server: always close http socket if responding with an error (issue6033)

It's possible for hgweb to respond _very_ early with an error if we're
catching certain types of errors. When we do, we need to tell the client
the socket is toast when there's a POST involved because otherwise there
can be lingering POST data on the socket that will confuse any future
requests on the socket. This manifested as a flaky failure on Linux in an
lfs extension test and a reliable failure on FreeBSD. With this patch
applied, test-lfs-serve-access.t now passes for me on FreeBSD.

Differential Revision: https://phab.mercurial-scm.org/D5498

mercurial/hgweb/server.py

@@ -1,373 +1,380 b''
 # hgweb/server.py - The standalone hg web server.
 #
 # Copyright 21 May 2005 - (c) 2005 Jake Edge <[e-mail]>
 # Copyright 2005-2007 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import errno
 import os
 import socket
 import sys
 import traceback
 import wsgiref.validate
 
 from ..i18n import _
 
 from .. import (
     encoding,
     error,
     pycompat,
     util,
 )
 
 httpservermod = util.httpserver
 socketserver = util.socketserver
 urlerr = util.urlerr
 urlreq = util.urlreq
 
 from . import (
     common,
 )
 
 def _splitURI(uri):
     """Return path and query that has been split from uri
 
     Just like CGI environment, the path is unquoted, the query is
     not.
     """
     if r'?' in uri:
         path, query = uri.split(r'?', 1)
     else:
         path, query = uri, r''
     return urlreq.unquote(path), query
 
 class _error_logger(object):
     def __init__(self, handler):
         self.handler = handler
     def flush(self):
         pass
     def write(self, str):
         self.writelines(str.split('\n'))
     def writelines(self, seq):
         for msg in seq:
             self.handler.log_error("HG error:  %s", msg)
 
 class _httprequesthandler(httpservermod.basehttprequesthandler):
 
     url_scheme = 'http'
 
     @staticmethod
     def preparehttpserver(httpserver, ui):
         """Prepare .socket of new HTTPServer instance"""
 
     def __init__(self, *args, **kargs):
         self.protocol_version = r'HTTP/1.1'
         httpservermod.basehttprequesthandler.__init__(self, *args, **kargs)
 
     def _log_any(self, fp, format, *args):
         fp.write(pycompat.sysbytes(
             r"%s - - [%s] %s" % (self.client_address[0],
                                  self.log_date_time_string(),
                                  format % args)) + '\n')
         fp.flush()
 
     def log_error(self, format, *args):
         self._log_any(self.server.errorlog, format, *args)
 
     def log_message(self, format, *args):
         self._log_any(self.server.accesslog, format, *args)
 
     def log_request(self, code=r'-', size=r'-'):
         xheaders = []
         if util.safehasattr(self, 'headers'):
             xheaders = [h for h in self.headers.items()
                         if h[0].startswith(r'x-')]
         self.log_message(r'"%s" %s %s%s',
                          self.requestline, str(code), str(size),
                          r''.join([r' %s:%s' % h for h in sorted(xheaders)]))
 
     def do_write(self):
         try:
             self.do_hgweb()
         except socket.error as inst:
             if inst[0] != errno.EPIPE:
                 raise
 
     def do_POST(self):
         try:
             self.do_write()
         except Exception:
             self._start_response(r"500 Internal Server Error", [])
             self._write(b"Internal Server Error")
             self._done()
             tb = r"".join(traceback.format_exception(*sys.exc_info()))
             # We need a native-string newline to poke in the log
             # message, because we won't get a newline when using an
             # r-string. This is the easy way out.
             newline = chr(10)
             self.log_error(r"Exception happened during processing "
                            r"request '%s':%s%s", self.path, newline, tb)
 
     def do_PUT(self):
         self.do_POST()
 
     def do_GET(self):
         self.do_POST()
 
     def do_hgweb(self):
         self.sent_headers = False
         path, query = _splitURI(self.path)
 
         # Ensure the slicing of path below is valid
         if (path != self.server.prefix
             and not path.startswith(self.server.prefix + b'/')):
             self._start_response(pycompat.strurl(common.statusmessage(404)),
                                  [])
+            if self.command == 'POST':
+                # Paranoia: tell the client we're going to close the
+                # socket so they don't try and reuse a socket that
+                # might have a POST body waiting to confuse us. We do
+                # this by directly munging self.saved_headers because
+                # self._start_response ignores Connection headers.
+                self.saved_headers = [(r'Connection', r'Close')]
             self._write(b"Not Found")
             self._done()
             return
 
         env = {}
         env[r'GATEWAY_INTERFACE'] = r'CGI/1.1'
         env[r'REQUEST_METHOD'] = self.command
         env[r'SERVER_NAME'] = self.server.server_name
         env[r'SERVER_PORT'] = str(self.server.server_port)
         env[r'REQUEST_URI'] = self.path
         env[r'SCRIPT_NAME'] = pycompat.sysstr(self.server.prefix)
         env[r'PATH_INFO'] = pycompat.sysstr(path[len(self.server.prefix):])
         env[r'REMOTE_HOST'] = self.client_address[0]
         env[r'REMOTE_ADDR'] = self.client_address[0]
         env[r'QUERY_STRING'] = query or r''
 
         if pycompat.ispy3:
             if self.headers.get_content_type() is None:
                 env[r'CONTENT_TYPE'] = self.headers.get_default_type()
             else:
                 env[r'CONTENT_TYPE'] = self.headers.get_content_type()
             length = self.headers.get(r'content-length')
         else:
             if self.headers.typeheader is None:
                 env[r'CONTENT_TYPE'] = self.headers.type
             else:
                 env[r'CONTENT_TYPE'] = self.headers.typeheader
             length = self.headers.getheader(r'content-length')
         if length:
             env[r'CONTENT_LENGTH'] = length
         for header in [h for h in self.headers.keys()
                        if h not in (r'content-type', r'content-length')]:
             hkey = r'HTTP_' + header.replace(r'-', r'_').upper()
             hval = self.headers.get(header)
             hval = hval.replace(r'\n', r'').strip()
             if hval:
                 env[hkey] = hval
         env[r'SERVER_PROTOCOL'] = self.request_version
         env[r'wsgi.version'] = (1, 0)
         env[r'wsgi.url_scheme'] = pycompat.sysstr(self.url_scheme)
         if env.get(r'HTTP_EXPECT', '').lower() == '100-continue':
             self.rfile = common.continuereader(self.rfile, self.wfile.write)
 
         env[r'wsgi.input'] = self.rfile
         env[r'wsgi.errors'] = _error_logger(self)
         env[r'wsgi.multithread'] = isinstance(self.server,
                                              socketserver.ThreadingMixIn)
         if util.safehasattr(socketserver, 'ForkingMixIn'):
             env[r'wsgi.multiprocess'] = isinstance(self.server,
                                                    socketserver.ForkingMixIn)
         else:
             env[r'wsgi.multiprocess'] = False
 
         env[r'wsgi.run_once'] = 0
 
         wsgiref.validate.check_environ(env)
 
         self.saved_status = None
         self.saved_headers = []
         self.length = None
         self._chunked = None
         for chunk in self.server.application(env, self._start_response):
             self._write(chunk)
         if not self.sent_headers:
             self.send_headers()
         self._done()
 
     def send_headers(self):
         if not self.saved_status:
             raise AssertionError("Sending headers before "
                                  "start_response() called")
         saved_status = self.saved_status.split(None, 1)
         saved_status[0] = int(saved_status[0])
         self.send_response(*saved_status)
         self.length = None
         self._chunked = False
         for h in self.saved_headers:
             self.send_header(*h)
             if h[0].lower() == r'content-length':
                 self.length = int(h[1])
         if (self.length is None and
             saved_status[0] != common.HTTP_NOT_MODIFIED):
             self._chunked = (not self.close_connection and
                              self.request_version == r'HTTP/1.1')
             if self._chunked:
                 self.send_header(r'Transfer-Encoding', r'chunked')
             else:
                 self.send_header(r'Connection', r'close')
         self.end_headers()
         self.sent_headers = True
 
     def _start_response(self, http_status, headers, exc_info=None):
         assert isinstance(http_status, str)
         code, msg = http_status.split(None, 1)
         code = int(code)
         self.saved_status = http_status
         bad_headers = (r'connection', r'transfer-encoding')
         self.saved_headers = [h for h in headers
                               if h[0].lower() not in bad_headers]
         return self._write
 
     def _write(self, data):
         if not self.saved_status:
             raise AssertionError("data written before start_response() called")
         elif not self.sent_headers:
             self.send_headers()
         if self.length is not None:
             if len(data) > self.length:
                 raise AssertionError("Content-length header sent, but more "
                                      "bytes than specified are being written.")
             self.length = self.length - len(data)
         elif self._chunked and data:
             data = '%x\r\n%s\r\n' % (len(data), data)
         self.wfile.write(data)
         self.wfile.flush()
 
     def _done(self):
         if self._chunked:
             self.wfile.write('0\r\n\r\n')
             self.wfile.flush()
 
     def version_string(self):
         if self.server.serverheader:
             return encoding.strfromlocal(self.server.serverheader)
         return httpservermod.basehttprequesthandler.version_string(self)
 
 class _httprequesthandlerssl(_httprequesthandler):
     """HTTPS handler based on Python's ssl module"""
 
     url_scheme = 'https'
 
     @staticmethod
     def preparehttpserver(httpserver, ui):
         try:
             from .. import sslutil
             sslutil.modernssl
         except ImportError:
             raise error.Abort(_("SSL support is unavailable"))
 
         certfile = ui.config('web', 'certificate')
 
         # These config options are currently only meant for testing. Use
         # at your own risk.
         cafile = ui.config('devel', 'servercafile')
         reqcert = ui.configbool('devel', 'serverrequirecert')
 
         httpserver.socket = sslutil.wrapserversocket(httpserver.socket,
                                                      ui,
                                                      certfile=certfile,
                                                      cafile=cafile,
                                                      requireclientcert=reqcert)
 
     def setup(self):
         self.connection = self.request
         self.rfile = self.request.makefile(r"rb", self.rbufsize)
         self.wfile = self.request.makefile(r"wb", self.wbufsize)
 
 try:
     import threading
     threading.activeCount() # silence pyflakes and bypass demandimport
     _mixin = socketserver.ThreadingMixIn
 except ImportError:
     if util.safehasattr(os, "fork"):
         _mixin = socketserver.ForkingMixIn
     else:
         class _mixin(object):
             pass
 
 def openlog(opt, default):
     if opt and opt != '-':
         return open(opt, 'ab')
     return default
 
 class MercurialHTTPServer(_mixin, httpservermod.httpserver, object):
 
     # SO_REUSEADDR has broken semantics on windows
     if pycompat.iswindows:
         allow_reuse_address = 0
 
     def __init__(self, ui, app, addr, handler, **kwargs):
         httpservermod.httpserver.__init__(self, addr, handler, **kwargs)
         self.daemon_threads = True
         self.application = app
 
         handler.preparehttpserver(self, ui)
 
         prefix = ui.config('web', 'prefix')
         if prefix:
             prefix = '/' + prefix.strip('/')
         self.prefix = prefix
 
         alog = openlog(ui.config('web', 'accesslog'), ui.fout)
         elog = openlog(ui.config('web', 'errorlog'), ui.ferr)
         self.accesslog = alog
         self.errorlog = elog
 
         self.addr, self.port = self.socket.getsockname()[0:2]
         self.fqaddr = socket.getfqdn(addr[0])
 
         self.serverheader = ui.config('web', 'server-header')
 
 class IPv6HTTPServer(MercurialHTTPServer):
     address_family = getattr(socket, 'AF_INET6', None)
     def __init__(self, *args, **kwargs):
         if self.address_family is None:
             raise error.RepoError(_('IPv6 is not available on this system'))
         super(IPv6HTTPServer, self).__init__(*args, **kwargs)
 
 def create_server(ui, app):
 
     if ui.config('web', 'certificate'):
         handler = _httprequesthandlerssl
     else:
         handler = _httprequesthandler
 
     if ui.configbool('web', 'ipv6'):
         cls = IPv6HTTPServer
     else:
         cls = MercurialHTTPServer
 
     # ugly hack due to python issue5853 (for threaded use)
     try:
         import mimetypes
         mimetypes.init()
     except UnicodeDecodeError:
         # Python 2.x's mimetypes module attempts to decode strings
         # from Windows' ANSI APIs as ascii (fail), then re-encode them
         # as ascii (clown fail), because the default Python Unicode
         # codec is hardcoded as ascii.
 
         sys.argv # unwrap demand-loader so that reload() works
         reload(sys) # resurrect sys.setdefaultencoding()
         oldenc = sys.getdefaultencoding()
         sys.setdefaultencoding("latin1") # or any full 8-bit encoding
         mimetypes.init()
         sys.setdefaultencoding(oldenc)
 
     address = ui.config('web', 'address')
     port = util.getport(ui.config('web', 'port'))
     try:
         return cls(ui, app, (address, port), handler)
     except socket.error as inst:
         raise error.Abort(_("cannot start server at '%s:%d': %s")
                           % (address, port, encoding.strtolocal(inst.args[1])))