1=pod 2 3=head1 NAME 4 5EVP_KDF-TLS1_PRF - The TLS1 PRF EVP_KDF implementation 6 7=head1 DESCRIPTION 8 9Support for computing the B<TLS1> PRF through the B<EVP_KDF> API. 10 11The EVP_KDF-TLS1_PRF algorithm implements the PRF used by TLS versions up to 12and including TLS 1.2. 13 14=head2 Identity 15 16"TLS1-PRF" is the name for this implementation; it 17can be used with the EVP_KDF_fetch() function. 18 19=head2 Supported parameters 20 21The supported parameters are: 22 23=over 4 24 25=item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string> 26 27=item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string> 28 29These parameters work as described in L<EVP_KDF(3)/PARAMETERS>. 30 31The B<OSSL_KDF_PARAM_DIGEST> parameter is used to set the message digest 32associated with the TLS PRF. 33EVP_md5_sha1() is treated as a special case which uses the 34PRF algorithm using both B<MD5> and B<SHA1> as used in TLS 1.0 and 1.1. 35 36=item "secret" (B<OSSL_KDF_PARAM_SECRET>) <octet string> 37 38This parameter sets the secret value of the TLS PRF. 39Any existing secret value is replaced. 40 41=item "seed" (B<OSSL_KDF_PARAM_SEED>) <octet string> 42 43This parameter sets the context seed. 44The length of the context seed cannot exceed 1024 bytes; 45this should be more than enough for any normal use of the TLS PRF. 46 47=back 48 49=head1 NOTES 50 51A context for the TLS PRF can be obtained by calling: 52 53 EVP_KDF *kdf = EVP_KDF_fetch(NULL, "TLS1-PRF", NULL); 54 EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf); 55 56The digest, secret value and seed must be set before a key is derived otherwise 57an error will occur. 58 59The output length of the PRF is specified by the I<keylen> parameter to the 60EVP_KDF_derive() function. 61 62=head1 EXAMPLES 63 64This example derives 10 bytes using SHA-256 with the secret key "secret" 65and seed value "seed": 66 67 EVP_KDF *kdf; 68 EVP_KDF_CTX *kctx; 69 unsigned char out[10]; 70 OSSL_PARAM params[4], *p = params; 71 72 kdf = EVP_KDF_fetch(NULL, "TLS1-PRF", NULL); 73 kctx = EVP_KDF_CTX_new(kdf); 74 EVP_KDF_free(kdf); 75 76 *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST, 77 SN_sha256, strlen(SN_sha256)); 78 *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET, 79 "secret", (size_t)6); 80 *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SEED, 81 "seed", (size_t)4); 82 *p = OSSL_PARAM_construct_end(); 83 if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) { 84 error("EVP_KDF_derive"); 85 } 86 EVP_KDF_CTX_free(kctx); 87 88=head1 CONFORMING TO 89 90RFC 2246, RFC 5246 and NIST SP 800-135 r1 91 92=head1 SEE ALSO 93 94L<EVP_KDF(3)>, 95L<EVP_KDF_CTX_new(3)>, 96L<EVP_KDF_CTX_free(3)>, 97L<EVP_KDF_CTX_set_params(3)>, 98L<EVP_KDF_derive(3)>, 99L<EVP_KDF(3)/PARAMETERS> 100 101=head1 HISTORY 102 103This functionality was added in OpenSSL 3.0. 104 105=head1 COPYRIGHT 106 107Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved. 108 109Licensed under the Apache License 2.0 (the "License"). You may not use 110this file except in compliance with the License. You can obtain a copy 111in the file LICENSE in the source distribution or at 112L<https://www.openssl.org/source/license.html>. 113 114=cut 115