Sylvain Beucler <[EMAIL PROTECTED]> tapota :

> On Sun, Jan 02, 2005 at 04:01:51PM +0100, Mathieu Roy wrote:
>> Sylvain Beucler <[EMAIL PROTECTED]> tapota :
>> 
>> > On Sun, Jan 02, 2005 at 03:15:44PM +0100, Mathieu Roy wrote:
>> >> Commit from yeupou on branch DEV_2004-12-28_Savannah (2005-01-02 15:15 
>> >> CET)
>> >> ----------------------------------------------------
>> >> 
>> >> Comment out a test being made on the ssh key type: I'm not sure we can do 
>> >> these test here.
>> >>        # An ssh server can be configured to accept only specific 
>> >> protocols.
>> >>        # Having Savane doing this kind of override looks way too 
>> >> site-specific.
>> >> '
>> >> 
>> >>   savane  lib/Savannah/User.pm  1.31.2.6
>> >
>> > From man sshd:
>> >      AUTHORIZED_KEYS FILE FORMAT
>> >
>> >      [...]
>> >
>> >      Each line of the file contains one key (empty lines and lines
>> >      starting with a `#' are ignored as comments).  Each RSA public
>> >      key consists of the following fields, separated by spaces:
>> >      options, bits, exponent, modulus, comment.  Each protocol version
>> >      2 public key consists of: options, key� type, base64 encoded key,
>> >      comment.  The options fields are optional; its presence is
>> >      determined by whether the line starts with a number or not (the
>> >      option field never starts with a number).  The bits, exponent,
>> >      modu� lus and comment fields give the RSA key for protocol
>> >      version 1; the com� ment field is not used for anything (but may
>> >      be convenient for the user to identify the key).  For protocol
>> >      version 2 the keytype is ``ssh-dss'' or ``ssh-rsa''.
>> >
>> > This is a test to test the validity of the key, so that user cannot
>> > put invalid stuff in ~/authorized_keys.
>> >
>> > It was setup by the FSF sysadmins.
>> >
>> > I wonder, do you think one could add "command=/bin/bash " in his key
>> > in a site that doesn't use an authorized_keys prefix (ie Gna!)?
>> 
>> One could do that. And he would get exactly what he would get if he
>> simply runs
>>        ssh [EMAIL PROTECTED]
>> 
>> This command= option allows to force someone to use a specific command
>> whenever he use ssh. But it does not allow him to use this specific
>> command in a way is not able to generally. 
>> 
>> 
>> > Is the problem, the fact you want to support SSH Protocol v1?
>> 
>> I do not think we support ssh protocol v1. But I would not like
>> someone installing Savane not being able out of the box to get
>> sv_users working because he's not user ssh protocol v2, to name a
>> case.
>> 
>> The problem with checking whether a key is valid or not it that it
>> forces us to reimplement what is already part of SSH. Fortunately, one
>> should be able to get ssh not being fooled easily with malicious
>> content in the authorized_keys file.
>> 
>> I'm not sure the best way to secure a system is to control strictly
>> content of what is, in the end, a user file (it is in ~/, not
>> /etc/passwd). I'm not saying that's dumb but I think that a file which
>> is by design under user control should not be where control is being
>> made. Sure we can add extra control everywhere; but when we do that,
>> we have to think about the problem it involves. And having sv_users
>> not running out of the box with a specific ssh server would be a
>> problem, don't you think?
>
> Ok.
>
> I'll ask Jim why this test was important, and depending on his reply,
> we'll reconsider the issue, including the need for
> $sys_authorized_keys_prefix.
>
> Meanwhile, we need it. I'm also reactivating and debugging the change
> in GetUserSSHKeyReal - else all keys will be rewritten, since it would
> include the prefix.

But make sure it does not alter the content of others keys (in some
cases, it was remove the first character of the key).



-- 
Mathieu Roy

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