Network Working Group M. Petit-Huguenin
Internet-Draft Stonyfish, Inc.
Intended status: Standards Track May 13, 2011
Expires: November 14, 2011
Configuration of Access Control Policy in REsource LOcation And
Discovery (RELOAD) Base Protocol
draft-petithuguenin-p2psip-access-control-02
Abstract
This document describes an extension to the REsource LOcation And
Discovery (RELOAD) base protocol to distribute the code of new Access
Control Policies without having to upgrade the RELOAD implementations
in an overlay.
Status of this Memo
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include Simplified BSD License text as described in Section 4.e of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Processing an extended Kind . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . . 6
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 6
A.1. Standard Access Control Policies . . . . . . . . . . . . . 6
A.1.1. USER-MATCH . . . . . . . . . . . . . . . . . . . . . . 6
A.1.2. NODE-MATCH . . . . . . . . . . . . . . . . . . . . . . 7
A.1.3. USER-NODE-MATCH . . . . . . . . . . . . . . . . . . . 7
A.1.4. NODE-MULTIPLE . . . . . . . . . . . . . . . . . . . . 7
A.2. Service Discovery Usage . . . . . . . . . . . . . . . . . 8
Appendix B. Release notes . . . . . . . . . . . . . . . . . . . . 10
B.1. Modifications between -02 and -01 . . . . . . . . . . . . 10
B.2. Modifications between -01 and -00 . . . . . . . . . . . . 10
B.3. Running Code Considerations . . . . . . . . . . . . . . . 10
B.4. TODO List . . . . . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
The RELOAD base protocol specifies an Access Control Policy as
"defin[ing] whether a request from a given node to operate on a given
value should succeed or fail." The paragraph continues saying that
"[i]t is anticipated that only a small number of generic access
control policies are required", but there is indications that this
assumption will not hold. On all the RELOAD Usages defined in other
documents than the RELOAD base protocol, roughly 50% defines a new
Access Control Policy.
The problem with a new Access Control Policy is that, because it is
executed when a Store request is processed, it needs to be
implemented by all the peers and so requires an upgrade of the
software. This is something that is probably not possible in large
overlays or on overlays using different implementations. For this
reason, this document proposes an extension to the RELOAD
configuration document that permits to transport the code of a new
Access Control Policy to each peer.
This extension defines a new element <access-control-code> that can
be optionally added to a <kind> element in the configuration
document. The <access-control-code> element contains ECMAScript
[ECMA-262] code that will be called for each StoredData object in a
StoreReq processed by a peer. The code receives four parameters,
corresponding to the Resource-ID, Signature, Kind and StoredDataValue
of the value to store. The code returns true or false to signal to
the implementation if the request should succeed or fail.
For example the USER-MATCH Access Control Policy defined in the base
protocol could be redefined by inserting the following code in an
<access-control-code> element:
return resource.equalsHash(signature.user_name.bytes());
The <kind> parameters are also passed to the code, so the NODE-
MULTIPLE Access Control Policy could be implemented like this:
for (var i = 0; i < kind.max_node_multiple; i++) {
if (resource.equalsHash(signature.node_id, i.width(4))) {
return true;
}
}
return false;
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Processing an extended Kind
A peer receiving a <kind> definition containing an access-control-
code elemtn , either by retrieving it from the configuration server
or in a ConfigUpdateReq message, MUST reject this configuration if
the kind element is not signed or if the signature verification
fails.
If the <access-control-code> element is present in the namespace
allocated to this specification, and the Access Control Policy is not
natively implemented, then the code inside the element MUST be called
for each DataValue found in a received StoreReq for this Kind. For
each call to the code, the following ECMAScript objects, properties
and functions MUST be available:
resource: An opaque object representing the Resource-ID, as an array
of bytes.
resource.equalsHash(Object...): A function that returns true if
hashing the concatenation of the arguments according to the
mapping function of the overlay algorithm is equal to the
Resource-ID. Each argument is an array of bytes.
signature.user_name: The rfc822Name stored in the certificate that
was used to sign the request, as a String object.
signature.node_id: The Node-ID stored in the certificate that was
used to sign the request, as an array of bytes.
kind.id: The id of the Kind associated with the entry, as a Number
object.
kind.name: If the Kind associated with the entry is registered by
IANA, contains the name as a String object. If not, this property
is undefined.
kind.data_model: The name of the Data Model associated with the
entry, as a String object.
kind.access_control: The name of the Access Control Policy
associated with the entry, as a String object.
kind.max_count: The value of the max-count element in the
configuration file, as a Number object.
kind.max_size: The value of the max-size element in the
configuration file as a Number object.
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kind.max_node_multiple: If the Access Control is MULTIPLE-NODE,
contains the value of the max-node-multiple element in the
configuration file, as a Number object. If not, this property is
undefined.
entry.index: If the Data Model is ARRAY, contains the index of the
entry, as a Number object. If not, this property is undefined.
entry.key: If the Data Model is DICTIONARY, contains the key of the
entry, as an array of bytes. If not, this property is undefined.
entry.storage_time: The date and time used to store the entry, as a
Date object.
entry.lifetime: The validity for the entry in seconds, as a Number
object.
entry.exists: Indicates if the entry value exists, as Boolean
object.
entry.value: This property contains an opaque object that represents
the whole data, as an array of bytes.
The properties SHOULD NOT be modifiable or deletable and if they are,
modifying or deleting them MUST NOT modify or delete the equivalent
internal values (in other words, the code cannot be used to modify
the elements that will be stored).
The value returned by the code is evaluated to true or false,
according to the ECMAScript rules. If the return value of one of the
call to the code is evaluated to false, then the StoreReq fails, the
state MUST be rolled back and an Error_Forbidden MUST be returned.
4. Security Considerations
TBD
5. IANA Considerations
No IANA considerations.
6. Acknowledgements
This document was written with the xml2rfc tool described in
[RFC2629].
7. References
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7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[I-D.ietf-p2psip-base]
Jennings, C., Lowekamp, B., Rescorla, E., Baset, S., and
H. Schulzrinne, "REsource LOcation And Discovery (RELOAD)
Base Protocol", draft-ietf-p2psip-base-13 (work in
progress), March 2011.
[ECMA-262]
Ecma, "ECMAScript Language Specification 3rd Edition",
December 2009.
7.2. Informative References
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[I-D.ietf-p2psip-service-discovery]
Maenpaa, J. and G. Camarillo, "Service Discovery Usage for
REsource LOcation And Discovery (RELOAD)",
draft-ietf-p2psip-service-discovery-02 (work in progress),
January 2011.
[I-D.knauf-p2psip-share]
Knauf, A., Hege, G., Schmidt, T., and M. Waehlisch, "A
Usage for Shared Resources in RELOAD (ShaRe)",
draft-knauf-p2psip-share-00 (work in progress),
March 2011.
Appendix A. Examples
A.1. Standard Access Control Policies
This section shows the ECMAScript code that could be used to
implement the standard Access Control Policies defined in
[I-D.ietf-p2psip-base].
A.1.1. USER-MATCH
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String.prototype['bytes'] = function() {
var bytes = [];
for (var i = 0; i < this.length; i++) {
bytes[i] = this.charCodeAt(i);
}
return bytes;
};
return resource.equalsHash(signature.user_name.bytes());
A.1.2. NODE-MATCH
return resource.equalsHash(signature.node_id);
A.1.3. USER-NODE-MATCH
String.prototype['bytes'] = function() {
var bytes = [];
for (var i = 0; i < this.length; i++) {
bytes[i] = this.charCodeAt(i);
}
return bytes;
};
var equals = function(a, b) {
if (a.length !== b.length) return false;
for (var i = 0; i < a.length; i++) {
if (a[i] !== b[i]) return false;
}
return true;
};
return resource.equalsHash(signature.user_name.bytes())
&& equals(entry.key, signature.node_id);
A.1.4. NODE-MULTIPLE
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Number.prototype['width'] = function(w) {
var bytes = [];
for (var i = 0; i < w; i++) {
bytes[i] = (this >>> ((w - i - 1) * 8)) & 255;
}
return bytes;
};
for (var i = 0; i < kind.max_node_multiple; i++) {
if (resource.equalsHash(signature.node_id, i.width(4))) {
return true;
}
}
return false;
[[Note that base-13 do not state exactly the length of i when
concatenated in the hash input]]
A.2. Service Discovery Usage
[I-D.ietf-p2psip-service-discovery] defines a specific Access Control
Policy (NODE-ID-MATCH) that need to access the content of the entry
to be written. If implemented as specified by this document, the
<kind> element would look something like this:
<kind name='REDIR'
xmlns:acp='http://implementers.org/access-control-policy'
xmlns:ext='http://implementers.org/my-ext'>
<data-model>DICTIONARY</data-model>
<access-control>NODE-ID-MATCH</access-control>
<max-count>100</max-count>
<max-size>60</max-size>
<acp:access-control-code>
/* Insert here the code from
http://jsfromhell.com/classes/bignumber
*/
var toBigNumber = function(node_id) {
var bignum = new BigNumber(0);
for (var i = 0; i < node_id.length; i++) {
bignum = bignum.multiply(256).add(node_id[i]);
}
return bignum;
};
var checkIntervals = function(node_id, level, node, factor) {
var size = new BigNumber(2).pow(128);
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var node = toBigNumber(node_id);
for (var f = 0; f < factor; f++) {
var temp = size.multiply(new BigNumber(f)
.pow(new BigNumber(level).negate()));
var min = temp.multiply(node.add(new BigNumber(f)
.divide(factor)));
var max = temp.multiply(node.add(new BigNumber(f + 1)
.divide(factor)));
if (node.compare(min) === -1 || node.compare(max) == 1
|| node.compare(max) == 0) return false;
}
return true;
};
var equals = function(a, b) {
if (a.length !== b.length) return false;
for (var i = 0; i < a.length; i++) {
if (a[i] !== b[i]) return false;
}
return true;
};
var level = function(value) {
var length = value[16] * 256 + value[17];
return value[18 + length] * 256 + value[18 + length + 1];
};
var node = function(value) {
var length = value[16] * 256 + value[17];
return value[18 + length + 2] * 256
+ value[18 + length + 3];
};
var namespace = function(value) {
var length = value[16] * 256 + value[17];
return String.fromCharCode(value.slice(18, length));
};
var branching_factor = 2;
return equals(entry.key, signature.node_id)
&& (!entry.exists || checkIntervals(entry.key,
level(entry.value), node(entry.value),
branching_factor))
&& (!entry.exists
|| resource.equalsHash(namespace(entry.value),
level(entry.value), node(entry.value)));
</acp:access-control-code>
</kind>
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Note that the code for the BigNumber object was removed from this
example, as the licensing terms are unclear. The code is available
at <http://jsfromhell.com/classes/bignumber>.
The branching-factor variable in the code must match the
<redirBranchingFactor> element, which is not accessible to the code.
The signer of the kind must be sure that the two match.
Appendix B. Release notes
This section must be removed before publication as an RFC.
B.1. Modifications between -02 and -01
o Made clear that an unsigned kind with this extension must be
rejected.
o Removed the kind.params array, and converted the max-count, max-
size and max-node-multiple as Number objects. Fixed the examples.
o Removed the parsing of extensions in the kind element. The former
system did not work with namespaces or attributes, and the right
solution (xpath) is probably too complex. The value of the
parameters can still be manually mirrored in the script, so there
is perhaps no need for the added complexity. Also fixed the
examples.
o Reference draft-p2psip-share instance of draft-p2psip-disco.
o Added a "Running Code Considerations" section that contain the
reference to the reference implementation and script tester.
o Nits
B.2. Modifications between -01 and -00
o Changed reference from JavaScript to ECMAScript.
o Changed signature from equals() to equalsHash().
o Fixed the examples following implementation.
o Replaced automatic decoding of value by ECMAScript code.
o Added the type of each property.
o Specified that the code cannot be used to modify the value stored.
B.3. Running Code Considerations
o Reference Implementation and Access Control Policy script tester
(<http://debian.implementers.org/testing/source/reload.tar.gz>).
Marc Petit-Huguenin. Implements version -02.
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B.4. TODO List
o Need to convert ShaRe [I-D.knauf-p2psip-share] Usages USER-CHAIN-
ACL and USER-PATTERN-MATCH.
Author's Address
Marc Petit-Huguenin
Stonyfish, Inc.
Email: petithug@acm.org
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