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Editing: SSL_set_session_id_context.3
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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" SSL_CTX_set_session_id_context, SSL_set_session_id_context \- set context within which session can be reused (server side only) .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #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); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\fBSSL_CTX_set_session_id_context()\fR sets the context \fBsid_ctx\fR of length \&\fBsid_ctx_len\fR within which a session can be reused for the \fBctx\fR object. .PP \&\fBSSL_set_session_id_context()\fR sets the context \fBsid_ctx\fR of length \&\fBsid_ctx_len\fR within which a session can be reused for the \fBssl\fR object. .SH "NOTES" .IX Header "NOTES" Sessions are generated within a certain context. When exporting/importing sessions with \fBi2d_SSL_SESSION\fR/\fBd2i_SSL_SESSION\fR 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 \fBsid_ctx\fR which is used to distinguish the contexts and is stored in exported sessions. The \fBsid_ctx\fR 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 ... .PP The session id context becomes part of the session. The session id context is set by the \s-1SSL/TLS\s0 server. The \fBSSL_CTX_set_session_id_context()\fR and \&\fBSSL_set_session_id_context()\fR functions are therefore only useful on the server side. .PP OpenSSL clients will check the session id context returned by the server when reusing a session. .PP The maximum length of the \fBsid_ctx\fR is limited to \&\fB\s-1SSL_MAX_SSL_SESSION_ID_LENGTH\s0\fR. .SH "WARNINGS" .IX Header "WARNINGS" If the session id context is not set on an \s-1SSL/TLS\s0 server and client certificates are used, stored sessions will not be reused but a fatal error will be flagged and the handshake will fail. .PP 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. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBSSL_CTX_set_session_id_context()\fR and \fBSSL_set_session_id_context()\fR return the following values: .IP "0" 4 The length \fBsid_ctx_len\fR of the session id context \fBsid_ctx\fR exceeded the maximum allowed length of \fB\s-1SSL_MAX_SSL_SESSION_ID_LENGTH\s0\fR. The error is logged to the error stack. .IP "1" 4 .IX Item "1" The operation succeeded. .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBssl\fR\|(3)
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