blob: 4d914e39a1feb55592563dcbe211a5396b5a633b [file] [log] [blame]
/* Shared library add-on to iptables to add TCP support. */
#include <stdbool.h>
#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[] = {
{.name = "source-port", .has_arg = true, .val = '1'},
{.name = "sport", .has_arg = true, .val = '1'}, /* synonym */
{.name = "destination-port", .has_arg = true, .val = '2'},
{.name = "dport", .has_arg = true, .val = '2'}, /* synonym */
{.name = "syn", .has_arg = false, .val = '3'},
{.name = "tcp-flags", .has_arg = true, .val = '4'},
{.name = "tcp-option", .has_arg = true, .val = '5'},
XT_GETOPT_TABLEEND,
};
static void
parse_tcp_ports(const char *portstring, uint16_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, uint8_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;
}
return 1;
}
static const char *
port_to_service(int port)
{
const struct servent *service;
if ((service = getservbyport(htons(port), "tcp")))
return service->s_name;
return NULL;
}
static void
print_port(uint16_t port, int numeric)
{
const char *service;
if (numeric || (service = port_to_service(port)) == NULL)
printf("%u", port);
else
printf("%s", service);
}
static void
print_ports(const char *name, uint16_t min, uint16_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);
}
}
}
static void
print_option(uint8_t option, int invert, int numeric)
{
if (option || invert)
printf(" option=%s%u", invert ? "!" : "", option);
}
static void
print_tcpf(uint8_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(uint8_t mask, uint8_t cmp, int invert, int numeric)
{
if (mask || invert) {
printf("flags:%s", invert ? "!" : "");
if (numeric)
printf(" 0x%02X/0x%02X", mask, cmp);
else {
printf(" ");
print_tcpf(mask);
printf("/");
print_tcpf(cmp);
}
}
}
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);
}
}
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);
}