NAME

       gnutls_prf - API function

SYNOPSIS

       #include <gnutls/gnutls.h>

       int  gnutls_prf(gnutls_session_t  session,  size_t  label_size,  const  char  * label, int
       server_random_first, size_t extra_size, const char * extra, size_t outsize, char * out);

ARGUMENTS

       gnutls_session_t session
                   is a gnutls_session_t type.

       size_t label_size
                   length of the  label variable.

       const char * label
                   label used in PRF computation, typically a short string.

       int server_random_first
                   non-zero if server random field should be first in seed

       size_t extra_size
                   length of the  extra variable.

       const char * extra
                   optional extra data to seed the PRF with.

       size_t outsize
                   size of pre-allocated output buffer to hold the output.

       char * out  pre-allocated buffer to hold the generated data.

DESCRIPTION

       Applies the TLS Pseudo-Random-Function (PRF) on the master secret and the  provided  data,
       seeded  with  the  client  and  server  random fields.  For the key expansion specified in
       RFC5705 see gnutls_prf_rfc5705().

       The  label variable usually contains a string denoting the purpose for the generated data.
       The   server_random_first  indicates  whether the client random field or the server random
       field should be first in the seed.  Non-zero indicates that the  server  random  field  is
       first, 0 that the client random field is first.

       The   extra variable can be used to add more data to the seed, after the random variables.
       It can be used to make sure the generated output is strongly connected to some  additional
       data (e.g., a string used in user authentication).

       The output is placed in  out , which must be pre-allocated.

NOTE

       This    function    produces    identical    output    with    gnutls_prf_rfc5705()   when
       server_random_first is set to 0 and  extra is NULL. Under TLS1.3 this function  will  only
       operate when these conditions are true, or otherwise return GNUTLS_E_INVALID_REQUEST.

RETURNS

       GNUTLS_E_SUCCESS on success, or an error code.

REPORTING BUGS

       Report bugs to <bugs@gnutls.org>.
       Home page: https://www.gnutls.org

COPYRIGHT

       Copyright © 2001-2023 Free Software Foundation, Inc., and others.
       Copying  and distribution of this file, with or without modification, are permitted in any
       medium without royalty provided the copyright notice and this notice are preserved.

SEE ALSO

       The  full  documentation  for  gnutls  is  maintained  as  a  Texinfo  manual.    If   the
       /usr/share/doc/gnutls/ directory does not contain the HTML form visit

       https://www.gnutls.org/manual/