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).

3 files changed, 559 insertions, 4 deletions

diff --git a/Lib/socket.py b/Lib/socket.py
index 45a122f..48bb4f6 100644
--- a/Lib/socket.py
+++ b/Lib/socket.py
@@ -68,11 +68,10 @@ if _have_ssl:
 
 _realsocket = socket
 if _have_ssl:
-    _realssl = ssl
     def ssl(sock, keyfile=None, certfile=None):
-        if hasattr(sock, "_sock"):
-            sock = sock._sock
-        return _realssl(sock, keyfile, certfile)
+        import ssl as realssl
+        return realssl.sslwrap_simple(sock, keyfile, certfile)
+    __all__.append("ssl")
 
 # WSA error codes
 if sys.platform.lower().startswith("win"):
diff --git a/Lib/ssl.py b/Lib/ssl.py
new file mode 100644
index 0000000..17a48ea
--- /dev/null
+++ b/Lib/ssl.py
@@ -0,0 +1,252 @@
+# Wrapper module for _ssl, providing some additional facilities
+# implemented in Python.  Written by Bill Janssen.
+
+"""\
+This module provides some more Pythonic support for SSL.
+
+Object types:
+
+  sslsocket -- subtype of socket.socket which does SSL over the socket
+
+Exceptions:
+
+  sslerror -- exception raised for I/O errors
+
+Functions:
+
+  cert_time_to_seconds -- convert time string used for certificate
+                          notBefore and notAfter functions to integer
+                          seconds past the Epoch (the time values
+                          returned from time.time())
+
+  fetch_server_certificate (HOST, PORT) -- fetch the certificate provided
+                          by the server running on HOST at port PORT.  No
+                          validation of the certificate is performed.
+
+Integer constants:
+
+SSL_ERROR_ZERO_RETURN
+SSL_ERROR_WANT_READ
+SSL_ERROR_WANT_WRITE
+SSL_ERROR_WANT_X509_LOOKUP
+SSL_ERROR_SYSCALL
+SSL_ERROR_SSL
+SSL_ERROR_WANT_CONNECT
+
+SSL_ERROR_EOF
+SSL_ERROR_INVALID_ERROR_CODE
+
+The following group define certificate requirements that one side is
+allowing/requiring from the other side:
+
+CERT_NONE - no certificates from the other side are required (or will
+            be looked at if provided)
+CERT_OPTIONAL - certificates are not required, but if provided will be
+                validated, and if validation fails, the connection will
+                also fail
+CERT_REQUIRED - certificates are required, and will be validated, and
+                if validation fails, the connection will also fail
+
+The following constants identify various SSL protocol variants:
+
+PROTOCOL_SSLv2
+PROTOCOL_SSLv3
+PROTOCOL_SSLv23
+PROTOCOL_TLSv1
+"""
+
+import os, sys
+
+import _ssl             # if we can't import it, let the error propagate
+from socket import socket
+from _ssl import sslerror
+from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
+from _ssl import PROTOCOL_SSLv2, PROTOCOL_SSLv3, PROTOCOL_SSLv23, PROTOCOL_TLSv1
+
+# Root certs:
+#
+# The "ca_certs" argument to sslsocket() expects a file containing one or more
+# certificates that are roots of various certificate signing chains.  This file
+# contains the certificates in PEM format (RFC ) where each certificate is
+# encoded in base64 encoding and surrounded with a header and footer:
+# -----BEGIN CERTIFICATE-----
+# ... (CA certificate in base64 encoding) ...
+# -----END CERTIFICATE-----
+# The various certificates in the file are just concatenated together:
+# -----BEGIN CERTIFICATE-----
+# ... (CA certificate in base64 encoding) ...
+# -----END CERTIFICATE-----
+# -----BEGIN CERTIFICATE-----
+# ... (a second CA certificate in base64 encoding) ...
+# -----END CERTIFICATE-----
+#
+# Some "standard" root certificates are available at
+#
+# http://www.thawte.com/roots/  (for Thawte roots)
+# http://www.verisign.com/support/roots.html  (for Verisign)
+
+class sslsocket (socket):
+
+    def __init__(self, sock, keyfile=None, certfile=None,
+                 server_side=False, cert_reqs=CERT_NONE,
+                 ssl_version=PROTOCOL_SSLv23, ca_certs=None):
+        socket.__init__(self, _sock=sock._sock)
+        if certfile and not keyfile:
+            keyfile = certfile
+        if server_side:
+            self._sslobj = _ssl.sslwrap(self._sock, 1, keyfile, certfile,
+                                        cert_reqs, ssl_version, ca_certs)
+        else:
+            # see if it's connected
+            try:
+                socket.getpeername(self)
+                # yes
+                self._sslobj = _ssl.sslwrap(self._sock, 0, keyfile, certfile,
+                                            cert_reqs, ssl_version, ca_certs)
+            except:
+                # no
+                self._sslobj = None
+        self.keyfile = keyfile
+        self.certfile = certfile
+        self.cert_reqs = cert_reqs
+        self.ssl_version = ssl_version
+        self.ca_certs = ca_certs
+
+    def read(self, len=1024):
+        return self._sslobj.read(len)
+
+    def write(self, data):
+        return self._sslobj.write(data)
+
+    def getpeercert(self):
+        return self._sslobj.peer_certificate()
+
+    def send (self, data, flags=0):
+        if flags != 0:
+            raise ValueError(
+                "non-zero flags not allowed in calls to send() on %s" %
+                self.__class__)
+        return self._sslobj.write(data)
+
+    def send_to (self, data, addr, flags=0):
+        raise ValueError("send_to not allowed on instances of %s" %
+                         self.__class__)
+
+    def sendall (self, data, flags=0):
+        if flags != 0:
+            raise ValueError(
+                "non-zero flags not allowed in calls to sendall() on %s" %
+                self.__class__)
+        return self._sslobj.write(data)
+
+    def recv (self, buflen=1024, flags=0):
+        if flags != 0:
+            raise ValueError(
+                "non-zero flags not allowed in calls to sendall() on %s" %
+                self.__class__)
+        return self._sslobj.read(data, buflen)
+
+    def recv_from (self, addr, buflen=1024, flags=0):
+        raise ValueError("recv_from not allowed on instances of %s" %
+                         self.__class__)
+
+    def shutdown(self):
+        if self._sslobj:
+            self._sslobj.shutdown()
+            self._sslobj = None
+        else:
+            socket.shutdown(self)
+
+    def close(self):
+        if self._sslobj:
+            self.shutdown()
+        else:
+            socket.close(self)
+
+    def connect(self, addr):
+        # Here we assume that the socket is client-side, and not
+        # connected at the time of the call.  We connect it, then wrap it.
+        if self._sslobj or (self.getsockname()[1] != 0):
+            raise ValueError("attempt to connect already-connected sslsocket!")
+        socket.connect(self, addr)
+        self._sslobj = _ssl.sslwrap(self._sock, 0, self.keyfile, self.certfile,
+                                    self.cert_reqs, self.ssl_version,
+                                    self.ca_certs)
+
+    def accept(self):
+        raise ValueError("accept() not supported on an sslsocket")
+
+
+# some utility functions
+
+def cert_time_to_seconds(cert_time):
+    import time
+    return time.mktime(time.strptime(cert_time, "%b %d %H:%M:%S %Y GMT"))
+
+# a replacement for the old socket.ssl function
+
+def sslwrap_simple (sock, keyfile=None, certfile=None):
+
+    return _ssl.sslwrap(sock._sock, 0, keyfile, certfile, CERT_NONE,
+                        PROTOCOL_SSLv23, None)
+
+# fetch the certificate that the server is providing in PEM form
+
+def fetch_server_certificate (host, port):
+
+    import re, tempfile, os
+
+    def subproc(cmd):
+        from subprocess import Popen, PIPE, STDOUT
+        proc = Popen(cmd, stdout=PIPE, stderr=STDOUT, shell=True)
+        status = proc.wait()
+        output = proc.stdout.read()
+        return status, output
+
+    def strip_to_x509_cert(certfile_contents, outfile=None):
+        m = re.search(r"^([-]+BEGIN CERTIFICATE[-]+[\r]*\n"
+                      r".*[\r]*^[-]+END CERTIFICATE[-]+)$",
+                      certfile_contents, re.MULTILINE | re.DOTALL)
+        if not m:
+            return None
+        else:
+            tn = tempfile.mktemp()
+            fp = open(tn, "w")
+            fp.write(m.group(1) + "\n")
+            fp.close()
+            try:
+                tn2 = (outfile or tempfile.mktemp())
+                status, output = subproc(r'openssl x509 -in "%s" -out "%s"' %
+                                         (tn, tn2))
+                if status != 0:
+                    raise OperationError(status, tsig, output)
+                fp = open(tn2, 'rb')
+                data = fp.read()
+                fp.close()
+                os.unlink(tn2)
+                return data
+            finally:
+                os.unlink(tn)
+
+    if sys.platform.startswith("win"):
+        tfile = tempfile.mktemp()
+        fp = open(tfile, "w")
+        fp.write("quit\n")
+        fp.close()
+        try:
+            status, output = subproc(
+                'openssl s_client -connect "%s:%s" -showcerts < "%s"' %
+                (host, port, tfile))
+        finally:
+            os.unlink(tfile)
+    else:
+        status, output = subproc(
+            'openssl s_client -connect "%s:%s" -showcerts < /dev/null' %
+            (host, port))
+    if status != 0:
+        raise OSError(status)
+    certtext = strip_to_x509_cert(output)
+    if not certtext:
+        raise ValueError("Invalid response received from server at %s:%s" %
+                         (host, port))
+    return certtext
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
new file mode 100644
index 0000000..0188dc2
--- /dev/null
+++ b/Lib/test/test_ssl.py
@@ -0,0 +1,304 @@
+# Test the support for SSL and sockets
+
+import sys
+import unittest
+from test import test_support
+import socket
+import errno
+import threading
+import subprocess
+import time
+import os
+import pprint
+import urllib
+import shutil
+import string
+import traceback
+
+# Optionally test SSL support, if we have it in the tested platform
+skip_expected = False
+try:
+    import ssl
+except ImportError:
+    skip_expected = True
+
+CERTFILE = None
+GMAIL_POP_CERTFILE = None
+
+class BasicTests(unittest.TestCase):
+
+    def testRudeShutdown(self):
+        # Some random port to connect to.
+        PORT = [9934]
+
+        listener_ready = threading.Event()
+        listener_gone = threading.Event()
+
+        # `listener` runs in a thread.  It opens a socket listening on
+        # PORT, and sits in an accept() until the main thread connects.
+        # Then it rudely closes the socket, and sets Event `listener_gone`
+        # to let the main thread know the socket is gone.
+        def listener():
+            s = socket.socket()
+            PORT[0] = test_support.bind_port(s, '', PORT[0])
+            s.listen(5)
+            listener_ready.set()
+            s.accept()
+            s = None # reclaim the socket object, which also closes it
+            listener_gone.set()
+
+        def connector():
+            listener_ready.wait()
+            s = socket.socket()
+            s.connect(('localhost', PORT[0]))
+            listener_gone.wait()
+            try:
+                ssl_sock = socket.ssl(s)
+            except socket.sslerror:
+                pass
+            else:
+                raise test_support.TestFailed(
+                      'connecting to closed SSL socket should have failed')
+
+        t = threading.Thread(target=listener)
+        t.start()
+        connector()
+        t.join()
+
+    def testSSLconnect(self):
+        import os
+        with test_support.transient_internet():
+            s = ssl.sslsocket(socket.socket(socket.AF_INET),
+                              cert_reqs=ssl.CERT_NONE)
+            s.connect(("pop.gmail.com", 995))
+            c = s.getpeercert()
+            if c:
+                raise test_support.TestFailed("Peer cert %s shouldn't be here!")
+            s.close()
+
+            # this should fail because we have no verification certs
+            s = ssl.sslsocket(socket.socket(socket.AF_INET),
+                              cert_reqs=ssl.CERT_REQUIRED)
+            try:
+                s.connect(("pop.gmail.com", 995))
+            except ssl.sslerror:
+                pass
+            finally:
+                s.close()
+
+class ConnectedTests(unittest.TestCase):
+
+    def testTLSecho (self):
+
+        s1 = socket.socket()
+        s1.connect(('127.0.0.1', 10024))
+        c1 = ssl.sslsocket(s1, ssl_version=ssl.PROTOCOL_TLSv1)
+        indata = "FOO\n"
+        c1.write(indata)
+        outdata = c1.read()
+        if outdata != indata.lower():
+            sys.stderr.write("bad data <<%s>> received\n" % data)
+        c1.close()
+
+    def testReadCert(self):
+
+        s2 = socket.socket()
+        s2.connect(('127.0.0.1', 10024))
+        c2 = ssl.sslsocket(s2, ssl_version=ssl.PROTOCOL_TLSv1,
+                           cert_reqs=ssl.CERT_REQUIRED, ca_certs=CERTFILE)
+        cert = c2.getpeercert()
+        if not cert:
+            raise test_support.TestFailed("Can't get peer certificate.")
+        if not cert.has_key('subject'):
+            raise test_support.TestFailed(
+                "No subject field in certificate: %s." %
+                pprint.pformat(cert))
+        if not (cert['subject'].has_key('organizationName')):
+            raise test_support.TestFailed(
+                "No 'organizationName' field in certificate subject: %s." %
+                pprint.pformat(cert))
+        if (cert['subject']['organizationName'] !=
+              "Python Software Foundation"):
+            raise test_support.TestFailed(
+                "Invalid 'organizationName' field in certificate subject; "
+                "should be 'Python Software Foundation'.");
+        c2.close()
+
+
+class threadedEchoServer(threading.Thread):
+
+    class connectionHandler(threading.Thread):
+
+        def __init__(self, server, connsock):
+            self.server = server
+            self.running = False
+            self.sock = connsock
+            threading.Thread.__init__(self)
+            self.setDaemon(True)
+
+        def run (self):
+            self.running = True
+            sslconn = ssl.sslsocket(self.sock, server_side=True,
+                                    certfile=self.server.certificate,
+                                    ssl_version=self.server.protocol,
+                                    cert_reqs=self.server.certreqs)
+            while self.running:
+                try:
+                    msg = sslconn.read()
+                    if not msg:
+                        # eof, so quit this handler
+                        self.running = False
+                        sslconn.close()
+                    elif msg.strip() == 'over':
+                        sslconn.close()
+                        self.server.stop()
+                        self.running = False
+                    else:
+                        # print "server:", msg.strip().lower()
+                        sslconn.write(msg.lower())
+                except ssl.sslerror:
+                    sys.stderr.write(string.join(
+                        traceback.format_exception(*sys.exc_info())))
+                    sslconn.close()
+                    self.running = False
+                except:
+                    sys.stderr.write(string.join(
+                        traceback.format_exception(*sys.exc_info())))
+
+    def __init__(self, port, certificate, ssl_version=ssl.PROTOCOL_TLSv1,
+                 certreqs=ssl.CERT_NONE, cacerts=None):
+        self.certificate = certificate
+        self.protocol = ssl_version
+        self.certreqs = certreqs
+        self.cacerts = cacerts
+        self.sock = socket.socket()
+        self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+        self.sock.bind(('127.0.0.1', port))
+        self.active = False
+        threading.Thread.__init__(self)
+        self.setDaemon(False)
+
+    def run (self):
+        self.sock.settimeout(0.5)
+        self.sock.listen(5)
+        self.active = True
+        while self.active:
+            try:
+                newconn, connaddr = self.sock.accept()
+                # sys.stderr.write('new connection from ' + str(connaddr))
+                handler = self.connectionHandler(self, newconn)
+                handler.start()
+            except socket.timeout:
+                pass
+            except KeyboardInterrupt:
+                self.active = False
+            except:
+                sys.stderr.write(string.join(
+                    traceback.format_exception(*sys.exc_info())))
+
+    def stop (self):
+        self.active = False
+
+
+CERTFILE_CONFIG_TEMPLATE = """
+# create RSA certs - Server
+
+[ req ]
+default_bits = 1024
+encrypt_key = yes
+distinguished_name = req_dn
+x509_extensions = cert_type
+
+[ req_dn ]
+countryName = Country Name (2 letter code)
+countryName_default             = US
+countryName_min                 = 2
+countryName_max                 = 2
+
+stateOrProvinceName             = State or Province Name (full name)
+stateOrProvinceName_default     = %(state)s
+
+localityName                    = Locality Name (eg, city)
+localityName_default            = %(city)s
+
+0.organizationName              = Organization Name (eg, company)
+0.organizationName_default      = %(organization)s
+
+organizationalUnitName          = Organizational Unit Name (eg, section)
+organizationalUnitName_default  = %(unit)s
+
+0.commonName                    = Common Name (FQDN of your server)
+0.commonName_default            = %(common-name)s
+
+# To create a certificate for more than one name uncomment:
+# 1.commonName                  = DNS alias of your server
+# 2.commonName                  = DNS alias of your server
+# ...
+# See http://home.netscape.com/eng/security/ssl_2.0_certificate.html
+# to see how Netscape understands commonName.
+
+[ cert_type ]
+nsCertType = server
+"""
+
+def create_cert_files():
+
+    import tempfile, socket, os
+    d = tempfile.mkdtemp()
+    # now create a configuration file for the CA signing cert
+    fqdn = socket.getfqdn()
+    crtfile = os.path.join(d, "cert.pem")
+    conffile = os.path.join(d, "ca.conf")
+    fp = open(conffile, "w")
+    fp.write(CERTFILE_CONFIG_TEMPLATE %
+             {'state': "Delaware",
+              'city': "Wilmington",
+              'organization': "Python Software Foundation",
+              'unit': "SSL",
+              'common-name': fqdn,
+              })
+    fp.close()
+    os.system(
+        "openssl req -batch -new -x509 -days 10 -nodes -config %s "
+        "-keyout \"%s\" -out \"%s\" > /dev/null < /dev/null 2>&1" %
+        (conffile, crtfile, crtfile))
+    # now we have a self-signed server cert in crtfile
+    os.unlink(conffile)
+    #sf_certfile = os.path.join(d, "sourceforge-imap.pem")
+    #sf_cert = ssl.fetch_server_certificate('pop.gmail.com', 995)
+    #open(sf_certfile, 'w').write(sf_cert)
+    #return d, crtfile, sf_certfile
+    # sys.stderr.write(open(crtfile, 'r').read() + '\n')
+    return d, crtfile
+
+def test_main():
+    if skip_expected:
+        raise test_support.TestSkipped("socket module has no ssl support")
+
+    global CERTFILE
+    tdir, CERTFILE = create_cert_files()
+
+    tests = [BasicTests]
+
+    server = None
+    if test_support.is_resource_enabled('network'):
+        server = threadedEchoServer(10024, CERTFILE)
+        server.start()
+        time.sleep(1)
+        tests.append(ConnectedTests)
+
+    thread_info = test_support.threading_setup()
+
+    try:
+        test_support.run_unittest(*tests)
+    finally:
+        if server is not None and server.active:
+            server.stop()
+            # wait for it to stop
+            server.join()
+
+    shutil.rmtree(tdir)
+    test_support.threading_cleanup(*thread_info)
+
+if __name__ == "__main__":
+    test_main()