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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36 * Use: pipe syslog auth output to this program.
38 * Detects failed ssh login attempts and maps out the originating IP and
39 * issues 'ipfw add' commands adding a lockout for rule 2100.
41 * /etc/syslog.conf line example:
42 * auth.info;authpriv.info |exec /usr/sbin/sshlockout
44 * Also suggest a cron entry to clean out the ipfw list at least once a day.
45 * 3 3 * * * ipfw delete 2100
48 #include <sys/types.h>
57 typedef struct iphist {
66 #define HMASK (HSIZE - 1)
68 #define SSHLIMIT 5 /* per hour */
71 iphist_t **hist_tail = &hist_base;
72 iphist_t *hist_hash[HSIZE];
75 static void checkline(char *buf);
76 static int insert_iph(const char *ips);
77 static void delete_iph(iphist_t *ip);
80 * Stupid simple string hash
84 iphash(const char *str)
88 hv = (hv << 5) ^ *str ^ (hv >> 23);
95 main(int ac __unused, char **av __unused)
99 openlog("sshlockout", LOG_PID|LOG_CONS, LOG_AUTH);
100 syslog(LOG_ERR, "sshlockout starting up");
101 freopen("/dev/null", "w", stdout);
102 freopen("/dev/null", "w", stderr);
104 while (fgets(buf, sizeof(buf), stdin) != NULL) {
105 if (strstr(buf, "sshd") == NULL)
109 syslog(LOG_ERR, "sshlockout exiting");
125 * ssh login attempt with password (only hit if ssh allows
126 * password entry). Root or admin.
128 if ((str = strstr(buf, "Failed password for root from")) != NULL ||
129 (str = strstr(buf, "Failed password for admin from")) != NULL) {
130 while (*str && (*str < '0' || *str > '9'))
132 if (sscanf(str, "%d.%d.%d.%d", &n1, &n2, &n3, &n4) == 4) {
133 snprintf(ips, sizeof(ips), "%d.%d.%d.%d",
135 if (insert_iph(ips)) {
137 "Detected ssh password login attempt "
138 "for root, locking out %s\n",
140 snprintf(buf, sizeof(buf),
141 "ipfw add 2100 deny tcp from "
151 * ssh login attempt with password (only hit if ssh allows password
152 * entry). Non-existant user.
154 if ((str = strstr(buf, "Failed password for invalid user")) != NULL) {
158 while (*str && *str != ' ')
160 if (strncmp(str, " from", 5) == 0 &&
161 sscanf(str + 5, "%d.%d.%d.%d", &n1, &n2, &n3, &n4) == 4) {
162 snprintf(ips, sizeof(ips), "%d.%d.%d.%d",
164 if (insert_iph(ips)) {
166 "Detected ssh password login attempt "
167 "for an invalid user, locking out %s\n",
169 snprintf(buf, sizeof(buf),
170 "ipfw add 2100 deny tcp from "
180 * Premature disconnect in pre-authorization phase, typically an
181 * attack but require 5 attempts in an hour before cleaning it out.
183 if ((str = strstr(buf, "Received disconnect from ")) != NULL &&
184 strstr(buf, "[preauth]") != NULL) {
185 if (sscanf(str + 25, "%d.%d.%d.%d", &n1, &n2, &n3, &n4) == 4) {
186 snprintf(ips, sizeof(ips), "%d.%d.%d.%d",
188 if (insert_iph(ips)) {
190 "Detected ssh password login attempt "
191 "for an invalid user, locking out %s\n",
193 snprintf(buf, sizeof(buf),
194 "ipfw add 2100 deny tcp from "
209 insert_iph(const char *ips)
211 iphist_t *ip = malloc(sizeof(*ip));
213 time_t t = time(NULL);
216 ip->hv = iphash(ips);
217 ip->ips = strdup(ips);
220 ip->hnext = hist_hash[ip->hv & HMASK];
221 hist_hash[ip->hv & HMASK] = ip;
224 hist_tail = &ip->next;
230 if (hist_count > MAXHIST + 16) {
231 while (hist_count > MAXHIST)
232 delete_iph(hist_base);
239 for (scan = hist_hash[ip->hv & HMASK]; scan; scan = scan->hnext) {
240 if (scan->hv == ip->hv && strcmp(scan->ips, ip->ips) == 0) {
241 int dt = (int)(t - ip->t);
244 if (found > SSHLIMIT)
249 return (found > SSHLIMIT);
253 * Delete an ip record. Note that we always delete from the head of the
254 * list, but we will still wind up scanning hash chains.
258 delete_iph(iphist_t *ip)
264 while ((scan = *scanp) != ip) {
268 if (hist_tail == &ip->next)
271 scanp = &hist_hash[ip->hv & HMASK];
272 while ((scan = *scanp) != ip) {
273 scanp = &scan->hnext;