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.

11 files changed, 111 insertions, 65 deletions

diff --git a/.travis.yml b/.travis.yml
index 4ab35a4..28e7a80 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,8 @@
 language: python
 python:
+- 2.6
 - 2.7
+- 3.4
 - 3.5
 - pypy
 
diff --git a/conftest.py b/conftest.py
new file mode 100644
index 0000000..969c119
--- /dev/null
+++ b/conftest.py
@@ -0,0 +1,10 @@
+import sys
+
+if sys.version_info >= (3, 0):
+    good_python = sys.version_info >= (3, 5)
+else:
+    good_python = sys.version_info >= (2, 7)
+
+collect_ignore = []
+if not good_python:
+    collect_ignore.append("sshuttle/tests/client")
diff --git a/docs/requirements.rst b/docs/requirements.rst
index 0c66538..c35824f 100644
--- a/docs/requirements.rst
+++ b/docs/requirements.rst
@@ -62,6 +62,7 @@ cmd.exe with Administrator access. See :doc:`windows` for more information.
 
 Server side Requirements
 ------------------------
+Server requirements are more relaxed, however it is recommended that you use
 Python 2.7 or Python 3.5.
 
 
diff --git a/sshuttle/assembler.py b/sshuttle/assembler.py
index 330528d..137331e 100644
--- a/sshuttle/assembler.py
+++ b/sshuttle/assembler.py
@@ -4,19 +4,20 @@ import imp
 
 z = zlib.decompressobj()
 while 1:
-    name = stdin.readline().strip()
+    name = sys.stdin.readline().strip()
     if name:
         name = name.decode("ASCII")
 
-        nbytes = int(stdin.readline())
+        nbytes = int(sys.stdin.readline())
         if verbosity >= 2:
             sys.stderr.write('server: assembling %r (%d bytes)\n'
                              % (name, nbytes))
-        content = z.decompress(stdin.read(nbytes))
+        content = z.decompress(sys.stdin.read(nbytes))
 
         module = imp.new_module(name)
-        parent, _, parent_name = name.rpartition(".")
-        if parent != "":
+        parents = name.rsplit(".", 1)
+        if len(parents) == 2:
+            parent, parent_name = parents
             setattr(sys.modules[parent], parent_name, module)
 
         code = compile(content, name, "exec")
diff --git a/sshuttle/helpers.py b/sshuttle/helpers.py
index 4e80e33..67a6013 100644
--- a/sshuttle/helpers.py
+++ b/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("ASCII")
+else:
+    binary_type = str
+
+    def b(s):
+        return s
 
 def log(s):
     global logprefix
@@ -70,7 +80,8 @@ 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:
diff --git a/sshuttle/hostwatch.py b/sshuttle/hostwatch.py
index 95a539a..be210f9 100644
--- a/sshuttle/hostwatch.py
+++ b/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)).encode("ASCII"))
         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().decode("ASCII")
         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
diff --git a/sshuttle/server.py b/sshuttle/server.py
index 78252b8..a47c760 100644
--- a/sshuttle/server.py
+++ b/sshuttle/server.py
@@ -12,29 +12,29 @@ import sshuttle.helpers as helpers
 import sshuttle.hostwatch as hostwatch
 import subprocess as ssubprocess
 from sshuttle.ssnet import Handler, Proxy, Mux, MuxWrapper
-from sshuttle.helpers import log, debug1, debug2, debug3, Fatal, \
+from sshuttle.helpers import b, log, debug1, debug2, debug3, Fatal, \
     resolvconf_random_nameserver
 
 
 def _ipmatch(ipstr):
     # FIXME: IPv4 only
-    if ipstr == b'default':
-        ipstr = b'0.0.0.0/0'
-    m = re.match(b'^(\d+(\.\d+(\.\d+(\.\d+)?)?)?)(?:/(\d+))?$', ipstr)
+    if ipstr == 'default':
+        ipstr = '0.0.0.0/0'
+    m = re.match('^(\d+(\.\d+(\.\d+(\.\d+)?)?)?)(?:/(\d+))?$', ipstr)
     if m:
         g = m.groups()
         ips = g[0]
         width = int(g[4] or 32)
         if g[1] is None:
-            ips += b'.0.0.0'
+            ips += '.0.0.0'
             width = min(width, 8)
         elif g[2] is None:
-            ips += b'.0.0'
+            ips += '.0.0'
             width = min(width, 16)
         elif g[3] is None:
-            ips += b'.0'
+            ips += '.0'
             width = min(width, 24)
-        ips = ips.decode("ASCII")
+        ips = ips
         return (struct.unpack('!I', socket.inet_aton(ips))[0], width)
 
 
@@ -66,7 +66,7 @@ def _list_routes():
     p = ssubprocess.Popen(argv, stdout=ssubprocess.PIPE)
     routes = []
     for line in p.stdout:
-        cols = re.split(b'\s+', line)
+        cols = re.split(r'\s+', line.decode("ASCII"))
         ipw = _ipmatch(cols[0])
         if not ipw:
             continue  # some lines won't be parseable; never mind
@@ -152,7 +152,8 @@ 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(),
@@ -169,7 +170,8 @@ 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]
 
@@ -204,14 +206,16 @@ 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))
@@ -244,26 +248,26 @@ def main(latency_control):
               socket.fromfd(sys.stdout.fileno(),
                             socket.AF_INET, socket.SOCK_STREAM))
     handlers.append(mux)
-    routepkt = b''
+    routepkt = ''
     for r in routes:
-        routepkt += b'%d,%s,%d\n' % (r[0], r[1].encode("ASCII"), r[2])
-    mux.send(0, ssnet.CMD_ROUTES, routepkt)
+        routepkt += '%d,%s,%d\n' % r
+    mux.send(0, ssnet.CMD_ROUTES, b(routepkt))
 
     hw = Hostwatch()
-    hw.leftover = b''
+    hw.leftover = b('')
 
     def hostwatch_ready(sock):
         assert(hw.pid)
         content = hw.sock.recv(4096)
         if content:
-            lines = (hw.leftover + content).split(b'\n')
+            lines = (hw.leftover + content).split(b('\n'))
             if lines[-1]:
                 # no terminating newline: entry isn't complete yet!
                 hw.leftover = lines.pop()
-                lines.append(b'')
+                lines.append(b(''))
             else:
-                hw.leftover = b''
-            mux.send(0, ssnet.CMD_HOST_LIST, b'\n'.join(lines))
+                hw.leftover = b('')
+            mux.send(0, ssnet.CMD_HOST_LIST, b('\n').join(lines))
         else:
             raise Fatal('hostwatch process died')
 
@@ -275,7 +279,7 @@ def main(latency_control):
     mux.got_host_req = got_host_req
 
     def new_channel(channel, data):
-        (family, dstip, dstport) = data.split(b',', 2)
+        (family, dstip, dstport) = data.decode("ASCII").split(',', 2)
         family = int(family)
         dstport = int(dstport)
         outwrap = ssnet.connect_dst(family, dstip, dstport)
diff --git a/sshuttle/ssh.py b/sshuttle/ssh.py
index cc89c0d..1a571d5 100644
--- a/sshuttle/ssh.py
+++ b/sshuttle/ssh.py
@@ -95,10 +95,10 @@ def connect(ssh_cmd, rhostport, python, stderr, options):
                 b"\n")
 
     pyscript = r"""
-                import sys;
+                import sys, os;
                 verbosity=%d;
-                stdin=getattr(sys.stdin,"buffer",sys.stdin);
-                exec(compile(stdin.read(%d), "assembler.py", "exec"))
+                sys.stdin = os.fdopen(0, "rb");
+                exec(compile(sys.stdin.read(%d), "assembler.py", "exec"))
                 """ % (helpers.verbose or 0, len(content))
     pyscript = re.sub(r'\s+', ' ', pyscript.strip())
 
diff --git a/sshuttle/ssnet.py b/sshuttle/ssnet.py
index 218e7b5..fe1de1e 100644
--- a/sshuttle/ssnet.py
+++ b/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)
-        except OSError as e:
+            read = _nb_clean(os.read, self.rsock.fileno(), 32768)
+        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:
-            self.inbuf += b
+        if read:
+            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(s2 == b'S')
+                assert(s1 == 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
 
diff --git a/sshuttle/tests/server/test_server.py b/sshuttle/tests/server/test_server.py
index bf6985f..6b437f7 100644
--- a/sshuttle/tests/server/test_server.py
+++ b/sshuttle/tests/server/test_server.py
@@ -5,9 +5,9 @@ from mock import patch, Mock, call
 
 
 def test__ipmatch():
-    assert sshuttle.server._ipmatch(b"1.2.3.4") is not None
-    assert sshuttle.server._ipmatch(b"::1") is None   # ipv6 not supported
-    assert sshuttle.server._ipmatch(b"42 Example Street, Melbourne") is None
+    assert sshuttle.server._ipmatch("1.2.3.4") is not None
+    assert sshuttle.server._ipmatch("::1") is None   # ipv6 not supported
+    assert sshuttle.server._ipmatch("42 Example Street, Melbourne") is None
 
 
 def test__ipstr():
@@ -16,7 +16,7 @@ def test__ipstr():
 
 
 def test__maskbits():
-    netmask = sshuttle.server._ipmatch(b"255.255.255.0")
+    netmask = sshuttle.server._ipmatch("255.255.255.0")
     sshuttle.server._maskbits(netmask)
 
 
diff --git a/tox.ini b/tox.ini
index e2e93f8..2b66655 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,12 +1,16 @@
 [tox]
 downloadcache = {toxworkdir}/cache/
 envlist =
+    py26,
     py27,
+    py34,
     py35,
 
 [testenv]
 basepython =
+    py26: python2.6
     py27: python2.7
+    py34: python3.4
     py35: python3.5
 commands =
     py.test