NAME

       SSL_CTX_set_session_id_context, SSL_set_session_id_context - set context within which
       session can be reused (server side only)

SYNOPSIS

        #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);

DESCRIPTION

       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.

NOTES

       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.

WARNINGS

       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.

RETURN VALUES

       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.

SEE ALSO

       ssl(7)

COPYRIGHT

       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>.