From: Kirill Isakov <bootctl@gmail.com>
Date: Fri, 27 May 2022 12:07:04 +0000 (+0600)
Subject: Don't tarpit localhost connections
X-Git-Url: https://git.tinc-vpn.org/git/browse?a=commitdiff_plain;h=ce4d55b72fd4290d4710f10e755f6dd9ed039d88;p=tinc

Don't tarpit localhost connections
---

diff --git a/src/net_socket.c b/src/net_socket.c
index 5d72471b..92dcbedb 100644
--- a/src/net_socket.c
+++ b/src/net_socket.c
@@ -689,32 +689,12 @@ remove:
 	list_delete(&outgoing_list, outgoing);
 }
 
-/*
-  accept a new tcp connect and create a
-  new connection
-*/
-void handle_new_meta_connection(void *data, int flags) {
-	(void)flags;
-	listen_socket_t *l = data;
-	connection_t *c;
-	sockaddr_t sa;
-	int fd;
-	socklen_t len = sizeof(sa);
-
-	fd = accept(l->tcp.fd, &sa.sa, &len);
-
-	if(fd < 0) {
-		logger(DEBUG_ALWAYS, LOG_ERR, "Accepting a new connection failed: %s", sockstrerror(sockerrno));
-		return;
-	}
-
-	sockaddrunmap(&sa);
-
+static bool check_tarpit(const sockaddr_t *sa, int fd) {
 	// Check if we get many connections from the same host
 
 	static sockaddr_t prev_sa;
 
-	if(!sockaddrcmp_noport(&sa, &prev_sa)) {
+	if(!sockaddrcmp_noport(sa, &prev_sa)) {
 		static time_t samehost_burst;
 		static time_t samehost_burst_time;
 
@@ -729,7 +709,7 @@ void handle_new_meta_connection(void *data, int flags) {
 
 		if(samehost_burst > max_connection_burst) {
 			tarpit(fd);
-			return;
+			return true;
 		}
 	}
 
@@ -752,6 +732,34 @@ void handle_new_meta_connection(void *data, int flags) {
 	if(connection_burst >= max_connection_burst) {
 		connection_burst = max_connection_burst;
 		tarpit(fd);
+		return true;
+	}
+
+	return false;
+}
+
+/*
+  accept a new tcp connect and create a
+  new connection
+*/
+void handle_new_meta_connection(void *data, int flags) {
+	(void)flags;
+	listen_socket_t *l = data;
+	connection_t *c;
+	sockaddr_t sa;
+	int fd;
+	socklen_t len = sizeof(sa);
+
+	fd = accept(l->tcp.fd, &sa.sa, &len);
+
+	if(fd < 0) {
+		logger(DEBUG_ALWAYS, LOG_ERR, "Accepting a new connection failed: %s", sockstrerror(sockerrno));
+		return;
+	}
+
+	sockaddrunmap(&sa);
+
+	if(!is_local_connection(&sa) && check_tarpit(&sa, fd)) {
 		return;
 	}
 
diff --git a/src/netutl.c b/src/netutl.c
index 0c19f5bb..6654f977 100644
--- a/src/netutl.c
+++ b/src/netutl.c
@@ -301,6 +301,23 @@ void sockaddr_setport(sockaddr_t *sa, const char *port) {
 	}
 }
 
+bool is_local_connection(const sockaddr_t *sa) {
+	switch(sa->sa.sa_family) {
+	case AF_INET:
+		// 127.0.0.0/8
+		return ntohl(sa->in.sin_addr.s_addr) >> 24 == 127;
+
+	case AF_INET6:
+		return IN6_IS_ADDR_LOOPBACK(&sa->in6.sin6_addr);
+
+	case AF_UNIX:
+		return true;
+
+	default:
+		return false;
+	}
+}
+
 uint16_t get_bound_port(int sockfd) {
 	sockaddr_t sa;
 	socklen_t salen = sizeof(sa);
diff --git a/src/netutl.h b/src/netutl.h
index 32181229..e8de4bbe 100644
--- a/src/netutl.h
+++ b/src/netutl.h
@@ -38,5 +38,6 @@ extern void sockaddrfree(sockaddr_t *sa);
 extern void sockaddrcpy(sockaddr_t *dest, const sockaddr_t *src);
 extern void sockaddr_setport(sockaddr_t *sa, const char *port);
 extern uint16_t get_bound_port(int sockfd);
+extern bool is_local_connection(const sockaddr_t *sa);
 
 #endif
diff --git a/test/unit/test_netutl.c b/test/unit/test_netutl.c
index a3486fcd..32bb6283 100644
--- a/test/unit/test_netutl.c
+++ b/test/unit/test_netutl.c
@@ -19,10 +19,60 @@ static void test_service_to_port_valid(void **state) {
 	assert_int_equal(1234, service_to_port("1234"));
 }
 
+static void test_is_local_connection_ipv4(void **state) {
+	(void)state;
+
+	sockaddr_t sa;
+
+	assert_true(inet_pton(AF_INET, "127.0.0.0", &sa.in.sin_addr));
+	sa.sa.sa_family = AF_INET;
+	assert_true(is_local_connection(&sa));
+
+	assert_true(inet_pton(AF_INET, "127.42.13.5", &sa.in.sin_addr));
+	sa.sa.sa_family = AF_INET;
+	assert_true(is_local_connection(&sa));
+
+	assert_true(inet_pton(AF_INET, "127.255.255.255", &sa.in.sin_addr));
+	sa.sa.sa_family = AF_INET;
+	assert_true(is_local_connection(&sa));
+
+	assert_true(inet_pton(AF_INET, "128.0.0.1", &sa.in.sin_addr));
+	sa.sa.sa_family = AF_INET;
+	assert_false(is_local_connection(&sa));
+}
+
+static void test_is_local_connection_ipv6(void **state) {
+	(void)state;
+
+	sockaddr_t sa;
+
+	assert_true(inet_pton(AF_INET6, "::1", &sa.in6.sin6_addr));
+	sa.sa.sa_family = AF_INET6;
+	assert_true(is_local_connection(&sa));
+
+	assert_true(inet_pton(AF_INET6, "::1:1", &sa.in6.sin6_addr));
+	sa.sa.sa_family = AF_INET6;
+	assert_false(is_local_connection(&sa));
+
+	assert_true(inet_pton(AF_INET6, "fe80::", &sa.in6.sin6_addr));
+	sa.sa.sa_family = AF_INET6;
+	assert_false(is_local_connection(&sa));
+}
+
+static void test_is_local_connection_unix(void **state) {
+	(void)state;
+
+	sockaddr_t sa = {.sa.sa_family = AF_UNIX};
+	assert_true(is_local_connection(&sa));
+}
+
 int main(void) {
 	const struct CMUnitTest tests[] = {
 		cmocka_unit_test(test_service_to_port_invalid),
 		cmocka_unit_test(test_service_to_port_valid),
+		cmocka_unit_test(test_is_local_connection_ipv4),
+		cmocka_unit_test(test_is_local_connection_ipv6),
+		cmocka_unit_test(test_is_local_connection_unix),
 	};
 	return cmocka_run_group_tests(tests, NULL, NULL);
 }