gnutls_prf_early

Section: gnutls (3)
Updated: 3.7.1
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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 © 2001- 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.