crypt function mode

[Thorsten Kukuk]

On Wed, Apr 22, Sudarshan Soma wrote:

> On Wed, Apr 22, 2009 at 2:48 AM, Martin <inkubus at interalpha.co.uk> wrote:
> > On Sun, 2009-04-19 at 12:00 -0400, pam-list-request at redhat.com wrote:
> >> >> Hi All,
> >> >> Can anyone please let me know what block ciphers mode( Electronic
> >> >> Codebook Mode (ECB) , Cipher Blockchaining Mode (CBC),..)
> >> >>  does the crypt function used in pam_unix use.
> >> > It doesn't.  These are for symmetric encryption, the crypt function
> >> uses
> >> > them as a one way hash (that why the later versions use MD5).
> >> >
> >> [Pavan] Thanks Martin. I was bit confused when it says that crypt uses
> >> modified form of DES algorithm
> >> (http://en.wikipedia.org/wiki/Crypt_(Unix)#Modifications_of_the_traditional_scheme).
> >>
> >> So these cipher modes are not applicable for storing/verifying
> >> passwords using crypt.
> > No - they are a tool for a different job.
> >
> >>  My requirement is to make  passwds more secure.
> > More secure against what?  Security is not a linear variable.  The
> > storage format of the password hashes is almost certainly not the
> > weakest link in the chain.
> >
> >> I think enabling shadow passwds(using pwconv) and MD5 hashes
> >> (etc/sysconfig/authconfig) would be enough as the first step.
> > Shadow passwords and using the MD5 based version of crypt are both good
> > ideas and an improvement - whether they will be enough rather depends on
> > your security policy.
> >
> [Pavan] I consider this change as my first step. I have to enable
> symmetrically encrypted passwords (which can be decrypted and use for
> other purposes) which are used on all the interfaces (telnet, ssh,
> ftp,..) for authentication.
> I am trying to figure out, if this can be achieved easily using
> pam_unix module. I will investigate this further and let you know my
> findings.

Code for symmetrically encrypted passwords don't exist, you have to 
implement something at your own.

You need to look at the system crypt() function for this.

  Thorsten

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Thorsten Kukuk, Project Manager/Release Manager SLES
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