xref: /openbsd-src/lib/libssl/man/SSL_clear.3 (revision 689a5e038eee38fafaea4f1560306028af829704)

.\"	$OpenBSD: SSL_clear.3,v 1.5 2021/06/11 19:41:39 jmc Exp $
.\"	OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
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.Dd $Mdocdate: June 11 2021 $
.Dt SSL_CLEAR 3
.Os
.Sh NAME
.Nm SSL_clear
.Nd reset SSL object to allow another connection
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft int
.Fn SSL_clear "SSL *ssl"
.Sh DESCRIPTION
Reset
.Fa ssl
to allow another connection.
All settings (method, ciphers, BIOs) are kept.
.Pp
.Fn SSL_clear
is used to prepare an
.Vt SSL
object for a new connection.
While all settings are kept,
a side effect is the handling of the current SSL session.
If a session is still
.Em open ,
it is considered bad and will be removed from the session cache,
as required by RFC 2246.
A session is considered open if
.Xr SSL_shutdown 3
was not called for the connection or at least
.Xr SSL_set_shutdown 3
was used to
set the
.Dv SSL_SENT_SHUTDOWN
state.
.Pp
If a session was closed cleanly,
the session object will be kept and all settings corresponding.
This explicitly means that for example the special method used during the
session will be kept for the next handshake.
So if the session was a TLSv1 session, a
.Vt SSL
client object will use a TLSv1 client method for the next handshake and a
.Vt SSL
server object will use a TLSv1 server method, even if
.Fn TLS_*_method Ns s
were chosen on startup.
This might lead to connection failures (see
.Xr SSL_new 3 )
for a description of the method's properties.
.Sh RETURN VALUES
The following return values can occur:
.Bl -tag -width Ds
.It 0
The
.Fn SSL_clear
operation could not be performed.
Check the error stack to find out the reason.
.It 1
The
.Fn SSL_clear
operation was successful.
.El
.Sh SEE ALSO
.Xr ssl 3 ,
.Xr SSL_CTX_set_client_cert_cb 3 ,
.Xr SSL_CTX_set_options 3 ,
.Xr SSL_free 3 ,
.Xr SSL_new 3 ,
.Xr SSL_set_shutdown 3 ,
.Xr SSL_shutdown 3
.Sh HISTORY
.Fn SSL_clear
first appeared in SSLeay 0.4.5b and has been available since
.Ox 2.4 .
.Sh CAVEATS
.Fn SSL_clear
resets the
.Vt SSL
object to allow for another connection.
The reset operation however keeps several settings of the last sessions
(some of these settings were made automatically during the last handshake).
It only makes sense for a new connection with the exact same peer that shares
these settings,
and may fail if that peer changes its settings between connections.
Use the sequence
.Xr SSL_get_session 3 ;
.Xr SSL_new 3 ;
.Xr SSL_set_session 3 ;
.Xr SSL_free 3
instead to avoid such failures (or simply
.Xr SSL_free 3 ;
.Xr SSL_new 3
if session reuse is not desired).