/src/openssl30/crypto/dh/dh_key.c

Source (jump to first uncovered line)
/*
 * Copyright 1995-2022 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
 */

/*
 * DH low level APIs are deprecated for public use, but still ok for
 * internal use.
 */
#include "internal/deprecated.h"

#include <stdio.h>
#include "internal/cryptlib.h"
#include "dh_local.h"
#include "crypto/bn.h"
#include "crypto/dh.h"
#include "crypto/security_bits.h"

#ifdef FIPS_MODULE
# define MIN_STRENGTH 112
#else
# define MIN_STRENGTH 80
#endif

static int generate_key(DH *dh);
static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
                         const BIGNUM *a, const BIGNUM *p,
                         const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
static int dh_init(DH *dh);
static int dh_finish(DH *dh);

/*
 * See SP800-56Ar3 Section 5.7.1.1
 * Finite Field Cryptography Diffie-Hellman (FFC DH) Primitive
 */
int ossl_dh_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
{
    BN_CTX *ctx = NULL;
    BN_MONT_CTX *mont = NULL;
    BIGNUM *z = NULL, *pminus1;
    int ret = -1;

    if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS) {
        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
        goto err;
    }

    if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS) {
        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
        return 0;
    }

    ctx = BN_CTX_new_ex(dh->libctx);
    if (ctx == NULL)
        goto err;
    BN_CTX_start(ctx);
    pminus1 = BN_CTX_get(ctx);
    z = BN_CTX_get(ctx);
    if (z == NULL)
        goto err;

    if (dh->priv_key == NULL) {
        ERR_raise(ERR_LIB_DH, DH_R_NO_PRIVATE_VALUE);
        goto err;
    }

    if (dh->flags & DH_FLAG_CACHE_MONT_P) {
        mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
                                      dh->lock, dh->params.p, ctx);
        BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
        if (!mont)
            goto err;
    }

    /* (Step 1) Z = pub_key^priv_key mod p */
    if (!dh->meth->bn_mod_exp(dh, z, pub_key, dh->priv_key, dh->params.p, ctx,
                              mont)) {
        ERR_raise(ERR_LIB_DH, ERR_R_BN_LIB);
        goto err;
    }

    /* (Step 2) Error if z <= 1 or z = p - 1 */
    if (BN_copy(pminus1, dh->params.p) == NULL
        || !BN_sub_word(pminus1, 1)
        || BN_cmp(z, BN_value_one()) <= 0
        || BN_cmp(z, pminus1) == 0) {
        ERR_raise(ERR_LIB_DH, DH_R_INVALID_SECRET);
        goto err;
    }

    /* return the padded key, i.e. same number of bytes as the modulus */
    ret = BN_bn2binpad(z, key, BN_num_bytes(dh->params.p));
 err:
    BN_clear(z); /* (Step 2) destroy intermediate values */
    BN_CTX_end(ctx);
    BN_CTX_free(ctx);
    return ret;
}

/*-
 * NB: This function is inherently not constant time due to the
 * RFC 5246 (8.1.2) padding style that strips leading zero bytes.
 */
int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
{
    int ret = 0, i;
    volatile size_t npad = 0, mask = 1;

    /* compute the key; ret is constant unless compute_key is external */
#ifdef FIPS_MODULE
    ret = ossl_dh_compute_key(key, pub_key, dh);
#else
    ret = dh->meth->compute_key(key, pub_key, dh);
#endif
    if (ret <= 0)
        return ret;

    /* count leading zero bytes, yet still touch all bytes */
    for (i = 0; i < ret; i++) {
        mask &= !key[i];
        npad += mask;
    }

    /* unpad key */
    ret -= npad;
    /* key-dependent memory access, potentially leaking npad / ret */
    memmove(key, key + npad, ret);
    /* key-dependent memory access, potentially leaking npad / ret */
    memset(key + ret, 0, npad);

    return ret;
}

int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
{
    int rv, pad;

    /* rv is constant unless compute_key is external */
#ifdef FIPS_MODULE
    rv = ossl_dh_compute_key(key, pub_key, dh);
#else
    rv = dh->meth->compute_key(key, pub_key, dh);
#endif
    if (rv <= 0)
        return rv;
    pad = BN_num_bytes(dh->params.p) - rv;
    /* pad is constant (zero) unless compute_key is external */
    if (pad > 0) {
        memmove(key + pad, key, rv);
        memset(key, 0, pad);
    }
    return rv + pad;
}

static DH_METHOD dh_ossl = {
    "OpenSSL DH Method",
    generate_key,
    ossl_dh_compute_key,
    dh_bn_mod_exp,
    dh_init,
    dh_finish,
    DH_FLAG_FIPS_METHOD,
    NULL,
    NULL
};

static const DH_METHOD *default_DH_method = &dh_ossl;

const DH_METHOD *DH_OpenSSL(void)
{
    return &dh_ossl;
}

const DH_METHOD *DH_get_default_method(void)
{
    return default_DH_method;
}

static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
                         const BIGNUM *a, const BIGNUM *p,
                         const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
{
    return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
}

static int dh_init(DH *dh)
{
    dh->flags |= DH_FLAG_CACHE_MONT_P;
    ossl_ffc_params_init(&dh->params);
    dh->dirty_cnt++;
    return 1;
}

static int dh_finish(DH *dh)
{
    BN_MONT_CTX_free(dh->method_mont_p);
    return 1;
}

#ifndef FIPS_MODULE
void DH_set_default_method(const DH_METHOD *meth)
{
    default_DH_method = meth;
}
#endif /* FIPS_MODULE */

int DH_generate_key(DH *dh)
{
#ifdef FIPS_MODULE
    return generate_key(dh);
#else
    return dh->meth->generate_key(dh);
#endif
}

int ossl_dh_generate_public_key(BN_CTX *ctx, const DH *dh,
                                const BIGNUM *priv_key, BIGNUM *pub_key)
{
    int ret = 0;
    BIGNUM *prk = BN_new();
    BN_MONT_CTX *mont = NULL;

    if (prk == NULL)
        return 0;

    if (dh->flags & DH_FLAG_CACHE_MONT_P) {
        /*
         * We take the input DH as const, but we lie, because in some cases we
         * want to get a hold of its Montgomery context.
         *
         * We cast to remove the const qualifier in this case, it should be
         * fine...
         */
        BN_MONT_CTX **pmont = (BN_MONT_CTX **)&dh->method_mont_p;

        mont = BN_MONT_CTX_set_locked(pmont, dh->lock, dh->params.p, ctx);
        if (mont == NULL)
            goto err;
    }
    BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);

    /* pub_key = g^priv_key mod p */
    if (!dh->meth->bn_mod_exp(dh, pub_key, dh->params.g, prk, dh->params.p,
                              ctx, mont))
        goto err;
    ret = 1;
err:
    BN_clear_free(prk);
    return ret;
}

static int generate_key(DH *dh)
{
    int ok = 0;
    int generate_new_key = 0;
#ifndef FIPS_MODULE
    unsigned l;
#endif
    BN_CTX *ctx = NULL;
    BIGNUM *pub_key = NULL, *priv_key = NULL;

    if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS) {
        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
        return 0;
    }

    if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS) {
        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
        return 0;
    }

    ctx = BN_CTX_new_ex(dh->libctx);
    if (ctx == NULL)
        goto err;

    if (dh->priv_key == NULL) {
        priv_key = BN_secure_new();
        if (priv_key == NULL)
            goto err;
        generate_new_key = 1;
    } else {
        priv_key = dh->priv_key;
    }

    if (dh->pub_key == NULL) {
        pub_key = BN_new();
        if (pub_key == NULL)
            goto err;
    } else {
        pub_key = dh->pub_key;
    }
    if (generate_new_key) {
        /* Is it an approved safe prime ?*/
        if (DH_get_nid(dh) != NID_undef) {
            int max_strength =
                    ossl_ifc_ffc_compute_security_bits(BN_num_bits(dh->params.p));

            if (dh->params.q == NULL
                || dh->length > BN_num_bits(dh->params.q))
                goto err;
            /* dh->length = maximum bit length of generated private key */
            if (!ossl_ffc_generate_private_key(ctx, &dh->params, dh->length,
                                               max_strength, priv_key))
                goto err;
        } else {
#ifdef FIPS_MODULE
            if (dh->params.q == NULL)
                goto err;
#else
            if (dh->params.q == NULL) {
                /* secret exponent length, must satisfy 2^(l-1) <= p */
                if (dh->length != 0
                    && dh->length >= BN_num_bits(dh->params.p))
                    goto err;
                l = dh->length ? dh->length : BN_num_bits(dh->params.p) - 1;
                if (!BN_priv_rand_ex(priv_key, l, BN_RAND_TOP_ONE,
                                     BN_RAND_BOTTOM_ANY, 0, ctx))
                    goto err;
                /*
                 * We handle just one known case where g is a quadratic non-residue:
                 * for g = 2: p % 8 == 3
                 */
                if (BN_is_word(dh->params.g, DH_GENERATOR_2)
                    && !BN_is_bit_set(dh->params.p, 2)) {
                    /* clear bit 0, since it won't be a secret anyway */
                    if (!BN_clear_bit(priv_key, 0))
                        goto err;
                }
            } else
#endif
            {
                /* Do a partial check for invalid p, q, g */
                if (!ossl_ffc_params_simple_validate(dh->libctx, &dh->params,
                                                     FFC_PARAM_TYPE_DH, NULL))
                    goto err;
                /*
                 * For FFC FIPS 186-4 keygen
                 * security strength s = 112,
                 * Max Private key size N = len(q)
                 */
                if (!ossl_ffc_generate_private_key(ctx, &dh->params,
                                                   BN_num_bits(dh->params.q),
                                                   MIN_STRENGTH,
                                                   priv_key))
                    goto err;
            }
        }
    }

    if (!ossl_dh_generate_public_key(ctx, dh, priv_key, pub_key))
        goto err;

    dh->pub_key = pub_key;
    dh->priv_key = priv_key;
    dh->dirty_cnt++;
    ok = 1;
 err:
    if (ok != 1)
        ERR_raise(ERR_LIB_DH, ERR_R_BN_LIB);

    if (pub_key != dh->pub_key)
        BN_free(pub_key);
    if (priv_key != dh->priv_key)
        BN_free(priv_key);
    BN_CTX_free(ctx);
    return ok;
}

int ossl_dh_buf2key(DH *dh, const unsigned char *buf, size_t len)
{
    int err_reason = DH_R_BN_ERROR;
    BIGNUM *pubkey = NULL;
    const BIGNUM *p;
    int ret;

    if ((pubkey = BN_bin2bn(buf, len, NULL)) == NULL)
        goto err;
    DH_get0_pqg(dh, &p, NULL, NULL);
    if (p == NULL || BN_num_bytes(p) == 0) {
        err_reason = DH_R_NO_PARAMETERS_SET;
        goto err;
    }
    /* Prevent small subgroup attacks per RFC 8446 Section 4.2.8.1 */
    if (!ossl_dh_check_pub_key_partial(dh, pubkey, &ret)) {
        err_reason = DH_R_INVALID_PUBKEY;
        goto err;
    }
    if (DH_set0_key(dh, pubkey, NULL) != 1)
        goto err;
    return 1;
err:
    ERR_raise(ERR_LIB_DH, err_reason);
    BN_free(pubkey);
    return 0;
}

size_t ossl_dh_key2buf(const DH *dh, unsigned char **pbuf_out, size_t size,
                       int alloc)
{
    const BIGNUM *pubkey;
    unsigned char *pbuf = NULL;
    const BIGNUM *p;
    int p_size;

    DH_get0_pqg(dh, &p, NULL, NULL);
    DH_get0_key(dh, &pubkey, NULL);
    if (p == NULL || pubkey == NULL
            || (p_size = BN_num_bytes(p)) == 0
            || BN_num_bytes(pubkey) == 0) {
        ERR_raise(ERR_LIB_DH, DH_R_INVALID_PUBKEY);
        return 0;
    }
    if (pbuf_out != NULL && (alloc || *pbuf_out != NULL)) {
        if (!alloc) {
            if (size >= (size_t)p_size)
                pbuf = *pbuf_out;
        } else {
            pbuf = OPENSSL_malloc(p_size);
        }

        if (pbuf == NULL) {
            ERR_raise(ERR_LIB_DH, ERR_R_MALLOC_FAILURE);
            return 0;
        }
        /*
         * As per Section 4.2.8.1 of RFC 8446 left pad public
         * key with zeros to the size of p
         */
        if (BN_bn2binpad(pubkey, pbuf, p_size) < 0) {
            if (alloc)
                OPENSSL_free(pbuf);
            ERR_raise(ERR_LIB_DH, DH_R_BN_ERROR);
            return 0;
        }
        *pbuf_out = pbuf;
    }
    return p_size;
}

Coverage Report

Created: 2023-06-08 06:40

Line	Count	Source (jump to first uncovered line)
1		/*
2		* Copyright 1995-2022 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		/*
11		* DH low level APIs are deprecated for public use, but still ok for
12		* internal use.
13		*/
14		#include "internal/deprecated.h"
15
16		#include <stdio.h>
17		#include "internal/cryptlib.h"
18		#include "dh_local.h"
19		#include "crypto/bn.h"
20		#include "crypto/dh.h"
21		#include "crypto/security_bits.h"
22
23		#ifdef FIPS_MODULE
24		# define MIN_STRENGTH 112
25		#else
26	0	# define MIN_STRENGTH 80
27		#endif
28
29		static int generate_key(DH *dh);
30		static int dh_bn_mod_exp(const DH dh, BIGNUM r,
31		const BIGNUM a, const BIGNUM p,
32		const BIGNUM m, BN_CTX ctx, BN_MONT_CTX *m_ctx);
33		static int dh_init(DH *dh);
34		static int dh_finish(DH *dh);
35
36		/*
37		* See SP800-56Ar3 Section 5.7.1.1
38		* Finite Field Cryptography Diffie-Hellman (FFC DH) Primitive
39		*/
40		int ossl_dh_compute_key(unsigned char key, const BIGNUM pub_key, DH *dh)
41	0	{
42	0	BN_CTX *ctx = NULL;
43	0	BN_MONT_CTX *mont = NULL;
44	0	BIGNUM z = NULL, pminus1;
45	0	int ret = -1;
46
47	0	if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS) {
48	0	ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
49	0	goto err;
50	0	}
51
52	0	if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS) {
53	0	ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
54	0	return 0;
55	0	}
56
57	0	ctx = BN_CTX_new_ex(dh->libctx);
58	0	if (ctx == NULL)
59	0	goto err;
60	0	BN_CTX_start(ctx);
61	0	pminus1 = BN_CTX_get(ctx);
62	0	z = BN_CTX_get(ctx);
63	0	if (z == NULL)
64	0	goto err;
65
66	0	if (dh->priv_key == NULL) {
67	0	ERR_raise(ERR_LIB_DH, DH_R_NO_PRIVATE_VALUE);
68	0	goto err;
69	0	}
70
71	0	if (dh->flags & DH_FLAG_CACHE_MONT_P) {
72	0	mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
73	0	dh->lock, dh->params.p, ctx);
74	0	BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
75	0	if (!mont)
76	0	goto err;
77	0	}
78
79		/* (Step 1) Z = pub_key^priv_key mod p */
80	0	if (!dh->meth->bn_mod_exp(dh, z, pub_key, dh->priv_key, dh->params.p, ctx,
81	0	mont)) {
82	0	ERR_raise(ERR_LIB_DH, ERR_R_BN_LIB);
83	0	goto err;
84	0	}
85
86		/* (Step 2) Error if z <= 1 or z = p - 1 */
87	0	if (BN_copy(pminus1, dh->params.p) == NULL
88	0	\|\| !BN_sub_word(pminus1, 1)
89	0	\|\| BN_cmp(z, BN_value_one()) <= 0
90	0	\|\| BN_cmp(z, pminus1) == 0) {
91	0	ERR_raise(ERR_LIB_DH, DH_R_INVALID_SECRET);
92	0	goto err;
93	0	}
94
95		/* return the padded key, i.e. same number of bytes as the modulus */
96	0	ret = BN_bn2binpad(z, key, BN_num_bytes(dh->params.p));
97	0	err:
98	0	BN_clear(z); /* (Step 2) destroy intermediate values */
99	0	BN_CTX_end(ctx);
100	0	BN_CTX_free(ctx);
101	0	return ret;
102	0	}
103
104		/*-
105		* NB: This function is inherently not constant time due to the
106		* RFC 5246 (8.1.2) padding style that strips leading zero bytes.
107		*/
108		int DH_compute_key(unsigned char key, const BIGNUM pub_key, DH *dh)
109	0	{
110	0	int ret = 0, i;
111	0	volatile size_t npad = 0, mask = 1;
112
113		/* compute the key; ret is constant unless compute_key is external */
114		#ifdef FIPS_MODULE
115		ret = ossl_dh_compute_key(key, pub_key, dh);
116		#else
117	0	ret = dh->meth->compute_key(key, pub_key, dh);
118	0	#endif
119	0	if (ret <= 0)
120	0	return ret;
121
122		/* count leading zero bytes, yet still touch all bytes */
123	0	for (i = 0; i < ret; i++) {
124	0	mask &= !key[i];
125	0	npad += mask;
126	0	}
127
128		/* unpad key */
129	0	ret -= npad;
130		/* key-dependent memory access, potentially leaking npad / ret */
131	0	memmove(key, key + npad, ret);
132		/* key-dependent memory access, potentially leaking npad / ret */
133	0	memset(key + ret, 0, npad);
134
135	0	return ret;
136	0	}
137
138		int DH_compute_key_padded(unsigned char key, const BIGNUM pub_key, DH *dh)
139	0	{
140	0	int rv, pad;
141
142		/* rv is constant unless compute_key is external */
143		#ifdef FIPS_MODULE
144		rv = ossl_dh_compute_key(key, pub_key, dh);
145		#else
146	0	rv = dh->meth->compute_key(key, pub_key, dh);
147	0	#endif
148	0	if (rv <= 0)
149	0	return rv;
150	0	pad = BN_num_bytes(dh->params.p) - rv;
151		/* pad is constant (zero) unless compute_key is external */
152	0	if (pad > 0) {
153	0	memmove(key + pad, key, rv);
154	0	memset(key, 0, pad);
155	0	}
156	0	return rv + pad;
157	0	}
158
159		static DH_METHOD dh_ossl = {
160		"OpenSSL DH Method",
161		generate_key,
162		ossl_dh_compute_key,
163		dh_bn_mod_exp,
164		dh_init,
165		dh_finish,
166		DH_FLAG_FIPS_METHOD,
167		NULL,
168		NULL
169		};
170
171		static const DH_METHOD *default_DH_method = &dh_ossl;
172
173		const DH_METHOD *DH_OpenSSL(void)
174	0	{
175	0	return &dh_ossl;
176	0	}
177
178		const DH_METHOD *DH_get_default_method(void)
179	0	{
180	0	return default_DH_method;
181	0	}
182
183		static int dh_bn_mod_exp(const DH dh, BIGNUM r,
184		const BIGNUM a, const BIGNUM p,
185		const BIGNUM m, BN_CTX ctx, BN_MONT_CTX *m_ctx)
186	0	{
187	0	return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
188	0	}
189
190		static int dh_init(DH *dh)
191	0	{
192	0	dh->flags \|= DH_FLAG_CACHE_MONT_P;
193	0	ossl_ffc_params_init(&dh->params);
194	0	dh->dirty_cnt++;
195	0	return 1;
196	0	}
197
198		static int dh_finish(DH *dh)
199	0	{
200	0	BN_MONT_CTX_free(dh->method_mont_p);
201	0	return 1;
202	0	}
203
204		#ifndef FIPS_MODULE
205		void DH_set_default_method(const DH_METHOD *meth)
206	0	{
207	0	default_DH_method = meth;
208	0	}
209		#endif /* FIPS_MODULE */
210
211		int DH_generate_key(DH *dh)
212	0	{
213		#ifdef FIPS_MODULE
214		return generate_key(dh);
215		#else
216	0	return dh->meth->generate_key(dh);
217	0	#endif
218	0	}
219
220		int ossl_dh_generate_public_key(BN_CTX ctx, const DH dh,
221		const BIGNUM priv_key, BIGNUM pub_key)
222	0	{
223	0	int ret = 0;
224	0	BIGNUM *prk = BN_new();
225	0	BN_MONT_CTX *mont = NULL;
226
227	0	if (prk == NULL)
228	0	return 0;
229
230	0	if (dh->flags & DH_FLAG_CACHE_MONT_P) {
231		/*
232		* We take the input DH as const, but we lie, because in some cases we
233		* want to get a hold of its Montgomery context.
234		*
235		* We cast to remove the const qualifier in this case, it should be
236		* fine...
237		*/
238	0	BN_MONT_CTX pmont = (BN_MONT_CTX )&dh->method_mont_p;
239
240	0	mont = BN_MONT_CTX_set_locked(pmont, dh->lock, dh->params.p, ctx);
241	0	if (mont == NULL)
242	0	goto err;
243	0	}
244	0	BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
245
246		/* pub_key = g^priv_key mod p */
247	0	if (!dh->meth->bn_mod_exp(dh, pub_key, dh->params.g, prk, dh->params.p,
248	0	ctx, mont))
249	0	goto err;
250	0	ret = 1;
251	0	err:
252	0	BN_clear_free(prk);
253	0	return ret;
254	0	}
255
256		static int generate_key(DH *dh)
257	0	{
258	0	int ok = 0;
259	0	int generate_new_key = 0;
260	0	#ifndef FIPS_MODULE
261	0	unsigned l;
262	0	#endif
263	0	BN_CTX *ctx = NULL;
264	0	BIGNUM pub_key = NULL, priv_key = NULL;
265
266	0	if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS) {
267	0	ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
268	0	return 0;
269	0	}
270
271	0	if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS) {
272	0	ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
273	0	return 0;
274	0	}
275
276	0	ctx = BN_CTX_new_ex(dh->libctx);
277	0	if (ctx == NULL)
278	0	goto err;
279
280	0	if (dh->priv_key == NULL) {
281	0	priv_key = BN_secure_new();
282	0	if (priv_key == NULL)
283	0	goto err;
284	0	generate_new_key = 1;
285	0	} else {
286	0	priv_key = dh->priv_key;
287	0	}
288
289	0	if (dh->pub_key == NULL) {
290	0	pub_key = BN_new();
291	0	if (pub_key == NULL)
292	0	goto err;
293	0	} else {
294	0	pub_key = dh->pub_key;
295	0	}
296	0	if (generate_new_key) {
297		/* Is it an approved safe prime ?*/
298	0	if (DH_get_nid(dh) != NID_undef) {
299	0	int max_strength =
300	0	ossl_ifc_ffc_compute_security_bits(BN_num_bits(dh->params.p));
301
302	0	if (dh->params.q == NULL
303	0	\|\| dh->length > BN_num_bits(dh->params.q))
304	0	goto err;
305		/* dh->length = maximum bit length of generated private key */
306	0	if (!ossl_ffc_generate_private_key(ctx, &dh->params, dh->length,
307	0	max_strength, priv_key))
308	0	goto err;
309	0	} else {
310		#ifdef FIPS_MODULE
311		if (dh->params.q == NULL)
312		goto err;
313		#else
314	0	if (dh->params.q == NULL) {
315		/* secret exponent length, must satisfy 2^(l-1) <= p */
316	0	if (dh->length != 0
317	0	&& dh->length >= BN_num_bits(dh->params.p))
318	0	goto err;
319	0	l = dh->length ? dh->length : BN_num_bits(dh->params.p) - 1;
320	0	if (!BN_priv_rand_ex(priv_key, l, BN_RAND_TOP_ONE,
321	0	BN_RAND_BOTTOM_ANY, 0, ctx))
322	0	goto err;
323		/*
324		* We handle just one known case where g is a quadratic non-residue:
325		* for g = 2: p % 8 == 3
326		*/
327	0	if (BN_is_word(dh->params.g, DH_GENERATOR_2)
328	0	&& !BN_is_bit_set(dh->params.p, 2)) {
329		/* clear bit 0, since it won't be a secret anyway */
330	0	if (!BN_clear_bit(priv_key, 0))
331	0	goto err;
332	0	}
333	0	} else
334	0	#endif
335	0	{
336		/* Do a partial check for invalid p, q, g */
337	0	if (!ossl_ffc_params_simple_validate(dh->libctx, &dh->params,
338	0	FFC_PARAM_TYPE_DH, NULL))
339	0	goto err;
340		/*
341		* For FFC FIPS 186-4 keygen
342		* security strength s = 112,
343		* Max Private key size N = len(q)
344		*/
345	0	if (!ossl_ffc_generate_private_key(ctx, &dh->params,
346	0	BN_num_bits(dh->params.q),
347	0	MIN_STRENGTH,
348	0	priv_key))
349	0	goto err;
350	0	}
351	0	}
352	0	}
353
354	0	if (!ossl_dh_generate_public_key(ctx, dh, priv_key, pub_key))
355	0	goto err;
356
357	0	dh->pub_key = pub_key;
358	0	dh->priv_key = priv_key;
359	0	dh->dirty_cnt++;
360	0	ok = 1;
361	0	err:
362	0	if (ok != 1)
363	0	ERR_raise(ERR_LIB_DH, ERR_R_BN_LIB);
364
365	0	if (pub_key != dh->pub_key)
366	0	BN_free(pub_key);
367	0	if (priv_key != dh->priv_key)
368	0	BN_free(priv_key);
369	0	BN_CTX_free(ctx);
370	0	return ok;
371	0	}
372
373		int ossl_dh_buf2key(DH dh, const unsigned char buf, size_t len)
374	0	{
375	0	int err_reason = DH_R_BN_ERROR;
376	0	BIGNUM *pubkey = NULL;
377	0	const BIGNUM *p;
378	0	int ret;
379
380	0	if ((pubkey = BN_bin2bn(buf, len, NULL)) == NULL)
381	0	goto err;
382	0	DH_get0_pqg(dh, &p, NULL, NULL);
383	0	if (p == NULL \|\| BN_num_bytes(p) == 0) {
384	0	err_reason = DH_R_NO_PARAMETERS_SET;
385	0	goto err;
386	0	}
387		/* Prevent small subgroup attacks per RFC 8446 Section 4.2.8.1 */
388	0	if (!ossl_dh_check_pub_key_partial(dh, pubkey, &ret)) {
389	0	err_reason = DH_R_INVALID_PUBKEY;
390	0	goto err;
391	0	}
392	0	if (DH_set0_key(dh, pubkey, NULL) != 1)
393	0	goto err;
394	0	return 1;
395	0	err:
396	0	ERR_raise(ERR_LIB_DH, err_reason);
397	0	BN_free(pubkey);
398	0	return 0;
399	0	}
400
401		size_t ossl_dh_key2buf(const DH dh, unsigned char *pbuf_out, size_t size,
402		int alloc)
403	0	{
404	0	const BIGNUM *pubkey;
405	0	unsigned char *pbuf = NULL;
406	0	const BIGNUM *p;
407	0	int p_size;
408
409	0	DH_get0_pqg(dh, &p, NULL, NULL);
410	0	DH_get0_key(dh, &pubkey, NULL);
411	0	if (p == NULL \|\| pubkey == NULL
412	0	\|\| (p_size = BN_num_bytes(p)) == 0
413	0	\|\| BN_num_bytes(pubkey) == 0) {
414	0	ERR_raise(ERR_LIB_DH, DH_R_INVALID_PUBKEY);
415	0	return 0;
416	0	}
417	0	if (pbuf_out != NULL && (alloc \|\| *pbuf_out != NULL)) {
418	0	if (!alloc) {
419	0	if (size >= (size_t)p_size)
420	0	pbuf = *pbuf_out;
421	0	} else {
422	0	pbuf = OPENSSL_malloc(p_size);
423	0	}
424
425	0	if (pbuf == NULL) {
426	0	ERR_raise(ERR_LIB_DH, ERR_R_MALLOC_FAILURE);
427	0	return 0;
428	0	}
429		/*
430		* As per Section 4.2.8.1 of RFC 8446 left pad public
431		* key with zeros to the size of p
432		*/
433	0	if (BN_bn2binpad(pubkey, pbuf, p_size) < 0) {
434	0	if (alloc)
435	0	OPENSSL_free(pbuf);
436	0	ERR_raise(ERR_LIB_DH, DH_R_BN_ERROR);
437	0	return 0;
438	0	}
439	0	*pbuf_out = pbuf;
440	0	}
441	0	return p_size;
442	0	}