warden_client.py

#!/usr/bin/python
# -*- coding: utf-8 -*-
#
# Copyright (C) 2011-2013 Cesnet z.s.p.o
# Use of this source is governed by a 3-clause BSD-style license, see LICENSE file.

import json, httplib, ssl, socket, logging, logging.handlers
from urlparse import urlparse
from urllib import urlencode
from sys import stderr, exc_info
from pprint import pformat
from traceback import format_tb
from os import path


class HTTPSConnection(httplib.HTTPSConnection):
    '''
    Overridden to allow peer certificate validation, configuration
    of SSL/ TLS version and cipher selection.  See:
    http://hg.python.org/cpython/file/c1c45755397b/Lib/httplib.py#l1144
    and `ssl.wrap_socket()`
    '''
    def __init__(self, host, **kwargs):
        self.ciphers = kwargs.pop('ciphers',None)
        self.ca_certs = kwargs.pop('ca_certs',None)
        self.ssl_version = kwargs.pop('ssl_version',ssl.PROTOCOL_SSLv23)

        httplib.HTTPSConnection.__init__(self,host,**kwargs)

    def connect(self):
        sock = socket.create_connection( (self.host, self.port), self.timeout)

        if self._tunnel_host:
            self.sock = sock
            self._tunnel()

        self.sock = ssl.wrap_socket(
            sock,
            keyfile = self.key_file,
            certfile = self.cert_file,
            ca_certs = self.ca_certs,
            cert_reqs = ssl.CERT_REQUIRED if self.ca_certs else ssl.CERT_NONE,
            ssl_version = self.ssl_version)



class Error(Exception):
    """ Object for returning error messages to calling application.
        Caller can test whether it received data or error by checking
        isinstance(res, Error).
        However if he does not want to deal with errors altogether,
        this error object also returns False value if used in Bool
        context (e.g. in "if res: print res" print is not evaluated),
        and also acts as empty iterator (e.g. in "for e in res: print e"
        print is also not evaluated).
        Also, it can be raised as an exception.
    """

    def __init__(self, message, logger=None, error=None, prio="error", method=None,
            req_id=None, detail=None, exc=None):

        self.message = message
        self.error = error
        self.method = method
        self.req_id = req_id
        self.detail = detail
        (self.exctype, self.excval, self.exctb) = exc or (None, None, None)
        self.cause = self.excval # compatibility with other exceptions
        if logger:
            getattr(logger, prio, "error")(str(self))
            info = self.info_str()
            if info:
                logger.info(info)
            debug = self.debug_str()
            if debug:
                logger.debug(debug)


    def __len__ (self):
        """ In list or iterable context we're empty """
        return 0


    def __iter__(self):
        """ We are the iterator """
        return self


    def next(self):
        """ In list or iterable context we're empty """
        raise StopIteration


    def __bool__(self):
        """ In boolean context we're never True """
        return False


    def __str__(self):
        out = []
        out.append("(%s)" % (self.error or "local"))
        if self.method is not None:
            out.append(" in %s" % self.method)
        if self.req_id is not None:
            out.append("(%8x)" % self.req_id)
        if self.message is not None:
            out.append(": %s" % self.message)
        if self.excval is not None:
            out.append(" - cause was %s: %s" % (type(self.excval).__name__, str(self.excval)))
        return "".join(out)


    def info_str(self):
        return ("Detail: %s" % pformat(self.detail)) or ""


    def debug_str(self):
        out = []
        if self.excval is not None:
            out.append("Exception %s: %s\n" % (type(self.excval).__name__, str(self.excval)))
        if self.exctb is not None:
            out.append("Traceback:\n%s" % "".join(format_tb(self.exctb)))
        return "".join(out)



class Client(object):

    def __init__(self,
            url,
            certfile=None,
            keyfile=None,
            cafile=None,
            timeout=60,
            recv_events_limit=6000,
            errlog={"level": "debug"},
            syslog=None,
            filelog=None,
            idstore=None,
            name="warden_client",
            secret=None):

        self.name = name
        self.secret = secret
        # Init logging as soon as possible and make sure we don't
        # spit out exceptions but just log or return Error objects
        self.init_log(errlog, syslog, filelog)

        self.url = urlparse(url, allow_fragments=False)

        self.conn = None

        base = path.join(path.dirname(__file__))
        self.certfile = path.join(base, certfile or "cert.pem")
        self.keyfile  = path.join(base, keyfile or "key.pem")
        self.cafile = path.join(base, cafile or "ca.pem")
        self.timeout = int(timeout)
        self.recv_events_limit = int(recv_events_limit)
        self.idstore = path.join(base, idstore) if idstore is not None else None

        self.ciphers = 'TLS_RSA_WITH_AES_256_CBC_SHA'
        self.sslversion = ssl.PROTOCOL_TLSv1


    def init_log(self, errlog, syslog, filelog):

        def loglevel(lev):
            try:
                return int(getattr(logging, lev.upper()))
            except (AttributeError, ValueError):
                self.logger.warning("Unknown loglevel \"%s\", using \"debug\"" % lev)
                return logging.DEBUG

        def facility(fac):
            try:
                return int(getattr(logging.handlers.SysLogHandler, "LOG_" + fac.upper()))
            except (AttributeError, ValueError):
                self.logger.warning("Unknown syslog facility \"%s\", using \"local7\"" % fac)
                return logging.handlers.SysLogHandler.LOG_LOCAL7

        form = "%(filename)s[%(process)d]: (%(levelname)s) %(name)s %(message)s"
        format_notime = logging.Formatter(form)
        format_time = logging.Formatter('%(asctime)s ' + form)

        self.logger = logging.getLogger(self.name)
        self.logger.propagate = False   # Don't bubble up to root logger
        self.logger.setLevel(logging.DEBUG)

        if errlog is not None:
            el = logging.StreamHandler(stderr)
            el.setFormatter(format_time)
            el.setLevel(loglevel(errlog.get("level", "debug")))
            self.logger.addHandler(el)

        if filelog is not None:
            try:
                fl = logging.FileHandler(
                    filename=path.join(
                        path.dirname(__file__),
                        filelog.get("file", "%s.log" % self.name)))
                fl.setLevel(loglevel(filelog.get("level", "warning")))
                fl.setFormatter(format_time)
                self.logger.addHandler(fl)
            except Exception as e:
                Error("Unable to setup file logging", self.logger, exc=exc_info())

        if syslog is not None:
            try:
                sl = logging.handlers.SysLogHandler(
                    address=syslog.get("socket", "/dev/log"),
                    facility=facility(syslog.get("facility", "local7")))
                sl.setLevel(loglevel(syslog.get("level", "warning")))
                sl.setFormatter(format_notime)
                self.logger.addHandler(sl)
            except Exception as e:
                Error("Unable to setup syslog logging", self.logger, exc=exc_info())

        if not (errlog or filelog or syslog):
            # User wants explicitly no logging, so let him shoot his socks off.
            # This silences complaining of logging module about no suitable
            # handler.
            self.logger.addHandler(logging.NullHandler())


    def connect(self):

        try:
            if self.url.scheme=="https":
                self.conn = HTTPSConnection(
                    self.url.netloc,
                    key_file = self.keyfile,
                    cert_file = self.certfile,
                    timeout = self.timeout,
                    ciphers = self.ciphers,
                    ca_certs = self.cafile,
                    ssl_version = self.sslversion)
            elif self.url.scheme=="http":
                self.conn = httplib.HTTPConnection(
                    self.url.netloc,
                    timeout = self.timeout)
            else:
                return Error("Don't know how to connect to \"%s\"" % self.url.scheme, self.logger,
                        detail={"url": self.url.geturl()})
        except Exception:
            return Error("HTTPS connection failed", self.logger, exc=exc_info(),
                detail={
                    "url": self.url.geturl(),
                    "timeout": self.timeout,
                    "key_file": self.keyfile,
                    "cert_file": self.certfile,
                    "cafile": self.cafile,
                    "ciphers": self.ciphers,
                    "ssl_version": self.sslversion})

        return True


    def sendRequest(self, func="", payload=None, **kwargs):

        if self.secret is None:
            kwargs["client"] = self.name
        else:
            kwargs["secret"] = self.secret

        if kwargs:
            for k in kwargs.keys():
                if kwargs[k] is None:
                    del kwargs[k]
            argurl = "?" + urlencode(kwargs, doseq=True)
        else:
            argurl = ""

        try:
            if payload is None:
                data = ""
            else:
                data = json.dumps(payload)
        except:
            return Error("Serialization to JSON failed", self.logger,
                exc=exc_info(), method=func, detail=payload)

        self.headers = {
            "Content-Type": "application/json",
            "Accept": "application/json",
            "Content-Length": str(len(data))
        }

        # We are connecting here at first use instead of in
        # constructor, because constructor cannot return data/errors
        # and we don't want to spit exceptions into user's face
        # And maaaybee sometime we will implement reconnection on errors
        if self.conn is None:
            err = self.connect()
            if not err:
                return err  # either False of Error instance

        loc = '%s/%s%s' % (self.url.path, func, argurl)
        try:
            self.conn.request("POST", loc, data, self.headers)
        except:
            return Error("Sending of request to server failed", self.logger,
                exc=exc_info(), method=func, detail={
                    "loc": loc,
                    "headers": self.headers,
                    "data": data})

        try:
            res = self.conn.getresponse()
        except:
            return Error("HTTP reply failed", self.logger, method=func, exc=exc_info())

        try:
            response_data = res.read()
        except:
            return Error("Fetching HTTP data from server failed", self.logger, method=func, exc=exc_info())

        if res.status==httplib.OK:
            try:
                data = json.loads(response_data)
            except:
                data = Error("JSON message parsing failed", self.logger,
                    exc=exc_info(), method=func, detail={"response": response_data})
        else:
            try:
                data = json.loads(response_data)
                data["error"]   # trigger exception if not dict or no error key
            except:
                data = Error("Generic server HTTP error", self.logger,
                    method=func,
                    error=res.status,
                    exc=exc_info(),
                    detail={"response": response_data})
            else:
                data = Error(data.get("message", None), self.logger,
                    method=data.get("method", None),
                    error=res.status,
                    req_id=data.get("req_id", None),
                    detail=data.get("detail", None))

        return data


    def _saveID(self, id, idstore=None):
        idf = idstore or self.idstore
        if not idf:
            return False
        try:
            with open(idf, "w+") as f:
                f.write(str(id))
        except (ValueError, IOError) as e:
            # Use Error instance just for proper logging
            Error("Writing id file \"%s\" failed" % idf, self.logger,
                prio="info", exc=exc_info(), detail={"idstore": idf})
        return id


    def _loadID(self, idstore=None):
        idf = idstore or self.idstore
        if not idf:
            return None
        try:
            with open(idf, "r") as f:
                id = int(f.read())
        except (ValueError, IOError) as e:
            Error("Reading id file \"%s\" failed, relying on server" % idf,
                self.logger, prio="info", exc=exc_info(), detail={"idstore": idf})
            id = None
        return id


    def getDebug(self):
        return self.sendRequest("getDebug")


    def getInfo(self):
        return self.sendRequest("getInfo")


    def sendEvents(self, events=[]):
        res = self.sendRequest(
            "sendEvents", payload=events)
        return res


    def getEvents(self, id=None, idstore=None, count=1,
            cat=None, nocat=None,
            tag=None, notag=None,
            group=None, nogroup=None):

        if not id:
            id = self._loadID(idstore)

        res = self.sendRequest(
            "getEvents", id=id, count=count or self.recv_events_limit, cat=cat,
            nocat=nocat, tag=tag, notag=notag, group=group, nogroup=nogroup)
        if not res:
            return res  # Should be Error instance

        try:
            events = res["events"]
            newid = res["lastid"]
        except KeyError:
            return Error("Server returned bogus reply", self.logger,
                method="getEvents", exc=exc_info(), detail={"response": res})

        self._saveID(newid)

        return events


    def close(self):

        if hasattr(self, "conn") and hasattr(self.conn, "close"):
            self.conn.close()


    __del__ = close



def read_cfg(cfgfile):
    abspath = path.join(path.dirname(__file__), cfgfile)
    with open(abspath, "r") as f:
        stripcomments = "\n".join((l for l in f if not l.lstrip().startswith("#")))
        return json.loads(stripcomments)