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Add convenience functions and macros for asymmetric key generation
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1=pod
2
3=head1 NAME
4
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5EVP_PKEY-DH, EVP_PKEY-DHX, EVP_KEYMGMT-DH
6- EVP_PKEY DH and DHX keytype and algorithm support
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7
8=head1 DESCRIPTION
9
10For B<DH> FFC key agreement, two classes of domain parameters can be used:
11"safe" domain parameters that are associated with approved named safe-prime
12groups, and a class of "FIPS 186-type" domain parameters. FIPS 186-type domain
13parameters should only be used for backward compatibility with existing
14applications that cannot be upgraded to use the approved safe-prime groups.
15
16See L<EVP_PKEY-FFC(7)> for more information about FFC keys.
17
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18The B<DH> key type uses PKCS#3 format which saves p and g, but not the 'q' value.
19The B<DHX> key type uses X9.42 format which saves the value of 'q' and this
20must be used for FIPS186-4.
21
22For B<DHX> that is not a named group the FIPS186-4 standard specifies that the
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23values used for FFC parameter generation are also required for parameter
24validation. This means that optional FFC domain parameter values for
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25I<seed>, I<pcounter> and I<gindex> or I<hindex> may need to be stored for
26validation purposes.
27For B<DHX> the I<seed> and I<pcounter> can be stored in ASN1 data
28(but the I<gindex> or I<hindex> can not be stored).
b8086652 29
f1ffaaee 30=head2 DH and DHX domain parameters
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31
32In addition to the common FCC parameters that all FFC keytypes should support
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33(see L<EVP_PKEY-FFC(7)/FFC parameters>) the B<DHX> and B<DH> keytype
34implementations support the following:
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35
36=over 4
37
023b188c 38=item "group" (B<OSSL_PKEY_PARAM_GROUP_NAME>) <UTF8 string>
b8086652 39
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40Sets or gets a string that associates a B<DH> or B<DHX> named safe prime group
41with known values for I<p>, I<q> and I<g>.
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42
43The following values can be used by the OpenSSL's default and FIPS providers:
44"ffdhe2048", "ffdhe3072", "ffdhe4096", "ffdhe6144", "ffdhe8192",
45"modp_2048", "modp_3072", "modp_4096", "modp_6144", "modp_8192".
46
47The following additional values can also be used by OpenSSL's default provider:
48"modp_1536", "dh_1024_160", "dh_2048_224", "dh_2048_256".
49
f1ffaaee 50DH/DHX named groups can be easily validated since the parameters are well known.
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51For protocols that only transfer I<p> and I<g> the value of I<q> can also be
52retrieved.
53
f1ffaaee 54=back
b8086652 55
f1ffaaee 56=head2 DH and DHX additional parameters
b8086652 57
f1ffaaee 58=over 4
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5ac8fb58 60=item "encoded-pub-key" (B<OSSL_PKEY_PARAM_ENCODED_PUBLIC_KEY>) <octet string>
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61
62Used for getting and setting the encoding of the DH public key used in a key
63exchange message for the TLS protocol.
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64See EVP_PKEY_set1_encoded_public_key() and EVP_PKEY_get1_encoded_public_key().
65
66=back
67
68=head2 DH additional domain parameters
69
70=over 4
71
72=item "safeprime-generator" (B<OSSL_PKEY_PARAM_DH_GENERATOR>) <integer>
73
74Used for DH generation of safe primes using the old safe prime generator code.
75The default value is 2.
76It is recommended to use a named safe prime group instead, if domain parameter
77validation is required.
78
79Randomly generated safe primes are not allowed by FIPS, so setting this value
80for the OpenSSL FIPS provider will instead choose a named safe prime group
81based on the size of I<p>.
6a9bd929 82
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83=back
84
f1ffaaee 85=head2 DH and DHX domain parameter / key generation parameters
b8086652 86
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87In addition to the common FFC key generation parameters that all FFC key types
88should support (see L<EVP_PKEY-FFC(7)/FFC key generation parameters>) the
f1ffaaee 89B<DH> and B<DHX> keytype implementation supports the following:
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90
91=over 4
92
c9f18e59 93=item "type" (B<OSSL_PKEY_PARAM_FFC_TYPE>) <UTF8 string>
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94
95Sets the type of parameter generation. For B<DH> valid values are:
96
97=over 4
98
99=item "fips186_4"
100
101=item "default"
102
103=item "fips186_2"
104
105These are described in L<EVP_PKEY-FFC(7)/FFC key generation parameters>
106
107=item "group"
108
109This specifies that a named safe prime name will be chosen using the "pbits"
110type.
111
112=item "generator"
113
114A safe prime generator. See the "safeprime-generator" type above.
f1ffaaee 115This is only valid for B<DH> keys.
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116
117=back
118
119=item "pbits" (B<OSSL_PKEY_PARAM_FFC_PBITS>) <unsigned integer>
120
121Sets the size (in bits) of the prime 'p'.
122
123For "fips186_4" this must be 2048.
124For "fips186_2" this must be 1024.
125For "group" this can be any one of 2048, 3072, 4096, 6144 or 8192.
126
127=item "priv_len" (B<OSSL_PKEY_PARAM_DH_PRIV_LEN>) <integer>
128
129An optional value to set the maximum length of the generated private key.
8c1cbc72 130The default value used if this is not set is the maximum value of
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131BN_num_bits(I<q>)). The minimum value that this can be set to is 2 * s.
132Where s is the security strength of the key which has values of
133112, 128, 152, 176 and 200 for key sizes of 2048, 3072, 4096, 6144 and 8192.
134
135=back
136
137=head1 EXAMPLES
138
139An B<EVP_PKEY> context can be obtained by calling:
140
141 EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_from_name(NULL, "DH", NULL);
142
185e1aa2 143A B<DH> key can be generated with a named safe prime group by calling:
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144
145 int priv_len = 2 * 112;
146 OSSL_PARAM params[3];
147 EVP_PKEY *pkey = NULL;
148 EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_from_name(NULL, "DH", NULL);
149
150 params[0] = OSSL_PARAM_construct_utf8_string("group", "ffdhe2048", 0);
151 /* "priv_len" is optional */
152 params[1] = OSSL_PARAM_construct_int("priv_len", &priv_len);
153 params[2] = OSSL_PARAM_construct_end();
154
155 EVP_PKEY_keygen_init(pctx);
156 EVP_PKEY_CTX_set_params(pctx, params);
f9253152 157 EVP_PKEY_generate(pctx, &pkey);
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158 ...
159 EVP_PKEY_free(key);
160 EVP_PKEY_CTX_free(pctx);
161
185e1aa2 162B<DHX> domain parameters can be generated according to B<FIPS 186-4> by calling:
05fa5fde 163
990aa405 164 int gindex = 2;
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165 unsigned int pbits = 2048;
166 unsigned int qbits = 256;
990aa405 167 OSSL_PARAM params[6];
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168 EVP_PKEY *param_key = NULL;
169 EVP_PKEY_CTX *pctx = NULL;
170
185e1aa2 171 pctx = EVP_PKEY_CTX_new_from_name(NULL, "DHX", NULL);
b8086652 172 EVP_PKEY_paramgen_init(pctx);
2edb571b 173
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174 params[0] = OSSL_PARAM_construct_uint("pbits", &pbits);
175 params[1] = OSSL_PARAM_construct_uint("qbits", &qbits);
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176 params[2] = OSSL_PARAM_construct_int("gindex", &gindex);
177 params[3] = OSSL_PARAM_construct_utf8_string("type", "fips186_4", 0);
178 params[4] = OSSL_PARAM_construct_utf8_string("digest", "SHA256", 0);
179 params[5] = OSSL_PARAM_construct_end();
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180 EVP_PKEY_CTX_set_params(pctx, params);
181
f9253152 182 EVP_PKEY_generate(pctx, &param_key);
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183
184 EVP_PKEY_print_params(bio_out, param_key, 0, NULL);
185 ...
186 EVP_PKEY_free(param_key);
187 EVP_PKEY_CTX_free(pctx);
188
185e1aa2 189A B<DH> key can be generated using domain parameters by calling:
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190
191 EVP_PKEY *key = NULL;
192 EVP_PKEY_CTX *gctx = EVP_PKEY_CTX_new_from_pkey(NULL, param_key, NULL);
193
194 EVP_PKEY_keygen_init(gctx);
f9253152 195 EVP_PKEY_generate(gctx, &key);
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196 EVP_PKEY_print_private(bio_out, key, 0, NULL);
197 ...
198 EVP_PKEY_free(key);
199 EVP_PKEY_CTX_free(gctx);
200
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201To validate B<FIPS 186-4> B<DHX> domain parameters decoded from B<PEM> or
202B<DER> data, additional values used during generation may be required to
203be set into the key.
204
205EVP_PKEY_todata(), OSSL_PARAM_merge(), and EVP_PKEY_fromdata() are useful
206to add these parameters to the original key or domain parameters before
990aa405 207the actual validation. In production code the return values should be checked.
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208
209 EVP_PKEY *received_domp = ...; /* parameters received and decoded */
210 unsigned char *seed = ...; /* and additional parameters received */
211 size_t seedlen = ...; /* by other means, required */
212 int gindex = ...; /* for the validation */
213 int pcounter = ...;
214 int hindex = ...;
990aa405 215 OSSL_PARAM extra_params[4];
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216 OSSL_PARAM *domain_params = NULL;
217 OSSL_PARAM *merged_params = NULL;
218 EVP_PKEY_CTX *ctx = NULL, *validate_ctx = NULL;
219 EVP_PKEY *complete_domp = NULL;
220
221 EVP_PKEY_todata(received_domp, OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS,
222 &domain_params);
223 extra_params[0] = OSSL_PARAM_construct_octet_string("seed", seed, seedlen);
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224 /*
225 * NOTE: For unverifiable g use "hindex" instead of "gindex"
226 * extra_params[1] = OSSL_PARAM_construct_int("hindex", &hindex);
227 */
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228 extra_params[1] = OSSL_PARAM_construct_int("gindex", &gindex);
229 extra_params[2] = OSSL_PARAM_construct_int("pcounter", &pcounter);
990aa405 230 extra_params[3] = OSSL_PARAM_construct_end();
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231 merged_params = OSSL_PARAM_merge(domain_params, extra_params);
232
233 ctx = EVP_PKEY_CTX_new_from_name(NULL, "DHX", NULL);
234 EVP_PKEY_fromdata_init(ctx);
235 EVP_PKEY_fromdata(ctx, &complete_domp, OSSL_KEYMGMT_SELECT_ALL,
236 merged_params);
237
238 validate_ctx = EVP_PKEY_CTX_new_from_pkey(NULL, complete_domp, NULL);
239 if (EVP_PKEY_param_check(validate_ctx) > 0)
240 /* validation_passed(); */
241 else
242 /* validation_failed(); */
243
244 OSSL_PARAM_free(domain_params);
245 OSSL_PARAM_free(merged_params);
246 EVP_PKEY_CTX_free(ctx);
247 EVP_PKEY_CTX_free(validate_ctx);
248 EVP_PKEY_free(complete_domp);
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249
250=head1 CONFORMING TO
251
252=over 4
253
254=item RFC 7919 (TLS ffdhe named safe prime groups)
255
256=item RFC 3526 (IKE modp named safe prime groups)
257
258=item RFC 5114 (Additional DH named groups for dh_1024_160", "dh_2048_224"
259 and "dh_2048_256").
260
261=back
262
263The following sections of SP800-56Ar3:
264
265=over 4
266
267=item 5.5.1.1 FFC Domain Parameter Selection/Generation
268
269=item Appendix D: FFC Safe-prime Groups
270
271=back
272
273The following sections of FIPS 186-4:
274
275=over 4
276
277=item A.1.1.2 Generation of Probable Primes p and q Using an Approved Hash Function.
278
279=item A.2.3 Generation of canonical generator g.
280
281=item A.2.1 Unverifiable Generation of the Generator g.
282
283=back
284
285=head1 SEE ALSO
286
287L<EVP_PKEY-FFC(7)>,
288L<EVP_KEYEXCH-DH(7)>
289L<EVP_PKEY(3)>,
290L<provider-keymgmt(7)>,
291L<EVP_KEYMGMT(3)>,
292L<OSSL_PROVIDER-default(7)>,
293L<OSSL_PROVIDER-FIPS(7)>
294
295=head1 COPYRIGHT
296
f5afac4b 297Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
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298
299Licensed under the Apache License 2.0 (the "License"). You may not use
300this file except in compliance with the License. You can obtain a copy
301in the file LICENSE in the source distribution or at
302L<https://www.openssl.org/source/license.html>.
303
304=cut