gnutls_prf_early — API function
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);
- 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.
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.
Report bugs to <firstname.lastname@example.org>.
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