mercurial/url.py

url: verify correctness of https server certificates (issue2407)

Pythons SSL module verifies that certificates received for HTTPS are valid
according to the specified cacerts, but it doesn't verify that the certificate
is for the host we connect to.

We now explicitly verify that the commonName in the received certificate
matches the requested hostname and is valid for the time being.

This is a minimal patch where we try to fail to the safe side, but we do still
rely on Python's SSL functionality and do not try to implement the standards
fully and correctly. CRLs and subjectAltName are not handled and proxies
haven't been considered.

This change might break connections to some sites if cacerts is specified and
the certificates (by our definition) isn't correct. The workaround is to
disable cacerts which in most cases isn't much worse than it was before with
cacerts.

# 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.

import urllib, urllib2, urlparse, httplib, os, re, socket, cStringIO, time
from i18n import _
import keepalive, util

def _urlunparse(scheme, netloc, path, params, query, fragment, url):
    '''Handle cases where urlunparse(urlparse(x://)) doesn't preserve the "//"'''
    result = urlparse.urlunparse((scheme, netloc, path, params, query, fragment))
    if (scheme and
        result.startswith(scheme + ':') and
        not result.startswith(scheme + '://') and
        url.startswith(scheme + '://')
       ):
        result = scheme + '://' + result[len(scheme + ':'):]
    return result

def hidepassword(url):
    '''hide user credential in a url string'''
    scheme, netloc, path, params, query, fragment = urlparse.urlparse(url)
    netloc = re.sub('([^:]*):([^@]*)@(.*)', r'\1:***@\3', netloc)
    return _urlunparse(scheme, netloc, path, params, query, fragment, url)

def removeauth(url):
    '''remove all authentication information from a url string'''
    scheme, netloc, path, params, query, fragment = urlparse.urlparse(url)
    netloc = netloc[netloc.find('@')+1:]
    return _urlunparse(scheme, netloc, path, params, query, fragment, url)

def netlocsplit(netloc):
    '''split [user[:passwd]@]host[:port] into 4-tuple.'''

    a = netloc.find('@')
    if a == -1:
        user, passwd = None, None
    else:
        userpass, netloc = netloc[:a], netloc[a + 1:]
        c = userpass.find(':')
        if c == -1:
            user, passwd = urllib.unquote(userpass), None
        else:
            user = urllib.unquote(userpass[:c])
            passwd = urllib.unquote(userpass[c + 1:])
    c = netloc.find(':')
    if c == -1:
        host, port = netloc, None
    else:
        host, port = netloc[:c], netloc[c + 1:]
    return host, port, user, passwd

def netlocunsplit(host, port, user=None, passwd=None):
    '''turn host, port, user, passwd into [user[:passwd]@]host[:port].'''
    if port:
        hostport = host + ':' + port
    else:
        hostport = host
    if user:
        quote = lambda s: urllib.quote(s, safe='')
        if passwd:
            userpass = quote(user) + ':' + quote(passwd)
        else:
            userpass = quote(user)
        return userpass + '@' + hostport
    return hostport

_safe = ('abcdefghijklmnopqrstuvwxyz'
         'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
         '0123456789' '_.-/')
_safeset = None
_hex = None
def quotepath(path):
    '''quote the path part of a URL

    This is similar to urllib.quote, but it also tries to avoid
    quoting things twice (inspired by wget):

    >>> quotepath('abc def')
    'abc%20def'
    >>> quotepath('abc%20def')
    'abc%20def'
    >>> quotepath('abc%20 def')
    'abc%20%20def'
    >>> quotepath('abc def%20')
    'abc%20def%20'
    >>> quotepath('abc def%2')
    'abc%20def%252'
    >>> quotepath('abc def%')
    'abc%20def%25'
    '''
    global _safeset, _hex
    if _safeset is None:
        _safeset = set(_safe)
        _hex = set('abcdefABCDEF0123456789')
    l = list(path)
    for i in xrange(len(l)):
        c = l[i]
        if (c == '%' and i + 2 < len(l) and
            l[i + 1] in _hex and l[i + 2] in _hex):
            pass
        elif c not in _safeset:
            l[i] = '%%%02X' % ord(c)
    return ''.join(l)

class passwordmgr(urllib2.HTTPPasswordMgrWithDefaultRealm):
    def __init__(self, ui):
        urllib2.HTTPPasswordMgrWithDefaultRealm.__init__(self)
        self.ui = ui

    def find_user_password(self, realm, authuri):
        authinfo = urllib2.HTTPPasswordMgrWithDefaultRealm.find_user_password(
            self, realm, authuri)
        user, passwd = authinfo
        if user and passwd:
            self._writedebug(user, passwd)
            return (user, passwd)

        if not user:
            auth = self.readauthtoken(authuri)
            if auth:
                user, passwd = auth.get('username'), auth.get('password')
        if not user or not passwd:
            if not self.ui.interactive():
                raise util.Abort(_('http authorization required'))

            self.ui.write(_("http authorization required\n"))
            self.ui.status(_("realm: %s\n") % realm)
            if user:
                self.ui.status(_("user: %s\n") % user)
            else:
                user = self.ui.prompt(_("user:"), default=None)

            if not passwd:
                passwd = self.ui.getpass()

        self.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 readauthtoken(self, uri):
        # Read configuration
        config = dict()
        for key, val in self.ui.configitems('auth'):
            if '.' not in key:
                self.ui.warn(_("ignoring invalid [auth] key '%s'\n") % key)
                continue
            group, setting = key.split('.', 1)
            gdict = config.setdefault(group, dict())
            if setting in ('username', 'cert', 'key'):
                val = util.expandpath(val)
            gdict[setting] = val

        # Find the best match
        scheme, hostpath = uri.split('://', 1)
        bestlen = 0
        bestauth = None
        for auth in config.itervalues():
            prefix = auth.get('prefix')
            if not prefix:
                continue
            p = prefix.split('://', 1)
            if len(p) > 1:
                schemes, prefix = [p[0]], p[1]
            else:
                schemes = (auth.get('schemes') or 'https').split()
            if (prefix == '*' or hostpath.startswith(prefix)) and \
                len(prefix) > bestlen and scheme in schemes:
                bestlen = len(prefix)
                bestauth = auth
        return bestauth

class proxyhandler(urllib2.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 + '/'
            snpqf = urlparse.urlsplit(proxyurl)
            proxyscheme, proxynetloc, proxypath, proxyquery, proxyfrag = snpqf
            hpup = netlocsplit(proxynetloc)

            proxyhost, proxyport, proxyuser, proxypasswd = hpup
            if not proxyuser:
                proxyuser = ui.config("http_proxy", "user")
                proxypasswd = 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 = urlparse.urlunsplit((
                proxyscheme, netlocunsplit(proxyhost, proxyport,
                                                proxyuser, proxypasswd or ''),
                proxypath, proxyquery, proxyfrag))
            proxies = {'http': proxyurl, 'https': proxyurl}
            ui.debug('proxying through http://%s:%s\n' %
                      (proxyhost, proxyport))
        else:
            proxies = {}

        # urllib2 takes proxy values from the environment and those
        # will take precedence if found, so drop them
        for env in ["HTTP_PROXY", "http_proxy", "no_proxy"]:
            try:
                if env in os.environ:
                    del os.environ[env]
            except OSError:
                pass

        urllib2.ProxyHandler.__init__(self, proxies)
        self.ui = ui

    def proxy_open(self, req, proxy, type_):
        host = req.get_host().split(':')[0]
        if host in self.no_list:
            return None

        # work around a bug in Python < 2.4.2
        # (it leaves a "\n" at the end of Proxy-authorization headers)
        baseclass = req.__class__
        class _request(baseclass):
            def add_header(self, key, val):
                if key.lower() == 'proxy-authorization':
                    val = val.strip()
                return baseclass.add_header(self, key, val)
        req.__class__ = _request

        return urllib2.ProxyHandler.proxy_open(self, req, proxy, type_)

class httpsendfile(file):
    def __len__(self):
        return os.fstat(self.fileno()).st_size

def _gen_sendfile(connection):
    def _sendfile(self, data):
        # send a file
        if isinstance(data, httpsendfile):
            # if auth required, some data sent twice, so rewind here
            data.seek(0)
            for chunk in util.filechunkiter(data):
                connection.send(self, chunk)
        else:
            connection.send(self, data)
    return _sendfile

has_https = hasattr(urllib2, 'HTTPSHandler')
if has_https:
    try:
        # avoid using deprecated/broken FakeSocket in python 2.6
        import ssl
        _ssl_wrap_socket = ssl.wrap_socket
        CERT_REQUIRED = ssl.CERT_REQUIRED
    except ImportError:
        CERT_REQUIRED = 2

        def _ssl_wrap_socket(sock, key_file, cert_file,
                             cert_reqs=CERT_REQUIRED, ca_certs=None):
            if ca_certs:
                raise util.Abort(_(
                    'certificate checking requires Python 2.6'))

            ssl = socket.ssl(sock, key_file, cert_file)
            return httplib.FakeSocket(sock, ssl)

    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, 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)

    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 x509 certificates
                self.sock = _ssl_wrap_socket(self.sock, None, None)
        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):
    if hasattr(req, '_tunnel_host') and req._tunnel_host:
        tunnel_host = req._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
        urlparts = urlparse.urlparse(tunnel_host)
        if new_tunnel or urlparts[0] == 'https': # only use CONNECT for HTTPS
            realhostport = urlparts[1]
            if realhostport[-1] == ']' or ':' not in realhostport:
                realhostport += ':443'

            h.realhostport = realhostport
            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._set_hostport(self.host, self.port)
    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(cStringIO.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, S4.4, #3 says we ignore this if tr_enc 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)

def _verifycert(cert, hostname):
    '''Verify that cert (in socket.getpeercert() format) matches hostname and is 
    valid at this time. CRLs and subjectAltName are not handled.
    
    Returns error message if any problems are found and None on success.
    '''
    if not cert:
        return _('no certificate received')
    notafter = cert.get('notAfter')
    if notafter and time.time() > ssl.cert_time_to_seconds(notafter):
        return _('certificate expired %s') % notafter
    notbefore = cert.get('notBefore')
    if notbefore and time.time() < ssl.cert_time_to_seconds(notbefore):
        return _('certificate not valid before %s') % notbefore
    dnsname = hostname.lower()
    for s in cert.get('subject', []):
        key, value = s[0]
        if key == 'commonName':
            certname = value.lower()
            if (certname == dnsname or
                '.' in dnsname and certname == '*.' + dnsname.split('.', 1)[1]):
                return None
            return _('certificate is for %s') % certname
    return _('no commonName found in certificate')

if has_https:
    class BetterHTTPS(httplib.HTTPSConnection):
        send = keepalive.safesend

        def connect(self):
            if hasattr(self, 'ui'):
                cacerts = self.ui.config('web', 'cacerts')
            else:
                cacerts = None

            if cacerts:
                sock = _create_connection((self.host, self.port))
                self.sock = _ssl_wrap_socket(sock, self.key_file,
                        self.cert_file, cert_reqs=CERT_REQUIRED,
                        ca_certs=cacerts)
                msg = _verifycert(self.sock.getpeercert(), self.host)
                if msg:
                    raise util.Abort('%s certificate error: %s' % (self.host, msg))
                self.ui.debug(_('%s certificate successfully verified\n') % 
                    self.host)
            else:
                httplib.HTTPSConnection.connect(self)

    class httpsconnection(BetterHTTPS):
        response_class = keepalive.HTTPResponse
        # must be able to send big bundle as stream.
        send = _gen_sendfile(BetterHTTPS)
        getresponse = keepalive.wrapgetresponse(httplib.HTTPSConnection)

        def connect(self):
            if 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):
                    self.sock = _ssl_wrap_socket(self.sock, self.cert_file,
                                                 self.key_file)
            else:
                BetterHTTPS.connect(self)

    class httpshandler(keepalive.KeepAliveHandler, urllib2.HTTPSHandler):
        def __init__(self, ui):
            keepalive.KeepAliveHandler.__init__(self)
            urllib2.HTTPSHandler.__init__(self)
            self.ui = ui
            self.pwmgr = passwordmgr(self.ui)

        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):
            self.auth = self.pwmgr.readauthtoken(req.get_full_url())
            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(urllib2.HTTPDigestAuthHandler):
    def __init__(self, *args, **kwargs):
        urllib2.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
        # In python < 2.5 AbstractDigestAuthHandler raises a ValueError if
        # it doesn't know about the auth type requested. This can happen if
        # somebody is using BasicAuth and types a bad password.
        try:
            return urllib2.HTTPDigestAuthHandler.http_error_auth_reqed(
                        self, auth_header, host, req, headers)
        except ValueError, inst:
            arg = inst.args[0]
            if arg.startswith("AbstractDigestAuthHandler doesn't know "):
                return
            raise

class httpbasicauthhandler(urllib2.HTTPBasicAuthHandler):
    def __init__(self, *args, **kwargs):
        urllib2.HTTPBasicAuthHandler.__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 urllib2.HTTPBasicAuthHandler.http_error_auth_reqed(
                        self, auth_header, host, req, headers)

def getauthinfo(path):
    scheme, netloc, urlpath, query, frag = urlparse.urlsplit(path)
    if not urlpath:
        urlpath = '/'
    if scheme != 'file':
        # XXX: why are we quoting the path again with some smart
        # heuristic here? Anyway, it cannot be done with file://
        # urls since path encoding is os/fs dependent (see
        # urllib.pathname2url() for details).
        urlpath = quotepath(urlpath)
    host, port, user, passwd = netlocsplit(netloc)

    # urllib cannot handle URLs with embedded user or passwd
    url = urlparse.urlunsplit((scheme, netlocunsplit(host, port),
                              urlpath, query, frag))
    if user:
        netloc = host
        if port:
            netloc += ':' + port
        # Python < 2.4.3 uses only the netloc to search for a password
        authinfo = (None, (url, netloc), user, passwd or '')
    else:
        authinfo = None
    return url, authinfo

handlerfuncs = []

def opener(ui, authinfo=None):
    '''
    construct an opener suitable for urllib2
    authinfo will be added to the password manager
    '''
    handlers = [httphandler()]
    if has_https:
        handlers.append(httpshandler(ui))

    handlers.append(proxyhandler(ui))

    passmgr = passwordmgr(ui)
    if authinfo is not None:
        passmgr.add_password(*authinfo)
        user, passwd = authinfo[2:4]
        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 = urllib2.build_opener(*handlers)

    # 1.0 here is the _protocol_ version
    opener.addheaders = [('User-agent', 'mercurial/proto-1.0')]
    opener.addheaders.append(('Accept', 'application/mercurial-0.1'))
    return opener

scheme_re = re.compile(r'^([a-zA-Z0-9+-.]+)://')

def open(ui, url, data=None):
    scheme = None
    m = scheme_re.search(url)
    if m:
        scheme = m.group(1).lower()
    if not scheme:
        path = util.normpath(os.path.abspath(url))
        url = 'file://' + urllib.pathname2url(path)
        authinfo = None
    else:
        url, authinfo = getauthinfo(url)
    return opener(ui, authinfo).open(url, data)