v1.5: 10DEC2008

Fixed zombie generation.
        Added support scripts (), Makefile.
        Changed all 'connexions' to 'connections' to please
        pesky users. Damn users.

Makefile

@@ -0,0 +1,23 @@
+# Configuration
+
+USELIBWRAP=1	# Use libwrap?
+
+
+# End of configuration -- the rest should take care of
+# itself
+
+CC = gcc
+
+#LIBS=-lnet
+LIBS=
+
+ifneq ($(strip $(USELIBWRAP)),)
+	LIBS:=$(LIBS) -lwrap
+	CFLAGS=-DLIBWRAP
+endif
+
+all:
+	$(CC) $(CFLAGS) -o sslh sslh.c $(LIBS)
+	strip sslh
+
+

README

@@ -0,0 +1,83 @@
+sslh -- A ssl/ssh multiplexer.
+
+sslh lets one accept both HTTPS and SSH connections on the
+same port. It makes it possible to connect to an SSH server
+on port 443 (e.g. from inside a corporate firewall) while
+still serving HTTPS on that port. 
+
+
+Compilation instructions:
+
+Solaris:
+  cc -o sslh sslh.c -lresolv -lsocket -lnsl
+
+LynxOS:
+  gcc -o tcproxy tcproxy.c -lnetinet
+
+Linux:
+  cc -o sslh sslh.c -lnet
+or:
+  cc -o sslh sslh.c
+
+To compile with libwrap support:
+  cc -o sslh -DLIBWRAP sslh.c -lwrap
+
+To install:
+
+make
+cp sslh /usr/local/sbin
+cp scripts/etc.init.d.sslh /etc/init.d/sslh
+cp scripts/etc.default.sslh /etc/default/sslh
+
+You can edit settings in /etc/default/sslh:
+
+PIDFILE=/var/run/sslh.pid
+LISTEN=ifname:443
+SSH=localhost:22
+SSL=localhost:443
+
+A good scheme is to use the external name of the machine in
+$LISTEN, and bind httpd to localhost:443: that way, https
+connections coming from inside your network don't need to go
+through sslh, and sslh is only there as a frontal for
+connections coming from the internet.
+
+Sslh can optionnaly perform libwrap checks for the sshd
+service: because the connection to sshd will be coming
+locally from sslh, sshd cannot determine the IP of the
+client.
+
+Comments? questions? sslh@rutschle.net
+
+HISTORY
+
+v1.5: 10DEC2008
+        Fixed zombie generation.
+        Added support scripts (), Makefile.
+        Changed all 'connexions' to 'connections' to please
+        pesky users. Damn users.
+
+v1.4: 13JUL2008
+	Added libwrap support for ssh service (Christian Weinberger)
+        Only SSH is libwraped, not SSL.
+
+v1.3: 14MAY2008
+        Added parsing for local interface to listen on
+        Changed default SSL connection to port 442 (443 doesn't make
+        sense as a default as we're already listening on 443)
+        Syslog incoming connections
+
+v1.2: 12MAY2008
+        Fixed compilation warning for AMD64 (Thx Daniel Lange)
+
+v1.1: 21MAY2007
+        Making sslhc more like a real daemon:
+        * If $PIDFILE is defined, write first PID to it upon startup
+        * Fork at startup (detach from terminal)
+        (thanks to http://www.enderunix.org/docs/eng/daemon.php -- good checklist)
+        * Less memory usage (?)
+
+v1.0: 
+        * Basic functionality: privilege dropping, target hostnames and ports
+        configurable.
+

scripts/etc.default.sslh

@@ -0,0 +1,4 @@
+PIDFILE=/var/run/sslh.pid
+LISTEN=ifname:443
+SSH=localhost:22
+SSL=localhost:443

scripts/etc.init.d.sslh

@@ -0,0 +1,62 @@
+#! /bin/sh
+
+### BEGIN INIT INFO
+# Provides:		sslh
+# Default-Start:	2 3 4 5
+# Default-Stop:		1
+# Short-Description:	sslh proxy ssl & ssh connections
+### END INIT INFO
+
+set -e
+tag=sslh
+facility=user.info
+
+# /etc/init.d/sslh: start and stop the sslh proxy daemon
+
+# Defaults -- can be overridden in /etc/default/sslh
+PIDFILE=/var/run/sslh.pid
+LISTEN=thelonious:443
+SSH=localhost:22
+SSL=localhost:443
+
+if test -f /etc/default/sslh; then
+    . /etc/default/sslh
+    export PIDFILE=${PIDFILE}
+fi
+
+DAEMON=/usr/local/sbin/sslh 
+
+start()
+{
+        echo "Start services: sslh"
+        $DAEMON -u nobody -p ${LISTEN} -s ${SSH} -l ${SSL}
+        logger -t ${tag} -p ${facility} -i 'Started sslh'
+}
+
+stop()
+{
+        echo "Stop services: sslh"
+	killall $DAEMON
+        rm ${PIDFILE}
+      	logger -t ${tag} -p ${facility} -i 'Stopped sslh'
+}
+
+
+case "$1" in
+	  start)
+		    start
+		    ;;
+	  stop)
+		    stop
+		    ;;
+    restart)
+		    stop
+		    sleep 5
+		    start
+		    ;;
+	  *)
+		    echo "Usage: /etc/init.d/sslh {start|stop|restart}" >&2
+		    ;;
+esac
+
+exit 0

sslh.c

@@ -1,7 +1,7 @@
 /*
    Reimplementation of sslh in C
 
-# Copyright (C) 2007  Yves Rutschle
+# Copyright (C) 2007-2008  Yves Rutschle
 # 
 # This program is free software; you can redistribute it
 # and/or modify it under the terms of the GNU General Public
@@ -18,19 +18,9 @@
 # The full text for the General Public License is here:
 # http://www.gnu.org/licenses/gpl.html
 
-Comments? questions? sslh@rutschle.net
-
-Compilation instructions:
-
-Solaris:
-  cc -o sslh sslh.c -lresolv -lsocket -lnsl
-
-LynxOS:
-  gcc -o tcproxy tcproxy.c -lnetinet
-
 */
 
-#define VERSION "1.0"
+#define VERSION "1.5"
 
 #include <sys/types.h>
 #include <fcntl.h>
@@ -40,10 +30,18 @@ LynxOS:
 #include <stdio.h>
 #include <signal.h>
 #include <sys/socket.h>
+#include <sys/wait.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <netdb.h>
 #include <pwd.h>
+#include <syslog.h>
+
+#ifdef LIBWRAP
+#include <tcpd.h>
+int allow_severity =0, deny_severity = 0;
+#endif
+
 
 #define CHECK_RES_DIE(res, str) \
 if (res == -1) {    \
@@ -51,15 +49,26 @@ if (res == -1) {    \
    exit(1);         \
 }
 
-#define USAGE_STRING "usage:\n\tsslh [-t <timeout>] -u <username> -p <listenport> -s [sshhost:]port -l [sslhost:]port [-v]\n"
+#define USAGE_STRING \
+"sslh v" VERSION "\n" \
+"usage:\n" \
+"\texport PIDFILE=/var/run/sslhc.pid\n" \
+"\tsslh [-t <timeout>] -u <username> -p [listenaddr:]<listenport> \n" \
+"\t\t-s [sshhost:]port -l [sslhost:]port [-v]\n\n" \
+"-v: verbose\n" \
+"-p: address and port to listen on. default: 0.0.0.0:443\n" \
+"-s: SSH address: where to connect an SSH connection. default: localhost:22\n" \
+"-l: SSL address: where to connect an SSL connection.\n" \
+""
 
+int verbose = 0; /* That's really quite global */
 
-/* Starts a listening socket on specified port.
+/* Starts a listening socket on specified address.
    Returns file descriptor
    */
-int start_listen_socket(int port)
+int start_listen_socket(struct sockaddr *addr)
 {
-   struct sockaddr_in saddr;
+   struct sockaddr_in *saddr = (struct sockaddr_in*)addr;
    int sockfd, res, reuse;
 
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
@@ -69,10 +78,7 @@ int start_listen_socket(int port)
    res = setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (char*)&reuse, sizeof(reuse));
    CHECK_RES_DIE(res, "setsockopt");
 
-   memset(&saddr, 0, sizeof(saddr));
-   saddr.sin_port = htons(port);
-
-   res = bind (sockfd, (struct sockaddr*)&saddr, sizeof(saddr));
+   res = bind (sockfd, (struct sockaddr*)saddr, sizeof(*saddr));
    CHECK_RES_DIE(res, "bind");
 
    res = listen (sockfd, 5);
@@ -128,7 +134,7 @@ int shovel(int fd1, int fd2)
       if (FD_ISSET(fd1, &fds)) {
          res = fd2fd(fd2, fd1);
          if (!res) {
-            printf("client socket closed\n");
+            if (verbose) fprintf(stderr, "client socket closed\n");
             return res;
          }
       }
@@ -136,31 +142,28 @@ int shovel(int fd1, int fd2)
       if (FD_ISSET(fd2, &fds)) {
          res = fd2fd(fd1, fd2);
          if (!res) {
-            printf("server socket closed\n");
+            if (verbose) fprintf(stderr, "server socket closed\n");
             return res;
          }
       }
    }
 }
 
-/* returns a static string that prints the IP and port of the sockaddr */
-char* get_addr(struct sockaddr* s)
+/* returns a string that prints the IP and port of the sockaddr */
+char* sprintaddr(char* buf, size_t size, struct sockaddr* s)
 {
    char addr_str[1024];
-   static char addr_name[1024];
 
    inet_ntop(AF_INET, &((struct sockaddr_in*)s)->sin_addr, addr_str, sizeof(addr_str));
-   snprintf(addr_name, sizeof(addr_name), "%s:%d", addr_str,ntohs(((struct sockaddr_in*)s)->sin_port));
-   return addr_name;
+   snprintf(buf, size, "%s:%d", addr_str, ntohs(((struct sockaddr_in*)s)->sin_port));
+   return buf;
 }
 
 /* turns a "hostname:port" string into a struct sockaddr;
 sock: socket address to which to copy the addr
 fullname: input string -- it gets clobbered
-serv: default service/port
-(defaults don't work yet)
 */
-int resolve_name(struct sockaddr *sock, char* fullname, int port) {
+void resolve_name(struct sockaddr *sock, char* fullname) {
    struct addrinfo *addr, hint;
    char *serv, *host;
    int res;
@@ -170,7 +173,7 @@ int resolve_name(struct sockaddr *sock, char* fullname, int port) {
    if (!sep) /* No separator: parameter is just a port */
    {
       serv = fullname;
-      fprintf(stderr, "names must be fully specified as hostname:port for the moment\n");
+      fprintf(stderr, "names must be fully specified as hostname:port\n");
       exit(1);
    }
    else {
@@ -194,16 +197,61 @@ int resolve_name(struct sockaddr *sock, char* fullname, int port) {
    memcpy(sock, addr->ai_addr, sizeof(*sock));
 }
 
+/* syslogs who connected to where */
+void log_connection(int socket, char* target)
+{
+    struct sockaddr peeraddr;
+    socklen_t size = sizeof(peeraddr);
+    char buf[64];
+    int res;
+
+    res = getpeername(socket, &peeraddr, &size);
+    CHECK_RES_DIE(res, "getpeername");
+
+    syslog(LOG_INFO, "connection from %s forwarded to %s\n", 
+           sprintaddr(buf, sizeof(buf), &peeraddr), target);
+
+}
+
 /* 
- * Settings that depend on the command line.
+ * Settings that depend on the command line. That's less global than verbose * :-)
  * They're set in main(), but also used in start_shoveler(), and it'd be heavy-handed
  * to pass it all as parameters
  */
-int verbose = 0;
 int timeout = 2;
-int listen_port = 443;
+struct sockaddr addr_listen;
 struct sockaddr addr_ssl, addr_ssh;
 
+/* libwrap (tcpd): check the ssh connection is legal. This is necessary because
+ * the actual sshd will only see a connection coming from localhost and can't
+ * apply the rules itself.
+ */
+void check_access_rights(int in_socket)
+{
+#ifdef LIBWRAP
+    struct sockaddr peeraddr;
+    socklen_t size = sizeof(peeraddr);
+    char addr_str[1024];
+    struct hostent *host;
+    struct in_addr addr;
+    int res;
+
+    res = getpeername(in_socket, &peeraddr, &size);
+    CHECK_RES_DIE(res, "getpeername");
+    inet_ntop(AF_INET, &((struct sockaddr_in*)&peeraddr)->sin_addr, addr_str, sizeof(addr_str));
+
+    addr.s_addr = inet_addr(addr_str);
+    host = gethostbyaddr((char *)&addr, sizeof(addr), AF_INET);
+
+    if (!hosts_ctl("sshd", (host ? host->h_name : STRING_UNKNOWN), addr_str, STRING_UNKNOWN)) {
+        if (verbose)
+            fprintf(stderr, "access denied\n");
+        log_connection(in_socket, "access denied");
+        close(in_socket);
+        exit(0);
+    }
+#endif
+}
 
 /* Child process that finds out what to connect to and proxies 
  */
@@ -214,6 +262,7 @@ void start_shoveler(int in_socket)
    struct sockaddr *saddr;
    int res;
    int out_socket;
+   char *target;
 
    FD_ZERO(&fds);
    FD_SET(in_socket, &fds);
@@ -227,15 +276,18 @@ void start_shoveler(int in_socket)
    if (FD_ISSET(in_socket, &fds)) {
       /* The client wrote something to the socket: it's an SSL connection */
       saddr = &addr_ssl;
-      if (verbose)
-         fprintf(stderr, "Forwarding to SSL\n");
+      target = "SSL";
    } else {
       /* The client hasn't written anything and we timed out: connect to SSH */
       saddr = &addr_ssh;
-      if (verbose)
-         fprintf(stderr, "Forwarding to SSH\n");
+      target = "SSH";
+
+      /* do hosts_access check if built with libwrap support */
+      check_access_rights(in_socket);
    }
 
+   log_connection(in_socket, target);
+
    /* Connect the target socket */
    out_socket = socket(AF_INET, SOCK_STREAM, 0);
    res = connect(out_socket, saddr, sizeof(addr_ssl));
@@ -264,10 +316,13 @@ void child_handler(int signo)
 }
 void setup_signals(void)
 {
-    int res;
+    void* res;
 
-    res = (int)signal(SIGCHLD, &child_handler);
-    CHECK_RES_DIE(res, "signal");
+    res = signal(SIGCHLD, &child_handler);
+    if (res == SIG_ERR) {
+        perror("signal");
+        exit(1);
+    }
 }
 
 
@@ -289,6 +344,39 @@ void drop_privileges(char* user_name)
     CHECK_RES_DIE(res, "setuid");
 }
 
+/* Writes my PID if $PIDFILE is defined */
+void write_pid_file(void)
+{
+    char *pidfile = getenv("PIDFILE");
+    FILE *f;
+
+    if (!pidfile)
+        return;
+
+    f = fopen(pidfile, "w");
+    if (!f) {
+        perror(pidfile);
+        exit(1);
+    }
+
+    fprintf(f, "%d\n", getpid());
+    fclose(f);
+}
+
+void printsettings(void)
+{
+    char buf[64];
+
+    fprintf(
+            stderr, 
+            "SSL addr: %s (after timeout %ds)\n",
+            sprintaddr(buf, sizeof(buf), &addr_ssl), 
+            timeout
+           );
+    fprintf(stderr, "SSH addr: %s\n", sprintaddr(buf, sizeof(buf), &addr_ssh));
+    fprintf(stderr, "listening on %s\n", sprintaddr(buf, sizeof(buf), &addr_listen));
+}
+
 int main(int argc, char *argv[])
 {
 
@@ -296,14 +384,17 @@ int main(int argc, char *argv[])
    extern int optind;
    int c, res;
 
-   int in_socket, out_socket, listen_socket;
+   int in_socket, listen_socket;
 
    /* Init defaults */
    char *user_name = "nobody";
-   char ssl_str[] = "localhost:443"; /* need to copy -- Linux doesn't let write to BSS? */
+   char listen_str[] = "0.0.0.0:443";
+   char ssl_str[] = "localhost:442";
    char ssh_str[] = "localhost:22";
-   resolve_name(&addr_ssl, ssl_str, 443);
-   resolve_name(&addr_ssh, ssh_str, 22);
+
+   resolve_name(&addr_listen, listen_str);
+   resolve_name(&addr_ssl, ssl_str);
+   resolve_name(&addr_ssh, ssh_str);
 
    while ((c = getopt(argc, argv, "t:l:s:p:vu:")) != EOF) {
       switch (c) {
@@ -313,15 +404,15 @@ int main(int argc, char *argv[])
                       break;
 
               case 'p':
-                      listen_port = atoi(optarg);
+                      resolve_name(&addr_listen, optarg);
                       break;
 
               case 'l':
-                      resolve_name(&addr_ssl, optarg, 443);
+                      resolve_name(&addr_ssl, optarg);
                       break;
 
               case 's':
-                      resolve_name(&addr_ssh, optarg, 22);
+                      resolve_name(&addr_ssh, optarg);
                       break;
 
               case 'v':
@@ -338,24 +429,31 @@ int main(int argc, char *argv[])
       }
    }
 
-   if (verbose) {
-      fprintf(stderr, "SSL addr: %s (after timeout %ds)\n", get_addr(&addr_ssl), timeout);
-      fprintf(stderr, "SSH addr: %s\n", get_addr(&addr_ssh));
-      fprintf(stderr, "listening on port %d\n", listen_port);
-   }
-
+   if (verbose)
+       printsettings();
 
    setup_signals();
 
-   listen_socket = start_listen_socket(listen_port);
+   listen_socket = start_listen_socket(&addr_listen);
+
+   if (fork() > 0) exit(0); /* Detach */
+
+   write_pid_file();
 
    drop_privileges(user_name);
 
+   /* New session -- become group leader */
+   res = setsid();
+   CHECK_RES_DIE(res, "setsid: already process leader");
+
+   /* Open syslog connection */
+   openlog(argv[0], LOG_CONS, LOG_AUTH);
+
    /* Main server loop: accept connections, find what they are, fork shovelers */
    while (1)
    {
       in_socket = accept(listen_socket, 0, 0);
-      fprintf(stderr, "accepted fd %d\n", in_socket);
+      if (verbose) fprintf(stderr, "accepted fd %d\n", in_socket);
 
       if (!fork())
       {