6783944f89
Reviewed-by: Paul Dale <paul.dale@oracle.com> Reviewed-by: Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/9008)
146 lines
3.6 KiB
Text
146 lines
3.6 KiB
Text
=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 Numeric identity
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B<EVP_KDF_TLS1_PRF> is the numeric identity for this implementation; it
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can be used with the EVP_KDF_CTX_new_id() function.
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=head2 Supported controls
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The supported controls are:
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=over 4
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=item B<EVP_KDF_CTRL_SET_MD>
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This control works as described in L<EVP_KDF_CTX(3)/CONTROLS>.
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The C<EVP_KDF_CTRL_SET_MD> control is used to set the message digest associated
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with the TLS PRF. 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 B<EVP_KDF_CTRL_SET_TLS_SECRET>
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This control expects two arguments: C<unsigned char *sec>, C<size_t seclen>
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Sets the secret value of the TLS PRF to B<seclen> bytes of the buffer B<sec>.
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Any existing secret value is replaced.
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EVP_KDF_ctrl_str() takes two type strings for this control:
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=over 4
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=item "secret"
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The value string is used as is.
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=item "hexsecret"
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The value string is expected to be a hexadecimal number, which will be
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decoded before being passed on as the control value.
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=back
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=item B<EVP_KDF_CTRL_RESET_TLS_SEED>
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This control does not expect any arguments.
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Resets the context seed buffer to zero length.
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=item B<EVP_KDF_CTRL_ADD_TLS_SEED>
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This control expects two arguments: C<unsigned char *seed>, C<size_t seedlen>
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Sets the seed to B<seedlen> bytes of B<seed>. If a seed is already set it is
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appended to the existing value.
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The total length of the context seed buffer 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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EVP_KDF_ctrl_str() takes two type strings for this control:
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=over 4
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=item "seed"
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The value string is used as is.
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=item "hexseed"
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The value string is expected to be a hexadecimal number, which will be
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decoded before being passed on as the control value.
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=back
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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_CTX *kctx = EVP_KDF_CTX_new_id(EVP_KDF_TLS1_PRF, NULL);
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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 C<keylen> parameter to the
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EVP_KDF_derive() function.
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=head1 EXAMPLE
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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_CTX *kctx;
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unsigned char out[10];
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kctx = EVP_KDF_CTX_new_id(EVP_KDF_TLS1_PRF);
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if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_MD, EVP_sha256()) <= 0) {
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error("EVP_KDF_CTRL_SET_MD");
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}
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if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_TLS_SECRET,
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"secret", (size_t)6) <= 0) {
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error("EVP_KDF_CTRL_SET_TLS_SECRET");
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}
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if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_ADD_TLS_SEED, "seed", (size_t)4) <= 0) {
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error("EVP_KDF_CTRL_ADD_TLS_SEED");
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}
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if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 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_CTX>,
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L<EVP_KDF_CTX_new_id(3)>,
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L<EVP_KDF_CTX_free(3)>,
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L<EVP_KDF_ctrl(3)>,
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L<EVP_KDF_derive(3)>,
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L<EVP_KDF_CTX(3)/CONTROLS>
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=head1 COPYRIGHT
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Copyright 2018 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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