SSL_CTX_set_session_id_context, SSL_set_session_id_context - set context within
which session can be reused (server side only)
#include <openssl/ssl.h>
int SSL_CTX_set_session_id_context(SSL_CTX *ctx, const unsigned char *sid_ctx,
unsigned int sid_ctx_len);
int SSL_set_session_id_context(SSL *ssl, const unsigned char *sid_ctx,
unsigned int sid_ctx_len);
SSL_CTX_set_session_id_context() sets the context
sid_ctx of
length
sid_ctx_len within which a session can be reused for the
ctx object.
SSL_set_session_id_context() sets the context
sid_ctx of length
sid_ctx_len within which a session can be reused for the
ssl
object.
Sessions are generated within a certain context. When exporting/importing
sessions with
i2d_SSL_SESSION/
d2i_SSL_SESSION it would be
possible, to re-import a session generated from another context (e.g. another
application), which might lead to malfunctions. Therefore, each application
must set its own session id context
sid_ctx which is used to
distinguish the contexts and is stored in exported sessions. The
sid_ctx can be any kind of binary data with a given length, it is
therefore possible to use e.g. the name of the application and/or the hostname
and/or service name ...
The session id context becomes part of the session. The session id context is
set by the SSL/TLS server. The
SSL_CTX_set_session_id_context() and
SSL_set_session_id_context() functions are therefore only useful on the
server side.
OpenSSL clients will check the session id context returned by the server when
reusing a session.
The maximum length of the
sid_ctx is limited to
SSL_MAX_SID_CTX_LENGTH.
If the session id context is not set on an SSL/TLS server and client
certificates are used, stored sessions will not be reused but a fatal error
will be flagged and the handshake will fail.
If a server returns a different session id context to an OpenSSL client when
reusing a session, an error will be flagged and the handshake will fail.
OpenSSL servers will always return the correct session id context, as an
OpenSSL server checks the session id context itself before reusing a session
as described above.
SSL_CTX_set_session_id_context() and
SSL_set_session_id_context()
return the following values:
- 0
- The length sid_ctx_len of the session id context
sid_ctx exceeded the maximum allowed length of
SSL_MAX_SID_CTX_LENGTH. The error is logged to the error
stack.
- 1
- The operation succeeded.
ssl(7)
Copyright 2001-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (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
<
https://www.openssl.org/source/license.html>.