=pod

=head1 NAME

SCT_validate, SCT_LIST_validate, SCT_get_validation_status -
checks Signed Certificate Timestamps (SCTs) are valid

=head1 SYNOPSIS

 #include <openssl/ct.h>

 typedef enum {
     SCT_VALIDATION_STATUS_NOT_SET,
     SCT_VALIDATION_STATUS_UNKNOWN_LOG,
     SCT_VALIDATION_STATUS_VALID,
     SCT_VALIDATION_STATUS_INVALID,
     SCT_VALIDATION_STATUS_UNVERIFIED,
     SCT_VALIDATION_STATUS_UNKNOWN_VERSION
 } sct_validation_status_t;

 int SCT_validate(SCT *sct, const CT_POLICY_EVAL_CTX *ctx);
 int SCT_LIST_validate(const STACK_OF(SCT) *scts, CT_POLICY_EVAL_CTX *ctx);
 sct_validation_status_t SCT_get_validation_status(const SCT *sct);

=head1 DESCRIPTION

SCT_validate() will check that an SCT is valid and verify its signature.
SCT_LIST_validate() performs the same checks on an entire stack of SCTs.
The result of the validation checks can be obtained by passing the SCT to
SCT_get_validation_status().

A CT_POLICY_EVAL_CTX must be provided that specifies:

=over 2

=item *

The certificate the SCT was issued for.

Failure to provide the certificate will result in the validation status being
SCT_VALIDATION_STATUS_UNVERIFIED.

=item *

The issuer of that certificate.

This is only required if the SCT was issued for a pre-certificate
(see RFC 6962). If it is required but not provided, the validation status will
be SCT_VALIDATION_STATUS_UNVERIFIED.

=item *

A CTLOG_STORE that contains the CT log that issued this SCT.

If the SCT was issued by a log that is not in this CTLOG_STORE, the validation
status will be SCT_VALIDATION_STATUS_UNKNOWN_LOG.

=back

If the SCT is of an unsupported version (only v1 is currently supported), the
validation status will be SCT_VALIDATION_STATUS_UNKNOWN_VERSION.

If the SCT's signature is incorrect, its timestamp is in the future (relative to
the time in CT_POLICY_EVAL_CTX), or if it is otherwise invalid, the validation
status will be SCT_VALIDATION_STATUS_INVALID.

If all checks pass, the validation status will be SCT_VALIDATION_STATUS_VALID.

=head1 NOTES

A return value of 0 from SCT_LIST_validate() should not be interpreted as a
failure. At a minimum, only one valid SCT may provide sufficient confidence
that a certificate has been publicly logged.

=head1 RETURN VALUES

SCT_validate() returns a negative integer if an internal error occurs, 0 if the
SCT fails validation, or 1 if the SCT passes validation.

SCT_LIST_validate() returns a negative integer if an internal error occurs, 0
if any of SCTs fails validation, or 1 if they all pass validation.

SCT_get_validation_status() returns the validation status of the SCT.
If SCT_validate() or SCT_LIST_validate() have not been passed that SCT, the
returned value will be SCT_VALIDATION_STATUS_NOT_SET.

=head1 SEE ALSO

L<ct(7)>

=head1 HISTORY

These functions were added in OpenSSL 1.1.0.

=head1 COPYRIGHT

Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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