samba - Nov 2008 - Confusing behavior of hosts allow/hosts deny in Samba 3.0.28/3.2.4

I saw some unexpected behavior in the interaction of hosts allow and
hosts deny on Samba 3.0.28. I built Samba 3.2.4 just to be sure it
wasn't something that had been fixed. I saw the same behavior.

I'm not sure if it is a bug or a failure on my part to
understand the documentation or misleading documentation.

If I have a share defined as

[export]
        comment         = exported storage
        path            = /export
        # admin users   = boehm
        hosts allow     = boehm-1
        hosts deny      = boehm-3
        oplocks         = no
        level2 oplocks  = no
        guest ok        = no
        create mask     = 0775
        directory mask  = 0775
        map archive     = no
        writeable       = yes

Then host boehm-1 has access and boehm-3 is denied access. The odd
part is that every other host now has access as well (e.g., boehm-2)

Now, if I had only hosts allow and no hosts deny, only host boehm-1
would have access.

         hosts allow    = boehm-1
         # hosts deny   = boehm-3

The confusing part, to me, was that adding hosts deny for a single
host suddenly opened up the share to every host that wasn't in
hosts deny, regardless as to whether they were in hosts allow.

The man page for smb.conf has an example for both hosts allows and
hosts deny

         Example 4: allow only hosts in NIS netgroup "foonet",
         but deny access from one particular host

         hosts allow = @foonet

         hosts deny = pirate

         Note Note that access still requires suitable user-level
         passwords.

         See testparm(1) for a way of testing your host access to
         see if it does what you expect.

This doesn't mention that every host but pirate will have access, not
just those in @foonet.

I see this as a bug but I wonder if I am missing something.

-- 
Eric M. Boehm                  /"\  ASCII Ribbon Campaign
boehm@nortel.com               \ /  No HTML or RTF in mail
                                X   No proprietary word-processing
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On Tue, Nov 04, 2008 at 10:43:35AM -0500, Eric Boehm
wrote:
> I saw some unexpected behavior in the interaction of hosts allow and
> hosts deny on Samba 3.0.28. I built Samba 3.2.4 just to be sure it
> wasn't something that had been fixed. I saw the same behavior.
> 
> I'm not sure if it is a bug or a failure on my part to
> understand the documentation or misleading documentation.
> 
> If I have a share defined as
> 
> [export]
>         comment         = exported storage
>         path            = /export
>         # admin users   = boehm
>         hosts allow     = boehm-1
>         hosts deny      = boehm-3
>         oplocks         = no
>         level2 oplocks  = no
>         guest ok        = no
>         create mask     = 0775
>         directory mask  = 0775
>         map archive     = no
>         writeable       = yes
> 
> Then host boehm-1 has access and boehm-3 is denied access. The odd
> part is that every other host now has access as well (e.g., boehm-2)
> 
> Now, if I had only hosts allow and no hosts deny, only host boehm-1
> would have access.
> 
>          hosts allow    = boehm-1
>          # hosts deny   = boehm-3
> 
> The confusing part, to me, was that adding hosts deny for a single
> host suddenly opened up the share to every host that wasn't in
> hosts deny, regardless as to whether they were in hosts allow.
> 
> The man page for smb.conf has an example for both hosts allows and
> hosts deny
> 
>          Example 4: allow only hosts in NIS netgroup "foonet",
>          but deny access from one particular host
> 
>          hosts allow = @foonet
> 
>          hosts deny = pirate
> 
>          Note Note that access still requires suitable user-level
>          passwords.
> 
>          See testparm(1) for a way of testing your host access to
>          see if it does what you expect.
> 
> This doesn't mention that every host but pirate will have access, not
> just those in @foonet.
> 
> I see this as a bug but I wonder if I am missing something.
I agree it's counter intuitive, but it does match the man
pages for hosts.allow and hosts.deny, which the original
code was based on.
>From those man pages :
-----------------------------------------------------------
ACCESS CONTROL FILES
       The access control software consults two files. The search stops at the
first match:

       ?      Access  will  be  granted  when  a  (daemon,client)  pair  matches
an  entry  in  the
              /etc/hosts.allow file.

       ?      Otherwise, access will be denied when a (daemon,client) pair
matches an entry  in  the
              /etc/hosts.deny file.

       ?      Otherwise, access will be granted.

       A  non-existing access control file is treated as if it were an empty
file. Thus, access con?
       trol can be turned off by providing no access control files.
-----------------------------------------------------------

So having a "hosts allow" but no "hosts deny" means the
"hosts deny"
is treated as an empty file (default deny I think). Once you define
a "hosts deny" then the default changes to "allow", if you
only want
to restrict access to a specific hosts list then don't define a
"hosts deny", just a "hosts allow". I guess the issue is you
really don't need to have both defined (maybe we should log
a warning in this case that the results may not be what you
would expect).

Jeremy.