#----------------------------------------------------------------------
# Copyright (c) 2008 Board of Trustees, Princeton University
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and/or hardware specification (the "Work") to
# deal in the Work without restriction, including without limitation the
# rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Work, and to permit persons to whom the Work
# is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Work.
#
# THE WORK IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE WORK OR THE USE OR OTHER DEALINGS
# IN THE WORK.
#----------------------------------------------------------------------
##
# Implements SFA Credentials
#
# Credentials are signed XML files that assign a subject gid privileges to an object gid
##
### $Id$
### $URL$
import os
import datetime
from tempfile import mkstemp
from xml.dom.minidom import Document, parseString
from dateutil.parser import parse
import sfa.util.sfalogging
from sfa.trust.certificate import Keypair
from sfa.trust.credential_legacy import CredentialLegacy
from sfa.trust.rights import *
from sfa.trust.gid import *
from sfa.util.faults import *
# Two years, in seconds
DEFAULT_CREDENTIAL_LIFETIME = 60 * 60 * 24 * 365 * 2
# TODO:
# . make privs match between PG and PL
# . Need to add support for other types of credentials, e.g. tickets
signature_template = \
'''
'''
##
# Convert a string into a bool
def str2bool(str):
if str.lower() in ['yes','true','1']:
return True
return False
##
# Utility function to get the text of an XML element
def getTextNode(element, subele):
sub = element.getElementsByTagName(subele)[0]
if len(sub.childNodes) > 0:
return sub.childNodes[0].nodeValue
else:
return None
##
# Utility function to set the text of an XML element
# It creates the element, adds the text to it,
# and then appends it to the parent.
def append_sub(doc, parent, element, text):
ele = doc.createElement(element)
ele.appendChild(doc.createTextNode(text))
parent.appendChild(ele)
##
# Signature contains information about an xmlsec1 signature
# for a signed-credential
#
class Signature(object):
def __init__(self, string=None):
self.refid = None
self.issuer_gid = None
self.xml = None
if string:
self.xml = string
self.decode()
def get_refid(self):
if not self.refid:
self.decode()
return self.refid
def get_xml(self):
if not self.xml:
self.encode()
return self.xml
def set_refid(self, id):
self.refid = id
def get_issuer_gid(self):
if not self.gid:
self.decode()
return self.gid
def set_issuer_gid(self, gid):
self.gid = gid
def decode(self):
doc = parseString(self.xml)
sig = doc.getElementsByTagName("Signature")[0]
self.set_refid(sig.getAttribute("xml:id").strip("Sig_"))
keyinfo = sig.getElementsByTagName("X509Data")[0]
szgid = getTextNode(keyinfo, "X509Certificate")
szgid = "-----BEGIN CERTIFICATE-----\n%s\n-----END CERTIFICATE-----" % szgid
self.set_issuer_gid(GID(string=szgid))
def encode(self):
self.xml = signature_template % (self.get_refid(), self.get_refid())
##
# A credential provides a caller gid with privileges to an object gid.
# A signed credential is signed by the object's authority.
#
# Credentials are encoded in one of two ways. The legacy style places
# it in the subjectAltName of an X509 certificate. The new credentials
# are placed in signed XML.
#
# WARNING:
# In general, a signed credential obtained externally should
# not be changed else the signature is no longer valid. So, once
# you have loaded an existing signed credential, do not call encode() or sign() on it.
def filter_creds_by_caller(creds, caller_hrn):
"""
Returns a list of creds who's gid caller matches the
specified caller hrn
"""
if not isinstance(creds, list): creds = [creds]
caller_creds = []
for cred in creds:
try:
tmp_cred = Credential(string=cred)
if tmp_cred.get_gid_caller().get_hrn() == caller_hrn:
caller_creds.append(cred)
except: pass
return caller_creds
class Credential(object):
##
# Create a Credential object
#
# @param create If true, create a blank x509 certificate
# @param subject If subject!=None, create an x509 cert with the subject name
# @param string If string!=None, load the credential from the string
# @param filename If filename!=None, load the credential from the file
# FIXME: create and subject are ignored!
def __init__(self, create=False, subject=None, string=None, filename=None):
self.gidCaller = None
self.gidObject = None
self.expiration = None
self.privileges = None
self.issuer_privkey = None
self.issuer_gid = None
self.issuer_pubkey = None
self.parent = None
self.signature = None
self.xml = None
self.refid = None
self.legacy = None
# Check if this is a legacy credential, translate it if so
if string or filename:
if string:
str = string
elif filename:
str = file(filename).read()
if str.strip().startswith("-----"):
self.legacy = CredentialLegacy(False,string=str)
self.translate_legacy(str)
else:
self.xml = str
self.decode()
# Find an xmlsec1 path
self.xmlsec_path = ''
paths = ['/usr/bin','/usr/local/bin','/bin','/opt/bin','/opt/local/bin']
for path in paths:
if os.path.isfile(path + '/' + 'xmlsec1'):
self.xmlsec_path = path + '/' + 'xmlsec1'
break
def get_subject(self):
if not self.gidObject:
self.decode()
return self.gidObject.get_subject()
def get_signature(self):
if not self.signature:
self.decode()
return self.signature
def set_signature(self, sig):
self.signature = sig
##
# Translate a legacy credential into a new one
#
# @param String of the legacy credential
def translate_legacy(self, str):
legacy = CredentialLegacy(False,string=str)
self.gidCaller = legacy.get_gid_caller()
self.gidObject = legacy.get_gid_object()
lifetime = legacy.get_lifetime()
if not lifetime:
# Default to two years
self.set_lifetime(DEFAULT_CREDENTIAL_LIFETIME)
else:
self.set_lifetime(int(lifetime))
self.lifeTime = legacy.get_lifetime()
self.set_privileges(legacy.get_privileges())
self.get_privileges().delegate_all_privileges(legacy.get_delegate())
##
# Need the issuer's private key and name
# @param key Keypair object containing the private key of the issuer
# @param gid GID of the issuing authority
def set_issuer_keys(self, privkey, gid):
self.issuer_privkey = privkey
self.issuer_gid = gid
##
# Set this credential's parent
def set_parent(self, cred):
self.parent = cred
self.updateRefID()
##
# set the GID of the caller
#
# @param gid GID object of the caller
def set_gid_caller(self, gid):
self.gidCaller = gid
# gid origin caller is the caller's gid by default
self.gidOriginCaller = gid
##
# get the GID of the object
def get_gid_caller(self):
if not self.gidCaller:
self.decode()
return self.gidCaller
##
# set the GID of the object
#
# @param gid GID object of the object
def set_gid_object(self, gid):
self.gidObject = gid
##
# get the GID of the object
def get_gid_object(self):
if not self.gidObject:
self.decode()
return self.gidObject
##
# set the lifetime of this credential
#
# @param lifetime lifetime of credential
# . if lifeTime is a datetime object, it is used for the expiration time
# . if lifeTime is an integer value, it is considered the number of seconds
# remaining before expiration
def set_lifetime(self, lifeTime):
if isinstance(lifeTime, int):
self.expiration = datetime.timedelta(seconds=lifeTime) + datetime.datetime.utcnow()
else:
self.expiration = lifeTime
##
# get the lifetime of the credential (in datetime format)
def get_lifetime(self):
if not self.expiration:
self.decode()
return self.expiration
##
# set the privileges
#
# @param privs either a comma-separated list of privileges of a RightList object
def set_privileges(self, privs):
if isinstance(privs, str):
self.privileges = RightList(string = privs)
else:
self.privileges = privs
##
# return the privileges as a RightList object
def get_privileges(self):
if not self.privileges:
self.decode()
return self.privileges
##
# determine whether the credential allows a particular operation to be
# performed
#
# @param op_name string specifying name of operation ("lookup", "update", etc)
def can_perform(self, op_name):
rights = self.get_privileges()
if not rights:
return False
return rights.can_perform(op_name)
##
# Encode the attributes of the credential into an XML string
# This should be done immediately before signing the credential.
# WARNING:
# In general, a signed credential obtained externally should
# not be changed else the signature is no longer valid. So, once
# you have loaded an existing signed credential, do not call encode() or sign() on it.
def encode(self):
# Create the XML document
doc = Document()
signed_cred = doc.createElement("signed-credential")
doc.appendChild(signed_cred)
# Fill in the bit
cred = doc.createElement("credential")
cred.setAttribute("xml:id", self.get_refid())
signed_cred.appendChild(cred)
append_sub(doc, cred, "type", "privilege")
append_sub(doc, cred, "serial", "8")
append_sub(doc, cred, "owner_gid", self.gidCaller.save_to_string())
append_sub(doc, cred, "owner_urn", self.gidCaller.get_urn())
append_sub(doc, cred, "target_gid", self.gidObject.save_to_string())
append_sub(doc, cred, "target_urn", self.gidObject.get_urn())
append_sub(doc, cred, "uuid", "")
if not self.expiration:
self.set_lifetime(DEFAULT_CREDENTIAL_LIFETIME)
self.expiration = self.expiration.replace(microsecond=0)
append_sub(doc, cred, "expires", self.expiration.isoformat())
privileges = doc.createElement("privileges")
cred.appendChild(privileges)
if self.privileges:
rights = self.get_privileges()
for right in rights.rights:
priv = doc.createElement("privilege")
append_sub(doc, priv, "name", right.kind)
append_sub(doc, priv, "can_delegate", str(right.delegate).lower())
privileges.appendChild(priv)
# Add the parent credential if it exists
if self.parent:
sdoc = parseString(self.parent.get_xml())
p_cred = doc.importNode(sdoc.getElementsByTagName("credential")[0], True)
p = doc.createElement("parent")
p.appendChild(p_cred)
cred.appendChild(p)
# Create the tag
signatures = doc.createElement("signatures")
signed_cred.appendChild(signatures)
# Add any parent signatures
if self.parent:
for cur_cred in self.get_credential_list()[1:]:
sdoc = parseString(cur_cred.get_signature().get_xml())
ele = doc.importNode(sdoc.getElementsByTagName("Signature")[0], True)
signatures.appendChild(ele)
# Get the finished product
self.xml = doc.toxml()
def save_to_random_tmp_file(self):
fp, filename = mkstemp(suffix='cred', text=True)
fp = os.fdopen(fp, "w")
self.save_to_file(filename, save_parents=True, filep=fp)
return filename
def save_to_file(self, filename, save_parents=True, filep=None):
if not self.xml:
self.encode()
if filep:
f = filep
else:
f = open(filename, "w")
f.write(self.xml)
f.close()
def save_to_string(self, save_parents=True):
if not self.xml:
self.encode()
return self.xml
def get_refid(self):
if not self.refid:
self.refid = 'ref0'
return self.refid
def set_refid(self, rid):
self.refid = rid
##
# Figure out what refids exist, and update this credential's id
# so that it doesn't clobber the others. Returns the refids of
# the parents.
def updateRefID(self):
if not self.parent:
self.set_refid('ref0')
return []
refs = []
next_cred = self.parent
while next_cred:
refs.append(next_cred.get_refid())
if next_cred.parent:
next_cred = next_cred.parent
else:
next_cred = None
# Find a unique refid for this credential
rid = self.get_refid()
while rid in refs:
val = int(rid[3:])
rid = "ref%d" % (val + 1)
# Set the new refid
self.set_refid(rid)
# Return the set of parent credential ref ids
return refs
def get_xml(self):
if not self.xml:
self.encode()
return self.xml
##
# Sign the XML file created by encode()
#
# WARNING:
# In general, a signed credential obtained externally should
# not be changed else the signature is no longer valid. So, once
# you have loaded an existing signed credential, do not call encode() or sign() on it.
def sign(self):
if not self.issuer_privkey or not self.issuer_gid:
return
doc = parseString(self.get_xml())
sigs = doc.getElementsByTagName("signatures")[0]
# Create the signature template to be signed
signature = Signature()
signature.set_refid(self.get_refid())
sdoc = parseString(signature.get_xml())
sig_ele = doc.importNode(sdoc.getElementsByTagName("Signature")[0], True)
sigs.appendChild(sig_ele)
self.xml = doc.toxml()
# Split the issuer GID into multiple certificates if it's a chain
chain = GID(filename=self.issuer_gid)
gid_files = []
while chain:
gid_files.append(chain.save_to_random_tmp_file(False))
if chain.get_parent():
chain = chain.get_parent()
else:
chain = None
# Call out to xmlsec1 to sign it
ref = 'Sig_%s' % self.get_refid()
filename = self.save_to_random_tmp_file()
signed = os.popen('%s --sign --node-id "%s" --privkey-pem %s,%s %s' \
% (self.xmlsec_path, ref, self.issuer_privkey, ",".join(gid_files), filename)).read()
os.remove(filename)
for gid_file in gid_files:
os.remove(gid_file)
self.xml = signed
# This is no longer a legacy credential
if self.legacy:
self.legacy = None
# Update signatures
self.decode()
##
# Retrieve the attributes of the credential from the XML.
# This is automatically called by the various get_* methods of
# this class and should not need to be called explicitly.
def decode(self):
if not self.xml:
return
doc = parseString(self.xml)
sigs = []
signed_cred = doc.getElementsByTagName("signed-credential")
# Is this a signed-cred or just a cred?
if len(signed_cred) > 0:
cred = signed_cred[0].getElementsByTagName("credential")[0]
signatures = signed_cred[0].getElementsByTagName("signatures")
if len(signatures) > 0:
sigs = signatures[0].getElementsByTagName("Signature")
else:
cred = doc.getElementsByTagName("credential")[0]
self.set_refid(cred.getAttribute("xml:id"))
self.set_lifetime(parse(getTextNode(cred, "expires")))
self.gidCaller = GID(string=getTextNode(cred, "owner_gid"))
self.gidObject = GID(string=getTextNode(cred, "target_gid"))
# Process privileges
privs = cred.getElementsByTagName("privileges")[0]
rlist = RightList()
for priv in privs.getElementsByTagName("privilege"):
kind = getTextNode(priv, "name")
deleg = str2bool(getTextNode(priv, "can_delegate"))
if kind == '*':
# Convert * into the default privileges for the credential's type
_ , type = urn_to_hrn(self.gidObject.get_urn())
rl = rlist.determine_rights(type, self.gidObject.get_urn())
for r in rl.rights:
rlist.add(r)
else:
rlist.add(Right(kind.strip(), deleg))
self.set_privileges(rlist)
# Is there a parent?
parent = cred.getElementsByTagName("parent")
if len(parent) > 0:
parent_doc = parent[0].getElementsByTagName("credential")[0]
parent_xml = parent_doc.toxml()
self.parent = Credential(string=parent_xml)
self.updateRefID()
# Assign the signatures to the credentials
for sig in sigs:
Sig = Signature(string=sig.toxml())
for cur_cred in self.get_credential_list():
if cur_cred.get_refid() == Sig.get_refid():
cur_cred.set_signature(Sig)
##
# Verify
# trusted_certs: A list of trusted GID filenames (not GID objects!)
# Chaining is not supported within the GIDs by xmlsec1.
#
# Verify that:
# . All of the signatures are valid and that the issuers trace back
# to trusted roots (performed by xmlsec1)
# . The XML matches the credential schema
# . That the issuer of the credential is the authority in the target's urn
# . In the case of a delegated credential, this must be true of the root
# . That all of the gids presented in the credential are valid
# . The credential is not expired
#
# -- For Delegates (credentials with parents)
# . The privileges must be a subset of the parent credentials
# . The privileges must have "can_delegate" set for each delegated privilege
# . The target gid must be the same between child and parents
# . The expiry time on the child must be no later than the parent
# . The signer of the child must be the owner of the parent
#
# -- Verify does *NOT*
# . ensure that an xmlrpc client's gid matches a credential gid, that
# must be done elsewhere
#
# @param trusted_certs: The certificates of trusted CA certificates
def verify(self, trusted_certs):
if not self.xml:
self.decode()
# trusted_cert_objects = [GID(filename=f) for f in trusted_certs]
trusted_cert_objects = []
ok_trusted_certs = []
for f in trusted_certs:
try:
# Failures here include unreadable files
# or non PEM files
trusted_cert_objects.append(GID(filename=f))
ok_trusted_certs.append(f)
except Exception, exc:
sfa.util.sfalogging.logger.error("Failed to load trusted cert from %s: %r", f, exc)
trusted_certs = ok_trusted_certs
# Use legacy verification if this is a legacy credential
if self.legacy:
self.legacy.verify_chain(trusted_cert_objects)
if self.legacy.client_gid:
self.legacy.client_gid.verify_chain(trusted_cert_objects)
if self.legacy.object_gid:
self.legacy.object_gid.verify_chain(trusted_cert_objects)
return True
# make sure it is not expired
if self.get_lifetime() < datetime.datetime.utcnow():
raise CredentialNotVerifiable("Credential expired at %s" % self.expiration.isoformat())
# Verify the signatures
filename = self.save_to_random_tmp_file()
cert_args = " ".join(['--trusted-pem %s' % x for x in trusted_certs])
# Verify the gids of this cred and of its parents
for cur_cred in self.get_credential_list():
cur_cred.get_gid_object().verify_chain(trusted_cert_objects)
cur_cred.get_gid_caller().verify_chain(trusted_cert_objects)
refs = []
refs.append("Sig_%s" % self.get_refid())
parentRefs = self.updateRefID()
for ref in parentRefs:
refs.append("Sig_%s" % ref)
for ref in refs:
verified = os.popen('%s --verify --node-id "%s" %s %s 2>&1' \
% (self.xmlsec_path, ref, cert_args, filename)).read()
if not verified.strip().startswith("OK"):
raise CredentialNotVerifiable("xmlsec1 error verifying cert: " + verified)
os.remove(filename)
# Verify the parents (delegation)
if self.parent:
self.verify_parent(self.parent)
# Make sure the issuer is the target's authority
self.verify_issuer()
return True
##
# Creates a list of the credential and its parents, with the root
# (original delegated credential) as the last item in the list
def get_credential_list(self):
cur_cred = self
list = []
while cur_cred:
list.append(cur_cred)
if cur_cred.parent:
cur_cred = cur_cred.parent
else:
cur_cred = None
return list
##
# Make sure the credential's target gid was signed by (or is the same) the entity that signed
# the original credential or an authority over that namespace.
def verify_issuer(self):
root_cred = self.get_credential_list()[-1]
root_target_gid = root_cred.get_gid_object()
root_cred_signer = root_cred.get_signature().get_issuer_gid()
if root_target_gid.is_signed_by_cert(root_cred_signer):
# cred signer matches target signer, return success
return
root_target_gid_str = root_target_gid.save_to_string()
root_cred_signer_str = root_cred_signer.save_to_string()
if root_target_gid_str == root_cred_signer_str:
# cred signer is target, return success
return
# See if it the signer is an authority over the domain of the target
# Maybe should be (hrn, type) = urn_to_hrn(root_cred_signer.get_urn())
root_cred_signer_type = root_cred_signer.get_type()
if (root_cred_signer_type == 'authority'):
#sfa.util.sfalogging.logger.debug('Cred signer is an authority')
# signer is an authority, see if target is in authority's domain
hrn = root_cred_signer.get_hrn()
if root_target_gid.get_hrn().startswith(hrn):
return
# We've required that the credential be signed by an authority
# for that domain. Reasonable and probably correct.
# A looser model would also allow the signer to be an authority
# in my control framework - eg My CA or CH. Even if it is not
# the CH that issued these, eg, user credentials.
# Give up, credential does not pass issuer verification
raise CredentialNotVerifiable("Could not verify credential owned by %s for object %s. Cred signer %s not the trusted authority for Cred target %s" % (self.gidCaller.get_urn(), self.gidObject.get_urn(), root_cred_signer.get_hrn(), root_target_gid.get_hrn()))
##
# -- For Delegates (credentials with parents) verify that:
# . The privileges must be a subset of the parent credentials
# . The privileges must have "can_delegate" set for each delegated privilege
# . The target gid must be the same between child and parents
# . The expiry time on the child must be no later than the parent
# . The signer of the child must be the owner of the parent
def verify_parent(self, parent_cred):
# make sure the rights given to the child are a subset of the
# parents rights (and check delegate bits)
if not parent_cred.get_privileges().is_superset(self.get_privileges()):
raise ChildRightsNotSubsetOfParent(
self.parent.get_privileges().save_to_string() + " " +
self.get_privileges().save_to_string())
# make sure my target gid is the same as the parent's
if not parent_cred.get_gid_object().save_to_string() == \
self.get_gid_object().save_to_string():
raise CredentialNotVerifiable("Target gid not equal between parent and child")
# make sure my expiry time is <= my parent's
if not parent_cred.get_lifetime() >= self.get_lifetime():
raise CredentialNotVerifiable("Delegated credential expires after parent")
# make sure my signer is the parent's caller
if not parent_cred.get_gid_caller().save_to_string(False) == \
self.get_signature().get_issuer_gid().save_to_string(False):
raise CredentialNotVerifiable("Delegated credential not signed by parent caller")
# Recurse
if parent_cred.parent:
parent_cred.verify_parent(parent_cred.parent)
def delegate(self, delegee_gidfile, caller_keyfile, caller_gidfile):
"""
Return a delegated copy of this credential, delegated to the
specified gid's user.
"""
# get the gid of the object we are delegating
object_gid = self.get_gid_object()
object_hrn = object_gid.get_hrn()
# the hrn of the user who will be delegated to
delegee_gid = GID(filename=delegee_gidfile)
delegee_hrn = delegee_gid.get_hrn()
#user_key = Keypair(filename=keyfile)
#user_hrn = self.get_gid_caller().get_hrn()
subject_string = "%s delegated to %s" % (object_hrn, delegee_hrn)
dcred = Credential(subject=subject_string)
dcred.set_gid_caller(delegee_gid)
dcred.set_gid_object(object_gid)
dcred.set_parent(self)
dcred.set_lifetime(self.get_lifetime())
dcred.set_privileges(self.get_privileges())
dcred.get_privileges().delegate_all_privileges(True)
#dcred.set_issuer_keys(keyfile, delegee_gidfile)
dcred.set_issuer_keys(caller_keyfile, caller_gidfile)
dcred.encode()
dcred.sign()
return dcred
##
# Dump the contents of a credential to stdout in human-readable format
#
# @param dump_parents If true, also dump the parent certificates
def dump(self, dump_parents=False):
print "CREDENTIAL", self.get_subject()
print " privs:", self.get_privileges().save_to_string()
print " gidCaller:"
gidCaller = self.get_gid_caller()
if gidCaller:
gidCaller.dump(8, dump_parents)
print " gidObject:"
gidObject = self.get_gid_object()
if gidObject:
gidObject.dump(8, dump_parents)
if self.parent and dump_parents:
print "PARENT",
self.parent.dump_parents()