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gnutls_prf_early(3) gnutls gnutls_prf_early(3)


gnutls_prf_early - API function


#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);


is a gnutls_session_t type.
length of the label variable.
label used in PRF computation, typically a short string.
length of the extra variable.
optional extra data to seed the PRF with.
size of pre-allocated output buffer to hold the output.
pre-allocated buffer to hold the generated data.


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.


GNUTLS_E_SUCCESS on success, or an error code.




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