[avahi] Avahi daemon dies on certain hostnames

[Marc Krochmal]

On Mar 31, 2006, at 3:50 PM, Lennart Poettering wrote:

> On Tue, 21.03.06 17:31, Iván Sánchez Ortega (i.sanchez at mirame.net)  
> wrote:
>
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> Hi,
>>
>> I just discovered that the Avahi daemon dies if one machine in the  
>> network
>> handles out a response with a strange host (or domain) name.
>>
>> I'm attaching the ethereal capture of the packet that "kills" the  
>> avahi
>> daemon, but this is how I can reproduce this:
>>
>> - - Buy an Axis IP camera
>> - - Change the camera hostname by issuing the following command:
>> wget
>> http://{camera_ip_address}/axis-cgi/admin/param.cgi? 
>> action=update&Network.Bonjour.FriendlyName=fóobar
>> (notice the acute in the 'ó')
>> - - Run avahi-browse -at
>> - - Watch how the avahi daemon dies.
>>
>> I guess that setting up any other kind of mDNS responder (an avahi  
>> daemon, a
>> Bonjour-enabled Mac, etc) to return a hostname with "strange"  
>> characters
>> (anything not in 7-bit ASCII, I guess, like in "fóobar") may be  
>> able to
>> reproduce this bug. By the way, I'm running Avahi 0.6.9 here.
>
>
> Hmm. While Avahi shouldn't die when such a host name appears on the
> network it's primarily a bug in the axis cameras. They shouldn't send
> hostnames with invalid UTF-8 characters in the first place. However, I
> don't know what to do in such a case. Ignore the hostanem entirely
> because it isn't valid UTF-8? Treat is as ISO8859-1 if it doesn't
> validate as UTF8?
>
> I think i will simply write a message to syslog and ignore the RRs
> which contains such bogus host names. What do you think?

Couldn't you just allow the UTF-8 hostname but log a warning  
message?  UTF-8 is a valid encoding scheme for mDNS in general, just  
in practice, hostnames are traditionally restricted to letter,  
digits, hyphens so as to make them easy to type into command-line  
interfaces.

-Marc