SSL_CTX_set_session_id_context, SSL_set_session_id_context - set context within which session can be

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       Licensed under the Apache License 2.0 (the "License").  You may not use this file  except  in  compliance
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3.5.0                                              2025-06-04               SSL_CTX_SET_SESSION_ID_CONTEXT(3SSL)

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.

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

       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.

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)

        #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);

       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.