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On 18/10/2013 16:05, Tanstaafl wrote: |
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> On 2013-10-18 7:19 AM, Alan McKinnon <alan.mckinnon@×××××.com> wrote: |
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>> On 18/10/2013 12:23, Tanstaafl wrote: |
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>>> On 2013-10-17 10:30 PM, Walter Dnes <waltdnes@××××××××.org> wrote: |
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>>>> I apologize. That is arguably a two factor system. When you said |
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>>>> "ssh key and password", I "jumped to delusions", assuming that it was a |
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>>>> standard ssh connection with the option of either key or password. |
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>>> |
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>>> Side question... |
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>>> |
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>>> So, wouldn't the simplest two-factor authentication be an SSH key that |
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>>> required a password? |
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> |
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>> No, there is no way to verify that a user has enabled a passphrase on an |
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>> ssh key. |
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> |
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> No... I mean... |
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> |
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> If I create an SSH key that requires a password (ie, not a 'blank' |
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> password), then when I use this ssh key to connect to the system it was |
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> created for, and it asks for the password... |
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> |
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> This is, as far as I can see, a poor man's 'two-factor' authentication, |
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> is it not? |
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> |
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I think you are misunderstanding how ssh keys work. |
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You do not create "an SSH key that requires a password", instead the |
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user sets up private key encryption locally with a secret. To use the |
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key it must be unlocked (decrypted) and only then can ssh use it. This |
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is completely under the USER's control, who is free to protect or not |
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protect the private key as they feel like. sshd on the server is unable |
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to enforce or influence this in any way. |
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Secondly, the statement "use this ssh key to connect to the system it |
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was created for" is nonsensical. A key pair has two components - public |
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and private keys, and the only thing sshd cares about is whether the |
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user connecting has the matching private key to the public one sshd can |
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read locally. The user is free to use that public key on as many or as |
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few servers as he feels like, and again sshd is in no position to |
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enforce or influence this. It is completely up to the user what he does |
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with his keys. |
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Perhaps you mean that on the server end the user's account has a |
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password defined and sshd is configured to use PAM. The PAM config could |
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require that the user authenticates successfully with ssh keys AND with |
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the Unix password before logging the user in. This can be done, but it |
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is not a common configuration and does not ship out the box. It will |
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also confuse the living daylights out of the average user who at least |
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in my world is unable to differentiate between a local ssh prompt for a |
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key passphrase, and a remote telnet prompt for a password... |
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-- |
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Alan McKinnon |
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alan.mckinnon@×××××.com |
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