1SSL_CTX_set_session_id_context(3)   OpenSSL  SSL_CTX_set_session_id_context(3)
2
3
4

NAME

6       SSL_CTX_set_session_id_context, SSL_set_session_id_context - set con‐
7       text within which session can be reused (server side only)
8

SYNOPSIS

10        #include <openssl/ssl.h>
11
12        int SSL_CTX_set_session_id_context(SSL_CTX *ctx, const unsigned char *sid_ctx,
13                                           unsigned int sid_ctx_len);
14        int SSL_set_session_id_context(SSL *ssl, const unsigned char *sid_ctx,
15                                       unsigned int sid_ctx_len);
16

DESCRIPTION

18       SSL_CTX_set_session_id_context() sets the context sid_ctx of length
19       sid_ctx_len within which a session can be reused for the ctx object.
20
21       SSL_set_session_id_context() sets the context sid_ctx of length
22       sid_ctx_len within which a session can be reused for the ssl object.
23

NOTES

25       Sessions are generated within a certain context. When exporting/import‐
26       ing sessions with i2d_SSL_SESSION/d2i_SSL_SESSION it would be possible,
27       to re-import a session generated from another context (e.g. another
28       application), which might lead to malfunctions. Therefore each applica‐
29       tion must set its own session id context sid_ctx which is used to dis‐
30       tinguish the contexts and is stored in exported sessions. The sid_ctx
31       can be any kind of binary data with a given length, it is therefore
32       possible to use e.g. the name of the application and/or the hostname
33       and/or service name ...
34
35       The session id context becomes part of the session. The session id con‐
36       text is set by the SSL/TLS server. The SSL_CTX_set_session_id_context()
37       and SSL_set_session_id_context() functions are therefore only useful on
38       the server side.
39
40       OpenSSL clients will check the session id context returned by the
41       server when reusing a session.
42
43       The maximum length of the sid_ctx is limited to SSL_MAX_SSL_SES‐
44       SION_ID_LENGTH.
45

WARNINGS

47       If the session id context is not set on an SSL/TLS server and client
48       certificates are used, stored sessions will not be reused but a fatal
49       error will be flagged and the handshake will fail.
50
51       If a server returns a different session id context to an OpenSSL client
52       when reusing a session, an error will be flagged and the handshake will
53       fail. OpenSSL servers will always return the correct session id con‐
54       text, as an OpenSSL server checks the session id context itself before
55       reusing a session as described above.
56

RETURN VALUES

58       SSL_CTX_set_session_id_context() and SSL_set_session_id_context()
59       return the following values:
60
61       0   The length sid_ctx_len of the session id context sid_ctx exceeded
62           the maximum allowed length of SSL_MAX_SSL_SESSION_ID_LENGTH. The
63           error is logged to the error stack.
64
65       1   The operation succeeded.
66

SEE ALSO

68       ssl(3)
69
70
71
720.9.8b                            2004-06-14 SSL_CTX_set_session_id_context(3)
Impressum