Set the default maximum DNS UDP packet size to 1232

Resolves: CVE-2023-28450

dnsmasq-2.89-edns0-size.patch

@@ -0,0 +1,45 @@
+From 559357d267197602d591a8a075146ab35146dbc6 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 9dd5430..8956f6d 100644
+--- a/man/dnsmasq.8
++++ b/man/dnsmasq.8
+@@ -183,7 +183,8 @@ 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 492c02f..f6d96db 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 1232 /* "go anywhere" UDP packet size, see https://dnsflagday.net/2020/ */
+ #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
+

dnsmasq.spec

@@ -23,7 +23,7 @@
 
 Name:           dnsmasq
 Version:        2.89
-Release:        1%{?extraversion:.%{extraversion}}%{?dist}
+Release:        2%{?extraversion:.%{extraversion}}%{?dist}
 Summary:        A lightweight DHCP/caching DNS server
 
 # SPDX identifiers already
@@ -45,6 +45,8 @@ Patch1:         dnsmasq-2.77-underflow.patch
 # https://bugzilla.redhat.com/show_bug.cgi?id=1852373
 Patch2:         dnsmasq-2.81-configuration.patch
 Patch3:         dnsmasq-2.78-fips.patch
+# https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;h=eb92fb32b746f2104b0f370b5b295bb8dd4bd5e5
+Patch4:         dnsmasq-2.89-edns0-size.patch
 
 
 Requires:       nettle
@@ -212,6 +214,9 @@ install -Dpm 644 %{SOURCE2} %{buildroot}%{_sysusersdir}/%{name}.conf
 %endif
 
 %changelog
+* Mon Apr 03 2023 Petr Menšík <pemensik@redhat.com> - 2.89-2
+- Limit offered EDNS0 size 1232 (CVE-2023-28450)
+
 * Mon Feb 13 2023 Petr Menšík <pemensik@redhat.com> - 2.89-1
 - Update to 2.89 (#2167121)