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_SSL_SESSION_ID_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_SSL_SESSION_ID_LENGTH. The
error is logged to the error stack.
