We spent some time yesterday trying to understand how IAX2 authentication works, and now I'm confused...

Let's say that the receiving end has this entry in their iax.conf file:

[remote-site]
type=user
secret=foo
auth=md5
context=incoming
host=dynamic

The way I see it, there are two ways to initiate an outbound IAX2 connection to this system:

1) Use Dial, as in:

Dial(IAX2/remote-site:[EMAIL PROTECTED]/extension)

In this mode, the IAX2 setup message contains a USERNAME ("remote-site"), and the receiving system compares it to the entity name in iax.conf, before comparing the secret. This is fine.

2) Use Dial and iax.conf, as in:

Dial(IAX2/local-site/extension)

and in remote-site's iax.conf:

[local-site]
type=peer
secret=foo
auth=md5
host=local-site.domain.com

In this mode, the IAX2 setup message _does not_ contain a USERNAME, and the receiving system somehow manages to find the proper entry and authenticate the connection.

However, the only way that I could see that this would be possible is that the receiving system is comparing the supplied "secret" against all secrets in it's iax.conf file to try to find a match. I don't know how that is possible using md5 authentication, but even if it is, I don't particularly like it. That means someone can connect to my Asterisk server over IAX if they can guess _any_ secret that happens to be in my iax.conf file.

I really would prefer to not embed the username/password information in my Dial commands (that way it doesn't have to be duplicated in multiple contexts, and it's more logically stored in iax.conf anyway), but unless I do that Asterisk does not send a USERNAME to the receiving server and thus the authentication is not very secure.

Is there a reason why Asterisk allows incoming IAX2 calls without USERNAME specified at all?
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