NAME

       SSL_CTX_set_tlsext_status_cb, SSL_CTX_get_tlsext_status_cb, SSL_CTX_set_tlsext_status_arg,
       SSL_CTX_get_tlsext_status_arg, SSL_CTX_set_tlsext_status_type,
       SSL_CTX_get_tlsext_status_type, SSL_set_tlsext_status_type, SSL_get_tlsext_status_type,
       SSL_get_tlsext_status_ocsp_resp, SSL_set_tlsext_status_ocsp_resp - OCSP Certificate Status
       Request functions

SYNOPSIS

        #include <openssl/tls1.h>

        long SSL_CTX_set_tlsext_status_cb(SSL_CTX *ctx, int (*callback)(SSL *, void *));
        long SSL_CTX_get_tlsext_status_cb(SSL_CTX *ctx, int (**callback)(SSL *, void *));

        long SSL_CTX_set_tlsext_status_arg(SSL_CTX *ctx, void *arg);
        long SSL_CTX_get_tlsext_status_arg(SSL_CTX *ctx, void **arg);

        long SSL_CTX_set_tlsext_status_type(SSL_CTX *ctx, int type);
        long SSL_CTX_get_tlsext_status_type(SSL_CTX *ctx);

        long SSL_set_tlsext_status_type(SSL *s, int type);
        long SSL_get_tlsext_status_type(SSL *s);

        long SSL_get_tlsext_status_ocsp_resp(ssl, unsigned char **resp);
        long SSL_set_tlsext_status_ocsp_resp(ssl, unsigned char *resp, int len);

DESCRIPTION

       A client application may request that a server send back an OCSP status response (also
       known as OCSP stapling). To do so the client should call the
       SSL_CTX_set_tlsext_status_type() function prior to the creation of any SSL objects.
       Alternatively an application can call the SSL_set_tlsext_status_type() function on an
       individual SSL object prior to the start of the handshake.  Currently the only supported
       type is TLSEXT_STATUSTYPE_ocsp. This value should be passed in the type argument. Calling
       SSL_CTX_get_tlsext_status_type() will return the type TLSEXT_STATUSTYPE_ocsp previously
       set via SSL_CTX_set_tlsext_status_type() or -1 if not set.

       The client should additionally provide a callback function to decide what to do with the
       returned OCSP response by calling SSL_CTX_set_tlsext_status_cb(). The callback function
       should determine whether the returned OCSP response is acceptable or not. The callback
       will be passed as an argument the value previously set via a call to
       SSL_CTX_set_tlsext_status_arg(). Note that the callback will not be called in the event of
       a handshake where session resumption occurs (because there are no Certificates exchanged
       in such a handshake).  The callback previously set via SSL_CTX_set_tlsext_status_cb() can
       be retrieved by calling SSL_CTX_get_tlsext_status_cb(), and the argument by calling
       SSL_CTX_get_tlsext_status_arg().

       On the client side SSL_get_tlsext_status_type() can be used to determine whether the
       client has previously called SSL_set_tlsext_status_type(). It will return
       TLSEXT_STATUSTYPE_ocsp if it has been called or -1 otherwise. On the server side
       SSL_get_tlsext_status_type() can be used to determine whether the client requested OCSP
       stapling. If the client requested it then this function will return
       TLSEXT_STATUSTYPE_ocsp, or -1 otherwise.

       The response returned by the server can be obtained via a call to
       SSL_get_tlsext_status_ocsp_resp(). The value *resp will be updated to point to the OCSP
       response data and the return value will be the length of that data.  Typically a callback
       would obtain an OCSP_RESPONSE object from this data via a call to the d2i_OCSP_RESPONSE()
       function. If the server has not provided any response data then *resp will be NULL and the
       return value from SSL_get_tlsext_status_ocsp_resp() will be -1.

       A server application must also call the SSL_CTX_set_tlsext_status_cb() function if it
       wants to be able to provide clients with OCSP Certificate Status responses. Typically the
       server callback would obtain the server certificate that is being sent back to the client
       via a call to SSL_get_certificate(); obtain the OCSP response to be sent back; and then
       set that response data by calling SSL_set_tlsext_status_ocsp_resp(). A pointer to the
       response data should be provided in the resp argument, and the length of that data should
       be in the len argument.

RETURN VALUES

       The callback when used on the client side should return a negative value on error; 0 if
       the response is not acceptable (in which case the handshake will fail) or a positive value
       if it is acceptable.

       The callback when used on the server side should return with either SSL_TLSEXT_ERR_OK
       (meaning that the OCSP response that has been set should be returned),
       SSL_TLSEXT_ERR_NOACK (meaning that an OCSP response should not be returned) or
       SSL_TLSEXT_ERR_ALERT_FATAL (meaning that a fatal error has occurred).

       SSL_CTX_set_tlsext_status_cb(), SSL_CTX_set_tlsext_status_arg(),
       SSL_CTX_set_tlsext_status_type(), SSL_set_tlsext_status_type() and
       SSL_set_tlsext_status_ocsp_resp() return 0 on error or 1 on success.

       SSL_CTX_get_tlsext_status_type() returns the value previously set by
       SSL_CTX_set_tlsext_status_type(), or -1 if not set.

       SSL_get_tlsext_status_ocsp_resp() returns the length of the OCSP response data or -1 if
       there is no OCSP response data.

       SSL_get_tlsext_status_type() returns TLSEXT_STATUSTYPE_ocsp on the client side if
       SSL_set_tlsext_status_type() was previously called, or on the server side if the client
       requested OCSP stapling. Otherwise -1 is returned.

HISTORY

       SSL_get_tlsext_status_type(), SSL_CTX_get_tlsext_status_type() and
       SSL_CTX_set_tlsext_status_type() were added in OpenSSL 1.1.0.

COPYRIGHT

       Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in
       compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.