Hi, Section 4: > If the resolver was > configured with a weak trust anchor and got nothing after sending a > request with DO bit set, then it should clear DO bit in the EDNS0 in > the query message and query again to the authoritative name server. > So it could receive a normal DNS message (with no DNSSEC information, > if the previous packet loss was caused by large size) and continue > its DNS query process, then return the result as an insecure message.
The concept is vulnerable to downgrade attacks: - An on-path MITM attacker can drop DNSSEC messages to force insecure DNS and then spoof bogus DNS responses. - An off-path attacker can saturate links to delay/drop DNSSEC messages to force insecure DNS and then spoof bogus DNS responses. The interoperability problems can be solved without degrading security, e.g. fall back to TCP. Regards, Matt -- Universität Duisburg-Essen Verteilte Systeme Bismarckstr. 90 / BC 316 47057 Duisburg
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