path: root/src/lib/Proxy.py

"""RPC client access to cobalt components.

Classes:
ComponentProxy -- an RPC client proxy to Cobalt components

Functions:
load_config -- read configuration files
"""

__revision__ = '$Revision: $'


from xmlrpclib import _Method

import httplib
import logging
import socket

# The ssl module is provided by either Python 2.6 or a separate ssl
# package that works on older versions of Python (see
# http://pypi.python.org/pypi/ssl).  If neither can be found, look for
# M2Crypto instead.
try:
    import ssl
    SSL_LIB = 'py26_ssl'
except ImportError, e:
    from M2Crypto import SSL
    SSL_LIB = 'm2crypto'


import string
import sys
import time
import urlparse
import xmlrpclib

version = sys.version_info[:2]
has_py23 = map(int, version) >= [2, 3]
has_py26 = map(int, version) >= [2, 6]

__all__ = ["ComponentProxy", "RetryMethod", "SSLHTTPConnection", "XMLRPCTransport"]

class CertificateError(Exception):
    def __init__(self, commonName):
        self.commonName = commonName

class RetryMethod(_Method):
    """Method with error handling and retries built in"""
    log = logging.getLogger('xmlrpc')
    max_retries = 4
    def __call__(self, *args):
        for retry in range(self.max_retries):
            try:
                return _Method.__call__(self, *args)
            except xmlrpclib.ProtocolError, err:
                self.log.error("Server failure: Protocol Error: %s %s" % \
                              (err.errcode, err.errmsg))
                raise xmlrpclib.Fault(20, "Server Failure")
            except xmlrpclib.Fault:
                raise
            except socket.error, err:
                if hasattr(err, 'errno') and err.errno == 336265218:
                    self.log.error("SSL Key error")
                    break
                if retry == 3:
                    self.log.error("Server failure: %s" % err)
                    raise xmlrpclib.Fault(20, err)
            except CertificateError, ce:
                self.log.error("Got unallowed commonName %s from server" \
                               % ce.commonName)
                break
            except KeyError:
                self.log.error("Server disallowed connection")
                break
            except:
                self.log.error("Unknown failure", exc_info=1)
                break
            time.sleep(0.5)
        raise xmlrpclib.Fault(20, "Server Failure")

# sorry jon
xmlrpclib._Method = RetryMethod

class SSLHTTPConnection(httplib.HTTPConnection):

    """Extension of HTTPConnection that implements SSL and related behaviors"""

    logger = logging.getLogger('Bcfg2.Proxy.SSLHTTPConnection')

    def __init__(self, host, port=None, strict=None, timeout=90, key=None,
                 cert=None, ca=None, scns=None, protocol='xmlrpc/ssl'):
        """Initializes the `httplib.HTTPConnection` object and stores security
        parameters

        Parameters
        ----------
        host : string
            Name of host to contact
        port : int, optional
            Port on which to contact the host.  If none is specified,
            the default port of 80 will be used unless the `host`
            string has a port embedded in the form host:port.
        strict : Boolean, optional
            Passed to the `httplib.HTTPConnection` constructor and if
            True, causes the `BadStatusLine` exception to be raised if
            the status line cannot be parsed as a valid HTTP 1.0 or
            1.1 status.
        timeout : int, optional
            Causes blocking operations to timeout after `timeout`
            seconds.
        key : string, optional
            The file system path to the local endpoint's SSL key.  May
            specify the same file as `cert` if using a file that
            contains both.  See
            http://docs.python.org/library/ssl.html#ssl-certificates
            for details.  Required if using xmlrpc/ssl with client
            certificate authentication.
        cert : string, optional
            The file system path to the local endpoint's SSL
            certificate.  May specify the same file as `cert` if using
            a file that contains both.  See
            http://docs.python.org/library/ssl.html#ssl-certificates
            for details.  Required if using xmlrpc/ssl with client
            certificate authentication.
        ca : string, optional
            The file system path to a set of concatenated certificate
            authority certs, which are used to validate certificates
            passed from the other end of the connection.
        scns : array-like, optional
            List of acceptable server commonNames.  The peer cert's
            common name must appear in this list, otherwise the
            connect() call will throw a `CertificateError`.
        protocol : {'xmlrpc/ssl', 'xmlrpc/tlsv1'}, optional
            Communication protocol to use.
        """
        if not has_py26:
            httplib.HTTPConnection.__init__(self, host, port, strict)
        else:
            httplib.HTTPConnection.__init__(self, host, port, strict, timeout)
        self.key = key
        self.cert = cert
        self.ca = ca
        self.scns = scns
        self.protocol = protocol
        self.timeout = timeout

    def connect(self):
        """Initiates a connection using previously set attributes"""
        if SSL_LIB == 'py26_ssl':
            self._connect_py26ssl()
        elif SSL_LIB == 'm2crypto':
            self._connect_m2crypto()
        else:
            raise Exception, "No SSL module support"


    def _connect_py26ssl(self):
        """Initiates a connection using the ssl module"""
        rawsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        if self.protocol == 'xmlrpc/ssl':
            ssl_protocol_ver = ssl.PROTOCOL_SSLv23
        elif self.protocol == 'xmlrpc/tlsv1':
            ssl_protocol_ver = ssl.PROTOCOL_TLSv1
        else:
            self.logger.error("Unknown protocol %s" % (self.protocol))
            raise Exception, "unknown protocol %s" % self.protocol
        if self.ca:
            other_side_required = ssl.CERT_REQUIRED
        else:
            other_side_required = ssl.CERT_NONE
            self.logger.warning("No ca is specified. Cannot authenticate the server with SSL.")
        if self.cert and not self.key:
            self.logger.warning("SSL cert specfied, but key. Cannot authenticate this client with SSL.")
            self.cert = None
        if self.key and not self.cert:
            self.logger.warning("SSL key specfied, but no cert. Cannot authenticate this client with SSL.")
            self.key = None

        if has_py23:
            rawsock.settimeout(self.timeout)
        self.sock = ssl.SSLSocket(rawsock, cert_reqs=other_side_required,
                                  ca_certs=self.ca, suppress_ragged_eofs=True,
                                  keyfile=self.key, certfile=self.cert,
                                  ssl_version=ssl_protocol_ver)
        self.sock.connect((self.host, self.port))
        peer_cert = self.sock.getpeercert()
        if peer_cert and self.scns:
            scn = [x[0][1] for x in peer_cert['subject'] if x[0][0] == 'commonName'][0]
            if scn not in self.scns:
                raise CertificateError, scn
        self.sock.closeSocket = True

    def _connect_m2crypto(self):
        """Initiates a connection using the M2Crypto module"""

        if self.protocol == 'xmlrpc/ssl':
            ctx = SSL.Context('sslv23')
        elif self.protocol == 'xmlrpc/tlsv1':
            ctx = SSL.Context('tlsv1')
        else:
            self.logger.error("Unknown protocol %s" % (self.protocol))
            raise Exception, "unknown protocol %s" % self.protocol

        if self.ca:
            # Use the certificate authority to validate the cert
            # presented by the server
            ctx.set_verify(SSL.verify_peer | SSL.verify_fail_if_no_peer_cert, depth=9)
            if ctx.load_verify_locations(self.ca) != 1:
                raise Exception('No CA certs')
        else:
            self.logger.warning("No ca is specified. Cannot authenticate the server with SSL.")

        if self.cert and self.key:
            # A cert/key is defined, use them to support client
            # authentication to the server
            ctx.load_cert(self.cert, self.key)
        elif self.cert:
            self.logger.warning("SSL cert specfied, but key. Cannot authenticate this client with SSL.")
        elif self.key:
            self.logger.warning("SSL key specfied, but no cert. Cannot authenticate this client with SSL.")

        self.sock = SSL.Connection(ctx)
        self.sock.connect((self.host, self.port)) # automatically checks cert matches host


class XMLRPCTransport(xmlrpclib.Transport):
    def __init__(self, key=None, cert=None, ca=None, scns=None, use_datetime=0, timeout=90):
        if hasattr(xmlrpclib.Transport, '__init__'):
            xmlrpclib.Transport.__init__(self, use_datetime)
        self.key = key
        self.cert = cert
        self.ca = ca
        self.scns = scns
        self.timeout = timeout

    def make_connection(self, host):
        host = self.get_host_info(host)[0]
        http = SSLHTTPConnection(host, key=self.key, cert=self.cert, ca=self.ca,
                                 scns=self.scns, timeout=self.timeout)
        https = httplib.HTTP()
        https._setup(http)
        return https

    def request(self, host, handler, request_body, verbose=0):
        '''send request to server and return response'''
        h = self.make_connection(host)
        self.send_request(h, handler, request_body)
        self.send_host(h, host)
        self.send_user_agent(h)
        self.send_content(h, request_body)

        errcode, errmsg, headers = h.getreply()
        msglen = int(headers.dict['content-length'])

        if errcode != 200:
            raise xmlrpclib.ProtocolError(host + handler, errcode, errmsg, headers)

        self.verbose = verbose

        return self._get_response(h.getfile(), msglen)

    def _get_response(self, fd, length):
        # read response from input file/socket, and parse it
        recvd = 0

        p, u = self.getparser()

        while recvd < length:
            rlen = min(length - recvd, 1024)
            response = fd.read(rlen)
            recvd += len(response)
            if not response:
                break
            if self.verbose:
                print "body:", repr(response), len(response)
            p.feed(response)

        fd.close()
        p.close()

        return u.close()

def ComponentProxy(url, user=None, password=None, key=None, cert=None, ca=None,
                   allowedServerCNs=None, timeout=90):

    """Constructs proxies to components.

    Arguments:
    component_name -- name of the component to connect to

    Additional arguments are passed to the ServerProxy constructor.
    """

    if user and password:
        method, path = urlparse.urlparse(url)[:2]
        newurl = "%s://%s:%s@%s" % (method, user, password, path)
    else:
        newurl = url
    ssl_trans = XMLRPCTransport(key, cert, ca, allowedServerCNs, timeout=timeout)
    return xmlrpclib.ServerProxy(newurl, allow_none=True, transport=ssl_trans)