=pod

=head1 NAME

ossl_cmp_build_cert_chain,
ossl_cmp_calc_protection,
ossl_cmp_msg_protect,
ossl_cmp_msg_add_extraCerts
- functions for producing CMP message protection

=head1 SYNOPSIS

 #include "cmp_local.h"

 STACK_OF(X509)
     *ossl_cmp_build_cert_chain(OSSL_LIB_CTX *libctx, const char *propq,
                                X509_STORE *store,
                                STACK_OF(X509) *certs, X509 *cert);
 ASN1_BIT_STRING *ossl_cmp_calc_protection(const OSSL_CMP_CTX *ctx,
                                           const OSSL_CMP_MSG *msg);
 int ossl_cmp_msg_protect(OSSL_CMP_CTX *ctx, OSSL_CMP_MSG *msg);
 int ossl_cmp_msg_add_extraCerts(OSSL_CMP_CTX *ctx, OSSL_CMP_MSG *msg);

=head1 DESCRIPTION

ossl_cmp_build_cert_chain() builds a certificate chain starting from I<cert>
using the optional list of intermediate CA certificates I<certs>.
If I<store> is NULL builds the chain as far down as possible, ignoring errors.
Else the chain must reach a trust anchor contained in I<store>.
It internally uses a B<X509_STORE_CTX> structure associated with the library
context I<libctx> and property query string I<propq>, both of which may be NULL.
If a non-NULL stack is returned the caller is responsible for freeing it.
In case there is more than one possibility for the chain,
OpenSSL seems to take the first one; check L<X509_verify_cert(3)> for details.

ossl_cmp_calc_protection() calculates the protection for the given I<msg>
according to the algorithm and parameters in the message header's protectionAlg
using the credentials, library context, and property criteria in the I<ctx>.

ossl_cmp_msg_protect() (re-)protects the given message I<msg> using an algorithm
depending on the available context information given in the I<ctx>.
If there is a secretValue it selects PBMAC, else if there is a protection cert
it selects Signature and uses L<ossl_cmp_msg_add_extraCerts(3)>.
It also sets the protectionAlg field in the message header accordingly.

ossl_cmp_msg_add_extraCerts() adds elements to the extraCerts field in I<msg>.
If signature-based message protection is used it adds first the CMP signer cert
ctx->cert and then its chain ctx->chain. If this chain is not present in I<ctx>
tries to build it using ctx->untrusted and caches the result in ctx->chain.
In any case all the certificates explicitly specified to be sent out (i.e.,
I<ctx->extraCertsOut>) are added. Note that it will NOT add the root certificate
of the chain, i.e, the trust anchor (unless it is part of extraCertsOut).

=head1 NOTES

CMP is defined in RFC 4210 (and CRMF in RFC 4211).

=head1 RETURN VALUES

ossl_cmp_build_cert_chain() returns NULL on error,
else a pointer to a stack of (up_ref'ed) certificates
starting with given EE certificate and followed by all available intermediate
certificates down towards (but excluding) any trusted root certificate.

ossl_cmp_calc_protection() returns the protection on success, else NULL.

All other functions return 1 on success, 0 on error.

=head1 HISTORY

The OpenSSL CMP support was added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2007-2020 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>.

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