xref: /openssl/crypto/dsa/dsa_key.c (revision da1c088f)
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  * DSA 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 <time.h>
18 #include "internal/cryptlib.h"
19 #include <openssl/bn.h>
20 #include <openssl/self_test.h>
21 #include "prov/providercommon.h"
22 #include "crypto/dsa.h"
23 #include "dsa_local.h"
24 
25 #ifdef FIPS_MODULE
26 # define MIN_STRENGTH 112
27 #else
28 # define MIN_STRENGTH 80
29 #endif
30 
31 static int dsa_keygen(DSA *dsa);
32 
DSA_generate_key(DSA * dsa)33 int DSA_generate_key(DSA *dsa)
34 {
35 #ifndef FIPS_MODULE
36     if (dsa->meth->dsa_keygen != NULL)
37         return dsa->meth->dsa_keygen(dsa);
38 #endif
39     return dsa_keygen(dsa);
40 }
41 
ossl_dsa_generate_public_key(BN_CTX * ctx,const DSA * dsa,const BIGNUM * priv_key,BIGNUM * pub_key)42 int ossl_dsa_generate_public_key(BN_CTX *ctx, const DSA *dsa,
43                                  const BIGNUM *priv_key, BIGNUM *pub_key)
44 {
45     int ret = 0;
46     BIGNUM *prk = BN_new();
47 
48     if (prk == NULL)
49         return 0;
50     BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
51 
52     /* pub_key = g ^ priv_key mod p */
53     if (!BN_mod_exp(pub_key, dsa->params.g, prk, dsa->params.p, ctx))
54         goto err;
55     ret = 1;
56 err:
57     BN_clear_free(prk);
58     return ret;
59 }
60 
61 #ifdef FIPS_MODULE
62 /*
63  * Refer: FIPS 140-3 IG 10.3.A Additional Comment 1
64  * Perform a KAT by duplicating the public key generation.
65  *
66  * NOTE: This issue requires a background understanding, provided in a separate
67  * document; the current IG 10.3.A AC1 is insufficient regarding the PCT for
68  * the key agreement scenario.
69  *
70  * Currently IG 10.3.A requires PCT in the mode of use prior to use of the
71  * key pair, citing the PCT defined in the associated standard. For key
72  * agreement, the only PCT defined in SP 800-56A is that of Section 5.6.2.4:
73  * the comparison of the original public key to a newly calculated public key.
74  */
dsa_keygen_knownanswer_test(DSA * dsa,BN_CTX * ctx,OSSL_CALLBACK * cb,void * cbarg)75 static int dsa_keygen_knownanswer_test(DSA *dsa, BN_CTX *ctx,
76                                        OSSL_CALLBACK *cb, void *cbarg)
77 {
78     int len, ret = 0;
79     OSSL_SELF_TEST *st = NULL;
80     unsigned char bytes[512] = {0};
81     BIGNUM *pub_key2 = BN_new();
82 
83     if (pub_key2 == NULL)
84         return 0;
85 
86     st = OSSL_SELF_TEST_new(cb, cbarg);
87     if (st == NULL)
88         goto err;
89 
90     OSSL_SELF_TEST_onbegin(st, OSSL_SELF_TEST_TYPE_PCT_KAT,
91                                OSSL_SELF_TEST_DESC_PCT_DSA);
92 
93     if (!ossl_dsa_generate_public_key(ctx, dsa, dsa->priv_key, pub_key2))
94         goto err;
95 
96     if (BN_num_bytes(pub_key2) > (int)sizeof(bytes))
97         goto err;
98     len = BN_bn2bin(pub_key2, bytes);
99     OSSL_SELF_TEST_oncorrupt_byte(st, bytes);
100     if (BN_bin2bn(bytes, len, pub_key2) != NULL)
101         ret = !BN_cmp(dsa->pub_key, pub_key2);
102 
103 err:
104     OSSL_SELF_TEST_onend(st, ret);
105     OSSL_SELF_TEST_free(st);
106     BN_free(pub_key2);
107     return ret;
108 }
109 
110 /*
111  * FIPS 140-2 IG 9.9 AS09.33
112  * Perform a sign/verify operation.
113  */
dsa_keygen_pairwise_test(DSA * dsa,OSSL_CALLBACK * cb,void * cbarg)114 static int dsa_keygen_pairwise_test(DSA *dsa, OSSL_CALLBACK *cb, void *cbarg)
115 {
116     int ret = 0;
117     unsigned char dgst[16] = {0};
118     unsigned int dgst_len = (unsigned int)sizeof(dgst);
119     DSA_SIG *sig = NULL;
120     OSSL_SELF_TEST *st = NULL;
121 
122     st = OSSL_SELF_TEST_new(cb, cbarg);
123     if (st == NULL)
124         goto err;
125 
126     OSSL_SELF_TEST_onbegin(st, OSSL_SELF_TEST_TYPE_PCT,
127                            OSSL_SELF_TEST_DESC_PCT_DSA);
128 
129     sig = DSA_do_sign(dgst, (int)dgst_len, dsa);
130     if (sig == NULL)
131         goto err;
132 
133     OSSL_SELF_TEST_oncorrupt_byte(st, dgst);
134 
135     if (DSA_do_verify(dgst, dgst_len, sig, dsa) != 1)
136         goto err;
137 
138     ret = 1;
139 err:
140     OSSL_SELF_TEST_onend(st, ret);
141     OSSL_SELF_TEST_free(st);
142     DSA_SIG_free(sig);
143     return ret;
144 }
145 #endif /* FIPS_MODULE */
146 
dsa_keygen(DSA * dsa)147 static int dsa_keygen(DSA *dsa)
148 {
149     int ok = 0;
150     BN_CTX *ctx = NULL;
151     BIGNUM *pub_key = NULL, *priv_key = NULL;
152 
153     if ((ctx = BN_CTX_new_ex(dsa->libctx)) == NULL)
154         goto err;
155 
156     if (dsa->priv_key == NULL) {
157         if ((priv_key = BN_secure_new()) == NULL)
158             goto err;
159     } else {
160         priv_key = dsa->priv_key;
161     }
162 
163     /* Do a partial check for invalid p, q, g */
164     if (!ossl_ffc_params_simple_validate(dsa->libctx, &dsa->params,
165                                          FFC_PARAM_TYPE_DSA, NULL))
166         goto err;
167 
168     /*
169      * For FFC FIPS 186-4 keygen
170      * security strength s = 112,
171      * Max Private key size N = len(q)
172      */
173     if (!ossl_ffc_generate_private_key(ctx, &dsa->params,
174                                        BN_num_bits(dsa->params.q),
175                                        MIN_STRENGTH, priv_key))
176         goto err;
177 
178     if (dsa->pub_key == NULL) {
179         if ((pub_key = BN_new()) == NULL)
180             goto err;
181     } else {
182         pub_key = dsa->pub_key;
183     }
184 
185     if (!ossl_dsa_generate_public_key(ctx, dsa, priv_key, pub_key))
186         goto err;
187 
188     dsa->priv_key = priv_key;
189     dsa->pub_key = pub_key;
190 
191     ok = 1;
192 #ifdef FIPS_MODULE
193     {
194         OSSL_CALLBACK *cb = NULL;
195         void *cbarg = NULL;
196 
197         OSSL_SELF_TEST_get_callback(dsa->libctx, &cb, &cbarg);
198         ok = dsa_keygen_pairwise_test(dsa, cb, cbarg)
199              && dsa_keygen_knownanswer_test(dsa, ctx, cb, cbarg);
200         if (!ok) {
201             ossl_set_error_state(OSSL_SELF_TEST_TYPE_PCT);
202             BN_free(dsa->pub_key);
203             BN_clear_free(dsa->priv_key);
204             dsa->pub_key = NULL;
205             dsa->priv_key = NULL;
206             BN_CTX_free(ctx);
207             return ok;
208         }
209     }
210 #endif
211     dsa->dirty_cnt++;
212 
213  err:
214     if (pub_key != dsa->pub_key)
215         BN_free(pub_key);
216     if (priv_key != dsa->priv_key)
217         BN_free(priv_key);
218     BN_CTX_free(ctx);
219 
220     return ok;
221 }
222