EVP: Add EVP_PKEY_set_type_by_keymgmt() and use it

This function intialises an EVP_PKEY to contain a provider side internal
key.

We take the opportunity to also document the older EVP_PKEY_set_type()
and EVP_PKEY_set_type_str().

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11375)

1 files changed, 68 insertions, 0 deletions

diff --git a/doc/man3/EVP_PKEY_set_type.pod b/doc/man3/EVP_PKEY_set_type.pod
new file mode 100644
index 0000000000..e5111a555b
--- /dev/null
+++ b/doc/man3/EVP_PKEY_set_type.pod
@@ -0,0 +1,68 @@
+=pod
+
+=head1 NAME
+
+EVP_PKEY_set_type, EVP_PKEY_set_type_str, EVP_PKEY_set_type_by_keymgmt
+- functions to change the EVP_PKEY type
+
+=head1 SYNOPSIS
+
+ #include <openssl/evp.h>
+
+ int EVP_PKEY_set_type(EVP_PKEY *pkey, int type);
+ int EVP_PKEY_set_type_str(EVP_PKEY *pkey, const char *str, int len);
+ int EVP_PKEY_set_type_by_keymgmt(EVP_PKEY *pkey, EVP_KEYMGMT *keymgmt);
+
+=head1 DESCRIPTION
+
+All the functions described here behave the same in so far that they
+clear all the previous key data and methods from I<pkey>, and reset it
+to be of the type of key given by the different arguments.  If
+I<pkey> is NULL, these functions will still return the same return
+values as if it wasn't.
+
+EVP_PKEY_set_type() initialises I<pkey> to contain an internal legacy
+key.  When doing this, it finds a L<EVP_PKEY_ASN1_METHOD(3)>
+corresponding to I<type>, and associates I<pkey> with the findings.
+It is an error if no L<EVP_PKEY_ASN1_METHOD(3)> could be found for
+I<type>.
+
+EVP_PKEY_set_type_str() initialises I<pkey> to contain an internal legacy
+key. When doing this, it finds a L<EVP_PKEY_ASN1_METHOD(3)>
+corresponding to I<str> that has then length I<len>, and associates
+I<pkey> with the findings.
+It is an error if no L<EVP_PKEY_ASN1_METHOD(3)> could be found for
+I<type>.
+
+For both EVP_PKEY_set_type() and EVP_PKEY_set_type_str(), I<pkey> gets
+a numeric type, which can be retrieved with L<EVP_PKEY_id(3)>.  This
+numeric type is taken from the L<EVP_PKEY_ASN1_METHOD(3)> that was
+found, and is equal to or closely related to I<type> in the case of
+EVP_PKEY_set_type(), or related to I<str> in the case of
+EVP_PKEY_set_type_str().
+
+EVP_PKEY_set_type_by_keymgmt() initialises I<pkey> to contain an
+internal provider side key.  When doing this, it associates I<pkey>
+with I<keymgmt>.  For keys initialised like this, the numeric type
+retrieved with L<EVP_PKEY_id(3)> will always be B<EVP_PKEY_NONE>.
+
+=head1 RETURN VALUES
+
+All functions described here return 1 if successful, or 0 on error.
+
+=head1 SEE ALSO
+
+L<EVP_PKEY_assign(3)>, L<EVP_PKEY_id(3)>, L<EVP_PKEY_get0_RSA(3)>,
+L<EVP_PKEY_copy_parameters(3)>, L<EVP_PKEY_ASN1_METHOD(3)>,
+L<EVP_KEYMGMT(3)>
+
+=head1 COPYRIGHT
+
+Copyright 2020 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