.\"	$OpenBSD: SSL_get_ex_data_X509_STORE_CTX_idx.3,v 1.5 2022/02/06 00:29:02 jsg Exp $
.\"	OpenSSL 9b86974e Aug 17 15:21:33 2015 -0400
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.Dd $Mdocdate: February 6 2022 $
.Dt SSL_GET_EX_DATA_X509_STORE_CTX_IDX 3
.Os
.Sh NAME
.Nm SSL_get_ex_data_X509_STORE_CTX_idx
.Nd get ex_data index to access SSL structure from X509_STORE_CTX
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft int
.Fn SSL_get_ex_data_X509_STORE_CTX_idx void
.Sh DESCRIPTION
.Fn SSL_get_ex_data_X509_STORE_CTX_idx
returns the index number under which the pointer to the
.Vt SSL
object is stored into the
.Vt X509_STORE_CTX
object.
.Pp
Whenever a
.Vt X509_STORE_CTX
object is created for the verification of the peer's certificate during a
handshake, a pointer to the
.Vt SSL
object is stored into the
.Vt X509_STORE_CTX
object to identify the connection affected.
To retrieve this pointer the
.Xr X509_STORE_CTX_get_ex_data 3
function can be used with the correct index.
This index is globally the same for all
.Vt X509_STORE_CTX
objects and can be retrieved using
.Fn SSL_get_ex_data_X509_STORE_CTX_idx .
The index value is set when
.Fn 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.
.Pp
The value depends on other index values defined for
.Vt X509_STORE_CTX
objects before the SSL index is created.
.Sh RETURN VALUES
.Bl -tag -width Ds
.It \(>=0
The index value to access the pointer.
.It <0
An error occurred, check the error stack for a detailed error message.
.El
.Sh EXAMPLES
The index returned from
.Fn SSL_get_ex_data_X509_STORE_CTX_idx
provides access to
.Vt SSL
object for the connection during the
.Fn verify_callback
when checking the peer's certificate.
Check the example in
.Xr SSL_CTX_set_verify 3 .
.Sh SEE ALSO
.Xr CRYPTO_set_ex_data 3 ,
.Xr ssl 3 ,
.Xr SSL_CTX_set_verify 3
.Sh HISTORY
.Fn SSL_get_ex_data_X509_STORE_CTX_idx
first appeared in SSLeay 0.9.1 and has been available since
.Ox 2.6 .