@deftypefun {int} {gnutls_prf_raw} (gnutls_session_t @var{session}, size_t @var{label_size}, const char * @var{label}, size_t @var{seed_size}, const char * @var{seed}, size_t @var{outsize}, char * @var{out})

@var{session}: is a @code{gnutls_session_t}  type.

@var{label_size}: length of the  @code{label} variable.

@var{label}: label used in PRF computation, typically a short string.

@var{seed_size}: length of the  @code{seed} variable.

@var{seed}: optional extra data to seed the PRF with.

@var{outsize}: size of pre-allocated output buffer to hold the output.

@var{out}: pre-allocated buffer to hold the generated data.

Apply the TLS Pseudo-Random-Function (PRF) on the master secret

and the provided data.

The  @code{label} variable usually contains a string denoting the purpose

for the generated data.  The  @code{seed} usually contains data such as the

client and server random, perhaps together with some additional

data that is added to guarantee uniqueness of the output for a

particular purpose.

Because the output is not guaranteed to be unique for a particular

session unless  @code{seed} includes the client random and server random

fields (the PRF would output the same data on another connection

resumed from the first one), it is not recommended to use this

function directly.  The @code{gnutls_prf()}  function seeds the PRF with the

client and server random fields directly, and is recommended if you

want to generate pseudo random data unique for each session.

@strong{Note:} This function will only operate under TLS versions prior to 1.3.

In TLS1.3 the use of PRF is replaced with HKDF and the generic

exporters like @code{gnutls_prf_rfc5705()}  should be used instead. Under

TLS1.3 this function returns @code{GNUTLS_E_INVALID_REQUEST} .

@strong{Returns:} @code{GNUTLS_E_SUCCESS}  on success, or an error code.

@end deftypefun