url: add distribution and version to user-agent request header (BC)

As a server operator, I've always wanted to know what Mercurial
version clients are running so I can track version adoption and
make informed decisions about which versions of Mercurial to
support in extensions. Unfortunately, there is no easy way to discern
this today: the best you can do is look for high-level feature usage
(e.g. bundle2) or sniff capabilities from bundle2 commands. And these
things aren't changed frequently enough to tell you anything that
interesting.

Nearly every piece of software talking HTTP sends its version in
the user agent. This includes web browsers, curl, and even Git.

This patch adds the distribution name and version to the user-agent
HTTP request header. We choose "Mercurial" for the distribution
name because that seems appropriate. The version string comes
from __version__.

The value is inside parenthesis for a few reasons:

* The version *may* contain spaces
* Alternate forms like "Mercurial/<version>" imply structure and
  since the user agent should not be used by servers for protocol
  or feature negotiation/detection, we don't want to even give the
  illusion that the value should be parsed. A free form field is
  the most hostile to parsing.

Flagging the patch as BC so it shows up in release notes. This
change should be backwards compatible. But I wouldn't be surprised if
a server somewhere is filtering on the exact old user agent string. So
I want to make noise about this change.

mercurial/url.py

@@ -1,522 +1,534
 # url.py - HTTP handling for mercurial
 #
 # Copyright 2005, 2006, 2007, 2008 Matt Mackall <[e-mail]>
 # Copyright 2006, 2007 Alexis S. L. Carvalho <[e-mail]>
 # Copyright 2006 Vadim Gelfer <[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 base64
 import os
 import socket
 
 from .i18n import _
 from . import (
     error,
     httpconnection as httpconnectionmod,
     keepalive,
     sslutil,
     util,
 )
 
 httplib = util.httplib
 stringio = util.stringio
 urlerr = util.urlerr
 urlreq = util.urlreq
 
 class passwordmgr(object):
     def __init__(self, ui, passwddb):
         self.ui = ui
         self.passwddb = passwddb
 
     def add_password(self, realm, uri, user, passwd):
         return self.passwddb.add_password(realm, uri, user, passwd)
 
     def find_user_password(self, realm, authuri):
         authinfo = self.passwddb.find_user_password(realm, authuri)
         user, passwd = authinfo
         if user and passwd:
             self._writedebug(user, passwd)
             return (user, passwd)
 
         if not user or not passwd:
             res = httpconnectionmod.readauthforuri(self.ui, authuri, user)
             if res:
                 group, auth = res
                 user, passwd = auth.get('username'), auth.get('password')
                 self.ui.debug("using auth.%s.* for authentication\n" % group)
         if not user or not passwd:
             u = util.url(authuri)
             u.query = None
             if not self.ui.interactive():
                 raise error.Abort(_('http authorization required for %s') %
                                  util.hidepassword(str(u)))
 
             self.ui.write(_("http authorization required for %s\n") %
                           util.hidepassword(str(u)))
             self.ui.write(_("realm: %s\n") % realm)
             if user:
                 self.ui.write(_("user: %s\n") % user)
             else:
                 user = self.ui.prompt(_("user:"), default=None)
 
             if not passwd:
                 passwd = self.ui.getpass()
 
         self.passwddb.add_password(realm, authuri, user, passwd)
         self._writedebug(user, passwd)
         return (user, passwd)
 
     def _writedebug(self, user, passwd):
         msg = _('http auth: user %s, password %s\n')
         self.ui.debug(msg % (user, passwd and '*' * len(passwd) or 'not set'))
 
     def find_stored_password(self, authuri):
         return self.passwddb.find_user_password(None, authuri)
 
 class proxyhandler(urlreq.proxyhandler):
     def __init__(self, ui):
         proxyurl = ui.config("http_proxy", "host") or os.getenv('http_proxy')
         # XXX proxyauthinfo = None
 
         if proxyurl:
             # proxy can be proper url or host[:port]
             if not (proxyurl.startswith('http:') or
                     proxyurl.startswith('https:')):
                 proxyurl = 'http://' + proxyurl + '/'
             proxy = util.url(proxyurl)
             if not proxy.user:
                 proxy.user = ui.config("http_proxy", "user")
                 proxy.passwd = ui.config("http_proxy", "passwd")
 
             # see if we should use a proxy for this url
             no_list = ["localhost", "127.0.0.1"]
             no_list.extend([p.lower() for
                             p in ui.configlist("http_proxy", "no")])
             no_list.extend([p.strip().lower() for
                             p in os.getenv("no_proxy", '').split(',')
                             if p.strip()])
             # "http_proxy.always" config is for running tests on localhost
             if ui.configbool("http_proxy", "always"):
                 self.no_list = []
             else:
                 self.no_list = no_list
 
             proxyurl = str(proxy)
             proxies = {'http': proxyurl, 'https': proxyurl}
             ui.debug('proxying through http://%s:%s\n' %
                       (proxy.host, proxy.port))
         else:
             proxies = {}
 
         # urllib2 takes proxy values from the environment and those
         # will take precedence if found. So, if there's a config entry
         # defining a proxy, drop the environment ones
         if ui.config("http_proxy", "host"):
             for env in ["HTTP_PROXY", "http_proxy", "no_proxy"]:
                 try:
                     if env in os.environ:
                         del os.environ[env]
                 except OSError:
                     pass
 
         urlreq.proxyhandler.__init__(self, proxies)
         self.ui = ui
 
     def proxy_open(self, req, proxy, type_):
         host = req.get_host().split(':')[0]
         for e in self.no_list:
             if host == e:
                 return None
             if e.startswith('*.') and host.endswith(e[2:]):
                 return None
             if e.startswith('.') and host.endswith(e[1:]):
                 return None
 
         return urlreq.proxyhandler.proxy_open(self, req, proxy, type_)
 
 def _gen_sendfile(orgsend):
     def _sendfile(self, data):
         # send a file
         if isinstance(data, httpconnectionmod.httpsendfile):
             # if auth required, some data sent twice, so rewind here
             data.seek(0)
             for chunk in util.filechunkiter(data):
                 orgsend(self, chunk)
         else:
             orgsend(self, data)
     return _sendfile
 
 has_https = util.safehasattr(urlreq, 'httpshandler')
 if has_https:
     try:
         _create_connection = socket.create_connection
     except AttributeError:
         _GLOBAL_DEFAULT_TIMEOUT = object()
 
         def _create_connection(address, timeout=_GLOBAL_DEFAULT_TIMEOUT,
                                source_address=None):
             # lifted from Python 2.6
 
             msg = "getaddrinfo returns an empty list"
             host, port = address
             for res in socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM):
                 af, socktype, proto, canonname, sa = res
                 sock = None
                 try:
                     sock = socket.socket(af, socktype, proto)
                     if timeout is not _GLOBAL_DEFAULT_TIMEOUT:
                         sock.settimeout(timeout)
                     if source_address:
                         sock.bind(source_address)
                     sock.connect(sa)
                     return sock
 
                 except socket.error as msg:
                     if sock is not None:
                         sock.close()
 
             raise socket.error(msg)
 
 class httpconnection(keepalive.HTTPConnection):
     # must be able to send big bundle as stream.
     send = _gen_sendfile(keepalive.HTTPConnection.send)
 
     def connect(self):
         if has_https and self.realhostport: # use CONNECT proxy
             self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
             self.sock.connect((self.host, self.port))
             if _generic_proxytunnel(self):
                 # we do not support client X.509 certificates
                 self.sock = sslutil.wrapsocket(self.sock, None, None, None,
                                                serverhostname=self.host)
         else:
             keepalive.HTTPConnection.connect(self)
 
     def getresponse(self):
         proxyres = getattr(self, 'proxyres', None)
         if proxyres:
             if proxyres.will_close:
                 self.close()
             self.proxyres = None
             return proxyres
         return keepalive.HTTPConnection.getresponse(self)
 
 # general transaction handler to support different ways to handle
 # HTTPS proxying before and after Python 2.6.3.
 def _generic_start_transaction(handler, h, req):
     tunnel_host = getattr(req, '_tunnel_host', None)
     if tunnel_host:
         if tunnel_host[:7] not in ['http://', 'https:/']:
             tunnel_host = 'https://' + tunnel_host
         new_tunnel = True
     else:
         tunnel_host = req.get_selector()
         new_tunnel = False
 
     if new_tunnel or tunnel_host == req.get_full_url(): # has proxy
         u = util.url(tunnel_host)
         if new_tunnel or u.scheme == 'https': # only use CONNECT for HTTPS
             h.realhostport = ':'.join([u.host, (u.port or '443')])
             h.headers = req.headers.copy()
             h.headers.update(handler.parent.addheaders)
             return
 
     h.realhostport = None
     h.headers = None
 
 def _generic_proxytunnel(self):
     proxyheaders = dict(
             [(x, self.headers[x]) for x in self.headers
              if x.lower().startswith('proxy-')])
     self.send('CONNECT %s HTTP/1.0\r\n' % self.realhostport)
     for header in proxyheaders.iteritems():
         self.send('%s: %s\r\n' % header)
     self.send('\r\n')
 
     # majority of the following code is duplicated from
     # httplib.HTTPConnection as there are no adequate places to
     # override functions to provide the needed functionality
     res = self.response_class(self.sock,
                               strict=self.strict,
                               method=self._method)
 
     while True:
         version, status, reason = res._read_status()
         if status != httplib.CONTINUE:
             break
         while True:
             skip = res.fp.readline().strip()
             if not skip:
                 break
     res.status = status
     res.reason = reason.strip()
 
     if res.status == 200:
         while True:
             line = res.fp.readline()
             if line == '\r\n':
                 break
         return True
 
     if version == 'HTTP/1.0':
         res.version = 10
     elif version.startswith('HTTP/1.'):
         res.version = 11
     elif version == 'HTTP/0.9':
         res.version = 9
     else:
         raise httplib.UnknownProtocol(version)
 
     if res.version == 9:
         res.length = None
         res.chunked = 0
         res.will_close = 1
         res.msg = httplib.HTTPMessage(stringio())
         return False
 
     res.msg = httplib.HTTPMessage(res.fp)
     res.msg.fp = None
 
     # are we using the chunked-style of transfer encoding?
     trenc = res.msg.getheader('transfer-encoding')
     if trenc and trenc.lower() == "chunked":
         res.chunked = 1
         res.chunk_left = None
     else:
         res.chunked = 0
 
     # will the connection close at the end of the response?
     res.will_close = res._check_close()
 
     # do we have a Content-Length?
     # NOTE: RFC 2616, section 4.4, #3 says we ignore this if
     # transfer-encoding is "chunked"
     length = res.msg.getheader('content-length')
     if length and not res.chunked:
         try:
             res.length = int(length)
         except ValueError:
             res.length = None
         else:
             if res.length < 0:  # ignore nonsensical negative lengths
                 res.length = None
     else:
         res.length = None
 
     # does the body have a fixed length? (of zero)
     if (status == httplib.NO_CONTENT or status == httplib.NOT_MODIFIED or
         100 <= status < 200 or # 1xx codes
         res._method == 'HEAD'):
         res.length = 0
 
     # if the connection remains open, and we aren't using chunked, and
     # a content-length was not provided, then assume that the connection
     # WILL close.
     if (not res.will_close and
        not res.chunked and
        res.length is None):
         res.will_close = 1
 
     self.proxyres = res
 
     return False
 
 class httphandler(keepalive.HTTPHandler):
     def http_open(self, req):
         return self.do_open(httpconnection, req)
 
     def _start_transaction(self, h, req):
         _generic_start_transaction(self, h, req)
         return keepalive.HTTPHandler._start_transaction(self, h, req)
 
 if has_https:
     class httpsconnection(httplib.HTTPConnection):
         response_class = keepalive.HTTPResponse
         default_port = httplib.HTTPS_PORT
         # must be able to send big bundle as stream.
         send = _gen_sendfile(keepalive.safesend)
         getresponse = keepalive.wrapgetresponse(httplib.HTTPConnection)
 
         def __init__(self, host, port=None, key_file=None, cert_file=None,
                      *args, **kwargs):
             httplib.HTTPConnection.__init__(self, host, port, *args, **kwargs)
             self.key_file = key_file
             self.cert_file = cert_file
 
         def connect(self):
             self.sock = _create_connection((self.host, self.port))
 
             host = self.host
             if self.realhostport: # use CONNECT proxy
                 _generic_proxytunnel(self)
                 host = self.realhostport.rsplit(':', 1)[0]
             self.sock = sslutil.wrapsocket(
                 self.sock, self.key_file, self.cert_file, ui=self.ui,
                 serverhostname=host)
             sslutil.validatesocket(self.sock)
 
     class httpshandler(keepalive.KeepAliveHandler, urlreq.httpshandler):
         def __init__(self, ui):
             keepalive.KeepAliveHandler.__init__(self)
             urlreq.httpshandler.__init__(self)
             self.ui = ui
             self.pwmgr = passwordmgr(self.ui,
                                      self.ui.httppasswordmgrdb)
 
         def _start_transaction(self, h, req):
             _generic_start_transaction(self, h, req)
             return keepalive.KeepAliveHandler._start_transaction(self, h, req)
 
         def https_open(self, req):
             # req.get_full_url() does not contain credentials and we may
             # need them to match the certificates.
             url = req.get_full_url()
             user, password = self.pwmgr.find_stored_password(url)
             res = httpconnectionmod.readauthforuri(self.ui, url, user)
             if res:
                 group, auth = res
                 self.auth = auth
                 self.ui.debug("using auth.%s.* for authentication\n" % group)
             else:
                 self.auth = None
             return self.do_open(self._makeconnection, req)
 
         def _makeconnection(self, host, port=None, *args, **kwargs):
             keyfile = None
             certfile = None
 
             if len(args) >= 1: # key_file
                 keyfile = args[0]
             if len(args) >= 2: # cert_file
                 certfile = args[1]
             args = args[2:]
 
             # if the user has specified different key/cert files in
             # hgrc, we prefer these
             if self.auth and 'key' in self.auth and 'cert' in self.auth:
                 keyfile = self.auth['key']
                 certfile = self.auth['cert']
 
             conn = httpsconnection(host, port, keyfile, certfile, *args,
                                    **kwargs)
             conn.ui = self.ui
             return conn
 
 class httpdigestauthhandler(urlreq.httpdigestauthhandler):
     def __init__(self, *args, **kwargs):
         urlreq.httpdigestauthhandler.__init__(self, *args, **kwargs)
         self.retried_req = None
 
     def reset_retry_count(self):
         # Python 2.6.5 will call this on 401 or 407 errors and thus loop
         # forever. We disable reset_retry_count completely and reset in
         # http_error_auth_reqed instead.
         pass
 
     def http_error_auth_reqed(self, auth_header, host, req, headers):
         # Reset the retry counter once for each request.
         if req is not self.retried_req:
             self.retried_req = req
             self.retried = 0
         return urlreq.httpdigestauthhandler.http_error_auth_reqed(
                     self, auth_header, host, req, headers)
 
 class httpbasicauthhandler(urlreq.httpbasicauthhandler):
     def __init__(self, *args, **kwargs):
         self.auth = None
         urlreq.httpbasicauthhandler.__init__(self, *args, **kwargs)
         self.retried_req = None
 
     def http_request(self, request):
         if self.auth:
             request.add_unredirected_header(self.auth_header, self.auth)
 
         return request
 
     def https_request(self, request):
         if self.auth:
             request.add_unredirected_header(self.auth_header, self.auth)
 
         return request
 
     def reset_retry_count(self):
         # Python 2.6.5 will call this on 401 or 407 errors and thus loop
         # forever. We disable reset_retry_count completely and reset in
         # http_error_auth_reqed instead.
         pass
 
     def http_error_auth_reqed(self, auth_header, host, req, headers):
         # Reset the retry counter once for each request.
         if req is not self.retried_req:
             self.retried_req = req
             self.retried = 0
         return urlreq.httpbasicauthhandler.http_error_auth_reqed(
                         self, auth_header, host, req, headers)
 
     def retry_http_basic_auth(self, host, req, realm):
         user, pw = self.passwd.find_user_password(realm, req.get_full_url())
         if pw is not None:
             raw = "%s:%s" % (user, pw)
             auth = 'Basic %s' % base64.b64encode(raw).strip()
             if req.headers.get(self.auth_header, None) == auth:
                 return None
             self.auth = auth
             req.add_unredirected_header(self.auth_header, auth)
             return self.parent.open(req)
         else:
             return None
 
 handlerfuncs = []
 
 def opener(ui, authinfo=None):
     '''
     construct an opener suitable for urllib2
     authinfo will be added to the password manager
     '''
     # experimental config: ui.usehttp2
     if ui.configbool('ui', 'usehttp2', False):
         handlers = [
             httpconnectionmod.http2handler(
                 ui,
                 passwordmgr(ui, ui.httppasswordmgrdb))
         ]
     else:
         handlers = [httphandler()]
         if has_https:
             handlers.append(httpshandler(ui))
 
     handlers.append(proxyhandler(ui))
 
     passmgr = passwordmgr(ui, ui.httppasswordmgrdb)
     if authinfo is not None:
         realm, uris, user, passwd = authinfo
         saveduser, savedpass = passmgr.find_stored_password(uris[0])
         if user != saveduser or passwd:
             passmgr.add_password(realm, uris, user, passwd)
         ui.debug('http auth: user %s, password %s\n' %
                  (user, passwd and '*' * len(passwd) or 'not set'))
 
     handlers.extend((httpbasicauthhandler(passmgr),
                      httpdigestauthhandler(passmgr)))
     handlers.extend([h(ui, passmgr) for h in handlerfuncs])
     opener = urlreq.buildopener(*handlers)
 
-    # 1.0 here is the _protocol_ version
-    opener.addheaders = [('User-agent', 'mercurial/proto-1.0')]
+    # The user agent should should *NOT* be used by servers for e.g.
+    # protocol detection or feature negotiation: there are other
+    # facilities for that.
+    #
+    # "mercurial/proto-1.0" was the original user agent string and
+    # exists for backwards compatibility reasons.
+    #
+    # The "(Mercurial %s)" string contains the distribution
+    # name and version. Other client implementations should choose their
+    # own distribution name. Since servers should not be using the user
+    # agent string for anything, clients should be able to define whatever
+    # user agent they deem appropriate.
+    agent = 'mercurial/proto-1.0 (Mercurial %s)' % util.version()
+    opener.addheaders = [('User-agent', agent)]
     opener.addheaders.append(('Accept', 'application/mercurial-0.1'))
     return opener
 
 def open(ui, url_, data=None):
     u = util.url(url_)
     if u.scheme:
         u.scheme = u.scheme.lower()
         url_, authinfo = u.authinfo()
     else:
         path = util.normpath(os.path.abspath(url_))
         url_ = 'file://' + urlreq.pathname2url(path)
         authinfo = None
     return opener(ui, authinfo).open(url_, data)