Git init

1 files changed, 395 insertions, 0 deletions

diff --git a/extensions/libxt_tcp.c b/extensions/libxt_tcp.c
new file mode 100644
index 0000000..75551d7
--- /dev/null
+++ b/extensions/libxt_tcp.c
@@ -0,0 +1,395 @@
+/* Shared library add-on to iptables to add TCP support. */
+#include <stdio.h>
+#include <netdb.h>
+#include <string.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <netinet/in.h>
+#include <xtables.h>
+#include <linux/netfilter/xt_tcpudp.h>
+
+static void tcp_help(void)
+{
+	printf(
+"tcp match options:\n"
+"[!] --tcp-flags mask comp	match when TCP flags & mask == comp\n"
+"				(Flags: SYN ACK FIN RST URG PSH ALL NONE)\n"
+"[!] --syn			match when only SYN flag set\n"
+"				(equivalent to --tcp-flags SYN,RST,ACK,FIN SYN)\n"
+"[!] --source-port port[:port]\n"
+" --sport ...\n"
+"				match source port(s)\n"
+"[!] --destination-port port[:port]\n"
+" --dport ...\n"
+"				match destination port(s)\n"
+"[!] --tcp-option number        match if TCP option set\n");
+}
+
+static const struct option tcp_opts[] = {
+	{ "source-port", 1, NULL, '1' },
+	{ "sport", 1, NULL, '1' }, /* synonym */
+	{ "destination-port", 1, NULL, '2' },
+	{ "dport", 1, NULL, '2' }, /* synonym */
+	{ "syn", 0, NULL, '3' },
+	{ "tcp-flags", 1, NULL, '4' },
+	{ "tcp-option", 1, NULL, '5' },
+	{ .name = NULL }
+};
+
+static void
+parse_tcp_ports(const char *portstring, u_int16_t *ports)
+{
+	char *buffer;
+	char *cp;
+
+	buffer = strdup(portstring);
+	if ((cp = strchr(buffer, ':')) == NULL)
+		ports[0] = ports[1] = xtables_parse_port(buffer, "tcp");
+	else {
+		*cp = '\0';
+		cp++;
+
+		ports[0] = buffer[0] ? xtables_parse_port(buffer, "tcp") : 0;
+		ports[1] = cp[0] ? xtables_parse_port(cp, "tcp") : 0xFFFF;
+
+		if (ports[0] > ports[1])
+			xtables_error(PARAMETER_PROBLEM,
+				   "invalid portrange (min > max)");
+	}
+	free(buffer);
+}
+
+struct tcp_flag_names {
+	const char *name;
+	unsigned int flag;
+};
+
+static const struct tcp_flag_names tcp_flag_names[]
+= { { "FIN", 0x01 },
+    { "SYN", 0x02 },
+    { "RST", 0x04 },
+    { "PSH", 0x08 },
+    { "ACK", 0x10 },
+    { "URG", 0x20 },
+    { "ALL", 0x3F },
+    { "NONE", 0 },
+};
+
+static unsigned int
+parse_tcp_flag(const char *flags)
+{
+	unsigned int ret = 0;
+	char *ptr;
+	char *buffer;
+
+	buffer = strdup(flags);
+
+	for (ptr = strtok(buffer, ","); ptr; ptr = strtok(NULL, ",")) {
+		unsigned int i;
+		for (i = 0; i < ARRAY_SIZE(tcp_flag_names); ++i)
+			if (strcasecmp(tcp_flag_names[i].name, ptr) == 0) {
+				ret |= tcp_flag_names[i].flag;
+				break;
+			}
+		if (i == ARRAY_SIZE(tcp_flag_names))
+			xtables_error(PARAMETER_PROBLEM,
+				   "Unknown TCP flag `%s'", ptr);
+	}
+
+	free(buffer);
+	return ret;
+}
+
+static void
+parse_tcp_flags(struct xt_tcp *tcpinfo,
+		const char *mask,
+		const char *cmp,
+		int invert)
+{
+	tcpinfo->flg_mask = parse_tcp_flag(mask);
+	tcpinfo->flg_cmp = parse_tcp_flag(cmp);
+
+	if (invert)
+		tcpinfo->invflags |= XT_TCP_INV_FLAGS;
+}
+
+static void
+parse_tcp_option(const char *option, u_int8_t *result)
+{
+	unsigned int ret;
+
+	if (!xtables_strtoui(option, NULL, &ret, 1, UINT8_MAX))
+		xtables_error(PARAMETER_PROBLEM, "Bad TCP option \"%s\"", option);
+
+	*result = ret;
+}
+
+static void tcp_init(struct xt_entry_match *m)
+{
+	struct xt_tcp *tcpinfo = (struct xt_tcp *)m->data;
+
+	tcpinfo->spts[1] = tcpinfo->dpts[1] = 0xFFFF;
+}
+
+#define TCP_SRC_PORTS 0x01
+#define TCP_DST_PORTS 0x02
+#define TCP_FLAGS 0x04
+#define TCP_OPTION	0x08
+
+static int
+tcp_parse(int c, char **argv, int invert, unsigned int *flags,
+          const void *entry, struct xt_entry_match **match)
+{
+	struct xt_tcp *tcpinfo = (struct xt_tcp *)(*match)->data;
+
+	switch (c) {
+	case '1':
+		if (*flags & TCP_SRC_PORTS)
+			xtables_error(PARAMETER_PROBLEM,
+				   "Only one `--source-port' allowed");
+		xtables_check_inverse(optarg, &invert, &optind, 0, argv);
+		parse_tcp_ports(optarg, tcpinfo->spts);
+		if (invert)
+			tcpinfo->invflags |= XT_TCP_INV_SRCPT;
+		*flags |= TCP_SRC_PORTS;
+		break;
+
+	case '2':
+		if (*flags & TCP_DST_PORTS)
+			xtables_error(PARAMETER_PROBLEM,
+				   "Only one `--destination-port' allowed");
+		xtables_check_inverse(optarg, &invert, &optind, 0, argv);
+		parse_tcp_ports(optarg, tcpinfo->dpts);
+		if (invert)
+			tcpinfo->invflags |= XT_TCP_INV_DSTPT;
+		*flags |= TCP_DST_PORTS;
+		break;
+
+	case '3':
+		if (*flags & TCP_FLAGS)
+			xtables_error(PARAMETER_PROBLEM,
+				   "Only one of `--syn' or `--tcp-flags' "
+				   " allowed");
+		parse_tcp_flags(tcpinfo, "SYN,RST,ACK,FIN", "SYN", invert);
+		*flags |= TCP_FLAGS;
+		break;
+
+	case '4':
+		if (*flags & TCP_FLAGS)
+			xtables_error(PARAMETER_PROBLEM,
+				   "Only one of `--syn' or `--tcp-flags' "
+				   " allowed");
+		xtables_check_inverse(optarg, &invert, &optind, 0, argv);
+
+		if (!argv[optind]
+		    || argv[optind][0] == '-' || argv[optind][0] == '!')
+			xtables_error(PARAMETER_PROBLEM,
+				   "--tcp-flags requires two args.");
+
+		parse_tcp_flags(tcpinfo, optarg, argv[optind],
+				invert);
+		optind++;
+		*flags |= TCP_FLAGS;
+		break;
+
+	case '5':
+		if (*flags & TCP_OPTION)
+			xtables_error(PARAMETER_PROBLEM,
+				   "Only one `--tcp-option' allowed");
+		xtables_check_inverse(optarg, &invert, &optind, 0, argv);
+		parse_tcp_option(optarg, &tcpinfo->option);
+		if (invert)
+			tcpinfo->invflags |= XT_TCP_INV_OPTION;
+		*flags |= TCP_OPTION;
+		break;
+
+	default:
+		return 0;
+	}
+
+	return 1;
+}
+
+static char *
+port_to_service(int port)
+{
+	struct servent *service;
+
+	if ((service = getservbyport(htons(port), "tcp")))
+		return service->s_name;
+
+	return NULL;
+}
+
+static void
+print_port(u_int16_t port, int numeric)
+{
+	char *service;
+
+	if (numeric || (service = port_to_service(port)) == NULL)
+		printf("%u", port);
+	else
+		printf("%s", service);
+}
+
+static void
+print_ports(const char *name, u_int16_t min, u_int16_t max,
+	    int invert, int numeric)
+{
+	const char *inv = invert ? "!" : "";
+
+	if (min != 0 || max != 0xFFFF || invert) {
+		printf("%s", name);
+		if (min == max) {
+			printf(":%s", inv);
+			print_port(min, numeric);
+		} else {
+			printf("s:%s", inv);
+			print_port(min, numeric);
+			printf(":");
+			print_port(max, numeric);
+		}
+		printf(" ");
+	}
+}
+
+static void
+print_option(u_int8_t option, int invert, int numeric)
+{
+	if (option || invert)
+		printf("option=%s%u ", invert ? "!" : "", option);
+}
+
+static void
+print_tcpf(u_int8_t flags)
+{
+	int have_flag = 0;
+
+	while (flags) {
+		unsigned int i;
+
+		for (i = 0; (flags & tcp_flag_names[i].flag) == 0; i++);
+
+		if (have_flag)
+			printf(",");
+		printf("%s", tcp_flag_names[i].name);
+		have_flag = 1;
+
+		flags &= ~tcp_flag_names[i].flag;
+	}
+
+	if (!have_flag)
+		printf("NONE");
+}
+
+static void
+print_flags(u_int8_t mask, u_int8_t cmp, int invert, int numeric)
+{
+	if (mask || invert) {
+		printf("flags:%s", invert ? "!" : "");
+		if (numeric)
+			printf("0x%02X/0x%02X ", mask, cmp);
+		else {
+			print_tcpf(mask);
+			printf("/");
+			print_tcpf(cmp);
+			printf(" ");
+		}
+	}
+}
+
+static void
+tcp_print(const void *ip, const struct xt_entry_match *match, int numeric)
+{
+	const struct xt_tcp *tcp = (struct xt_tcp *)match->data;
+
+	printf("tcp ");
+	print_ports("spt", tcp->spts[0], tcp->spts[1],
+		    tcp->invflags & XT_TCP_INV_SRCPT,
+		    numeric);
+	print_ports("dpt", tcp->dpts[0], tcp->dpts[1],
+		    tcp->invflags & XT_TCP_INV_DSTPT,
+		    numeric);
+	print_option(tcp->option,
+		     tcp->invflags & XT_TCP_INV_OPTION,
+		     numeric);
+	print_flags(tcp->flg_mask, tcp->flg_cmp,
+		    tcp->invflags & XT_TCP_INV_FLAGS,
+		    numeric);
+	if (tcp->invflags & ~XT_TCP_INV_MASK)
+		printf("Unknown invflags: 0x%X ",
+		       tcp->invflags & ~XT_TCP_INV_MASK);
+}
+
+static void tcp_save(const void *ip, const struct xt_entry_match *match)
+{
+	const struct xt_tcp *tcpinfo = (struct xt_tcp *)match->data;
+
+	if (tcpinfo->spts[0] != 0
+	    || tcpinfo->spts[1] != 0xFFFF) {
+		if (tcpinfo->invflags & XT_TCP_INV_SRCPT)
+			printf("! ");
+		if (tcpinfo->spts[0]
+		    != tcpinfo->spts[1])
+			printf("--sport %u:%u ",
+			       tcpinfo->spts[0],
+			       tcpinfo->spts[1]);
+		else
+			printf("--sport %u ",
+			       tcpinfo->spts[0]);
+	}
+
+	if (tcpinfo->dpts[0] != 0
+	    || tcpinfo->dpts[1] != 0xFFFF) {
+		if (tcpinfo->invflags & XT_TCP_INV_DSTPT)
+			printf("! ");
+		if (tcpinfo->dpts[0]
+		    != tcpinfo->dpts[1])
+			printf("--dport %u:%u ",
+			       tcpinfo->dpts[0],
+			       tcpinfo->dpts[1]);
+		else
+			printf("--dport %u ",
+			       tcpinfo->dpts[0]);
+	}
+
+	if (tcpinfo->option
+	    || (tcpinfo->invflags & XT_TCP_INV_OPTION)) {
+		if (tcpinfo->invflags & XT_TCP_INV_OPTION)
+			printf("! ");
+		printf("--tcp-option %u ", tcpinfo->option);
+	}
+
+	if (tcpinfo->flg_mask
+	    || (tcpinfo->invflags & XT_TCP_INV_FLAGS)) {
+		if (tcpinfo->invflags & XT_TCP_INV_FLAGS)
+			printf("! ");
+		printf("--tcp-flags ");
+		if (tcpinfo->flg_mask != 0xFF) {
+			print_tcpf(tcpinfo->flg_mask);
+		}
+		printf(" ");
+		print_tcpf(tcpinfo->flg_cmp);
+		printf(" ");
+	}
+}
+
+static struct xtables_match tcp_match = {
+	.family		= NFPROTO_UNSPEC,
+	.name		= "tcp",
+	.version	= XTABLES_VERSION,
+	.size		= XT_ALIGN(sizeof(struct xt_tcp)),
+	.userspacesize	= XT_ALIGN(sizeof(struct xt_tcp)),
+	.help		= tcp_help,
+	.init		= tcp_init,
+	.parse		= tcp_parse,
+	.print		= tcp_print,
+	.save		= tcp_save,
+	.extra_opts	= tcp_opts,
+};
+
+void
+_init(void)
+{
+	xtables_register_match(&tcp_match);
+}