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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 ffed6aa9a4
commit a84d6321e9
2 changed files with 51 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

7
dnsmasq.spec
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@ -20,7 +20,7 @@
Name: dnsmasq
Version: 2.85
Release: 6%{?extraversion:.%{extraversion}}%{?dist}
Release: 7%{?extraversion:.%{extraversion}}%{?dist}
Summary: A lightweight DHCP/caching DNS server
License: GPLv2 or GPLv3
@ -51,6 +51,8 @@ Patch6: dnsmasq-2.86-dhcpv6-client-arch.patch
Patch7: dnsmasq-2.87-CVE-2022-0934.patch
# Downstream only patch; fixes Patch4 change
Patch8: dnsmasq-2.79-server-domain-fixup.patch
# https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;h=eb92fb32b746f2104b0f370b5b295bb8dd4bd5e5
Patch9: dnsmasq-2.89-edns0-size.patch
# This is workaround to nettle bug #1549190
# https://bugzilla.redhat.com/show_bug.cgi?id=1549190
@ -194,6 +196,9 @@ install -Dpm 644 %{SOURCE2} %{buildroot}%{_sysusersdir}/%{name}.conf
%{_mandir}/man1/dhcp_*
%changelog
* Mon Apr 03 2023 Petr Menšík <pemensik@redhat.com> - 2.85-7
- Limit offered EDNS0 size 1232 (CVE-2023-28450)
* Thu Jan 26 2023 Petr Menšík <pemensik@redhat.com> - 2.85-6
- Use upstream change for CVE-2022-0934 (#2126586)