iptables/iptables-nft-fix-interface-comparisons.patch

 From 40406dbfaefbc204134452b2747bae4f6a122848 Mon Sep 17 00:00:00 2001
From: Jeremy Sowden <jeremy@azazel.net>
Date: Mon, 18 Nov 2024 13:56:50 +0000
Subject: nft: fix interface comparisons in `-C` commands

Commit 9ccae6397475 ("nft: Leave interface masks alone when parsing from
kernel") removed code which explicitly set interface masks to all ones.  The
result of this is that they are zero.  However, they are used to mask interfaces
in `is_same_interfaces`.  Consequently, the masked values are alway zero, the
comparisons are always true, and check commands which ought to fail succeed:

  # iptables -N test
  # iptables -A test -i lo \! -o lo -j REJECT
  # iptables -v -L test
  Chain test (0 references)
   pkts bytes target     prot opt in     out     source               destination
      0     0 REJECT     all  --  lo     !lo     anywhere             anywhere             reject-with icmp-port-unreachable
  # iptables -v -C test -i abcdefgh \! -o abcdefgh -j REJECT
  REJECT  all opt -- in lo out !lo  0.0.0.0/0  -> 0.0.0.0/0   reject-with icmp-port-unreachable

Remove the mask parameters from `is_same_interfaces`.  Add a test-case.

Fixes: 9ccae6397475 ("nft: Leave interface masks alone when parsing from kernel")
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 iptables/nft-arp.c                                 | 10 ++----
 iptables/nft-ipv4.c                                |  4 +--
 iptables/nft-ipv6.c                                |  6 +---
 iptables/nft-shared.c                              | 36 +++++-----------------
 iptables/nft-shared.h                              |  6 +---
 .../testcases/nft-only/0020-compare-interfaces_0   |  9 ++++++
 6 files changed, 22 insertions(+), 49 deletions(-)
 create mode 100755 iptables/tests/shell/testcases/nft-only/0020-compare-interfaces_0

diff --git a/iptables/nft-arp.c b/iptables/nft-arp.c
index 264864c3..c11d64c3 100644
--- a/iptables/nft-arp.c
+++ b/iptables/nft-arp.c
@@ -385,14 +385,8 @@ static bool nft_arp_is_same(const struct iptables_command_state *cs_a,
 		return false;
 	}
 
-	return is_same_interfaces(a->arp.iniface,
-				  a->arp.outiface,
-				  (unsigned char *)a->arp.iniface_mask,
-				  (unsigned char *)a->arp.outiface_mask,
-				  b->arp.iniface,
-				  b->arp.outiface,
-				  (unsigned char *)b->arp.iniface_mask,
-				  (unsigned char *)b->arp.outiface_mask);
+	return is_same_interfaces(a->arp.iniface, a->arp.outiface,
+				  b->arp.iniface, b->arp.outiface);
 }
 
 static void nft_arp_save_chain(const struct nftnl_chain *c, const char *policy)
diff --git a/iptables/nft-ipv4.c b/iptables/nft-ipv4.c
index 74092875..0c8bd291 100644
--- a/iptables/nft-ipv4.c
+++ b/iptables/nft-ipv4.c
@@ -113,9 +113,7 @@ static bool nft_ipv4_is_same(const struct iptables_command_state *a,
 	}
 
 	return is_same_interfaces(a->fw.ip.iniface, a->fw.ip.outiface,
-				  a->fw.ip.iniface_mask, a->fw.ip.outiface_mask,
-				  b->fw.ip.iniface, b->fw.ip.outiface,
-				  b->fw.ip.iniface_mask, b->fw.ip.outiface_mask);
+				  b->fw.ip.iniface, b->fw.ip.outiface);
 }
 
 static void nft_ipv4_set_goto_flag(struct iptables_command_state *cs)
diff --git a/iptables/nft-ipv6.c b/iptables/nft-ipv6.c
index b184f8af..4dbb2af2 100644
--- a/iptables/nft-ipv6.c
+++ b/iptables/nft-ipv6.c
@@ -99,11 +99,7 @@ static bool nft_ipv6_is_same(const struct iptables_command_state *a,
 	}
 
 	return is_same_interfaces(a->fw6.ipv6.iniface, a->fw6.ipv6.outiface,
-				  a->fw6.ipv6.iniface_mask,
-				  a->fw6.ipv6.outiface_mask,
-				  b->fw6.ipv6.iniface, b->fw6.ipv6.outiface,
-				  b->fw6.ipv6.iniface_mask,
-				  b->fw6.ipv6.outiface_mask);
+				  b->fw6.ipv6.iniface, b->fw6.ipv6.outiface);
 }
 
 static void nft_ipv6_set_goto_flag(struct iptables_command_state *cs)
diff --git a/iptables/nft-shared.c b/iptables/nft-shared.c
index 6775578b..2c29e68f 100644
--- a/iptables/nft-shared.c
+++ b/iptables/nft-shared.c
@@ -220,36 +220,16 @@ void add_l4proto(struct nft_handle *h, struct nftnl_rule *r,
 }
 
 bool is_same_interfaces(const char *a_iniface, const char *a_outiface,
-			unsigned const char *a_iniface_mask,
-			unsigned const char *a_outiface_mask,
-			const char *b_iniface, const char *b_outiface,
-			unsigned const char *b_iniface_mask,
-			unsigned const char *b_outiface_mask)
+			const char *b_iniface, const char *b_outiface)
 {
-	int i;
-
-	for (i = 0; i < IFNAMSIZ; i++) {
-		if (a_iniface_mask[i] != b_iniface_mask[i]) {
-			DEBUGP("different iniface mask %x, %x (%d)\n",
-			a_iniface_mask[i] & 0xff, b_iniface_mask[i] & 0xff, i);
-			return false;
-		}
-		if ((a_iniface[i] & a_iniface_mask[i])
-		    != (b_iniface[i] & b_iniface_mask[i])) {
-			DEBUGP("different iniface\n");
-			return false;
-		}
-		if (a_outiface_mask[i] != b_outiface_mask[i]) {
-			DEBUGP("different outiface mask\n");
-			return false;
-		}
-		if ((a_outiface[i] & a_outiface_mask[i])
-		    != (b_outiface[i] & b_outiface_mask[i])) {
-			DEBUGP("different outiface\n");
-			return false;
-		}
+	if (strncmp(a_iniface, b_iniface, IFNAMSIZ)) {
+		DEBUGP("different iniface\n");
+		return false;
+	}
+	if (strncmp(a_outiface, b_outiface, IFNAMSIZ)) {
+		DEBUGP("different outiface\n");
+		return false;
 	}
-
 	return true;
 }
 
diff --git a/iptables/nft-shared.h b/iptables/nft-shared.h
index 51d1e460..b57aee1f 100644
--- a/iptables/nft-shared.h
+++ b/iptables/nft-shared.h
@@ -105,11 +105,7 @@ void add_l4proto(struct nft_handle *h, struct nftnl_rule *r, uint8_t proto, uint
 void add_compat(struct nftnl_rule *r, uint32_t proto, bool inv);
 
 bool is_same_interfaces(const char *a_iniface, const char *a_outiface,
-			unsigned const char *a_iniface_mask,
-			unsigned const char *a_outiface_mask,
-			const char *b_iniface, const char *b_outiface,
-			unsigned const char *b_iniface_mask,
-			unsigned const char *b_outiface_mask);
+			const char *b_iniface, const char *b_outiface);
 
 void __get_cmp_data(struct nftnl_expr *e, void *data, size_t dlen, uint8_t *op);
 void get_cmp_data(struct nftnl_expr *e, void *data, size_t dlen, bool *inv);
diff --git a/iptables/tests/shell/testcases/nft-only/0020-compare-interfaces_0 b/iptables/tests/shell/testcases/nft-only/0020-compare-interfaces_0
new file mode 100755
index 00000000..278cd648
--- /dev/null
+++ b/iptables/tests/shell/testcases/nft-only/0020-compare-interfaces_0
@@ -0,0 +1,9 @@
+#!/bin/bash
+
+[[ $XT_MULTI == *xtables-nft-multi ]] || { echo "skip $XT_MULTI"; exit 0; }
+
+$XT_MULTI iptables -N test
+$XT_MULTI iptables -A test -i lo \! -o lo -j REJECT
+$XT_MULTI iptables -C test -i abcdefgh \! -o abcdefgh -j REJECT 2>/dev/null && exit 1
+
+exit 0
-- 
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