new function: sqlpage.hmac

[lovasoa]

Initially suggested in #263

[srcarvalho12]

Searching around I found this function for MySQL and MariaDB:

DROP FUNCTION IF EXISTS HMACSHA256;

-- here val is the message generate a HMAC for
DELIMITER //
CREATE FUNCTION HMACSHA256(secret_key VARCHAR(256), val VARCHAR(2048))
  RETURNS CHAR(64) DETERMINISTIC
BEGIN
DECLARE ipad,opad BINARY(64);
DECLARE hexkey CHAR(128);
DECLARE hmac CHAR(64);

SET hexkey = RPAD(HEX(secret_key),128,"0");

IF LENGTH(secret_key) > 64 THEN
   SET hexkey = RPAD(SHA2(secret_key, '256'), 128, "0");
END IF;

SET ipad = UNHEX(CONCAT(
    LPAD(CONV(CONV( MID(hexkey,1  ,16), 16, 10 ) ^ CONV( '3636363636363636', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,17 ,16), 16, 10 ) ^ CONV( '3636363636363636', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,33 ,16), 16, 10 ) ^ CONV( '3636363636363636', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,49 ,16), 16, 10 ) ^ CONV( '3636363636363636', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,65 ,16), 16, 10 ) ^ CONV( '3636363636363636', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,81 ,16), 16, 10 ) ^ CONV( '3636363636363636', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,97 ,16), 16, 10 ) ^ CONV( '3636363636363636', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,113,16), 16, 10 ) ^ CONV( '3636363636363636', 16, 10 ),10,16),16,"0")
));

SET opad = UNHEX(CONCAT(
    LPAD(CONV(CONV( MID(hexkey,1  ,16), 16, 10 ) ^ CONV( '5c5c5c5c5c5c5c5c', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,17 ,16), 16, 10 ) ^ CONV( '5c5c5c5c5c5c5c5c', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,33 ,16), 16, 10 ) ^ CONV( '5c5c5c5c5c5c5c5c', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,49 ,16), 16, 10 ) ^ CONV( '5c5c5c5c5c5c5c5c', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,65 ,16), 16, 10 ) ^ CONV( '5c5c5c5c5c5c5c5c', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,81 ,16), 16, 10 ) ^ CONV( '5c5c5c5c5c5c5c5c', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,97 ,16), 16, 10 ) ^ CONV( '5c5c5c5c5c5c5c5c', 16, 10 ),10,16),16,"0"),
    LPAD(CONV(CONV( MID(hexkey,113,16), 16, 10 ) ^ CONV( '5c5c5c5c5c5c5c5c', 16, 10 ),10,16),16,"0")
));

SET hmac = SHA2(CONCAT(opad,UNHEX(SHA2(CONCAT(ipad,val), '256'))), '256');

RETURN hmac;

END //
DELIMITER ;