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SSL_CTX_use_psk_identity_hint(3)    OpenSSL   SSL_CTX_use_psk_identity_hint(3)

       SSL_CTX_use_psk_identity_hint, SSL_use_psk_identity_hint,
       SSL_CTX_set_psk_server_callback, SSL_set_psk_server_callback - set PSK
       identity hint to use

	#include <openssl/ssl.h>

	int SSL_CTX_use_psk_identity_hint(SSL_CTX *ctx, const char *hint);
	int SSL_use_psk_identity_hint(SSL *ssl, const char *hint);

	void SSL_CTX_set_psk_server_callback(SSL_CTX *ctx,
	       unsigned int (*callback)(SSL *ssl, const char *identity,
	       unsigned char *psk, int max_psk_len));
	void SSL_set_psk_server_callback(SSL *ssl,
	       unsigned int (*callback)(SSL *ssl, const char *identity,
	       unsigned char *psk, int max_psk_len));

       SSL_CTX_use_psk_identity_hint() sets the given NULL-terminated PSK
       identity hint hint to SSL context object ctx.
       SSL_use_psk_identity_hint() sets the given NULL-terminated PSK identity
       hint hint to SSL connection object ssl. If hint is NULL the current
       hint from ctx or ssl is deleted.

       In the case where PSK identity hint is NULL, the server does not send
       the ServerKeyExchange message to the client.

       A server application must provide a callback function which is called
       when the server receives the ClientKeyExchange message from the client.
       The purpose of the callback function is to validate the received PSK
       identity and to fetch the pre-shared key used during the connection
       setup phase. The callback is set using functions
       SSL_CTX_set_psk_server_callback() or SSL_set_psk_server_callback(). The
       callback function is given the connection in parameter ssl,
       NULL-terminated PSK identity sent by the client in parameter identity,
       and a buffer psk of length max_psk_len bytes where the pre-shared key
       is to be stored.

       SSL_CTX_use_psk_identity_hint() and SSL_use_psk_identity_hint() return
       1 on success, 0 otherwise.

       Return values from the server callback are interpreted as follows:

       0   PSK identity was not found. An "unknown_psk_identity" alert message
	   will be sent and the connection setup fails.

       >0  PSK identity was found and the server callback has provided the PSK
	   successfully in parameter psk. Return value is the length of psk in
	   bytes. It is an error to return a value greater than max_psk_len.

	   If the PSK identity was not found but the callback instructs the
	   protocol to continue anyway, the callback must provide some random
	   data to psk and return the length of the random data, so the
	   connection will fail with decryption_error before it will be
	   finished completely.

1.0.2k				  2017-01-26  SSL_CTX_use_psk_identity_hint(3)