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Use random source ports where possible if source addresses/interfaces in use.

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CVE-2021-3448 applies.

It's possible to specify the source address or interface to be
used when contacting upstream nameservers: server=8.8.8.8@1.2.3.4
or server=8.8.8.8@1.2.3.4#66 or server=8.8.8.8@eth0, and all of
these have, until now, used a single socket, bound to a fixed
port. This was originally done to allow an error (non-existent
interface, or non-local address) to be detected at start-up. This
means that any upstream servers specified in such a way don't use
random source ports, and are more susceptible to cache-poisoning
attacks.

We now use random ports where possible, even when the
source is specified, so server=8.8.8.8@1.2.3.4 or
server=8.8.8.8@eth0 will use random source
ports. server=8.8.8.8@1.2.3.4#66 or any use of --query-port will
use the explicitly configured port, and should only be done with
understanding of the security implications.
Note that this change changes non-existing interface, or non-local
source address errors from fatal to run-time. The error will be
logged and communiction with the server not possible.
This commit is contained in:
Simon Kelley
2021-03-15 21:59:51 +00:00
parent 4c30e9602b
commit 74d4fcd756
10 changed files with 345 additions and 273 deletions
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2
src/util.c
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@@ -316,7 +316,7 @@ void *whine_malloc(size_t size)
return ret;
}
int sockaddr_isequal(union mysockaddr *s1, union mysockaddr *s2)
int sockaddr_isequal(const union mysockaddr *s1, const union mysockaddr *s2)
{
if (s1->sa.sa_family == s2->sa.sa_family)
{