Re: storing password in variable

From: foo (foo_at_bar.baz)
Date: 06/07/04 

Date: Mon, 07 Jun 2004 00:04:13 -0700

Atom 'Smasher' wrote:

> using a script to encrypt (using openssl) some files to removable media,
> i'm prompted for a password (twice) each time openssl is invoked.
>
> i'm wondering if it's "safe" for the script to ask me for a password,
> store the password in a variable, and use it each time openssl is invoked
> throughout the script. (i can have the script not echo the password as i'm
> typing it, and ask for it to be typed twice)
>

If someone has read access to '/dev/mem', they can see your password in
plain-text; so this approach isn't advisable.

> in the environment where this is being used, my concern (and curiosity) is
> if the variable (containing the password) might be saved to disk cache
> while the shell script is running.

This can happen if your OS implements virtual memory (e.g., the page that
holds your password is paged-out to disk) or full-fledged process swapping.
I know Linux implements both.

Once again, if someone has read access to the swap partition or page-file,
they can see your password in plain-text.

>
> so i'm wondering how "safe" it is to do that, what else should i be
> concerned with, and how much of this is shell and OS dependant.
>

This is mostly OS dependent, unless of course you store your password in a
global environment variable using 'export' or 'declare -x' in BASH.

> thanks...

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