1 /*
2  * Copyright 2019-2021 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  * Finite Field cryptography (FFC) is used for DSA and DH.
12  * This file contains methods for validation of FFC parameters.
13  * It calls the same functions as the generation as the code is very similar.
14  */
15 
16 #include <openssl/err.h>
17 #include <openssl/bn.h>
18 #include <openssl/dsaerr.h>
19 #include <openssl/dherr.h>
20 #include "internal/ffc.h"
21 
22 /* FIPS186-4 A.2.2 Unverifiable partial validation of Generator g */
ossl_ffc_params_validate_unverifiable_g(BN_CTX * ctx,BN_MONT_CTX * mont,const BIGNUM * p,const BIGNUM * q,const BIGNUM * g,BIGNUM * tmp,int * ret)23 int ossl_ffc_params_validate_unverifiable_g(BN_CTX *ctx, BN_MONT_CTX *mont,
24                                             const BIGNUM *p, const BIGNUM *q,
25                                             const BIGNUM *g, BIGNUM *tmp,
26                                             int *ret)
27 {
28     /*
29      * A.2.2 Step (1) AND
30      * A.2.4 Step (2)
31      * Verify that 2 <= g <= (p - 1)
32      */
33     if (BN_cmp(g, BN_value_one()) <= 0 || BN_cmp(g, p) >= 0) {
34         *ret |= FFC_ERROR_NOT_SUITABLE_GENERATOR;
35         return 0;
36     }
37 
38     /*
39      * A.2.2 Step (2) AND
40      * A.2.4 Step (3)
41      * Check g^q mod p = 1
42      */
43     if (!BN_mod_exp_mont(tmp, g, q, p, ctx, mont))
44         return 0;
45     if (BN_cmp(tmp, BN_value_one()) != 0) {
46         *ret |= FFC_ERROR_NOT_SUITABLE_GENERATOR;
47         return 0;
48     }
49     return 1;
50 }
51 
ossl_ffc_params_FIPS186_4_validate(OSSL_LIB_CTX * libctx,const FFC_PARAMS * params,int type,int * res,BN_GENCB * cb)52 int ossl_ffc_params_FIPS186_4_validate(OSSL_LIB_CTX *libctx,
53                                        const FFC_PARAMS *params, int type,
54                                        int *res, BN_GENCB *cb)
55 {
56     size_t L, N;
57 
58     if (params == NULL || params->p == NULL || params->q == NULL)
59         return FFC_PARAM_RET_STATUS_FAILED;
60 
61     /* A.1.1.3 Step (1..2) : L = len(p), N = len(q) */
62     L = BN_num_bits(params->p);
63     N = BN_num_bits(params->q);
64     return ossl_ffc_params_FIPS186_4_gen_verify(libctx, (FFC_PARAMS *)params,
65                                                 FFC_PARAM_MODE_VERIFY, type,
66                                                 L, N, res, cb);
67 }
68 
69 /* This may be used in FIPS mode to validate deprecated FIPS-186-2 Params */
ossl_ffc_params_FIPS186_2_validate(OSSL_LIB_CTX * libctx,const FFC_PARAMS * params,int type,int * res,BN_GENCB * cb)70 int ossl_ffc_params_FIPS186_2_validate(OSSL_LIB_CTX *libctx,
71                                        const FFC_PARAMS *params, int type,
72                                        int *res, BN_GENCB *cb)
73 {
74     size_t L, N;
75 
76     if (params == NULL || params->p == NULL || params->q == NULL) {
77         *res = FFC_CHECK_INVALID_PQ;
78         return FFC_PARAM_RET_STATUS_FAILED;
79     }
80 
81     /* A.1.1.3 Step (1..2) : L = len(p), N = len(q) */
82     L = BN_num_bits(params->p);
83     N = BN_num_bits(params->q);
84     return ossl_ffc_params_FIPS186_2_gen_verify(libctx, (FFC_PARAMS *)params,
85                                                 FFC_PARAM_MODE_VERIFY, type,
86                                                 L, N, res, cb);
87 }
88 
89 /*
90  * This does a simple check of L and N and partial g.
91  * It makes no attempt to do a full validation of p, q or g since these require
92  * extra parameters such as the digest and seed, which may not be available for
93  * this test.
94  */
ossl_ffc_params_simple_validate(OSSL_LIB_CTX * libctx,const FFC_PARAMS * params,int paramstype,int * res)95 int ossl_ffc_params_simple_validate(OSSL_LIB_CTX *libctx, const FFC_PARAMS *params,
96                                     int paramstype, int *res)
97 {
98     int ret;
99     int tmpres = 0;
100     FFC_PARAMS tmpparams = {0};
101 
102     if (params == NULL)
103         return 0;
104 
105     if (res == NULL)
106         res = &tmpres;
107 
108     if (!ossl_ffc_params_copy(&tmpparams, params))
109         return 0;
110 
111     tmpparams.flags = FFC_PARAM_FLAG_VALIDATE_G;
112     tmpparams.gindex = FFC_UNVERIFIABLE_GINDEX;
113 
114 #ifndef FIPS_MODULE
115     if (params->flags & FFC_PARAM_FLAG_VALIDATE_LEGACY)
116         ret = ossl_ffc_params_FIPS186_2_validate(libctx, &tmpparams, paramstype,
117                                                  res, NULL);
118     else
119 #endif
120         ret = ossl_ffc_params_FIPS186_4_validate(libctx, &tmpparams, paramstype,
121                                                  res, NULL);
122 #ifndef OPENSSL_NO_DH
123     if (ret == FFC_PARAM_RET_STATUS_FAILED
124         && (*res & FFC_ERROR_NOT_SUITABLE_GENERATOR) != 0) {
125         ERR_raise(ERR_LIB_DH, DH_R_NOT_SUITABLE_GENERATOR);
126     }
127 #endif
128 
129     ossl_ffc_params_cleanup(&tmpparams);
130 
131     return ret != FFC_PARAM_RET_STATUS_FAILED;
132 }
133 
134 /*
135  * If possible (or always in FIPS_MODULE) do full FIPS 186-4 validation.
136  * Otherwise do simple check but in addition also check the primality of the
137  * p and q.
138  */
ossl_ffc_params_full_validate(OSSL_LIB_CTX * libctx,const FFC_PARAMS * params,int paramstype,int * res)139 int ossl_ffc_params_full_validate(OSSL_LIB_CTX *libctx, const FFC_PARAMS *params,
140                                   int paramstype, int *res)
141 {
142     int tmpres = 0;
143 
144     if (params == NULL)
145         return 0;
146 
147     if (res == NULL)
148         res = &tmpres;
149 
150 #ifdef FIPS_MODULE
151     return ossl_ffc_params_FIPS186_4_validate(libctx, params, paramstype,
152                                               res, NULL);
153 #else
154     if (params->seed != NULL) {
155         if (params->flags & FFC_PARAM_FLAG_VALIDATE_LEGACY)
156             return ossl_ffc_params_FIPS186_2_validate(libctx, params, paramstype,
157                                                       res, NULL);
158         else
159             return ossl_ffc_params_FIPS186_4_validate(libctx, params, paramstype,
160                                                       res, NULL);
161     } else {
162         int ret = 0;
163 
164         ret = ossl_ffc_params_simple_validate(libctx, params, paramstype, res);
165         if (ret) {
166             BN_CTX *ctx;
167 
168             if ((ctx = BN_CTX_new_ex(libctx)) == NULL)
169                 return 0;
170             if (BN_check_prime(params->q, ctx, NULL) != 1) {
171 # ifndef OPENSSL_NO_DSA
172                 ERR_raise(ERR_LIB_DSA, DSA_R_Q_NOT_PRIME);
173 # endif
174                 ret = 0;
175             }
176             if (ret && BN_check_prime(params->p, ctx, NULL) != 1) {
177 # ifndef OPENSSL_NO_DSA
178                 ERR_raise(ERR_LIB_DSA, DSA_R_P_NOT_PRIME);
179 # endif
180                 ret = 0;
181             }
182             BN_CTX_free(ctx);
183         }
184         return ret;
185     }
186 #endif
187 }
188