Update KDF documentation (section 7)

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9662)

1 files changed, 104 insertions, 0 deletions

diff --git a/doc/man7/EVP_KDF-PBKDF2.pod b/doc/man7/EVP_KDF-PBKDF2.pod
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+=pod
+
+=head1 NAME
+
+EVP_KDF-PBKDF2 - The PBKDF2 EVP_KDF implementation
+
+=head1 DESCRIPTION
+
+Support for computing the B<PBKDF2> password-based KDF through the B<EVP_KDF>
+API.
+
+The EVP_KDF-PBKDF2 algorithm implements the PBKDF2 password-based key
+derivation function, as described in SP800-132; it derives a key from a password
+using a salt and iteration count.
+
+=head2 Identity
+
+"PBKDF2" is the name for this implementation; it
+can be used with the EVP_KDF_fetch() function.
+
+=head2 Supported parameters
+
+The supported parameters are:
+
+=over 4
+
+=item B<OSSL_KDF_PARAM_PASSWORD> ("pass") <octet string>
+
+=item B<OSSL_KDF_PARAM_SALT> ("salt") <octet string>
+
+=item B<OSSL_KDF_PARAM_ITER> ("iter") <unsigned int>
+
+This parameter has a default value of 2048.
+
+=item B<OSSL_KDF_PARAM_PROPERTIES> ("properties") <UTF8 string>
+
+=item B<OSSL_KDF_PARAM_DIGEST> ("digest") <UTF8 string>
+
+These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
+
+=item B<OSSL_KDF_PARAM_PKCS5> ("pkcs5") <int>
+
+This parameter can be used to enable or disable SP800-132 compliance checks.
+Setting the mode to 0 enables the compliance checks.
+
+The checks performed are:
+
+=over 4
+
+=item - the iteration count is at least 1000.
+
+=item - the salt length is at least 128 bits.
+
+=item - the derived key length is at least 112 bits.
+
+=back
+
+The default provider uses a default mode of 1 for backwards compatibility,
+and the fips provider uses a default mode of 0.
+
+The value string is expected to be a decimal number 0 or 1.
+
+=back
+
+=head1 NOTES
+
+A typical application of this algorithm is to derive keying material for an
+encryption algorithm from a password in the B<pass>, a salt in B<salt>,
+and an iteration count.
+
+Increasing the B<iter> parameter slows down the algorithm which makes it
+harder for an attacker to perform a brute force attack using a large number
+of candidate passwords.
+
+No assumption is made regarding the given password; it is simply treated as a
+byte sequence.
+
+=head1 CONFORMING TO
+
+SP800-132
+
+=head1 SEE ALSO
+
+L<EVP_KDF>,
+L<EVP_KDF-CTX_new_id(3)>,
+L<EVP_KDF-CTX_free(3)>,
+L<EVP_KDF-ctrl(3)>,
+L<EVP_KDF-derive(3)>,
+L<EVP_KDF-CTX(3)/PARAMETERS>
+
+=head1 HISTORY
+
+This functionality was added to OpenSSL 3.0.
+
+=head1 COPYRIGHT
+
+Copyright 2018-2019 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the Apache License 2.0 (the "License").  You may not use
+this file except in compliance with the License.  You can obtain a copy
+in the file LICENSE in the source distribution or at
+L<https://www.openssl.org/source/license.html>.
+
+=cut