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Vonage paul248: Those MD5 hashes are the key. The problem is that they are some sort of
paul248: Those MD5 hashes are the key. The problem is that they are some sort of challenge/response system and we don't know the secrets.
As an example of how this sort of thing typically works, something like this would happen.
Server: Generates a token (random chunk of data, serial number, something)
Client: connects to server, and the server tells the client what the challenge (token) is. WIth things like apop, the challenge is the msgid-like string at login. With ppp-chap it is explicitly passed through. I dont know enough about the sip handshake to say what happens here.
Client: takes token from server, and the secret ("password") which is stored internally in the device. client then hashes the combination of token and client secret. Passes the md5 string to the server.
Server: does the same hash operation on the token and what it expects the client to have as the secret. It then compares the two hash values. If they are the same, then the client has proved its identity.
And that is the hard part. The hash is (essentially) irreversible. We will not know what the challenge token will be in advance, it is different each time the client connects. We don't know the secret (password) stored on the client.
We can see the hash each time, but that doesn't help us at all for figuring out the secret password. And we can't reuse the MD5 hash each time, because the server is (or had better be!) using a new challenge token each time.
Of course, the hash can be brute forced and you can try permutations of all possible secrets, but that takes a lot of horsepower. It might be easier to physically attack the device and download the eeprom contents.
If you want to know how hard the secret will be to crack, you might look at existing softphone account passwords. They probably are generated with the same algorithm so you can see how long they might be, what character sets are used, etc.
The interesting weakness in this simple system is that it is completely vulnerable to a man-in-the-middle attack. You can proxy the tokens and responses and neither end will be aware of the computer in the middle.
Anyway, this is not particularly useful to know because you need to figure out how to get the ATA into handshaking mode in order to abuse it to calculate the responses for you. There are so many problems waiting there that it is probably going to be simpler to physically attack the device.
Of course, this is all well into Terms Of Service violation territory if you're a Vonage customer and you could find yourself in hot water.
Interesting thought.. If you are not a Vonage customer and go to a retail store and buy one of the locked retail kits, you haven't yet agreed to the terms of service that you are normally forced to agree to when you activate an account... There isn't even a shrink-wrap license notice on the outside of the box... And the TOS hardcopy inside the box says that "by activating the service, you agree ....." - so in theory if you're not a subscriber, you can do whatever you'd like with it.
It is just a matter of time before somebody pops open a box, extracts the keys and writes a decent sip client emulator that proxies the connections. Sooner or later, somebody will do it and all hell will break loose.
If I was Vonage, I'd be thinking about heading that off that scenario by removing the incentives. ie: providing what their customers want. The attitude of "This is what we provide and you WILL like it!" is part of the reason why people hate their local telcos and why Vonage gets a foot in the door. Finding the same attitudes at the "alternative" is a big let down. Price isn't everything.
Read The Full Thread: Softphone for Main Unlimited $24.99 Residential Service
• To ask simply and directly as possible, why can't you use Softphone software feature
• If you would like an official explanation from Vonage then you need to speak with
• Thank you very much for your reply..
And what you say could very well be true.
In
• I don't have SoftPhone, but I'd guess it's partly to discourage you from sharing
• I wish they'd figure out something reasonable soon. I'm not buying the 'too many
• That doesn't apply to the issue. The question was, why isn't unlimited use of the
• I'd happily give them their motorola ATA back and pay the shipping if they'd only
• ToddlerTN,
I wish I would have worded the subject the way you just did. Very
• Actually, what is really damn annoying is that Vonage *do* offer multiple line,
• Wow very informative post about the business offerings.
I have taken some
peterwemm posted "paul248: Those MD5 hashes are the key. The problem is that they are some sort of" on 03/17/2005 |
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