xref: /openssl/crypto/dh/dh_check.c (revision b6461792)
1 /*
2  * Copyright 1995-2024 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  */
DH_check_params_ex(const DH * dh)28 int 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
DH_check_params(const DH * dh,int * ret)48 int 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
DH_check_params(const DH * dh,int * ret)69 int 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  */
DH_check_ex(const DH * dh)111 int 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 */
DH_check(const DH * dh,int * ret)141 int 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 
DH_check_pub_key_ex(const DH * dh,const BIGNUM * pub_key)230 int 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  */
DH_check_pub_key(const DH * dh,const BIGNUM * pub_key,int * ret)250 int 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  */
ossl_dh_check_pub_key_partial(const DH * dh,const BIGNUM * pub_key,int * ret)272 int 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 
ossl_dh_check_priv_key(const DH * dh,const BIGNUM * priv_key,int * ret)278 int 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;
323 end:
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  */
ossl_dh_check_pairwise(const DH * dh)332 int 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 public_key */
355     ret = BN_cmp(pub_key, dh->pub_key) == 0;
356 err:
357     BN_free(pub_key);
358     BN_CTX_free(ctx);
359     return ret;
360 }
361