doc: add PBKDF1 provider documentation

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15967)

doc/man7/EVP_KDF-PBKDF1.pod

@@ -0,0 +1,82 @@
+=pod
+
+=head1 NAME
+
+EVP_KDF-PBKDF1 - The PBKDF1 EVP_KDF implementation
+
+=head1 DESCRIPTION
+
+Support for computing the B<PBKDF1> password-based KDF through the B<EVP_KDF>
+API.
+
+The EVP_KDF-PBKDF1 algorithm implements the PBKDF1 password-based key
+derivation function, as described in RFC 8018; it derives a key from a password
+using a salt and iteration count.
+
+=head2 Identity
+
+"PBKDF1" 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 "pass" (B<OSSL_KDF_PARAM_PASSWORD>) <octet string>
+
+=item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
+
+=item "iter" (B<OSSL_KDF_PARAM_ITER>) <unsigned integer>
+
+This parameter has a default value of 0 and should be set.
+
+=item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
+
+=item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
+
+These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
+
+=back
+
+=head1 NOTES
+
+A typical application of this algorithm is to derive keying material for an
+encryption algorithm from a password in the "pass", a salt in "salt",
+and an iteration count.
+
+Increasing the "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
+
+RFC 8018
+
+=head1 SEE ALSO
+
+L<EVP_KDF(3)>,
+L<EVP_KDF_CTX_new(3)>,
+L<EVP_KDF_CTX_free(3)>,
+L<EVP_KDF_CTX_set_params(3)>,
+L<EVP_KDF_derive(3)>,
+L<EVP_KDF(3)/PARAMETERS>
+
+=head1 HISTORY
+
+This functionality was added to OpenSSL 3.0.
+
+=head1 COPYRIGHT
+
+Copyright 2021 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