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tallow.c
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tallow.c
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/*
* tallow.c - IP block sshd login abuse
*
* (C) Copyright 2015-2019 Intel Corporation
* Authors:
* Auke Kok <auke-jan.h.kok@intel.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; version 3
* of the License.
*/
#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <stdbool.h>
#include <signal.h>
#include <unistd.h>
#include <limits.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <linux/limits.h>
#include <pcre.h>
#include <systemd/sd-journal.h>
#include "json.h"
#include "data.h"
#define MAX_OFFSETS 30
static char ipt_path[PATH_MAX];
static char fwcmd_path[PATH_MAX];
static int expires = 3600;
static int has_ipv6 = 0;
static bool nocreate = false;
static sd_journal *j;
static int ext(char *fmt, ...)
{
va_list args;
char cmd[1024];
int ret = 0;
va_start(args, fmt);
vsnprintf(cmd, sizeof(cmd), fmt, args);
va_end(args);
ret = system(cmd);
if (ret)
fprintf(stderr, "Error executing \"%s\": returned %d\n", cmd, ret);
return (ret);
}
static void ext_ignore(char *fmt, ...)
{
va_list args;
char cmd[1024];
va_start(args, fmt);
vsnprintf(cmd, sizeof(cmd), fmt, args);
va_end(args);
__attribute__((unused)) int ret = system(cmd);
}
static void reset_rules(void)
{
/* reset all rules in case the running fw changes */
ext_ignore("%s/firewall-cmd --permanent --direct --remove-rule ipv4 filter INPUT 1 -m set --match-set tallow src -j DROP 2> /dev/null", fwcmd_path);
ext_ignore("%s/firewall-cmd --permanent --delete-ipset=tallow 2> /dev/null", fwcmd_path);
/* delete iptables ref to set before the ipset! */
ext_ignore("%s/iptables -t filter -D INPUT -m set --match-set tallow src -j DROP 2> /dev/null", ipt_path);
ext_ignore("%s/ipset destroy tallow 2> /dev/null", ipt_path);
if (has_ipv6) {
ext_ignore("%s/firewall-cmd --permanent --direct --remove-rule ipv6 filter INPUT 1 -m set --match-set tallow6 src -j DROP 2> /dev/null", fwcmd_path);
ext_ignore("%s/firewall-cmd --permanent --delete-ipset=tallow6 2> /dev/null", fwcmd_path);
/* delete iptables ref to set before the ipset! */
ext_ignore("%s/ip6tables -t filter -D INPUT -m set --match-set tallow6 src -j DROP 2> /dev/null", ipt_path);
ext_ignore("%s/ipset destroy tallow6 2> /dev/null", ipt_path);
}
}
static void setup(void)
{
static bool done = false;
if (done)
return;
done = true;
if (nocreate)
return;
/* firewalld */
char *fwd_path;
if (asprintf(&fwd_path, "%s/firewall-cmd", fwcmd_path) < 0) {
exit(EXIT_FAILURE);
}
if ((access(fwd_path, X_OK) == 0) && ext("%s/firewall-cmd --state --quiet", fwcmd_path) == 0) {
fprintf(stdout, "firewalld is running and will be used by tallow.\n");
reset_rules();
/* create ipv4 rule and ipset */
if (ext("%s/firewall-cmd --permanent --quiet --new-ipset=tallow --type=hash:ip --family=inet --option=timeout=%d", fwcmd_path, expires)) {
fprintf(stderr, "Unable to create ipv4 ipset with firewall-cmd.\n");
exit(EXIT_FAILURE);
}
if (ext("%s/firewall-cmd --permanent --direct --quiet --add-rule ipv4 filter INPUT 1 -m set --match-set tallow src -j DROP", fwcmd_path)) {
fprintf(stderr, "Unable to create ipv4 firewalld rule.\n");
exit(EXIT_FAILURE);
}
/* create ipv6 rule and ipset */
if (has_ipv6) {
if (ext("%s/firewall-cmd --permanent --quiet --new-ipset=tallow6 --type=hash:ip --family=inet6 --option=timeout=%d", fwcmd_path, expires)) {
fprintf(stderr, "Unable to create ipv6 ipset with firewall-cmd.\n");
exit(EXIT_FAILURE);
}
if (ext("%s/firewall-cmd --permanent --direct --quiet --add-rule ipv6 filter INPUT 1 -m set --match-set tallow6 src -j DROP ", fwcmd_path)) {
fprintf(stderr, "Unable to create ipv6 firewalld rule.\n");
exit(EXIT_FAILURE);
}
}
/* reload firewalld for ipsets to load */
if (ext("%s/firewall-cmd --reload --quiet", fwcmd_path, expires)) {
fprintf(stderr, "Unable to reload firewalld rules.\n");
exit(EXIT_FAILURE);
}
} else {
/* iptables */
reset_rules();
/* create ipv4 rule and ipset */
if (ext("%s/ipset create tallow hash:ip family inet timeout %d", ipt_path, expires)) {
fprintf(stderr, "Unable to create ipv4 ipset.\n");
exit(EXIT_FAILURE);
}
if (ext("%s/iptables -t filter -A INPUT -m set --match-set tallow src -j DROP", ipt_path)) {
fprintf(stderr, "Unable to create iptables rule.\n");
exit(EXIT_FAILURE);
}
/* create ipv6 rule and ipset */
if (has_ipv6) {
if (ext("%s/ipset create tallow6 hash:ip family inet6 timeout %d", ipt_path, expires)) {
fprintf(stderr, "Unable to create ipv6 ipset.\n");
exit(EXIT_FAILURE);
}
if (ext("%s/ip6tables -t filter -A INPUT -m set --match-set tallow6 src -j DROP", ipt_path)) {
fprintf(stderr, "Unable to create ipt6ables rule.\n");
exit(EXIT_FAILURE);
}
}
}
free(fwd_path);
}
static void block(struct block_struct *s, int instant_block)
{
setup();
if (strchr(s->ip, ':')) {
if (has_ipv6) {
if (instant_block > 0) {
(void) ext("%s/ipset -! add tallow6 %s timeout %d",
ipt_path, s->ip, instant_block);
} else {
(void) ext("%s/ipset -! add tallow6 %s", ipt_path, s->ip);
s->blocked = true;
}
}
} else {
if (instant_block > 0) {
(void) ext("%s/ipset -! add tallow %s timeout %d",
ipt_path, s->ip, instant_block);
} else {
(void) ext("%s/ipset -! add tallow %s", ipt_path, s->ip);
s->blocked = true;
}
}
if (s->blocked) {
fprintf(stderr, "Blocked %s\n", s->ip);
} else {
dbg("Throttled %s\n", s->ip);
}
}
void find(const char *ip, float weight, int instant_block)
{
struct block_struct *s = blocks;
struct block_struct *n;
if (!ip)
return;
/*
* not validating the IP address format here, just
* making sure we're not passing special characters
* to system().
*/
if (strspn(ip, "0123456789abcdef:.") != strlen(ip))
return;
if (whitelist_find(ip))
return;
/* walk and update entry */
while (s) {
if (!strcmp(s->ip, ip)) {
s->score += weight;
dbg("%s: %1.3f\n", s->ip, s->score);
(void) gettimeofday(&s->time, NULL);
if (s->blocked) {
return;
}
if (s->score >= 1.0) {
block(s, 0);
} else if (instant_block > 0) {
block(s, instant_block);
}
return;
}
if (s->next)
s = s->next;
else
break;
}
/* append */
n = calloc(1, sizeof(struct block_struct));
if (!n) {
fprintf(stderr, "Out of memory.\n");
exit(EXIT_FAILURE);
}
if (!blocks)
blocks = n;
else
s->next = n;
n->ip = strdup(ip);
n->score = weight;
n->next = NULL;
n->blocked = false;
(void) gettimeofday(&n->time, NULL);
dbg("%s: %1.3f\n", n->ip, n->score);
if (weight >= 1.0) {
block(n, 0);
} else if (instant_block > 0) {
block(n, instant_block);
}
return;
}
#ifdef DEBUG
static void sigusr1(int u __attribute__ ((unused)))
{
fprintf(stderr, "Dumping score list on request:\n");
struct block_struct *s = blocks;
while (s) {
fprintf(stderr, "%ld %s %1.3f\n", s->time.tv_sec, s->ip, s->score);
s = s->next;
}
}
#endif
int main(void)
{
int r;
FILE *f;
int timeout = 60;
long long unsigned int last_timestamp = 0;
json_load_patterns();
strcpy(ipt_path, "/usr/sbin");
strcpy(fwcmd_path, "/usr/sbin");
#ifdef DEBUG
fprintf(stderr, "Debug output enabled. Send SIGUSR1 to dump internal state table\n");
struct sigaction s;
memset(&s, 0, sizeof(struct sigaction));
s.sa_handler = sigusr1;
sigaction(SIGUSR1, &s, NULL);
#endif
if (access("/proc/sys/net/ipv6", R_OK | X_OK) == 0)
has_ipv6 = 1;
f = fopen(SYSCONFDIR "/tallow.conf", "r");
if (f) {
char buf[256];
char *key;
char *val;
while (fgets(buf, 80, f) != NULL) {
char *c;
c = strchr(buf, '\n');
if (c) *c = 0; /* remove trailing \n */
if (buf[0] == '#')
continue; /* comment line */
key = strtok(buf, "=");
if (!key)
continue;
val = strtok(NULL, "=");
if (!val)
continue;
// todo: filter leading/trailing whitespace
if (!strcmp(key, "ipt_path"))
strncpy(ipt_path, val, PATH_MAX - 1);
if (!strcmp(key, "fwcmd_path"))
strncpy(fwcmd_path, val, PATH_MAX - 1);
if (!strcmp(key, "expires"))
expires = atoi(val);
if (!strcmp(key, "whitelist"))
whitelist_add(val);
if (!strcmp(key, "ipv6"))
has_ipv6 = atoi(val);
if (!strcmp(key, "nocreate"))
nocreate = (atoi(val) == 1);
}
fclose(f);
}
if (!has_ipv6)
fprintf(stdout, "ipv6 support disabled.\n");
if (!whitelist) {
whitelist_add("127.0.0.1");
whitelist_add("192.168.");
whitelist_add("10.");
}
r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY);
if (r < 0) {
fprintf(stderr, "Failed to open journal: %s\n", strerror(-r));
exit(EXIT_FAILURE);
}
/* add all filters */
struct filter_struct *flt = filters;
while (flt) {
sd_journal_add_match(j, flt->filter, 0);
flt = flt->next;
}
/* go to the tail and wait */
r = sd_journal_seek_tail(j);
sd_journal_wait(j, (uint64_t) 0);
dbg("sd_journal_seek_tail() returned %d\n", r);
while (sd_journal_next(j) != 0)
r++;
dbg("Forwarded through %d items in the journal to reach the end\n", r);
fprintf(stderr, PACKAGE_STRING " Started\n");
for (;;) {
const void *d, *dt;
size_t l, dl;
r = sd_journal_wait(j, (uint64_t) timeout * 1000000);
if (r == SD_JOURNAL_INVALIDATE) {
fprintf(stderr, "Journal was rotated, resetting\n");
sd_journal_seek_tail(j);
} else if (r == SD_JOURNAL_NOP) {
dbg("Timeout reached, waiting again\n");
continue;
}
while (sd_journal_next(j) != 0) {
char *m;
/*
* discard messages older than ones we've already seen before
* this happens when the journal rotates - we get replayed events
*/
if (sd_journal_get_data(j, "_SOURCE_REALTIME_TIMESTAMP", &dt, &dl) == 0) {
long long unsigned int lt = atoll(dt + strlen("_SOURCE_REALTIME_TIMESTAMP="));
if (lt > last_timestamp)
last_timestamp = lt;
else if (lt < last_timestamp) {
dbg("Discarding old entry: %llu - %llu\n", lt, last_timestamp);
continue;
}
}
if (sd_journal_get_data(j, "MESSAGE", &d, &l) < 0) {
fprintf(stderr, "Failed to read message field: %s\n", strerror(-r));
break;
}
m = strndup(d, l+1);
m[l] = '\0';
struct pattern_struct *pat = patterns;
while (pat) {
int off[MAX_OFFSETS];
int ret = pcre_exec(pat->re, NULL, m, l, 0, 0, off, MAX_OFFSETS);
if (ret == 2) {
const char *s;
ret = pcre_get_substring(m, off, 2, 1, &s);
if (ret > 0) {
dbg("%s == %s\n", s, pat->pattern);
find(s, pat->weight, pat->instant_block);
pcre_free_substring(s);
}
}
pat = pat->next;
}
free(m);
}
prune(expires);
}
sd_journal_close(j);
exit(EXIT_SUCCESS);
}