source: fedd/federation/authorizer.py @ 09b1e9d

#/usr/local/bin/python

from string import join
from tempfile import mkstemp
from subprocess import call
from threading import Lock

from fedid import fedid
from remote_service import service_caller
from service_error import service_error


import ABAC
import pickle

import sys
import os
import re

class authorizer_base:
    """
    Classes based on this one keep track of authorization attributes for the
    various modules running.  This base class holds some utility functions that
    they all potentially use.
    """

    # general error exception for badly formed names.  
    class bad_name(RuntimeError): pass
    # difficulty creating an attribute
    class attribute_error(RuntimeError): pass

    @staticmethod
    def auth_name(name):
        """
        Helper to convert a non-unicode local name to a unicode string.  Mixed
        representations can needlessly confuse the authorizer.
        """
        if isinstance(name, basestring):
            if not isinstance(name, unicode): return unicode(name)
            else: return name
        else: return name

    @staticmethod
    def valid_name(name):
        """
        Ensure that the given name is valid.  A valid name can either be a
        triple of strings and fedids representing one of our generalized Emulab
        names or a single fedid.  Compound names can include wildcards (None)
        and must anchor to a fedid at their highest level (unless they're all
        None)

        This either returns True or throws an exception.  More an assertion
        than a function.
        """
        if isinstance(name, tuple) and len(name) == 3:
            for n in name:
                if n: 
                    if not (isinstance(n, basestring) or isinstance(n, fedid)):
                        raise authorizer_base.bad_name(
                                "names must be either a triple or a fedid")
            for n in name: 
                if n:
                    if isinstance(n, fedid):
                        return True
                    else:
                        raise authorizer_base.bad_name(
                                "Compound names must be " + \
                                "rooted in fedids: %s" % str(name))

            return True
        elif isinstance(name, fedid):
            return True
        else:
            raise authorizer_base.bad_name(
                    "Names must be a triple or a fedid (%s)" % name)


class authorizer(authorizer_base):
    """
    This class keeps track of authorization attributes for the various modules
    running.  When it gets smarter it will be the basis for a real
    attribute-based authentication system.
    """
    def __init__(self, def_attr="testbed"):
        self.attrs = { }
        self.globals=set()

    def set_attribute(self, name, attr):
        """
        Attach attr to name.  Multiple attrs can be attached.
        """
        self.valid_name(name)
        if isinstance(name, tuple):
            aname = tuple([ self.auth_name(n) for n in name])
        else:
            aname = self.auth_name(name)

        if not self.attrs.has_key(aname):
            self.attrs[aname] = set()
        self.attrs[aname].add(attr)

    def unset_attribute(self, name, attr):
        """
        Remove an attribute from name
        """
        self.valid_name(name)
        if isinstance(name, tuple):
            aname = tuple([ self.auth_name(n) for n in name])
        else:
            aname = self.auth_name(name)

        attrs = self.attrs.get(aname, None)
        if attrs: attrs.discard(attr)

    def check_attribute(self, name, attr):
        """
        Return True if name has attr (or if attr is global).  Tuple names match
        any tuple name that matches all names present and has None entries in
        other fileds.  For tuple names True implies that there is a matching
        tuple name with the attribute.
        """
        def tup(tup, i, p):
            mask = 1 << i
            if p & mask : return authorizer.auth_name(tup[i])
            else: return None

        self.valid_name(name)
        if attr in self.globals:
            return True

        if isinstance(name, tuple):
            for p in range(0,8):
                lookup = ( tup(name, 0, p), tup(name,1, p), tup(name,2,p))
                if self.attrs.has_key(lookup):
                    if attr in self.attrs[lookup]:
                        return True
        else:
            return  attr in self.attrs.get(self.auth_name(name), set())

    def set_global_attribute(self, attr):
        """
        Set a global attribute.  All names, even those otherwise unknown to the
        authorizer have this attribute.
        """
        self.globals.add(attr)

    def unset_global_attribute(self, attr):
        """
        Remove a global attribute
        """

        self.globals.discard(attr)

    def __str__(self):
        rv = ""
        rv += "attrs %s\n" % self.attrs
        rv += "globals %s" % self.globals
        return rv

    def clone(self):
        rv = authorizer()
        rv.attrs = self.attrs.copy()
        rv.globals = self.globals.copy()
        return rv

    def save(self, fn):
        f = open(fn, "w")
        pickle.dump(self, f)
        f.close()

    def load(self, fn):
        f = open(fn, "r")
        a = pickle.load(f)
        f.close()
        self.attrs = a.attrs
        self.globals = a.globals
        

class abac_authorizer(authorizer_base):
    """
    Use the ABAC authorization system to make attribute decisions.
    """

    clean_attr_re = re.compile('[^A-Za-z_]+')
    cred_file_re = re.compile('.*\.der$')
    bad_name = authorizer_base.bad_name
    attribute_error = authorizer_base.attribute_error
    ABAC.libabac_init()

    def __init__(self, certs=None, me=None, key=None, loadfile=None):
        self.creddy = '/usr/local/bin/creddy'
        self.globals = set()
        self.lock = Lock()
        self.me = me
        self.key = key
        self.context = ABAC.Context()
        if me:
            self.fedid = fedid(file=self.me)
            self.context.load_id_file(self.me)
        else:
            self.fedid = None

        if isinstance(certs, basestring):
            certs = [ certs ] 

        for dir in certs or []:
            self.context.load_directory(dir)

        if loadfile:
            self.load(loadfile)

    @staticmethod
    def clean_attr(attr):
        return abac_authorizer.clean_attr_re.sub('_', attr)

    def set_attribute(self, name=None, attr=None, cert=None):
        if name and attr:
            if isinstance(name, tuple):
                raise abac_authorizer.bad_name(
                        "ABAC doesn't understand three-names")
            if self.me and self.key:
                # Create a credential and insert it into context
                # This will simplify when we have libcreddy
                try:
                    # create temp file
                    f, fn = mkstemp()
                    os.close(f)
                except EnvironmentError, e:
                    raise abac_authorizer.attribute_error(
                            "Cannot create temp file: %s" %e)

                # Create the attribute certificate with creddy
                cmd = [self.creddy, '--attribute', '--issuer=%s' % self.me, 
                    '--key=%s' % self.key, '--role=%s' % self.clean_attr(attr), 
                    '--subject-id=%s' % name, '--out=%s' % fn]
                rv = call(cmd)
                if rv == 0:
                    self.lock.acquire()
                    # load it to context and remove the file
                    rv = self.context.load_attribute_file(fn)
                    self.lock.release()
                    os.unlink(fn)
                else:
                    os.unlink(fn)
                    raise abac_authorizer.attribute_error(
                            "creddy returned %s" % rv)
            else:
                raise abac_authorizer.attribute_error(
                        "Identity and key not specified on creation")
        elif cert:
            # Insert this credential into the context
            self.lock.acquire()
            self.context.load_attribute_chunk(cert)
            self.lock.release()
        else:
            raise abac_authorizer.attribute_error(
                    "Neither name/attr nor cert is set")

    def unset_attribute(self, name, attr):
        if isinstance(name, tuple):
            raise abac_authorizer.bad_name(
                    "ABAC doesn't understand three-names")
        cattr = self.clean_attr(attr)
        self.lock.acquire()
        ctxt = ABAC.Context()
        ids = set()
        for c in self.context.credentials():
            h = c.head()
            t = c.tail()
            if h.is_role() and t.is_principal():
                if t.principal() == '%s' % name and \
                        h.principal() == '%s' % self.fedid and \
                        h.role_name() == cattr:
                    continue

            id = c.issuer_cert()
            if id not in ids:
                ctxt.load_id_chunk(id)
                ids.add(id)
            ctxt.load_attribute_chunk(c.attribute_cert())
        self.context = ctxt
        self.lock.release()


    def check_attribute(self, name, attr):
        # XXX proof soon
        if isinstance(name, tuple):
            raise abac_authorizer.bad_name(
                    "ABAC doesn't understand three-names")
        else:
            # Naked attributes are attested by this principal
            if attr.find('.') == -1: 
                a = "%s.%s" % (self.fedid, self.clean_attr(attr))
            else: 
                r, a = attr.split('.',1)
                a = "%s.%s" ( r, self.clean_attr(a))

            self.lock.acquire()
            proof, rv = self.context.query(a, name)
            # XXX delete soon
            if not rv and attr in self.globals: rv = True
            self.lock.release()

            return rv

    def set_global_attribute(self, attr):
        """
        Set a global attribute.  All names, even those otherwise unknown to the
        authorizer have this attribute.
        """
        self.lock.acquire()
        self.globals.add(self.clean_attr(attr))
        self.lock.release()

    def unset_global_attribute(self, attr):
        """
        Remove a global attribute
        """

        self.lock.acquire()
        self.globals.discard(self.clean_attr(attr))
        self.lock.release()

    def clone(self):
        self.lock.acquire()
        rv = abac_authorizer(me=self.me, key=self.key)
        rv.globals = self.globals.copy()
        rv.context = ABAC.Context(self.context)
        self.lock.release()
        return rv

    def save(self, dir):
        self.lock.acquire()
        try:
            if not os.access(dir, os.F_OK):
                os.mkdir(dir)
            # These are unpicklable, so set them aside
            context = self.context
            lock = self.lock
            self.context = None
            self.lock = None

            f = open("%s/state" % dir, "w")
            pickle.dump(self, f)
            f.close()

            if not os.access("%s/certs" %dir, os.F_OK):
                os.mkdir("%s/certs" % dir)
            seenit = set()

            #restore unpicklable state 
            self.context = context
            self.lock = lock
            #remove old certs
            for fn in [ f for f in os.listdir("%s/certs" % dir) \
                    if abac_authorizer.cred_file_re.match(f)]:
                os.unlink('%s/certs/%s' % (dir, fn))
            ii = 0
            ai = 0
            for c in self.context.credentials():
                id = c.issuer_cert()
                attr = c.attribute_cert()
                # NB: file naming conventions matter here.  The trailing_ID and
                # _attr are required by ABAC.COntext.load_directory()
                if id not in seenit:
                    f = open("%s/certs/ID_%03d_ID.der" % (dir, ii), "w")
                    print >>f, id
                    f.close()
                    ii += 1
                    seenit.add(id)
                if attr:
                    f = open("%s/certs/attr_%03d_attr.der" % (dir, ai), "w")
                    print >>f, attr
                    f.close()
                    ai += 1
        except EnvironmentError, e:
            # If we've mislaid self.lock, release lock (they're the same object)
            if self.lock: self.lock.release()
            elif lock: lock.release()
            raise e
        except pickle.PickleError, e:
            # If we've mislaid self.lock, release lock (they're the same object)
            if self.lock: self.lock.release()
            elif lock: lock.release()
            raise e
        self.lock.release()

    def load(self, dir):
        self.lock.acquire()
        try:
            if os.access("%s/state" % dir, os.R_OK):
                f = open("%s/state" % dir, "r")
                st = pickle.load(f)
                f.close()
                # Cpoy the useful attributes from the pickled state
                for a in ('globals', 'key', 'me', 'cert', 'fedid'):
                    setattr(self, a, getattr(st, a, None))

            # Initialize the new context with the new identity
            self.context = ABAC.Context()
            if self.me:
                self.context.load_id_file(self.me)
            self.context.load_directory("%s/certs" % dir)
        except EnvironmentError, e:
            self.lock.release()
            raise e
        except pickle.PickleError, e:
            self.lock.release()
            raise e
        self.lock.release()

    def __str__(self):
        def encode_role(r):
            if r.is_principal(): 
                return "%s" % r.principal()
            elif r.is_role(): 
                return "%s.%s" % (r.principal(), r.role_name())
            elif r.is_linking():
                return "%s.%s.%s" % \
                        (r.principal(), r.linking_role(), r.role_name())

        self.lock.acquire()
        rv = "%s" % self.fedid
        for c in self.context.credentials():
            rv += '\n%s <- %s' % (encode_role(c.head()), encode_role(c.tail()))
        self.lock.release()
        return rv