Enhanced DNS support. Initial version.

README.md

@@ -63,19 +63,7 @@ This is how you use it:
     on your client machine. You'll need root or sudo
     access, and python needs to be installed.
 
- - The most basic use of sshuttle looks like:
-  <tt>./sshuttle -r username@sshserver 0.0.0.0/0 -vv</tt>
-
- - There is a shortcut for 0.0.0.0/0 for those that value
-   their wrists
-   <tt>./sshuttle -r username@sshserver 0/0 -vv</tt>
-
- - If you would also like your DNS queries to be proxied
-   through the DNS server of the server you are connect to:
-   <tt>./sshuttle --dns -rvv username@sshserver 0/0</tt>
-
-   The above is probably what you want to use to prevent
-   local network attacks such as Firesheep and friends.
+ - <tt>./sshuttle -r username@sshserver 0.0.0.0/0 -vv</tt>
 
 (You may be prompted for one or more passwords; first, the
 local password to become root using either sudo or su, and

client.py

@@ -175,8 +175,60 @@ class FirewallClient:
             raise Fatal('cleanup: %r returned %d' % (self.argv, rv))
 
 
+def unpack_dns_name(buf, off):
+    name = ''
+    while True:
+        # get the next octet from buffer
+        n = ord(buf[off])
+
+        # zero octet terminates name
+        if n == 0:
+            off += 1
+            break
+
+        # top two bits on
+        # => a 2 octect pointer to another part of the buffer
+        elif (n & 0xc0) == 0xc0:
+            ptr = struct.unpack('>H', buf[off:off+2])[0] & 0x3fff
+            off = ptr
+
+        # an octet representing the number of bytes to process.
+        else:
+            off += 1
+            name = name + buf[off:off+n] + '.'
+            off += n
+
+    return name.strip('.'), off
+
+class dnspkt:
+    def unpack(self, buf, off):
+        l = len(buf)
+
+        (self.id, self.op, self.qdcount, self.ancount, self.nscount, self.arcount) = struct.unpack("!HHHHHH",buf[off:off+12])
+        off += 12
+
+        self.q = []
+        for i in range(self.qdcount):
+            qname, off = unpack_dns_name(buf, off)
+            qtype, qclass = struct.unpack('!HH', buf[off:off+4])
+            off += 4
+            self.q.append( (qname,qtype,qclass) )
+
+        return off
+
+    def match_q_domain(self, domain):
+        l = len(domain)
+        for qname,qtype,qclass in self.q:
+            if qname[-l:] == domain:
+                if l==len(qname):
+                    return True
+                elif qname[-l-1] == '.':
+                    return True
+        return False
+
 def _main(listener, fw, ssh_cmd, remotename, python, latency_control,
-          dnslistener, seed_hosts, auto_nets,
+          dnslistener, dnsforwarder, dns_domains, dns_to,
+          seed_hosts, auto_nets,
           syslog, daemon):
     handlers = []
     if helpers.verbose >= 1:
@@ -198,14 +250,7 @@ def _main(listener, fw, ssh_cmd, remotename, python, latency_control,
     handlers.append(mux)
 
     expected = 'SSHUTTLE0001'
-    
     try:
-        v = 'x'
-        while v and v != '\0':
-            v = serversock.recv(1)
-        v = 'x'
-        while v and v != '\0':
-            v = serversock.recv(1)
         initstring = serversock.recv(len(expected))
     except socket.error, e:
         if e.args[0] == errno.ECONNRESET:
@@ -290,6 +335,7 @@ def _main(listener, fw, ssh_cmd, remotename, python, latency_control,
     handlers.append(Handler([listener], onaccept))
 
     dnsreqs = {}
+    dnsforwards = {}
     def dns_done(chan, data):
         peer,timeout = dnsreqs.get(chan) or (None,None)
         debug3('dns_done: channel=%r peer=%r\n' % (chan, peer))
@@ -302,16 +348,54 @@ def _main(listener, fw, ssh_cmd, remotename, python, latency_control,
         now = time.time()
         if pkt:
             debug1('DNS request from %r: %d bytes\n' % (peer, len(pkt)))
+            dns = dnspkt()
+            dns.unpack(pkt, 0)
+
+            match=False
+            if dns_domains is not None:
+                for domain in dns_domains:
+                    if dns.match_q_domain(domain):
+                        match=True
+                        break
+
+            if match:
+                debug3("We need to redirect this request remotely\n")
                 chan = mux.next_channel()
                 dnsreqs[chan] = peer,now+30
                 mux.send(chan, ssnet.CMD_DNS_REQ, pkt)
                 mux.channels[chan] = lambda cmd,data: dns_done(chan,data)
+            else:
+                debug3("We need to forward this request locally\n")
+                dnsforwarder.sendto(pkt, dns_to)
+                dnsforwards[dns.id] = peer,now+30
         for chan,(peer,timeout) in dnsreqs.items():
             if timeout < now:
                 del dnsreqs[chan]
+        for chan,(peer,timeout) in dnsforwards.items():
+            if timeout < now:
+                del dnsforwards[chan]
         debug3('Remaining DNS requests: %d\n' % len(dnsreqs))
+        debug3('Remaining DNS forwards: %d\n' % len(dnsforwards))
     if dnslistener:
         handlers.append(Handler([dnslistener], ondns))
+    def ondnsforward():
+        debug1("We got a response.\n")
+        pkt,server = dnsforwarder.recvfrom(4096)
+        now = time.time()
+        if server[0] != dns_to[0] or server[1] != dns_to[1]:
+            debug1("Ooops. The response came from the wrong server. Ignoring\n")
+        else:
+            dns = dnspkt()
+            dns.unpack(pkt, 0)
+            chan=dns.id
+            peer,timeout = dnsforwards.get(chan) or (None,None)
+            debug3('dns_done: channel=%r peer=%r\n' % (chan, peer))
+            if peer:
+                del dnsforwards[chan]
+                debug3('doing sendto %r\n' % (peer,))
+                dnslistener.sendto(pkt, peer)
+    if dnsforwarder:
+        handlers.append(Handler([dnsforwarder], ondnsforward))
 
     if seed_hosts != None:
         debug1('seed_hosts: %r\n' % seed_hosts)
@@ -328,7 +412,8 @@ def _main(listener, fw, ssh_cmd, remotename, python, latency_control,
         mux.callback()
 
 
-def main(listenip, ssh_cmd, remotename, python, latency_control, dns,
+def main(listenip, ssh_cmd, remotename, python, latency_control,
+         dns, dns_domains, dns_to,
          seed_hosts, auto_nets,
          subnets_include, subnets_exclude, syslog, daemon, pidfile):
     if syslog:
@@ -373,15 +458,21 @@ def main(listenip, ssh_cmd, remotename, python, latency_control, dns,
         dnsip = dnslistener.getsockname()
         debug1('DNS listening on %r.\n' % (dnsip,))
         dnsport = dnsip[1]
+
+        dnsforwarder = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        dnsforwarder.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        dnsforwarder.setsockopt(socket.SOL_IP, socket.IP_TTL, 42)
     else:
         dnsport = 0
         dnslistener = None
+        dnsforwarder = None
 
     fw = FirewallClient(listenip[1], subnets_include, subnets_exclude, dnsport)
     
     try:
         return _main(listener, fw, ssh_cmd, remotename,
-                     python, latency_control, dnslistener,
+                     python, latency_control,
+                     dnslistener, dnsforwarder, dns_domains, dns_to,
                      seed_hosts, auto_nets, syslog, daemon)
     finally:
         try:

do

@@ -8,14 +8,14 @@
 #
 
 # By default, no output coloring.
-green=""
-bold=""
-plain=""
+GREEN=""
+BOLD=""
+PLAIN=""
 
 if [ -n "$TERM" -a "$TERM" != "dumb" ] && tty <&2 >/dev/null 2>&1; then
-	green="$(printf '\033[32m')"
-	bold="$(printf '\033[1m')"
-	plain="$(printf '\033[m')"
+	GREEN="$(printf '\033[32m')"
+	BOLD="$(printf '\033[1m')"
+	PLAIN="$(printf '\033[m')"
 fi
 
 _dirsplit()
@@ -24,13 +24,6 @@ _dirsplit()
 	dir=${1%$base}
 }
 
-dirname()
-(
-	_dirsplit "$1"
-	dir=${dir%/}
-	echo "${dir:-.}"
-)
-
 _dirsplit "$0"
 export REDO=$(cd "${dir:-.}" && echo "$PWD/$base")
 
@@ -61,105 +54,87 @@ fi
 
 _find_dofile_pwd()
 {
-	dofile=default.$1.do
+	DOFILE=default.$1.do
 	while :; do
-		dofile=default.${dofile#default.*.}
-		[ -e "$dofile" -o "$dofile" = default.do ] && break
+		DOFILE=default.${DOFILE#default.*.}
+		[ -e "$DOFILE" -o "$DOFILE" = default.do ] && break
 	done
-	ext=${dofile#default}
-	ext=${ext%.do}
-	base=${1%$ext}
+	EXT=${DOFILE#default}
+	EXT=${EXT%.do}
+	BASE=${1%$EXT}
 }
 
 
 _find_dofile()
 {
-	local prefix=
+	PREFIX=
 	while :; do
 		_find_dofile_pwd "$1"
-		[ -e "$dofile" ] && break
+		[ -e "$DOFILE" ] && break
 		[ "$PWD" = "/" ] && break
-		target=${PWD##*/}/$target
-		tmp=${PWD##*/}/$tmp
-		prefix=${PWD##*/}/$prefix
+		TARGET=${PWD##*/}/$TARGET
+		PREFIX=${PWD##*/}/$PREFIX
 		cd ..
 	done
-	base=$prefix$base
+	BASE=$PREFIX$BASE
 }
 
 
 _run_dofile()
 {
 	export DO_DEPTH="$DO_DEPTH  "
-	export REDO_TARGET=$PWD/$target
-	local line1
+	export REDO_TARGET=$PWD/$TARGET
 	set -e
-	read line1 <"$PWD/$dofile"
+	read line1 <"$PWD/$DOFILE"
 	cmd=${line1#"#!/"}
 	if [ "$cmd" != "$line1" ]; then
-		/$cmd "$PWD/$dofile" "$@" >"$tmp.tmp2"
+		/$cmd "$PWD/$DOFILE" "$@" >"$TARGET.tmp2"
 	else
-		:; . "$PWD/$dofile" >"$tmp.tmp2"
+		. "$PWD/$DOFILE" >"$TARGET.tmp2"
 	fi
 }
 
 
 _do()
 {
-	local dir=$1 target=$2 tmp=$3
-	if [ ! -e "$target" ] || [ -d "$target" -a ! -e "$target.did" ]; then
+	DIR=$1
+	TARGET=$2
+	if [ ! -e "$TARGET" ] || [ -e "$TARGET/." -a ! -e "$TARGET.did" ]; then
 		printf '%sdo  %s%s%s%s\n' \
-			"$green" "$DO_DEPTH" "$bold" "$dir$target" "$plain" >&2
-		echo "$PWD/$target" >>"$DO_BUILT"
-		dofile=$target.do
-		base=$target
-		ext=
-		[ -e "$target.do" ] || _find_dofile "$target"
-		if [ ! -e "$dofile" ]; then
-			echo "do: $target: no .do file" >&2
+			"$GREEN" "$DO_DEPTH" "$BOLD" "$DIR$TARGET" "$PLAIN" >&2
+		echo "$PWD/$TARGET" >>"$DO_BUILT"
+		DOFILE=$TARGET.do
+		BASE=$TARGET
+		EXT=
+		[ -e "$TARGET.do" ] || _find_dofile "$TARGET"
+		if [ ! -e "$DOFILE" ]; then
+			echo "do: $TARGET: no .do file" >&2
 			return 1
 		fi
-		[ ! -e "$DO_BUILT" ] || [ ! -d "$(dirname "$target")" ] ||
-		: >>"$target.did"
-		( _run_dofile "$base" "$ext" "$tmp.tmp" )
-		rv=$?
-		if [ $rv != 0 ]; then
+		[ ! -e "$DO_BUILD" ] || : >>"$TARGET.did"
+		( _run_dofile "$BASE" "$EXT" "$TARGET.tmp" )
+		RV=$?
+		if [ $RV != 0 ]; then
 			printf "do: %s%s\n" "$DO_DEPTH" \
-				"$dir$target: got exit code $rv" >&2
-			rm -f "$tmp.tmp" "$tmp.tmp2"
-			return $rv
+				"$DIR$TARGET: got exit code $RV" >&2
+			rm -f "$TARGET.tmp" "$TARGET.tmp2"
+			return $RV
 		fi
-		mv "$tmp.tmp" "$target" 2>/dev/null ||
-		! test -s "$tmp.tmp2" ||
-		mv "$tmp.tmp2" "$target" 2>/dev/null
-		rm -f "$tmp.tmp2"
+		mv "$TARGET.tmp" "$TARGET" 2>/dev/null ||
+		! test -s "$TARGET.tmp2" ||
+		mv "$TARGET.tmp2" "$TARGET" 2>/dev/null
+		rm -f "$TARGET.tmp2"
 	else
-		echo "do  $DO_DEPTH$target exists." >&2
+		echo "do  $DO_DEPTH$TARGET exists." >&2
 	fi
 }
 
 
-# Make corrections for directories that don't actually exist yet.
-_dir_shovel()
-{
-	local dir base
-	xdir=$1 xbase=$2 xbasetmp=$2
-	while [ ! -d "$xdir" -a -n "$xdir" ]; do
-		_dirsplit "${xdir%/}"
-		xbasetmp=${base}__$xbase
-		xdir=$dir xbase=$base/$xbase
-		echo "xbasetmp='$xbasetmp'" >&2
-	done
-}
-
-
 redo()
 {
 	for i in "$@"; do
 		_dirsplit "$i"
-		_dir_shovel "$dir" "$base"
-		dir=$xdir base=$xbase basetmp=$xbasetmp
-		( cd "$dir" && _do "$dir" "$base" "$basetmp" ) || return 1
+		( cd "$dir" && _do "$dir" "$base" ) || return 1
 	done
 }
 

main.py

@@ -54,6 +54,8 @@ l,listen=  transproxy to this ip address and port number [127.0.0.1:0]
 H,auto-hosts scan for remote hostnames and update local /etc/hosts
 N,auto-nets  automatically determine subnets to route
 dns        capture local DNS requests and forward to the remote DNS server
+dns-domains= comma seperated list of DNS domains for DNS forwarding
+dns-to=    forward any DNS requests that don't match domains to this address
 python=    path to python interpreter on the remote server
 r,remote=  ssh hostname (and optional username) of remote sshuttle server
 x,exclude= exclude this subnet (can be used more than once)
@@ -110,12 +112,26 @@ try:
             sh = []
         else:
             sh = None
+        if opt.dns and opt.dns_domains:
+            dns_domains = opt.dns_domains.split(",")
+            if opt.dns_to:
+                addr,colon,port = opt.dns_to.rpartition(":")
+                if colon == ":":
+                    dns_to = ( addr, int(port) )
+                else:
+                    dns_to = ( port, 53 )
+            else:
+                o.fatal('--dns-to=ip is required with --dns-domains=list')
+        else:
+            dns_domains = None
+            dns_to = None
+
         sys.exit(client.main(parse_ipport(opt.listen or '0.0.0.0:0'),
                              opt.ssh_cmd,
                              remotename,
                              opt.python,
                              opt.latency_control,
-                             opt.dns,
+                             opt.dns, dns_domains, dns_to,
                              sh,
                              opt.auto_nets,
                              parse_subnets(includes),

server.py

@@ -130,7 +130,7 @@ class DnsProxy(Handler):
         try:
             self.sock.send(self.request)
         except socket.error, e:
-            if e.args[0] in ssnet.NET_ERRS:
+            if e.args[0] in [errno.ECONNREFUSED, errno.EHOSTUNREACH]:
                 # might have been spurious; try again.
                 # Note: these errors sometimes are reported by recv(),
                 # and sometimes by send().  We have to catch both.
@@ -145,7 +145,7 @@ class DnsProxy(Handler):
         try:
             data = self.sock.recv(4096)
         except socket.error, e:
-            if e.args[0] in ssnet.NET_ERRS:
+            if e.args[0] in [errno.ECONNREFUSED, errno.EHOSTUNREACH]:
                 # might have been spurious; try again.
                 # Note: these errors sometimes are reported by recv(),
                 # and sometimes by send().  We have to catch both.
@@ -173,7 +173,7 @@ def main():
         debug1('  %s/%d\n' % r)
         
     # synchronization header
-    sys.stdout.write('\0\0SSHUTTLE0001')
+    sys.stdout.write('SSHUTTLE0001')
     sys.stdout.flush()
 
     handlers = []

ssh.py

@@ -85,7 +85,7 @@ def connect(ssh_cmd, rhostport, python, stderr, options):
             pycmd = "'%s' -c '%s'" % (python, pyscript)
         else:
             pycmd = ("P=python2; $P -V 2>/dev/null || P=python; "
-                     "exec \"$P\" -c '%s'") % pyscript
+                     "\"$P\" -c '%s'") % pyscript
         argv = (sshl + 
                 portl + 
                 ipv6flag + 

sshuttle

@@ -1,10 +1,5 @@
 #!/bin/sh
-EXE=$0
-for i in 1 2 3 4 5 6 7 8 9 10; do
-	[ -L "$EXE" ] || break
-	EXE=$(readlink "$EXE")
-done
-DIR=$(dirname "$EXE")
+DIR=$(dirname "$0")
 if python2 -V 2>/dev/null; then
 	exec python2 "$DIR/main.py" python2 "$@"
 else

ssnet.py

@@ -42,10 +42,6 @@ cmd_to_name = {
 }
     
 
-NET_ERRS = [errno.ECONNREFUSED, errno.ETIMEDOUT,
-            errno.EHOSTUNREACH, errno.ENETUNREACH,
-            errno.EHOSTDOWN, errno.ENETDOWN]
-
 
 def _add(l, elem):
     if not elem in l:
@@ -128,12 +124,6 @@ class SockWrapper:
             return  # already connected
         self.rsock.setblocking(False)
         debug3('%r: trying connect to %r\n' % (self, self.connect_to))
-        if socket.inet_aton(self.connect_to[0])[0] == '\0':
-            self.seterr(Exception("Can't connect to %r: "
-                                  "IP address starts with zero\n"
-                                  % (self.connect_to,)))
-            self.connect_to = None
-            return
         try:
             self.rsock.connect(self.connect_to)
             # connected successfully (Linux)
@@ -155,7 +145,9 @@ class SockWrapper:
             elif e.args[0] == errno.EISCONN:
                 # connected successfully (BSD)
                 self.connect_to = None
-            elif e.args[0] in NET_ERRS + [errno.EACCES, errno.EPERM]:
+            elif e.args[0] in [errno.ECONNREFUSED, errno.ETIMEDOUT,
+                               errno.EHOSTUNREACH, errno.ENETUNREACH,
+                               errno.EACCES, errno.EPERM]:
                 # a "normal" kind of error
                 self.connect_to = None
                 self.seterr(e)

ui-macos/bits/runpython.do

@@ -1,10 +1,5 @@
 exec >&2
 redo-ifchange runpython.c
-ARCHES=""
-for d in /usr/libexec/gcc/darwin/*; do
-    ARCHES="$ARCHES -arch $(basename $d)"
-done
-gcc $ARCHES \
-	-Wall -o $3 runpython.c \
+gcc -Wall -o $3 runpython.c \
 	-I/usr/include/python2.5 \
 	-lpython2.5