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Server-side SSL and certificate validation, by Bill Janssen.
While cleaning up Bill's C style, I may have cleaned up some code he didn't touch as well (in _ssl.c).
This commit is contained in:
Guido van Rossum
parent
1a42ece0c7
commit
4f2c3ddca4
7 changed files with 1037 additions and 97 deletions
252
Lib/ssl.py
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252
Lib/ssl.py
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# Wrapper module for _ssl, providing some additional facilities
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# implemented in Python. Written by Bill Janssen.
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"""\
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This module provides some more Pythonic support for SSL.
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Object types:
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sslsocket -- subtype of socket.socket which does SSL over the socket
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Exceptions:
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sslerror -- exception raised for I/O errors
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Functions:
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cert_time_to_seconds -- convert time string used for certificate
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notBefore and notAfter functions to integer
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seconds past the Epoch (the time values
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returned from time.time())
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fetch_server_certificate (HOST, PORT) -- fetch the certificate provided
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by the server running on HOST at port PORT. No
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validation of the certificate is performed.
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Integer constants:
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SSL_ERROR_ZERO_RETURN
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SSL_ERROR_WANT_READ
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SSL_ERROR_WANT_WRITE
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SSL_ERROR_WANT_X509_LOOKUP
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SSL_ERROR_SYSCALL
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SSL_ERROR_SSL
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SSL_ERROR_WANT_CONNECT
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SSL_ERROR_EOF
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SSL_ERROR_INVALID_ERROR_CODE
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The following group define certificate requirements that one side is
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allowing/requiring from the other side:
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CERT_NONE - no certificates from the other side are required (or will
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be looked at if provided)
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CERT_OPTIONAL - certificates are not required, but if provided will be
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validated, and if validation fails, the connection will
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also fail
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CERT_REQUIRED - certificates are required, and will be validated, and
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if validation fails, the connection will also fail
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The following constants identify various SSL protocol variants:
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PROTOCOL_SSLv2
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PROTOCOL_SSLv3
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PROTOCOL_SSLv23
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PROTOCOL_TLSv1
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"""
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import os, sys
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import _ssl # if we can't import it, let the error propagate
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from socket import socket
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from _ssl import sslerror
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from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
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from _ssl import PROTOCOL_SSLv2, PROTOCOL_SSLv3, PROTOCOL_SSLv23, PROTOCOL_TLSv1
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# Root certs:
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#
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# The "ca_certs" argument to sslsocket() expects a file containing one or more
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# certificates that are roots of various certificate signing chains. This file
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# contains the certificates in PEM format (RFC ) where each certificate is
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# encoded in base64 encoding and surrounded with a header and footer:
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# -----BEGIN CERTIFICATE-----
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# ... (CA certificate in base64 encoding) ...
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# -----END CERTIFICATE-----
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# The various certificates in the file are just concatenated together:
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# -----BEGIN CERTIFICATE-----
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# ... (CA certificate in base64 encoding) ...
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# -----END CERTIFICATE-----
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# -----BEGIN CERTIFICATE-----
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# ... (a second CA certificate in base64 encoding) ...
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# -----END CERTIFICATE-----
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#
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# Some "standard" root certificates are available at
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#
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# http://www.thawte.com/roots/ (for Thawte roots)
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# http://www.verisign.com/support/roots.html (for Verisign)
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class sslsocket (socket):
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def __init__(self, sock, keyfile=None, certfile=None,
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server_side=False, cert_reqs=CERT_NONE,
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ssl_version=PROTOCOL_SSLv23, ca_certs=None):
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socket.__init__(self, _sock=sock._sock)
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if certfile and not keyfile:
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keyfile = certfile
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if server_side:
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self._sslobj = _ssl.sslwrap(self._sock, 1, keyfile, certfile,
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cert_reqs, ssl_version, ca_certs)
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else:
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# see if it's connected
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try:
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socket.getpeername(self)
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# yes
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self._sslobj = _ssl.sslwrap(self._sock, 0, keyfile, certfile,
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cert_reqs, ssl_version, ca_certs)
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except:
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# no
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self._sslobj = None
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self.keyfile = keyfile
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self.certfile = certfile
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self.cert_reqs = cert_reqs
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self.ssl_version = ssl_version
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self.ca_certs = ca_certs
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def read(self, len=1024):
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return self._sslobj.read(len)
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def write(self, data):
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return self._sslobj.write(data)
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def getpeercert(self):
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return self._sslobj.peer_certificate()
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def send (self, data, flags=0):
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if flags != 0:
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raise ValueError(
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"non-zero flags not allowed in calls to send() on %s" %
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self.__class__)
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return self._sslobj.write(data)
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def send_to (self, data, addr, flags=0):
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raise ValueError("send_to not allowed on instances of %s" %
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self.__class__)
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def sendall (self, data, flags=0):
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if flags != 0:
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raise ValueError(
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"non-zero flags not allowed in calls to sendall() on %s" %
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self.__class__)
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return self._sslobj.write(data)
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def recv (self, buflen=1024, flags=0):
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if flags != 0:
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raise ValueError(
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"non-zero flags not allowed in calls to sendall() on %s" %
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self.__class__)
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return self._sslobj.read(data, buflen)
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def recv_from (self, addr, buflen=1024, flags=0):
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raise ValueError("recv_from not allowed on instances of %s" %
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self.__class__)
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def shutdown(self):
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if self._sslobj:
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self._sslobj.shutdown()
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self._sslobj = None
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else:
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socket.shutdown(self)
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def close(self):
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if self._sslobj:
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self.shutdown()
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else:
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socket.close(self)
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def connect(self, addr):
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# Here we assume that the socket is client-side, and not
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# connected at the time of the call. We connect it, then wrap it.
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if self._sslobj or (self.getsockname()[1] != 0):
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raise ValueError("attempt to connect already-connected sslsocket!")
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socket.connect(self, addr)
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self._sslobj = _ssl.sslwrap(self._sock, 0, self.keyfile, self.certfile,
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self.cert_reqs, self.ssl_version,
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self.ca_certs)
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def accept(self):
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raise ValueError("accept() not supported on an sslsocket")
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# some utility functions
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def cert_time_to_seconds(cert_time):
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import time
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return time.mktime(time.strptime(cert_time, "%b %d %H:%M:%S %Y GMT"))
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# a replacement for the old socket.ssl function
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def sslwrap_simple (sock, keyfile=None, certfile=None):
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return _ssl.sslwrap(sock._sock, 0, keyfile, certfile, CERT_NONE,
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PROTOCOL_SSLv23, None)
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# fetch the certificate that the server is providing in PEM form
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def fetch_server_certificate (host, port):
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import re, tempfile, os
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def subproc(cmd):
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from subprocess import Popen, PIPE, STDOUT
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proc = Popen(cmd, stdout=PIPE, stderr=STDOUT, shell=True)
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status = proc.wait()
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output = proc.stdout.read()
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return status, output
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def strip_to_x509_cert(certfile_contents, outfile=None):
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m = re.search(r"^([-]+BEGIN CERTIFICATE[-]+[\r]*\n"
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r".*[\r]*^[-]+END CERTIFICATE[-]+)$",
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certfile_contents, re.MULTILINE | re.DOTALL)
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if not m:
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return None
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else:
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tn = tempfile.mktemp()
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fp = open(tn, "w")
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fp.write(m.group(1) + "\n")
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fp.close()
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try:
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tn2 = (outfile or tempfile.mktemp())
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status, output = subproc(r'openssl x509 -in "%s" -out "%s"' %
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(tn, tn2))
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if status != 0:
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raise OperationError(status, tsig, output)
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fp = open(tn2, 'rb')
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data = fp.read()
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fp.close()
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os.unlink(tn2)
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return data
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finally:
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os.unlink(tn)
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if sys.platform.startswith("win"):
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tfile = tempfile.mktemp()
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fp = open(tfile, "w")
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fp.write("quit\n")
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fp.close()
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try:
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status, output = subproc(
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'openssl s_client -connect "%s:%s" -showcerts < "%s"' %
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(host, port, tfile))
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finally:
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os.unlink(tfile)
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else:
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status, output = subproc(
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'openssl s_client -connect "%s:%s" -showcerts < /dev/null' %
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(host, port))
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if status != 0:
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raise OSError(status)
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certtext = strip_to_x509_cert(output)
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if not certtext:
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raise ValueError("Invalid response received from server at %s:%s" %
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(host, port))
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return certtext
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