ssl_ctx_set_session_id_context(3)
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_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.
- 1 The operation succeeded.