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 adds to a PF table <lockout> using 'pfctl -tlockout -Tadd' commands.
41 * /etc/syslog.conf line example:
42 * auth.info;authpriv.info |exec /usr/sbin/sshlockout lockout
44 * Also suggest a cron entry to clean out the PF table at least once a day.
45 * 3 3 * * * pfctl -tlockout -Tflush
48 #include <sys/types.h>
57 typedef struct iphist {
66 #define HMASK (HSIZE - 1)
68 #define SSHLIMIT 5 /* per hour */
69 #define MAX_TABLE_NAME 20 /* PF table name limit */
71 static iphist_t *hist_base;
72 static iphist_t **hist_tail = &hist_base;
73 static iphist_t *hist_hash[HSIZE];
74 static int hist_count = 0;
76 static char *pftable = NULL;
78 static void init_iphist(void);
79 static void checkline(char *buf);
80 static int insert_iph(const char *ips, time_t t);
81 static void delete_iph(iphist_t *ip);
85 block_ip(const char *ips) {
87 int r = snprintf(buf, sizeof(buf),
88 "pfctl -t%s -Tadd %s", pftable, ips);
89 if ((int)strlen(buf) == r) {
93 syslog(LOG_ERR, "sshlockout: command size overflow");
98 * Stupid simple string hash
102 iphash(const char *str)
106 hv = (hv << 5) ^ *str ^ (hv >> 23);
113 main(int ac, char **av)
119 if (ac == 2 && av[1] != NULL &&
120 strlen(av[1]) > 0 && strlen(av[1]) < MAX_TABLE_NAME) {
124 syslog(LOG_ERR, "sshlockout: invalid argument");
128 openlog("sshlockout", LOG_PID|LOG_CONS, LOG_AUTH);
129 syslog(LOG_ERR, "sshlockout starting up");
130 freopen("/dev/null", "w", stdout);
131 freopen("/dev/null", "w", stderr);
133 while (fgets(buf, sizeof(buf), stdin) != NULL) {
134 if (strstr(buf, "sshd") == NULL)
138 syslog(LOG_ERR, "sshlockout exiting");
144 checkip(const char *str, const char *reason1, const char *reason2) {
150 time_t t = time(NULL);
154 if (sscanf(str, "%d.%d.%d.%d", &n1, &n2, &n3, &n4) == 4) {
155 snprintf(ips, sizeof(ips), "%d.%d.%d.%d", n1, n2, n3, n4);
157 // TODO: Check for IPv6 address
159 if (strlen(ips) > 0) {
162 * Check for DoS attack. When connections from too many
163 * IP addresses come in at the same time, our hash table
164 * would overflow, so we delete the oldest entries AND
165 * block it's IP when they are younger than 10 seconds.
166 * This prevents massive attacks from arbitrary IPs.
168 if (hist_count > MAXHIST + 16) {
169 while (hist_count > MAXHIST) {
170 iphist_t *iph = hist_base;
171 int dt = (int)(t - iph->t);
174 "Detected overflow attack, "
183 if (insert_iph(ips, t)) {
185 "Detected ssh %s attempt "
186 "for %s, locking out %s\n",
187 reason1, reason2, ips);
200 * ssh login attempt with password (only hit if ssh allows
201 * password entry). Root or admin.
203 if ((str = strstr(buf, "Failed password for root from")) != NULL ||
204 (str = strstr(buf, "Failed password for admin from")) != NULL) {
205 while (*str && (*str < '0' || *str > '9'))
207 checkip(str, "password login", "root or admin");
212 * ssh login attempt with password (only hit if ssh allows password
213 * entry). Non-existant user.
215 if ((str = strstr(buf, "Failed password for invalid user")) != NULL) {
219 while (*str && *str != ' ')
221 if (strncmp(str, " from", 5) == 0) {
222 checkip(str + 5, "password login", "an invalid user");
228 * ssh login attempt for non-existant user.
230 if ((str = strstr(buf, "Invalid user")) != NULL) {
234 while (*str && *str != ' ')
236 if (strncmp(str, " from", 5) == 0) {
237 checkip(str + 5, "login", "an invalid user");
243 * Premature disconnect in pre-authorization phase, typically an
244 * attack but require 5 attempts in an hour before cleaning it out.
246 if ((str = strstr(buf, "Received disconnect from ")) != NULL &&
247 strstr(buf, "[preauth]") != NULL) {
248 checkip(str + 25, "preauth", "an invalid user");
258 insert_iph(const char *ips, time_t t)
260 iphist_t *ip = malloc(sizeof(*ip));
264 ip->hv = iphash(ips);
265 ip->ips = strdup(ips);
268 ip->hnext = hist_hash[ip->hv & HMASK];
269 hist_hash[ip->hv & HMASK] = ip;
272 hist_tail = &ip->next;
278 if (hist_count > MAXHIST + 16) {
279 while (hist_count > MAXHIST)
280 delete_iph(hist_base);
287 for (scan = hist_hash[ip->hv & HMASK]; scan; scan = scan->hnext) {
288 if (scan->hv == ip->hv && strcmp(scan->ips, ip->ips) == 0) {
289 int dt = (int)(t - ip->t);
292 if (found > SSHLIMIT)
297 return (found > SSHLIMIT);
301 * Delete an ip record. Note that we always delete from the head of the
302 * list, but we will still wind up scanning hash chains.
306 delete_iph(iphist_t *ip)
312 while ((scan = *scanp) != ip) {
316 if (hist_tail == &ip->next)
319 scanp = &hist_hash[ip->hv & HMASK];
320 while ((scan = *scanp) != ip) {
321 scanp = &scan->hnext;
333 hist_tail = &hist_base;
334 for (int i = 0; i < HSIZE; i++) {