ssl_support.py 8.3 KB

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  1. import os
  2. import socket
  3. import atexit
  4. import re
  5. import functools
  6. import urllib.request
  7. import http.client
  8. from pkg_resources import ResolutionError, ExtractionError
  9. try:
  10. import ssl
  11. except ImportError:
  12. ssl = None
  13. __all__ = [
  14. 'VerifyingHTTPSHandler', 'find_ca_bundle', 'is_available', 'cert_paths',
  15. 'opener_for'
  16. ]
  17. cert_paths = """
  18. /etc/pki/tls/certs/ca-bundle.crt
  19. /etc/ssl/certs/ca-certificates.crt
  20. /usr/share/ssl/certs/ca-bundle.crt
  21. /usr/local/share/certs/ca-root.crt
  22. /etc/ssl/cert.pem
  23. /System/Library/OpenSSL/certs/cert.pem
  24. /usr/local/share/certs/ca-root-nss.crt
  25. /etc/ssl/ca-bundle.pem
  26. """.strip().split()
  27. try:
  28. HTTPSHandler = urllib.request.HTTPSHandler
  29. HTTPSConnection = http.client.HTTPSConnection
  30. except AttributeError:
  31. HTTPSHandler = HTTPSConnection = object
  32. is_available = ssl is not None and object not in (
  33. HTTPSHandler, HTTPSConnection)
  34. try:
  35. from ssl import CertificateError, match_hostname
  36. except ImportError:
  37. try:
  38. from backports.ssl_match_hostname import CertificateError
  39. from backports.ssl_match_hostname import match_hostname
  40. except ImportError:
  41. CertificateError = None
  42. match_hostname = None
  43. if not CertificateError:
  44. class CertificateError(ValueError):
  45. pass
  46. if not match_hostname:
  47. def _dnsname_match(dn, hostname, max_wildcards=1):
  48. """Matching according to RFC 6125, section 6.4.3
  49. https://tools.ietf.org/html/rfc6125#section-6.4.3
  50. """
  51. pats = []
  52. if not dn:
  53. return False
  54. # Ported from python3-syntax:
  55. # leftmost, *remainder = dn.split(r'.')
  56. parts = dn.split(r'.')
  57. leftmost = parts[0]
  58. remainder = parts[1:]
  59. wildcards = leftmost.count('*')
  60. if wildcards > max_wildcards:
  61. # Issue #17980: avoid denials of service by refusing more
  62. # than one wildcard per fragment. A survey of established
  63. # policy among SSL implementations showed it to be a
  64. # reasonable choice.
  65. raise CertificateError(
  66. "too many wildcards in certificate DNS name: " + repr(dn))
  67. # speed up common case w/o wildcards
  68. if not wildcards:
  69. return dn.lower() == hostname.lower()
  70. # RFC 6125, section 6.4.3, subitem 1.
  71. # The client SHOULD NOT attempt to match a
  72. # presented identifier in which the wildcard
  73. # character comprises a label other than the
  74. # left-most label.
  75. if leftmost == '*':
  76. # When '*' is a fragment by itself, it matches a non-empty dotless
  77. # fragment.
  78. pats.append('[^.]+')
  79. elif leftmost.startswith('xn--') or hostname.startswith('xn--'):
  80. # RFC 6125, section 6.4.3, subitem 3.
  81. # The client SHOULD NOT attempt to match a presented identifier
  82. # where the wildcard character is embedded within an A-label or
  83. # U-label of an internationalized domain name.
  84. pats.append(re.escape(leftmost))
  85. else:
  86. # Otherwise, '*' matches any dotless string, e.g. www*
  87. pats.append(re.escape(leftmost).replace(r'\*', '[^.]*'))
  88. # add the remaining fragments, ignore any wildcards
  89. for frag in remainder:
  90. pats.append(re.escape(frag))
  91. pat = re.compile(r'\A' + r'\.'.join(pats) + r'\Z', re.IGNORECASE)
  92. return pat.match(hostname)
  93. def match_hostname(cert, hostname):
  94. """Verify that *cert* (in decoded format as returned by
  95. SSLSocket.getpeercert()) matches the *hostname*. RFC 2818 and RFC 6125
  96. rules are followed, but IP addresses are not accepted for *hostname*.
  97. CertificateError is raised on failure. On success, the function
  98. returns nothing.
  99. """
  100. if not cert:
  101. raise ValueError("empty or no certificate")
  102. dnsnames = []
  103. san = cert.get('subjectAltName', ())
  104. for key, value in san:
  105. if key == 'DNS':
  106. if _dnsname_match(value, hostname):
  107. return
  108. dnsnames.append(value)
  109. if not dnsnames:
  110. # The subject is only checked when there is no dNSName entry
  111. # in subjectAltName
  112. for sub in cert.get('subject', ()):
  113. for key, value in sub:
  114. # XXX according to RFC 2818, the most specific Common Name
  115. # must be used.
  116. if key == 'commonName':
  117. if _dnsname_match(value, hostname):
  118. return
  119. dnsnames.append(value)
  120. if len(dnsnames) > 1:
  121. raise CertificateError(
  122. "hostname %r doesn't match either of %s"
  123. % (hostname, ', '.join(map(repr, dnsnames))))
  124. elif len(dnsnames) == 1:
  125. raise CertificateError(
  126. "hostname %r doesn't match %r"
  127. % (hostname, dnsnames[0]))
  128. else:
  129. raise CertificateError(
  130. "no appropriate commonName or "
  131. "subjectAltName fields were found")
  132. class VerifyingHTTPSHandler(HTTPSHandler):
  133. """Simple verifying handler: no auth, subclasses, timeouts, etc."""
  134. def __init__(self, ca_bundle):
  135. self.ca_bundle = ca_bundle
  136. HTTPSHandler.__init__(self)
  137. def https_open(self, req):
  138. return self.do_open(
  139. lambda host, **kw: VerifyingHTTPSConn(host, self.ca_bundle, **kw),
  140. req
  141. )
  142. class VerifyingHTTPSConn(HTTPSConnection):
  143. """Simple verifying connection: no auth, subclasses, timeouts, etc."""
  144. def __init__(self, host, ca_bundle, **kw):
  145. HTTPSConnection.__init__(self, host, **kw)
  146. self.ca_bundle = ca_bundle
  147. def connect(self):
  148. sock = socket.create_connection(
  149. (self.host, self.port), getattr(self, 'source_address', None)
  150. )
  151. # Handle the socket if a (proxy) tunnel is present
  152. if hasattr(self, '_tunnel') and getattr(self, '_tunnel_host', None):
  153. self.sock = sock
  154. self._tunnel()
  155. # http://bugs.python.org/issue7776: Python>=3.4.1 and >=2.7.7
  156. # change self.host to mean the proxy server host when tunneling is
  157. # being used. Adapt, since we are interested in the destination
  158. # host for the match_hostname() comparison.
  159. actual_host = self._tunnel_host
  160. else:
  161. actual_host = self.host
  162. if hasattr(ssl, 'create_default_context'):
  163. ctx = ssl.create_default_context(cafile=self.ca_bundle)
  164. self.sock = ctx.wrap_socket(sock, server_hostname=actual_host)
  165. else:
  166. # This is for python < 2.7.9 and < 3.4?
  167. self.sock = ssl.wrap_socket(
  168. sock, cert_reqs=ssl.CERT_REQUIRED, ca_certs=self.ca_bundle
  169. )
  170. try:
  171. match_hostname(self.sock.getpeercert(), actual_host)
  172. except CertificateError:
  173. self.sock.shutdown(socket.SHUT_RDWR)
  174. self.sock.close()
  175. raise
  176. def opener_for(ca_bundle=None):
  177. """Get a urlopen() replacement that uses ca_bundle for verification"""
  178. return urllib.request.build_opener(
  179. VerifyingHTTPSHandler(ca_bundle or find_ca_bundle())
  180. ).open
  181. # from jaraco.functools
  182. def once(func):
  183. @functools.wraps(func)
  184. def wrapper(*args, **kwargs):
  185. if not hasattr(func, 'always_returns'):
  186. func.always_returns = func(*args, **kwargs)
  187. return func.always_returns
  188. return wrapper
  189. @once
  190. def get_win_certfile():
  191. try:
  192. import wincertstore
  193. except ImportError:
  194. return None
  195. class CertFile(wincertstore.CertFile):
  196. def __init__(self):
  197. super(CertFile, self).__init__()
  198. atexit.register(self.close)
  199. def close(self):
  200. try:
  201. super(CertFile, self).close()
  202. except OSError:
  203. pass
  204. _wincerts = CertFile()
  205. _wincerts.addstore('CA')
  206. _wincerts.addstore('ROOT')
  207. return _wincerts.name
  208. def find_ca_bundle():
  209. """Return an existing CA bundle path, or None"""
  210. extant_cert_paths = filter(os.path.isfile, cert_paths)
  211. return (
  212. get_win_certfile()
  213. or next(extant_cert_paths, None)
  214. or _certifi_where()
  215. )
  216. def _certifi_where():
  217. try:
  218. return __import__('certifi').where()
  219. except (ImportError, ResolutionError, ExtractionError):
  220. pass