From 572692f0bdd6a3fabe3dd4a3e8e5565cc69b5e14 Mon Sep 17 00:00:00 2001
From: Ronan Pigott <ronan@rjp.ie>
Date: Sun, 25 Feb 2024 00:23:32 -0700
Subject: [PATCH] resolved: reduce the maximum nsec3 iterations to 100

According to RFC9267, the 2500 value is not helpful, and in fact it can
be harmful to permit a large number of iterations. Combined with limits
on the number of signature validations, I expect this will mitigate the
impact of maliciously crafted domains designed to cause excessive
cryptographic work.

(cherry picked from commit eba291124bc11f03732d1fc468db3bfac069f9cb)

Conflict:NA
Reference:https://github.com/systemd/systemd-stable/commit/572692f0bdd6a3fabe3dd4a3e8e5565cc69b5e14

---
 src/resolve/resolved-dns-dnssec.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/resolve/resolved-dns-dnssec.c b/src/resolve/resolved-dns-dnssec.c
index aa87820dca..a192d82083 100644
--- a/src/resolve/resolved-dns-dnssec.c
+++ b/src/resolve/resolved-dns-dnssec.c
@@ -28,8 +28,9 @@ DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(EC_KEY*, EC_KEY_free, NULL);
 /* Permit a maximum clock skew of 1h 10min. This should be enough to deal with DST confusion */
 #define SKEW_MAX (1*USEC_PER_HOUR + 10*USEC_PER_MINUTE)
 
-/* Maximum number of NSEC3 iterations we'll do. RFC5155 says 2500 shall be the maximum useful value */
-#define NSEC3_ITERATIONS_MAX 2500
+/* Maximum number of NSEC3 iterations we'll do. RFC5155 says 2500 shall be the maximum useful value, but
+ * RFC9276 § 3.2 says that we should reduce the acceptable iteration count */
+#define NSEC3_ITERATIONS_MAX 100
 
 /*
  * The DNSSEC Chain of trust:
-- 
2.33.0

