MD5 in Oracle (DBMS_OBFUSCATION_TOOLKIT.MD5)

Question

I'm trying to compose a function to obtain MD5 hashes from bits I've gathered here and there. I want to obtain the lower-case hexadecimal representation of the hash. I have this so far:

CREATE OR REPLACE FUNCTION MD5 (
    CADENA IN VARCHAR2
) RETURN DBMS_OBFUSCATION_TOOLKIT.VARCHAR2_CHECKSUM
AS
BEGIN
    RETURN LOWER(
        RAWTOHEX(
            UTL_RAW.CAST_TO_RAW(
                DBMS_OBFUSCATION_TOOLKIT.MD5(INPUT_STRING => CADENA)
            )
        )
    );
END;

I'm not sure about the return type of the function. DBMS_OBFUSCATION_TOOLKIT.VARCHAR2_CHECKSUM looks like the appropriate choice and as far as I can tell it works as expected but the package definition for dbms_obfuscation_toolkit as displayed by SQL Developer shows this:

SUBTYPE varchar2_checksum IS VARCHAR2(16);

The output has 32 characters so I must be doing something wrong. My questions:

• What's the correct type for the RETURN statement?
• Am I doing unnecessary conversions to calculate the hash?

Answer 1

Here you go:

create or replace function getMD5(
  in_string in varchar2)
return varchar2
as
  cln_md5raw raw(2000);
  out_raw raw(16);
begin
  cln_md5raw := utl_raw.cast_to_raw(in_string);
  dbms_obfuscation_toolkit.md5(input=>cln_md5raw,checksum=>out_raw);
  -- return hex version (32 length)
  return rawtohex(out_raw);
end;

The 32 length is because it is a hex representation of the raw(16) value. Or, modify above to output the raw version and store the raw in a RAW column (less space used, but you'll be doing future rawtohex and hextoraw conversions, believe me).

Cheers