/src/openssl/crypto/bn/bn_blind.c

Source
/*
 * Copyright 1998-2025 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

#include <openssl/opensslconf.h>
#include "internal/cryptlib.h"
#include "bn_local.h"

#define BN_BLINDING_COUNTER 32

struct bn_blinding_st {
    BIGNUM *A;
    BIGNUM *Ai;
    BIGNUM *e;
    BIGNUM *mod; /* just a reference */
    CRYPTO_THREAD_ID tid;
    int counter;
    unsigned long flags;
    BN_MONT_CTX *m_ctx;
    int (*bn_mod_exp)(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
        const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
    CRYPTO_RWLOCK *lock;
};

BN_BLINDING *BN_BLINDING_new(const BIGNUM *A, const BIGNUM *Ai, BIGNUM *mod)
{
    BN_BLINDING *ret = NULL;

    bn_check_top(mod);

    if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL)
        return NULL;

    ret->lock = CRYPTO_THREAD_lock_new();
    if (ret->lock == NULL) {
        ERR_raise(ERR_LIB_BN, ERR_R_CRYPTO_LIB);
        OPENSSL_free(ret);
        return NULL;
    }

    BN_BLINDING_set_current_thread(ret);

    if (A != NULL) {
        if ((ret->A = BN_dup(A)) == NULL)
            goto err;
    }

    if (Ai != NULL) {
        if ((ret->Ai = BN_dup(Ai)) == NULL)
            goto err;
    }

    /* save a copy of mod in the BN_BLINDING structure */
    if ((ret->mod = BN_dup(mod)) == NULL)
        goto err;

    if (BN_get_flags(mod, BN_FLG_CONSTTIME) != 0)
        BN_set_flags(ret->mod, BN_FLG_CONSTTIME);

    /*
     * Set the counter to the special value -1 to indicate that this is
     * never-used fresh blinding that does not need updating before first
     * use.
     */
    ret->counter = -1;

    return ret;

err:
    BN_BLINDING_free(ret);
    return NULL;
}

void BN_BLINDING_free(BN_BLINDING *r)
{
    if (r == NULL)
        return;
    BN_free(r->A);
    BN_free(r->Ai);
    BN_free(r->e);
    BN_free(r->mod);
    CRYPTO_THREAD_lock_free(r->lock);
    OPENSSL_free(r);
}

int BN_BLINDING_update(BN_BLINDING *b, BN_CTX *ctx)
{
    int ret = 0;

    if ((b->A == NULL) || (b->Ai == NULL)) {
        ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
        goto err;
    }

    if (b->counter == -1)
        b->counter = 0;

    if (++b->counter == BN_BLINDING_COUNTER && b->e != NULL && !(b->flags & BN_BLINDING_NO_RECREATE)) {
        /* re-create blinding parameters */
        if (!BN_BLINDING_create_param(b, NULL, NULL, ctx, NULL, NULL))
            goto err;
    } else if (!(b->flags & BN_BLINDING_NO_UPDATE)) {
        if (b->m_ctx != NULL) {
            if (!bn_mul_mont_fixed_top(b->Ai, b->Ai, b->Ai, b->m_ctx, ctx)
                || !bn_mul_mont_fixed_top(b->A, b->A, b->A, b->m_ctx, ctx))
                goto err;
        } else {
            if (!BN_mod_mul(b->Ai, b->Ai, b->Ai, b->mod, ctx)
                || !BN_mod_mul(b->A, b->A, b->A, b->mod, ctx))
                goto err;
        }
    }

    ret = 1;
err:
    if (b->counter == BN_BLINDING_COUNTER)
        b->counter = 0;
    return ret;
}

int BN_BLINDING_convert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
{
    return BN_BLINDING_convert_ex(n, NULL, b, ctx);
}

int BN_BLINDING_convert_ex(BIGNUM *n, BIGNUM *r, BN_BLINDING *b, BN_CTX *ctx)
{
    int ret = 1;

    bn_check_top(n);

    if ((b->A == NULL) || (b->Ai == NULL)) {
        ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
        return 0;
    }

    if (b->counter == -1)
        /* Fresh blinding, doesn't need updating. */
        b->counter = 0;
    else if (!BN_BLINDING_update(b, ctx))
        return 0;

    if (r != NULL && (BN_copy(r, b->Ai) == NULL))
        return 0;

    if (b->m_ctx != NULL)
        ret = BN_mod_mul_montgomery(n, n, b->A, b->m_ctx, ctx);
    else
        ret = BN_mod_mul(n, n, b->A, b->mod, ctx);

    return ret;
}

int BN_BLINDING_invert(BIGNUM *n, BN_BLINDING *b, BN_CTX *ctx)
{
    return BN_BLINDING_invert_ex(n, NULL, b, ctx);
}

int BN_BLINDING_invert_ex(BIGNUM *n, const BIGNUM *r, BN_BLINDING *b,
    BN_CTX *ctx)
{
    int ret;

    bn_check_top(n);

    if (r == NULL && (r = b->Ai) == NULL) {
        ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
        return 0;
    }

    if (b->m_ctx != NULL) {
        /* ensure that BN_mod_mul_montgomery takes pre-defined path */
        if (n->dmax >= r->top) {
            size_t i, rtop = r->top, ntop = n->top;
            BN_ULONG mask;

            for (i = 0; i < rtop; i++) {
                mask = (BN_ULONG)0 - ((i - ntop) >> (8 * sizeof(i) - 1));
                n->d[i] &= mask;
            }
            mask = (BN_ULONG)0 - ((rtop - ntop) >> (8 * sizeof(ntop) - 1));
            /* always true, if (rtop >= ntop) n->top = r->top; */
            n->top = (int)((rtop & ~mask) | (ntop & mask));
            n->flags |= (BN_FLG_FIXED_TOP & ~mask);
        }
        ret = bn_mul_mont_fixed_top(n, n, r, b->m_ctx, ctx);
        bn_correct_top_consttime(n);
    } else {
        ret = BN_mod_mul(n, n, r, b->mod, ctx);
    }

    bn_check_top(n);
    return ret;
}

int BN_BLINDING_is_current_thread(BN_BLINDING *b)
{
    return CRYPTO_THREAD_compare_id(CRYPTO_THREAD_get_current_id(), b->tid);
}

void BN_BLINDING_set_current_thread(BN_BLINDING *b)
{
    b->tid = CRYPTO_THREAD_get_current_id();
}

int BN_BLINDING_lock(BN_BLINDING *b)
{
    return CRYPTO_THREAD_write_lock(b->lock);
}

int BN_BLINDING_unlock(BN_BLINDING *b)
{
    return CRYPTO_THREAD_unlock(b->lock);
}

unsigned long BN_BLINDING_get_flags(const BN_BLINDING *b)
{
    return b->flags;
}

void BN_BLINDING_set_flags(BN_BLINDING *b, unsigned long flags)
{
    b->flags = flags;
}

BN_BLINDING *BN_BLINDING_create_param(BN_BLINDING *b,
    const BIGNUM *e, BIGNUM *m, BN_CTX *ctx,
    int (*bn_mod_exp)(BIGNUM *r,
        const BIGNUM *a,
        const BIGNUM *p,
        const BIGNUM *m,
        BN_CTX *ctx,
        BN_MONT_CTX *m_ctx),
    BN_MONT_CTX *m_ctx)
{
    int retry_counter = 32;
    BN_BLINDING *ret = NULL;

    if (b == NULL)
        ret = BN_BLINDING_new(NULL, NULL, m);
    else
        ret = b;

    if (ret == NULL)
        goto err;

    if (ret->A == NULL && (ret->A = BN_new()) == NULL)
        goto err;
    if (ret->Ai == NULL && (ret->Ai = BN_new()) == NULL)
        goto err;

    if (e != NULL) {
        BN_free(ret->e);
        ret->e = BN_dup(e);
    }
    if (ret->e == NULL)
        goto err;

    if (bn_mod_exp != NULL)
        ret->bn_mod_exp = bn_mod_exp;
    if (m_ctx != NULL)
        ret->m_ctx = m_ctx;

    do {
        int rv;
        if (!BN_priv_rand_range_ex(ret->A, ret->mod, 0, ctx))
            goto err;
        if (int_bn_mod_inverse(ret->Ai, ret->A, ret->mod, ctx, &rv))
            break;

        /*
         * this should almost never happen for good RSA keys
         */
        if (!rv)
            goto err;

        if (retry_counter-- == 0) {
            ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
            goto err;
        }
    } while (1);

    if (ret->bn_mod_exp != NULL && ret->m_ctx != NULL) {
        if (!ret->bn_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx, ret->m_ctx))
            goto err;
    } else {
        if (!BN_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx))
            goto err;
    }

    if (ret->m_ctx != NULL) {
        if (!bn_to_mont_fixed_top(ret->Ai, ret->Ai, ret->m_ctx, ctx)
            || !bn_to_mont_fixed_top(ret->A, ret->A, ret->m_ctx, ctx))
            goto err;
    }

    return ret;
err:
    if (b == NULL) {
        BN_BLINDING_free(ret);
        ret = NULL;
    }

    return ret;
}

Coverage Report

Created: 2025-12-10 06:24

Line	Count	Source
1		/*
2		* Copyright 1998-2025 The OpenSSL Project Authors. All Rights Reserved.
3		*
4		* Licensed under the Apache License 2.0 (the "License"). You may not use
5		* this file except in compliance with the License. You can obtain a copy
6		* in the file LICENSE in the source distribution or at
7		* https://www.openssl.org/source/license.html
8		*/
9
10		#include <openssl/opensslconf.h>
11		#include "internal/cryptlib.h"
12		#include "bn_local.h"
13
14	0	#define BN_BLINDING_COUNTER 32
15
16		struct bn_blinding_st {
17		BIGNUM *A;
18		BIGNUM *Ai;
19		BIGNUM *e;
20		BIGNUM mod; / just a reference */
21		CRYPTO_THREAD_ID tid;
22		int counter;
23		unsigned long flags;
24		BN_MONT_CTX *m_ctx;
25		int (bn_mod_exp)(BIGNUM r, const BIGNUM a, const BIGNUM p,
26		const BIGNUM m, BN_CTX ctx, BN_MONT_CTX *m_ctx);
27		CRYPTO_RWLOCK *lock;
28		};
29
30		BN_BLINDING BN_BLINDING_new(const BIGNUM A, const BIGNUM Ai, BIGNUM mod)
31	0	{
32	0	BN_BLINDING *ret = NULL;
33
34	0	bn_check_top(mod);
35
36	0	if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL)
37	0	return NULL;
38
39	0	ret->lock = CRYPTO_THREAD_lock_new();
40	0	if (ret->lock == NULL) {
41	0	ERR_raise(ERR_LIB_BN, ERR_R_CRYPTO_LIB);
42	0	OPENSSL_free(ret);
43	0	return NULL;
44	0	}
45
46	0	BN_BLINDING_set_current_thread(ret);
47
48	0	if (A != NULL) {
49	0	if ((ret->A = BN_dup(A)) == NULL)
50	0	goto err;
51	0	}
52
53	0	if (Ai != NULL) {
54	0	if ((ret->Ai = BN_dup(Ai)) == NULL)
55	0	goto err;
56	0	}
57
58		/* save a copy of mod in the BN_BLINDING structure */
59	0	if ((ret->mod = BN_dup(mod)) == NULL)
60	0	goto err;
61
62	0	if (BN_get_flags(mod, BN_FLG_CONSTTIME) != 0)
63	0	BN_set_flags(ret->mod, BN_FLG_CONSTTIME);
64
65		/*
66		* Set the counter to the special value -1 to indicate that this is
67		* never-used fresh blinding that does not need updating before first
68		* use.
69		*/
70	0	ret->counter = -1;
71
72	0	return ret;
73
74	0	err:
75	0	BN_BLINDING_free(ret);
76	0	return NULL;
77	0	}
78
79		void BN_BLINDING_free(BN_BLINDING *r)
80	0	{
81	0	if (r == NULL)
82	0	return;
83	0	BN_free(r->A);
84	0	BN_free(r->Ai);
85	0	BN_free(r->e);
86	0	BN_free(r->mod);
87	0	CRYPTO_THREAD_lock_free(r->lock);
88	0	OPENSSL_free(r);
89	0	}
90
91		int BN_BLINDING_update(BN_BLINDING b, BN_CTX ctx)
92	0	{
93	0	int ret = 0;
94
95	0	if ((b->A == NULL) \|\| (b->Ai == NULL)) {
96	0	ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
97	0	goto err;
98	0	}
99
100	0	if (b->counter == -1)
101	0	b->counter = 0;
102
103	0	if (++b->counter == BN_BLINDING_COUNTER && b->e != NULL && !(b->flags & BN_BLINDING_NO_RECREATE)) {
104		/* re-create blinding parameters */
105	0	if (!BN_BLINDING_create_param(b, NULL, NULL, ctx, NULL, NULL))
106	0	goto err;
107	0	} else if (!(b->flags & BN_BLINDING_NO_UPDATE)) {
108	0	if (b->m_ctx != NULL) {
109	0	if (!bn_mul_mont_fixed_top(b->Ai, b->Ai, b->Ai, b->m_ctx, ctx)
110	0	\|\| !bn_mul_mont_fixed_top(b->A, b->A, b->A, b->m_ctx, ctx))
111	0	goto err;
112	0	} else {
113	0	if (!BN_mod_mul(b->Ai, b->Ai, b->Ai, b->mod, ctx)
114	0	\|\| !BN_mod_mul(b->A, b->A, b->A, b->mod, ctx))
115	0	goto err;
116	0	}
117	0	}
118
119	0	ret = 1;
120	0	err:
121	0	if (b->counter == BN_BLINDING_COUNTER)
122	0	b->counter = 0;
123	0	return ret;
124	0	}
125
126		int BN_BLINDING_convert(BIGNUM n, BN_BLINDING b, BN_CTX *ctx)
127	0	{
128	0	return BN_BLINDING_convert_ex(n, NULL, b, ctx);
129	0	}
130
131		int BN_BLINDING_convert_ex(BIGNUM n, BIGNUM r, BN_BLINDING b, BN_CTX ctx)
132	0	{
133	0	int ret = 1;
134
135	0	bn_check_top(n);
136
137	0	if ((b->A == NULL) \|\| (b->Ai == NULL)) {
138	0	ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
139	0	return 0;
140	0	}
141
142	0	if (b->counter == -1)
143		/* Fresh blinding, doesn't need updating. */
144	0	b->counter = 0;
145	0	else if (!BN_BLINDING_update(b, ctx))
146	0	return 0;
147
148	0	if (r != NULL && (BN_copy(r, b->Ai) == NULL))
149	0	return 0;
150
151	0	if (b->m_ctx != NULL)
152	0	ret = BN_mod_mul_montgomery(n, n, b->A, b->m_ctx, ctx);
153	0	else
154	0	ret = BN_mod_mul(n, n, b->A, b->mod, ctx);
155
156	0	return ret;
157	0	}
158
159		int BN_BLINDING_invert(BIGNUM n, BN_BLINDING b, BN_CTX *ctx)
160	0	{
161	0	return BN_BLINDING_invert_ex(n, NULL, b, ctx);
162	0	}
163
164		int BN_BLINDING_invert_ex(BIGNUM n, const BIGNUM r, BN_BLINDING *b,
165		BN_CTX *ctx)
166	0	{
167	0	int ret;
168
169	0	bn_check_top(n);
170
171	0	if (r == NULL && (r = b->Ai) == NULL) {
172	0	ERR_raise(ERR_LIB_BN, BN_R_NOT_INITIALIZED);
173	0	return 0;
174	0	}
175
176	0	if (b->m_ctx != NULL) {
177		/* ensure that BN_mod_mul_montgomery takes pre-defined path */
178	0	if (n->dmax >= r->top) {
179	0	size_t i, rtop = r->top, ntop = n->top;
180	0	BN_ULONG mask;
181
182	0	for (i = 0; i < rtop; i++) {
183	0	mask = (BN_ULONG)0 - ((i - ntop) >> (8 * sizeof(i) - 1));
184	0	n->d[i] &= mask;
185	0	}
186	0	mask = (BN_ULONG)0 - ((rtop - ntop) >> (8 * sizeof(ntop) - 1));
187		/* always true, if (rtop >= ntop) n->top = r->top; */
188	0	n->top = (int)((rtop & ~mask) \| (ntop & mask));
189	0	n->flags \|= (BN_FLG_FIXED_TOP & ~mask);
190	0	}
191	0	ret = bn_mul_mont_fixed_top(n, n, r, b->m_ctx, ctx);
192	0	bn_correct_top_consttime(n);
193	0	} else {
194	0	ret = BN_mod_mul(n, n, r, b->mod, ctx);
195	0	}
196
197	0	bn_check_top(n);
198	0	return ret;
199	0	}
200
201		int BN_BLINDING_is_current_thread(BN_BLINDING *b)
202	0	{
203	0	return CRYPTO_THREAD_compare_id(CRYPTO_THREAD_get_current_id(), b->tid);
204	0	}
205
206		void BN_BLINDING_set_current_thread(BN_BLINDING *b)
207	0	{
208	0	b->tid = CRYPTO_THREAD_get_current_id();
209	0	}
210
211		int BN_BLINDING_lock(BN_BLINDING *b)
212	0	{
213	0	return CRYPTO_THREAD_write_lock(b->lock);
214	0	}
215
216		int BN_BLINDING_unlock(BN_BLINDING *b)
217	0	{
218	0	return CRYPTO_THREAD_unlock(b->lock);
219	0	}
220
221		unsigned long BN_BLINDING_get_flags(const BN_BLINDING *b)
222	0	{
223	0	return b->flags;
224	0	}
225
226		void BN_BLINDING_set_flags(BN_BLINDING *b, unsigned long flags)
227	0	{
228	0	b->flags = flags;
229	0	}
230
231		BN_BLINDING BN_BLINDING_create_param(BN_BLINDING b,
232		const BIGNUM e, BIGNUM m, BN_CTX *ctx,
233		int (bn_mod_exp)(BIGNUM r,
234		const BIGNUM *a,
235		const BIGNUM *p,
236		const BIGNUM *m,
237		BN_CTX *ctx,
238		BN_MONT_CTX *m_ctx),
239		BN_MONT_CTX *m_ctx)
240	0	{
241	0	int retry_counter = 32;
242	0	BN_BLINDING *ret = NULL;
243
244	0	if (b == NULL)
245	0	ret = BN_BLINDING_new(NULL, NULL, m);
246	0	else
247	0	ret = b;
248
249	0	if (ret == NULL)
250	0	goto err;
251
252	0	if (ret->A == NULL && (ret->A = BN_new()) == NULL)
253	0	goto err;
254	0	if (ret->Ai == NULL && (ret->Ai = BN_new()) == NULL)
255	0	goto err;
256
257	0	if (e != NULL) {
258	0	BN_free(ret->e);
259	0	ret->e = BN_dup(e);
260	0	}
261	0	if (ret->e == NULL)
262	0	goto err;
263
264	0	if (bn_mod_exp != NULL)
265	0	ret->bn_mod_exp = bn_mod_exp;
266	0	if (m_ctx != NULL)
267	0	ret->m_ctx = m_ctx;
268
269	0	do {
270	0	int rv;
271	0	if (!BN_priv_rand_range_ex(ret->A, ret->mod, 0, ctx))
272	0	goto err;
273	0	if (int_bn_mod_inverse(ret->Ai, ret->A, ret->mod, ctx, &rv))
274	0	break;
275
276		/*
277		* this should almost never happen for good RSA keys
278		*/
279	0	if (!rv)
280	0	goto err;
281
282	0	if (retry_counter-- == 0) {
283	0	ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
284	0	goto err;
285	0	}
286	0	} while (1);
287
288	0	if (ret->bn_mod_exp != NULL && ret->m_ctx != NULL) {
289	0	if (!ret->bn_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx, ret->m_ctx))
290	0	goto err;
291	0	} else {
292	0	if (!BN_mod_exp(ret->A, ret->A, ret->e, ret->mod, ctx))
293	0	goto err;
294	0	}
295
296	0	if (ret->m_ctx != NULL) {
297	0	if (!bn_to_mont_fixed_top(ret->Ai, ret->Ai, ret->m_ctx, ctx)
298	0	\|\| !bn_to_mont_fixed_top(ret->A, ret->A, ret->m_ctx, ctx))
299	0	goto err;
300	0	}
301
302	0	return ret;
303	0	err:
304	0	if (b == NULL) {
305	0	BN_BLINDING_free(ret);
306	0	ret = NULL;
307	0	}
308
309	0	return ret;
310	0	}