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5366490822
Fixes #7894 This allows SHAKE to squeeze multiple times with different output sizes. The existing EVP_DigestFinalXOF() API has been left as a one shot operation. A similar interface is used by another toolkit. The low level SHA3_Squeeze() function needed to change slightly so that it can handle multiple squeezes. This involves changing the assembler code so that it passes a boolean to indicate whether the Keccak function should be called on entry. At the provider level, the squeeze is buffered, so that it only requests a multiple of the blocksize when SHA3_Squeeze() is called. On the first call the value is zero, on subsequent calls the value passed is 1. This PR is derived from the excellent work done by @nmathewson in https://github.com/openssl/openssl/pull/7921 Reviewed-by: Paul Dale <pauli@openssl.org> Reviewed-by: Tomas Mraz <tomas@openssl.org> (Merged from https://github.com/openssl/openssl/pull/21511)
97 lines
2.7 KiB
Plaintext
97 lines
2.7 KiB
Plaintext
=pod
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=head1 NAME
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EVP_MD-SHAKE, EVP_MD-KECCAK-KMAC
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- The SHAKE / KECCAK family EVP_MD implementations
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=head1 DESCRIPTION
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Support for computing SHAKE or KECCAK-KMAC digests through the
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B<EVP_MD> API.
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KECCAK-KMAC is a special digest that's used by the KMAC EVP_MAC
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implementation (see L<EVP_MAC-KMAC(7)>).
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=head2 Identities
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This implementation is available in the FIPS provider as well as the default
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provider, and includes the following varieties:
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=over 4
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=item KECCAK-KMAC-128
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Known names are "KECCAK-KMAC-128" and "KECCAK-KMAC128"
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This is used by L<EVP_MAC-KMAC128(7)>
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=item KECCAK-KMAC-256
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Known names are "KECCAK-KMAC-256" and "KECCAK-KMAC256"
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This is used by L<EVP_MAC-KMAC256(7)>
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=item SHAKE-128
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Known names are "SHAKE-128" and "SHAKE128"
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=item SHAKE-256
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Known names are "SHAKE-256" and "SHAKE256"
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=back
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=head2 Gettable Parameters
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This implementation supports the common gettable parameters described
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in L<EVP_MD-common(7)>.
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=head2 Settable Context Parameters
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These implementations support the following L<OSSL_PARAM(3)> entries,
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settable for an B<EVP_MD_CTX> with L<EVP_MD_CTX_set_params(3)>:
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=over 4
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=item "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>) <unsigned integer>
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Sets the digest length for extendable output functions.
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The length of the "xoflen" parameter should not exceed that of a B<size_t>.
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For backwards compatibility reasons the default xoflen length for SHAKE-128 is
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16 (bytes) which results in a security strength of only 64 bits. To ensure the
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maximum security strength of 128 bits, the xoflen should be set to at least 32.
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For backwards compatibility reasons the default xoflen length for SHAKE-256 is
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32 (bytes) which results in a security strength of only 128 bits. To ensure the
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maximum security strength of 256 bits, the xoflen should be set to at least 64.
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This parameter may be used when calling either EVP_DigestFinal_ex() or
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EVP_DigestFinal(), since these functions were not designed to handle variable
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length output. It is recommended to either use EVP_DigestSqueeze() or
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EVP_DigestFinalXOF() instead.
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=back
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=head1 NOTES
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For SHAKE-128, to ensure the maximum security strength of 128 bits, the output
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length passed to EVP_DigestFinalXOF() should be at least 32.
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For SHAKE-256, to ensure the maximum security strength of 256 bits, the output
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length passed to EVP_DigestFinalXOF() should be at least 64.
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=head1 SEE ALSO
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L<EVP_MD_CTX_set_params(3)>, L<provider-digest(7)>, L<OSSL_PROVIDER-default(7)>
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=head1 COPYRIGHT
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Copyright 2020-2023 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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