SSL_CTX_SET_SESSION_I... BSD Library Functions Manual SSL_CTX_SET_SESSION_I...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);
DESCRIPTIONSSL_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/import‐
ing sessions with i2d_SSL_SESSION(3) and d2i_SSL_SESSION(3), 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 pos‐
sible to use, for instance, the name of the application, the hostname,
the service name...
The session id context becomes part of the session. The session id con‐
text 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_SSL_SESSION_ID_LENGTH.
WARNINGS
If the session id context is not set on an SSL/TLS server and client cer‐
tificates 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 VALUESSSL_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_SSL_SESSION_ID_LENGTH. The
error is logged to the error stack.
1 The operation succeeded.
SEE ALSOssl(3)BSD April 25, 2024 BSD
