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SSL_CTX_set_tlsext_status_cb(3)     OpenSSL    SSL_CTX_set_tlsext_status_cb(3)

       SSL_CTX_set_tlsext_status_cb, SSL_CTX_set_tlsext_status_arg,
       SSL_set_tlsext_status_type, SSL_get_tlsext_status_ocsp_resp,
       SSL_set_tlsext_status_ocsp_resp - OCSP Certificate Status Request

       libcrypto, -lcrypto

        #include <openssl/tls1.h>

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

        long SSL_set_tlsext_status_type(SSL *s, int type);

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

       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_set_tlsext_status_type() function 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. 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 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.

       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_set_tlsext_status_type() and SSL_set_tlsext_status_ocsp_resp()
       return 0 on error or 1 on success.

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

1.0.2k                            2016-01-30   SSL_CTX_set_tlsext_status_cb(3)