.\" DO NOT MODIFY THIS FILE!  It was generated by gdoc.

.TH "gnutls_prf_early" 3 "3.6.14" "gnutls" "gnutls"

.SH NAME

gnutls_prf_early \- API function

.SH SYNOPSIS

.B #include <gnutls/gnutls.h>

.sp

.BI "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 ");"

.SH ARGUMENTS

.IP "gnutls_session_t session" 12

is a \fBgnutls_session_t\fP type.

.IP "size_t label_size" 12

length of the  \fIlabel\fP variable.

.IP "const char * label" 12

label used in PRF computation, typically a short string.

.IP "size_t context_size" 12

length of the  \fIextra\fP variable.

.IP "const char * context" 12

optional extra data to seed the PRF with.

.IP "size_t outsize" 12

size of pre\-allocated output buffer to hold the output.

.IP "char * out" 12

pre\-allocated buffer to hold the generated data.

.SH "DESCRIPTION"

This function is similar to \fBgnutls_prf_rfc5705()\fP, 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 \fBGNUTLS_HANDSHAKE_CLIENT_HELLO\fP.

The  \fIlabel\fP variable usually contains a string denoting the purpose

for the generated data.

The  \fIcontext\fP 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  \fIout\fP , which must be pre\-allocated.

Note that, to provide the RFC5705 context, the  \fIcontext\fP variable

must be non\-null.

.SH "RETURNS"

\fBGNUTLS_E_SUCCESS\fP on success, or an error code.

.SH "SINCE"

3.6.8

.SH "REPORTING BUGS"

Report bugs to <bugs@gnutls.org>.

.br

Home page: https://www.gnutls.org

.SH COPYRIGHT

Copyright \(co 2001- Free Software Foundation, Inc., and others.

.br

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.

.SH "SEE ALSO"

The full documentation for

.B gnutls

is maintained as a Texinfo manual.

If the /usr/share/doc/gnutls/

directory does not contain the HTML form visit

.B

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

.PP