mirror of https://github.com/openssl/openssl.git
111 lines
3.0 KiB
Plaintext
111 lines
3.0 KiB
Plaintext
=pod
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=head1 NAME
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EVP_KDF-TLS1_PRF - The TLS1 PRF EVP_KDF implementation
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=head1 DESCRIPTION
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Support for computing the B<TLS1> PRF through the B<EVP_KDF> API.
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The EVP_KDF-TLS1_PRF algorithm implements the PRF used by TLS versions up to
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and including TLS 1.2.
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=head2 Identity
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"TLS1-PRF" is the name for this implementation; it
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can be used with the EVP_KDF_fetch() function.
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=head2 Supported parameters
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The supported parameters are:
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=over 4
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=item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
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=item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
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These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
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The B<OSSL_KDF_PARAM_DIGEST> parameter is used to set the message digest
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associated with the TLS PRF.
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EVP_md5_sha1() is treated as a special case which uses the
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PRF algorithm using both B<MD5> and B<SHA1> as used in TLS 1.0 and 1.1.
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=item "secret" (B<OSSL_KDF_PARAM_SECRET>) <octet string>
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This parameter sets the secret value of the TLS PRF.
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Any existing secret value is replaced.
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=item "seed" (B<OSSL_KDF_PARAM_SEED>) <octet string>
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This parameter sets the context seed.
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The length of the context seed cannot exceed 1024 bytes;
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this should be more than enough for any normal use of the TLS PRF.
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=back
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=head1 NOTES
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A context for the TLS PRF can be obtained by calling:
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EVP_KDF *kdf = EVP_KDF_fetch(NULL, "TLS1-PRF", NULL);
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EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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The digest, secret value and seed must be set before a key is derived otherwise
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an error will occur.
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The output length of the PRF is specified by the I<keylen> parameter to the
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EVP_KDF_derive() function.
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=head1 EXAMPLES
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This example derives 10 bytes using SHA-256 with the secret key "secret"
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and seed value "seed":
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EVP_KDF *kdf;
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EVP_KDF_CTX *kctx;
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unsigned char out[10];
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OSSL_PARAM params[4], *p = params;
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kdf = EVP_KDF_fetch(NULL, "TLS1-PRF", NULL);
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kctx = EVP_KDF_CTX_new(kdf);
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EVP_KDF_free(kdf);
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
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SN_sha256, strlen(SN_sha256));
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
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"secret", (size_t)6);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SEED,
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"seed", (size_t)4);
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*p = OSSL_PARAM_construct_end();
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if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
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error("EVP_KDF_derive");
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}
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EVP_KDF_CTX_free(kctx);
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=head1 CONFORMING TO
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RFC 2246, RFC 5246 and NIST SP 800-135 r1
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=head1 SEE ALSO
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L<EVP_KDF(3)>,
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L<EVP_KDF_CTX_new(3)>,
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L<EVP_KDF_CTX_free(3)>,
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L<EVP_KDF_CTX_set_params(3)>,
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L<EVP_KDF_derive(3)>,
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L<EVP_KDF(3)/PARAMETERS>
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=head1 COPYRIGHT
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Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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