blob: e5db6376f2fdd92ec98f90f41be0461ae601225f [file] [log] [blame]
/* 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 <xtables.h>
#include <linux/netfilter/xt_tcpudp.h>
/* Function which prints out usage message. */
static void
help(void)
{
printf(
"TCP v%s 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\n",
IPTABLES_VERSION);
}
static const struct option opts[] = {
{ "source-port", 1, 0, '1' },
{ "sport", 1, 0, '1' }, /* synonym */
{ "destination-port", 1, 0, '2' },
{ "dport", 1, 0, '2' }, /* synonym */
{ "syn", 0, 0, '3' },
{ "tcp-flags", 1, 0, '4' },
{ "tcp-option", 1, 0, '5' },
{0}
};
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] = parse_port(buffer, "tcp");
else {
*cp = '\0';
cp++;
ports[0] = buffer[0] ? parse_port(buffer, "tcp") : 0;
ports[1] = cp[0] ? parse_port(cp, "tcp") : 0xFFFF;
if (ports[0] > ports[1])
exit_error(PARAMETER_PROBLEM,
"invalid portrange (min > max)");
}
free(buffer);
}
struct tcp_flag_names {
const char *name;
unsigned int flag;
};
static 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 < sizeof(tcp_flag_names)/sizeof(struct tcp_flag_names);
i++) {
if (strcasecmp(tcp_flag_names[i].name, ptr) == 0) {
ret |= tcp_flag_names[i].flag;
break;
}
}
if (i == sizeof(tcp_flag_names)/sizeof(struct tcp_flag_names))
exit_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 (string_to_number(option, 1, 255, &ret) == -1)
exit_error(PARAMETER_PROBLEM, "Bad TCP option `%s'", option);
*result = (u_int8_t)ret;
}
/* Initialize the match. */
static void
init(struct xt_entry_match *m, unsigned int *nfcache)
{
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
/* Function which parses command options; returns true if it
ate an option. */
static int
parse(int c, char **argv, int invert, unsigned int *flags,
const void *entry,
unsigned int *nfcache,
struct xt_entry_match **match)
{
struct xt_tcp *tcpinfo = (struct xt_tcp *)(*match)->data;
switch (c) {
case '1':
if (*flags & TCP_SRC_PORTS)
exit_error(PARAMETER_PROBLEM,
"Only one `--source-port' allowed");
check_inverse(optarg, &invert, &optind, 0);
parse_tcp_ports(argv[optind-1], tcpinfo->spts);
if (invert)
tcpinfo->invflags |= XT_TCP_INV_SRCPT;
*flags |= TCP_SRC_PORTS;
break;
case '2':
if (*flags & TCP_DST_PORTS)
exit_error(PARAMETER_PROBLEM,
"Only one `--destination-port' allowed");
check_inverse(optarg, &invert, &optind, 0);
parse_tcp_ports(argv[optind-1], tcpinfo->dpts);
if (invert)
tcpinfo->invflags |= XT_TCP_INV_DSTPT;
*flags |= TCP_DST_PORTS;
break;
case '3':
if (*flags & TCP_FLAGS)
exit_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)
exit_error(PARAMETER_PROBLEM,
"Only one of `--syn' or `--tcp-flags' "
" allowed");
check_inverse(optarg, &invert, &optind, 0);
if (!argv[optind]
|| argv[optind][0] == '-' || argv[optind][0] == '!')
exit_error(PARAMETER_PROBLEM,
"--tcp-flags requires two args.");
parse_tcp_flags(tcpinfo, argv[optind-1], argv[optind],
invert);
optind++;
*flags |= TCP_FLAGS;
break;
case '5':
if (*flags & TCP_OPTION)
exit_error(PARAMETER_PROBLEM,
"Only one `--tcp-option' allowed");
check_inverse(optarg, &invert, &optind, 0);
parse_tcp_option(argv[optind-1], &tcpinfo->option);
if (invert)
tcpinfo->invflags |= XT_TCP_INV_OPTION;
*flags |= TCP_OPTION;
break;
default:
return 0;
}
return 1;
}
/* Final check; we don't care. */
static void
final_check(unsigned int flags)
{
}
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(" ");
}
}
}
/* Prints out the union ipt_matchinfo. */
static void
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);
}
/* Saves the union ipt_matchinfo in parsable form to stdout. */
static void 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 = {
.family = AF_INET,
.name = "tcp",
.version = IPTABLES_VERSION,
.size = XT_ALIGN(sizeof(struct xt_tcp)),
.userspacesize = XT_ALIGN(sizeof(struct xt_tcp)),
.help = &help,
.init = &init,
.parse = &parse,
.final_check = &final_check,
.print = &print,
.save = &save,
.extra_opts = opts,
};
static struct xtables_match tcp6 = {
.family = AF_INET6,
.name = "tcp",
.version = IPTABLES_VERSION,
.size = XT_ALIGN(sizeof(struct xt_tcp)),
.userspacesize = XT_ALIGN(sizeof(struct xt_tcp)),
.help = &help,
.init = &init,
.parse = &parse,
.final_check = &final_check,
.print = &print,
.save = &save,
.extra_opts = opts,
};
void
_init(void)
{
xtables_register_match(&tcp);
xtables_register_match(&tcp6);
}