Dear list,

I was thinking of writing a daemon in freepascal. When the program is started it will ask for a password. Then keep the pass in a string variable, using it every 10 minutes.

It's not for an high security environment but I'm interested in general. How to protect those information in memory?

Johannes

Under Linux or BSD, only the owner can access the memory of his program. So if launched by root, only readable by root.
If possible, store a hash and not a clear password, just to be paranoid as we should :o)
Ex :

var
  salt : string;
  pwd : string;
begin
  salt := 'Something random or my software name, just used to avoid
dictionary attacks';
  pwd := md5('My Secret Password' + salt);
end;

So only a hash is stored in pwd, and it's unique.
But always remember that local access to a computer = quit easy to hack anything, unless you use strong cryptography.

Just keep the password encrypted in memory, and decrypt it before you use it.
You can use the XOrEncode and XOrDecode functions for this. They are in the strutils unit.

Michael.

Marc PERTRON wrote

dictionary attacks'; pwd := md5('My Secret Password' + salt); end;

And where do you think the phrase 'My Secret Password' would be stored other than memory?

Vinzent.

And where do you think the phrase 'My Secret Password' would be stored other than memory?

so you have to override variables after use? like

var pwd: array[0..15] of char;
     xpwd: string;

[...]

readln(pwd);
xpwd := encrypt(pwd);
pwd := '123456789012345'; // override

[...]

???

Yes, and obviously don't declare it within the
program (that's what appeared in the original
example from Marc Pertron) - your example is
indeed better from this point of view. I'd add
that the disadvantage of ReadLn (used by you) is
that it shows typed characters on console and in
addition, I believe that these characters might
be temporarily stored in a buffer in memory too
(before they get overwritten with following
input).

Tomas

Of course my example or the ReadLn are because we don't know your program and where the password comes from.
It appears obvious that you should not write the password in clear text in the software if you want it not to be read from memory ! It was an example for hashing password which are one of the best solution but need a salt to avoid dictionary attacks. Marc