_ctx_reset(struct ecc_ctx *ctx)
188 {
189 unsigned int curve_id = ctx->curve_id;
190 int ret;
191
192 ecdsa_ecc_ctx_deinit(ctx);
193 ret = ecdsa_ecc_ctx_init(ctx, curve_id);
194 if (ret == 0)
195 ctx->pub_key = ECC_POINT_INIT(ctx->x, ctx->y,
196 ctx->curve->g.ndigits);
197 return ret;
198 }
199
200 /*
201 * Set the public ECC key as defined by RFC5480 section 2.2 "Subject Public
202 * Key". Only the uncompressed format is supported.
203 */
204 static int ecdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key, unsigned int keylen)
205 {
206 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
207 unsigned int digitlen, ndigits;
208 const unsigned char *d = key;
209 int ret;
210
211 ret = ecdsa_ecc_ctx_reset(ctx);
212 if (ret < 0)
213 return ret;
214
215 if (keylen < 1 || ((keylen - 1) & 1) != 0)
216 return -EINVAL;
217 /* we only accept uncompressed format indicated by '4' */
218 if (d[0] != 4)
219 return -EINVAL;
220
221 keylen--;
222 digitlen = keylen >> 1;
223
224 ndigits = DIV_ROUND_UP(digitlen, sizeof(u64));
225 if (ndigits != ctx->curve->g.ndigits)
226 return -EINVAL;
227
228 d++;
229
230 ecc_digits_from_bytes(d, digitlen, ctx->pub_key.x, ndigits);
231 ecc_digits_from_bytes(&d[digitlen], digitlen, ctx->pub_key.y, ndigits);
232
233 ret = ecc_is_pubkey_valid_full(ctx->curve, &ctx->pub_key);
234
235 ctx->pub_key_set = ret == 0;
236
237 return ret;
238 }
239
240 static void ecdsa_exit_tfm(struct crypto_akcipher *tfm)
241 {
242 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
243
244 ecdsa_ecc_ctx_deinit(ctx);
245 }
246
247 static unsigned int ecdsa_max_size(struct crypto_akcipher *tfm)
248 {
249 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
250
251 return DIV_ROUND_UP(ctx->curve->nbits, 8);
252 }
253
254 static int ecdsa_nist_p521_init_tfm(struct crypto_akcipher *tfm)
255 {
256 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
257
258 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P521);
259 }
260
261 static struct akcipher_alg ecdsa_nist_p521 = {
262 .verify = ecdsa_verify,
263 .set_pub_key = ecdsa_set_pub_key,
264 .max_size = ecdsa_max_size,
265 .init = ecdsa_nist_p521_init_tfm,
266 .exit = ecdsa_exit_tfm,
267 .base = {
268 .cra_name = "ecdsa-nist-p521",
269 .cra_driver_name = "ecdsa-nist-p521-generic",
270 .cra_priority = 100,
271 .cra_module = THIS_MODULE,
272 .cra_ctxsize = sizeof(struct ecc_ctx),
273 },
274 };
275
276 static int ecdsa_nist_p384_init_tfm(struct crypto_akcipher *tfm)
277 {
278 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
279
280 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P384);
281 }
282
283 static struct akcipher_alg ecdsa_nist_p384 = {
284 .verify = ecdsa_verify,
285 .set_pub_key = ecdsa_set_pub_key,
286 .max_size = ecdsa_max_size,
287 .init = ecdsa_nist_p384_init_tfm,
288 .exit = ecdsa_exit_tfm,
289 .base = {
290 .cra_name = "ecdsa-nist-p384",
291 .cra_driver_name = "ecdsa-nist-p384-generic",
292 .cra_priority = 100,
293 .cra_module = THIS_MODULE,
294 .cra_ctxsize = sizeof(struct ecc_ctx),
295 },
296 };
297
298 static int ecdsa_nist_p256_init_tfm(struct crypto_akcipher *tfm)
299 {
300 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
301
302 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P256);
303 }
304
305 static struct akcipher_alg ecdsa_nist_p256 = {
306 .verify = ecdsa_verify,
307 .set_pub_key = ecdsa_set_pub_key,
308 .max_size = ecdsa_max_size,
309 .init = ecdsa_nist_p256_init_tfm,
310 .exit = ecdsa_exit_tfm,
311 .base = {
312 .cra_name = "ecdsa-nist-p256",
313 .cra_driver_name = "ecdsa-nist-p256-generic",
314 .cra_priority = 100,
315 .cra_module = THIS_MODULE,
316 .cra_ctxsize = sizeof(struct ecc_ctx),
317 },
318 };
319
320 static int ecdsa_nist_p192_init_tfm(struct crypto_akcipher *tfm)
321 {
322 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
323
324 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P192);
325 }
326
327 static struct akcipher_alg ecdsa_nist_p192 = {
328 .verify = ecdsa_verify,
329 .set_pub_key = ecdsa_set_pub_key,
330 .max_size = ecdsa_max_size,
331 .init = ecdsa_nist_p192_init_tfm,
332 .exit = ecdsa_exit_tfm,
333 .base = {
334 .cra_name = "ecdsa-nist-p192",
335 .cra_driver_name = "ecdsa-nist-p192-generic",
336 .cra_priority = 100,
337 .cra_module = THIS_MODULE,
338 .cra_ctxsize = sizeof(struct ecc_ctx),
339 },
340 };
341 static bool ecdsa_nist_p192_registered;
342
343 static int __init ecdsa_init(void)
344 {
345 int ret;
346
347 /* NIST p192 may not be available in FIPS mode */
348 ret = crypto_register_akcipher(&ecdsa_nist_p192);
349 ecdsa_nist_p192_registered = ret == 0;
350
351 ret = crypto_register_akcipher(&ecdsa_nist_p256);
352 if (ret)
353 goto nist_p256_error;
354
355 ret = crypto_register_akcipher(&ecdsa_nist_p384);
356 if (ret)
357 goto nist_p384_error;
358
359 ret = crypto_register_akcipher(&ecdsa_nist_p521);
360 if (ret)
361 goto nist_p521_error;
362
363 return 0;
364
365 nist_p521_error:
366 crypto_unregister_akcipher(&ecdsa_nist_p384);
367
368 nist_p384_error:
369 crypto_unregister_akcipher(&ecdsa_nist_p256);
370
371 nist_p256_error:
372 if (ecdsa_nist_p192_registered)
373 crypto_unregister_akcipher(&ecdsa_nist_p192);
374 return ret;
375 }
376
377 static void __exit ecdsa_exit(void)
378 {
379 if (ecdsa_nist_p192_registered)
380 crypto_unregister_akcipher(&ecdsa_nist_p192);
381 crypto_unregister_akcipher(&ecdsa_nist_p256);
382 crypto_unregister_akcipher(&ecdsa_nist_p384);
383 crypto_unregister_akcipher(&ecdsa_nist_p521);
384 }
385
386 subsys_initcall(ecdsa_init);
387 module_exit(ecdsa_exit);
388
389 MODULE_LICENSE("GPL");
390 MODULE_AUTHOR("Stefan Berger <stefanb@linux.ibm.com>");
391 MODULE_DESCRIPTION("ECDSA generic algorithm");
392 MODULE_ALIAS_CRYPTO("ecdsa-nist-p192");
393 MODULE_ALIAS_CRYPTO("ecdsa-nist-p256");
394 MODULE_ALIAS_CRYPTO("ecdsa-nist-p384");
395 MODULE_ALIAS_CRYPTO("ecdsa-nist-p521");
396 MODULE_ALIAS_CRYPTO("ecdsa-generic");
397
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.