xtables: Fix for false-positive rule matching

When comparing two rules with non-standard targets, differences in
targets' payloads wasn't respected.

The cause is a rather hideous one: Unlike xtables_find_match(),
xtables_find_target() did not care whether the found target was already
in use or not, so the same target instance was assigned to both rules
and therefore payload comparison happened over the same memory location.

With legacy iptables it is not possible to reuse a target: The only case
where two rules (i.e., iptables_command_state instances) could exist at
the same time is when comparing rules, but that's handled using libiptc.

The above change clashes with ebtables-nft's reuse of target objects:
While input parsing still just assigns the object from xtables_targets
list, rule conversion from nftnl to iptables_command_state allocates new
data. To fix this, make ebtables-nft input parsing use the common
command_jump() routine instead of its own simplified copy. In turn, this
also eliminates the ebtables-nft-specific variants of parse_target(),
though with a slight change of behaviour: Names of user-defined chains
are no longer allowed to contain up to 31 but merely 28 characters.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>

6 files changed, 24 insertions, 71 deletions

diff --git a/iptables/nft-bridge.c b/iptables/nft-bridge.c
index b4265c8a..7c390dfa 100644
--- a/iptables/nft-bridge.c
+++ b/iptables/nft-bridge.c
@@ -45,6 +45,16 @@ void ebt_cs_clean(struct iptables_command_state *cs)
 		free(m);
 		m = nm;
 	}
+
+	if (cs->target) {
+		free(cs->target->t);
+		cs->target->t = NULL;
+
+		if (cs->target == cs->target->next) {
+			free(cs->target);
+			cs->target = NULL;
+		}
+	}
 }
 
 static void ebt_print_mac(const unsigned char *mac)
diff --git a/iptables/nft-bridge.h b/iptables/nft-bridge.h
index de52cd71..d90066f1 100644
--- a/iptables/nft-bridge.h
+++ b/iptables/nft-bridge.h
@@ -32,7 +32,6 @@ int ebt_get_mac_and_mask(const char *from, unsigned char *to, unsigned char *mas
  */
 
 #define EBT_TABLE_MAXNAMELEN 32
-#define EBT_CHAIN_MAXNAMELEN EBT_TABLE_MAXNAMELEN
 #define EBT_FUNCTION_MAXNAMELEN EBT_TABLE_MAXNAMELEN
 
 /* verdicts >0 are "branches" */
@@ -122,6 +121,5 @@ void ebt_add_match(struct xtables_match *m,
 void ebt_add_watcher(struct xtables_target *watcher,
                      struct iptables_command_state *cs);
 int ebt_command_default(struct iptables_command_state *cs);
-struct xtables_target *ebt_command_jump(const char *jumpto);
 
 #endif
diff --git a/iptables/nft-shared.c b/iptables/nft-shared.c
index 2d4b8d55..a72d414d 100644
--- a/iptables/nft-shared.c
+++ b/iptables/nft-shared.c
@@ -687,6 +687,11 @@ void nft_clear_iptables_command_state(struct iptables_command_state *cs)
 	if (cs->target) {
 		free(cs->target->t);
 		cs->target->t = NULL;
+
+		if (cs->target == cs->target->next) {
+			free(cs->target);
+			cs->target = NULL;
+		}
 	}
 }
 
diff --git a/iptables/tests/shell/testcases/iptables/0005-delete-rules_0 b/iptables/tests/shell/testcases/iptables/0005-delete-rules_0
index 9312fd53..5038cbce 100755
--- a/iptables/tests/shell/testcases/iptables/0005-delete-rules_0
+++ b/iptables/tests/shell/testcases/iptables/0005-delete-rules_0
@@ -5,3 +5,10 @@
 $XT_MULTI iptables -A FORWARD -i eth23 -o eth42 -j DROP
 $XT_MULTI iptables -D FORWARD -i eth23 -o eth42 -j REJECT
 [[ $? -eq 1 ]] || exit 1
+
+# test incorrect deletion of rules with deviating payload
+# in non-standard target
+
+$XT_MULTI iptables -A FORWARD -i eth23 -o eth42 -j MARK --set-mark 23
+$XT_MULTI iptables -D FORWARD -i eth23 -o eth42 -j MARK --set-mark 42
+[[ $? -eq 1 ]] || exit 1
diff --git a/iptables/xtables-eb-translate.c b/iptables/xtables-eb-translate.c
index f98c3855..0fe14d2d 100644
--- a/iptables/xtables-eb-translate.c
+++ b/iptables/xtables-eb-translate.c
@@ -64,27 +64,6 @@ static int parse_rule_number(const char *rule)
 	return rule_nr;
 }
 
-static const char *
-parse_target(const char *targetname)
-{
-	const char *ptr;
-
-	if (strlen(targetname) < 1)
-		xtables_error(PARAMETER_PROBLEM,
-			      "Invalid target name (too short)");
-
-	if (strlen(targetname)+1 > EBT_CHAIN_MAXNAMELEN)
-		xtables_error(PARAMETER_PROBLEM,
-			      "Invalid target '%s' (%d chars max)",
-			      targetname, EBT_CHAIN_MAXNAMELEN);
-
-	for (ptr = targetname; *ptr; ptr++)
-		if (isspace(*ptr))
-			xtables_error(PARAMETER_PROBLEM,
-				      "Invalid target name `%s'", targetname);
-	return targetname;
-}
-
 static int get_current_chain(const char *chain)
 {
 	if (strcmp(chain, "PREROUTING") == 0)
@@ -411,8 +390,7 @@ print_zero:
 				break;
 			} else if (c == 'j') {
 				ebt_check_option2(&flags, OPT_JUMP);
-				cs.jumpto = parse_target(optarg);
-				cs.target = ebt_command_jump(cs.jumpto);
+				command_jump(&cs);
 				break;
 			} else if (c == 's') {
 				ebt_check_option2(&flags, OPT_SOURCE);
diff --git a/iptables/xtables-eb.c b/iptables/xtables-eb.c
index b9d98a05..75d43963 100644
--- a/iptables/xtables-eb.c
+++ b/iptables/xtables-eb.c
@@ -139,27 +139,6 @@ static int parse_rule_number(const char *rule)
 	return rule_nr;
 }
 
-static const char *
-parse_target(const char *targetname)
-{
-	const char *ptr;
-
-	if (strlen(targetname) < 1)
-		xtables_error(PARAMETER_PROBLEM,
-			      "Invalid target name (too short)");
-
-	if (strlen(targetname)+1 > EBT_CHAIN_MAXNAMELEN)
-		xtables_error(PARAMETER_PROBLEM,
-			      "Invalid target '%s' (%d chars max)",
-			      targetname, EBT_CHAIN_MAXNAMELEN);
-
-	for (ptr = targetname; *ptr; ptr++)
-		if (isspace(*ptr))
-			xtables_error(PARAMETER_PROBLEM,
-				      "Invalid target name `%s'", targetname);
-	return targetname;
-}
-
 static int
 append_entry(struct nft_handle *h,
 	     const char *chain,
@@ -365,29 +344,6 @@ static struct option *merge_options(struct option *oldopts,
 	return merge;
 }
 
-/*
- * More glue code.
- */
-struct xtables_target *ebt_command_jump(const char *jumpto)
-{
-	struct xtables_target *target;
-	unsigned int verdict;
-
-	/* Standard target? */
-	if (!ebt_fill_target(jumpto, &verdict))
-		jumpto = "standard";
-
-	/* For ebtables, all targets are preloaded. Hence it is either in
-	 * xtables_targets or a custom chain to jump to, in which case
-	 * returning NULL is fine. */
-	for (target = xtables_targets; target; target = target->next) {
-		if (!strcmp(target->name, jumpto))
-			break;
-	}
-
-	return target;
-}
-
 static void print_help(const struct xtables_target *t,
 		       const struct xtables_rule_match *m, const char *table)
 {
@@ -1055,8 +1011,7 @@ print_zero:
 			} else if (c == 'j') {
 				ebt_check_option2(&flags, OPT_JUMP);
 				if (strcmp(optarg, "CONTINUE") != 0) {
-					cs.jumpto = parse_target(optarg);
-					cs.target = ebt_command_jump(cs.jumpto);
+					command_jump(&cs);
 				}
 				break;
 			} else if (c == 's') {