| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | SSL_CTX_set_session_id_context, SSL_set_session_id_context - set context within which session can be reused (server side only)
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/ssl.h>
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| 10 |
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| 11 | int SSL_CTX_set_session_id_context(SSL_CTX *ctx, const unsigned char *sid_ctx,
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| 12 | unsigned int sid_ctx_len);
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| 13 | int SSL_set_session_id_context(SSL *ssl, const unsigned char *sid_ctx,
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| 14 | unsigned int sid_ctx_len);
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| 15 |
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| 16 | =head1 DESCRIPTION
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| 17 |
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| 18 | SSL_CTX_set_session_id_context() sets the context B<sid_ctx> of length
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| 19 | B<sid_ctx_len> within which a session can be reused for the B<ctx> object.
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| 20 |
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| 21 | SSL_set_session_id_context() sets the context B<sid_ctx> of length
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| 22 | B<sid_ctx_len> within which a session can be reused for the B<ssl> object.
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| 23 |
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| 24 | =head1 NOTES
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| 25 |
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| 26 | Sessions are generated within a certain context. When exporting/importing
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| 27 | sessions with B<i2d_SSL_SESSION>/B<d2i_SSL_SESSION> it would be possible,
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| 28 | to re-import a session generated from another context (e.g. another
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| 29 | application), which might lead to malfunctions. Therefore, each application
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| 30 | must set its own session id context B<sid_ctx> which is used to distinguish
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| 31 | the contexts and is stored in exported sessions. The B<sid_ctx> can be
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| 32 | any kind of binary data with a given length, it is therefore possible
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| 33 | to use e.g. the name of the application and/or the hostname and/or service
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| 34 | name ...
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| 35 |
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| 36 | The session id context becomes part of the session. The session id context
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| 37 | is set by the SSL/TLS server. The SSL_CTX_set_session_id_context() and
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| 38 | SSL_set_session_id_context() functions are therefore only useful on the
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| 39 | server side.
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| 40 |
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| 41 | OpenSSL clients will check the session id context returned by the server
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| 42 | when reusing a session.
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| 43 |
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| 44 | The maximum length of the B<sid_ctx> is limited to
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| 45 | B<SSL_MAX_SID_CTX_LENGTH>.
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| 46 |
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| 47 | =head1 WARNINGS
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| 48 |
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| 49 | If the session id context is not set on an SSL/TLS server and client
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| 50 | certificates are used, stored sessions
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| 51 | will not be reused but a fatal error will be flagged and the handshake
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| 52 | will fail.
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| 53 |
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| 54 | If a server returns a different session id context to an OpenSSL client
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| 55 | when reusing a session, an error will be flagged and the handshake will
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| 56 | fail. OpenSSL servers will always return the correct session id context,
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| 57 | as an OpenSSL server checks the session id context itself before reusing
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| 58 | a session as described above.
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| 59 |
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| 60 | =head1 RETURN VALUES
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| 61 |
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| 62 | SSL_CTX_set_session_id_context() and SSL_set_session_id_context()
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| 63 | return the following values:
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| 64 |
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| 65 | =over 4
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| 66 |
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| 67 | =item Z<>0
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| 68 |
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| 69 | The length B<sid_ctx_len> of the session id context B<sid_ctx> exceeded
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| 70 | the maximum allowed length of B<SSL_MAX_SID_CTX_LENGTH>. The error
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| 71 | is logged to the error stack.
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| 72 |
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| 73 | =item Z<>1
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| 74 |
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| 75 | The operation succeeded.
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| 76 |
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| 77 | =back
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| 78 |
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| 79 | =head1 SEE ALSO
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| 80 |
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| 81 | L<ssl(7)>
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| 82 |
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| 83 | =head1 COPYRIGHT
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| 84 |
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| 85 | Copyright 2001-2020 The OpenSSL Project Authors. All Rights Reserved.
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| 86 |
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| 87 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 88 | this file except in compliance with the License. You can obtain a copy
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| 89 | in the file LICENSE in the source distribution or at
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| 90 | L<https://www.openssl.org/source/license.html>.
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| 91 |
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| 92 | =cut
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