gnutls_prf_early(3)                 gnutls                 gnutls_prf_early(3)

NAME
       gnutls_prf_early - API function

SYNOPSIS
       #include <gnutls/gnutls.h>

       int gnutls_prf_early(gnutls_session_t session, size_t label_size, const
       char * label, size_t context_size, const char * context, 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.

       size_t context_size
                   length of the  extra variable.

       const char * context
                   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
       This function is similar to gnutls_prf_rfc5705(), but only works in TLS
       1.3 or later to export early keying material.

       Note that the keying material is only available after the ClientHello
       message is processed and before the application traffic keys are
       established.  Therefore this function shall be called in a handshake
       hook function for GNUTLS_HANDSHAKE_CLIENT_HELLO.

       The  label variable usually contains a string denoting the purpose for
       the generated data.

       The  context 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 that, to provide the RFC5705 context, the  context variable must
       be non-null.

RETURNS
       GNUTLS_E_SUCCESS on success, or an error code.

SINCE
       3.6.8

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


COPYRIGHT
       Copyright (C) 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/

gnutls                               3.8.8                 gnutls_prf_early(3)