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Check destination of DNS UDP query replies.

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At any time, dnsmasq will have a set of sockets open, bound to
random ports, on which it sends queries to upstream nameservers.
This patch fixes the existing problem that a reply for ANY in-flight
query would be accepted via ANY open port, which increases the
chances of an attacker flooding answers "in the blind" in an
attempt to poison the DNS cache. CERT VU#434904 refers.
This commit is contained in:
Simon Kelley
2020-11-12 18:49:23 +00:00
parent 4e96a4be68
commit 257ac0c5f7
2 changed files with 33 additions and 10 deletions
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@@ -6,8 +6,12 @@ version 2.83
dnsmasq with DNSSEC compiled in and enabled is vulnerable to this,
referenced by CERT VU#434904.
Be sure to only accept UDP DNS query replies at the address
from which the query was originated. This keeps as much entropy
in the {query-ID, random-port} tuple as possible, help defeat
cache poisoning attacks. Refer: CERT VU#434904.
>>>>>>> Fix remote buffer overflow CERT VU#434904
version 2.82
Improve behaviour in the face of network interfaces which come
and go and change index. Thanks to Petr Mensik for the patch.