Issue #10883: Fix socket leaks in urllib.request.

* ftpwrapper now uses reference counting to ensure that the underlying socket
  is closed when the ftpwrapper object is no longer in use
* ftplib.FTP.ntransfercmd() now closes the socket if an error occurs

Initial patch by Victor Stinner.

1 files changed, 31 insertions, 25 deletions

diff --git a/Lib/ftplib.py b/Lib/ftplib.py
index 8713e47..c896433 100644
--- a/Lib/ftplib.py
+++ b/Lib/ftplib.py
@@ -325,33 +325,39 @@ class FTP:
         if self.passiveserver:
             host, port = self.makepasv()
             conn = socket.create_connection((host, port), self.timeout)
-            if rest is not None:
-                self.sendcmd("REST %s" % rest)
-            resp = self.sendcmd(cmd)
-            # Some servers apparently send a 200 reply to
-            # a LIST or STOR command, before the 150 reply
-            # (and way before the 226 reply). This seems to
-            # be in violation of the protocol (which only allows
-            # 1xx or error messages for LIST), so we just discard
-            # this response.
-            if resp[0] == '2':
-                resp = self.getresp()
-            if resp[0] != '1':
-                raise error_reply, resp
+            try:
+                if rest is not None:
+                    self.sendcmd("REST %s" % rest)
+                resp = self.sendcmd(cmd)
+                # Some servers apparently send a 200 reply to
+                # a LIST or STOR command, before the 150 reply
+                # (and way before the 226 reply). This seems to
+                # be in violation of the protocol (which only allows
+                # 1xx or error messages for LIST), so we just discard
+                # this response.
+                if resp[0] == '2':
+                    resp = self.getresp()
+                if resp[0] != '1':
+                    raise error_reply, resp
+            except:
+                conn.close()
+                raise
         else:
             sock = self.makeport()
-            if rest is not None:
-                self.sendcmd("REST %s" % rest)
-            resp = self.sendcmd(cmd)
-            # See above.
-            if resp[0] == '2':
-                resp = self.getresp()
-            if resp[0] != '1':
-                raise error_reply, resp
-            conn, sockaddr = sock.accept()
-            if self.timeout is not _GLOBAL_DEFAULT_TIMEOUT:
-                conn.settimeout(self.timeout)
-            sock.close()
+            try:
+                if rest is not None:
+                    self.sendcmd("REST %s" % rest)
+                resp = self.sendcmd(cmd)
+                # See above.
+                if resp[0] == '2':
+                    resp = self.getresp()
+                if resp[0] != '1':
+                    raise error_reply, resp
+                conn, sockaddr = sock.accept()
+                if self.timeout is not _GLOBAL_DEFAULT_TIMEOUT:
+                    conn.settimeout(self.timeout)
+            finally:
+                sock.close()
         if resp[:3] == '150':
             # this is conditional in case we received a 125
             size = parse150(resp)