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/* Shared library add-on to iptables to add realm matching support. */
#include <stdbool.h>
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include <getopt.h>
#if defined(__GLIBC__) && __GLIBC__ == 2
#include <net/ethernet.h>
#else
#include <linux/if_ether.h>
#endif
#include <xtables.h>
#include <linux/netfilter_ipv4/ipt_realm.h>
static void realm_help(void)
{
printf(
"realm match options:\n"
"[!] --realm value[/mask]\n"
" Match realm\n");
}
static const struct option realm_opts[] = {
{.name = "realm", .has_arg = true, .val = '1'},
XT_GETOPT_TABLEEND,
};
struct realmname {
int id;
char* name;
int len;
struct realmname* next;
};
/* array of realms from /etc/iproute2/rt_realms */
static struct realmname *realms;
/* 1 if loading failed */
static int rdberr;
static void load_realms(void)
{
const char* rfnm = "/etc/iproute2/rt_realms";
char buf[512];
FILE *fil;
char *cur, *nxt;
int id;
struct realmname *oldnm = NULL, *newnm = NULL;
fil = fopen(rfnm, "r");
if (!fil) {
rdberr = 1;
return;
}
while (fgets(buf, sizeof(buf), fil)) {
cur = buf;
while ((*cur == ' ') || (*cur == '\t'))
cur++;
if ((*cur == '#') || (*cur == '\n') || (*cur == 0))
continue;
/* iproute2 allows hex and dec format */
errno = 0;
id = strtoul(cur, &nxt, strncmp(cur, "0x", 2) ? 10 : 16);
if ((nxt == cur) || errno)
continue;
/* same boundaries as in iproute2 */
if (id < 0 || id > 255)
continue;
cur = nxt;
if (!isspace(*cur))
continue;
while ((*cur == ' ') || (*cur == '\t'))
cur++;
if ((*cur == '#') || (*cur == '\n') || (*cur == 0))
continue;
nxt = cur;
while ((*nxt != 0) && !isspace(*nxt))
nxt++;
if (nxt == cur)
continue;
/* found valid data */
newnm = malloc(sizeof(struct realmname));
if (newnm == NULL) {
perror("libipt_realm: malloc failed");
exit(1);
}
newnm->id = id;
newnm->len = nxt - cur;
newnm->name = malloc(newnm->len + 1);
if (newnm->name == NULL) {
perror("libipt_realm: malloc failed");
exit(1);
}
strncpy(newnm->name, cur, newnm->len);
newnm->name[newnm->len] = 0;
newnm->next = NULL;
if (oldnm)
oldnm->next = newnm;
else
realms = newnm;
oldnm = newnm;
}
fclose(fil);
}
/* get realm id for name, -1 if error/not found */
static int realm_name2id(const char* name)
{
struct realmname* cur;
if ((realms == NULL) && (rdberr == 0))
load_realms();
cur = realms;
if (cur == NULL)
return -1;
while (cur) {
if (!strncmp(name, cur->name, cur->len + 1))
return cur->id;
cur = cur->next;
}
return -1;
}
/* get realm name for id, NULL if error/not found */
static const char *realm_id2name(int id)
{
struct realmname* cur;
if ((realms == NULL) && (rdberr == 0))
load_realms();
cur = realms;
if (cur == NULL)
return NULL;
while (cur) {
if (id == cur->id)
return cur->name;
cur = cur->next;
}
return NULL;
}
static int realm_parse(int c, char **argv, int invert, unsigned int *flags,
const void *entry, struct xt_entry_match **match)
{
struct ipt_realm_info *realminfo = (struct ipt_realm_info *)(*match)->data;
int id;
switch (c) {
char *end;
case '1':
xtables_check_inverse(optarg, &invert, &optind, 0, argv);
end = optarg = optarg;
realminfo->id = strtoul(optarg, &end, 0);
if (end != optarg && (*end == '/' || *end == '\0')) {
if (*end == '/')
realminfo->mask = strtoul(end+1, &end, 0);
else
realminfo->mask = 0xffffffff;
if (*end != '\0' || end == optarg)
xtables_error(PARAMETER_PROBLEM,
"Bad realm value `%s'", optarg);
} else {
id = realm_name2id(optarg);
if (id == -1)
xtables_error(PARAMETER_PROBLEM,
"Realm `%s' not found", optarg);
realminfo->id = id;
realminfo->mask = 0xffffffff;
}
if (invert)
realminfo->invert = 1;
*flags = 1;
break;
default:
return 0;
}
return 1;
}
static void
print_realm(unsigned long id, unsigned long mask, int numeric)
{
const char* name = NULL;
if (mask != 0xffffffff)
printf("0x%lx/0x%lx ", id, mask);
else {
if (numeric == 0)
name = realm_id2name(id);
if (name)
printf("%s ", name);
else
printf("0x%lx ", id);
}
}
static void realm_print(const void *ip, const struct xt_entry_match *match,
int numeric)
{
const struct ipt_realm_info *ri = (const void *)match->data;
if (ri->invert)
printf("! ");
printf("realm ");
print_realm(ri->id, ri->mask, numeric);
}
static void realm_save(const void *ip, const struct xt_entry_match *match)
{
const struct ipt_realm_info *ri = (const void *)match->data;
if (ri->invert)
printf("! ");
printf("--realm ");
print_realm(ri->id, ri->mask, 0);
}
static void realm_check(unsigned int flags)
{
if (!flags)
xtables_error(PARAMETER_PROBLEM,
"realm match: You must specify `--realm'");
}
static struct xtables_match realm_mt_reg = {
.name = "realm",
.version = XTABLES_VERSION,
.family = NFPROTO_IPV4,
.size = XT_ALIGN(sizeof(struct ipt_realm_info)),
.userspacesize = XT_ALIGN(sizeof(struct ipt_realm_info)),
.help = realm_help,
.parse = realm_parse,
.final_check = realm_check,
.print = realm_print,
.save = realm_save,
.extra_opts = realm_opts,
};
void _init(void)
{
xtables_register_match(&realm_mt_reg);
}
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