This patch resolves the problem reported in:
https://bugzilla.redhat.com/show_bug.cgi?id=886663
The source of the problem was the fix for CVE 2011-3411:
https://bugzilla.redhat.com/show_bug.cgi?id=833033
which was originally committed upstream in commit
753ff83a50. That commit improperly
removed the "--except-interface lo" from dnsmasq commandlines when
--bind-dynamic was used (based on comments in the latter bug).
It turns out that the problem reported in the CVE could be eliminated
without removing "--except-interface lo", and removing it actually
caused each instance of dnsmasq to listen on localhost on port 53,
which created a new problem:
If another instance of dnsmasq using "bind-interfaces" (instead of
"bind-dynamic") had already been started (or if another instance
started later used "bind-dynamic"), this wouldn't have any immediately
visible ill effects, but if you tried to start another dnsmasq
instance using "bind-interfaces" *after* starting any libvirt
networks, the new dnsmasq would fail to start, because there was
already another process listening on port 53.
This patch changes the network driver to *always* add
"except-interface=lo" to dnsmasq conf files, regardless of whether we use
bind-dynamic or bind-interfaces. This way no libvirt dnsmasq instances
are listening on localhost (and the CVE is still fixed).
The actual code change is miniscule, but must be propogated through all
of the test files as well.
(This is *not* a cherry-pick of the upstream commit that fixes the bug
(commit d66eb78667), because subsequent
to the CVE fix, another patch changed the network driver to put
dnsmasq options in a conf file rather than directly on the dnsmasq
commandline preserving the same options), so a cherry-pick is just one
very large conflict.)
This bug resolves CVE-2012-3411, which is described in the following
bugzilla report:
https://bugzilla.redhat.com/show_bug.cgi?id=833033
The following report is specifically for libvirt on Fedora:
https://bugzilla.redhat.com/show_bug.cgi?id=874702
In short, a dnsmasq instance run with the intention of listening for
DHCP/DNS requests only on a libvirt virtual network (which is
constructed using a Linux host bridge) would also answer queries sent
from outside the virtualization host.
This patch takes advantage of a new dnsmasq option "--bind-dynamic",
which will cause the listening socket to be setup such that it will
only receive those requests that actually come in via the bridge
interface. In order for this behavior to actually occur, not only must
"--bind-interfaces" be replaced with "--bind-dynamic", but also all
"--listen-address" options must be replaced with a single
"--interface" option. Fully:
--bind-interfaces --except-interface lo --listen-address x.x.x.x ...
(with --listen-address possibly repeated) is replaced with:
--bind-dynamic --interface virbrX
Of course libvirt can't use this new option if the host's dnsmasq
doesn't have it, but we still want libvirt to function (because the
great majority of libvirt installations, which only have mode='nat'
networks using RFC1918 private address ranges (e.g. 192.168.122.0/24),
are immune to this vulnerability from anywhere beyond the local subnet
of the host), so we use the new dnsmasqCaps API to check if dnsmasq
supports the new option and, if not, we use the "old" option style
instead. In order to assure that this permissiveness doesn't lead to a
vulnerable system, we do check for non-private addresses in this case,
and refuse to start the network if both a) we are using the old-style
options, and b) the network has a publicly routable IP
address. Hopefully this will provide the proper balance of not being
disruptive to those not practically affected, and making sure that
those who *are* affected get their dnsmasq upgraded.
(--bind-dynamic was added to dnsmasq in upstream commit
54dd393f3938fc0c19088fbd319b95e37d81a2b0, which was included in
dnsmasq-2.63)
This patch removed the "--filterwin2k" dnsmasq command line
parameter which was unnecessary for domain specification,
possibly blocked some usage, and was command line clutter.
Gene Czarcinski <gene@czarc.net>
dnsmasq is forwarding a number of queries upstream that should not
be done. There still remains an MX query for a plain name with no
domain specified that will be forwarded is dnsmasq has --domain=xxx
--local=/xxx/ specified. This does not happen with no domain name
and --local=// ... not a libvirt problem.
BTW, thanks again to Claudio Bley!
The path to the dnsmasq binary can be configured while in the test data
the path is hard-coded to /usr/bin/. This break the test suite if a the
binary is located in a different location, like /usr/local/sbin/.
Replace the hard coded path in the test data by a token, which is
dynamically replaced in networkxml2argvtest with the configured path
after the test data has been loaded.
(Another option would have been to modify configure.ac to generate the
test data during configure, but I do not know of an easy way do trick
configure into mass-generate those test files without listing every
single one, which I consider less flexible.)
- unit-test the unit-test:
#include <assert.h>
#define TEST(in,token,rep,out) { char *buf = strdup(in); assert(!replaceTokens(&buf, token, rep) && !strcmp(buf, out)); free(buf); }
TEST("", "AA", "B", "");
TEST("A", "AA", "B", "A");
TEST("AA", "AA", "B", "B");
TEST("AAA", "AA", "B", "BA");
TEST("AA", "AA", "BB", "BB");
TEST("AA", "AA", "BBB", "BBB");
TEST("<AA", "AA", "B", "<B");
TEST("<AA", "AA", "BB", "<BB");
TEST("<AA", "AA", "BBB", "<BBB");
TEST("AA>", "AA", "B", "B>");
TEST("AA>", "AA", "BB", "BB>");
TEST("AA>", "AA", "BBB", "BBB>");
TEST("<AA>", "AA", "B", "<B>");
TEST("<AA>", "AA", "BB", "<BB>");
TEST("<AA>", "AA", "BBB", "<BBB>");
TEST("<AA|AA>", "AA", "B", "<B|B>");
TEST("<AA|AA>", "AA", "BB", "<BB|BB>");
TEST("<AA|AA>", "AA", "BBB", "<BBB|BBB>");
TEST("<AAAA>", "AA", "B", "<BB>");
TEST("<AAAA>", "AA", "BB", "<BBBB>");
TEST("<AAAA>", "AA", "BBB", "<BBBBBB>");
TEST("AAAA>", "AA", "B", "BB>");
TEST("AAAA>", "AA", "BB", "BBBB>");
TEST("AAAA>", "AA", "BBB", "BBBBBB>");
TEST("<AAAA", "AA", "B", "<BB");
TEST("<AAAA", "AA", "BB", "<BBBB");
TEST("<AAAA", "AA", "BBB", "<BBBBBB");
alarm(1); /* no infinite loop */
TEST("A", "A", "A", "A");
TEST("AA", "A", "A", "AA");
alarm(0);
Signed-off-by: Philipp Hahn <hahn@univention.de>
If a domain name is defined for a network, add the --expand-hosts
option to the dnsmasq commandline. This results in the domain being
added to any hostname that is defined in a dns <host> element and
contains no '.' characters (i.e. it is an "unqualified"
hostname). Since PTR records are automatically created for any name
defined in <host>, the result of a PTR request will change from the
unqualified name to the qualified name.
This also has the same effect on any hostnames that dnsmasq reads
from the host's /etc/hosts file.
(In the case of guest hostnames that were learned by dnsmasq via DHCP
requests, they were already getting the domain name added on, even
without --expand-hosts).
This commit introduces names definition for the DNS hosts file using
the following syntax:
<dns>
<host ip="192.168.1.1">
<name>alias1</name>
<name>alias2</name>
</host>
</dns>
Some of the improvements and fixes were done by Laine Stump so
I'm putting him into the SOB clause again ;-)
Signed-off-by: Michal Novotny <minovotn@redhat.com>
Signed-off-by: Laine Stump <laine@laine.org>
