Network Working Group M. Rose

Network Working Group M. Rose
Request for Comments: 3341 Dover Beach Consulting, Inc.
Category: Standards Track G. Klyne
Clearswift Corporation
D. Crocker
Brandenburg InternetWorking
July 2002

The Application Exchange (APEX) Access Service

Status of this Memo

This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2002). All Rights Reserved.

Abstract

This memo describes the Application Exchange (APEX) access service,
addressed as the well-known endpoint "apex=access". The access
service is used to control use of both the APEX "relaying mesh" and
other APEX services.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Use and Management of Access Information . . . . . . . . . . . 3
2.1 Querying Access Information . . . . . . . . . . . . . . . . . 3
2.2 Retrieval of Access Information . . . . . . . . . . . . . . . 4
2.3 Update of Access Information . . . . . . . . . . . . . . . . . 5
3. Format of Access Entries . . . . . . . . . . . . . . . . . . . 9
3.1 Finding the Appropriate Entry: Matching Owners and Actors . . 11
3.2 Creating and Updating Access Entries . . . . . . . . . . . . . 14
4. The Access Service . . . . . . . . . . . . . . . . . . . . . . 14
4.1 Use of XML and MIME . . . . . . . . . . . . . . . . . . . . . 15
4.2 The Query Operation . . . . . . . . . . . . . . . . . . . . . 16
4.3 The Get Operation . . . . . . . . . . . . . . . . . . . . . . 17
4.4 The Set Operation . . . . . . . . . . . . . . . . . . . . . . 18
4.5 The Reply Operation . . . . . . . . . . . . . . . . . . . . . 20
5. Registration: The Access Service . . . . . . . . . . . . . . . 20
6. The Access Service DTD . . . . . . . . . . . . . . . . . . . . 21

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

7. Security Considerations . . . . . . . . . . . . . . . . . . . 23
References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 24
A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 26

1. Introduction

This memo describes an access service that is built upon the APEX [1]
"relaying mesh". The APEX access service is used to control use of
both the relaying mesh and other APEX services.

APEX, at its core, provides a best-effort datagram service. Within
an administrative domain, all relays must be able to handle messages
for any endpoint within that domain. APEX services are logically
defined as endpoints but given their ubiquitous semantics they do not
necessarily need to be associated with a single physical endpoint.
As such, they may be provisioned co-resident with each relay within
an administrative domain, even though they are logically provided on
top of the relaying mesh, i.e.,

+----------+ +----------+ +----------+ +---------+
| APEX | | APEX | | APEX | | |
| access | | presence | | report | | ... |
| service | | service | | service | | |
+----------+ +----------+ +----------+ +---------+
| | | |
| | | |
+----------------------------------------------------------------+
| |
| APEX core |
| |
+----------------------------------------------------------------+

That is, applications communicate with an APEX service by exchanging
data with a "well-known endpoint" (WKE).

APEX applications communicate with the access service by exchanging
data with the well-known endpoint "apex=access" in the corresponding
administrative domain, e.g., "[email protected]" is the
endpoint associated with the access service in the "example.com"
administrative domain.

Note that within a single administrative domain, the relaying mesh
makes use of the APEX access service in order to determine if an
originator is allowed to transmit data to a recipient (c.f., Step 5.3
of Section 4.4.4.1 of [1]).

Rose, et. al. Standards Track [Page 2]

RFC 3341 The Application Exchange (APEX) Access Service July 2002

2. Use and Management of Access Information

Access information is organized around access entries, each of which
contains:

o an owner: an APEX address with which the entry is associated;

o an actor: an APEX address that is granted permission to perform
some action in the context of the owner;

o a list of actions; and,

o a timestamp indicating when the service last created or modified
the access entry.

The access entry for a given owner controls access to a potentially
large range of different APEX services, such as data delivery, access
control, and presence information. In addition, Section 4.5 of [1]
discusses APEX access policies that govern such activities as peer
authentication, message relaying, and so on.

Management of access information falls into three categories:

o applications may query the access service to see if one or more
actions are allowed;

o applications may retrieve access information associated with an
owner/actor combination; and,

o applications may modify (i.e., create, replace, or delete) access
information associated with an owner/actor combination.

Each is now described in turn.

2.1 Querying Access Information

When an application wants to determine whether one or more actions
are allowed for an owner/actor combination, it sends a "query"
element to the service, e.g.,

+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+

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C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<query owner='[email protected]' transID='1'
actor='[email protected]'
actions='core:data presence:subscribe' />
</data-content>
</data>
S: <ok />

The service immediately responds with either an allow or deny
operation containing the same transaction-identifier, where "allow"
means that all of the actions listed in the query are permitted,
e.g.,

+-------+ +-------+
| | <------- data -- | |
| relay | |access |
| | -- ok ---------> | svc. |
+-------+ +-------+

C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<allow transID='1' />
</data-content>
</data>
S: <ok />

or

C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<deny transID='1' />
</data-content>
</data>
S: <ok />

2.2 Retrieval of Access Information

When an application wants to retrieve the access entry associated
with an owner/actor combination (typically in preparation for
updating that access information), it sends a "get" element to the
service, e.g.,

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+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+

C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<get transID='2'
owner='[email protected]'
actor='*@example.com' />
</data-content>
</data>
S: <ok />

The service immediately responds with a set operation containing the
access entry and the same transaction-identifier, e.g.,

+-------+ +-------+
| | <------- data -- | |
| relay | |access |
| | -- ok ---------> | svc. |
+-------+ +-------+

C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<set transID='2'>
<access owner='[email protected]'
actor='*@example.com'
actions='core:data presence:subscribe'
lastUpdate='2000-05-14T13:02:00-08:00' />
</set>
</data-content>
</data>
S: <ok />

2.3 Update of Access Information

When an application wants to create or modify an access entry
associated with an owner/actor combination, it sends a "set" element
to the service containing the new access entry, e.g.,

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+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+

C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<set transID='1'>
<access owner='[email protected]'
actor='*@example.com'
actions='core:data presence:subscribe'
lastUpdate='2000-05-14T13:02:00-08:00' />
</set>
</data-content>
</data>
S: <ok />

Note that Step 4 of Section 4.4 requires that the "lastUpdate"
attribute of an access entry be supplied in order to update that
entry; accordingly, applications must successfully retrieve an access
entry prior to trying to modify that entry. (Naturally,
administrators should ensure that applications authorized to modify
an access entry are also authorized to retrieve that entry.)

The service immediately responds with a reply operation containing
the same transaction-identifier, e.g.,

+-------+ +-------+
| | <------- data -- | |
| relay | |access |
| | -- ok ---------> | svc. |
+-------+ +-------+

C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<reply code='250' transID='1' />
</data-content>
</data>
S: <ok />

Note that Steps 6.2 and 9.2 of Section 4.4 require that the access
service update the "lastUpdate" attribute of an access entry when it
is created or modified.

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The service also immediately sends a set operation to the owner
attribute associated with the access entry, e.g.,

+-------+ +-------+
| | <------- data -- | |
| relay | |access |
| | -- ok ---------> | svc. |
+-------+ +-------+

C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<set transID='1'>
<access owner='[email protected]'
actor='*@example.com'
actions='core:data presence:subscribe'
lastUpdate='2000-05-14T23:02:00-08:00' />
</set>
</data-content>
</data>
S: <ok />

When an application wants to delete the access entry associated with
an owner/actor combination, it sends a "set" element to the service
omitting the permitted actions, e.g.,

+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+

C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<set transID='2'>
<access owner='[email protected]'
actor='*@example.com'
lastUpdate='2000-05-14T13:02:00-08:00' />
</set>
</data-content>
</data>
S: <ok />

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

The service immediately responds with a reply operation containing
the same transaction-identifier, e.g.,

+-------+ +-------+
| | <------- data -- | |
| relay | |access |
| | -- ok ---------> | svc. |
+-------+ +-------+

C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<reply code='250' transID='2' />
</data-content>
</data>
S: <ok />

The service also immediately sends a set operation to the owner
attribute associated with the access entry, e.g.,

+-------+ +-------+
| | <------- data -- | |
| relay | |access |
| | -- ok ---------> | svc. |
+-------+ +-------+

C: <data content='#Content'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
<data-content Name='Content'>
<set transID='2'>
<access owner='[email protected]'
actor='*@example.com'
lastUpdate='2000-05-14T13:02:00-08:00' />
</set>
</data-content>
</data>
S: <ok />

Because there are no actions associated with this access entry, the
owner knows that the entry has been deleted.

Note that because access control supported limited wildcarding of
actors, deleting an access entry for a particular owner/actor
combination, may modify, rather than remove, permission. Because of
this, a special action, "all:none", is used.

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For example, consider these two access entries:

<access owner='[email protected]'
actor='[email protected]'
actions='core:data presence:subscribe presence:watch'
lastUpdate='2000-05-14T13:20:00-08:00' />

<access owner='[email protected]'
actor='*@example.com'
actions='core:data'
lastUpdate='2000-05-14T13:20:00-08:00' />

Deleting the first access entry will not remove all permissions for
for the actor "[email protected]".

Instead, the first access entry should be modified thusly:

<access owner='[email protected]'
actor='[email protected]'
actions='all:none'
lastUpdate='2000-05-14T13:20:00-08:00' />

3. Format of Access Entries

Each administrative domain is responsible for maintaining one or more
"access entries" for each of its endpoints and associated
subaddresses (regardless of whether those addresses are currently
attached to the relaying mesh).

A separate access entry is required for each actor or group of actors
for whom access permission is specified. Section 6 defines the
syntax for access entries. Each access entry has an "owner"
attribute, an "actor" attribute, an "actions" attribute, a
"lastUpdate" attribute, and no content:

o the "owner" attribute specifies the address (endpoint or
subaddress) associated with the access entry;

o the "actor" attribute specifies an entity or group of entities for
whom access permissions are specified, as described below;

o the "actions" attribute specifies the permissions granted to the
actor in the context of the owner; and,

o the "lastUpdate" attribute specifies the date and time that the
service last created or modified the access entry.

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An action is specified as a service/operation pair, e.g., the action
"presence:publish" refers to the "publish" operation of the
"presence" service. Two service values are reserved:

o "all" is used to refer to all services, e.g., "all:data"; and,

o "core" is used to refer to the service implemented by the relaying
mesh, e.g., the "core:data" permission is consulted by the
relaying mesh (c.f., Step 5.3 of Section 4.4.4.1 of [1]).

Further, two operation values are reserved:

o "all" is used to refer to all operations, e.g., "presence:all";
and,

o "none" is used to refer to no operations whatsoever, e.g.,
"all:none".

An actor is an APEX address and is specified using the "entity"
syntax specified in Section 2.2 of [1]. However, both the "local"
and "domain" parts may contain limited wildcarding:

o The "local" part is either:

* a literal string (e.g., "fred");

* a subaddress wildcard (e.g., "fred/*" or "apex=pubsub/*"); or,

* the value "apex=*", specifying all APEX services;

* the value "*", specifying any address other than an APEX
service.

o The "domain" part is either:

* a FQDN (e.g., "example.com");

* a domain wildcard (e.g., "*.example.com"); or,

* the value "*", specifying all administrative domains.

Note that in the case of a domain wildcard, the wildcard itself
matches zero or more subdomains, e.g., "*.example.com" matches
"example.com", "foo.example.com", "bar.foo.example.com", and so
on.)

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The following default entries are provided for each owner, but are
overridden by an explicitly supplied entry with the same actor value:

actor='local@domain' actions='all:all'
actor='apex=*@domain' actions='all:all'
actor='apex=*@*' actions='core:data'
actor='*@*' actions='all:none'

where "local@domain" specifies the owner associated with the access
entry.

For example, the explicit entry

actor='*@*' actions='core:data'

allows endpoints from any domain to use the relaying mesh to send
data to the owner, but does not override the default entry for
"apex=*@domain", which allows all APEX services in the owner's domain
access to all actions.

APEX endpoint names can legitimately contain the character '*', but
access entries use '*' to indicate wildcarding. Accordingly, the
two-character sequence '\*' is used to avoid ambiguity in the "actor"
attribute. Similarly, to explicitly specify an endpoint name
containing '\' in the "actor" attribute, the two-character sequence
'\\' is used.

Note that this convention is used only for the "actor" attribute of
the "get" operation and of the "access" entry that appears in the
"set" operation; however, this convention is not used in the "query"
operation, as this operation does not allow wildcarding.

For example, to specify the endpoint named as "a\b*[email protected]" in
the "get" operation or in an "access" entry, the string
"a\\b\*[email protected]" is used; but in the "query" operation, the
string "a\b*[email protected]" is used. (Of course, as name allocation
is a local matter, these complications can be avoided by the simple
expedient of not using endpoint names containing '*' or '\'.)

3.1 Finding the Appropriate Entry: Matching Owners and Actors

The use of actor wildcarding makes it possible for several access
entries to apply for a given owner/actor combination. When
determining which access entry to use when responding to the query
operation, the algorithm is:

o Consider only those access entries that are associated with the
given owner.

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

o Consider only those access entries in which the actor value
matches the actor address in the query. If the wildcard character
('*') is present, then it a match is possible only if each
wildcard character can be replaced with a non-empty character
sequence (one or more characters) to obtain a value identical to
the address in the query.

o Order those remaining access entries:

* Use the exactness of the match with the domain part of the
actor value as the primary key; and,

* Use the exactness of the match with the local part of the actor
value as the secondary key.

o When matching with the domain part, an exact match is the best
match; otherwise, the shorter the wildcard match, the higher the
priority.

For example, if the actor's domain is "bar.foo.example.com", a
match against an entry of "*.foo.example.com" is better than a
match against an entry of "*.example.com".

o When matching with the local part, an exact match is the best
match; otherwise, the shorter the wildcard match, the higher the
priority. This is true regardless of whether the wildcarding is
for subaddress or service. (Note that a local part with a
wildcard subaddress does not have a non-empty match with the same
local part without a subaddress.)

For example, consider these access entries:

<access owner='[email protected]'
actor='[email protected]'
actions='all:all'
lastUpdate='2000-05-14T13:20:00-08:00' />
<access owner='[email protected]'
actor='[email protected]'
actions='core:data'
lastUpdate='2000-05-14T13:20:00-08:00' />
<access owner='fred/[email protected]'
actor='barney/[email protected]'
actions='core:data'
lastUpdate='2000-05-14T13:20:00-08:00' />
<access owner='[email protected]'
actor='*@example.com'
actions='core:data presence:subscribe presence:watch'
lastUpdate='2000-05-14T13:20:00-08:00' />

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<access owner='[email protected]'
actor='*@*'
actions='core:data'
lastUpdate='2000-05-14T13:20:00-08:00' />

Briefly:

o For addresses within the "example.com" administrative domain:

* "fred", "wilma", and all APEX services within the "example.com"
administrative domain are allowed access to all operations for
"[email protected]";

* "mr.slate" is allowed access only to send data through the
relaying mesh to "[email protected]";

* "barney/appl=wb" is allowed access only to send data to "fred/
appl=wb", a subaddress of "[email protected]"; and,

* any other address within the "example.com" administrative
domain is allowed access to send data and invoke the
"subscribe" and "watch" operations of the APEX presence service
with respect to "[email protected]".

o For any address outside the "example.com" administrative domain,
the address is allowed access to send data, regardless of whether
it is an APEX service.

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Note that although the four default entries are always available, the
explicit entry for actor "*@*" overrides the corresponding default
entry.

3.2 Creating and Updating Access Entries

The get and set operations are provided as a basic mechanism for
creating and updating access rules, for which no special wildcard
processing is performed.

The actor value for an access entry may contain limited wildcard
characters which have special significance only when performing a
query operation (cf., Section 3.1). For the purposes of retrieving
and updating entries, actor values are treated simply as literal
names.

4. The Access Service

Section 5 contains the APEX service registration for the access
service:

o Within an administrative domain, the service is addressed using
the well-known endpoint of "apex=access".

o Section 6 defines the syntax of the operations exchanged with the
service.

o A consumer of the service initiates communications by sending data
containing a query, get, or set operation.

o The service replies to these operations.

o When an access entry is changed, the service sends a notification
to the owner associated with the changed entry.

An implementation of the service must maintain information about
access entries in persistent storage.

Consult Section 6.1.1 of [1] for a discussion on the properties of
long-lived transaction-identifiers.

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

4.1 Use of XML and MIME

Section 4.1 of [1] describes how arbitrary MIME content is exchanged
as a BEEP [2] payload. For example, to transmit:

<data content='...'>
<originator identity='[email protected]' />
<recipient identity='[email protected]' />
</data>

where "..." refers to:

<query owner='[email protected]' transID='1'
actor='[email protected]'
actions='core:data presence:subscribe' />

then the corresponding BEEP message might look like this:

C: MSG 1 2 . 42 1234
C: Content-Type: multipart/related; boundary="boundary";
C: start="<[email protected]>";
C: type="application/beep+xml"
C:
C: --boundary
C: Content-Type: application/beep+xml
C: Content-ID: <[email protected]>
C:
C: <data content='cid:[email protected]'>
C: <originator identity='[email protected]' />
C: <recipient identity='[email protected]' />
C: </data>
C: --boundary
C: Content-Type: application/beep+xml
C: Content-ID: <[email protected]>
C:
C: <query owner='[email protected]' transID='1'
C: actor='[email protected]'
C: actions='core:data presence:subscribe' />
C: --boundary--
C: END

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or this:

C: MSG 1 1 . 42 267
C: Content-Type: application/beep+xml
C:
C: <data content='#Content'>
C: <originator identity='[email protected]' />
C: <recipient identity='[email protected]' />
C: <data-content Name='Content'>
C: <query owner='[email protected]' transID='1'
C: actor='[email protected]'
C: actions='core:data presence:subscribe' />
C: </data-content>
C: </data>
C: END

4.2 The Query Operation

When an application wants to see if a particular operation is
allowed, it sends a "query" element to the service.

The "query" element has an "owner" attribute, an "actor" attribute,
an "actions" attribute, a "transID" attribute, and no content:

o the "owner" attribute specifies the address associated with the
access entry;

o the "actor" attribute specifies the address (without wildcarding)
for which access permissions are queried;

o the "actions" attribute specifies one or more actions for which
permission is queried; and,

o the "transID" attribute specifies the transaction-identifier
associated with this operation.

When the service receives a "query" element, we refer to the "owner"
attribute as the "subject". The service performs these steps:

1. If the subject is outside this administrative domain, a "reply"
element having code 553 is sent to the originator.

2. If the subject does not refer to a valid address, a "reply"
element having code 550 is sent to the originator.

3. If the subject's access entry matching the originator does not
contain an "access:query" token, a "reply" element having code 537
is sent to the originator.

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4. The subject's access entry matching the actor attribute of the
query element is selected (cf., Section 3.1).

5. If all of the permissions in the "actions" attribute of the query
element are contained in the selected access entry, then an
"allow" element is sent to the originator.

6. Otherwise, a "deny" element is sent to the originator.

Regardless of whether an "allow", "deny", or "reply" element is sent
to the originator, the "transID" attribute is identical to the value
found in the "query" element sent by the originator.

4.3 The Get Operation

Prior to creating or updating an access entry for some owner/actor
combination, an application will usually need to retrieve any
existing access entry. It does so by sending a "get" element to the
service. In particular, a successful response returns a "lastUpdate"
value that is necessary when sending a subsequent "set" element.

The "get" element has an "owner" attribute, an "actor" attribute, a
"transID" attribute, and no content:

o the "owner" attribute specifies the address associated with the
access entry;

o the "actor" attribute specifies the address (with possible
wildcarding) for which access permissions are retrieved; and,

o the "transID" attribute specifies the transaction-identifier
associated with this operation.

When the service receives a "get" element, we refer to the "owner"
attribute as the "subject". The service performs these steps:

1. If the subject is outside this administrative domain, a "reply"
element having code 553 is sent to the originator.

2. If the subject does not refer to a valid address, a "reply"
element having code 550 is sent to the originator.

3. If the subject's access entry matching the originator does not
contain an "access:get" token, a "reply" element having code 537
is sent to the originator.

4. The subject's access entry whose "actor" attribute identically
matches the "actor" attribute of the "get" element is selected.

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

5. If no such entry exists, a "reply" element having code 551 is sent
to the originator.

6. Otherwise, a "set" element corresponding to the selected access
entry is sent to the originator.

Regardless of whether a "set" or "reply" element is sent to the
originator, the "transID" attribute is identical to the value found
in the "get" element sent by the originator.

4.4 The Set Operation

When an application wants to modify (i.e., create, replace, or
delete) the access entry associated with an owner/actor combination,
it sends a "set" element to the service.

The "set" element has a "transID" attribute, and contains an "access"
element:

o the "transID" attribute specifies the transaction-identifier
associated with this operation; and,

o the "access" element contains the access entry to be created,
replaced, or deleted.

The "access" element has an "owner" attribute, an "actor" attribute,
an optional "actions" attribute, an optional "lastUpdate" attribute,
and no content:

o the "owner" attribute specifies the address associated with the
access entry;

o the "actor" attribute specifies the address (with possible
wildcarding) for which access permissions are specified;

o the "actions" attribute (present only to add or replace an entry)
specifies one or more actions for which permission is to be
determined; and,

o the "lastUpdate" attribute (present only to replace or delete an
entry) specifies the current timestamp of the access entry that is
to be replaced.

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

When the service receives a "set" element, we refer to the "owner"
attribute of the access element as the "subject". The service
performs these steps:

1. If the subject is outside this administrative domain, a "reply"
element having code 553 is sent to the originator.

2. If the subject does not refer to a valid address, a "reply"
element having code 550 is sent to the originator.

3. If the subject's access entry matching the originator does not
contain an "access:set" token, a "reply" element having code 537
is sent to the originator.

4. The subject's access entry whose "actor" attribute identically
matches the "actor" attribute of the "set" element is selected.

5. If no such entry exists and the "lastUpdate" attribute is present
in the supplied "set" element, a "reply" element having code 555
is sent to the originator.

6. If no such entry exists and the "lastUpdate" attribute is absent
in the supplied "set" element, then:

1. The access entry for the owner/actor combination is created
from the supplied "access" element.

2. The "lastUpdate" attribute of that access entry set to the
service's notion of the current date and time.

3. A "reply" element having code 250 is sent to the originator.

4. A "set" element corresponding to the newly-created access entry
is sent to the subject's address.

7. If the selected entry exists, but its "lastUpdate" attribute is
not semantically identical to the "lastUpdate" attribute of the
supplied "access" element, a "reply" element having code 555 is
sent to the originator.

8. If "actions" attribute of the supplied "access" element is not
present, then:

1. The selected entry is deleted.

2. A "reply" element having code 250 is sent to the originator.

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

3. A "set" element corresponding to the owner/actor combination,
but lacking an "actions" attribute is sent to the subject's
address.

9. Otherwise:

1. The access entry for the owner/actor combination is updated
from the supplied "access" element.

2. The "lastUpdate" attribute of the updated access entry is set
to the service's notion of the current date and time (which
should be different from the "lastUpdate" value associated with
any replaced entry).

3. A "reply" element having code 250 is sent to the originator.

4. A "set" element corresponding to the newly-updated access entry
is sent to the subject's address.

When sending the "reply" element, the "transID" attribute is
identical to the value found in the "set" element sent by the
originator.

4.5 The Reply Operation

While processing operations, the service may respond with a "reply"
element. Consult Sections 10.2 and 6.1.2 of [1], respectively, for
the definition and an exposition of the syntax of the reply element.

5. Registration: The Access Service

Well-Known Endpoint: apex=access

Syntax of Messages Exchanged: c.f., Section 6

Sequence of Messages Exchanged: c.f., Section 4

Access Control Tokens: access:query, access:get, access:set

Contact Information: c.f., the "Authors' Addresses" section of this
memo

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

6. The Access Service DTD



<!ENTITY % APEXCORE PUBLIC "-//IETF//DTD APEX CORE//EN" "">
%APEXCORE;



<!ENTITY % ACTOR "CDATA">
<!ENTITY % ACTIONS "NMTOKENS">



<!ELEMENT query EMPTY>
<!ATTLIST query
owner %ENDPOINT; #REQUIRED
actor %ACTOR; #REQUIRED
actions %ACTIONS; #REQUIRED
transID %UNIQID; #REQUIRED>

<!ELEMENT get EMPTY>
<!ATTLIST get
owner %ENDPOINT; #REQUIRED
actor %ACTOR; #REQUIRED
transID %UNIQID; #REQUIRED>

<!ELEMENT set (access)>
<!ATTLIST set
transID %UNIQID; #REQUIRED>

<!ELEMENT allow EMPTY>
<!ATTLIST allow
transID %UNIQID; #REQUIRED>

<!ELEMENT deny EMPTY>
<!ATTLIST deny
transID %UNIQID; #REQUIRED>



<!ELEMENT access EMPTY>
<!ATTLIST access
owner %ENDPOINT; #REQUIRED
actor %ACTOR; #REQUIRED
actions %ACTIONS; #IMPLIED
lastUpdate %TIMESTAMP; #IMPLIED>

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

7. Security Considerations

Consult [1]'s Section 11 for a discussion of security issues.

In addition, timestamps issued by the the access service may disclose
location information. If this information is considered sensitive,
the special timezone value "-00:00" may be used (after converting the
local time accordingly).

References

[1] Rose, M., Klyne, G. and D. Crocker, "The Application Exchange
Core", RFC 3340, July 2002.

[2] Rose, M., "The Blocks Extensible Exchange Protocol Core", RFC
3080, March 2001.

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

Authors' Addresses

Marshall T. Rose
Dover Beach Consulting, Inc.
POB 255268
Sacramento, CA 95865-5268
US

Phone: +1 916 483 8878
EMail: [email protected]

Graham Klyne
Clearswift Corporation
1310 Waterside
Arlington Business Park
Theale, Reading RG7 4SA
UK

Phone: +44 11 8903 8903
EMail: [email protected]

David H. Crocker
Brandenburg Consulting
675 Spruce Drive
Sunnyvale, CA 94086
US

Phone: +1 408 246 8253
EMail: [email protected]
URI: http://www.brandenburg.com/

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

Appendix A. Acknowledgements

The authors gratefully acknowledge the contributions of: Neil Cook,
Darren New, Chris Newman, Scott Pead, and Bob Wyman.

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RFC 3341 The Application Exchange (APEX) Access Service July 2002

Full Copyright Statement

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others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
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Acknowledgement

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Rose, et. al. Standards Track [Page 26]