=pod

=head1 NAME

OSSL_CMP_validate_msg,
OSSL_CMP_validate_cert_path
- functions for verifying CMP message protection

=head1 SYNOPSIS

 #include <openssl/cmp.h>
 int OSSL_CMP_validate_msg(OSSL_CMP_CTX *ctx, OSSL_CMP_MSG *msg);
 int OSSL_CMP_validate_cert_path(const OSSL_CMP_CTX *ctx,
                                 X509_STORE *trusted_store, X509 *cert);

=head1 DESCRIPTION

This is the API for validating the protection of CMP messages,
which includes validating CMP message sender certificates and their paths
while optionally checking the revocation status of the certificates(s).

OSSL_CMP_validate_msg() validates the protection of the given I<msg>,
which must be signature-based or using password-based MAC (PBM).
In the former case a suitable trust anchor must be given in the CMP context
I<ctx>, and in the latter case the matching secret must have been set there
using L<OSSL_CMP_CTX_set1_secretValue(3)>.

In case of signature algorithm, the certificate to use for the signature check
is preferably the one provided by a call to L<OSSL_CMP_CTX_set1_srvCert(3)>.
If no such sender cert has been pinned then candidate sender certificates are
taken from the list of certificates received in the I<msg> extraCerts, then any
certificates provided before via L<OSSL_CMP_CTX_set1_untrusted(3)>, and
then all trusted certificates provided via L<OSSL_CMP_CTX_set0_trusted(3)>.
A candidate certificate is acceptable only if it is currently valid
(or the trust store contains a verification callback that overrides the verdict
that the certificate is expired or not yet valid), its subject DN matches
the I<msg> sender DN (as far as present), and its subject key identifier
is present and matches the senderKID (as far as the latter is present).
Each acceptable cert is tried in the given order to see if the message
signature check succeeds and the cert and its path can be verified
using any trust store set via L<OSSL_CMP_CTX_set0_trusted(3)>.

If the option OSSL_CMP_OPT_PERMIT_TA_IN_EXTRACERTS_FOR_IR was set by calling
L<OSSL_CMP_CTX_set_option(3)>, for an Initialization Response (IP) message
any self-issued certificate from the I<msg> extraCerts field may be used
as a trust anchor for the path verification of an 'acceptable' cert if it can be
used also to validate the issued certificate returned in the IP message. This is
according to TS 33.310 [Network Domain Security (NDS); Authentication Framework
(AF)] document specified by The 3rd Generation Partnership Project (3GPP).
Note that using this option is dangerous as the certificate obtained this way
has not been authenticated (at least not at CMP level).
Taking it over as a trust anchor implements trust-on-first-use (TOFU).

Any cert that has been found as described above is cached and tried first when
validating the signatures of subsequent messages in the same transaction.

OSSL_CMP_validate_cert_path() attempts to validate the given certificate and its
path using the given store of trusted certs (possibly including CRLs and a cert
verification callback) and non-trusted intermediate certs from the I<ctx>.

=head1 NOTES

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

=head1 RETURN VALUES

OSSL_CMP_validate_msg() and OSSL_CMP_validate_cert_path()
return 1 on success, 0 on error or validation failed.

=head1 SEE ALSO

L<OSSL_CMP_CTX_new(3)>, L<OSSL_CMP_exec_certreq(3)>,
L<OSSL_CMP_CTX_set1_secretValue(3)>, L<OSSL_CMP_CTX_set1_srvCert(3)>,
L<OSSL_CMP_CTX_set1_untrusted(3)>, L<OSSL_CMP_CTX_set0_trusted(3)>

=head1 HISTORY

The OpenSSL CMP support was added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2007-2025 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
