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 */
ecdsa_get_signature_rs(u64 * dest,size_t hdrlen,unsigned char tag,const void * value,size_t vlen,unsigned int ndigits)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 keylen = ndigits * sizeof(u64);
39 ssize_t diff = vlen - keylen;
40 const char *d = value;
41 u8 rs[ECC_MAX_BYTES];
42
43 if (!value || !vlen)
44 return -EINVAL;
45
46 /* diff = 0: 'value' has exacly the right size
47 * diff > 0: 'value' has too many bytes; one leading zero is allowed that
48 * makes the value a positive integer; error on more
49 * diff < 0: 'value' is missing leading zeros, which we add
50 */
51 if (diff > 0) {
52 /* skip over leading zeros that make 'value' a positive int */
53 if (*d == 0) {
54 vlen -= 1;
55 diff--;
56 d++;
57 }
58 if (diff)
59 return -EINVAL;
60 }
61 if (-diff >= keylen)
62 return -EINVAL;
63
64 if (diff) {
65 /* leading zeros not given in 'value' */
66 memset(rs, 0, -diff);
67 }
68
69 memcpy(&rs[-diff], d, vlen);
70
71 ecc_swap_digits((u64 *)rs, dest, ndigits);
72
73 return 0;
74 }
75
ecdsa_get_signature_r(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)76 int ecdsa_get_signature_r(void *context, size_t hdrlen, unsigned char tag,
77 const void *value, size_t vlen)
78 {
79 struct ecdsa_signature_ctx *sig = context;
80
81 return ecdsa_get_signature_rs(sig->r, hdrlen, tag, value, vlen,
82 sig->curve->g.ndigits);
83 }
84
ecdsa_get_signature_s(void * context,size_t hdrlen,unsigned char tag,const void * value,size_t vlen)85 int ecdsa_get_signature_s(void *context, size_t hdrlen, unsigned char tag,
86 const void *value, size_t vlen)
87 {
88 struct ecdsa_signature_ctx *sig = context;
89
90 return ecdsa_get_signature_rs(sig->s, hdrlen, tag, value, vlen,
91 sig->curve->g.ndigits);
92 }
93
_ecdsa_verify(struct ecc_ctx * ctx,const u64 * hash,const u64 * r,const u64 * s)94 static int _ecdsa_verify(struct ecc_ctx *ctx, const u64 *hash, const u64 *r, const u64 *s)
95 {
96 const struct ecc_curve *curve = ctx->curve;
97 unsigned int ndigits = curve->g.ndigits;
98 u64 s1[ECC_MAX_DIGITS];
99 u64 u1[ECC_MAX_DIGITS];
100 u64 u2[ECC_MAX_DIGITS];
101 u64 x1[ECC_MAX_DIGITS];
102 u64 y1[ECC_MAX_DIGITS];
103 struct ecc_point res = ECC_POINT_INIT(x1, y1, ndigits);
104
105 /* 0 < r < n and 0 < s < n */
106 if (vli_is_zero(r, ndigits) || vli_cmp(r, curve->n, ndigits) >= 0 ||
107 vli_is_zero(s, ndigits) || vli_cmp(s, curve->n, ndigits) >= 0)
108 return -EBADMSG;
109
110 /* hash is given */
111 pr_devel("hash : %016llx %016llx ... %016llx\n",
112 hash[ndigits - 1], hash[ndigits - 2], hash[0]);
113
114 /* s1 = (s^-1) mod n */
115 vli_mod_inv(s1, s, curve->n, ndigits);
116 /* u1 = (hash * s1) mod n */
117 vli_mod_mult_slow(u1, hash, s1, curve->n, ndigits);
118 /* u2 = (r * s1) mod n */
119 vli_mod_mult_slow(u2, r, s1, curve->n, ndigits);
120 /* res = u1*G + u2 * pub_key */
121 ecc_point_mult_shamir(&res, u1, &curve->g, u2, &ctx->pub_key, curve);
122
123 /* res.x = res.x mod n (if res.x > order) */
124 if (unlikely(vli_cmp(res.x, curve->n, ndigits) == 1))
125 /* faster alternative for NIST p384, p256 & p192 */
126 vli_sub(res.x, res.x, curve->n, ndigits);
127
128 if (!vli_cmp(res.x, r, ndigits))
129 return 0;
130
131 return -EKEYREJECTED;
132 }
133
134 /*
135 * Verify an ECDSA signature.
136 */
ecdsa_verify(struct akcipher_request * req)137 static int ecdsa_verify(struct akcipher_request *req)
138 {
139 struct crypto_akcipher *tfm = crypto_akcipher_reqtfm(req);
140 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
141 size_t keylen = ctx->curve->g.ndigits * sizeof(u64);
142 struct ecdsa_signature_ctx sig_ctx = {
143 .curve = ctx->curve,
144 };
145 u8 rawhash[ECC_MAX_BYTES];
146 u64 hash[ECC_MAX_DIGITS];
147 unsigned char *buffer;
148 ssize_t diff;
149 int ret;
150
151 if (unlikely(!ctx->pub_key_set))
152 return -EINVAL;
153
154 buffer = kmalloc(req->src_len + req->dst_len, GFP_KERNEL);
155 if (!buffer)
156 return -ENOMEM;
157
158 sg_pcopy_to_buffer(req->src,
159 sg_nents_for_len(req->src, req->src_len + req->dst_len),
160 buffer, req->src_len + req->dst_len, 0);
161
162 ret = asn1_ber_decoder(&ecdsasignature_decoder, &sig_ctx,
163 buffer, req->src_len);
164 if (ret < 0)
165 goto error;
166
167 /* if the hash is shorter then we will add leading zeros to fit to ndigits */
168 diff = keylen - req->dst_len;
169 if (diff >= 0) {
170 if (diff)
171 memset(rawhash, 0, diff);
172 memcpy(&rawhash[diff], buffer + req->src_len, req->dst_len);
173 } else if (diff < 0) {
174 /* given hash is longer, we take the left-most bytes */
175 memcpy(&rawhash, buffer + req->src_len, keylen);
176 }
177
178 ecc_swap_digits((u64 *)rawhash, hash, ctx->curve->g.ndigits);
179
180 ret = _ecdsa_verify(ctx, hash, sig_ctx.r, sig_ctx.s);
181
182 error:
183 kfree(buffer);
184
185 return ret;
186 }
187
ecdsa_ecc_ctx_init(struct ecc_ctx * ctx,unsigned int curve_id)188 static int ecdsa_ecc_ctx_init(struct ecc_ctx *ctx, unsigned int curve_id)
189 {
190 ctx->curve_id = curve_id;
191 ctx->curve = ecc_get_curve(curve_id);
192 if (!ctx->curve)
193 return -EINVAL;
194
195 return 0;
196 }
197
198
ecdsa_ecc_ctx_deinit(struct ecc_ctx * ctx)199 static void ecdsa_ecc_ctx_deinit(struct ecc_ctx *ctx)
200 {
201 ctx->pub_key_set = false;
202 }
203
ecdsa_ecc_ctx_reset(struct ecc_ctx * ctx)204 static int ecdsa_ecc_ctx_reset(struct ecc_ctx *ctx)
205 {
206 unsigned int curve_id = ctx->curve_id;
207 int ret;
208
209 ecdsa_ecc_ctx_deinit(ctx);
210 ret = ecdsa_ecc_ctx_init(ctx, curve_id);
211 if (ret == 0)
212 ctx->pub_key = ECC_POINT_INIT(ctx->x, ctx->y,
213 ctx->curve->g.ndigits);
214 return ret;
215 }
216
217 /*
218 * Set the public key given the raw uncompressed key data from an X509
219 * certificate. The key data contain the concatenated X and Y coordinates of
220 * the public key.
221 */
ecdsa_set_pub_key(struct crypto_akcipher * tfm,const void * key,unsigned int keylen)222 static int ecdsa_set_pub_key(struct crypto_akcipher *tfm, const void *key, unsigned int keylen)
223 {
224 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
225 const unsigned char *d = key;
226 const u64 *digits = (const u64 *)&d[1];
227 unsigned int ndigits;
228 int ret;
229
230 ret = ecdsa_ecc_ctx_reset(ctx);
231 if (ret < 0)
232 return ret;
233
234 if (keylen < 1 || (((keylen - 1) >> 1) % sizeof(u64)) != 0)
235 return -EINVAL;
236 /* we only accept uncompressed format indicated by '4' */
237 if (d[0] != 4)
238 return -EINVAL;
239
240 keylen--;
241 ndigits = (keylen >> 1) / sizeof(u64);
242 if (ndigits != ctx->curve->g.ndigits)
243 return -EINVAL;
244
245 ecc_swap_digits(digits, ctx->pub_key.x, ndigits);
246 ecc_swap_digits(&digits[ndigits], ctx->pub_key.y, ndigits);
247 ret = ecc_is_pubkey_valid_full(ctx->curve, &ctx->pub_key);
248
249 ctx->pub_key_set = ret == 0;
250
251 return ret;
252 }
253
ecdsa_exit_tfm(struct crypto_akcipher * tfm)254 static void ecdsa_exit_tfm(struct crypto_akcipher *tfm)
255 {
256 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
257
258 ecdsa_ecc_ctx_deinit(ctx);
259 }
260
ecdsa_max_size(struct crypto_akcipher * tfm)261 static unsigned int ecdsa_max_size(struct crypto_akcipher *tfm)
262 {
263 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
264
265 return ctx->pub_key.ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
266 }
267
ecdsa_nist_p384_init_tfm(struct crypto_akcipher * tfm)268 static int ecdsa_nist_p384_init_tfm(struct crypto_akcipher *tfm)
269 {
270 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
271
272 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P384);
273 }
274
275 static struct akcipher_alg ecdsa_nist_p384 = {
276 .verify = ecdsa_verify,
277 .set_pub_key = ecdsa_set_pub_key,
278 .max_size = ecdsa_max_size,
279 .init = ecdsa_nist_p384_init_tfm,
280 .exit = ecdsa_exit_tfm,
281 .base = {
282 .cra_name = "ecdsa-nist-p384",
283 .cra_driver_name = "ecdsa-nist-p384-generic",
284 .cra_priority = 100,
285 .cra_module = THIS_MODULE,
286 .cra_ctxsize = sizeof(struct ecc_ctx),
287 },
288 };
289
ecdsa_nist_p256_init_tfm(struct crypto_akcipher * tfm)290 static int ecdsa_nist_p256_init_tfm(struct crypto_akcipher *tfm)
291 {
292 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
293
294 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P256);
295 }
296
297 static struct akcipher_alg ecdsa_nist_p256 = {
298 .verify = ecdsa_verify,
299 .set_pub_key = ecdsa_set_pub_key,
300 .max_size = ecdsa_max_size,
301 .init = ecdsa_nist_p256_init_tfm,
302 .exit = ecdsa_exit_tfm,
303 .base = {
304 .cra_name = "ecdsa-nist-p256",
305 .cra_driver_name = "ecdsa-nist-p256-generic",
306 .cra_priority = 100,
307 .cra_module = THIS_MODULE,
308 .cra_ctxsize = sizeof(struct ecc_ctx),
309 },
310 };
311
ecdsa_nist_p192_init_tfm(struct crypto_akcipher * tfm)312 static int ecdsa_nist_p192_init_tfm(struct crypto_akcipher *tfm)
313 {
314 struct ecc_ctx *ctx = akcipher_tfm_ctx(tfm);
315
316 return ecdsa_ecc_ctx_init(ctx, ECC_CURVE_NIST_P192);
317 }
318
319 static struct akcipher_alg ecdsa_nist_p192 = {
320 .verify = ecdsa_verify,
321 .set_pub_key = ecdsa_set_pub_key,
322 .max_size = ecdsa_max_size,
323 .init = ecdsa_nist_p192_init_tfm,
324 .exit = ecdsa_exit_tfm,
325 .base = {
326 .cra_name = "ecdsa-nist-p192",
327 .cra_driver_name = "ecdsa-nist-p192-generic",
328 .cra_priority = 100,
329 .cra_module = THIS_MODULE,
330 .cra_ctxsize = sizeof(struct ecc_ctx),
331 },
332 };
333 static bool ecdsa_nist_p192_registered;
334
ecdsa_init(void)335 static int __init ecdsa_init(void)
336 {
337 int ret;
338
339 /* NIST p192 may not be available in FIPS mode */
340 ret = crypto_register_akcipher(&ecdsa_nist_p192);
341 ecdsa_nist_p192_registered = ret == 0;
342
343 ret = crypto_register_akcipher(&ecdsa_nist_p256);
344 if (ret)
345 goto nist_p256_error;
346
347 ret = crypto_register_akcipher(&ecdsa_nist_p384);
348 if (ret)
349 goto nist_p384_error;
350
351 return 0;
352
353 nist_p384_error:
354 crypto_unregister_akcipher(&ecdsa_nist_p256);
355
356 nist_p256_error:
357 if (ecdsa_nist_p192_registered)
358 crypto_unregister_akcipher(&ecdsa_nist_p192);
359 return ret;
360 }
361
ecdsa_exit(void)362 static void __exit ecdsa_exit(void)
363 {
364 if (ecdsa_nist_p192_registered)
365 crypto_unregister_akcipher(&ecdsa_nist_p192);
366 crypto_unregister_akcipher(&ecdsa_nist_p256);
367 crypto_unregister_akcipher(&ecdsa_nist_p384);
368 }
369
370 subsys_initcall(ecdsa_init);
371 module_exit(ecdsa_exit);
372
373 MODULE_LICENSE("GPL");
374 MODULE_AUTHOR("Stefan Berger <stefanb@linux.ibm.com>");
375 MODULE_DESCRIPTION("ECDSA generic algorithm");
376 MODULE_ALIAS_CRYPTO("ecdsa-generic");
377