Backward compatibility with Python 2.4 (server)

It is often the case that the user has no administrative control over
the server that is being used. As such it is important to support as
many versions as possible, at least on the remote server end. These
fixes will allow sshuttle to be used with servers that have only
python 2.4 or python 2.6 installed while hopefully not breaking the
compatibility with 2.7 and 3.5.

sshuttle/assembler.py

@@ -13,8 +13,9 @@ while 1:
         content = z.decompress(sys.stdin.read(nbytes))
 
         module = imp.new_module(name)
-        parent, _, parent_name = name.rpartition(".")
+        parents = name.rsplit(".", 1)
-        if parent != "":
+        if len(parents) == 2:
+            parent, parent_name = parents
             setattr(sys.modules[parent], parent_name, module)
 
         code = compile(content, name, "exec")

sshuttle/helpers.py

@@ -5,6 +5,16 @@ import errno
 logprefix = ''
 verbose = 0
 
+if sys.version_info[0] == 3:
+    binary_type = bytes
+
+    def b(s):
+        return s.encode("latin-1")
+else:
+    binary_type = str
+
+    def b(s):
+        return s
 
 def log(s):
     try:
@@ -62,7 +72,8 @@ def islocal(ip, family):
     try:
         try:
             sock.bind((ip, 0))
-        except socket.error as e:
+        except socket.error:
+            _, e = sys.exc_info()[:2]
             if e.args[0] == errno.EADDRNOTAVAIL:
                 return False  # not a local IP
             else:

sshuttle/hostwatch.py

@@ -22,7 +22,8 @@ hostnames = {}
 queue = {}
 try:
     null = open('/dev/null', 'wb')
-except IOError as e:
+except IOError:
+    _, e = sys.exc_info()[:2]
     log('warning: %s\n' % e)
     null = os.popen("sh -c 'while read x; do :; done'", 'wb', 4096)
 
@@ -38,7 +39,7 @@ def write_host_cache():
         for name, ip in sorted(hostnames.items()):
             f.write('%s,%s\n' % (name, ip))
         f.close()
-        os.chmod(tmpname, 0o600)
+        os.chmod(tmpname, 384) # 600 in octal, 'rw-------'
         os.rename(tmpname, CACHEFILE)
     finally:
         try:
@@ -50,7 +51,8 @@ def write_host_cache():
 def read_host_cache():
     try:
         f = open(CACHEFILE)
-    except IOError as e:
+    except IOError:
+        _, e = sys.exc_info()[:2]
         if e.errno == errno.ENOENT:
             return
         else:
@@ -124,7 +126,8 @@ def _check_netstat():
         p = ssubprocess.Popen(argv, stdout=ssubprocess.PIPE, stderr=null)
         content = p.stdout.read()
         p.wait()
-    except OSError as e:
+    except OSError:
+        _, e = sys.exc_info()[:2]
         log('%r failed: %r\n' % (argv, e))
         return
 
@@ -144,7 +147,8 @@ def _check_smb(hostname):
         p = ssubprocess.Popen(argv, stdout=ssubprocess.PIPE, stderr=null)
         lines = p.stdout.readlines()
         p.wait()
-    except OSError as e:
+    except OSError:
+        _, e = sys.exc_info()[:2]
         log('%r failed: %r\n' % (argv, e))
         _smb_ok = False
         return
@@ -201,7 +205,8 @@ def _check_nmb(hostname, is_workgroup, is_master):
         p = ssubprocess.Popen(argv, stdout=ssubprocess.PIPE, stderr=null)
         lines = p.stdout.readlines()
         rv = p.wait()
-    except OSError as e:
+    except OSError:
+        _, e = sys.exc_info()[:2]
         log('%r failed: %r\n' % (argv, e))
         _nmb_ok = False
         return

sshuttle/server.py

@@ -147,7 +147,8 @@ class DnsProxy(Handler):
         try:
             sock.send(self.request)
             self.socks.append(sock)
-        except socket.error as e:
+        except socket.error:
+            _, e = sys.exc_info()[:2]
             if e.args[0] in ssnet.NET_ERRS:
                 # might have been spurious; try again.
                 # Note: these errors sometimes are reported by recv(),
@@ -164,7 +165,8 @@ class DnsProxy(Handler):
 
         try:
             data = sock.recv(4096)
-        except socket.error as e:
+        except socket.error:
+            _, e = sys.exc_info()[:2]
             self.socks.remove(sock)
             del self.peers[sock]
 
@@ -199,14 +201,16 @@ class UdpProxy(Handler):
         debug2('UDP: sending to %r port %d\n' % dstip)
         try:
             self.sock.sendto(data, dstip)
-        except socket.error as e:
+        except socket.error:
+            _, e = sys.exc_info()[:2]
             log('UDP send to %r port %d: %s\n' % (dstip[0], dstip[1], e))
             return
 
     def callback(self, sock):
         try:
             data, peer = sock.recvfrom(4096)
-        except socket.error as e:
+        except socket.error:
+            _, e = sys.exc_info()[:2]
             log('UDP recv from %r port %d: %s\n' % (peer[0], peer[1], e))
             return
         debug2('UDP response: %d bytes\n' % len(data))

sshuttle/ssnet.py

@@ -1,9 +1,10 @@
+import sys
 import struct
 import socket
 import errno
 import select
 import os
-from sshuttle.helpers import log, debug1, debug2, debug3, Fatal
+from sshuttle.helpers import b, binary_type, log, debug1, debug2, debug3, Fatal
 
 MAX_CHANNEL = 65535
 
@@ -75,7 +76,8 @@ def _fds(l):
 def _nb_clean(func, *args):
     try:
         return func(*args)
-    except OSError as e:
+    except OSError:
+        _, e = sys.exc_info()[:2]
         if e.errno not in (errno.EWOULDBLOCK, errno.EAGAIN):
             raise
         else:
@@ -88,7 +90,8 @@ def _try_peername(sock):
         pn = sock.getpeername()
         if pn:
             return '%s:%s' % (pn[0], pn[1])
-    except socket.error as e:
+    except socket.error:
+        _, e = sys.exc_info()[:2]
         if e.args[0] not in (errno.ENOTCONN, errno.ENOTSOCK):
             raise
     return 'unknown'
@@ -144,7 +147,8 @@ class SockWrapper:
             self.rsock.connect(self.connect_to)
             # connected successfully (Linux)
             self.connect_to = None
-        except socket.error as e:
+        except socket.error:
+            _, e = sys.exc_info()[:2]
             debug3('%r: connect result: %s\n' % (self, e))
             if e.args[0] == errno.EINVAL:
                 # this is what happens when you call connect() on a socket
@@ -191,7 +195,8 @@ class SockWrapper:
             self.shut_write = True
             try:
                 self.wsock.shutdown(SHUT_WR)
-            except socket.error as e:
+            except socket.error:
+                _, e = sys.exc_info()[:2]
                 self.seterr('nowrite: %s' % e)
 
     def too_full(self):
@@ -203,7 +208,8 @@ class SockWrapper:
         self.wsock.setblocking(False)
         try:
             return _nb_clean(os.write, self.wsock.fileno(), buf)
-        except OSError as e:
+        except OSError:
+            _, e = sys.exc_info()[:2]
             if e.errno == errno.EPIPE:
                 debug1('%r: uwrite: got EPIPE\n' % self)
                 self.nowrite()
@@ -225,9 +231,10 @@ class SockWrapper:
         self.rsock.setblocking(False)
         try:
             return _nb_clean(os.read, self.rsock.fileno(), 65536)
-        except OSError as e:
+        except OSError:
+            _, e = sys.exc_info()[:2]
             self.seterr('uread: %s' % e)
-            return b''  # unexpected error... we'll call it EOF
+            return b('')  # unexpected error... we'll call it EOF
 
     def fill(self):
         if self.buf:
@@ -235,7 +242,7 @@ class SockWrapper:
         rb = self.uread()
         if rb:
             self.buf.append(rb)
-        if rb == b'':  # empty string means EOF; None means temporarily empty
+        if rb == b(''):  # empty string means EOF; None means temporarily empty
             self.noread()
 
     def copy_to(self, outwrap):
@@ -333,11 +340,11 @@ class Mux(Handler):
         self.channels = {}
         self.chani = 0
         self.want = 0
-        self.inbuf = b''
+        self.inbuf = b('')
         self.outbuf = []
         self.fullness = 0
         self.too_full = False
-        self.send(0, CMD_PING, b'chicken')
+        self.send(0, CMD_PING, b('chicken'))
 
     def next_channel(self):
         # channel 0 is special, so we never allocate it
@@ -357,7 +364,7 @@ class Mux(Handler):
     def check_fullness(self):
         if self.fullness > 32768:
             if not self.too_full:
-                self.send(0, CMD_PING, b'rttest')
+                self.send(0, CMD_PING, b('rttest'))
             self.too_full = True
         # ob = []
         # for b in self.outbuf:
@@ -366,9 +373,9 @@ class Mux(Handler):
         # log('outbuf: %d %r\n' % (self.amount_queued(), ob))
 
     def send(self, channel, cmd, data):
-        assert isinstance(data, bytes)
+        assert isinstance(data, binary_type)
         assert len(data) <= 65535
-        p = struct.pack('!ccHHH', b'S', b'S', channel, cmd, len(data)) + data
+        p = struct.pack('!ccHHH', b('S'), b('S'), channel, cmd, len(data)) + data
         self.outbuf.append(p)
         debug2(' > channel=%d cmd=%s len=%d (fullness=%d)\n'
                % (channel, cmd_to_name.get(cmd, hex(cmd)),
@@ -434,14 +441,15 @@ class Mux(Handler):
     def fill(self):
         self.rsock.setblocking(False)
         try:
-            b = _nb_clean(os.read, self.rsock.fileno(), 32768)
+            read = _nb_clean(os.read, self.rsock.fileno(), 32768)
-        except OSError as e:
+        except OSError:
+            _, e = sys.exc_info()[:2]
             raise Fatal('other end: %r' % e)
         # log('<<< %r\n' % b)
-        if b == b'':  # EOF
+        if read == b(''):  # EOF
             self.ok = False
-        if b:
+        if read:
-            self.inbuf += b
+            self.inbuf += read
 
     def handle(self):
         self.fill()
@@ -451,8 +459,8 @@ class Mux(Handler):
             if len(self.inbuf) >= (self.want or HDR_LEN):
                 (s1, s2, channel, cmd, datalen) = \
                     struct.unpack('!ccHHH', self.inbuf[:HDR_LEN])
-                assert(s1 == b'S')
+                assert(s1 == b('S'))
-                assert(s2 == b'S')
+                assert(s2 == b('S'))
                 self.want = datalen + HDR_LEN
             if self.want and len(self.inbuf) >= self.want:
                 data = self.inbuf[HDR_LEN:self.want]
@@ -496,14 +504,14 @@ class MuxWrapper(SockWrapper):
         if not self.shut_read:
             debug2('%r: done reading\n' % self)
             self.shut_read = True
-            self.mux.send(self.channel, CMD_TCP_STOP_SENDING, b'')
+            self.mux.send(self.channel, CMD_TCP_STOP_SENDING, b(''))
             self.maybe_close()
 
     def nowrite(self):
         if not self.shut_write:
             debug2('%r: done writing\n' % self)
             self.shut_write = True
-            self.mux.send(self.channel, CMD_TCP_EOF, b'')
+            self.mux.send(self.channel, CMD_TCP_EOF, b(''))
             self.maybe_close()
 
     def maybe_close(self):
@@ -526,7 +534,7 @@ class MuxWrapper(SockWrapper):
 
     def uread(self):
         if self.shut_read:
-            return b''  # EOF
+            return b('')  # EOF
         else:
             return None  # no data available right now