Mehmet Erol Sanliturk
m.e.sanliturk at gmail.com
Sun Mar 24 04:51:54 UTC 2013
On Sat, Mar 23, 2013 at 9:22 PM, Doug Hardie <bc979 at lafn.org> wrote:
> I am not sure this is the best place to ask this, but I didn't see any
> other maillists that seemed more appropriate.
> Basically, my outgoing mail server is being systematically attacked to try
> passwords looking for one that works. When they do find one, we get
> inundated by spam sent through that account throughout the world. The
> situation is such that most of our users are older and their computer is a
> hand-me-down so they can talk to their grandchildren. Passwords are a
> great inconvenience for them and create numerous problems with remembering
> them even when they are simple. Unfortunately, most of them are quite easy
> to guess.
> Telling users to use more appropriate passwords is a complete waste of my
> time. Its never going to make any changes as they probably would not
> remember any other password (or where they wrote down the password). This
> situation requires a technical solution.
> I have been investigating the use of client authentication through SSL.
> DoD uses this approach by having the certificates on an ID card and a card
> reader on each computer. We don't have the money to use that approach no
> could we every get our users to spring for that. I was hoping to figure
> out a way to put the certificate on a flash drive or CD that the user would
> carry. The approach we use has to also work for iPads, smart phones etc
> that do not have an interface for a card reader.
> At this time, I have successfully configured a test for openssl client
> authentication using a client certificate. There are a few issues
> remaining. DoD uses a p12 format for their certificates. Many browsers
> support that format. It encrypts the certificate and private key so they
> are not easily obtained from the smart card. Openssl's s_client uses pem
> certificates and the key has to be included in the certificate file. While
> that is easily transported on CD or flash drive, the private key is in the
> clear on the device. Thats not really viable.
> S_client works properly without a certificate when the certificate check
> in the server is set to not fail if a certificate is not provided. This is
> needed because we will never get all our users to use this approach at
> home. They will still want to use passwords. Since the certificate
> request is made before the connection information is available, there is no
> easy way to request it only when needed. I have only been able to test
> with the Safari browser and it does not handle the no certificate case
> properly. I believe it is dropping the connection when the user does not
> select a certificate. I still have to test the other browsers.
> There is an interesting aspect of openssl that the certificate it uses for
> normal SSL authentication is not used for client authentication. There are
> another completely different set of calls that have to be made to set the
> certificate/key for use in validating the client certificates. Much of
> this is only documented in existing code.
> With Safari you have to import the client's certificate into the keychain.
> Then it works fine. Unfortunately, it doesn't go away when you are done
> with it. Unlike the smart card which, when removed, removes the
> certificate, the Safari certificate can continue to be used by anyone
> afterwards. Hence, its not all that useful for authentication. One
> approach I have heard about, but not investigated yet is to place the
> keychain on the removable device. That would make it go away. However,
> that approach would not work with any other browser or mail program.
> Any ideas/suggestions on this will be appreciated. Thanks,
> -- Doug
Using Static IP in the client side , and checking Static IP of the user may
be a possibility :
In that way , any message from another IP will not be accepted .
If this is possible for your systems , it may be checked for usability .
One difficulty is that each user should obtain a Static IP and can not
connect to his/her ISP from another IP .
Good side is that nobody can connect to ISP of the user from another IP :
It supplies hardware security ( we are assuming that the user computer is
not captured ) ..
Thank you very much .
Mehmet Erol Sanliturk
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