add proxy support powered by PySocks

Read proxy option in imapserver, instantiate a class in imaplibutil
using a self-defined keyword and a socket instance, and use this socket
instance to substitute the default socket instance used in imaplib2.

Signed-off-by: 夏恺(Xia Kai) <xiaket@gmail.com>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap.conf

@@ -380,6 +380,15 @@ remoterepository = RemoteExample
 #filterheaders = X-Some-Weird-Header
 
 
+# This option stands in the [Account Test] section.
+#
+# Use proxy connection for this account. Usefull to bypass the GFW in China.
+# To specify a proxy connection, join proxy type, host and port with colons.
+# Available proxy types are SOCKS5, SOCKS4, HTTP.
+# You also need to install PySocks through pip.
+#
+#proxy = SOCKS5:localhost:9999
+
 [Repository LocalExample]
 
 # Each repository requires a "type" declaration. The types supported for

offlineimap/imaplibutil.py

@@ -21,6 +21,7 @@ import subprocess
 from sys import exc_info
 import threading
 from hashlib import sha1
+import socket
 
 from offlineimap.ui import getglobalui
 from offlineimap import OfflineImapError
@@ -69,6 +70,37 @@ class UsefulIMAPMixIn(object):
     def _mesg(self, s, tn=None, secs=None):
         new_mesg(self, s, tn, secs)
 
+    # Overrides private function from IMAP4 (@imaplib2)
+    def open_socket(self):
+        """open_socket()
+        Open socket choosing first address family available."""
+        msg = (-1, 'could not open socket')
+        for res in socket.getaddrinfo(self.host, self.port, socket.AF_UNSPEC, socket.SOCK_STREAM):
+            af, socktype, proto, canonname, sa = res
+            try:
+                # use socket of our own, possiblly socksified socket.
+                s = self.socket(af, socktype, proto)
+            except socket.error, msg:
+                continue
+            try:
+                for i in (0, 1):
+                    try:
+                        s.connect(sa)
+                        break
+                    except socket.error, msg:
+                        if len(msg.args) < 2 or msg.args[0] != errno.EINTR:
+                            raise
+                else:
+                    raise socket.error(msg)
+            except socket.error, msg:
+                s.close()
+                continue
+            break
+        else:
+            raise socket.error(msg)
+
+        return s
+
 
 class IMAP4_Tunnel(UsefulIMAPMixIn, IMAP4):
     """IMAP4 client class over a tunnel
@@ -79,6 +111,9 @@ class IMAP4_Tunnel(UsefulIMAPMixIn, IMAP4):
     The result will be in PREAUTH stage."""
 
     def __init__(self, tunnelcmd, **kwargs):
+        if "use_socket" in kwargs:
+            self.socket = kwargs['use_socket']
+            del kwargs['use_socket']
         IMAP4.__init__(self, tunnelcmd, **kwargs)
 
     def open(self, host, port):
@@ -141,6 +176,9 @@ class WrappedIMAP4_SSL(UsefulIMAPMixIn, IMAP4_SSL):
     """Improved version of imaplib.IMAP4_SSL overriding select()."""
 
     def __init__(self, *args, **kwargs):
+        if "use_socket" in kwargs:
+            self.socket = kwargs['use_socket']
+            del kwargs['use_socket']
         self._fingerprint = kwargs.get('fingerprint', None)
         if type(self._fingerprint) != type([]):
             self._fingerprint = [self._fingerprint]
@@ -171,7 +209,11 @@ class WrappedIMAP4_SSL(UsefulIMAPMixIn, IMAP4_SSL):
 class WrappedIMAP4(UsefulIMAPMixIn, IMAP4):
     """Improved version of imaplib.IMAP4 overriding select()."""
 
-    pass
+    def __init__(self, *args, **kwargs):
+        if "use_socket" in kwargs:
+            self.socket = kwargs['use_socket']
+            del kwargs['use_socket']
+        IMAP4.__init__(self, *args, **kwargs)
 
 
 def Internaldate2epoch(resp):

offlineimap/imapserver.py

@@ -15,10 +15,7 @@
 #    along with this program; if not, write to the Free Software
 #    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 
-from offlineimap import imaplibutil, imaputil, threadutil, OfflineImapError
-from offlineimap.ui import getglobalui
 from threading import Lock, BoundedSemaphore, Thread, Event, currentThread
-import offlineimap.accounts
 import hmac
 import socket
 import base64
@@ -28,6 +25,11 @@ from sys import exc_info
 from socket import gaierror
 from ssl import SSLError, cert_time_to_seconds
 
+from offlineimap import imaplibutil, imaputil, threadutil, OfflineImapError
+import offlineimap.accounts
+from offlineimap.ui import getglobalui
+
+
 try:
     # do we have a recent pykerberos?
     have_gss = False
@@ -101,6 +103,31 @@ class IMAPServer:
         self.gss_vc = None
         self.gssapi = False
 
+        # In order to support proxy connection, we have to override the
+        # default socket instance with our own socksified socket instance.
+        # We add this option to bypass the GFW in China.
+        _account_section = 'Account ' + self.repos.account.name
+        if not self.config.has_option(_account_section, 'proxy'):
+            self.proxied_socket = socket.socket
+        else:
+            proxy = self.config.get(_account_section, 'proxy')
+            # Powered by PySocks.
+            try:
+                import socks
+                proxy_type, host, port = proxy.split(":")
+                port = int(port)
+                socks.setdefaultproxy(getattr(socks, proxy_type), host, port)
+                self.proxied_socket = socks.socksocket
+            except ImportError:
+                self.ui.warn("PySocks not installed, ignoring proxy option.")
+                self.proxied_socket = socket.socket
+            except (AttributeError, ValueError) as e:
+                self.ui.warn("Bad proxy option %s for account %s: %s "
+                    "Ignoring proxy option."%
+                    (proxy, self.repos.account.name, e))
+                self.proxied_socket = socket.socket
+
+
     def __getpassword(self):
         """Returns the server password or None"""
         if self.goodpassword != None: # use cached good one first
@@ -391,12 +418,16 @@ class IMAPServer:
                 # Generate a new connection.
                 if self.tunnel:
                     self.ui.connecting('tunnel', self.tunnel)
-                    imapobj = imaplibutil.IMAP4_Tunnel(self.tunnel,
+                    imapobj = imaplibutil.IMAP4_Tunnel(
-                                                       timeout=socket.getdefaulttimeout())
+                        self.tunnel,
+                        timeout=socket.getdefaulttimeout(),
+                        use_socket=self.proxied_socket,
+                        )
                     success = 1
                 elif self.usessl:
                     self.ui.connecting(self.hostname, self.port)
-                    imapobj = imaplibutil.WrappedIMAP4_SSL(self.hostname,
+                    imapobj = imaplibutil.WrappedIMAP4_SSL(
+                        self.hostname,
                         self.port,
                         self.sslclientkey,
                         self.sslclientcert,
@@ -404,12 +435,16 @@ class IMAPServer:
                         self.__verifycert,
                         self.sslversion,
                         timeout=socket.getdefaulttimeout(),
-                                                           fingerprint=self.fingerprint
+                        fingerprint=self.fingerprint,
+                        use_socket=self.proxied_socket,
                         )
                 else:
                     self.ui.connecting(self.hostname, self.port)
-                    imapobj = imaplibutil.WrappedIMAP4(self.hostname, self.port,
+                    imapobj = imaplibutil.WrappedIMAP4(
-                                                       timeout=socket.getdefaulttimeout())
+                        self.hostname, self.port,
+                        timeout=socket.getdefaulttimeout(),
+                        use_socket=self.proxied_socket,
+                        )
 
                 if not self.preauth_tunnel:
                     try: