On Oct 16, 2013, at 12:30 PM, Stephen Kent <[email protected]> wrote: >> Finally, we must consider passive wiretapping an active attack. The only >> thing which prevents a passive wiretap from modifying (rather than just >> monitoring) traffic is almost invariably the will of the attacker, not any >> technical limitation, since even on-path wiretappers can packet inject, >> allowing the attacker to trivially promote themselves into a MitM situation >> in almost all circumstances. > I don't agree that we should ignore the differences between passive and > active wiretapping. > I do agree that passive wiretapping can be augment with active attacks of > various sorts. > It's not just the "will" of the attacker that matters; it's also the > capabilities of the > attacker and their sensitivity to being detected.
Capability wise, there is nothing except cryptographic data integrity that prevents an eavesdropper from injecting their own traffic. On HTTP, this enables redirecting the browser to an arbitrary site (for exploitation), extracting any not-SSL-only cookies, injecting arbitrary code at the end of a web page, etc. Absent DNSSEC validation on the part of the victim, DNS injection allows the attacker to MITM any connection. Similarly, at layer 2, absent significant protection in the switch, properly configured, both DHCP and ARP injection allows similar total hijacking. There are no capability limitations of note for a "passive" eavesdropper who wants to become active. Thus it really is "will" as convenient shorthand: is the attacker willing to use this and chance getting caught if a subtle detector is actually looking for the signs of attack? We need universal protection against active adversaries, because the precedents have been set and the distinction between passive and active really is the willingness of the adversary to include active techniques. We need end-to-end data integrity on all communication and if you have end-to-end integrity, anything point-to-point rather than broadcast should also include confidentiality since you can just about get it for free by this point. -- Nicholas Weaver it is a tale, told by an idiot, [email protected] full of sound and fury, 510-666-2903 .signifying nothing PGP: http://www1.icsi.berkeley.edu/~nweaver/data/nweaver_pub.asc
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