=pod

=head1 NAME

SSL_get_ex_data_X509_STORE_CTX_idx - get ex_data index to access SSL structure
from X509_STORE_CTX

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 int SSL_get_ex_data_X509_STORE_CTX_idx(void);

=head1 DESCRIPTION

SSL_get_ex_data_X509_STORE_CTX_idx() returns the index number under which
the pointer to the SSL object is stored into the X509_STORE_CTX object.

=head1 NOTES

Whenever a X509_STORE_CTX object is created for the verification of the
peers certificate during a handshake, a pointer to the SSL object is
stored into the X509_STORE_CTX object to identify the connection affected.
To retrieve this pointer the X509_STORE_CTX_get_ex_data() function can
be used with the correct index. This index is globally the same for all
X509_STORE_CTX objects and can be retrieved using
SSL_get_ex_data_X509_STORE_CTX_idx(). The index value is set when
SSL_get_ex_data_X509_STORE_CTX_idx() is first called either by the application
program directly or indirectly during other SSL setup functions or during
the handshake.

The value depends on other index values defined for X509_STORE_CTX objects
before the SSL index is created.

=head1 RETURN VALUES

=over 4

=item E<gt>=0

The index value to access the pointer.

=item E<lt>0

An error occurred, check the error stack for a detailed error message.

=back

=head1 EXAMPLES

The index returned from SSL_get_ex_data_X509_STORE_CTX_idx() allows to
access the SSL object for the connection to be accessed during the
verify_callback() when checking the peers certificate. Please check
the example in L<SSL_CTX_set_verify(3)|SSL_CTX_set_verify(3)>,

=head1 SEE ALSO

L<ssl(3)|ssl(3)>, L<SSL_CTX_set_verify(3)|SSL_CTX_set_verify(3)>,
L<CRYPTO_set_ex_data(3)|CRYPTO_set_ex_data(3)>

=cut