Coverage Report

Created: 2018-08-29 13:53

/src/openssl/crypto/ec/ec2_oct.c
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Count
Source (jump to first uncovered line)
1
/*
2
 * Copyright 2011-2016 The OpenSSL Project Authors. All Rights Reserved.
3
 * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
4
 *
5
 * Licensed under the OpenSSL license (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
#include <openssl/err.h>
12
13
#include "ec_lcl.h"
14
15
#ifndef OPENSSL_NO_EC2M
16
17
/*-
18
 * Calculates and sets the affine coordinates of an EC_POINT from the given
19
 * compressed coordinates.  Uses algorithm 2.3.4 of SEC 1.
20
 * Note that the simple implementation only uses affine coordinates.
21
 *
22
 * The method is from the following publication:
23
 *
24
 *     Harper, Menezes, Vanstone:
25
 *     "Public-Key Cryptosystems with Very Small Key Lengths",
26
 *     EUROCRYPT '92, Springer-Verlag LNCS 658,
27
 *     published February 1993
28
 *
29
 * US Patents 6,141,420 and 6,618,483 (Vanstone, Mullin, Agnew) describe
30
 * the same method, but claim no priority date earlier than July 29, 1994
31
 * (and additionally fail to cite the EUROCRYPT '92 publication as prior art).
32
 */
33
int ec_GF2m_simple_set_compressed_coordinates(const EC_GROUP *group,
34
                                              EC_POINT *point,
35
                                              const BIGNUM *x_, int y_bit,
36
                                              BN_CTX *ctx)
37
0
{
38
0
    BN_CTX *new_ctx = NULL;
39
0
    BIGNUM *tmp, *x, *y, *z;
40
0
    int ret = 0, z0;
41
0
42
0
    /* clear error queue */
43
0
    ERR_clear_error();
44
0
45
0
    if (ctx == NULL) {
46
0
        ctx = new_ctx = BN_CTX_new();
47
0
        if (ctx == NULL)
48
0
            return 0;
49
0
    }
50
0
51
0
    y_bit = (y_bit != 0) ? 1 : 0;
52
0
53
0
    BN_CTX_start(ctx);
54
0
    tmp = BN_CTX_get(ctx);
55
0
    x = BN_CTX_get(ctx);
56
0
    y = BN_CTX_get(ctx);
57
0
    z = BN_CTX_get(ctx);
58
0
    if (z == NULL)
59
0
        goto err;
60
0
61
0
    if (!BN_GF2m_mod_arr(x, x_, group->poly))
62
0
        goto err;
63
0
    if (BN_is_zero(x)) {
64
0
        if (!BN_GF2m_mod_sqrt_arr(y, group->b, group->poly, ctx))
65
0
            goto err;
66
0
    } else {
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0
        if (!group->meth->field_sqr(group, tmp, x, ctx))
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0
            goto err;
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0
        if (!group->meth->field_div(group, tmp, group->b, tmp, ctx))
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0
            goto err;
71
0
        if (!BN_GF2m_add(tmp, group->a, tmp))
72
0
            goto err;
73
0
        if (!BN_GF2m_add(tmp, x, tmp))
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0
            goto err;
75
0
        if (!BN_GF2m_mod_solve_quad_arr(z, tmp, group->poly, ctx)) {
76
0
            unsigned long err = ERR_peek_last_error();
77
0
78
0
            if (ERR_GET_LIB(err) == ERR_LIB_BN
79
0
                && ERR_GET_REASON(err) == BN_R_NO_SOLUTION) {
80
0
                ERR_clear_error();
81
0
                ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
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0
                      EC_R_INVALID_COMPRESSED_POINT);
83
0
            } else
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0
                ECerr(EC_F_EC_GF2M_SIMPLE_SET_COMPRESSED_COORDINATES,
85
0
                      ERR_R_BN_LIB);
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0
            goto err;
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0
        }
88
0
        z0 = (BN_is_odd(z)) ? 1 : 0;
89
0
        if (!group->meth->field_mul(group, y, x, z, ctx))
90
0
            goto err;
91
0
        if (z0 != y_bit) {
92
0
            if (!BN_GF2m_add(y, y, x))
93
0
                goto err;
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0
        }
95
0
    }
96
0
97
0
    if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
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0
        goto err;
99
0
100
0
    ret = 1;
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0
102
0
 err:
103
0
    BN_CTX_end(ctx);
104
0
    BN_CTX_free(new_ctx);
105
0
    return ret;
106
0
}
107
108
/*
109
 * Converts an EC_POINT to an octet string. If buf is NULL, the encoded
110
 * length will be returned. If the length len of buf is smaller than required
111
 * an error will be returned.
112
 */
113
size_t ec_GF2m_simple_point2oct(const EC_GROUP *group, const EC_POINT *point,
114
                                point_conversion_form_t form,
115
                                unsigned char *buf, size_t len, BN_CTX *ctx)
116
0
{
117
0
    size_t ret;
118
0
    BN_CTX *new_ctx = NULL;
119
0
    int used_ctx = 0;
120
0
    BIGNUM *x, *y, *yxi;
121
0
    size_t field_len, i, skip;
122
0
123
0
    if ((form != POINT_CONVERSION_COMPRESSED)
124
0
        && (form != POINT_CONVERSION_UNCOMPRESSED)
125
0
        && (form != POINT_CONVERSION_HYBRID)) {
126
0
        ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_INVALID_FORM);
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0
        goto err;
128
0
    }
129
0
130
0
    if (EC_POINT_is_at_infinity(group, point)) {
131
0
        /* encodes to a single 0 octet */
132
0
        if (buf != NULL) {
133
0
            if (len < 1) {
134
0
                ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
135
0
                return 0;
136
0
            }
137
0
            buf[0] = 0;
138
0
        }
139
0
        return 1;
140
0
    }
141
0
142
0
    /* ret := required output buffer length */
143
0
    field_len = (EC_GROUP_get_degree(group) + 7) / 8;
144
0
    ret =
145
0
        (form ==
146
0
         POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
147
0
148
0
    /* if 'buf' is NULL, just return required length */
149
0
    if (buf != NULL) {
150
0
        if (len < ret) {
151
0
            ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
152
0
            goto err;
153
0
        }
154
0
155
0
        if (ctx == NULL) {
156
0
            ctx = new_ctx = BN_CTX_new();
157
0
            if (ctx == NULL)
158
0
                return 0;
159
0
        }
160
0
161
0
        BN_CTX_start(ctx);
162
0
        used_ctx = 1;
163
0
        x = BN_CTX_get(ctx);
164
0
        y = BN_CTX_get(ctx);
165
0
        yxi = BN_CTX_get(ctx);
166
0
        if (yxi == NULL)
167
0
            goto err;
168
0
169
0
        if (!EC_POINT_get_affine_coordinates(group, point, x, y, ctx))
170
0
            goto err;
171
0
172
0
        buf[0] = form;
173
0
        if ((form != POINT_CONVERSION_UNCOMPRESSED) && !BN_is_zero(x)) {
174
0
            if (!group->meth->field_div(group, yxi, y, x, ctx))
175
0
                goto err;
176
0
            if (BN_is_odd(yxi))
177
0
                buf[0]++;
178
0
        }
179
0
180
0
        i = 1;
181
0
182
0
        skip = field_len - BN_num_bytes(x);
183
0
        if (skip > field_len) {
184
0
            ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
185
0
            goto err;
186
0
        }
187
0
        while (skip > 0) {
188
0
            buf[i++] = 0;
189
0
            skip--;
190
0
        }
191
0
        skip = BN_bn2bin(x, buf + i);
192
0
        i += skip;
193
0
        if (i != 1 + field_len) {
194
0
            ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
195
0
            goto err;
196
0
        }
197
0
198
0
        if (form == POINT_CONVERSION_UNCOMPRESSED
199
0
            || form == POINT_CONVERSION_HYBRID) {
200
0
            skip = field_len - BN_num_bytes(y);
201
0
            if (skip > field_len) {
202
0
                ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
203
0
                goto err;
204
0
            }
205
0
            while (skip > 0) {
206
0
                buf[i++] = 0;
207
0
                skip--;
208
0
            }
209
0
            skip = BN_bn2bin(y, buf + i);
210
0
            i += skip;
211
0
        }
212
0
213
0
        if (i != ret) {
214
0
            ECerr(EC_F_EC_GF2M_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
215
0
            goto err;
216
0
        }
217
0
    }
218
0
219
0
    if (used_ctx)
220
0
        BN_CTX_end(ctx);
221
0
    BN_CTX_free(new_ctx);
222
0
    return ret;
223
0
224
0
 err:
225
0
    if (used_ctx)
226
0
        BN_CTX_end(ctx);
227
0
    BN_CTX_free(new_ctx);
228
0
    return 0;
229
0
}
230
231
/*
232
 * Converts an octet string representation to an EC_POINT. Note that the
233
 * simple implementation only uses affine coordinates.
234
 */
235
int ec_GF2m_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
236
                             const unsigned char *buf, size_t len,
237
                             BN_CTX *ctx)
238
0
{
239
0
    point_conversion_form_t form;
240
0
    int y_bit;
241
0
    BN_CTX *new_ctx = NULL;
242
0
    BIGNUM *x, *y, *yxi;
243
0
    size_t field_len, enc_len;
244
0
    int ret = 0;
245
0
246
0
    if (len == 0) {
247
0
        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL);
248
0
        return 0;
249
0
    }
250
0
    form = buf[0];
251
0
    y_bit = form & 1;
252
0
    form = form & ~1U;
253
0
    if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
254
0
        && (form != POINT_CONVERSION_UNCOMPRESSED)
255
0
        && (form != POINT_CONVERSION_HYBRID)) {
256
0
        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
257
0
        return 0;
258
0
    }
259
0
    if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
260
0
        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
261
0
        return 0;
262
0
    }
263
0
264
0
    if (form == 0) {
265
0
        if (len != 1) {
266
0
            ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
267
0
            return 0;
268
0
        }
269
0
270
0
        return EC_POINT_set_to_infinity(group, point);
271
0
    }
272
0
273
0
    field_len = (EC_GROUP_get_degree(group) + 7) / 8;
274
0
    enc_len =
275
0
        (form ==
276
0
         POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
277
0
278
0
    if (len != enc_len) {
279
0
        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
280
0
        return 0;
281
0
    }
282
0
283
0
    if (ctx == NULL) {
284
0
        ctx = new_ctx = BN_CTX_new();
285
0
        if (ctx == NULL)
286
0
            return 0;
287
0
    }
288
0
289
0
    BN_CTX_start(ctx);
290
0
    x = BN_CTX_get(ctx);
291
0
    y = BN_CTX_get(ctx);
292
0
    yxi = BN_CTX_get(ctx);
293
0
    if (yxi == NULL)
294
0
        goto err;
295
0
296
0
    if (!BN_bin2bn(buf + 1, field_len, x))
297
0
        goto err;
298
0
    if (BN_ucmp(x, group->field) >= 0) {
299
0
        ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
300
0
        goto err;
301
0
    }
302
0
303
0
    if (form == POINT_CONVERSION_COMPRESSED) {
304
0
        if (!EC_POINT_set_compressed_coordinates(group, point, x, y_bit, ctx))
305
0
            goto err;
306
0
    } else {
307
0
        if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
308
0
            goto err;
309
0
        if (BN_ucmp(y, group->field) >= 0) {
310
0
            ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
311
0
            goto err;
312
0
        }
313
0
        if (form == POINT_CONVERSION_HYBRID) {
314
0
            if (!group->meth->field_div(group, yxi, y, x, ctx))
315
0
                goto err;
316
0
            if (y_bit != BN_is_odd(yxi)) {
317
0
                ECerr(EC_F_EC_GF2M_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
318
0
                goto err;
319
0
            }
320
0
        }
321
0
322
0
        /*
323
0
         * EC_POINT_set_affine_coordinates is responsible for checking that
324
0
         * the point is on the curve.
325
0
         */
326
0
        if (!EC_POINT_set_affine_coordinates(group, point, x, y, ctx))
327
0
            goto err;
328
0
    }
329
0
330
0
    ret = 1;
331
0
332
0
 err:
333
0
    BN_CTX_end(ctx);
334
0
    BN_CTX_free(new_ctx);
335
0
    return ret;
336
0
}
337
#endif