Hi,
On 25 Sep 2019, at 20:45, peter.mueller@ipfire.org wrote:
Allowing outgoing DNS traffic (destination port 53, both TCP and UDP) to the root servers is BCP for some reasons. First, RFC 5011 assumes resolvers are able to fetch new trust ancors from the root servers for a certain time period in order to do key rollovers.
Second, Unbound shows some side effects if it cannot do trust anchor signaling (see RFC 8145) or fetch the current trust anchor, resulting in SERVFAILs for arbitrary requests a few minutes.
There is little security implication of allowing DNS traffic to the root servers: An attacker might abuse this for exfiltrating data via DNS queries, but is unable to infiltrate data unless he gains control over at least one root server instance. If there is no firewall ruleset in place which prohibits any other DNS traffic than to chosen DNS servers, this patch will not have security implications at all.
I think we need to document this on the wiki before we merge this patch.
Fixes #12183
Cc: Michael Tremer michael.tremer@ipfire.org Suggested-by: Horace Michael horace.michael@gmx.com Signed-off-by: Peter Müller peter.mueller@ipfire.org
config/rootfiles/core/137/filelists/files | 1 + src/initscripts/system/firewall | 16 ++++++++++++++-- 2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/config/rootfiles/core/137/filelists/files b/config/rootfiles/core/137/filelists/files index ce4e51768..a02840d12 100644 --- a/config/rootfiles/core/137/filelists/files +++ b/config/rootfiles/core/137/filelists/files @@ -1,4 +1,5 @@ etc/system-release etc/issue +etc/rc.d/init.d/firewall srv/web/ipfire/cgi-bin/credits.cgi var/ipfire/langs diff --git a/src/initscripts/system/firewall b/src/initscripts/system/firewall index ec396c708..ff63a2ede 100644 --- a/src/initscripts/system/firewall +++ b/src/initscripts/system/firewall @@ -6,10 +6,11 @@ eval $(/usr/local/bin/readhash /var/ipfire/ppp/settings) eval $(/usr/local/bin/readhash /var/ipfire/ethernet/settings) eval $(/usr/local/bin/readhash /var/ipfire/optionsfw/settings) -IFACE=`/bin/cat /var/ipfire/red/iface 2> /dev/null | /usr/bin/tr -d '\012'` +ROOTHINTS="/etc/unbound/root.hints" +IFACE=$( /bin/cat /var/ipfire/red/iface 2> /dev/null | /usr/bin/tr -d '\012' )
if [ -f /var/ipfire/red/device ]; then
- DEVICE=`/bin/cat /var/ipfire/red/device 2> /dev/null | /usr/bin/tr -d '\012'`
- DEVICE=$( /bin/cat /var/ipfire/red/device 2> /dev/null | /usr/bin/tr -d '\012' )
fi
Why the added whitespace? Should have been an extra patch.
function iptables() { @@ -307,6 +308,17 @@ iptables_init() { iptables -A INPUT -j TOR_INPUT iptables -N TOR_OUTPUT iptables -A OUTPUT -j TOR_OUTPUT
- # Allow outgoing DNS traffic (TCP and UDP) to DNS root servers
- ROOTSERVERIPS="$( awk '/\s+A\s+/ { print $4 }' ${ROOTHINTS} | xargs )"
- ipset -N root-servers iphash
ROOTSERVERIPS could have been an array and could have been local.
You do not need to call xargs. It is a rather expensive way to remove line breaks.
- for ip in ${ROOTSERVERIPS}; do
ipset add root-servers $ip- done
It is also interesting that ipset does not allow to add more IP addresses in one go. This looks like a very expensive loop for a lot of IP addresses. I think this is fine here for about a dozen addresses, but importing a blacklist of thousands or tens of thousands of IP addresses will take a long time.
iptables -A OUTPUT -m set --match-set root-servers dst -p tcp --dport 53 -j ACCEPT
iptables -A OUTPUT -m set --match-set root-servers dst -p udp --dport 53 -j ACCEPT
# Jump into the actual firewall ruleset. iptables -N INPUTFW
-- 2.16.4
-Michael