diff --git a/COPYING b/COPYING new file mode 100644 index 0000000..94a9ed0 --- /dev/null +++ b/COPYING @@ -0,0 +1,674 @@ + GNU GENERAL PUBLIC LICENSE + Version 3, 29 June 2007 + + Copyright (C) 2007 Free Software Foundation, Inc. + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + Preamble + + The GNU General Public License is a free, copyleft license for +software and other kinds of works. + + The licenses for most software and other practical works are designed +to take away your freedom to share and change the works. By contrast, +the GNU General Public License is intended to guarantee your freedom to +share and change all versions of a program--to make sure it remains free +software for all its users. We, the Free Software Foundation, use the +GNU General Public License for most of our software; it applies also to +any other work released this way by its authors. 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If your program is a subroutine library, you +may consider it more useful to permit linking proprietary applications with +the library. If this is what you want to do, use the GNU Lesser General +Public License instead of this License. But first, please read +. diff --git a/Makefile b/Makefile new file mode 100644 index 0000000..789102e --- /dev/null +++ b/Makefile @@ -0,0 +1,26 @@ +CC = g++ +CFLAGS = -O2 -s -D_GNU_SOURCE -Werror -W -Wall -Wextra -ansi -pedantic +LDLIBS = +PREFIX = +BINDIR = $(PREFIX)/usr/sbin + +all: forbidhosts + +forbidhosts: forbidhosts.o + $(CC) $(CFLAGS) $(LDLIBS) forbidhosts.o -o forbidhosts + +forbidhosts.o: forbidhosts.cpp + $(CC) $(CFLAGS) $(DEFS) -c forbidhosts.cpp + +install: + mkdir -p $(BINDIR) + cp forbidhosts $(BINDIR) + @echo "All done!" + +uninstall: + @rm -f $(BINDIR)/foridhosts + @echo "All done!" + +clean: + rm -f forbidhosts *.o + @echo "All done!" diff --git a/files/forbidhosts.conf b/files/forbidhosts.conf new file mode 100644 index 0000000..f46d85c --- /dev/null +++ b/files/forbidhosts.conf @@ -0,0 +1,28 @@ +# SECURE_LOG: the log file that contains sshd logging information +# If you are not sure, `grep "sshd:" /var/log/*`. This option +# defaults to /var/log/auth.log +SECURE_LOG="/var/log/auth.log" + +# HOSTS_DENY: the file which contains restricted host access +# information. On most operating systems, this option should +# defaults to /etc/hosts.deny +HOSTS_DENY="/etc/hosts.deny" + +# BLOCK_ALL_SERVICES: specifies whether all services, or only SSH +# should be blocked in HOSTS_DENY file. Check `man 5 hosts_access` +# for more details +BLOCK_ALL_SERVICES=0 + +# DENY_THRESHOLD: block each host after the number of failed login +# attempts within specified time that has exceeded this value. This +# value applies to both valid and invalid user login attempts +DENY_THRESHOLD=3 + +# DENY_EXPIRATION: block each host after the number of failed login +# attempts within specified time. Once this value has been exceeded +# then the host will not be banned until DENY_THRESHOLD is reached +DENY_EXPIRATION=10 + +# LOCK_FILE: This file will be created upon invocation. This ensures +# that only one instance is running at a time +LOCK_FILE="/var/run/forbidhosts.pid" diff --git a/files/forbidhosts.init b/files/forbidhosts.init new file mode 100644 index 0000000..0404d8b --- /dev/null +++ b/files/forbidhosts.init @@ -0,0 +1,28 @@ +#!/sbin/runscript + +description="ForbidHosts provides SSH attack prevention" + +depend() +{ + use sshd +} + +start() { + ebegin "Starting ForbidHosts" + source /etc/forbidhosts.conf + if [ ${BLOCK_ALL_SERVICES} -eq 1 ]; then + SERVICES="-a" + else + SERVICES="" + fi + /usr/sbin/forbidhosts -l "${SECURE_LOG}" -d "${HOSTS_DENY}" -t "${DENY_THRESHOLD}" -e "${DENY_EXPIRATION}" -p "${LOCK_FILE}" ${SERVICES} + eend $? +} + +stop() { + ebegin "Stopping ForbidHosts" + source /etc/forbidhosts.conf + kill `cat ${LOCK_FILE}` + rm -f ${LOCK_FILE} + eend 0 +} diff --git a/forbidhosts.cpp b/forbidhosts.cpp new file mode 100644 index 0000000..f90a118 --- /dev/null +++ b/forbidhosts.cpp @@ -0,0 +1,475 @@ +/** + * @PROJECT ForbidHosts + * @COPYRIGHT See COPYING in the top level directory + * @FILE forbidhosts.cpp + * @PURPOSE Tool for checking IPv4 & IPv6 failed connections + * @DEVELOPERS Pierre Schweitzer + * Rafal Kupiec + */ + +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include +#include +#include + +#include "forbidhosts.h" + +using namespace std; + +void assertException(const char *file, unsigned int line, const char *assert, bool critical) { + syslog(LOG_ERR, "Assertion '%s' failed at line %d in file %s", assert, line, file); + if(critical) { + shutdown(EXIT_FAILURE); + } +} + +void assignGlobalVars() { + global.max_attempts = MAXATTEMPTS; + global.host_expire = HOSTEXPIRE; + global.failure_penalty = FAILUREPENALTY; + global.deny_file = DENYFILE; + global.log_file = LOGFILE; + global.pid_file = PIDFILE; + global.protocol = "sshd"; +} + +bool compare(const host_t &lhs, const host_t &rhs) { + return (lhs.expires > rhs.expires); +} + +void daemonize(string workdir) { + int pidfile; + char pid[10]; + struct sigaction sigact; + pid_t daemon; + + if(getppid() == 1) { + return; + } + setlogmask(LOG_MASK(LOG_INFO) | LOG_MASK(LOG_ERR) | LOG_MASK(LOG_CRIT)); + openlog("ForbidHosts", LOG_CONS, LOG_USER); + syslog(LOG_INFO, "Starting up daemon."); + daemon = fork(); + if(daemon < 0) { + syslog(LOG_CRIT, "Unable to execute fork()."); + shutdown(EXIT_FAILURE); + } + if(daemon > 0) { + syslog(LOG_INFO, "Child process created, working in background. Parent exiting."); + exit(EXIT_SUCCESS); + } + sigact.sa_handler = &signalHandler; + sigact.sa_flags = SA_RESTART; + sigfillset(&sigact.sa_mask); + sigaction(SIGABRT, &sigact, NULL); + sigaction(SIGHUP, &sigact, NULL); + sigaction(SIGINT, &sigact, NULL); + sigaction(SIGKILL, &sigact, NULL); + sigaction(SIGQUIT, &sigact, NULL); + sigaction(SIGTERM, &sigact, NULL); + sigaction(SIGUSR1, &sigact, NULL); + sigaction(SIGUSR2, &sigact, NULL); + umask(0); + if(setsid() < 0) { + shutdown(EXIT_FAILURE); + } + if((chdir(workdir.c_str())) < 0) { + syslog(LOG_CRIT, "Unable to change working directory to '%s'.", workdir.c_str()); + shutdown(EXIT_FAILURE); + } + close(STDIN_FILENO); + close(STDOUT_FILENO); + close(STDERR_FILENO); + pidfile = open(global.pid_file.c_str(), O_RDWR | O_CREAT, 0600); + if(pidfile == -1) { + syslog(LOG_CRIT, "Unable to open '%s' PID lock file.", global.pid_file.c_str()); + shutdown(EXIT_FAILURE); + } + if(lockf(pidfile, F_TLOCK,0) == -1) { + syslog(LOG_CRIT, "Unable to lock '%s' PID lock file.", global.pid_file.c_str()); + shutdown(EXIT_FAILURE); + } + sprintf(pid, "%d\n", getpid()); + assertSoft(write(pidfile, pid, strlen(pid)) == (ssize_t) strlen(pid)); + close(pidfile); + syslog(LOG_INFO, "Daemon is UP & RUNNING."); +} + +void debug(const char *msg, ...) { + int fp; + char *log = NULL; + va_list args; + + if(global.debug.length()) { + if((fp = open(global.debug.c_str(), O_WRONLY | O_APPEND))) { + va_start(args, msg); + sprintf(log, msg, args); + va_end(args); + assertSoft(write(fp, log, strlen(log)) == (ssize_t) strlen(log)); + close(fp); + sync(); + } + } +} + +void denyHost(string host) { + int colon; + int deny; + string entry; + + deny = open(global.deny_file.c_str(), O_WRONLY | O_APPEND); + if(deny < 0) { + debug("Banning host '%s' in file %s failed for unknown reason.", host.c_str(), global.deny_file.c_str()); + syslog(LOG_ERR, "Banning host '%s' in file %s failed for unknown reason.", host.c_str(), global.deny_file.c_str()); + shutdown(EXIT_FAILURE); + } + colon = host.find_first_of(':'); + if(colon != -1) { + entry = global.protocol + ": [" + host + "]\n"; + } else { + entry = global.protocol + ": " + host + "\n"; + } + assertSoft(write(deny, entry.c_str(), entry.length()) == (ssize_t) entry.length()); + close(deny); + sync(); + debug("Banned host '%s' for excessive abusive.", host.c_str()); + syslog(LOG_INFO, "Banned host '%s' for excessive abusive.", host.c_str()); +} + +int main(int argc, char *argv[]) { + int i_auth; + int i_notify; + int next_opt; + int val; + vector banned; + vector hosts; + + assignGlobalVars(); + while((next_opt = getopt(argc, argv, "t:p:n:l:e:d:D:av")) != -1) { + switch(next_opt) { + case 'a': + global.protocol = "ALL"; + break; + case 'd': + global.deny_file = strdup(optarg); + break; + case 'D': + global.debug = strdup(optarg); + break; + case 'e': + val = sscanf(optarg, "%u", &global.host_expire); + if(val > 0) { + global.host_expire = global.host_expire > 0 ? global.host_expire : HOSTEXPIRE; + } else { + global.host_expire = HOSTEXPIRE; + } + break; + case 'l': + global.log_file = strdup(optarg); + break; + case 'n': + global.banned_names = strdup(optarg); + break; + case 'p': + global.pid_file = strdup(optarg); + break; + case 't': + val = sscanf(optarg, "%u", &global.max_attempts); + if(val > 0) { + global.max_attempts = global.max_attempts > 0 ? global.max_attempts : MAXATTEMPTS; + } else { + global.max_attempts = MAXATTEMPTS; + } + break; + case 'v': + printVersion(); + break; + } + } + daemonize("/tmp"); + logfile = open(global.log_file.c_str(), O_RDONLY | O_NONBLOCK); + if(logfile < 0) { + syslog(LOG_CRIT, "Unable to open '%s' log file for reading.", global.log_file.c_str()); + shutdown(EXIT_FAILURE); + } + lseek(logfile, 0, SEEK_END); + i_notify = inotify_init1(IN_NONBLOCK); + if(i_notify < 0) { + close(logfile); + syslog(LOG_CRIT, "Unable to initialize iNotify subsystem."); + shutdown(EXIT_FAILURE); + } + i_auth = inotify_add_watch(i_notify, global.log_file.c_str(), IN_MODIFY); + if(i_auth < 0) { + close(i_notify); + close(logfile); + syslog(LOG_CRIT, "Unable to attach a watcher on a log file."); + shutdown(EXIT_FAILURE); + } + for(;;) { + struct pollfd fds[] = {i_notify, POLLIN, 0}; + int timeout = -1; + if(!hosts.empty()) { + timeout = hosts.back().expires - time(0) * 1000; + } + int event = poll(fds, 1, timeout); + if(event > 0) { + struct inotify_event i_event; + assertSoft(read(i_notify, &i_event, sizeof(struct inotify_event)) == sizeof(struct inotify_event)); + } + while(!readLine(logfile, hosts, banned)); + while(!banned.empty()) { + if(banned.back().expires > time(0)) { + break; + } + banned.pop_back(); + } + while(!hosts.empty()) { + if(hosts.back().expires > time(0)) { + break; + } + hosts.pop_back(); + } + sleep(1); + } + close(i_auth); + close(i_notify); + close(logfile); +} + +void printVersion() { + printf("ForbidHosts Daemon v%s\n\n", FHVERSION); + exit(EXIT_SUCCESS); +} + +unsigned int readLine(int file, vector &hosts, vector &banned) { + char line[255]; + char *address; + string host; + bool loggedin = false; + static string last_addr = ""; + unsigned int length; + unsigned int addr_length; + unsigned int red = 0; + unsigned int repeated = 1; + + for(;;) { + red = 0; + while(red < sizeof(line) / sizeof(char)) { + length = read(file, &line[red], sizeof(char)); + if(length < 1) { + if(red == 0) { + return length; + } else { + break; + } + } + if(line[red] == '\n') { + line[red] = '\0'; + break; + } + red++; + } + if(!validateEntry(line, &address, &addr_length, &loggedin)) { + if(!last_addr.empty()) { + repeated = validateRepeated(line); + if(repeated == 0) { + last_addr = ""; + return length; + } + } else { + last_addr = ""; + return length; + } + } else { + host = address; + host.erase(addr_length); + last_addr = host; + } + if(updateHost(last_addr, hosts, banned, repeated, loggedin)) { + hosts.push_back(host_t(time(0), host)); + } + sort(hosts.begin(), hosts.end(), compare); + } +} + +void shutdown(int code) { + if(code != 0) { + syslog(LOG_CRIT, "Emergency daemon shutdown due to errors."); + } else { + syslog(LOG_INFO, "Shutting down daemon."); + } + unlink(global.pid_file.c_str()); + exit(code); +} + +void signalHandler(int signal) { + switch(signal) { + case SIGHUP: + syslog(LOG_WARNING, "Received SIGHUP signal!"); + break; + case SIGABRT: + case SIGINT: + case SIGQUIT: + case SIGTERM: + shutdown(EXIT_SUCCESS); + break; + case SIGUSR1: + case SIGUSR2: + syslog(LOG_INFO, "Received SIGUSR1 signal - probably logs rotated."); + syslog(LOG_INFO, "Reloading system log file."); + lseek(logfile, 0, SEEK_END); + break; + default: + syslog(LOG_WARNING, "Unhandled signal caught: %s.", strsignal(signal)); + return; + } +} + +bool updateHost(const string &host, vector &hosts, vector &banned, unsigned int repeated, bool loggedin) { + bool insert = true; + + assertSoft(!banned.empty()); + for(vector::iterator it = banned.begin(); it != banned.end(); ++it) { + if((*it).ipaddr.compare(host) == 0) { + insert = false; + break; + } + } + if(insert) { + assertSoft(!host.empty()); + for(vector::iterator it = hosts.begin(); it != hosts.end(); ++it) { + if((*it).ipaddr.compare(host) == 0) { + insert = false; + (*it).attempts += repeated; + if(loggedin) { + hosts.erase(it); + } else if((*it).attempts >= global.max_attempts) { + denyHost((*it).ipaddr); + hosts.erase(it); + banned.push_back(banned_t(time(0), host)); + } else { + (*it).expires += (global.host_expire * 60); + } + break; + } + } + } + assertSoft((insert && repeated == 1) || !insert); + return (loggedin ? false : insert); +} + +bool validateEntry(char *entry, char **address, unsigned int *length, bool *loggedin) { + char *sshd; + char *method; + char *user; + char *host; + char *end; + + *loggedin = false; + sshd = strstr(entry, " sshd["); + if(sshd != 0) { + method = strstr(sshd, ": Failed "); + if(method != 0) { + method += sizeof(": Failed "); + user = strstr(method, " for "); + if(user == 0) { + return false; + } + user += sizeof(" for "); + host = strstr(user, " from "); + if(host == 0) { + return false; + } + host += sizeof(" from ") - sizeof('\0'); + end = strstr(host, " port "); + if(end == 0) { + return false; + } + } else { + method = strstr(sshd, ": Invalid "); + if(method != 0) { + user = strstr(method, " user "); + if(user == 0) { + return false; + } + user += sizeof (" user "); + host = strstr(user, " from "); + if(host == 0) { + return false; + } + host += sizeof(" from ") - sizeof('\0'); + end = strchr(host, '\0'); + } else { + method = strstr(sshd, ": Address "); + if(method != 0) { + host = strdup(method); + host += sizeof(": Address ") - sizeof('\0'); + user = strstr(host, " POSSIBLE BREAK-IN ATTEMPT"); + if(user == 0) { + return false; + } + end = strstr(host, " maps to "); + if(end == 0) { + return false; + } + } else { + method = strstr(sshd, ": Accepted "); + if(method != 0) { + user = strstr(method, " for "); + if(user == 0) { + return false; + } + user += sizeof(" for "); + host = strstr(user, " from "); + if(host == 0) { + return false; + } + host += sizeof(" from ") - sizeof('\0'); + end = strchr(host, '\0'); + *loggedin = true; + } else { + return false; + } + } + } + } + } else { + return false; + } + *address = host; + *length = (end - host); + return true; +} + +unsigned int validateRepeated(char *line) { + char *sshd; + char *times; + char *end; + + sshd = strstr(line, " sshd["); + if(sshd == 0) { + return 0; + } + times = strstr(sshd, ": last message repeated "); + if(times == 0) { + return 0; + } + times += sizeof(": last message repeated ") - sizeof('\0'); + end = strstr(times, " times"); + if(end == 0) { + return 0; + } + return strtoul(times, 0, 10); +} diff --git a/forbidhosts.h b/forbidhosts.h new file mode 100644 index 0000000..daa2692 --- /dev/null +++ b/forbidhosts.h @@ -0,0 +1,75 @@ +/** + * @PROJECT ForbidHosts + * @COPYRIGHT See COPYING in the top level directory + * @FILE forbidhosts.h + * @PURPOSE Tool for checking IPv4 & IPv6 failed connections + * @DEVELOPERS Pierre Schweitzer + * Rafal Kupiec + */ + +#define MAXATTEMPTS 5 +#define HOSTEXPIRE 10 +#define FAILUREPENALTY 1 +#define DENYFILE "/etc/hosts.deny" +#define LOGFILE "/var/log/auth.log" +#define PIDFILE "/var/run/forbidhosts.pid" + +#define FHVERSION "1.6" + +#define assertHard(e) if (!(e)) assertException(__FILE__, __LINE__, #e, true) +#define assertSoft(e) if (!(e)) assertException(__FILE__, __LINE__, #e, false) + +using namespace std; + +struct hf_t { + unsigned int max_attempts; + unsigned int host_expire; + unsigned int failure_penalty; + string banned_names; + string debug; + string deny_file; + string log_file; + string pid_file; + string protocol; +}; +hf_t global; + +struct banned_t { + string ipaddr; + time_t expires; + + banned_t(time_t date, const string &address) { + ipaddr = address; + expires = date + 12 * 60 * 60; + } +}; + +struct host_t { + string ipaddr; + unsigned int attempts; + time_t first_seen; + time_t expires; + + host_t(time_t date, const string &address) { + attempts = 1; + ipaddr = address; + first_seen = date; + expires = date + global.host_expire * 60; + } +}; + +int logfile; + +void assertException(const char *file, unsigned int line, const char *assert, bool critical); +void assignGlobalVars(); +bool compare(const host_t &lhs, const host_t &rhs); +void daemonize(string workdir); +void debug(const char *msg, ...); +void denyHost(string host); +void printVersion(); +unsigned int readLine(int file, vector &hosts, vector &banned); +void shutdown(int code); +void signalHandler(int signal); +bool updateHost(const string &host, vector &hosts, vector &banned, unsigned int repeated, bool loggedin); +bool validateEntry(char *entry, char **address, unsigned int *length, bool *loggedin); +unsigned int validateRepeated(char *line);