=pod

=head1 NAME

X509_STORE_CTX_new, X509_STORE_CTX_cleanup, X509_STORE_CTX_free,
X509_STORE_CTX_init, X509_STORE_CTX_set0_trusted_stack, X509_STORE_CTX_set_cert,
X509_STORE_CTX_set0_crls,
X509_STORE_CTX_get0_chain, X509_STORE_CTX_set0_verified_chain,
X509_STORE_CTX_get0_param, X509_STORE_CTX_set0_param,
X509_STORE_CTX_get0_untrusted, X509_STORE_CTX_set0_untrusted,
X509_STORE_CTX_get_num_untrusted,
X509_STORE_CTX_set_default,
X509_STORE_CTX_set_verify,
X509_STORE_CTX_verify_fn
- X509_STORE_CTX initialisation

=head1 SYNOPSIS

 #include <openssl/x509_vfy.h>

 X509_STORE_CTX *X509_STORE_CTX_new(void);
 void X509_STORE_CTX_cleanup(X509_STORE_CTX *ctx);
 void X509_STORE_CTX_free(X509_STORE_CTX *ctx);

 int X509_STORE_CTX_init(X509_STORE_CTX *ctx, X509_STORE *store,
                         X509 *x509, STACK_OF(X509) *chain);

 void X509_STORE_CTX_set0_trusted_stack(X509_STORE_CTX *ctx, STACK_OF(X509) *sk);

 void X509_STORE_CTX_set_cert(X509_STORE_CTX *ctx, X509 *x);
 STACK_OF(X509) *X509_STORE_CTX_get0_chain(X509_STORE_CTX *ctx);
 void X509_STORE_CTX_set0_verified_chain(X509_STORE_CTX *ctx, STACK_OF(X509) *chain);
 void X509_STORE_CTX_set0_crls(X509_STORE_CTX *ctx, STACK_OF(X509_CRL) *sk);

 X509_VERIFY_PARAM *X509_STORE_CTX_get0_param(X509_STORE_CTX *ctx);
 void X509_STORE_CTX_set0_param(X509_STORE_CTX *ctx, X509_VERIFY_PARAM *param);
 int X509_STORE_CTX_set_default(X509_STORE_CTX *ctx, const char *name);

 STACK_OF(X509)* X509_STORE_CTX_get0_untrusted(X509_STORE_CTX *ctx);
 void X509_STORE_CTX_set0_untrusted(X509_STORE_CTX *ctx, STACK_OF(X509) *sk);

 int X509_STORE_CTX_get_num_untrusted(X509_STORE_CTX *ctx);

 typedef int (*X509_STORE_CTX_verify_fn)(X509_STORE_CTX *);
 void X509_STORE_CTX_set_verify(X509_STORE_CTX *ctx, X509_STORE_CTX_verify_fn verify);

=head1 DESCRIPTION

These functions initialise an B<X509_STORE_CTX> structure for subsequent use
by X509_verify_cert().

X509_STORE_CTX_new() returns a newly initialised B<X509_STORE_CTX> structure.

X509_STORE_CTX_cleanup() internally cleans up an B<X509_STORE_CTX> structure.
The context can then be reused with a new call to X509_STORE_CTX_init().

X509_STORE_CTX_free() completely frees up B<ctx>. After this call B<ctx>
is no longer valid.
If B<ctx> is NULL nothing is done.

X509_STORE_CTX_init() sets up B<ctx> for a subsequent verification operation.
It must be called before each call to X509_verify_cert(), i.e. a B<ctx> is only
good for one call to X509_verify_cert(); if you want to verify a second
certificate with the same B<ctx> then you must call X509_STORE_CTX_cleanup()
and then X509_STORE_CTX_init() again before the second call to
X509_verify_cert(). The trusted certificate store is set to B<store>, the end
entity certificate to be verified is set to B<x509> and a set of additional
certificates (which will be untrusted but may be used to build the chain) in
B<chain>. Any or all of the B<store>, B<x509> and B<chain> parameters can be
B<NULL>.

X509_STORE_CTX_set0_trusted_stack() sets the set of trusted certificates of
B<ctx> to B<sk>. This is an alternative way of specifying trusted certificates
instead of using an B<X509_STORE>.

X509_STORE_CTX_set_cert() sets the certificate to be verified in B<ctx> to
B<x>.

X509_STORE_CTX_set0_verified_chain() sets the validated chain used
by B<ctx> to be B<chain>.
Ownership of the chain is transferred to B<ctx> and should not be
free'd by the caller.
X509_STORE_CTX_get0_chain() returns the internal pointer used by the
B<ctx> that contains the validated chain.

X509_STORE_CTX_set0_crls() sets a set of CRLs to use to aid certificate
verification to B<sk>. These CRLs will only be used if CRL verification is
enabled in the associated B<X509_VERIFY_PARAM> structure. This might be
used where additional "useful" CRLs are supplied as part of a protocol,
for example in a PKCS#7 structure.

X509_STORE_CTX_get0_param() retrieves an internal pointer
to the verification parameters associated with B<ctx>.

X509_STORE_CTX_get0_untrusted() retrieves an internal pointer to the
stack of untrusted certificates associated with B<ctx>.

X509_STORE_CTX_set0_untrusted() sets the internal point to the stack
of untrusted certificates associated with B<ctx> to B<sk>.

X509_STORE_CTX_set0_param() sets the internal verification parameter pointer
to B<param>. After this call B<param> should not be used.

X509_STORE_CTX_set_default() looks up and sets the default verification
method to B<name>. This uses the function X509_VERIFY_PARAM_lookup() to
find an appropriate set of parameters from B<name>.

X509_STORE_CTX_get_num_untrusted() returns the number of untrusted certificates
that were used in building the chain following a call to X509_verify_cert().

X509_STORE_CTX_set_verify() provides the capability for overriding the default
verify function. This function is responsible for verifying chain signatures and
expiration times.

A verify function is defined as an X509_STORE_CTX_verify type which has the
following signature:

 int (*verify)(X509_STORE_CTX *);

This function should receive the current X509_STORE_CTX as a parameter and
return 1 on success or 0 on failure.

=head1 NOTES

The certificates and CRLs in a store are used internally and should B<not>
be freed up until after the associated B<X509_STORE_CTX> is freed.

=head1 BUGS

The certificates and CRLs in a context are used internally and should B<not>
be freed up until after the associated B<X509_STORE_CTX> is freed. Copies
should be made or reference counts increased instead.

=head1 RETURN VALUES

X509_STORE_CTX_new() returns a newly allocated context or B<NULL> if an
error occurred.

X509_STORE_CTX_init() returns 1 for success or 0 if an error occurred.

X509_STORE_CTX_get0_param() returns a pointer to an B<X509_VERIFY_PARAM>
structure or B<NULL> if an error occurred.

X509_STORE_CTX_cleanup(), X509_STORE_CTX_free(),
X509_STORE_CTX_set0_trusted_stack(),
X509_STORE_CTX_set_cert(),
X509_STORE_CTX_set0_crls() and X509_STORE_CTX_set0_param() do not return
values.

X509_STORE_CTX_set_default() returns 1 for success or 0 if an error occurred.

X509_STORE_CTX_get_num_untrusted() returns the number of untrusted certificates
used.

=head1 SEE ALSO

L<X509_verify_cert(3)>
L<X509_VERIFY_PARAM_set_flags(3)>

=head1 HISTORY

The X509_STORE_CTX_set0_crls() function was added in OpenSSL 1.0.0.
The X509_STORE_CTX_get_num_untrusted() function was added in OpenSSL 1.1.0.

=head1 COPYRIGHT

Copyright 2009-2020 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
