1/*
2 * Copyright 1995-2023 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 <openssl/bn.h>
19#include "dh_local.h"
20#include "crypto/dh.h"
21
22/*-
23 * Check that p and g are suitable enough
24 *
25 * p is odd
26 * 1 < g < p - 1
27 */
28int DH_check_params_ex(const DH *dh)
29{
30    int errflags = 0;
31
32    if (!DH_check_params(dh, &errflags))
33        return 0;
34
35    if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
36        ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_PRIME);
37    if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
38        ERR_raise(ERR_LIB_DH, DH_R_NOT_SUITABLE_GENERATOR);
39    if ((errflags & DH_MODULUS_TOO_SMALL) != 0)
40        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
41    if ((errflags & DH_MODULUS_TOO_LARGE) != 0)
42        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
43
44    return errflags == 0;
45}
46
47#ifdef FIPS_MODULE
48int DH_check_params(const DH *dh, int *ret)
49{
50    int nid;
51
52    *ret = 0;
53    /*
54     * SP800-56A R3 Section 5.5.2 Assurances of Domain Parameter Validity
55     * (1a) The domain parameters correspond to any approved safe prime group.
56     */
57    nid = DH_get_nid((DH *)dh);
58    if (nid != NID_undef)
59        return 1;
60    /*
61     * OR
62     * (2b) FFC domain params conform to FIPS-186-4 explicit domain param
63     * validity tests.
64     */
65    return ossl_ffc_params_FIPS186_4_validate(dh->libctx, &dh->params,
66                                              FFC_PARAM_TYPE_DH, ret, NULL);
67}
68#else
69int DH_check_params(const DH *dh, int *ret)
70{
71    int ok = 0;
72    BIGNUM *tmp = NULL;
73    BN_CTX *ctx = NULL;
74
75    *ret = 0;
76    ctx = BN_CTX_new_ex(dh->libctx);
77    if (ctx == NULL)
78        goto err;
79    BN_CTX_start(ctx);
80    tmp = BN_CTX_get(ctx);
81    if (tmp == NULL)
82        goto err;
83
84    if (!BN_is_odd(dh->params.p))
85        *ret |= DH_CHECK_P_NOT_PRIME;
86    if (BN_is_negative(dh->params.g)
87        || BN_is_zero(dh->params.g)
88        || BN_is_one(dh->params.g))
89        *ret |= DH_NOT_SUITABLE_GENERATOR;
90    if (BN_copy(tmp, dh->params.p) == NULL || !BN_sub_word(tmp, 1))
91        goto err;
92    if (BN_cmp(dh->params.g, tmp) >= 0)
93        *ret |= DH_NOT_SUITABLE_GENERATOR;
94    if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS)
95        *ret |= DH_MODULUS_TOO_SMALL;
96    if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS)
97        *ret |= DH_MODULUS_TOO_LARGE;
98
99    ok = 1;
100 err:
101    BN_CTX_end(ctx);
102    BN_CTX_free(ctx);
103    return ok;
104}
105#endif /* FIPS_MODULE */
106
107/*-
108 * Check that p is a safe prime and
109 * g is a suitable generator.
110 */
111int DH_check_ex(const DH *dh)
112{
113    int errflags = 0;
114
115    if (!DH_check(dh, &errflags))
116        return 0;
117
118    if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
119        ERR_raise(ERR_LIB_DH, DH_R_NOT_SUITABLE_GENERATOR);
120    if ((errflags & DH_CHECK_Q_NOT_PRIME) != 0)
121        ERR_raise(ERR_LIB_DH, DH_R_CHECK_Q_NOT_PRIME);
122    if ((errflags & DH_CHECK_INVALID_Q_VALUE) != 0)
123        ERR_raise(ERR_LIB_DH, DH_R_CHECK_INVALID_Q_VALUE);
124    if ((errflags & DH_CHECK_INVALID_J_VALUE) != 0)
125        ERR_raise(ERR_LIB_DH, DH_R_CHECK_INVALID_J_VALUE);
126    if ((errflags & DH_UNABLE_TO_CHECK_GENERATOR) != 0)
127        ERR_raise(ERR_LIB_DH, DH_R_UNABLE_TO_CHECK_GENERATOR);
128    if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
129        ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_PRIME);
130    if ((errflags & DH_CHECK_P_NOT_SAFE_PRIME) != 0)
131        ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_SAFE_PRIME);
132    if ((errflags & DH_MODULUS_TOO_SMALL) != 0)
133        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
134    if ((errflags & DH_MODULUS_TOO_LARGE) != 0)
135        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
136
137    return errflags == 0;
138}
139
140/* Note: according to documentation - this only checks the params */
141int DH_check(const DH *dh, int *ret)
142{
143#ifdef FIPS_MODULE
144    return DH_check_params(dh, ret);
145#else
146    int ok = 0, r, q_good = 0;
147    BN_CTX *ctx = NULL;
148    BIGNUM *t1 = NULL, *t2 = NULL;
149    int nid = DH_get_nid((DH *)dh);
150
151    *ret = 0;
152    if (nid != NID_undef)
153        return 1;
154
155    /* Don't do any checks at all with an excessively large modulus */
156    if (BN_num_bits(dh->params.p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {
157        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
158        *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_P_NOT_PRIME;
159        return 0;
160    }
161
162    if (!DH_check_params(dh, ret))
163        return 0;
164
165    ctx = BN_CTX_new_ex(dh->libctx);
166    if (ctx == NULL)
167        goto err;
168    BN_CTX_start(ctx);
169    t1 = BN_CTX_get(ctx);
170    t2 = BN_CTX_get(ctx);
171    if (t2 == NULL)
172        goto err;
173
174    if (dh->params.q != NULL) {
175        if (BN_ucmp(dh->params.p, dh->params.q) > 0)
176            q_good = 1;
177        else
178            *ret |= DH_CHECK_INVALID_Q_VALUE;
179    }
180
181    if (q_good) {
182        if (BN_cmp(dh->params.g, BN_value_one()) <= 0)
183            *ret |= DH_NOT_SUITABLE_GENERATOR;
184        else if (BN_cmp(dh->params.g, dh->params.p) >= 0)
185            *ret |= DH_NOT_SUITABLE_GENERATOR;
186        else {
187            /* Check g^q == 1 mod p */
188            if (!BN_mod_exp(t1, dh->params.g, dh->params.q, dh->params.p, ctx))
189                goto err;
190            if (!BN_is_one(t1))
191                *ret |= DH_NOT_SUITABLE_GENERATOR;
192        }
193        r = BN_check_prime(dh->params.q, ctx, NULL);
194        if (r < 0)
195            goto err;
196        if (!r)
197            *ret |= DH_CHECK_Q_NOT_PRIME;
198        /* Check p == 1 mod q  i.e. q divides p - 1 */
199        if (!BN_div(t1, t2, dh->params.p, dh->params.q, ctx))
200            goto err;
201        if (!BN_is_one(t2))
202            *ret |= DH_CHECK_INVALID_Q_VALUE;
203        if (dh->params.j != NULL
204            && BN_cmp(dh->params.j, t1))
205            *ret |= DH_CHECK_INVALID_J_VALUE;
206    }
207
208    r = BN_check_prime(dh->params.p, ctx, NULL);
209    if (r < 0)
210        goto err;
211    if (!r)
212        *ret |= DH_CHECK_P_NOT_PRIME;
213    else if (dh->params.q == NULL) {
214        if (!BN_rshift1(t1, dh->params.p))
215            goto err;
216        r = BN_check_prime(t1, ctx, NULL);
217        if (r < 0)
218            goto err;
219        if (!r)
220            *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
221    }
222    ok = 1;
223 err:
224    BN_CTX_end(ctx);
225    BN_CTX_free(ctx);
226    return ok;
227#endif /* FIPS_MODULE */
228}
229
230int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key)
231{
232    int errflags = 0;
233
234    if (!DH_check_pub_key(dh, pub_key, &errflags))
235        return 0;
236
237    if ((errflags & DH_CHECK_PUBKEY_TOO_SMALL) != 0)
238        ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_TOO_SMALL);
239    if ((errflags & DH_CHECK_PUBKEY_TOO_LARGE) != 0)
240        ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_TOO_LARGE);
241    if ((errflags & DH_CHECK_PUBKEY_INVALID) != 0)
242        ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_INVALID);
243
244    return errflags == 0;
245}
246
247/*
248 * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Full public key validation.
249 */
250int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
251{
252    /* Don't do any checks at all with an excessively large modulus */
253    if (BN_num_bits(dh->params.p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {
254        ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
255        *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_PUBKEY_INVALID;
256        return 0;
257    }
258
259    if (dh->params.q != NULL && BN_ucmp(dh->params.p, dh->params.q) < 0) {
260        *ret |= DH_CHECK_INVALID_Q_VALUE | DH_CHECK_PUBKEY_INVALID;
261        return 1;
262    }
263
264    return ossl_ffc_validate_public_key(&dh->params, pub_key, ret);
265}
266
267/*
268 * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Partial public key validation.
269 * To only be used with ephemeral FFC public keys generated using the approved
270 * safe-prime groups.
271 */
272int ossl_dh_check_pub_key_partial(const DH *dh, const BIGNUM *pub_key, int *ret)
273{
274    return ossl_ffc_validate_public_key_partial(&dh->params, pub_key, ret)
275           && *ret == 0;
276}
277
278int ossl_dh_check_priv_key(const DH *dh, const BIGNUM *priv_key, int *ret)
279{
280    int ok = 0;
281    BIGNUM *two_powN = NULL, *upper;
282
283    *ret = 0;
284    two_powN = BN_new();
285    if (two_powN == NULL)
286        return 0;
287
288    if (dh->params.q != NULL) {
289        upper = dh->params.q;
290#ifndef FIPS_MODULE
291    } else if (dh->params.p != NULL) {
292        /*
293         * We do not have q so we just check the key is within some
294         * reasonable range, or the number of bits is equal to dh->length.
295         */
296        int length = dh->length;
297
298        if (length == 0) {
299            length = BN_num_bits(dh->params.p) - 1;
300            if (BN_num_bits(priv_key) <= length
301                && BN_num_bits(priv_key) > 1)
302                ok = 1;
303        } else if (BN_num_bits(priv_key) == length) {
304            ok = 1;
305        }
306        goto end;
307#endif
308    } else {
309        goto end;
310    }
311
312    /* Is it from an approved Safe prime group ?*/
313    if (DH_get_nid((DH *)dh) != NID_undef && dh->length != 0) {
314        if (!BN_lshift(two_powN, BN_value_one(), dh->length))
315            goto end;
316        if (BN_cmp(two_powN, dh->params.q) < 0)
317            upper = two_powN;
318    }
319    if (!ossl_ffc_validate_private_key(upper, priv_key, ret))
320        goto end;
321
322    ok = 1;
323end:
324    BN_free(two_powN);
325    return ok;
326}
327
328/*
329 * FFC pairwise check from SP800-56A R3.
330 *    Section 5.6.2.1.4 Owner Assurance of Pair-wise Consistency
331 */
332int ossl_dh_check_pairwise(const DH *dh)
333{
334    int ret = 0;
335    BN_CTX *ctx = NULL;
336    BIGNUM *pub_key = NULL;
337
338    if (dh->params.p == NULL
339        || dh->params.g == NULL
340        || dh->priv_key == NULL
341        || dh->pub_key == NULL)
342        return 0;
343
344    ctx = BN_CTX_new_ex(dh->libctx);
345    if (ctx == NULL)
346        goto err;
347    pub_key = BN_new();
348    if (pub_key == NULL)
349        goto err;
350
351    /* recalculate the public key = (g ^ priv) mod p */
352    if (!ossl_dh_generate_public_key(ctx, dh, dh->priv_key, pub_key))
353        goto err;
354    /* check it matches the existing pubic_key */
355    ret = BN_cmp(pub_key, dh->pub_key) == 0;
356err:
357    BN_free(pub_key);
358    BN_CTX_free(ctx);
359    return ret;
360}
361