Mark file local statistics struct static (#63)

Debian uses CPPFLAGS to pass arguments like -D_FORTIFY_SOURCE=2.

Makefile

@@ -1,6 +1,7 @@
 .POSIX:
 CC       = cc
 CFLAGS   = -std=c99 -Wall -Wextra -Wno-missing-field-initializers -Os
+CPPFLAGS =
 LDFLAGS  = -ggdb3
 LDLIBS   =
 PREFIX   = /usr/local
@@ -8,7 +9,7 @@ PREFIX  = /usr/local
 all: endlessh
 
 endlessh: endlessh.c
-	$(CC) $(LDFLAGS) $(CFLAGS) -o $@ endlessh.c $(LDLIBS)
+	$(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) -o $@ endlessh.c $(LDLIBS)
 
 install: endlessh
 	install -d $(DESTDIR)$(PREFIX)/bin

README.md

@@ -11,14 +11,12 @@ occurs, this program doesn't depend on any cryptographic libraries. It's
 a simple, single-threaded, standalone C program. It uses `poll()` to
 trap multiple clients at a time.
 
-
-
 ## Usage
 
 Usage information is printed with `-h`.
 
 ```
-Usage: endlessh [-vh] [-d MS] [-f CONFIG] [-l LEN] [-m LIMIT] [-p PORT]
+Usage: endlessh [-vhs] [-d MS] [-f CONFIG] [-l LEN] [-m LIMIT] [-p PORT]
   -4        Bind to IPv4 only
   -6        Bind to IPv6 only
   -d INT    Message millisecond delay [10000]
@@ -27,7 +25,8 @@ Usage: endlessh [-vh] [-d MS] [-f CONFIG] [-l LEN] [-m LIMIT] [-p PORT]
   -l INT    Maximum banner line length (3-255) [32]
   -m INT    Maximum number of clients [4096]
   -p INT    Listening port [2222]
-  -v        Print diagnostics to standard output (repeatable)
+  -s        Print diagnostics to syslog instead of standard output
+  -v        Print diagnostics (repeatable)
 ```
 
 Argument order matters. The configuration file is loaded when the `-f`
@@ -36,7 +35,8 @@ configuration file.
 
 By default no log messages are produced. The first `-v` enables basic
 logging and a second `-v` enables debugging logging (noisy). All log
-messages are sent to standard output.
+messages are sent to standard output by default. `-s` causes them to be
+sent to syslog.
 
     endlessh -v >endlessh.log 2>endlessh.err
 
@@ -108,5 +108,26 @@ to remove GCC-specific options. For example, on Solaris:
 The feature test macros on these systems isn't reliable, so you may also
 need to use `-D__EXTENSIONS__` in `CFLAGS`.
 
+### OpenBSD
+
+The man page needs to go into a different path for OpenBSD's `man` command:
+
+```
+diff --git a/Makefile b/Makefile
+index 119347a..dedf69d 100644
+--- a/Makefile
++++ b/Makefile
+@@ -14,8 +14,8 @@ endlessh: endlessh.c
+ install: endlessh
+        install -d $(DESTDIR)$(PREFIX)/bin
+        install -m 755 endlessh $(DESTDIR)$(PREFIX)/bin/
+-       install -d $(DESTDIR)$(PREFIX)/share/man/man1
+-       install -m 644 endlessh.1 $(DESTDIR)$(PREFIX)/share/man/man1/
++       install -d $(DESTDIR)$(PREFIX)/man/man1
++       install -m 644 endlessh.1 $(DESTDIR)$(PREFIX)/man/man1/
+
+ clean:
+        rm -rf endlessh
+```
 
 [np]: https://nullprogram.com/blog/2019/03/22/

endlessh.1

@@ -1,4 +1,4 @@
-.Dd $Mdocdate: April 12 2019 $
+.Dd $Mdocdate: January 29 2020 $
 .Dt ENDLESSH 1
 .Os
 .Sh NAME
@@ -6,7 +6,7 @@
 .Nd An SSH tarpit
 .Sh SYNOPSIS
 .Nm endless
-.Op Fl 46chvV
+.Op Fl 46chsvV
 .Op Fl d Ar delay
 .Op Fl f Ar config
 .Op Fl l Ar max banner length
@@ -55,15 +55,17 @@ Maximum number of clients. Default: 4096
 Set the listening port. By default
 .Nm
 listens on port 2222.
+.It Fl s
+Print diagnostics to syslog. By default
+.Nm
+prints them to standard output.
 .It Fl v
-Print diagnostics to standard output. Can be specified
+Print diagnostics. Can be specified up to twice to increase verbosity.
-numerous times to increase verbosity.
 .It Fl V
 Causes
 .Nm
 to print version information and exit.
 .El
-.El
 .Pp
 If
 .Nm
@@ -79,3 +81,4 @@ A SIGUSR1 signal will print connections stats to the log.
 The default
 .Nm
 configuration file.
+.El

endlessh.c

@@ -1,4 +1,13 @@
-#define _XOPEN_SOURCE 600
+/* Endlessh: an SSH tarpit
+ *
+ * This is free and unencumbered software released into the public domain.
+ */
+#if defined(__OpenBSD__)
+#  define _BSD_SOURCE  /* for pledge(2) and unveil(2) */
+#else
+#  define _XOPEN_SOURCE 600
+#endif
+
 #include <time.h>
 #include <errno.h>
 #include <stdio.h>
@@ -15,14 +24,21 @@
 #include <sys/socket.h>
 #include <arpa/inet.h>
 #include <netinet/in.h>
+#include <syslog.h>
 
-#define ENDLESSH_VERSION           1.0
+#define ENDLESSH_VERSION           1.1
 
 #define DEFAULT_PORT              2222
 #define DEFAULT_DELAY            10000  /* milliseconds */
 #define DEFAULT_MAX_LINE_LENGTH     32
 #define DEFAULT_MAX_CLIENTS       4096
-#define DEFAULT_CONFIG_FILE      "/etc/endlessh/config"
+
+#if defined(__FreeBSD__)
+#  define DEFAULT_CONFIG_FILE "/usr/local/etc/endlessh.config"
+#else
+#  define DEFAULT_CONFIG_FILE "/etc/endlessh/config"
+#endif
+
 #define DEFAULT_BIND_FAMILY  AF_UNSPEC
 
 #define XSTR(s) STR(s)
@@ -37,13 +53,15 @@ epochms(void)
 }
 
 static enum loglevel {
-    LOG_NONE,
+    log_none,
-    LOG_INFO,
+    log_info,
-    LOG_DEBUG
+    log_debug
-} loglevel = LOG_NONE;
+} loglevel = log_none;
+
+static void (*logmsg)(enum loglevel level, const char *, ...);
 
 static void
-logmsg(enum loglevel level, const char *format, ...)
+logstdio(enum loglevel level, const char *format, ...)
 {
     if (loglevel >= level) {
         int save = errno;
@@ -67,7 +85,27 @@ logmsg(enum loglevel level, const char *format, ...)
     }
 }
 
-struct {
+static void
+logsyslog(enum loglevel level, const char *format, ...)
+{
+    static const int prio_map[] = { LOG_NOTICE, LOG_INFO, LOG_DEBUG };
+
+    if (loglevel >= level) {
+        int save = errno;
+
+        /* Output the log message */
+        va_list ap;
+        va_start(ap, format);
+        char buf[256];
+        vsnprintf(buf, sizeof buf, format, ap);
+        va_end(ap);
+        syslog(prio_map[level], "%s", buf);
+
+        errno = save;
+    }
+}
+
+static struct {
     long long connects;
     long long milliseconds;
     long long bytes_sent;
@@ -101,9 +139,9 @@ client_new(int fd, long long send_next)
          */
         int value = 1;
         int r = setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &value, sizeof(value));
-        logmsg(LOG_DEBUG, "setsockopt(%d, SO_RCVBUF, %d) = %d", fd, value, r);
+        logmsg(log_debug, "setsockopt(%d, SO_RCVBUF, %d) = %d", fd, value, r);
         if (r == -1)
-            logmsg(LOG_DEBUG, "errno = %d, %s", errno, strerror(errno));
+            logmsg(log_debug, "errno = %d, %s", errno, strerror(errno));
 
         /* Get IP address */
         struct sockaddr_storage addr;
@@ -128,9 +166,9 @@ client_new(int fd, long long send_next)
 static void
 client_destroy(struct client *client)
 {
-    logmsg(LOG_DEBUG, "close(%d)", client->fd);
+    logmsg(log_debug, "close(%d)", client->fd);
     long long dt = epochms() - client->connect_time;
-    logmsg(LOG_INFO,
+    logmsg(log_info,
             "CLOSE host=%s port=%d fd=%d "
             "time=%lld.%03lld bytes=%lld",
             client->ipaddr, client->port, client->fd,
@@ -147,7 +185,7 @@ statistics_log_totals(struct client *clients)
     long long milliseconds = statistics.milliseconds;
     for (long long now = epochms(); clients; clients = clients->next)
         milliseconds += now - clients->connect_time;
-    logmsg(LOG_INFO, "TOTALS connects=%lld seconds=%lld.%03lld bytes=%lld",
+    logmsg(log_info, "TOTALS connects=%lld seconds=%lld.%03lld bytes=%lld",
            statistics.connects,
            milliseconds / 1000,
            milliseconds % 1000,
@@ -447,7 +485,7 @@ config_load(struct config *c, const char *file, int hardfail)
                     errno = 0;
                     char *end;
                     long v = strtol(tokens[1], &end, 10);
-                    if (errno || *end || v < LOG_NONE || v > LOG_DEBUG) {
+                    if (errno || *end || v < log_none || v > log_debug) {
                         fprintf(stderr, "%s:%ld: Invalid log level '%s'\n",
                                 file, lineno, tokens[1]);
                         if (hardfail) exit(EXIT_FAILURE);
@@ -465,11 +503,11 @@ config_load(struct config *c, const char *file, int hardfail)
 static void
 config_log(const struct config *c)
 {
-    logmsg(LOG_INFO, "Port %d", c->port);
+    logmsg(log_info, "Port %d", c->port);
-    logmsg(LOG_INFO, "Delay %ld", c->delay);
+    logmsg(log_info, "Delay %d", c->delay);
-    logmsg(LOG_INFO, "MaxLineLength %d", c->max_line_length);
+    logmsg(log_info, "MaxLineLength %d", c->max_line_length);
-    logmsg(LOG_INFO, "MaxClients %d", c->max_clients);
+    logmsg(log_info, "MaxClients %d", c->max_clients);
-    logmsg(LOG_INFO, "BindFamily %s",
+    logmsg(log_info, "BindFamily %s",
         c->bind_family == AF_INET6 ? "IPv6 Only" :
         c->bind_family == AF_INET  ? "IPv4 Only" :
                                 "IPv4 Mapped IPv6");
@@ -509,15 +547,15 @@ server_create(int port, int family)
     int r, s, value;
 
     s = socket(family == AF_UNSPEC ? AF_INET6 : family, SOCK_STREAM, 0);
-    logmsg(LOG_DEBUG, "socket() = %d", s);
+    logmsg(log_debug, "socket() = %d", s);
     if (s == -1) die();
 
     /* Socket options are best effort, allowed to fail */
     value = 1;
     r = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &value, sizeof(value));
-    logmsg(LOG_DEBUG, "setsockopt(%d, SO_REUSEADDR, true) = %d", s, r);
+    logmsg(log_debug, "setsockopt(%d, SO_REUSEADDR, true) = %d", s, r);
     if (r == -1)
-        logmsg(LOG_DEBUG, "errno = %d, %s", errno, strerror(errno));
+        logmsg(log_debug, "errno = %d, %s", errno, strerror(errno));
 
     /*
      * With OpenBSD IPv6 sockets are always IPv6-only, so the socket option
@@ -529,9 +567,9 @@ server_create(int port, int family)
         errno = 0;
         value = (family == AF_INET6);
         r = setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &value, sizeof(value));
-        logmsg(LOG_DEBUG, "setsockopt(%d, IPV6_V6ONLY, true) = %d", s, r);
+        logmsg(log_debug, "setsockopt(%d, IPV6_V6ONLY, true) = %d", s, r);
         if (r == -1)
-            logmsg(LOG_DEBUG, "errno = %d, %s", errno, strerror(errno));
+            logmsg(log_debug, "errno = %d, %s", errno, strerror(errno));
     }
 #endif
 
@@ -550,11 +588,11 @@ server_create(int port, int family)
         };
         r = bind(s, (void *)&addr6, sizeof(addr6));
     }
-    logmsg(LOG_DEBUG, "bind(%d, port=%d) = %d", s, port, r);
+    logmsg(log_debug, "bind(%d, port=%d) = %d", s, port, r);
     if (r == -1) die();
 
     r = listen(s, INT_MAX);
-    logmsg(LOG_DEBUG, "listen(%d) = %d", s, r);
+    logmsg(log_debug, "listen(%d) = %d", s, r);
     if (r == -1) die();
 
     return s;
@@ -568,7 +606,7 @@ sendline(struct client *client, int max_line_length, unsigned long *rng)
     int len = randline(line, max_line_length, rng);
     for (;;) {
         ssize_t out = write(client->fd, line, len);
-        logmsg(LOG_DEBUG, "write(%d) = %d", client->fd, (int)out);
+        logmsg(log_debug, "write(%d) = %d", client->fd, (int)out);
         if (out == -1) {
             if (errno == EINTR) {
                 continue;      /* try again */
@@ -590,12 +628,20 @@ sendline(struct client *client, int max_line_length, unsigned long *rng)
 int
 main(int argc, char **argv)
 {
+    logmsg = logstdio;
     struct config config = CONFIG_DEFAULT;
     const char *config_file = DEFAULT_CONFIG_FILE;
+
+#if defined(__OpenBSD__)
+    unveil(config_file, "r"); /* return ignored as the file may not exist */
+    if (pledge("inet stdio rpath unveil", 0) == -1)
+        die();
+#endif
+
     config_load(&config, config_file, 1);
 
     int option;
-    while ((option = getopt(argc, argv, "46d:f:hl:m:p:vV")) != -1) {
+    while ((option = getopt(argc, argv, "46d:f:hl:m:p:svV")) != -1) {
         switch (option) {
             case '4':
                 config_set_bind_family(&config, "4", 1);
@@ -608,6 +654,13 @@ main(int argc, char **argv)
                 break;
             case 'f':
                 config_file = optarg;
+
+#if defined(__OpenBSD__)
+                unveil(config_file, "r");
+                if (unveil(0, 0) == -1)
+                    die();
+#endif
+
                 config_load(&config, optarg, 1);
                 break;
             case 'h':
@@ -623,7 +676,11 @@ main(int argc, char **argv)
             case 'p':
                 config_set_port(&config, optarg, 1);
                 break;
+            case 's':
+                logmsg = logsyslog;
+                break;
             case 'v':
+                if (loglevel < log_debug)
                     loglevel++;
                 break;
             case 'V':
@@ -641,8 +698,15 @@ main(int argc, char **argv)
         exit(EXIT_FAILURE);
     }
 
+    if (logmsg == logsyslog) {
+        /* Prepare the syslog */
+        const char *prog = strrchr(argv[0], '/');
+        prog = prog ? prog + 1 : argv[0];
+        openlog(prog, LOG_PID, LOG_DAEMON);
+    } else {
         /* Set output (log) to line buffered */
         setvbuf(stdout, 0, _IOLBF, 0);
+    }
 
     /* Log configuration */
     config_log(&config);
@@ -713,13 +777,13 @@ main(int argc, char **argv)
         /* Wait for next event */
         struct pollfd fds = {server, POLLIN, 0};
         int nfds = fifo->length < config.max_clients;
-        logmsg(LOG_DEBUG, "poll(%d, %d)", nfds, timeout);
+        logmsg(log_debug, "poll(%d, %d)", nfds, timeout);
         int r = poll(&fds, nfds, timeout);
-        logmsg(LOG_DEBUG, "= %d", r);
+        logmsg(log_debug, "= %d", r);
         if (r == -1) {
             switch (errno) {
                 case EINTR:
-                    logmsg(LOG_DEBUG, "EINTR");
+                    logmsg(log_debug, "EINTR");
                     continue;
                 default:
                     fprintf(stderr, "endlessh: fatal: %s\n", strerror(errno));
@@ -730,7 +794,7 @@ main(int argc, char **argv)
         /* Check for new incoming connections */
         if (fds.revents & POLLIN) {
             int fd = accept(server, 0, 0);
-            logmsg(LOG_DEBUG, "accept() = %d", fd);
+            logmsg(log_debug, "accept() = %d", fd);
             statistics.connects++;
             if (fd == -1) {
                 const char *msg = strerror(errno);
@@ -738,7 +802,7 @@ main(int argc, char **argv)
                     case EMFILE:
                     case ENFILE:
                         config.max_clients = fifo->length;
-                        logmsg(LOG_INFO,
+                        logmsg(log_info,
                                 "MaxClients %d",
                                 fifo->length);
                         break;
@@ -761,15 +825,19 @@ main(int argc, char **argv)
                 if (!client) {
                     fprintf(stderr, "endlessh: warning: out of memory\n");
                     close(fd);
-                }
+                } else {
                     fifo_append(fifo, client);
-                logmsg(LOG_INFO, "ACCEPT host=%s port=%d fd=%d n=%d/%d",
+                    logmsg(log_info, "ACCEPT host=%s port=%d fd=%d n=%d/%d",
                             client->ipaddr, client->port, client->fd,
                             fifo->length, config.max_clients);
                 }
             }
         }
+    }
 
     fifo_destroy(fifo);
     statistics_log_totals(0);
+
+    if (logmsg == logsyslog)
+        closelog();
 }

util/endlessh.service

@@ -1,12 +1,13 @@
 [Unit]
 Description=Endlessh SSH Tarpit
+Documentation=man:endlessh(1)
 Requires=network-online.target
 
 [Service]
 Type=simple
 Restart=always
 RestartSec=30sec
-ExecStart=/opt/endlessh/endlessh
+ExecStart=/usr/local/bin/endlessh
 KillSignal=SIGTERM
 
 # Stop trying to restart the service if it restarts too many times in a row
@@ -21,9 +22,18 @@ PrivateTmp=true
 PrivateDevices=true
 ProtectSystem=full
 ProtectHome=true
-NoNewPrivileges=true
+InaccessiblePaths=/run /var
-ConfigurationDirectory=/etc/endlessh
+
+## If you want Endlessh to bind on ports < 1024
+## 1) run: 
+##     setcap 'cap_net_bind_service=+ep' /usr/local/bin/endlessh
+## 2) uncomment following line
+#AmbientCapabilities=CAP_NET_BIND_SERVICE
+## 3) comment following line
 PrivateUsers=true
+
+NoNewPrivileges=true
+ConfigurationDirectory=endlessh
 ProtectKernelTunables=true
 ProtectKernelModules=true
 ProtectControlGroups=true
@@ -31,3 +41,4 @@ MemoryDenyWriteExecute=true
 
 [Install]
 WantedBy=multi-user.target
+

util/openbsd/README.md

@@ -0,0 +1,34 @@
+# Running `endlessh` on OpenBSD
+
+## Covering IPv4 and IPv6
+
+If you want to cover both IPv4 and IPv6 you'll need to run *two* instances of
+`endlessh` due to OpenBSD limitations. Here's how I did it:
+
+- copy the `endlessh` script to `rc.d` twice, as `endlessh` and `endlessh6`
+- copy the `config` file to `/etc/endlessh` twice, as `config` and `config6`
+  - use `BindFamily 4` in `config`
+  - use `BindFamily 6` in `config6`
+- in `rc.conf.local` force `endlessh6` to load `config6` like so:
+
+```
+endlessh6_flags=-s -f /etc/endlessh/config6
+endlessh_flags=-s
+```
+
+## Covering more than 128 connections
+
+The defaults in OpenBSD only allow for 128 open file descriptors per process,
+so regardless of the `MaxClients` setting in `/etc/config` you'll end up with
+something like 124 clients at the most.
+You can increase these limits in `/etc/login.conf` for `endlessh` (and
+`endlessh6`) like so:
+
+```
+endlessh:\
+	:openfiles=1024:\
+	:tc=daemon:
+endlessh6:\
+	:openfiles=1024:\
+	:tc=daemon:
+```