1 /*
2 * Copyright 2011-2021 The OpenSSL Project Authors. All Rights Reserved.
3 * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
4 *
5 * Licensed under the Apache License 2.0 (the "License"). You may not use
6 * this file except in compliance with the License. You can obtain a copy
7 * in the file LICENSE in the source distribution or at
8 * https://www.openssl.org/source/license.html
9 */
10
11 /*
12 * ECDSA low level APIs are deprecated for public use, but still ok for
13 * internal use.
14 */
15 #include "internal/deprecated.h"
16
17 #include <openssl/err.h>
18 #include <openssl/symhacks.h>
19
20 #include "ec_local.h"
21
ossl_ec_GFp_simple_set_compressed_coordinates(const EC_GROUP * group,EC_POINT * point,const BIGNUM * x_,int y_bit,BN_CTX * ctx)22 int ossl_ec_GFp_simple_set_compressed_coordinates(const EC_GROUP *group,
23 EC_POINT *point,
24 const BIGNUM *x_, int y_bit,
25 BN_CTX *ctx)
26 {
27 BN_CTX *new_ctx = NULL;
28 BIGNUM *tmp1, *tmp2, *x, *y;
29 int ret = 0;
30
31 if (ctx == NULL) {
32 ctx = new_ctx = BN_CTX_new_ex(group->libctx);
33 if (ctx == NULL)
34 return 0;
35 }
36
37 y_bit = (y_bit != 0);
38
39 BN_CTX_start(ctx);
40 tmp1 = BN_CTX_get(ctx);
41 tmp2 = BN_CTX_get(ctx);
42 x = BN_CTX_get(ctx);
43 y = BN_CTX_get(ctx);
44 if (y == NULL)
45 goto err;
46
47 /*-
48 * Recover y. We have a Weierstrass equation
49 * y^2 = x^3 + a*x + b,
50 * so y is one of the square roots of x^3 + a*x + b.
51 */
52
53 /* tmp1 := x^3 */
54 if (!BN_nnmod(x, x_, group->field, ctx))
55 goto err;
56 if (group->meth->field_decode == 0) {
57 /* field_{sqr,mul} work on standard representation */
58 if (!group->meth->field_sqr(group, tmp2, x_, ctx))
59 goto err;
60 if (!group->meth->field_mul(group, tmp1, tmp2, x_, ctx))
61 goto err;
62 } else {
63 if (!BN_mod_sqr(tmp2, x_, group->field, ctx))
64 goto err;
65 if (!BN_mod_mul(tmp1, tmp2, x_, group->field, ctx))
66 goto err;
67 }
68
69 /* tmp1 := tmp1 + a*x */
70 if (group->a_is_minus3) {
71 if (!BN_mod_lshift1_quick(tmp2, x, group->field))
72 goto err;
73 if (!BN_mod_add_quick(tmp2, tmp2, x, group->field))
74 goto err;
75 if (!BN_mod_sub_quick(tmp1, tmp1, tmp2, group->field))
76 goto err;
77 } else {
78 if (group->meth->field_decode) {
79 if (!group->meth->field_decode(group, tmp2, group->a, ctx))
80 goto err;
81 if (!BN_mod_mul(tmp2, tmp2, x, group->field, ctx))
82 goto err;
83 } else {
84 /* field_mul works on standard representation */
85 if (!group->meth->field_mul(group, tmp2, group->a, x, ctx))
86 goto err;
87 }
88
89 if (!BN_mod_add_quick(tmp1, tmp1, tmp2, group->field))
90 goto err;
91 }
92
93 /* tmp1 := tmp1 + b */
94 if (group->meth->field_decode) {
95 if (!group->meth->field_decode(group, tmp2, group->b, ctx))
96 goto err;
97 if (!BN_mod_add_quick(tmp1, tmp1, tmp2, group->field))
98 goto err;
99 } else {
100 if (!BN_mod_add_quick(tmp1, tmp1, group->b, group->field))
101 goto err;
102 }
103
104 ERR_set_mark();
105 if (!BN_mod_sqrt(y, tmp1, group->field, ctx)) {
106 #ifndef FIPS_MODULE
107 unsigned long err = ERR_peek_last_error();
108
109 if (ERR_GET_LIB(err) == ERR_LIB_BN
110 && ERR_GET_REASON(err) == BN_R_NOT_A_SQUARE) {
111 ERR_pop_to_mark();
112 ERR_raise(ERR_LIB_EC, EC_R_INVALID_COMPRESSED_POINT);
113 } else
114 #endif
115 {
116 ERR_clear_last_mark();
117 ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
118 }
119 goto err;
120 }
121 ERR_clear_last_mark();
122
123 if (y_bit != BN_is_odd(y)) {
124 if (BN_is_zero(y)) {
125 int kron;
126
127 kron = BN_kronecker(x, group->field, ctx);
128 if (kron == -2)
129 goto err;
130
131 if (kron == 1)
132 ERR_raise(ERR_LIB_EC, EC_R_INVALID_COMPRESSION_BIT);
133 else
134 /*
135 * BN_mod_sqrt() should have caught this error (not a square)
136 */
137 ERR_raise(ERR_LIB_EC, EC_R_INVALID_COMPRESSED_POINT);
138 goto err;
139 }
140 if (!BN_usub(y, group->field, y))
141 goto err;
142 }
143 if (y_bit != BN_is_odd(y)) {
144 ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
145 goto err;
146 }
147
148 if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
149 goto err;
150
151 ret = 1;
152
153 err:
154 BN_CTX_end(ctx);
155 BN_CTX_free(new_ctx);
156 return ret;
157 }
158
ossl_ec_GFp_simple_point2oct(const EC_GROUP * group,const EC_POINT * point,point_conversion_form_t form,unsigned char * buf,size_t len,BN_CTX * ctx)159 size_t ossl_ec_GFp_simple_point2oct(const EC_GROUP *group, const EC_POINT *point,
160 point_conversion_form_t form,
161 unsigned char *buf, size_t len, BN_CTX *ctx)
162 {
163 size_t ret;
164 BN_CTX *new_ctx = NULL;
165 int used_ctx = 0;
166 BIGNUM *x, *y;
167 size_t field_len, i, skip;
168
169 if ((form != POINT_CONVERSION_COMPRESSED)
170 && (form != POINT_CONVERSION_UNCOMPRESSED)
171 && (form != POINT_CONVERSION_HYBRID)) {
172 ERR_raise(ERR_LIB_EC, EC_R_INVALID_FORM);
173 goto err;
174 }
175
176 if (EC_POINT_is_at_infinity(group, point)) {
177 /* encodes to a single 0 octet */
178 if (buf != NULL) {
179 if (len < 1) {
180 ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
181 return 0;
182 }
183 buf[0] = 0;
184 }
185 return 1;
186 }
187
188 /* ret := required output buffer length */
189 field_len = BN_num_bytes(group->field);
190 ret =
191 (form ==
192 POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
193
194 /* if 'buf' is NULL, just return required length */
195 if (buf != NULL) {
196 if (len < ret) {
197 ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
198 goto err;
199 }
200
201 if (ctx == NULL) {
202 ctx = new_ctx = BN_CTX_new_ex(group->libctx);
203 if (ctx == NULL)
204 return 0;
205 }
206
207 BN_CTX_start(ctx);
208 used_ctx = 1;
209 x = BN_CTX_get(ctx);
210 y = BN_CTX_get(ctx);
211 if (y == NULL)
212 goto err;
213
214 if (!EC_POINT_get_affine_coordinates(group, point, x, y, ctx))
215 goto err;
216
217 if ((form == POINT_CONVERSION_COMPRESSED
218 || form == POINT_CONVERSION_HYBRID) && BN_is_odd(y))
219 buf[0] = form + 1;
220 else
221 buf[0] = form;
222
223 i = 1;
224
225 skip = field_len - BN_num_bytes(x);
226 if (skip > field_len) {
227 ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
228 goto err;
229 }
230 while (skip > 0) {
231 buf[i++] = 0;
232 skip--;
233 }
234 skip = BN_bn2bin(x, buf + i);
235 i += skip;
236 if (i != 1 + field_len) {
237 ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
238 goto err;
239 }
240
241 if (form == POINT_CONVERSION_UNCOMPRESSED
242 || form == POINT_CONVERSION_HYBRID) {
243 skip = field_len - BN_num_bytes(y);
244 if (skip > field_len) {
245 ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
246 goto err;
247 }
248 while (skip > 0) {
249 buf[i++] = 0;
250 skip--;
251 }
252 skip = BN_bn2bin(y, buf + i);
253 i += skip;
254 }
255
256 if (i != ret) {
257 ERR_raise(ERR_LIB_EC, ERR_R_INTERNAL_ERROR);
258 goto err;
259 }
260 }
261
262 if (used_ctx)
263 BN_CTX_end(ctx);
264 BN_CTX_free(new_ctx);
265 return ret;
266
267 err:
268 if (used_ctx)
269 BN_CTX_end(ctx);
270 BN_CTX_free(new_ctx);
271 return 0;
272 }
273
ossl_ec_GFp_simple_oct2point(const EC_GROUP * group,EC_POINT * point,const unsigned char * buf,size_t len,BN_CTX * ctx)274 int ossl_ec_GFp_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
275 const unsigned char *buf, size_t len,
276 BN_CTX *ctx)
277 {
278 point_conversion_form_t form;
279 int y_bit;
280 BN_CTX *new_ctx = NULL;
281 BIGNUM *x, *y;
282 size_t field_len, enc_len;
283 int ret = 0;
284
285 if (len == 0) {
286 ERR_raise(ERR_LIB_EC, EC_R_BUFFER_TOO_SMALL);
287 return 0;
288 }
289 form = buf[0];
290 y_bit = form & 1;
291 form = form & ~1U;
292 if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
293 && (form != POINT_CONVERSION_UNCOMPRESSED)
294 && (form != POINT_CONVERSION_HYBRID)) {
295 ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
296 return 0;
297 }
298 if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
299 ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
300 return 0;
301 }
302
303 if (form == 0) {
304 if (len != 1) {
305 ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
306 return 0;
307 }
308
309 return EC_POINT_set_to_infinity(group, point);
310 }
311
312 field_len = BN_num_bytes(group->field);
313 enc_len =
314 (form ==
315 POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
316
317 if (len != enc_len) {
318 ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
319 return 0;
320 }
321
322 if (ctx == NULL) {
323 ctx = new_ctx = BN_CTX_new_ex(group->libctx);
324 if (ctx == NULL)
325 return 0;
326 }
327
328 BN_CTX_start(ctx);
329 x = BN_CTX_get(ctx);
330 y = BN_CTX_get(ctx);
331 if (y == NULL)
332 goto err;
333
334 if (!BN_bin2bn(buf + 1, field_len, x))
335 goto err;
336 if (BN_ucmp(x, group->field) >= 0) {
337 ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
338 goto err;
339 }
340
341 if (form == POINT_CONVERSION_COMPRESSED) {
342 if (!EC_POINT_set_compressed_coordinates(group, point, x, y_bit, ctx))
343 goto err;
344 } else {
345 if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
346 goto err;
347 if (BN_ucmp(y, group->field) >= 0) {
348 ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
349 goto err;
350 }
351 if (form == POINT_CONVERSION_HYBRID) {
352 if (y_bit != BN_is_odd(y)) {
353 ERR_raise(ERR_LIB_EC, EC_R_INVALID_ENCODING);
354 goto err;
355 }
356 }
357
358 /*
359 * EC_POINT_set_affine_coordinates is responsible for checking that
360 * the point is on the curve.
361 */
362 if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
363 goto err;
364 }
365
366 ret = 1;
367
368 err:
369 BN_CTX_end(ctx);
370 BN_CTX_free(new_ctx);
371 return ret;
372 }
373
