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Set the default maximum DNS UDP packet size to 1232

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Resolves: CVE-2023-28450
This commit is contained in:
Petr Menšík 2023-04-03 16:23:51 +02:00
parent 8ca7e31dc5
commit f132a4c40b
2 changed files with 52 additions and 1 deletions
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45
dnsmasq-2.89-edns0-size.patch Normal file
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@ -0,0 +1,45 @@
From 9d8270be2e2b31437684f2d87add9a28a41f0c75 Mon Sep 17 00:00:00 2001
From: Simon Kelley <simon@thekelleys.org.uk>
Date: Tue, 7 Mar 2023 22:07:46 +0000
Subject: [PATCH] Set the default maximum DNS UDP packet size to 1232.
http://www.dnsflagday.net/2020/ refers.
Thanks to Xiang Li for the prompt.
(cherry picked from commit eb92fb32b746f2104b0f370b5b295bb8dd4bd5e5)
---
man/dnsmasq.8 | 3 ++-
src/config.h | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/man/dnsmasq.8 b/man/dnsmasq.8
index fce580f..4b0b180 100644
--- a/man/dnsmasq.8
+++ b/man/dnsmasq.8
@@ -171,7 +171,8 @@ to zero completely disables DNS function, leaving only DHCP and/or TFTP.
.TP
.B \-P, --edns-packet-max=<size>
Specify the largest EDNS.0 UDP packet which is supported by the DNS
-forwarder. Defaults to 4096, which is the RFC5625-recommended size.
+forwarder. Defaults to 1232, which is the recommended size following the
+DNS flag day in 2020. Only increase if you know what you are doing.
.TP
.B \-Q, --query-port=<query_port>
Send outbound DNS queries from, and listen for their replies on, the
diff --git a/src/config.h b/src/config.h
index 8c41943..62b7fa1 100644
--- a/src/config.h
+++ b/src/config.h
@@ -19,7 +19,7 @@
#define CHILD_LIFETIME 150 /* secs 'till terminated (RFC1035 suggests > 120s) */
#define TCP_MAX_QUERIES 100 /* Maximum number of queries per incoming TCP connection */
#define TCP_BACKLOG 32 /* kernel backlog limit for TCP connections */
-#define EDNS_PKTSZ 4096 /* default max EDNS.0 UDP packet from RFC5625 */
+#define EDNS_PKTSZ 1232 /* default max EDNS.0 UDP packet from from /dnsflagday.net/2020 */
#define SAFE_PKTSZ 1280 /* "go anywhere" UDP packet size */
#define KEYBLOCK_LEN 40 /* choose to minimise fragmentation when storing DNSSEC keys */
#define DNSSEC_WORK 50 /* Max number of queries to validate one question */
--
2.39.2

8
dnsmasq.spec
View File

@ -13,7 +13,7 @@
Name: dnsmasq
Version: 2.79
Release: 26%{?extraversion:.%{extraversion}}%{?dist}
Release: 27%{?extraversion:.%{extraversion}}%{?dist}
Summary: A lightweight DHCP/caching DNS server
License: GPLv2 or GPLv3
@ -83,6 +83,8 @@ Patch37: dnsmasq-2.81-linux-SIOCGSTAMP.patch
Patch38: dnsmasq-2.79-server-domain-fixup.patch
# https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;h=f8c77edbdffb8ada7753ea9fa104f0f6da70cfe3
Patch39: dnsmasq-2.81-dhcpv6-relay-link-address.patch
# https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;h=eb92fb32b746f2104b0f370b5b295bb8dd4bd5e5
Patch40: dnsmasq-2.89-edns0-size.patch
# This is workaround to nettle bug #1549190
# https://bugzilla.redhat.com/show_bug.cgi?id=1549190
@ -155,6 +157,7 @@ server's leases.
%patch37 -p1 -b .SIOCGSTAMP
%patch38 -p1 -b .rh2120357
%patch39 -p1 -b .rh2169355
%patch40 -p1 -b .CVE-2023-28450
# use /var/lib/dnsmasq instead of /var/lib/misc
for file in dnsmasq.conf.example man/dnsmasq.8 man/es/dnsmasq.8 src/config.h; do
@ -254,6 +257,9 @@ install -Dpm 644 %{SOURCE2} %{buildroot}%{_sysusersdir}/dnsmasq.conf
%{_mandir}/man1/dhcp_*
%changelog
* Mon Apr 03 2023 Petr Menšík <pemensik@redhat.com> - 2.79-27
- Limit offered EDNS0 size to 1232 (CVE-2023-28450)
* Wed Feb 15 2023 Petr Menšík <pemensik@redhat.com> - 2.79-26
- Avoid DHCPv6 relayed replies with Client Link-Layer Address (#2169355)