Messages in this thread | | | Subject | Re: predictable IP ID | Date | Mon, 4 Oct 1999 14:26:31 +0100 (BST) | From | Alan Cox <> |
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> Predictable IP IDs is not just a question about losing packets because > attackers can create junk fragments.
Oh not this one again.
The checksum of the tcp header or UDP header covers the entire packet after reassembly. That means that feeding in a corrupt fragment causes a checksum failure and packet discard.
The original TCP authors had that one covered. IP sequence space is shorter than max ttl so all protocols need to be robust against suprise fragment delivery.
> There are other possible attacks. For example predictable IP IDs can be used > to completely bypass TCP connection security based on unpredictable TCP sequence
> numbers. Tools exploiting this weakness already exist. See > http://www.securityfocus.com/templates/archive.pike?list=1&date=1999-08-1&msg=BUGTRAQ%251999080211573830@LISTS.SECURITYFOCUS.COM >
This URL has nothing to do with IP sequence guessing. It references some old unrelated 2.0.3x thing.
Alan
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