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Subject: [xacml] Minutes of 28 Oct 02 SC Meeting; also Updated Change Requests
I have removed all completely resolved items from the Summary list. I have divided the Summary list into two parts: - CRs that have been resolved by a non-quorum meeting but are awaiting a quorum vote to confirm. - CRs that still need action and resolution. For most of these we have a TENTATIVE RESOLUTION that simply needs to be written up by the person assigned the action item, then the proposal needs a final vote. Anne -- Anne H. Anderson Email: Anne.Anderson@Sun.COM Sun Microsystems Laboratories 1 Network Drive,UBUR02-311 Tel: 781/442-0928 Burlington, MA 01803-0902 USA Fax: 781/442-1692
Title: Change Requests Set 4
Author: Anne Anderson
Version: 1.13, 02/10/28 (yy/mm/dd)
Original Source: /net/labeast.east/files2/east/info/projects/isrg/xacml/docs/SCCS/s.ChangeRequests4.txt
This file contains all non-editorial Change Requests not
reflected in the v0.18c.doc version of the XACML Specification
and still open after the 17 Oct 2002 TC conference call.
Includes e-mail up through
http://lists.oasis-open.org/archives/xacml/200210/msg00286.html
See
http://lists.oasis-open.org/archives/xacml/200210/msg00214.html
for the changes previously approved to v0.18c.doc.
This document also serves as the minutes for the SC meeting on 28
Oct 2002: Present:
Simon Godik, Hal Lockhart, Tim Moses, Polar Humenn, Anne Anderson (scribe)
ACTION ITEMS
============
0134c: Need Datatypes for each defined AttributeId
ACTION ITEM: [Simon] Propose types for each XACMl-defined attribute-id
0134f: Missing status codes
ACTION ITEM: [Seth] supply list of additional codes.
0141: data type uri's
ACTION ITEM: [All] Weigh in with opinions.
0142: bags and targets. Forwarded message from Seth Proctor.
ACTION ITEM: [Anne] Write up TENTATIVE RESOLUTION with details spelled out.
0143: 6.15 status detail formats
ACTION ITEM: [Seth Proctor] Write up details for Tentative Resolution.
0148a: Example two rules not applicable to request
ACTION ITEM: [Simon] Review and revise as needed.
0148b: Include target-namespace in Request Context?
ACTION ITEM: [Simon] Review and revise as needed.
0148c: Syntax of RequestContextPath not consistent
ACTION ITEM: [Simon] Review and revise as needed.
0148d: Move "disjunctive sequence" up to higher element description
ACTION ITEM: [Simon] Review and revise as needed.
SUMMARY OF ITEMS STILL NOT COMPLETELY RESOLVED
==============================================
LEGEND
======
NQ=no quorum; official vote required
Q=quorum
NEED OFFICIAL VOTE ONLY
=======================
0076: [Anne] AA02: New section in Appendix A on Structured datatypes
STATUS: Need final vote (NQ 10/21). See TENTATIVE RESOLUTION.
0092: [Polar] PH09: New section 7.4.2 Attributes
STATUS: Tentative approval (NQ 10/17). 7.4.2.2 revised. Needs final vote.
0098: [Anne] AA11: Clarify "MatchId" functions
STATUS: CLOSED (NQ 10/28): allow any boolean function that takes two arguments.
0101: [Satoshi Hada] SatoshiHada01: How many namespaces does XACML define?
STATUS: CLOSED (NQ 10/28). Use URI for everything. TENTATIVE RESOLUTION rejected.
0134a: [Seth Proctor] Policy Target computed before arriving at PDP
STATUS: CLOSED (NQ 10/28). Current version is OK.
0140: [Michiharu] MK01: DataType and Namespace
STATUS: CLOSED (NQ 10/28). Use URI for everything.
SEE ALSO: CR#0101,0132,0141
0144: [Polar] harmful to interoperability
STATUS: APPROVED (NQ 10/28). Reword as suggested. Don't talk about harmful anything.
0145: [Seth Proctor] Multi-valued attributes in Request.
STATUS: APPROVED (NQ 10/28) Change to maxOccurs=1.
0146: [Polar] CR 144: function "present" needs to be fixed.
STATUS: APPROVED (NQ 10/28). See RESOLUTION.
0147: [Seth Proctor] Bug in pseudocode for Only One Applicable.
STATUS: APPROVED (NQ 10/28). Polar will reword.
0149: [Seth Proctor] Environment attributes
STATUS: CLOSED (NQ 10/28). See RESOLUTION.
STILL NEED REVIEW AND ACTION
============================
0134c: [Seth Proctor] Need Datatypes for each defined AttributeId
STATUS: See TENTATIVE RESOLUTION (10/24). Waiting on Simon's list.
0134f: [Seth Proctor] Missing status codes
STATUS: Seth requested to supply list of additional codes. (10/24).
0141: [Simon] SG[??]: data type uri's
STATUS: UNRESOLVED (10/28). See TENTATIVE RESOLUTION.
0142: [Seth Proctor] bags and targets. Forwarded message from Seth Proctor.
STATUS: UNRESOLVED (10/28). See TENTATIVE RESOLUTION.
0143: [Seth Proctor] 6.15 status detail formats. Forwarded message from SethProctor.
STATUS: See TENTATIVE RESOLUTION (NQ 10/28).
0148a: [Yassir Elley] Example two rules not applicable to request
STATUS: (10/28) Waiting on Simon's review and/or revision.
0148b: [Yassir Elley] Include target-namespace in Request Context?
STATUS: (10/28) Waiting on Simon's review and/or revision.
0148c: [Yassir Elley] Syntax of RequestContextPath not consistent
STATUS: (10/28) Waiting on Simon's review and/or revision.
0148d: [Yassir Elley] Move "disjunctive sequence" up to higher element description
STATUS: (10/28) Waiting on Simon's review and/or revision.
0152: [Tim Moses] Trivial Matter
STATUS: Not yet considered.
DETAILS
==================================================================
0076: [Anne] AA02: New section in Appendix A on Structured datatypes
e-mail sent 11 Oct 2002 10:27:09 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00124.html
http://lists.oasis-open.org/archives/xacml/200210/msg00209.html (revised)
STATUS: Need final vote (NQ 10/21). See TENTATIVE RESOLUTION.
TENTATIVE RESOLUTION: 10/21 meeting reached following tentative
resolution, but it involves enough of a change that members
need to see the actual revised text before voting.
TEXT LOCATION: Section A, following "A.2 Primitive
types" (p. 86, between lines 3345 and 3346 in my copy of 0.18c)
TEXT CHANGE: Add following new section as follows:
A.3 Structured types
An XACML <AttributeValue> MAY contain an instance of a
structured xml data type, for example <ds:KeyInfo>.
Structured data types MAY be structured XML data or MAY use
other encodings, such as DER-encoded ASN.1. XACML 1.0
supports several ways for comparing such <AttributeValue>s.
1) In some cases, such an <AttributeValue> MAY be compared
using one of the XACML-defined functions,such as
regexp-string-match or hexBinary-equal, described below.
In this case, the structured data, including its tags and
attributes, SHALL use the DataType corresponding to the
function to be used, both in the Policy
AttributeDesignators and Selectors and in the Request
Attribute.
In general, this method will not be adequate unless the
structured data type is quite simple.
2) An <AttributeSelector> element MAY be used to select the value
of a leaf sub-element of an XML structured data type.
That value MAY then be compared using one of the supported
XACML functions appropriate for its primitive data type.
This method requires support by the PDP for the optional
XPath expressions feature.
3) An <AttributeSelector> element MAY be used to select the value
of any node in an XML structured type. This node MAY then
be compared using one of the XPath-based functions
described in "Section A.13.13 XPath-based functions".
This method requires support by the PDP for the optional
XPath expressions and XPath functions features.
See Section 8. XACML extensibility points for further ways in
which structured data types may be handled.
TEXT LOCATION: 8. XACML extensibility points
TEXT CHANGE: Add following new section:
8.3 Structured data types
Section "A.3 Structured types" describes normative ways of
dealing with structured data types. XACML extensibility
points may be used to deal with such types in two additional
ways.
1) For a given structured data type, a new attribute
identifier MAY be defined for various leaf sub-elements of
the structured data type. The structured data is
presented to the PDP in the Request Context as a sequence
of <Attribute>s that use the new identifiers. Each such
<Attribute> MAY be compared using the XACML-defined
functions.
This method requires support by the PEP or Context Handler
for flattening the structured data type into the sequence
of individual <Attribute>s using the new attribute
identifiers. Using this method, the structured data type
itself never appears in an <AttributeValue> element.
2) A new function MAY be defined for comparing a value of the
structured datatype against some other value.
This method requires support by the PDP for the new
function.
==================================================================
0086: [Hal] HL03: Question about Anonymous Access Subject
e-mail sent 11 Oct 2002 11:56:37 -0400
http://lists.oasis-open.org/archives/xacml/200210/msg00126.html
STATUS: REJECTED (Q 10/17): submit specific proposals if explicit "anonymous" support needed.
Is there a cannonical way to represent an anonymous access
subject in the Request Context? This seems to me to be an
extremely common case that should be described in the spec. (My
preference would be to leave out the access subject entirely,
but I see that it is mandatory)
DISCUSSION:
[Anne] Yes, there is a canonical way. The sequence of
Attributes under <Subject> is minOccurs=0, so you can have a
Request Context in which the one <Subject> element has no
Attributes (such as no subject-id).
[Polar] A question that we are wrestling with in our logical
analysis of the security protocols, namely CSIv2, is whether
not having a prncipal is really an anonymous principal.
I think we are finding that there is a "default" principal, of
which you associated a principal with by either configuration
(let's say a request that comes over a VPN).
Also, you can assert an anonymous principal, which actually
states that you really do not know who it is. This principal is
supremely weaker than all other principals.
We might come up with a particular identifier saying
"Anonymous", but should make sure it isn't used for the
"default" case, unless the default case is truly anonymous.
In constrast to the default case, we could have a "default"
principal id, or, we direct the PEP to "fill" the principal in
with the default principal's id.
[Daniel] ..And to write rules on anonymous subject I presume
one has to use <anysubject> for target? Right? Does missed
subject have applicable rules written on <anysubject> ?
[Bill] that was my understanding.
[10/17 concall] Current document does not contain any
references to "anonymous".
If someone thinks we need explicit text on how to deal with
"anonymous" subjects, or if someone thinks we need an explicit
identifier for an "anonymous" subject, then that person needs
to submit a new change request with a use case, specific
locations to change, and specific text to use.
We may want to submit to SAML some specific values for the
"authn-method" attribute, such as: "intentionally anonymous",
"not authenticated", "authenticated by say so", "unknown", etc.
"No subject attributes" is not equivalent to "anonymous".
We agreed that it is permissible to omit all <Attribute>s from
the <Subject> and it is possible to refer to such a <Subject>
by using <AnySubject>. Neither of these requires any changes
to the existing text or schemas.
==================================================================
0092: [Polar] PH09: New section 7.4.2 Attributes
e-mail sent 11 Oct 2002 16:13:36 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00141.html
http://lists.oasis-open.org/archives/xacml/200210/msg00207.html (revised 7.4.2.2)
STATUS: Tentative approval (NQ 10/17). 7.4.2.2 revised. Needs final vote.
TEXT LOCATION: Following Section 7.4.1 "Hierarchi[c]al
resources", p. 70, after line 2911, and following the approved
sections "7.4.2 Attributes" and "7.4.2.1 Attribute Retrieval"
shown in DISCUSSION section below.
TEXT CHANGE: Add following new section:
7.4.2.2 Missing Attributes
The PDP SHALL consider an attribute as missing if it
evaluates an expression that requires at least one value to
be present from an attribute designator or selector. In this
case, the expression evaluates to "indeterminate". The PDP
may carry the missing attribute upward in its indeterminate
value in accordance with the XACML evaluation strategy of the
encompassing expressions, rules, policies, and policy
sets. If the PDP evaluates its policy or policy set to
Indeterminate with a missing attribute, the PDP MAY list the
AttributeId and DataType of that attribute in the result as
described in Section 7.5 "Authorization decision". However,
the PDP MAY choose not to issue such information due to
security concerns.
DISCUSSION: On 17 Oct 2002, we approved the following sections.
Polar was asked to revise the "Missing Attributes" section that
followed, and that is what is shown above.
7.4.2 Attributes
Attributes are specified in the request context and are
referred to in the policy by the subject, resource, action,
and environment attribute designators or selectors. Each
attribute specifies an AttributeId and a DataType, and each
attribute desigator specifies an AttributeId and
DataType. Attribute Designators and Attribute Selectors SHALL
match attributes by using string equality on both the
AttributeId and DataType values.
7.4.2.1 Attribute Retrieval
The PDP SHALL retrieve the values of attributes that match
the particular attribute designator or attribute selector and
form them into a bag of values with the specified
DataType. If no attributes from the request context match,
the attribute shall be considered missing, and an empty bag
is said to be retrieved.
==================================================================
0098: [Anne] AA11: Clarify "MatchId" functions
e-mail sent 14 Oct 2002 09:48:04 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00151.html
STATUS: CLOSED (NQ 10/28): allow any boolean function that takes two arguments.
TEXT LOCATION: Section A.11 Matching elements, p. 89, lines
3446-3456.
TEXT CHANGE: [Bag functions omitted per comment from Polar]
Replace following paragraph:
"The match elements: <SubjectMatch>, <ResourceMatch> and
<ActionMatch> SHALL use XACML standard functions to perform
the match evaluation. The function used for determining a
match is named in the MatchId attribute of these elements.
Each of these elements contains a <AttributeDesignator> or
<AttributeSelector> element and an explicit attribute value.
The restriction on the function is that the MatchId attribute
must name a binary function, such that its result type is
"xs:boolean". Also, each argument to the named function must
match the appropriate primitive types for the
<AttributeDesignator> or <AttributeSelector> element and the
following explicit attribute value, such that the explicit
attribute value is placed as the first argument to the
function, while an element of the bag returned by the
<AttributeDesignator> or <AttributeSelector> element is placed
as the second argument to the function."
with the following:
"The match elements: <SubjectMatch>, <ResourceMatch> and
<ActionMatch> SHALL use functions that match two arguments,
returning a result type of "xs:boolean", to perform the match
evaluation.The function used for determinaing a match is named
in the MatchId attribute of these elements. Each argument to
the named function must match the appropriate primitive types
for the <AttributeDesignator> or <AttributeSelector> element
and the following explicit attribute value, such that the
explicit attribute value is placed as the first argument to
the function, while an element of the bag returned by the
<AttributeDesignator> or <AttributeSelector> element is placed
as the second argument to the function.
The XACML standard functions that may be used as a MatchId
attribute value are:
function:*-equal
function:*-greater-than
function:*-greater-than-or-equal
function:*-less-than
function:*-less-than-or-equal
function:*-match
DISCUSSION: explanation of which functions may be used as MatchId
functions is not clear. Also, function used need not be a
"standard" function as long as it returns a boolean and its
arguments follow the required format.
[10/17 concall] Disagreement on whether functions used in
<Target> MUST be XACML standard functions, or whether they can
be any function of the specified form (returns binary, takes
two arguments where first is explicit attribute value and
second is Designator or Selector.
Also, if XACML standard functions required, which ones are
permitted. Polar and Daniel support just *-equal functions in
MatchId. Hal and Tim support *-equal and *-match functions in
MatchId. Anne supports *-equal, *-match, *-great-than*, and
*-less-than* functions in MatchId (i.e. any two-argument
function that returns boolean).
There appear to be three points of view with respect to use of
<Target> that would determine which functions are appropriate:
1) <Target>/<Condition> is a way to divide the evaluation into
an "easy" part and a "hard" part, so that many potentially
applicable policies can be easily eliminated without having
to evaluate the "hard" part. The policies may be in a
database, or may be explicitly included or referenced from
another policy set. Target is an aid to indexing, but is
not the complete way policies are indexed. [This view is
reflected in this Change Request]
2) <Target> is designed to help search for the initial
applicable policy in a database based on an incoming
request. Any functions of the specified type (return
boolean, take Designator/Selector and explicit
AttributeValue as two args) that are supported by SQL and
LDAP should be permitted.
3) <Target> is designed for searching an index of potential
policies or rules. Only XACML standard *-equal functions
should be permitted in a "MatchId".
Apparently, there was a vote taken on this earlier that
supported 3), and Daniel was apparently strongly in favor of
this. [Anne: I can not find any record of such a vote].
Use cases and more discussion are required to resolve this.
==================================================================
0100: [Steve Hanna] SteveHanna01: integer-mod takes two arguments
personal communication to Anne Anderson on 14 Oct 2002
STATUS: APPROVED (Q 10/24). Use proposed text.
TEXT LOCATION: Section A.13.2 Arithmetic functions, p. 92,
4569, list of functions that take a single argument.
TEXT CHANGE: Move "integer-mod" up to the list of functions
that take two arguments.
==================================================================
0101: [Satoshi Hada] SatoshiHada01: How many namespaces does XACML define?
e-mail to xacml-comment 15 Oct 2002 13:51:19 +0900
STATUS: CLOSED (NQ 10/28). Use URI for everything. TENTATIVE RESOLUTION rejected.
SEE ALSO: CR#0140,0141
TENTATIVE RESOLUTION: Use QName for DataType, URI for
everything else. [REJECTED]
Changes required:
1) Define new namespace for XACML datatype in B.1:
urn:oasis:names:tc:xacml:1.0:datatype
2) In schemas, define DataType attribute type as a QName.
3) Statement like: We recommend use of the following QName
xmlns prefixes. [To make policies easier to read]
xsi: <XML Schema Instance namespace>
xs: <XML Schema namespace>
ds: <XML Digital Signature namespace>
?: urn:oasis:names:tc:xacml:1.0:datatype
?: urn:oasis:names:tc:xacml:1.0:context (used by XPath expression)
DISCUSSION:
It is unclear to me how many namespaces XACML tries to define.
Appendix B.1 says that the following two namespace URIs are defined.
urn:oasis:names:tc:xacml:1.0:policy
urn:oasis:names:tc:xacml:1.0:context
However, it seems to me that XACML tries to define at least two other
namespaces.
(1) One is for function identifiers, i.e.,
urn:oasis:names:tc:xacml:1.0:function. Indeed, the type of
the "FunctionID" attribute is xs:QName and so I think this
URN should be one of namespace URIs defined in the XACML
specification.
(2) The other is for data types, i.e.,
urn:oasis:names:tc:xacml:1.0:datatype. Currently, the type
of the "DataType" attribute is xs:anyURI.
I think it should be xs:QName and this URN should be one of
namespace URIs defined in the XACML specification.
[10/24/02 con call]
[Anne] Should we also define namespaces for attribute
categories, status codes, subject-categories?
[Simon] No. Use QNames for datatypes, since xsi:string,
etc. are commonly used.
[Tim] Aren't QNames are used for names taken from schemas?
[Simon] No. It is just a syntactic structure with no semantics
behind it. Used for value of an attribute. It is an XML
datatype.
[Hal] A QName is a macro-expansion facility. Used in lots of
schemas and specifications.
[Tim] WSS uses QName for encoding type. Just an identifier.
[Polar] Type needs to be either a QName or a URI, can't be
both.
[Satoshi Hada] So the tentative resolution says that we should
write a condition by using URI rather than QName to specify
function identifiers. Please correct me if I'm wrong. [See
http://lists.oasis-open.org/archives/xacml/200210/msg00278.html
for two examples]
[Simon, responding to Satoshi Hada] That is correct
[Anne, asking general questions about QNames]
1. If an xml attribute is defined as Type="xs:QName", then do XML
parsers like SAX and DOM do the resolution of those names?
Example: Assume AttributeDesignatorType is defined as follows:
<xs:complexType name="AttributeDesignatorType">
<xs:attribute name="AttributeId" type="xs:QName" use="required"/>
<xs:attribute name="DataType" type="xs:anyURI" use="required"/>
<xs:attribute name="Issuer" type="xs:anyURI" use="optional"/>
</xs:complexType>
Then, if my Policy says
<Policy xmlns="urn:oasis:names:tc:xacml:1.0:policy"
xmlns:sun-attrs="urn:sun:names:attribute-ids"
...
<SubjectAttributeDesignator AttributeId="sun-attrs:attr1"
.../>
And a Request says
<Request xmlns="urn:oasis:names:tc:xacml:1.0:context"
xmlns:sun-stuff="urn:sun:names:attribute-ids"
...
<Subject>
<Attribute AttributeId="sun-stuff:attr1">
...
Will the tools themselves resolve these, or do I have to
expand the names and then perform a string match myself?
Simon> By looking at the sax api it does not seem that
Simon> anything is done with attribute values of qname type.
Simon> My guess is that an application is responsible for
Simon> expanding qname. Problem is that expanded name is a
Simon> pair: (URI, local_name) and there is no standard that
Simon> says how this 2 elements should be combined to form one
Simon> value. Some suggest URI+local_name, others
Simon> URIlocal_name, and so on.
Simon> My preference would be not to use qnames for attribute
Simon> values at all, and use URI's instead.
Anne> But then what do we do about DataType values such as
Anne> xsi:string that are already defined as QNames?
2. Does anyone have a reference from W3C on whether QNames MAY be
used as "aliases" for any URI or whether they are ONLY for use
in referring to URI's that represent schemas?
I.e. are the uses of QNames for use in identifiers as in #1
and in our current schemas even allowed (or recommended)?
3. Is there a way to define aliases for shortcut names other than
QNames? I.e. can I define an alias to be equal to some
initial prefix of a long URI, and then have that expanded by
XML parsing tools?
==================================================================
0102: [Anne] AA13: Remove B.11 Identifiers used in conformance tests
e-mail sent 14 Oct 2002 09:58:56 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00154.html
STATUS: APPROVED (Q 10/24). Use proposed text.
TEXT LOCATION: Section B.11, p. 111, lines 4325-4328
TEXT CHANGE: remove entire Section "B.11 Identifiers used only
in XACML conformance tests"
DISCUSSION: just as for identifiers used in examples, I don't
think we need to spell out the identifiers used in conformance
tests.
==================================================================
0121: [Anne] AA32: clarify use of "dn"
e-mail sent 14 Oct 2002 12:59:38 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00177.html
STATUS: APPROVED (Q 10/24). Use proposed text.
TEXT LOCATION: Section 6.7 Element <Attribute>, description of
"Issuer [Optional]", p. 64, line 2685
TEXT CHANGE: replace "This MAY be a dn that binds to a public
key" with "This attribute value MAY be an X.500 Distinguished
Name that binds to a public key"
==================================================================
0132: [Anne] AA43: use "xs:" or "xsi:"?
e-mail sent 14 Oct 2002 13:36:53 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00187.html
STATUS: CLOSED (Q 10/24) See RESOLUTION below
SEE ALSO: CR#0101,0140,0141
RESOLUTION: Use xsi:string, etc. for XML Schema-defined
datatypes in examples. Use xs:any, etc. in schema
definitions.
DISCUSSION: In some places we use "xsi:<some datatype>", while
in other places we use "xs:<some datatype>". We should pick
one. I propose "xs:" just because it is shorter.
[Tim] Example: p. 64 <Decision> is restriction on xs:string.
xsi only used in examples.
==================================================================
0134a: [Seth Proctor] Policy Target computed before arriving at PDP
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
STATUS: CLOSED (NQ 10/28). Current version is OK.
3.3.2.1 (PolicyTarget) still makes it unclear that Policy
Target is computed before arriving at the PDP.
0134b: [Seth Proctor] Add pointer to higher-order bag function to Apply
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
STATUS: APPROVED (Q 10/24). Add pointer as in Anne's comment.
In section 5, when the <Function> tag is explained in Apply, it
should have a pointer to the higher-order bag section so people
understand what it's there for
DISCUSSION:
[Anne] To be more specific, in Section 5.21 Element <Apply>,
explanation of <Function> [Optional], p. 54, line 2260,
following "The name of a function that is applied to the
elements of a bag.", append: "See Section A.13.11 Higher-order
bag functions."
0134c: [Seth Proctor] Need Datatypes for each defined AttributeId
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
10.3.6 (Identifiers) doesn't list the type of any these
attributes, nor does it give the required uses for them that it
says implementors must follow. I realize this is transparent to
a lot of the code, and only one of these is required to
support, but it would still be helpful to know what type
they're supposed to be (if there is a certain expected
type). Later in the spec they're explained in a little more
detail, but not enough to make the strong language in this
section about correct implemention make sense.
ACTION ITEM: [Simon] Propose types for each XACMl-defined attribute-id
STATUS: See TENTATIVE RESOLUTION (10/24). Waiting on Simon's list.
SEE ALSO: CR#0150
TENTATIVE RESOLUTION: Each "standard attribute" should have a
"standard datatype", since we proposed them for
interoperability in the first place. Simon will come up with
a proposal with types for each standard attribute, and we can
then vote on it.
DISCUSSION:
[Anne] I don't think there is a specified type for these. You
specify the type using the XML Datatype="" attribute. One user
might specify key-info, for example, using a SubjectKeyInfo
from PKIX, while another might use a ds:KeyInfo structure.
0134d: [Seth Proctor] Fix examples in Section A to include DataType
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
A.6 (Element <AttributeValue>) says that an AttributeValue's
type is implied by the function using it, but that's changed
now to state the type explicitly (same for next 2
sections)...actually, this change is missing in most of the
section A examples.
STATUS: APPROVED (Q 10/24). Fix all examples in A to include DataType.
0134e: [Seth Proctor] Bag input to single param function error; bags of any type
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
1) A.11 (Matching elements) says that the AD/AS used in a Target
match must return a bag, and then has some other language
that borders on describing an API. I think it should be made
clear that if a function expects a single String (eg), then
getting a bag is an error.
2) Also, this section (and the section later describing bags)
should clarify that _any_ type is allowed in a bag, not just
those defined as base types in the spec. If you'd like, I
can work on alternate language.
STATUS: CLOSED (Q 10/24): See RESOLUTION
RESOLUTION:
1) APPROVED: Any type allowed in a bag (i.e. user-defined types
as well as XACML-defined types). Wording in A.11 and A.13.9
should be changed to reflect this.
2) REJECTED: Already specified.
A.14.1 Equality predicates,
example: boolean-equal: "This function SHALL take two
arguments of xs:boolean".
A.14.2 Arithmetic functions
Starts with "All of the following functions SHALL take
two elements of the specified type, integer or decimal."
A.14.3 String conversion functions
example: string-normalize-space: "This function SHALL
take one argument of type 'xsi:string'..."
etc.
0134f: [Seth Proctor] Missing status codes
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
B.9 (Status codes) is still missing some of the codes that we
discussed (like problems choosing the root policy). Maybe a few more
could be added. Maybe I should writeup a few other codes, and include
some proposal for the format of the values to accompany various
Status codes?
ACTION ITEM: [Seth] supply list of additional codes.
STATUS: Seth requested to supply list of additional codes. (10/24).
SEE ALSO: CR#0143, which proposes formats.
0134g: [Seth Proctor] Acknowledgments/Contributions
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
D (Acknowledgments) ... this is a small issue, but since the
list of voting memebers is basically also the contributer list,
shouldn't this section name people who weren't on the TC but
helped shape the standard? This is the way other specs look.
STATUS: APPROVED (Q 10/24). See RESOLUTION.
RESOLUTION: Include Seth, Pierangela, Ernesto, etc. on front
page "Contributors" (everyone who made substantial
contributions during development of sepcification). Appendix
D will include only voting members at the time of approval for
Committee Spec.
0134h: [Seth Proctor] Should SubjectADWhere extend SubjectAD?
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
Should SubjectAttributeDesignatorWhere extend SubjectAD now instead of
just AD? Before it made sense, since all ADs were the same, but I
would think that since there's now a special AD for Subjects, that's
what you would want to extend.
STATUS: REJECTED (Q 10/24). See Simon's comment.
DISCUSSION:
[Simon] if we extend subj-attr-desig <-
subject-attr-desig-where we will inherit subject-category
attribute. Having subject-category in subject-attr-desig is
confusing.
0134i: [Seth Proctor] Treating Request as notional document
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
There is still no discussion anywhere about treating the Request as a
notional doc and going outside the PDP to get attribute values. The
same text is still throughout the spec suggesting just the opposite,
and the picture at the beginning looks the same. I know you're thinking
about how to change this, but if this is really supposed to be supported,
then the spec _must_ change dramatically to make this clear. One or
two paragraphs added somewhere will not cut it.
STATUS: CLOSED (Q 10/24). Provide specific wording if still needed.
SEE ALSO: CR#0135, CR#0136
DISCUSSION:
[Anne] Some of the "one or two paragraphs added somewhere"
are in a new section proposed in CR#092: "7.4.2 Attributes"
that includes subsections on Attribute Retrieval and Missing
Attributes. The rest is already in the document in Section
7.7 Use profile for XACML request.
If more text is needed to make these sections clear, please
propose it.
0134j: [Seth Proctor] Examples for using AD/AS with "notional" Request
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
There needs to be some clear examples of how to use an AD/AS to
make [treating Request as notional document] happen. I don't
think that AS's should be used for this functionality (just
because it's too hard to support), but that's a separate issue.
STATUS: CLOSED (Q 10/24). Provide specific wording if still needed.
DISCUSSION:
[Anne] Isn't that an implementation issue? The spec should
just specify the desired behavior, not how it is achieved.
0134k: [Seth Proctor] Describe how Policy[Set]Ids should be treated
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
There should probably be some language added to discuss how
Policy[Set] Ids should be treated. At the very least, and
example or some hints about typical use would make things
better, since right now this is entirely up to the implementor,
and as such is guarenteed to be a point where interoperability
of policies fails.
STATUS: REJECTED (Q 10/24). See RESOLUTION.
RESOLUTION: Out of scope. Id MUST be a URI, but we don't force
URN or URL. Anne is thinking of writing another specification
for an extension or wrapper for an XACML policy that specified
via URLs where to find things like: policy ids, executable code
for functions, attributes, PAP's, AA's. Basically a schema for
mapping various IDs in various contexts to URLs.
0134l: [Seth Proctor] How to do resolution in an Apply
e-mail sent 16 Oct 2002 11:16:30 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00192.html
There is still no text about how to do resolution in an Apply,
and how this can be short-circuited, etc. The current spec
doesn't make it clear that you should be able to do this, so I
think this needs to be added in clear examples & specification,
otherwise not all implementors will get this right.
STATUS: REJECTED (Q 10/24). Already specified. See RESOLUTION.
RESOLUTION: Already clearly laid out in A.13.5 for logical
functions. Bag functions refer to these. Laid out in first
paragraph of A.13.2 for Arithmetic functions (if any argument
is missing, then expression is "indeterminate". Laid out at
beginning of description of each other type of function.
==================================================================
0135: [Anne] AA45: make data-flow diagram consistent with 7.7 Use profile for XACML request
e-mail sent 16 Oct 2002 14:32:00 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00195.html
STATUS: (Q 10/24). See RESOLUTION
RESOLUTION: Don't touch diagram. However, 8 should say
"Context Handler supplies information about the Request Context
to the PDP."
SEE ALSO: CR#0134i
TEXT LOCATION: 3.1 Data-flow model, Figure 1 - Data-flow diagram
TEXT CHANGE: Replace diagram with:
access requester --2. access request----> PEP --13. obligations--> obligations
| ^ service
| |
3. request 12. response
| |
| |
V |
PDP <--4. request notification---- context handler <---8. resource--> resource
content
---5. attribute queries------>
^ <--10. attributes------------
| --11. response context-------->
| | ^ ^
| | | |--9. environment--> environment
| | | attributes
| | |
| 6. attribute 7. attributes
| queries |
1. policy | |
| | |
| V |
PAP PIP
TEXT LOCATION: 3.1 Data-flow model, Steps 1-12
TEXT CHANGE: Replace text for steps as follows:
1. PAPs write policies and make them available to the PDP.
2. The access requester sends a request for access to the PEP.
3. The PEP sends the request for access to the context handler in
its native request format, optionally including additional
attributes of the subjects, resource and action. The
context handler translates the information in the native
request into a form consistent with an XACML Request Context
(see Section 7.7 Use profile for XACML request).
4. The PEP notifies the PDP that a request is available for
evaluation.
5. Based on its initial policy (see Section 7.1 Initial
policy), the PDP issues attribute queries to the context
handler based on the attributes required to evaluate the
initial policy and those policies referenced from it.
Attribute queries are expressed in the form of
AttributeDesignators or AttributeSelectors.
6. The context handler may issue attribute queries to a PIP in
order to resolve attributes not present in the native
request.
7. The PIP returns the requested attributes to the context
handler.
8. The context handler may optionally obtain information from
the resource itself.
9. The context handler may optionally obtain information from
the environment.
10. The context handler makes the requested attributes available
to the PDP "as if" the requested attributes were located in
a Request Context. The PDP evaluates the policy.
11. The PDP returns the response context (including its
decision) to the context handler.
12. The context handler translates the response context to the
native response format of the PEP. The context handler
returns the response to the PEP.
13. The PEP fulfills the obligations
14. (Not shown) if access is permitted, then the PEP permits
access to the resource; otherwise, it denies access.
DISCUSSION: Make diagram and steps consistent with respect to
"notional" Request Context and how/when attributes are obtained.
==================================================================
0136: [Anne] AA46: Make 3.2 XACML context consistent with 7.7 Use profile for XACML request
e-mail sent 16 Oct 2002 14:36:47 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00196.html
STATUS: APPROVED (Q 10/24). Use proposed text.
TEXT LOCATION: 3.2 XACML context, last paragraph. p. 17, line
560.
TEXT CHANGE: Append: "See Section 7.7 Use profile for XACML
request for more information about how the XACML request context
is handled."
==================================================================
0137: [Steve Hanna] SteveHanna02: xsi:decimal string representation
e-mail sent 16 Oct 2002 14:45:39 -0400
http://lists.oasis-open.org/archives/xacml/200210/msg00198.html
STATUS: REJECTED (Q 10/24). Stated in schema definition.
Section A.3 Representations says:
For integers and decimals, XACML SHALL use the conversions
described in IBM Standard Decimal Arithmetic document at
the following URL:
http://www2.hursley.ibm.com/decimal/decarith.html
This document combines the various standards set forth by
IEEE and ANSI for string representation of numeric values.
The IBM document defines a numeric string syntax that
allows scientific notation, NaNs, and infinities. The XML
schema document that defines the permissible contents of the
xs:decimal data type does not allow any of these.
I suggest that a note be added after the above passage,
saying:
Note that although the IBM document allows exponents,
NaNs, and infinities the XML Schema specification does
not allow these in an xs:integer and xs:decimal value.
Therefore, they MUST NOT be used in such values.
==================================================================
0138: [Steve Hanna] SteveHanna03: Use of decimal math should be justified
e-mail sent 16 Oct 2002 14:45:44 -0400
http://lists.oasis-open.org/archives/xacml/200210/msg00199.html
STATUS: APPROVED (Q 10/24): Replace "decimal" with "double".
It is unusual to specify the use of decimal math in
a specification like XACML, especially requiring strict
conformance to a detailed specification of decimal
math behavior. Many platforms do not support decimal
math. Binary math is much more common.
I can see why you might want to use decimal math for
this specification. Maybe you're likely to be doing a
lot of financial calculations. Still, I think it's a
bit odd that you require support for exponents, NaNs,
and the like in the implementation but don't provide
any way for a user to access these features. A simpler
approach would have been to leave the arithmetic
loosely specified, like XQuery has done.
At the least, I think you should add a few sentences
to the end of section A.12 Arithmetic evaluation saying
Decimal arithmetic is used in order to provide
results that closely match those expected by the
average user.
==================================================================
0139: [Steve Hanna] SteveHanna04: handling of divide-by-zero
mail sent 16 Oct 2002 14:45:48 -0400
http://lists.oasis-open.org/archives/xacml/200210/msg00188.html
STATUS: APPROVED (Q 10/24). Use proposed text.
Section A.12 Arithmetic evaluation says that trap-enablers
SHALL all be set to 0. I believe that this means that a
division by zero will produce a result of positive or
negative infinity and proceed along happily. That seems
surprising and contradicts sections 6.11 and B.9, which
imply that a division by zero will produce an indeterminate
result.
I suggest that you change section A.12 to say that all
trap-enablers SHALL be set to 0 except division-by-zero,
which SHALL be set to 1. Then you can change the description
of the integer-divide and decimal-divide functions in
section A.13.2 to say that they SHALL produce a result
of indeterminate with a processing-error status if the
divisor is 0.
==================================================================
0140: [Michiharu] MK01: DataType and Namespace
e-mail sent 17 Oct 2002 18:47:58 +0900
http://lists.oasis-open.org/archives/xacml/200210/msg00202.html
STATUS: CLOSED (NQ 10/28). Use URI for everything.
SEE ALSO: CR#0101,0132,0141
We have agreed to specify DataType attribute in both policy and
context. The schema 16j says that DataType attribute is
xs:anyURI. I think that the DataType is written as QName such
as "xs:string" and "xs:boolean" like MatchId attribute. So I
request to change DataType attribute from xs:anyURI to
xs:QName. Besides, we should add the following namespace prefix
and its namespace URI in the spec.
Prefix Namespace URI
xacml-function urn:oasis:names:tc:xacml:1.0:function
xacml-datatype urn:oasis:names:tc:xacml:1.0:datatype
*) datatype prefix is used for xacml-datatype:x500Name and
xacml-datatype:rfc822Name. In fact, prefix itself matters only
in the specification document. Policy writers can choose
another prefix as they like.
I think text that refers to ds: prefix (XML Signature
namespace) and saml: prefix no longer exist in the spec. So
line 289-290, 303-305 should be deleted.
[Satoshi Hada] I found an inconsistent use of the "DataType"
attribute.
----------------------------------------------------
<Attribute DataType="xs:string"....>
In this case, it seems to me that the attribute type is xs:QName.
----------------------------------------------------
<Attribute DataType="urn:oasis:names:tc:xacml:1.0.datatype:x500name"...>
In this case, it seems to me that the attribute type is xs:anyURI.
----------------------------------------------------
As Kudo-san is requesting, I'd request to change the type from
xs:anyURI to xs:QName.
==================================================================
0141: [Simon] SG[??]: data type uri's
e-mail sent 17 Oct 2002 09:50:15 -0700
http://lists.oasis-open.org/archives/xacml/200210/msg00208.html
ACTION ITEM: [All] Weigh in with opinions.
STATUS: UNRESOLVED (10/28). See TENTATIVE RESOLUTION.
SEE ALSO: CR#0101,0132,0140
TENTATIVE RESOLUTION: We like the list of data types and agree
they should not be QNames, but are unresolved as to whether we
use URL or URN for datatypes. If URL, then we need a way to
specify the two xacml-defined DataTypes as URLs.
XML-schema datatype namespace:
http://www.w3.org/2001/XMLSchema-datatypes
Xml data types:
http://www.w3.org/2001/XMLSchema-datatypes#string
http://www.w3.org/2001/XMLSchema-datatypes#boolean
http://www.w3.org/2001/XMLSchema-datatypes#integer
http://www.w3.org/2001/XMLSchema-datatypes#decimal
http://www.w3.org/2001/XMLSchema-datatypes#date
http://www.w3.org/2001/XMLSchema-datatypes#dateTime
http://www.w3.org/2001/XMLSchema-datatypes#anyURI
http://www.w3.org/2001/XMLSchema-datatypes#hexBinary
http://www.w3.org/2001/XMLSchema-datatypes#base64Binary
Xquery operators datatype namespace:
http://www.w3.org/TR/xquery-operators
Xquery data types:
http://www.w3.org/TR/xquery-operators#dayTimeDuration
http://www.w3.org/TR/xquery-operators#yearMonthDuration
Xacml datatype namespace:
urn:oasis:names:tc:xacml:1.0:datatype
Xacml data types:
urn:oasis:names:tc:xacml:1.0:datatype:x500Name
urn:oasis:names:tc:xacml:1.0:datatype:rfc822Name
Changes:
A2. Primitive types.
replace datatype list with the above list.
B4. Data types
replace data-type identifiers with the above list
==================================================================
0142: [Seth Proctor] bags and targets. Forwarded message from Seth Proctor.
e-mail sent 17 Oct 2002 16:43:04 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00216.html
ACTION ITEM: [Anne] Write up TENTATIVE RESOLUTION with details spelled out.
STATUS: UNRESOLVED (10/28). See TENTATIVE RESOLUTION.
TENTATIVE RESOLUTION: Create a new XML attribute on Designators
and Selectors to indicate "Must be present". This new
attribute is optional, and may be used in either Target or
Condition. Behavior of indeterminate results in Target where
AND or especially OR is being done (e.g. in multiple subjects
where only one needs to match) needs to be spelled out, but it
should follow behavior of current "and" and "or" functions.
TEXT LOCATION: Section A.11, Paragraph 3, lines3459-3461: 'If
the <AttributeDesignator> or <AttributeSelector> element
evaluates to an empty bag, then the result of the expression
SHALL be "False".'
It seems to me that an empty bag only happens if you can't
resolve a value for the attribute in question...could this
actually mean something else? The only thing I could think of
is an Attribute in the Request that matched but had no
AttributeValues in it (this strikes me as a wierd case, but
since it's allowed, this is possible). If this is the case
being described, then this should be explained so it's
clear. If this is not the case, then isn't an empty bag really
an Indterminate case? There isn't much discussion elsewhere
about what exactly AD/AS objects are expected to return, so
maybe more text in section 5 would help clarify this situation.
I'm also a little uneasy about the language because it borders
on defining programming interfaces, but I don't want to propose
alternate language until I understand what's really being
described here. What does this sentence mean?
[Polar] This sentence means exactly what it says. If the the
selector or designator evalutates to an empty bag, then there
is no match, i.e. the match "predicate" is False.
The match predicate is akin to asking, "Do you have one or more
of any subject ids that match "john.*". If you have none, then
False, if you have at least one, then True.
This is a composition of three functions: an Attribute
Designator i.e. "Get me all subject ids", a match filter,
i.e. "that match 'john.*', and a length predicate "length > 0".
Regardless of the match filter, if you have zero elements to
start with, you will end up with zero elements after you apply
the match filter, and therefore, vacuously, you don't have a
match.
[Seth] Yes, I understand that. What I don't understand is how
the bag could be empty and not have that be an Indeterminate
case. This is the only question I was asking.
[Polar] If I ask you whether or not you have any bills in your
wallet that have a picture of Ulysses S. Grant on them. What
will you tell me?
[Anne, responding to Polar] On 17 October, Polar Humenn writes:
> This sentence means exactly what it says. If the the selector or
> designator evalutates to an empty bag, then there is no match, i.e. the
> match "predicate" is False.
>
> The match predicate is akin to asking, "Do you have one or more of any
> subject ids that match "john.*". If you have none, then False, if you have
> at least one, then True.
Are you saying that the result will be "False", rather than
"Indeterminate", when an not-found attribute is compared to a
value?
If so, I think this is wrong. If we can't find an attribute
value in the Request Context, for whatever reason, then the
result should be "Indeterminate", because there MAY be such a
value available somewhere and we simply weren't able to get it.
If your application needs to know for sure that something is
not available (e.g. "Is this person a convicted felon?"), then
the application needs to use a positive attribute like "Is not
a convicted felon", where a trusted authority makes a positive
assertion that such information is missing, rather than
depending on a missing "Is a convicted felon" attribute.
We really need to pin this down. Daniel, I think, says that
only some sort of operational error in talking to the PIP or
repository would result in "Indeterminate". But we can't
guarantee that an error would be detected or that the PDP
wasn't querying the wrong PIP or repository. A classic
security breach is to make something silently unavailable
(unplug a relay, re-route a message, etc.), and use that to
access systems that assume something that is not available is
false.
If an attribute is not present, then the PDP doesn't know what
its value is, and the result should be "Indeterminate" - which
means "the PDP is unable to determine the result".
[Polar] A *Match does not return indeterminate, unless
something is wrong operationally. The predicate is there an
attribute that matches? If there is no attributes of that name,
then the information isn't there.
If you really want an indeterminate, you may wrap the attribute
designator in an apply of "*-one-and-only". This forces an
Indeterminate error if there isn't one attribute. Simiarly, you
can write "*-greater-than" on the "*-length", etc.
I strongly suggest that policy writers should not be relying on
"Indeterminate" for evaluations. It is an error condition, not
a valid access decision.
Writers (or should I say their tools) should be using "present"
in boolean expressions that lead to the desired effect.
[Anne, responding to Polar] On 17 October, Polar Humenn writes:
> This sentence means exactly what it says. If the the selector or
> designator evalutates to an empty bag, then there is no match, i.e. the
> match "predicate" is False.
Isn't this in direct contradiction to your proposed text for
"7.4.2.2 Missing Attributes":
7.4.2.2 Missing Attributes
The PDP SHALL consider an attribute as missing if it
evaluates an expression that requires at least one value to
be present from an attribute designator or selector. In this
case, the expression evaluates to "indeterminate". The PDP
may carry the missing attribute upward in its indeterminate
value in accordance with the XACML evaluation strategy of the
encompassing expressions, rules, policies, and policy
sets. If the PDP evaluates its policy or policy set to
Indeterminate with a missing attribute, the PDP MAY list the
AttributeId and DataType of that attribute in the result as
described in Section 7.5 "Authorization decision". However,
the PDP MAY choose not to issue such information due to
security concerns.
[Polar, responding to Anne] No,
This says if the PDP "evaluates an expression that requires at
least one value to be present"
Such an example would be
<Apply FunctionId="string-one-and-only">
<AttributeDesignator
AttributeId="urn:...:name"
DataType="xs:string"/>
</Apply>
[Anne, responding to Polar] You can't use "present" or
"*-one-and-only" or "*-length" in a <Target>. This means any
policy where you really care about whether an attribute is
present or not will have to use an <Any*> Target, and thus will
always need to be evaluated (can't eliminate by indexing).
I strongly suggest that policy writers should not be relying on
absence of an attribute for evaluations. It is indeterminate,
not a valid access decision. :-)
Note that there are numerous places in the spec that will need
to be re-written or clarified to conform with your
interpretation of attribute retrieval.
I think this is something that has not been clearly understood
by all the TC members, but it is critical to the semantics of
XACML. I can live with Polar's interpretation, although I
think it is wrong and dangerous to security. If we accept his
interpretation, however, we need to be very clear in spelling
out how his interpretation applies to policy evaluation. That
is not currently the case, as witnessed by this entire
disagreement.
[Daniel, responding to Anne]
>We really need to pin this down. Daniel, I think, says that
>only some sort of operational error in talking to the PIP or
>repository would result in "Indeterminate". But we can't
>guarantee that an error would be detected or that the PDP
>wasn't querying the wrong PIP or repository. A classic
>security breach is to make something silently unavailable
>(unplug a relay, re-route a message, etc.), and use that to
>access systems that assume something that is not available is
>false.
Not only an operational error - value out of the permissible
value space for the particular data type, or inability of an
underlying computational procedure to produce a result when the
value is returned by an another function application also
results in Indeterminate.
What you are suggesting is that PDP should have some sort of an
internal knowledge of what information must be available in the
context and signal any discrepancy via Indeterminate result. I
do not think it is a workable operational requirement,
especially given that we do not specify much about the
internals of our virtual context (and I do not think we
should). Such intrusion detection is probably the job of the
PIP service, and yes - it can pass Indeterminate value to the
PDP if, for example, some SHA signature is off etc. But that
is not the job of the PDP, and an empty bag is a critically
useful abstraction to use.
If you want to write your policy in the way, that prohibits
access if something is missing - you can. Polar suggested
several different approaches to this - using present,
*-one-and-only will achieve the same effect.
I do not remember whether we agreed or even discussed my
proposal to treat designator supplied as an argument to a
function requiring a single value attribute as an implicitly
wrapped in *-one-and-only type transformation (but at least
several examples used around do treat it that way). Explicitly
stating such an assumption will probably answer your concern -
it does produce Indeterminate on missing attribute, when
applied to a function requiring a singleton..
[Anne, responding to Daniel] I believe it is your
interpretation that suggests that the PDP has some sort of
internal knowledge about what information must be available in
the context. I am being very clear in saying that the PDP does
NOT have that knowledge, and if it is unable to find an
attribute that is referenced by an AttributeDesignator, for
whatever reason, it will ALWAYS return "Indeterminate" as the
result.
> If you want to write your policy in the way, that prohibits
> access if something is missing - you can. Polar suggested
> several different approaches to this - using present,
> *-one-and-only will achieve the same effect.
a) I can't use those in the Target
b) If I try to use an attribute whose retrieval could fail in a
Target, then the Target will evaluate to NotApplicable.
This will happen even if a temporary network glitch was the
cause for the attribute retrieval failure, and even if the
policy has a "Deny" effect and would have caused me to deny
access had the attribute been available.
> I do not remember whether we agreed or even discussed my
> proposal to treat designator supplied as an argument to a
> function requiring a single value attribute as an implicitly
> wrapped in *-one-and-only type transformation (but at least
> several examples used around do treat it that way).
> Explicitly stating such an assumption will probably answer
> your concern - it does produce Indeterminate on missing
> attribute, when applied to a function requiring a
> singleton..
That would answer only one concern. I agree, however, that if
we accept your interpretation, we must spell this out.
[Polar, responding to Anne] Requiring an attribute to be there
for a match in a target, requires you to evaluate targets
against your request context for your missing attributes, which
precludes doing easy target indexing on the > request in the
first place.
The process of target indexing is actually the other way
around. You have a context with attributes, then you ask "Which
policyies match these attributes?".
You evaluate the request context against the targets. You
evaluate the conditions against the request context.
That functionality can be expressed in the condition with an
appropriate target that doesnn't match on your particular
attribute.
But like I said, you shouldn't be writing policies based on
"Indeterminate". It is a bad error condition.
You should write expressions in the condition that yield the
desired effect for an access decision if such needed
information is missing.
[Daniel] We probably should discuss my suggestion. Implicit
*-one-and-only type transformation when selector/Designator is
used as an argument that must be of singleton type is safe,
clear and answers your concerns about its use in Target. If
you, indeed need one and only one argument (and any function
requiring a sigleton does, by definition) anything else will
yield Indeterminate (which is indeed a bad condition one should
not rely upon for expressing the policy logic - it is there
since errors do happen in our externalized data model and
computation model and we needed a clear and deterministic
mechanism of dealing with them).
[Daniel, responding to Anne] In the same fashion your rule
repository could break or hacked in. There are many of modes
to break down, but the system stability is hardly a concern for
the authorization logic, is it?
Also - empty bag is NOT a failed retrieval. Failed retrieval
MUST result in Indeterminate. Empty bag means that context was
verified intact, working and lacking a particular named
attribute value. If the presense of such attribute was
required by the rule logic - it is a missing attribute,
expressed as Indeterminate value, as in Polar's one-and-only
example..
[Polar] Even so, this appraoch breaks the whole ease of
targeting policies.
This requires that you need to evaluated all your targets for
every request to make sure that you do not have an
interdeterimate comming up from some error condtion of not not
having a particular attribute.
You want to take the information given to you in the request
context and select the applicable policies. Write those
policies as such. If you have special requirements such that an
attribute must be present with some value, that is a
"complicated" evaluation and should go in the condition.
Otherwise, Policy Targeting is just another "hard" evaluation,
and we might as well eliminate it all together.
[Daniel] Not sure what exactly is being broken - the evaluation
performed is exactly the same - the only difference is the
"automatic" type convertion function application for this very
narrow and well defined case.
Matching (member-of "blah" <designator>) and (string-equal
"blah" <implicit string-one-and-only<designator> >) is the same
- you can compile and make sure the type safety is satisfied
just as well. It is only a syntax issue to allow easier use of
designators/selector in target without opening up the syntax to
a full blown <apply> tree.
If you have your context precompiled and verified you index the
target in just the same way - you just write it down in a
little bit diferent manner..
But I do agree that everything complicated sould go into
condition - but we already have our target structure.
[Polar, responding to Daniel]
> Not sure what exactly is being broken - the evaluation
performed is exactly > the same - the only difference is the
"automatic" type convertion function > application for this
very narrow and well defined case.
That's not what I am talking about.
I am talking about taking you match statements and evaluating
the request context against them.
If you have 100,000 policies all of which only 3 apply to a
subject-id of "john".
You can take the information in the request context,
i.e. subject-id of John, and find those three policies by
indexing, of which now, you apply the combining algorithm
against their evaluations.
Now, if you didn't have a request context with a subject-id
attribute?
You might get other policies that apply on some other criteria,
but you would be forced to throw an Indeterminate? How would
you even find those policies to begin with?
If you are allowed to have a single policy with a TARGET that
says "if you don't have an attribute of "subject-id" throw an
Indeterminate". That forces the PDP to evaluate each and every
target, all 100,000 of them for each request, to make sure that
the attributes are there.
Remember, the combining algorithms do funky things with
indeterminates, like make them disappear, in favor of Deny or
Permit, up the evaluation chain. So you would indeed have to
evaluate each and every target of every policy for each
request, all 100,000 of them!
That is not what Targeting is for. It is supposed to aid in
simple indexing and finding of applicable policies. Hal
wouldn't you agree?
Otherwise, we might as well just get rid of target alltogether
and leave everything into a condition.
Targeting allows you to place simple critera for discovering
the applicability of a policy, and nothing else. If an
attribute is needed and it is not there, that logic should
reside in the <Condition>, which MUST be evaluated once the
policy/rule is considered applicable.
[Daniel]
>If you are allowed to have a single policy with a TARGET that
>says "if you don't have an attribute of "subject-id" throw an
>Indeterminate". That forces the PDP to evaluate each and every
>target, all 100,000 of them for each request, to make sure
>that the attributes are there.
Absolutely not. The time to look up "John" in a hash map is
the same whether "John" is present or not. It is O(1) for any
case when it can be reduced to an equality operation and
indexed in advance - is not it?
[Polar] I think you mean, the time to look up subject-id "John"
in the hash map is the same as looking up whether the
subject-id is present or not.
It's one thing to *have* a subject id with "John" and look up
applicable policies. Its an entirely different thing to NOT
have a bunch of ???? attributes and find out if there are any
policies that want it.
Let's say you have a FirstApplicable combining Algorithm on the
the policy set. The first Target wants a "subject-id" match to
"John". The second wants a "weight" attribute of "100lbs". If
you have a request with a "subject-id" of "John" and no
"weight" attribute. What happens? What happens if you have a
"weight" attribute of "100lbs", but no "subject-id" attribute?
What happens.
I know it's a seemingly simple case, but now expand that with
many policies, many targets, and also consider the recursive
nature of the policy set composition.
You end up having to encode the logic of the combining
algorithms into your missing attribute discovery. Also, think
of the Subject section which has complex logic for dealing with
different subjects. That evaluation is of greater complexity
of just looking up policies against attributes you already
have.
The Target should determine the applicability of the policy or
rule, and nothing else. The complex logic goes in the
condition. Indeterminate is an error condition, it should not
be relied upon for policy decisions. That is an abuse of the
intent. Use the right logic, and determine the proper effect.
[Daniel, responding to Polar] Let me clarify a bit. The way I
see the indexing working: Policy is analysed and, for example,
rules requiring attribute "foo" to match are present. Rules
are indexed by the value of "foo" required to match. Rules are
indexed by each attribute required to match - so, yes it is
expensive to have rules requiring many different attributes -
but there is no way around this anyway.
If a request, with an attribute "foo" comes in - rules are
looked up - constant time per each attribute. It is known in
advance that rules requiring "foo" are needed, so if it is not
present, automatically, the whole table of rules indexed by
"foo" are getting Indeterminate result in match - in constant
time, that's what happens. What to do with all this rules -
that's a different thing, but as long as we MAY have missing
attributes in match (they are (non)received with a request),
this can happen and it does scale well.
So it does scale as long as it is an match that can be hashed.
==================================================================
0143: [Seth Proctor] 6.15 status detail formats. Forwarded message from SethProctor.
e-mail sent 17 Oct 2002 16:56:44 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00217.html
ACTION ITEM: [Seth Proctor] Write up details for Tentative Resolution.
STATUS: See TENTATIVE RESOLUTION (NQ 10/28).
TENTATIVE RESOLUTION: Accept proposed text for all status codes
except for "missing-attribute". That one needs:
o syntax for a sequence of <xacml-context:Attribute>
o way to specify whether each missing attribute is for Subject, Resource, Action, or
Environment, and
o if missing attribute is for a subject, and if there are
multiple Subjects, a way to specify for which subject the
attribute is missing.
[Anne: perhaps the format is just <xacml-context:Request>...]
TEXT LOCATION: Following last sentence of Section "6.15 Element
<StatusDetail>", p. 68, line 2820.
TEXT CHANGE: Append following:
Inclusion of a <StatusDetail> element is always optional.
However, if a PDP returns one of the following XACML-defined
<StatusCode> values AND returns a <StatusDetail> element,
then the format of the <StatusDetail> element MUST be as
follows:
urn:oasis:names:tc:xacml:1.0:status:ok
The PDP MUST return no <StatusDetail> element in conjunction
with this status value.
urn:oasis:names:tc:xacml:1.0:status:missing-attribute
ISSUE: Needs to specify subject/resource/action/env
attribute, and, if multiple subjects, for which one.
sequence of <Attribute>
A PDP MAY choose not to return any <StatusDetail>
information or MAY choose to return a <StatusDetail>
message containing one or more <xacml-context:Attribute>
elements.
If AttributeValues are included in an Attribute, then the
PDP is specifying one or more acceptable values for that
Attribute. If no AttributeValues are included, then PDP is
simply naming attributes that it failed to resolve during
its evaluation.
The list of Attributes may be partial or complete. There
is no guarantee by the PDP that supplying the missing
values or attributes will be sufficient to satisfy the
policy.
urn:oasis:names:tc:xacml:1.0:status:syntax-error
A PDP MUST return no <StatusDetail> element in conjunction
with this status value.
A syntax error is either a problem with the policy being
used or with the Request document submitted. The PDP MAY
return a <StatusMessage> describing the problem.
urn:oasis:names:tc:xacml:1.0:status:processing-error
A PDP MUST return no <StatusDetail> element in conjunction
with this status value.
This status code indicates an internal problem in the PDP.
For security reasons, the PDP MAY choose to return no
further information to the PEP. In the case of a
divide-by-zero error or other computational error, the PDP
MAY return a <StatusMessage> describing the nature of the
error.
DISCUSSION:
When status data is returned from the PDP, it may be as
result of any number of things, four of which are defined in
the specification. For these standard cases, the PEP (or some
other entity) will need to be able to handle any extra data
that is returned in the status. But the format of status data
associated with the four standard status codes is not
defined, which is a problem. Here, therefore, is a very
simple proposal for what the formats should like.
There are undoubtedly more complex solutions, but this seems
like the most straightforward approach, and will let
different implementions act in similar ways.
==================================================================
0144: [Polar] harmful to interoperability
e-mail sent 21 Oct 2002 08:50:03 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00239.html
STATUS: APPROVED (NQ 10/28). Reword as suggested. Don't talk about harmful anything.
In section 2.3 "Combining Algorithms", the last paragraph says,
"Users of the standard may, if necessary, defined their own
combining algorithms. However this approach is harmful to
interoperability..."
How is this harmful to interoperability?
Don't you mean "portability" of policies from one XACML
evaluation engine, e.g. a PDP, to another?
Also, saying that "users should specify how the combined result
is to be derived from separate evaluation of the individual
<Rule> or <Policy> statements", is not needed. It's like
telling somebody that they *should* document their
code. Although it is a notably good practice and should be
encouraged, it is kind of insulting to XACML spec readers that
would or already do so.
I would be in favor of a statement that is more focused on the
standard and not its "user" in this regard. I think what we are
after here, is just a statement that rule and policy combining
algorithms are an XACML extensibility point.
I request to change the entire paragraph to:
As one of the XACML extensibility points, XACML may be extended
with alternate rule and policy combining algorithms.
==================================================================
0145: [Seth Proctor] Multi-valued attributes in Request.
e-mail sent 22 Oct 2002 07:48:21 -0400
http://lists.oasis-open.org/archives/xacml/200210/msg00243.html
STATUS: APPROVED (NQ 10/28) Change to maxOccurs=1.
I'm looking for a clarification on the use of multiple
AttribueValue entries in an Attribute type in the Request. If I
have an Attribute with multiple AttributeValue entries, am I
supposed to treat each of these as being (effectively) separate
Attributes with the same values for their meta-data? This
seems like the logical approach, but nothing in the spec
defines the right behavior. Following from this, is it an error
if the Subject Category (for instance) Attribute has multiple
AttributeValue entries, since the spec says that there must be
one and only one value for this attribute?
[Polar] We have multiple <AttributeValue> in attributes? You
mean in the Request Context?
That really shouldn't be.
Being that the request context is a "notational" structure,
there really insn't any need for "economy", such as it is with
XML, on these things. Also, since the <Attribute> has the
DataType attribute, and has the <AttributeValue> element which
must conform to the DataType, I really see no reason to have
such things. Why complicate matters?
The request context is "notational" and using the language of
XML schema should just say that each attribute shall have an
attribute id, a datatype, and a value for that datatype, and
may have and issuer and issue instant.
I suggest we clear this up by changing the schema to make the
attribute value occurance to minOccurs=1 maxOccurs=1.
[Bill] i agree.
[Konstantin] I agree too. Multi-value attributes make the
semantics of attribute comparison more difficult.
==================================================================
0146: [Polar] CR 144: function "present" needs to be fixed.
e-mail sent 22 Oct 2002 12:25:52 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00247.html
STATUS: APPROVED (NQ 10/28). See RESOLUTION.
RESOLUTION: Make new XML elements in schema. Remove them from
Appendix A, put them in text description. New proposal removes
all the -must-be-present functions, since new XML attribute on
attribute designator can do that.
ResourceAttributeDesignator now extends AttributeDesignator.
Resource-attribute-is-present attribute contains same
information, but it returns
The function "present" as we discussed yesterday in spec 18d is
vague in whether it returns "false" or raises an
"indeterminate" if the attribute is not present.
This needs to be cleared up, and we might address some of
Simon's concerns of which he alluded to yesterday on
"indeterminate" for an attribute that is not present. I don't
like that, but I'm not against it.
I've got another proposal to handle the cases where we need to
have predicates for the presence of attribute values, for
action, resources, and subjects.
The basic upshot is the following:
The following correspond to their *AttributeDesignator counterparts:
o action-attribute-is-present
o resource-attribute-is-present
o subject-attribute-is-present
o subject-attribute-is-present-where
o environment-attribute-is-present
The following correspond to the AttributeSelector element:
o attribute-is-present
o attribute-must-be-present
So, I now suggest to replace the last bullet & paragraph
(i.e. "present" of Section A.14.5 Logical Functions with the
following:
o action-attribute-is-present
This function SHALL take two arguments. The first argument
SHALL be an attribute value of type "xs:QName" as used in the
"AttributeId" XML attribute of an <ActionAttributeDesignator>
element. The second argument SHALL be an attribute value of
type "xs:QName" containing the identity of the data type as
used in the "DataType" XML attribute of the
<ActionAttributeDesignator> element. This expression SHALL
result in "true" if the named attribute can be located in the
request context. A result of "true" means that an
<ActionAttributeDesignator> element for this named attribute
will return a bag consisting of at least one element. If no
value can be found for the attribute in the request context,
then this expression SHALL result in "false". A result of
"false" means that an <ActionAttributeDesignator> element for
this named attribute will return an empty bag. If it cannot be
determined whether the attribute is present or not present in
the request context, or its value is unavailable, then the
expression SHALL result in "indeterminate".
o resource-attribute-is-present
This function SHALL take two arguments. The first argument
SHALL be an attribute value of type "xs:QName" as used in the
"AttributeId" XML attribute of an <ResourceAttributeDesignator>
element. The second argument SHALL be an attribute value of
type "xs:QName" containing the identity of the data type as
used in the "DataType" XML attribute of the
<ResourceAttributeDesignator> element. This expression SHALL
result in "true" if the named attribute can be located in the
request context. A result of "true" means that an
<ResourceAttributeDesignator> element for this named attribute
will return a bag consisting of at least one element. If no
value can be found for the attribute in the request context,
then this expression SHALL result in "false". A result of
"false" means that an <ResourceAttributeDesignator> element for
this named attribute will return an empty bag. If it cannot be
determined whether the attribute is present or not present in
the request context, or its value is unavailable, then the
expression SHALL result in "indeterminate".
o subject-attribute-is-present
This function SHALL take two arguments. The first argument
SHALL be an attribute value of type "xs:QName" as used in the
"AttributeId" XML attribute of an <SubjectAttributeDesignator>
element. The second argument SHALL be an attribute value of
type "xs:QName" containing the identity of the data type as
used in the "DataType" XML attribute of the
<SubjectAttributeDesignator> element. This expression SHALL
result in "true" if the named attribute can be located in the
request context. A result of "true" means that an
<SubjectAttributeDesignator> element for this named attribute
will return a bag consisting of at least one element. If no
value can be found for the attribute in the request context,
then this expression SHALL result in "false". A result of
"false" means that an <SubjectAttributeDesignator> element for
this named attribute will return an empty bag. If it cannot be
determined whether the attribute is present or not present in
the request context, or its value is unavailable, then the
expression SHALL result in "indeterminate".
o subject-attribute-is-present-where
This function SHALL take three or more arguments. The first
argument SHALL be an attribute value of type "xs:QName" as used
in the "AttributeId" XML attribute of an
<SubjectAttributeDesignatorWhere> element. The second argument
SHALL be an attribute value of type "xs:QName" containing the
identity of the data type as used in the "DataType" XML
attribute of the <SubjectAttributeDesignatorWhere> element. The
third and subsequent arguments SHALL be <SubjectMatch>
elements. This expression SHALL result in "true" if the named
attribute named by "AttributeId" and "DataType" XML attributes
can be located in the particular subject in the request context
of which all the given <SubjectMatch> expressions evaluate to
"true". A result of "true" means that a
<SubjectAttributeDesignatorWhere> element for this named
attribute and identical <SubjectMatch> elements will return a
bag consisting of at least one element. If no value can be
found for the attribute in the request context, then this
expression SHALL result in "false". A result of "false" means
that an <SubjectAttributeDesignatorWhere> element for this
named attribute will return an empty bag. If it cannot be
determined whether the attribute is present or not present in
the request context, its value is unavailable, or any of the
<SubjectMatch> elements evaluate to "indeterminate", then the
expression SHALL result in "indeterminate".
o evironment-attribute-is-present
This function SHALL take two arguments. The first argument
SHALL be an attribute value of type "xs:QName" as used in the
"AttributeId" XML attribute of an
<EnvironmentAttributeDesignator> element. The second argument
SHALL be an attribute value of type "xs:QName" containing the
identity of the data type as used in the "DataType" XML
attribute of the <EnvironmentAttributeDesignator> element. This
expression SHALL result in "true" if the named attribute can be
located in the request context. A result of "true" means that
an <EnvironmentAttributeDesignator> element for this named
attribute will return a bag consisting of at least one
element. If no value can be found for the attribute in the
request context, then this expression SHALL result in
"false". A result of "false" means that an
<EnvironmentAttributeDesignator> element for this named
attribute will return an empty bag. If it cannot be determined
whether the attribute is present or not present in the request
context, or its value is unavailable, then the expression SHALL
result in "indeterminate".
o attribute-is-present
This function SHALL take two arguments. The first argument
SHALL be an argument of type "xs:string" that is an XPath
expression that is used in the "RequestContextPath" XML
attribute of the <AttributeSelector> element. The second
argument SHALL be an attribute value of type "xs:QName"
containing the identity of the data type as used in the
"DataType" XML attribute of the <AttributeSelector>
element. This expression SHALL result in "true" if the value
can be found. A result of "true" means that an
<AttributeSelector> element for this named attribute SHALL
return a bag consisting of at least one element. If no value
can be found, then this expression SHALL result in "false". A
result of "false" means that the corresponding
<AttributeSelector> element SHALL return an empty bag. If it
cannot be determined that a value for this XPath expression is
present or not present, or the value is unavailable, then the
expression SHALL result in "indeterminate".
o attribute-must-be-present
This function SHALL take two arguments. The first argument
SHALL be an argument of type "xs:string" that is an XPATH
expression that is used in the "RequestContextPath" XML
attribute of the <AttributeSelector> element. The second
argument SHALL be an attribute value of type "xs:QName"
containing the identity of the data type as used in the
"DataType" XML attribute of the <AttributeSelector>
element. This expression SHALL result in "true" if the value
can be found. A result of "true" means that an
<AttributeSelector> element for this named attribute SHALL
return a bag consisting of at least one element. If no value
can be found, then this expression SHALL result in "false",
which means that the corresponding <AttributeSelector> element
SHALL return an empty bag, this expression SHALL result in
"indeterminate". If it cannot be determined that a value for
this XPath expression is present or not present, or the value
is unavailable, then the expression SHALL result in
"indeterminate".
[Polar] Okay, I'm in trouble on this "*-is-present" stuff.
In looking in the schema, I found out that I probably messed up
the subject-attribute-*-present functions by not having an
argument that states the value of the subject-category
attribute.
I also have a problem with the
subject-attribute-*-present-where functions. I specify that
they will take <SubjectMatch> elements as arguments in the
<Apply>. However, that does NOT fit the evaluation strategy
very well, as these elements return booleans, and to be
consistent with the generic function application evaluation
model, they should be evaluated independantly as
arguments. Basically, they are evaluated without concern of
being limited to the same subject. We somehow have to bring the
evaluation of the equivalent of subject match into the
function.
So, unfortunately, because of multiple subjects, this approach
complicates matters to no end for the function predicates that
need to figure this out, as for
subject-attribute-is-present-where I would have to specify
something silly like:
For each subject match we would add to the
subject-attribute-is-present-where function, sets of four
arguments, each of which the first is the MatchId, the second
is the attribute name, the third is the data type, and the
fourth is the matching value. (Yuch!)
My conclusion: Since attributes are retrieved by different
schema elements, it seems most logical to make their
"is-present" counterparts schema elements as well, using much
of the same machinery already in place. It would be easy to add
these as element of the AttributeDeignator/Selector/Type
complex types we ALREADY have defined:
So, I think a better approach would be to add the following
elements to the schema with the semantics I proposed in the
previous iterations.
These elements would be element instances of the
<AttributeDesignatorType>:
ActionAttributeIsPresent ActionAttributeMustBePresent
ResourceAttributeIsPresent ResourceAttributeMustBePresent
EnvironmentAttributeIsPresent EnvironmentAttributeMustBePresent
These elements would be element instances of the
<SubjectAttributeDesignatorType>:
SubjectAttributeIsPresent SubjectAttributeMustBePresent
These elements would be element instances of the
<SubjectAttributeDesignatorWhereType>:
These elements can be element instances of the
<AttributeSelectorType>:
AttributeIsPresent AttributeMustBePresent
I can modify the document with Word97 and give these sections
to the list if one would like?
[Simon] I think that <AttributeDesignator> and <AttributeSelector> elements with
mustBePresent attribute will cover all cases:
<xs:complexType name="AttributeDesignatorType">
<xs:attribute name="AttributeId" type="xs:anyURI" use="required"/>
<xs:attribute name="DataType" type="xs:QName" use="required"/>
<xs:attribute name="MustBePresent" type="xs:boolean" use="required"/> <--
new attribute
<xs:attribute name="Issuer" type="xs:anyURI" use="optional"/>
</xs:complexType>
<xs:complexType name="AttributeSelectorType">
<xs:attribute name="RequestContextPath" type="xs:string" use="required"/>
<xs:attribute name="DataType" type="xs:QName" use="required"/>
<xs:attribute name="MustBePresent" type="xs:boolean" use="required"/> <-- new
attribute
</xs:complexType>
[Polar, responding to Simon]
> I think that <AttributeDesignator> and <AttributeSelector>
> elements with mustBePresent attribute will cover all cases:
No, it won't. Thas is because I will not be able to write
predicates about their presence, and only be able to get an
"indeterminate" on requesting one.
And also, again, in the Target, where these things appear, that
attribute's semantics would complicate the idexing and
retriveal of policies and rules etc etc etc.
==================================================================
0147: [Seth Proctor] Bug in pseudocode for Only One Applicable.
e-mail sent 22 Oct 2002 13:56:29 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00249.html
STATUS: APPROVED (NQ 10/28). Polar will reword.
I think there is a bug in the pseudocode for the Only One
Applicable Policy combining algorithm. The spec reads
"If an error occurs while evaluating the target of a policy
... then the policy set SHALL evaluate to 'Indeterminate'."
I think this is correct, but it's not expressed in the
pseudocode. The code calls isApplicable() on the policy to see
if the target matches, but there is no code to check if this
call resulted in an error. Small issue, but I thought I'd
mention it, since all the other combining algs can be
implemented verbatim from the given pseudocode.
==================================================================
0148a: [Yassir Elley] Example two rules not applicable to request
e-mail sent 22 Oct 2002 15:10:25 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00251.html
Example two specifies four separate rules, as well as a
request context "to which the example rules are intended to be
applicable." Unfortunately, none of the example rules are
applicable to the request context that is specified. This
should probably be fixed.
ACTION ITEM: [Simon] Review and revise as needed.
STATUS: (10/28) Waiting on Simon's review and/or revision.
==================================================================
0148b: [Yassir Elley] Include target-namespace in Request Context?
e-mail sent 22 Oct 2002 15:10:25 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00251.html
As part of the Target, each of the rules includes a
<ResourceMatch> of <ResourceAttributeDesignator
AttributeId="urn:...:target-namespace" ...> Since
"target-namespace" is not included as a Resource Attribute in
the request context, none of the rules will ever match. Perhaps
"target-namespace" should be included as a Resource Attribute
in the request context.
ACTION ITEM: [Simon] Review and revise as needed.
STATUS: (10/28) Waiting on Simon's review and/or revision.
==================================================================
0148c: [Yassir Elley] Syntax of RequestContextPath not consistent
e-mail sent 22 Oct 2002 15:10:25 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00251.html
Rules 1, 2, and 3 make use of an AttributeSelector as part of a
Condition. The AttribueSelector has an XML attribute named
RequestContextPath (RCP). The syntax of the RCP is inconsistent
among the rules and should be made consistent. For example:
Rule 1: RCP="//ctx:ResourceContent/md:record/" Rule 2:
RCP="/ctx:Request//ctx:ResourceContent/md:record/" Rule 3:
RCP="/ctx:Request/ctx:Resource/ctx:ResourceContent/md:record/"
ACTION ITEM: [Simon] Review and revise as needed.
STATUS: (10/28) Waiting on Simon's review and/or revision.
==================================================================
0148d: [Yassir Elley] Move "disjunctive sequence" up to higher element description
e-mail sent 22 Oct 2002 15:10:25 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00251.html
In Section 5.6 (line 1951), it is somewhat strange that the
explanatory text for <Subject> reads "A disjunctive sequence of
<Subject> elements." This seems more appropriate for the
<Subjects> element. This same pattern occurs with the
explanatory text for <Resource> (line 2015) and <Action> (line
2078)
ACTION ITEM: [Simon] Review and revise as needed.
STATUS: (10/28) Waiting on Simon's review and/or revision.
==================================================================
0148e: [Yassir Elley] Editorial comments
e-mail sent 22 Oct 2002 15:10:25 -0400 (EDT)
http://lists.oasis-open.org/archives/xacml/200210/msg00251.html
STATUS: Editorial. No vote required.
1041: insert "//" (i.e. "http://www.medico.com";;)
1049: insert "//" (i.e. "http://www.medico.com";;)
1069: replace "[14]-[72]" with "[15]-[22]"
1085: Rule 1 states "A person may read any record for which he or
she is the designated patient." In Example 4.2.4.1, however,
the policy-number in the medical record is compared with
the policy-number attribute of the subject. This is slightly
confusing.
1107: replace "scheams" with "schemas"
1131: replace "xpath-match" with "xpath-node-match"
1184: replace "authorization decision request such, that the value" with
"authorization decision request, such that the value"
1201: insert "the" before "explicit value"
1296: replace "xpath-match" with "xpath-node-match"
1346: "md:parentGuardianId" doesn't exist in example medical record.
It should be added.
1541: "md:physicianId" doesn't exist in example medical record. There is
however a "registrationId". These should be made consistent.
1600: replace "exampes:attributes:group" with "example:attribute:role"
1604: replace "read" with "write"
1675: replace "xpath-match" with "xpath-node-match"
1726: replace ""read"" with ""read" or "write""
1933: remove duplicate "for the"
2225: insert ",action," after "resource"
2280: <SubjectAttributeDesignator> is missing
2333: replace "Shall" with "SHALL"
2384: replace "contains following attributes" with "contains the
following attribute"
2434: insert "in" after "resulting"
2599: replace "Distingwished" with "Distinguished"
2704: replace "dn" with "DN"
3286: resource:resource-id is marked as Optional. Earlier, the spec
specifies that "the <Resource> element MUST contain one
and only one <Attribute> with AttributeId "urn:...:resource-id".
This should probably be marked Mandatory, not Optional.
3920: replace "second" with "third"
4696: replace "CombinginAlogrithm" with "CombiningAlgorithm"
==================================================================
0149: [Seth Proctor] Environment attributes
e-mail sent 23 Oct 2002 12:22:39 -0400
http://lists.oasis-open.org/archives/xacml/200210/msg00253.html
STATUS: CLOSED (NQ 10/28). See RESOLUTION.
RESOLUTION: If in original RequestContext from PEP, then use
that. If has to be retrieved (i.e. "notional"), it is up to
the implementation. The semantics are "Time that applies to
the Request". It is up to the PEP to ask the right question.
ORIGINAL CHANGE REQUEST:
In section 10.3.5 of 18d, the spec calls out three attribute
identifiers that the PDP must be able to handle specially
(these are current-time, current-date, and
current-dateTime). Is the idea that these would appear in an AD
in a policy, and the PDP is supposed to know to resolve these
values itself rather than looking in the Request? I think
that's the idea, but it's not spelled out explicitly in the
text.
[Polar] I should believe that values for the current-time,
current-date, and current-dateTime environmental attributes
should be provided by the PEP, not the PDP.
How can one force temporal evaluation schemes on the PDP for it
to come up with values for these attributes? One has no control
over the evaluation, especially if different pieces of the
policy get evaluated at different times. It is completely up to
an implementation.
The client of the PDP, (i.e. a PEP) should be providing values
for these attributes in the request context. The PDP should NOT
supply them. Otherwise, you would get different answers for
the same inputs given by the client (i.e. a PEP).
In fairness to temporal reasoning, however, it is the onerous
of the client, i.e. PEP, in accordance with XACML semantics, to
give these attributes values that are considered valid with the
temporal concerns of an access decision.
Basic upshot: The current-time, current-date, and
current-dateTime should be required to come from the request
context.
[Anne] Except that I believe we say explicitly that
"current-time", etc. is the time at the PDP. How is the PEP
supposed to know the time at the PDP? Maybe we need
current-PDP-time, etc. and current-PEP-time, etc. :-)
[Polar] The PEP is not supposed to know the time at the
PDP. The PEP should fill those values with the time relavant to
the access decision. The XACML writer expects those values to
correspond with the time for which the access decision applies.
[Daniel] Disagree. For time based policy having the time passed
in is not always safe.
If it is needed - it is easy to do, just add an attribute, but
if you are going to have a build in time it has to be server
side for auditing and safety.
[Bill, responding to Polar] i agree. we should explicitly state
this in the context description, spelling out that PEP passes
*local* datetime information as azn request attributes.
[Bill, responding to Daniel]...which means that policies
writers will have to manually compensate for time (and date)
variations. assuming that you have a PDP in the central
timezone and a PEP on either coast, this presents something of
a challenge. that alone negates any potential 'security'
enhancement that may be provided through increased opportunity
for author error.
as to auditing, if all PDP transactions are timestamped by the
PDP as part ot the logging process i don't see this an an
impediment to centralized audits. any event can be mapped back
to the point of request at the time of audit--a safer model in
my mind.
[Daniel] Attempt to elaborate: if we are to have a build-in
standard time attribute it should be on PDP, otherwise it is
hard to use it in a policy (if having a policy based on the
time of decision is what you want). If you do not want to have
a policy based on the time of decision, then we should probably
let the implementation to decide when, where and how the
relevant time is computed and placed into the context. If we
see too many problems with "build-in" clock, I would agree to
drop it altogether, although I think that some reference
decision time clock is a useful feature (not only for decision,
but also for such sanity checks, like not granting access three
years in the future, or in the last century..)..
[Daniel, responding to Bill]
>...which means that policies writers will have to manually
>compensate for time (and date) variations. assuming that you
>have a PDP in the central timezone and a PEP on either coast,
>this presents something of a challenge. that alone negates
>any potential 'security' enhancement that may be provided
>through increased opportunity for author error.
Sure. There is no free lunch - if you want a "live" clock
ticking somewhere, you got to be careful (and may want to use
GMT time or something...)
>as to auditing, if all PDP transactions are timestamped by the
>PDP as part of the logging process i don't see this an an
>impediment to centralized audits. any event can be mapped back
>to the point of request at the time of audit--a safer model in
>my mind.
Unless you do want a policy tied to a live clock (and many
applications do) and you want to connect the decision with the
time stamp - so the auditing and ecision uses the exact same
clock.
I agree that it does open the can of worms - but occasionally
you need'em to go fishing..
I would also agree to not include "live" clock anywhere at all.
It can be done in an implementation if needed..
[Bill] i don't understand what you mean by a 'live clock'. can
you explain, or give an example of a policy that needs a 'live
clock'?
[Mike Burati]
>>which means that policies writers will have to manually
>>compensate for time (and date) variations. assuming >that you
>>have a PDP in the central timezone and a PEP on either coast,
>>this presents something of a challenge.
>
> Sure. There is no free lunch - if you want a "live" clock
> ticking somewhere, you got to be careful (and may want to use
> GMT time or something...)
Whether or not you have a PDP in a different timezone than PEP,
you have to deal with dateTime values that may differ in
Timezone (consider the scenario where a multinational or even
just US-wide enterprise has policy admins/writers in multiple
timezones even if they centralize their PDP in their IT
headquarter's TZ and keep PEPs local to the systems they're
protecting...). So, you likely already have to deal with
converting/normalizing to a single timezone (eg, GMT) to do
comparisons, even for a PDP/PEP within a single timezone, no?
>as to auditing, if all PDP transactions are timestamped by the
>PDP as part of the logging process i don't see this an an
>impediment to centralized audits. any event can be mapped back
>to the point of request at the time of audit--a safer model in
>my mind.
I agree - audit records created by a PDP should be timestamped
using the PDP's clock, likewise for any audit records the PEP
creates - use its clock.
> I agree that it does open the can of worms - but occasionally
> you need'em to go fishing..
>
> I would also agree to not include "live" clock anywhere at
> all. It can be done in an implementation if needed..
Which is a good reason to allow, but not require use of the
timestamps, right? (other than for audit logs where I presume
it would be required anyway).
Speaking of a can of worms - for those who want to make
ultimate use of timestamps in their authorization decisions:
One option "if" the decision is made to stick with the PDP's
clock for comparing against a policy timestamp, would be to
allow use of a Kerberos-like PEP to PDP time-synchronization
check where the PEP specifies that the PDP should evaluate the
policy IFF the PDP's current-time is within a given
(configurable) window of the PEP-current-time (normalized to
GMT) included in the context (pardon the terminology - as I
said, I'm a bit behind the curve on this one). Sure, it leads
to lots of runtime errors if you don't synchronize your clocks
(as I've seen lots of with Kerberos and DCE in the past even in
small enterprises), but it does give you the "option" of having
both the PEP's clock and PDP's clock contribute to the
evaluation for those that can't agree which is the correct
choice.
[Daniel, responding to Bill]
>i don't understand what you mean by a 'live clock'. can you
>explain, or give an example of a policy that needs a 'live
>clock'?
Dumb example: if you control access to the building, that have
a thousand doors, you do not want each lock to send in its own
time in a request. Nor you need permission to open the door in
the future on in the past. One need to enter right now, and
that "now" must be determined during the evaluation.. Only then
policy writer can guarantee that nobody gets in in the wrong
time.. "Live" clock is something that is guaranteed to be the
same in any evaluation context, independent of the request..
[Polar, responding to Daniel]
> Disagree. For time based policy having the time passed in is
> not always safe.
Well, for time based (or time critical?) policy as you suggest,
you would make sure that your PEP to PDP configuration was as
"real-time" as you could make it. That would mean that the PEP
would supply the time of the access decision, and your
evaluation strategy of the PDP would process within your
realtime constraints.
> If it is needed - it is easy to do, just add an attribute,
> but if you are going to have a build in time it has to be
> server side for auditing and safety.
For auditing and safety, your PDP could check to see if the
time supplied in the request is within acceptable constraints
before and/or after the decision is processed. This approach is
common in authentication mechanisms, such as Kerberos.
You also may want to ask about access decisions that are not of
the actual current time, but at some time in the future. For
example, as a pure client of a PDP, you may want to know if A
has access to R five minutes from now, such that the decision
governs how a request gets processed. To make sense of that,
the policy must be written as if it were processing the given
time as the current time.
Alternatively, to address your time based policy approach, the
PEP may not supply the time, but the "request context builder"
would. Being that the request context is this a "notion" more
than it is a concrete request structure, we can just state that
the current time is supplied in the request context. However,
whenever the PDP it asks for the current-time attribute, it
gets it from the request context, and the request context
builder can assign that attribute the current time at that
moment, just as if were a "weight" attribute pulled from
Daniel's database. However, I would suggest, once it is
assigned it doesn't change during the evaluation!
So, in implemenation the values given to the current time
attributes can be as static and dynamic as you want it to
be. And in the standard, having it come from the request
context addresses both concerns, without much problem.
Having the PDP generate current-time on the fly isn't much good
if policies take a long time to evaluate and you cannot
guarrantee when they are evaluated, and doesn't address being
able to ask access decisions about the future or even the past.
"Was John allowed in the building at 6pm yesterday?"
Also, for analysis and testing to make sure that the policy is
doing what you think it ought to do:
Can "Employees get in the building at 7pm tonight"?
[Anne, responding to Daniel] I think most "auditing" will be
done by the PEP. The PEP is the entity that must enforce the
access decision, and the PDP must trust the PEP to supply
correct attributes and to do the enforcement. The PDP is just
an "evaluation engine": given request and policy, provide
decision.
[Daniel, responding to Anne]..given request and policy and
CONTEXT, which very well may include global parameters
independent of an individual request..
Also, auditing is best done where the decision is made, not
were it is used, as auditing may include information not
returned to PEP (such as a reason for DENY)..
[Polar, responding to Daniel]
> ..given request and policy and CONTEXT, which very well may
> include global parameters independent of an individual
> request..
>
> Also, auditing is best done where the decision is made, not
> were it is used, as auditing may include information not
> returned to PEP (such as a reason for DENY)..
Well, "best" is only an opinion which depends upon the
application, and the auditing that is required for that
application. The decision, itself could have been made weeks
ago. Actually when you write the policy, you've have *already*
made the decision.
==================================================================
0150: [Seth Proctor] Types of pre-defined attributes
e-mail sent 23 Oct 2002 12:22:39 -0400
http://lists.oasis-open.org/archives/xacml/200210/msg00253.html
STATUS: CLOSED. SUPERSEDED BY 0134c. (Q 10/24).
...these go on that list I started earlier of attributes that
should be defined to always be of a particular type:
subject-category string or URI
resource-id string or URI
scope string
current-time ???
current-date date
current-dateTime dateTime
Since each of these identifiers must be special-cased by the
PDP, they must always be of a known type. There may be others
that should be on this list, but most of the other identifiers
are not treated in any special way by the PDP, so the type
information is transparent to the PDP.
==================================================================
0151: [Seth Proctor] editorial: 10.3.6 extraneous paragraph
e-mail sent 23 Oct 2002 14:38:32 -0400
http://lists.oasis-open.org/archives/xacml/200210/msg00254.html
STATUS: Editorial. No vote required.
In section 10.3.6, the 2nd paragraph isn't needed, since it's
the same as the first two sentences of the 1st paragraph.
==================================================================
0152: [Tim Moses] Trivial Matter
e-mail sent 28 Oct 2002 09:31:24 -0500
http://lists.oasis-open.org/archives/xacml/200210/msg00285.html
STATUS: Not yet considered.
We should call the <SubjectAttributeDesignatorWhere> element
<SubjectQualifier>. If you need further convincing, read on.
I recognize at least two styles for naming elements,
attributes, etc.: the "descriptive" style and the "literate"
style. In the "descriptive" style, the name is chosen in an
attempt to reflect the semantics of the element. In the
"literate" style, the name is chosen in an attempt to make the
"source" "read". I contend that we have almost exclusively
chosen the descriptive style. Consider the XML attribute
"FunctionId". If we had been following the literate style, we
would have chosen the name "Function". Then the Apply element
would read ...
<Apply Function ...
instead of ...
<Apply FunctionId ...
I think either style would be acceptable (although both Polar
and I have declared that we never want to read an XACML policy
in its native form). But, I would like us to be consistent in
our application of a single style.
Therefore, I propose that we use the descriptive style of
naming and that we choose <SubjectQualifier> instead of
<SubjectAttributeDesignatorWhere>. It has the additional
benefit of being half the size.
I also considered <SubjectSelector>, but thought that was too
similar to <SubjecAttributeSelector>.
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