2 * Copyright (c) 2015 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@dragonflybsd.org>
6 * by Venkatesh Srinivas <vsrinivas@dragonflybsd.org>
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the
18 * 3. Neither the name of The DragonFly Project nor the names of its
19 * contributors may be used to endorse or promote products derived
20 * from this software without specific, prior written permission.
22 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
23 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
24 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
25 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
26 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
27 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
28 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
29 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
30 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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32 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * Use: pipe syslog auth output to this program.
38 * Detects failed ssh login attempts and maps out the originating IP and
39 * issues, in case of a PF firewall, adds to a PF table <lockout> using
40 * 'pfctl -tlockout -Tadd' commands.
42 * /etc/syslog.conf line example:
43 * auth.info;authpriv.info |exec /usr/sbin/sshlockout -pf lockout
45 * Also suggest a cron entry to clean out the PF table at least once a day.
46 * 3 3 * * * pfctl -tlockout -Tflush
48 * Alternatively there is an ipfw(8) mode (-ipfw <rulenum>).
51 #include <sys/types.h>
62 typedef struct iphist {
80 #define HMASK (HSIZE - 1)
82 #define SSHLIMIT 5 /* per hour */
83 #define MAX_TABLE_NAME 20 /* PF table name limit */
85 static iphist_t *hist_base;
86 static iphist_t **hist_tail = &hist_base;
87 static iphist_t *hist_hash[HSIZE];
88 static int hist_count = 0;
90 static struct args args;
92 static void init_iphist(void);
93 static void checkline(char *buf);
94 static int insert_iph(const char *ips, time_t t);
95 static void delete_iph(iphist_t *ip);
99 block_ip(const char *ips) {
103 switch (args.fw_type) {
105 r = snprintf(buf, sizeof(buf),
106 "pfctl -t%s -Tadd %s", args.arg1, ips);
109 r = snprintf(buf, sizeof(buf),
110 "ipfw add %s deny tcp from %s to me 22",
115 if (r > 0 && (int)strlen(buf) == r) {
119 syslog(LOG_ERR, "sshlockout: invalid command");
124 * Stupid simple string hash
128 iphash(const char *str)
132 hv = (hv << 5) ^ *str ^ (hv >> 23);
140 parse_args(int ac, char **av)
143 if (strcmp(av[1], "-pf") == 0) {
145 char *tablename = av[2];
146 if (ac == 3 && tablename != NULL) {
147 if (strlen(tablename) > 0 &&
148 strlen(tablename) < MAX_TABLE_NAME) {
149 args.fw_type = FW_IS_PF;
150 args.arg1 = tablename;
156 if (strcmp(av[1], "-ipfw") == 0) {
159 if (ac == 3 && rule != NULL) {
160 if (strlen(rule) > 0 && strlen(rule) <= 5) {
161 for (char *s = rule; *s; ++s) {
167 if (atoi(rule) > 65535)
169 args.fw_type = FW_IS_IPFW;
182 main(int ac, char **av)
190 if (!parse_args(ac, av)) {
191 syslog(LOG_ERR, "sshlockout: invalid argument");
197 openlog("sshlockout", LOG_PID|LOG_CONS, LOG_AUTH);
198 syslog(LOG_ERR, "sshlockout starting up");
199 freopen("/dev/null", "w", stdout);
200 freopen("/dev/null", "w", stderr);
202 while (fgets(buf, sizeof(buf), stdin) != NULL) {
203 if (strstr(buf, "sshd") == NULL)
207 syslog(LOG_ERR, "sshlockout exiting");
213 checkip(const char *str, const char *reason1, const char *reason2) {
219 time_t t = time(NULL);
223 if (sscanf(str, "%d.%d.%d.%d", &n1, &n2, &n3, &n4) == 4) {
224 snprintf(ips, sizeof(ips), "%d.%d.%d.%d", n1, n2, n3, n4);
228 * Check for IPv6 address (primitive way)
231 while (str[cnt] == ':' || isxdigit(str[cnt])) {
234 if (cnt > 0 && cnt < (int)sizeof(ips)) {
235 memcpy(ips, str, cnt);
241 * We do not block localhost as is makes no sense.
243 if (strcmp(ips, "127.0.0.1") == 0)
245 if (strcmp(ips, "::1") == 0)
248 if (strlen(ips) > 0) {
251 * Check for DoS attack. When connections from too many
252 * IP addresses come in at the same time, our hash table
253 * would overflow, so we delete the oldest entries AND
254 * block it's IP when they are younger than 10 seconds.
255 * This prevents massive attacks from arbitrary IPs.
257 if (hist_count > MAXHIST + 16) {
258 while (hist_count > MAXHIST) {
259 iphist_t *iph = hist_base;
260 int dt = (int)(t - iph->t);
263 "Detected overflow attack, "
272 if (insert_iph(ips, t)) {
274 "Detected ssh %s attempt "
275 "for %s, locking out %s\n",
276 reason1, reason2, ips);
289 * ssh login attempt with password (only hit if ssh allows
290 * password entry). Root or admin.
292 if ((str = strstr(buf, "Failed password for root from")) != NULL ||
293 (str = strstr(buf, "Failed password for admin from")) != NULL) {
294 while (*str && (*str < '0' || *str > '9'))
296 checkip(str, "password login", "root or admin");
301 * ssh login attempt with password (only hit if ssh allows password
302 * entry). Non-existant user.
304 if ((str = strstr(buf, "Failed password for invalid user")) != NULL) {
308 while (*str && *str != ' ')
310 if (strncmp(str, " from", 5) == 0) {
311 checkip(str + 5, "password login", "an invalid user");
317 * ssh login attempt for non-existant user.
319 if ((str = strstr(buf, "Invalid user")) != NULL) {
323 while (*str && *str != ' ')
325 if (strncmp(str, " from", 5) == 0) {
326 checkip(str + 5, "login", "an invalid user");
332 * Premature disconnect in pre-authorization phase, typically an
333 * attack but require 5 attempts in an hour before cleaning it out.
335 if ((str = strstr(buf, "Received disconnect from ")) != NULL &&
336 strstr(buf, "[preauth]") != NULL) {
337 checkip(str + 25, "preauth", "an invalid user");
347 insert_iph(const char *ips, time_t t)
349 iphist_t *ip = malloc(sizeof(*ip));
353 ip->hv = iphash(ips);
354 ip->ips = strdup(ips);
357 ip->hnext = hist_hash[ip->hv & HMASK];
358 hist_hash[ip->hv & HMASK] = ip;
361 hist_tail = &ip->next;
367 if (hist_count > MAXHIST + 16) {
368 while (hist_count > MAXHIST)
369 delete_iph(hist_base);
376 for (scan = hist_hash[ip->hv & HMASK]; scan; scan = scan->hnext) {
377 if (scan->hv == ip->hv && strcmp(scan->ips, ip->ips) == 0) {
378 int dt = (int)(t - ip->t);
381 if (found > SSHLIMIT)
386 return (found > SSHLIMIT);
390 * Delete an ip record. Note that we always delete from the head of the
391 * list, but we will still wind up scanning hash chains.
395 delete_iph(iphist_t *ip)
401 while ((scan = *scanp) != ip) {
405 if (hist_tail == &ip->next)
408 scanp = &hist_hash[ip->hv & HMASK];
409 while ((scan = *scanp) != ip) {
410 scanp = &scan->hnext;
422 hist_tail = &hist_base;
423 for (int i = 0; i < HSIZE; i++) {