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+# Copyright (c) 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""
+A http client with support for https connections with certificate verification.
+
+The verification is based on http://tools.ietf.org/html/rfc6125#section-6.4.3
+and the code is from Lib/ssl.py in python3:
+ http://hg.python.org/cpython/file/4dac45f88d45/Lib/ssl.py
+
+One use case is to download Chromium DEPS file in a secure way:
+ https://src.chromium.org/chrome/trunk/src/DEPS
+
+Notice: python 2.7 or newer is required.
+"""
+
+import cookielib
+import httplib
+import os
+import re
+import socket
+import ssl
+import urllib
+import urllib2
+
+import http_client
+
+
+_SCRIPT_DIR = os.path.dirname(__file__)
+_TRUSTED_ROOT_CERTS = os.path.join(_SCRIPT_DIR, 'cacert.pem')
+
+
+class CertificateError(ValueError):
+ pass
+
+
+def _DNSNameMatch(dn, hostname, max_wildcards=1):
+ """Matching according to RFC 6125, section 6.4.3
+
+ http://tools.ietf.org/html/rfc6125#section-6.4.3
+ """
+ pats = []
+ if not dn:
+ return False
+
+ parts = dn.split(r'.')
+ leftmost = parts[0]
+ remainder = parts[1:]
+
+ wildcards = leftmost.count('*')
+ if wildcards > max_wildcards:
+ # Issue #17980: avoid denials of service by refusing more
+ # than one wildcard per fragment. A survery of established
+ # policy among SSL implementations showed it to be a
+ # reasonable choice.
+ raise CertificateError(
+ 'too many wildcards in certificate DNS name: ' + repr(dn))
+
+ # speed up common case w/o wildcards
+ if not wildcards:
+ return dn.lower() == hostname.lower()
+
+ # RFC 6125, section 6.4.3, subitem 1.
+ # The client SHOULD NOT attempt to match a presented identifier in which
+ # the wildcard character comprises a label other than the left-most label.
+ if leftmost == '*':
+ # When '*' is a fragment by itself, it matches a non-empty dotless
+ # fragment.
+ pats.append('[^.]+')
+ elif leftmost.startswith('xn--') or hostname.startswith('xn--'):
+ # RFC 6125, section 6.4.3, subitem 3.
+ # The client SHOULD NOT attempt to match a presented identifier
+ # where the wildcard character is embedded within an A-label or
+ # U-label of an internationalized domain name.
+ pats.append(re.escape(leftmost))
+ else:
+ # Otherwise, '*' matches any dotless string, e.g. www*
+ pats.append(re.escape(leftmost).replace(r'\*', '[^.]*'))
+
+ # add the remaining fragments, ignore any wildcards
+ for frag in remainder:
+ pats.append(re.escape(frag))
+
+ pat = re.compile(r'\A' + r'\.'.join(pats) + r'\Z', re.IGNORECASE)
+ return pat.match(hostname)
+
+
+def _MatchHostname(cert, hostname):
+ """Verify that *cert* (in decoded format as returned by
+ SSLSocket.getpeercert()) matches the *hostname*. RFC 2818 and RFC 6125
+ rules are followed, but IP addresses are not accepted for *hostname*.
+
+ CertificateError is raised on failure. On success, the function
+ returns nothing.
+ """
+ if not cert:
+ raise ValueError('empty or no certificate, match_hostname needs a '
+ 'SSL socket or SSL context with either '
+ 'CERT_OPTIONAL or CERT_REQUIRED')
+ dnsnames = []
+ san = cert.get('subjectAltName', ())
+ for key, value in san:
+ if key == 'DNS':
+ if _DNSNameMatch(value, hostname):
+ return
+ dnsnames.append(value)
+ if not dnsnames:
+ # The subject is only checked when there is no dNSName entry
+ # in subjectAltName
+ for sub in cert.get('subject', ()):
+ for key, value in sub:
+ # XXX according to RFC 2818, the most specific Common Name
+ # must be used.
+ if key == 'commonName':
+ if _DNSNameMatch(value, hostname):
+ return
+ dnsnames.append(value)
+ if len(dnsnames) > 1:
+ raise CertificateError('hostname %r doesn\'t match either of %s'
+ % (hostname, ', '.join(map(repr, dnsnames))))
+ elif len(dnsnames) == 1:
+ raise CertificateError('hostname %r doesn\'t match %r'
+ % (hostname, dnsnames[0]))
+ else:
+ raise CertificateError('no appropriate commonName or '
+ 'subjectAltName fields were found')
+
+
+class HTTPSConnection(httplib.HTTPSConnection):
+
+ def __init__(self, host, root_certs=_TRUSTED_ROOT_CERTS, **kwargs):
+ self.root_certs = root_certs
+ httplib.HTTPSConnection.__init__(self, host, **kwargs)
+
+ def connect(self):
+ # Overrides for certificate verification.
+ args = [(self.host, self.port), self.timeout,]
+ if self.source_address:
+ args.append(self.source_address)
+ sock = socket.create_connection(*args)
+
+ if self._tunnel_host:
+ self.sock = sock
+ self._tunnel()
+
+ # Wrap the socket for verification with the root certs.
+ kwargs = {}
+ if self.root_certs is not None:
+ kwargs.update(cert_reqs=ssl.CERT_REQUIRED, ca_certs=self.root_certs)
+ self.sock = ssl.wrap_socket(sock, **kwargs)
+
+ # Check hostname.
+ try:
+ _MatchHostname(self.sock.getpeercert(), self.host)
+ except CertificateError:
+ self.sock.shutdown(socket.SHUT_RDWR)
+ self.sock.close()
+ raise
+
+
+class HTTPSHandler(urllib2.HTTPSHandler):
+
+ def __init__(self, root_certs=_TRUSTED_ROOT_CERTS):
+ urllib2.HTTPSHandler.__init__(self)
+ self.root_certs = root_certs
+
+ def https_open(self, req):
+ # Pass a reference to the function below so that verification against
+ # trusted root certs could be injected.
+ return self.do_open(self.GetConnection, req)
+
+ def GetConnection(self, host, **kwargs):
+ params = dict(root_certs=self.root_certs)
+ params.update(kwargs)
+ return HTTPSConnection(host, **params)
+
+
+def _SendRequest(url, timeout=None):
+ """Send request to the given https url, and return the server response.
+
+ Args:
+ url: The https url to send request to.
+
+ Returns:
+ An integer: http code of the response.
+ A string: content of the response.
+
+ Raises:
+ CertificateError: Certificate verification fails.
+ """
+ if not url:
+ return None, None
+
+ handlers = []
+ if url.startswith('https://'):
+ # HTTPSHandler has to go first, because we don't want to send secure cookies
+ # to a man in the middle.
+ handlers.append(HTTPSHandler())
+
+
+ cookie_file = os.environ.get('COOKIE_FILE')
+ if cookie_file and os.path.exists(cookie_file):
+ handlers.append(
+ urllib2.HTTPCookieProcessor(cookielib.MozillaCookieJar(cookie_file)))
+
+ url_opener = urllib2.build_opener(*handlers)
+ if timeout is not None:
+ response = url_opener.open(url, timeout=timeout)
+ else:
+ response = url_opener.open(url)
+ return response.code, response.read()
+
+
+class HttpClientLocal(http_client.HttpClient):
+ """This http client is used locally in a workstation, GCE VMs, etc."""
+
+ @staticmethod
+ def Get(url, params={}, timeout=None):
+ if params:
+ url = '%s?%s' % (url, urllib.urlencode(params))
+ return _SendRequest(url, timeout=timeout)