NAME

       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
       functions

SYNOPSIS

        #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);

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_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.

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_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.

1.0.2g                                             2016-01-28                 SSL_CTX_set_tlsext_status_cb(3SSL)