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Re: SSHA as default password-hash in next password change
Hi Andrew and Michael,
Thanks so much for your clarification....I really appreciate them.
We are already using overlay and it is working perfectly.
Your point about MD5 is great!...but we have some requirements and the
idea is use SSHA-512 for our password.
I read some post from Michael talking about this problem and I know that
there is a contrib module for SSHA-512.
Any suggestions about this problem are welcome!..
Thanks in advance,
On 06/04/2013 04:58 AM, Andrew Findlay wrote:
> On Mon, Jun 03, 2013 at 03:54:38PM -0500, cbulist@gmail.com wrote:
>
>> We are not using any client..we are just changing the user password from
>> ssh console.
> If you use the passwd command, the LDAP operation used to make the change
> will depend on your PAM LDAP implementation. It might be the Password
> Modify extended operation (good) or it might be an ordinary LDAP Modify
> operation (less good).
>
>> We imported our /etc/passwd to openldap and our idea is when the user
>> gets the next expiration time the new password be in SSHA.
>> Is it possible?....
> To catch both cases above you will need to add an overlay to your slapd
> config. First set the desired hash in the global section:
>
> password-hash {SSHA}
>
> Then add an overlay on top of the main database section:
>
> overlay ppolicy
> ppolicy_default "cn=Password Policy,dc=dir,dc=example,dc=org"
> ppolicy_hash_cleartext
>
> You should also create the password policy entry, something like this:
>
> # Default password policy
> # Applies to userPassword (2.5.4.35)
> dn: cn=Password Policy,dc=dir,dc=example,dc=org
> objectClass: organizationalRole
> objectClass: pwdPolicy
> cn: Password Policy
> description: The default password policy
> pwdAttribute: 2.5.4.35
> pwdLockout: TRUE
>
> The overall effect will be that passwords that arrive at the LDAP server in
> plain text will be hashed using the SSHA scheme. Any passwords that arrived
> pre-hashed (e.g. by PAM LDAP) will be stored as-is (it is not possible to
> convert from one hash scheme to another).
>
> Why are you changing from MD5 to SSHA? If it is to improve password
> security you may be disappointed, depending on which MD5-based hash you
> currently use. As the passwords came from an /etc/passwd file it is likely
> that they use the $6$ or $2a$ hash schemes. Those are both vastly more
> secure than {SSHA} against brute-force attacks. The known weaknesses in the
> MD5 algorithm are much less significant than the fact that {SSHA} only runs
> the algorithm *once* whereas $6$ and $2a$ are carefully designed to be slow
> to calculate.
>
> For an indication of the relative strengths of various hash schemes, see
> Hashcat: http://hashcat.net/oclhashcat-plus/ (table near the bottom of the
> page).
>
> If all your LDAP servers will run on Linux, Solaris, or similar OS then you
> can stay with $6$ like this:
>
> password-hash {CRYPT}
> password-crypt-salt-format "$6$%.12s"
>
> The result will be about 60,000 times harder to break than SSHA.
>
> Andrew