Firewall blocking desktop features

Daniel J Walsh dwalsh at
Wed Sep 11 13:05:45 UTC 2013

Hash: SHA1

On 09/11/2013 08:56 AM, Alec Leamas wrote:
> On 2013-09-11 14:46, Daniel J Walsh wrote:
>> On 09/11/2013 06:35 AM, Heiko Adams wrote:
>>> Am 11.09.2013 12:30, schrieb Alec Leamas:
>>>> That said, I see your point.  Seems to boil down to that only the 
>>>> application knows which port(s)  to open and why, whereas only the 
>>>> firewall can guarantee  that it actually opens the ports requested
>>>> by user instead of something else.
>>> So the application needs to ask the firewall to open one or more ports
>>> and the firewall has to ask the user for permission to do so. In this
>>> szenario the firewall knows what application wants which port(s) to be
>>> open. Letting the application directly ask for permission to punch
>>> holes in the firewall is IMHO the worst case of all and a securiry
>>> nightmare.
>> Asking my wife if she intends to open port 2345 is a waste of time.  She
>> has no idea whether or not this is required.  And will quickly learn to
>> answer ok.
>> Asking her "Do you want to make security changes to share directory 
>> /home/phyllis/Share?"  Or
>> Do you want to make security changes to share Printer XYZ?
>> Would make sense.
>> If we had applications register prompts/ports in the installed package
>> that firewalld could look up and send the prompt to the user would be the
>> best solution to this problem.
>> This of course does not stop firefox plugin from attempting to share a 
>> directory, but my wife would have more of a chance to say no.
> Although this would work for both our wifes I'd hate it myself. There need
> to be some way in  the interface to understand what's *really* going on
> here, the ports opened, triggers etc. But not unless requested, agreed.

My idea is that Samba registers something with firewalld that says here is the
prompt to show if a process in user space says to open port 2345.

Or cups registers the ports that would be required to share a printer. And the
prompt.  The apps on the desktop would have limited control over these prompts
other them maybe a couple of args the could pass in.

The problem with this solution is potential conflicts in port numbers and pps
that just use random ports (Which I think should just not be allowed to use
the service and would require to disable the firewall.)

Bottom line we need to give feed back to the user about the action being
requested that makes sense.  I might understand I am sharing a printer or a
directory containing music, what network ports these apps require, I would
have no clue.
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