[Asterisk-Users] Formatting in sip.conf...can you have 2 @ signs for register?

[Greg Hill]

On Mon, 16 Aug 2004, Sean Cheesman wrote:

> It might make sense for * to parse the register line from right to left.
> Then it wouldn't be an issue.  Or am I missing another issue that would
> arise?

That's an interesting idea. It might be tricky, though, because you have
to read the scheme (sip:) off the front of the URI to identify what it is
and what fields it might have. Some fields are optional, too, like the
password and port. It would take some careful handling, but I suppose it
could be done.

As an aside, many MTAs will simply drop a message when they find that a
to/from header has an address with multiple @'s. They consider it to be an
attempted attack (by the sender) trying to break some security. For
example, if I were to send mail to victim at realtarget@unfortunaterelay.com
and the MTA at unfortunaterelay.com allowed the message through, then some
other tool in the chain might see this as a message to victim at realtarget
and re-send the message there. The supposed-closed relay would effectively
be an open relay, with all the implications that go with that.

Greg



> -----Original Message-----
> From: asterisk-users-admin at lists.digium.com
> [mailto:asterisk-users-admin at lists.digium.com] On Behalf Of Greg Hill
> Sent: Monday, August 16, 2004 1:21 PM
> To: asterisk-users at lists.digium.com
> Subject: Re: [Asterisk-Users] Formatting in sip.conf...can you have 2 @
> signs for register?
>
>
> On Mon, 16 Aug 2004, Olle E. Johansson wrote:
>
> > James Freire wrote:
> >
> > > Hi All,
> > > I am trying to setup another sip trunk in addition to what I am
> > > already using.  The sip provider we are using right now gives you
> > > your username as your email address. So IE. If my email is
> > > james at james.com.... that is my username . Now... When I put this in
> > > the sip.conf file I have found that Asterisk is not able to parse it
> > > correctly and instantly goes to the email server to authenticate the
> > > sip user upon registration
> > >
> > > Here is the line below in my sip.conf file
> > >
> > > register => username at theiremailhost.com:password at sipprovider.com
> > >
> > > THe error is below
> > >
> > > Aug 16 11:30:05 NOTICE[114695]: chan_sip.c:3922 sip_reg_timeout:
> > > Registration for 'john at useremail.com@sip.voipamericas.com' timed
> > > out, trying again Aug 16 11:30:06 NOTICE[114695]: chan_sip.c:6575
> > > handle_response: Failed to authenticate on REGISTER to
> > > '<sip:john at useremail.com>;tag=as1c528b93'
> > >
> >
> > That's obviously an error. Please add it to the bug tracker and we'll
> > solve it.
>
>
> I disagree.. although the sip rfc (I'm looking at 3261, June 2002)
> doesn't specifically state that the user field cannot have the @
> character in it, the language there suggests that '@' is supposed to be
> the separator between the user string and the host string. In addition,
> it is stated that the sip URI scheme follows RFC 2396, which states that
> all of [;/?:@&=+$,] are reserved characters. See section 2.2:
>    The "reserved" syntax class above refers to those characters that are
>    allowed within a URI, but which may not be allowed within a
>    particular component of the generic URI syntax; they are used as
>    delimiters of the components described in Section 3.
>
> I think Asterisk's behavior is correct and the syntax
> 'john at useremail.com@sip.voipamericas.com' is debateable at best. It's
> possible that replacing the @ in the intended user portion with %40 may
> allow it to slip through Asterisk and get un-escaped by the server on
> the far end.. Anyway, the issue may warrant some more dialogue before
> declaring it a defect.
>
> Greg
>