Handle System Namespace and Service Definition
draft-sun-handle-system-def-08
The information below is for an old version of the document that is already published as an RFC.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 3651.
|
|
|---|---|---|---|
| Authors | Larry Lannom , Sean Reilly , Sam Sun | ||
| Last updated | 2020-01-21 (Latest revision 2003-07-01) | ||
| RFC stream | Independent Submission | ||
| Formats | |||
| Stream | ISE state | (None) | |
| Consensus boilerplate | Unknown | ||
| Document shepherd | (None) | ||
| IESG | IESG state | RFC 3651 (Informational) | |
| Telechat date | (None) | ||
| Responsible AD | Ted Hardie | ||
| IESG note |
It is suggested that these go forward with the following IESG Note attached (originally drafted by Patrik): IESG NOTE: The IETF and IRTF have discussed the Handle system in the realm of URI-related work. The IESG wishes to point out that there is no IETF consensus on the current Handle system nor on where it fits in the IETF architecture. The IESG is of the view that the Handle system would be able to, with very small changes, fit into the IETF architecture as a URN namespace. These documents, however, contain information on the Handle system without these changes. |
||
| Send notices to | <boesch@arpa.mil> |
draft-sun-handle-system-def-08
Internet Draft Sam X. Sun
Document: draft-sun-handle-system-def-08.txt Sean Reilly
Expires: December 2003 Larry Lannom
CNRI
June 2003
Handle System Namespace and Service Definition
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as "work in
progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
The Handle System is a general-purpose global name service that
allows secured name resolution and administration over the public
Internet. This document provides a detailed description of the
Handle System namespace, and its data, service, and operation
models. The namespace definition specifies the handle syntax and
its semantic structure. The data model defines the data structures
used by the handle system protocol and any pre-defined data types
for carrying out the handle service. The service model provides
definitions of various Handle System components and explains how
they work together over the network. Finally, the handle system
operation model describes its service operation in terms of
messages transmitted between client and server, and the client
authentication process based on the handle system authentication
protocol.
Table of Contents
1. Introduction..................................................2
2. Handle System Namespace.......................................3
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3. Handle System Data Model......................................4
3.1 Handle Value Set.............................................4
3.2 Pre-defined Handle Data Types................................9
3.2.1 Handle Administrator: HS_ADMIN............................9
3.2.2 Service Site Information: HS_SITE........................14
3.2.3 Naming Authority Delegation Service: HS_NA_DELEGATE......19
3.2.4 Service Handle: HS_SERV..................................19
3.2.5 Alias Handle: HS_ALIAS...................................20
3.2.6 Primary Site: HS_PRIMARY.................................21
3.2.7 Handle Value List: HS_VLIST..............................21
4. Handle System Service Model..................................21
4.1 Handle System Service Components............................22
4.1.1 Global Handle Registry (GHR).............................22
4.1.2 Local Handle Service (LHS)...............................24
4.2 Handle System Middle-Ware Components........................26
4.2.1 Handle System Caching Service............................26
4.2.2 Handle System Proxy Server...............................26
4.3 Handle System Client Components.............................27
5. Handle System Operation Model................................28
5.1 Handle System Service Request and Response..................28
5.2 Handle System Authentication Protocol.......................31
6. Security Considerations......................................34
References and Bibliography.....................................35
Author's Addresses..............................................36
1. Introduction
The Handle System manages handles as globally unique names for
Internet resources. It was originally conceived and described in a
paper by Robert Kahn and Robert Wilensky [22] in 1995. The Handle
System provides a general-purpose global name service that allows
handles to be resolved and administrated securely over the public
Internet. The Handle System categorizes its service into two
categories: the handle resolution service and the handle
administration service. Clients use handle resolution service to
resolve handles into their values. The handle administration
service deals with client requests to manage these handles,
including adding and deleting handles, and updating handle values.
The document "Handle System Overview" [1] provides an architectural
overview of the Handle System, and its relationship to other
Internet services such as DNS [2,3] and LDAP[4]. This document
provides a detailed description of the Handle System namespace, its
data and service model, and its operation model. It assumes that
readers are familiar with the basic concepts of the Handle System
as described in the overview document.
The namespace definition specifies the handle syntax and its
semantic structure. The data model defines the data structures used
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by the handle system protocol and any pre-defined data types for
carrying out the handle service. The service model provides
definitions of various Handle System components and explains how
they work together over the network. Finally, the handle system
operation model describes its service operation in terms of
messages transmitted between client and server, and the client
authentication process based on the handle system authentication
protocol.
2. Handle System Namespace
Handles are character strings that may consist of a wide range of
characters. Every handle in the Handle System consists of two
parts: its naming authority, followed by a unique local name under
the naming authority. The naming authority and the local name are
separated by the ASCII character "/" (octet 0x2F). The following
table provides the handle syntax definition in ABNF [5] notation:
<Handle> = <NamingAuthority> "/" <LocalName>
<NamingAuthority> = *(<NamingAuthority> ".") <NAsegment>
<NAsegment> = 1*(%x00-2D / %x30-3F / %x41-FF )
; any octets that map to UTF-8 encoded
; Unicode 2.0 characters except
; octets '0x2E' and '0x2F' (which
; correspond to the ASCII characters '.',
; and '/').
<LocalName> = *(%x00-FF)
; any octets that map to UTF-8 encoded
; Unicode 2.0 characters
Table 2.1: Handle syntax
As shown in Table 2.1, both <NamingAuthority> and <LocalName> are
UTF-8 [6] encoded character strings. The handle system protocol
mandates UTF-8 encoding for handles transferred over the wire. The
<LocalName> may consist of any characters from the Unicode 2.0
standard [7]. The <NamingAuthority> may use any characters from the
Unicode 2.0 standard except the ASCII character '/' (0x2F), which
is reserved to separate the <NamingAuthority> from the <LocalName>.
A <NamingAuthority> may consist of multiple non-empty <NAsegment>s,
each of which separated by the ASCII character '.' (octet 0x2E).
Naming authorities are defined in a hierarchical fashion resembling
a tree structure. Each node and leaf of the tree is given a label
that corresponds to a naming authority segment (<NAsegment>). The
parent node represents the parent naming authority. Naming
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authorities are constructed left to right, concatenating the labels
from the root of the tree to the node that represents the naming
authority. Each label (or its <NAsegment>) is separated by the
character '.' (octet 0x2E). For example, the naming authority for
the Digital Object Identifier (DOI) project is "10". It is a root-
level naming authority as it has no parent naming authority for
itself. It can, however, have many child naming authorities. For
example, "10.1045" is a child naming authority of "10" for the D-
Lib Magazine.
By default, handles are case sensitive. However, a handle service,
global or local, may implement its namespace so that ASCII
characters under the namespace are treated as case insensitive. For
example, the global handle service, formally known as the Global
Handle Registry (GHR), is implemented such that ASCII characters
are treated as case insensitive. Since the GHR manages all handles
for naming authorities, ASCII characters in naming authorities are
treated as case insensitive.
3. Handle System Data Model
The Handle System provides a name-to-value binding service over the
public Internet. Each handle may have a set of values assigned to
it. The Handle System maintains the value set of each handle and
will return it in response to any handle resolution request. The
handle system data model defines the conceptual data structure for
these values. The data model used by the protocol may not be the
exact physical data model used for storage in any specific
implementation. Rather, it is the data model followed by the handle
system protocol as specified in the "Handle System Protocol
Specification" [8].
3.1 Handle Value Set
Each handle may have a set of values assigned to it. These handle
values use a common data structure for its data. For example, each
handle value has a unique index number that distinguishes it from
other values in the value set. It also has a specific data type
that defines the syntax and semantics of the data in its data
field. Besides these, each handle value contains a set of
administrative information such as TTL and permissions. Figure 3.1
shows the handle "10.1045/may99-payette" with a set of three handle
values. One of these values (with index number set to 1) is shown
in detail. (Note that the encoding of the length for each field is
not shown in Figure 3.1. Also, the empty <reference> field consists
of a 4-byte integer whose value is zero.)
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Handle "10.1045/may99-payette"
|
|
V
-------------------------------------------------------------
| <index>: 3 |
------------------------------------------------------------- |
| <index>: 2 | |
------------------------------------------------------------- | |
| | | |
| <index>: 1 | | |
| <type>: URL | | |
| <data>: http://www.dlib.org/dlib... | | |
| <TTL>: {Relative: 24 hours} | | |
| <permission>: PUBLIC_READ, ADMIN_WRITE | | |
| <timestamp>: 927314334000 | | |
| <reference>: {empty} | |-
| |-
-------------------------------------------------------------
Figure 3.1: Handle "10.1045/may99-payette" and its set of values
In Figure 3.1, it shows a handle value whose its index is set to 1.
The data type for the handle value is URL. The URL data as stated
in the <data> field is "http://www.dlib.org/dlib...". The TTL (time
to live) entry suggests that the value record should be cached no
more than 24 hours before the source of the information to be
consulted again. The <permission> field grants anyone permission to
read, but only the administrator to update the value. The
<reference> field is empty. It may contain a list of references to
other handle values as credentials for this handle value.
Thus a handle value may be thought of as a record that consists of
a group of data fields. Each of these data fields is defined as
follows:
<index>
An unsigned 32-bit integer that uniquely identifies a handle
value from other handle values.
<type>
A UTF8-string that identifies the data type for the value record.
Note that throughout this document, a UTF8-string is defined as a
data structure that consists of a 4-byte unsigned integer
followed by an UTF-8 encoded character string. The integer
specifies the number of octets in the character string.
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The <type> field identifies the data type that defines the syntax
and semantics of data in the next <data> field. The data type may
be registered with the Handle System to avoid potential
conflicts. The Handle System has a reserved naming authority
"0.TYPE" for registered data types. For example, "URL" (as shown
in Figure 3.1) is a registered data type. It is registered as the
handle "0.TYPE/URL". The handle may have a value that explains
the syntax and semantics of the data type.
Data types under the Handle System may be hierarchical. Each
level of the hierarchy may be named in terms of a UTF8-String
with no '.' (0x2E) characters. The '.' character is used to mark
the boundary between hierarchy levels. For example, the handle
system data type "a.b" may be considered as a sub-type "b" under
the type "a". Similarly, handle values of <type> "a.b.x", "a.b.y"
and "a.b.z" may be considered as handle values under the common
type hierarchy "a.b".
For any handle values, the UTF8-string in the <type> field may
not end with the '.' character. In other words, no handle system
data type should end with the '.' character. However, the '.'
character may appear in the end of the <type> parameter in a
handle query. This is used to query for all handle values under a
common type hierarchy. For example, one may query for all handle
values under the type hierarchy "a.b" (e.g. handle values of
<type> "a.b.x", "a.b.y" and "a.b.z") by setting the <type>
parameter to "a.b.". Note here that the <type> parameter ends
with the '.' character. Details of the handle query operation can
be found in the handle system protocol specification [8].
<data>
A sequence of octets (preceded by its length in a 4-byte unsigned
integer) that describes the resource identified by the handle.
The syntax and semantics of these octets are identified by the
<type> field.
<permission>
An eight-bit bit-mask for access control of the handle value.
Access control is defined in terms of read, write, and execute
permissions, applicable to either general public or handle
administrator(s). Each handle value can have its permission field
specified as any combination of the following bits:
PUBLIC_WRITE (0x01) permission that allows anyone to
modify or delete the handle value.
PUBLIC_READ (0x02) permission that allows anyone to read
the handle value.
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ADMIN_WRITE (0x04) permission that allows any handle
administrator to update or delete the
handle value.
ADMIN_READ (0x08)_ permission that allows the handle
value to be read by any handle
administrator with AUTHORITIVE_READ
privilege.
PUBLIC_EXECUTE (0x10) permission that allows anyone to
execute the program identified by the
handle value on the handle host as
anonymous user. Because of the
security risks this may have brought
up, implementations may choose not to
support such permission, or provide
options so that it can be disabled at
deployment.
ADMIN_EXECUTE (0x20) permission that allows handle
administrator(s) to run the program
identified by the handle value on the
handle server. The handle server must
authenticate the handle administrator
before executing the program. The
handle administrator must have a
established account on the handle
server. The execution of the handle
value should assume the same
privilege as the one given to the
account for the handle administrator.
Because of the security risks this
may have brought up, implementations
may choose not to support such
permission, or provide options so
that it can be disabled at
deployment.
Note that a handle value with no PUBLIC_READ nor ADMIN_READ
permission can not leave the handle server. It may be used, for
example, to store secret keys for authentication purposes. A
handle value with neither PUBLIC_WRITE nor ADMIN_WRITE permission
makes the handle value immutable and cannot be deleted by any
handle administrator (via the handle system protocol).
The administrator for a given handle must specify the permission
for each handle value. Implementations may choose PUBLIC_READ and
ADMIN_WRITE as the default permission for each handle value.
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Handle servers must check permissions before fulfilling any
client request.
<TTL>
An octet followed by a 4-byte integer that specifies the Time-To-
Live of the value record. It is used to describe how long the
value record can be cached before the source of the information
should again be consulted. A zero value for a TTL indicates that
the value record should only be used for the transaction in
progress and should not be cached. Any non-zero TTL is defined in
terms of a TTL type (specified in the first octet), followed by
the TTL value (the 32-bit unsigned integer that follows the TTL
type). The TTL type indicates whether the TTL value is absolute
or relative. The absolute TTL value defines the time to live in
terms of seconds since 00:00:00 UTC, January 1st 1970. A relative
TTL specifies the time to live in terms of the number of seconds
elapsed since the value was obtained by the client from any
handle server.
<timestamp>
An 8-byte (long) integer that records the last time the value was
updated at the server. The field contains elapsed time since
00:00:00 UTC, January 1970 in milliseconds. The choice of
milliseconds is to avoid potential collision when updating the
value.
<reference>
A 4-byte integer followed by a list of references to other handle
values. The integer specifies the number of references in the
list. Each reference in the list refers to another handle value
in terms of a UTF8-string and a 4-byte integer (where the UTF8-
string is the handle name and the integer is the value index).
References are generally used to add credentials to the current
handle value. For example, a handle value may make itself more
trust-worthy by referring to a digital signature issued by a
commonly trusted entity.
By default, the Handle System returns all the handle values with
public-read permission in response of any resolution request. It is
possible for a client to ask for a subset of those values with
specific data type (e.g. all URLs assigned to the handle). The
client may also ask for a specific handle value based on a specific
value index.
Each handle value can be uniquely referenced by the combination of
the handle and its value index. Care must be taken when changing
the value index as it may break an existing reference to the handle
value. For example, suppose the handle X/Y has a value whose index
is 1. That value may be referred to as X/Y:1. If the handle
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administrator changes the value index from 1 to 2, the reference to
X/Y:1 will become obsolete. Any reference to the handle value will
have to change to X/Y:2.
Value records assigned to any handle may or may not have continuous
index numbers. Nor can it be assumed that the index will start with
0 or 1. A handle administrator may assign a handle value with any
index as long as each index is unique within the value set.
A handle value may be "privatized" or "disabled" by setting its
<permission> field as "authorized-read". This limits read-access to
the handle administrator only. The "privatized" value can then be
used to keep any historical data (on behalf of the handle
administrator) without exposing it to public. Such approach may
also be used to keep any obsolete handle or naming authority from
being reused accidentally.
3.2 Pre-defined Handle Data Types
Every handle value must have a data type specified in its <type>
field. The Handle System provides a type registration service that
allows organizations to register new data types for their
applications. Data types can be registered as handles under the
naming authority "0.TYPE". For example, the URL data type is
registered under the Handle System as the handle "0.TYPE/URL". The
handle may have a handle value that refers to RFC1738 [9], an IETF
standard document that defines the syntax and semantics of URL.
The Handle System pre-defines a set of data types to carry out the
handle service. For example, HS_ADMIN is a pre-defined data type
used to describe handle administrators or administrator groups.
HS_SITE is a pre-defined data type to describe the service
interface of any handle system service component. The following
sections provide detailed descriptions of these pre-defined data
types under the Handle System.
3.2.1 Handle Administrator: HS_ADMIN
Each handle has one or more administrators. Any administrative
operation (e.g., add, delete or modify handle values) can only be
performed by the handle administrator with adequate privilege.
Handle administrators are defined in terms of HS_ADMIN values.
Every handle must have at least one HS_ ADMIN value that defines
its administrator. Each HS_ADMIN value can be used to define a set
of handle administrators sharing the same administration privilege.
Handles with multiple administrators of different privileges may
have multiple HS_ADMIN values. HS_ADMIN values are used by the
Handle System to authenticate handle administrators before
fulfilling any handle administration request.
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Naming authorities, as described above, are themselves registered
as handles under the reserved naming authority "0.NA". These
handles are referred to as naming authority handles. Administrators
for any naming authority are so defined as the administrators of
the corresponding naming authority handle. For example, "0.NA/10"
is the naming authority handle for the naming authority "10". Hence
any administrator for the naming authority handle "0.NA/10" is also
the administrator for the naming authority "10". Naming authority
administrators are the only ones who can create handles or sub-
naming authorities under the naming authority. A sub-naming
authority may define its own set of administrators to create
handles or further levels of sub-naming authorities. For example,
the naming authority "10.1045" may have a totally different group
of administrators from its parent naming authority "10".
A HS_ADMIN value is a handle value whose <type> field is HS_ADMIN
and whose <data> field consists of the following entries:
<AdminRef>
A reference to a handle value. The reference consists of the
handle name (a UTF8-string) followed by a 4-byte unsigned integer
for the handle value index. The handle value identifies the set
of administrators for the handle.
<AdminPermission>
A 16-bit bit-mask that defines the administration privilege of
the set of handle administrators identified by the HS_ADMIN
value.
The <AdminRef> entry refers to a handle value that can be used to
authenticate the handle administrator. Such handle value is called
the handle administrator reference. The handle administrator
reference may contain the secret key, public key, or X.509
certificate [10] provided by the handle administrator. For example,
the <AdminRef> entry may contain a handle administrator reference
whose <type> field is DSS_WITH_DES_CBC_SHA and whose <data> field
contains a DES secret key [11], for use in the Cipher Block
Chaining (CBC) mode of operation [12, 13]. The secret key can be
used by the handle server to authenticate the handle administrator.
For stronger cryptographic algorithm, the handle administrator
reference may contain a set of Triple-DES keys [23] and set its
<type> to be DES-EDE3-WITH-CBC.
A single handle may be assigned with both the HS_ADMIN value and
the handle administrator reference. In other words, the <AdminRef>
entry may refer to a handle value assigned to the same handle that
has the HS_ADMIN value. In this case, authentication of the handle
administrator does not rely on any other handles. Alternatively,
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the handle administrator reference may be a handle value under a
different handle. Thus HS_ADMIN values from different handles may
share a common handle administrator reference. This feature allows
sharing of handle administrators among different handles. The
handle administrator reference contains the secret key, public key,
or X.509 certificate provided by the administrator of these
handles.
Handle administrator reference may be of type HS_VLIST and has its
<data> field contain a list of references to other handle values.
Each of these handle values defines a handle administrator
reference. The HS_VLIST value defines an administrator group. Each
handle administrator reference from the HS_VLIST is a member of the
administrator group. Each handle value reference is defined in
terms of a <handle>:<index> pair. An administrator group may also
contain other administrator groups as its members. This allows
administrator groups to be defined in a hierarchical fashion. Care
must be taken, however, to avoid cyclic definition of
administrators or administrator groups. Multiple levels of
administrator groups should be avoided due to their lack of
efficiency, but will not be signaled as an error. Client software
should be prepared to detect any potential cyclic definition of
administrators or <AdminRef> entries that point to non-existent
handle values and treat them as an error.
A handle can have multiple HS_ADMIN values, each of which defines a
different handle administrator. Different administrators can play
different roles or be granted different permissions. For example,
the naming authority handle "0.NA/10" may have two administrators,
one of which may only have permission to create new handles under
the naming authority, while the other may have permission to create
new sub-naming authorities (e.g. "10.1045"). The set of possible
permissions for a handle administrator is defined as follows:
Add_Handle (0x0001)
This permission allows naming authority administrator to create
new handles under a given naming authority.
Delete_Handle (0x0002)
This permission allows naming authority administrator to delete
handles under a given naming authority.
Add_NA (0x0004)
This permission allows the naming authority administrator to
create new sub-naming authorities.
Delete_NA (0x0008)
This permission allows naming authority administrator to delete
an existing sub-naming authority.
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Modify_Value (0x0010)
This permission allows handle administrator to modify any handle
values other than HS_ADMIN values. HS_ADMIN values are used to
define handle administrators and are managed by a different set
of permissions.
Delete_Value (0x0020)
This permission allows handle administrator to delete any handle
value other than the HS_ADMIN values.
Add_Value (0x0040)
This permission allows handle administrator to add handle values
other than the HS_ADMIN values.
Modify_Admin (0x0080)
This permission allows handle administrator to modify HS_ADMIN
values.
Remove_Admin (0x0100)
This permission allows handle administrator to remove HS_ADMIN
values.
Add_Admin (0x0200)
This permission allows handle administrator to add new HS_ADMIN
values.
Authorized_Read (0x0400)
This permission grants handle administrator read-access to handle
values with the ADMIN_READ permission. Administrators without
this permission will not have access to handle values that
require authentication for read access.
LIST_Handle (0x0800)
This permission allows naming authority administrator to list
handles under a given naming authority.
LIST_NA (0x1000)
This permission allows naming authority administrator to list
immediate sub-naming authorities under a given naming authority.
Administrator permissions are encoded in the <AdminPermission>
entry in the <data> field of any HS_ADMIN value. Each permission is
encoded as a bit flag. The permission is granted if the flag is set
to 1, otherwise it is set to 0.
Figure 3.2.1 shows an example of HS_ADMIN value that defines an
administrator for the naming authority handle "0.NA/10". In figure
3.2.1, a naming authority administrator is identified by an
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HS_ADMIN value assigned to the naming authority handle "0.NA/10".
The administrator can be authenticated based on the handle value
"0.NA/10":3, which is the handle value assigned to the naming
authority handle "0.NA/10" and has its index set to 3. The handle
value "0.NA/10":3 may contain the secret or public key used by the
administrator. The administrator is granted permission to add,
delete, or modify sub-naming authorities under "10", and add or
delete handles directly under the naming authority. The
administrator may also add, delete, or modify any handle values
assigned to the naming authority handle except those HS_ADMIN
values. In other words, the administrator is not allowed to add,
delete, or modify any administrators for the naming authority.
-------------------------------------------------------------
------------------------------------------------------------- |
------------------------------------------------------------- | |
| | | |
| <index>: 2 | | |
| <type>: HS_ADMIN | | |
| <data>: | | |
| <AdminRef>: "0.NA/10": 3 | | |
| <AdminPerm>: Add_NA, Delete_NA, | | |
| Add Handle, Delete_Handle, | | |
| Add_Value, Delete_Value, Modify_Value, | | |
| Authorized_Read, List_Handle, List_NA | | |
| | | |
| <TTL>: 24 hours | | |
| <permission>: PUBLIC_READ, ADMIN_WRITE | | |
| <reference>: {empty} | |-
| |-
-------------------------------------------------------------
Figure 3.2.1: Administrator for the naming authority
handle "0.NA/10"
HS_ADMIN values are used by handle servers to authenticate the
handle administrator before fulfilling any administrative requests.
The server authenticates a client by checking whether the client
has possession of the secret key (or the private key) that matches
the one in any of the handle administrator references. The
authentication is carried out via the handle system authentication
protocol as described later in this document.
HS_ADMIN values may require authentication for read access in order
to prevent public exposure of the data. Additionally, the handle
administrator reference that contains the administrator's secret
key should have neither PUBLIC_READ nor ADMIN_READ permission to
prevent the key from leaving the server.
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3.2.2 Service Site Information: HS_SITE
The Handle System consists of a single distributed global handle
service, also known as the Global Handle Registry (GHR), and
unlimited number of Local Handle Services (LHSs). Each handle
service, global or local, may be replicated into multiple service
sites. Each service site may consist of multiple server computers.
Service requests targeted at any handle service can be distributed
into different service sites, and into different server computers
within any service site. Such architecture assures that each handle
service could have the capacity to manage any large number of
handles and handle requests. It also provides ways for each handle
service to avoid any single point of failure.
Each handle service, global or local, may provide the same set of
functions for resolving and administering its collection of
handles. Handle services differ primarily in that each service is
responsible for a distinct set of handles. They are also likely to
differ in the selection, number, and configuration of their
components such as the servers used to provide handle resolution
and administration. Different handle services may be created and
managed by different organizations. Each of them may have their own
goals and policies.
A service site typically consists of a cluster of server computers
residing within a local Internet domain. These computers work
together to distribute the data storage and processing load at the
site. It is possible, although not recommended, to compose a site
from servers at widely different locations. Further, it is even
possible to compose two different sites from the same set of
servers.
Each service site is defined by an HS_SITE value. HS_SITE is a pre-
defined handle system data type. An HS_SITE value defines a service
site by identifying the server computers (e.g., IP addresses) that
comprise the site along with their service configurations (e.g.,
port numbers). HS_SITE values are typically assigned to naming
authority handles. The set of HS_SITE values assigned to a naming
authority handle is called the service information for the naming
authority.
The service information is managed by the naming authority
administrator. It must reflect the configuration of the handle
service for the naming authority. Note that an additional layer of
indirection, called a service handle, can be used to allow multiple
naming authorities to reference a single set of HS_SITE values, as
described later in this document (see section 3.2.3). Clients of
the Handle System depend on the service information to locate the
responsible handle server before they can send their service
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requests. The service information can also be used by clients to
authenticate any service response from the handle server.
An HS_SITE value is a handle value whose <type> field is HS_SITE
and whose <data> field consists of the following entries:
<Version>
A 2-byte value that identifies the version number of the HS_SITE.
The version number identifies the data format used by the HS_SITE
value. It is defined to allow backward compatibility over time.
This document defines the HS_SITE with version number 0.
<ProtocolVersion>
A 2-byte integer value that identifies the handle protocol
version. The higher byte of the value identifies the major
version and the lower byte the minor version. Details of the
handle system protocol is specified in [8].
<SerialNumber>
A 2-byte integer value that increases by 1 (and may wrap around
through 0) each time the HS_SITE value gets changed. It is used
in the handle system protocol to synchronize the HS_SITE values
between client and server.
<PrimaryMask>
An 8-bit mask that identifies the primary site(s) of the handle
service. The first bit of the octet is the <MultiPrimary> bit. It
indicates whether the handle service has multiple primary sites.
The second bit of the octet is the <PrimarySite> bit. It
indicates whether the HS_SITE value is a primary site. A primary
site is the one that supports administrative operations for its
handles. A <MultiPrimary> entry with zero value indicates that
the handle service has a single primary site and all handle
administration has to be done at that site. A non-zero
<MultiPrimary> entry indicates that the handle service has
multiple primary sites. Each primary site may be used to
administrate handles managed under the handle service. Handles
managed by such service may identify its primary sites using an
HS_PRIMARY value, as described in section 3.2.5.
<HashOption>
An 8-bit octet that identifies the hash option used by the
service site to distribute handles among its servers. Valid
options include HASH_BY_NA (0x00), HASH_BY_LOCAL (0x01), or
HASH_BY_HANDLE (0x02). These options indicate whether the hash
operation should only be applied to the naming authority portion
of the handle, or only the local name portion of the handle, or
the entire handle, respectively. The standard MD5 hashing
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algorithm [14] is used by each service site to distribute handles
among its servers.
<HashFilter>
An UTF8-string entry reserved for future use.
<AttributeList>
A 4-byte integer followed by a list of UTF8-string pairs. The
integer indicates the number of UTF8-string pairs that follow.
Each UTF8-string pair is an <attribute>:<value> pair. They are
used to add literal explanations of the service site. For
example, if the <attribute> is "Organization", the <value> should
contain a description of the organization hosting the service
site. Other <attribute>s may be defined to help distinguish the
service sites from each other.
<NumOfServer>
A 4-byte integer that defines the number of servers in the
service site. The entry is followed by a list of <ServerRecord>s.
Each <ServerRecord> defines a handle server that is part of the
service site. Each <ServerRecord> consists of the following data
fields:
<ServerRecord> ::= <ServerID>
<Address>
<PublicKeyRecord>
<ServiceInterface>
where each field is defined as follows:
<ServerID>
A 4-byte unsigned integer that uniquely identifies a server
process under the service site. <ServerID>s do not have to
begin with 1 and they don't have be consecutive numbers. They
are used to distinguish servers under a service site from
each other. Note that there can be multiple servers residing
on any given computer, each with a different <ServerID>.
<Address>
The 16-byte IPv6 [15, 16] address of the handle server. Any
IPv4 address should be presented as :::::FFFF:xxxx:xxxx
(where xxxx:xxxx can be any 4-byte IPv4 address).
<PublicKeyRecord>
A 4-byte integer followed by a byte-array that contains the
server's public key. The integer specifies the size of the
byte-array. The byte-array (for the publickey) consists of
three parts: a UTF8-string that describes the key type, a
two-byte option field reserved for future use, and a byte-
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array that contains the public key itself. For example, the
UTF8-String "DSA_PUB_KEY" indicates that the
<PublicKeyRecord> contains a DSA public key. The storage
format of the DSA key in the byte-array could then be found
from the handle "0.type/DSA_PUB_KEY". Public key in the
<PublicKeyRecord> can be used to authenticate any service
response from the handle server.
The <PublicKeyRecord> may also contain a X.509 certificate.
This happens if the key type field contains the UTF8-String
"CERT.X509". In this case, "CERT.X509" will map to the
handle "0.TYPE/CERT.X509". The handle may contain
information that describes the syntax and semantics of the
public key or its certificate. Additional key type may also
be registered (as handles under "0.TYPE") to further
distinguish different kind of X.509 certificates. For
example, "CERT.X509.DSA" may be used to denote X.509
certificates that contain DSA public keys. If the key type
field of a <PublicKeyRecord> declares "CERT.X509.DSA", the
<PublicKeyRecord> must contain a X.509 certificate with a
DSA public key in it."
<ServiceInterface> ::= <InterfaceCounter>
* [ <ServiceType>
<TransmissionProtocol>
<PortNumber> ]
A 4-byte integer followed by an array of triplets consisting
of <ServiceType, TransmissionProtocol, PortNumber>. The 4-
byte integer specifies the number of triplets. Each triplet
lists a service interface provided by the handle server. For
each triplet, the <ServiceType> is an octet (as a bit mask)
that specifies whether the interface is for handle resolution
(0x01), handle administration (0x02), or both. The
<TransmissionProtocol> is also an octet (as a bit mask) that
specifies the transmission protocol. Possible transmission
protocols include TCP (0x01), UDP (0x02), and HTTP (0x04).
The <PortNumber> is a 4-byte unsigned integer that specifies
the port number used by the interface. The default port
number is 2641.
Figure 3.2.2 shows an example of handle service site in terms of a
HS_SITE value. The HS_SITE value is assigned to the naming
authority handle "0.NA/10". The <PrimaryMask> indicates that it is
the only primary site of the handle service. The site consists of
three handle servers, as indicated in the <NumOfServer>. These
servers provide handle resolution and administration service for
every handle under the naming authority "10". The first server
record (ServerID 0) shows two service interfaces, one for handle
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resolution and the other for handle administration. Each interface
has its own port.
Each server within a service site is responsible for a subset of
handles managed by the handle service. Clients can find the
responsible server by performing a common hash-operation. The hash-
operation will first convert all ASCII characters in the handle
into upper-case. It then applies the MD5 hashing upon the portion
of the converted handle string (according to the <HashOption>
entry). The result is a 16-byte integer. The absolute value of the
integer will be divided by the number of servers (specified in the
<NumOfServer> entry). The remainder is the sequence number
(starting with zero) of the <ServerRecord> listed in the HS_SITE
value. From the <ServerRecord>, clients can find the IP address of
the handle server for their handle requests.
------------------------------------------------------------
------------------------------------------------------------ |
----------------------------------------------------------- | |
| | | |
| <index>: 2 | | |
| <type>: HS_SITE | | |
| <data>: | | |
| Version: 0 | | |
| ProtocolVersion: 2.1 | | |
| SerialNumber: 1 | | |
| PrimaryMask: | | |
| MultiPrimary: FALSE | | |
| PrimarySite: TRUE | | |
| HashOption: HASH_BY_HANDLE | | |
| HashFilter: {empty UTF8-String} | | |
| AttributeList: 0 {followed by no attributes} | | |
| NumOfServer: 3 | | |
| {followed by a list of <ServerRecord>} | | |
| | | |
| ----------------------------------------- | | |
| ------------------------------------------ | | | |
| ------------------------------------------ || | | |
| | ServerID: 1 ||| | | |
| | Address: :FFFF:132.151.1.155 ||| | | |
| | PublicKeyRecord: HS_DSAKEY, iQCuR2R... ||| | | |
| | ServiceInterface ||| | | |
| | ServiceType: Resolution_Only ||| | | |
| | TransmissionProtocol: TCP & UDP ||| | | |
| | PortNumber: 2641 ||| | | |
| | ||| | | |
| | ServiceType: Admin only ||| | | |
| | TransmissionProtocol: TCP || | | |
| | PortNumber: 2642 | | | |
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| ------------------------------------------ | | |
| | | |
| <TTL>: 24 hours | | |
| <permission>: PUBLIC_READ, ADMIN_WRITE | | |
| <reference>: {empty} | |-
| |-
-----------------------------------------------------------
Fig. 3.2.2: The primary service site for the naming authority "10"
3.2.3 Naming Authority Delegation Service: HS_NA_DELEGATE
The HS_NA_DELEGATE is a pre-defined handle system data type. It has
the exact same format as the HS_SITE value. Like HS_SITE values,
HS_NA_DELEGATE values are used to describe service sites of a LHS.
HS_NA_DELEGATE values may be assigned to naming authority handles
to designate naming authority administration to a LHS. A naming
authority handle with a set of HS_NA_DELEGATE values indicates that
all child naming authorities of the naming authority are managed by
the LHS described by the HS_NA_DELEGATE values.
For example, suppose the naming authority "foo.bar" decides to have
its child naming authorities delegated to a LHS. To achieve this,
one may assign the naming authority handle "0.NA/foo.bar" with a
set of HS_NA_DELEGATE values that describes the LHS. The set of
HS_NA_DELEGATE values indicate that the service information of any
child naming authority of the "foo.bar", such as "foo.bar.baz", can
be found by querying the naming authority handle "0.NA/foo.bar.baz"
from the LHS.
3.2.4 Service Handle: HS_SERV
Any handle service, global or local, can be defined in terms of a
set of HS_SITE values. These HS_SITE values may be assigned
directly to the relevant naming authority handle, or an additional
level of indirection may be introduced through the use of service
handles. A service handle may be thought of as a name for a handle
service. It may be used to maintain the HS_SITE values for the
handle service and referenced from a naming authority handle via a
HS_SERV value. A HS_SERV value is a handle value whose <type> field
is HS_SERV and whose <data> field contains the reference to the
service handle. HS_SERV values are typically assigned to naming
authority handles to refer clients to the responsible handle
service.
Use of service handle allows sharing of service information among
multiple naming authorities. It also allows changes to service
configuration (e.g., adding a new site) to be made in one place
rather than in every naming authority handle involved. The
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mechanism may also be used to support service referral from one
handle service to another for whatever reason.
A naming authority handle may have no more than one HS_SERV value
assigned to it, otherwise it is an error. If a naming authority
handle has both a list of HS_SITE values and an HS_SERV value, the
HS_SITE values should be used as the service information for the
naming authority.
Service handles can be registered under the reserved naming
authority "0.SERV". Handles under "0.SERV" are managed by the GHR.
For example, the service handle "0.SERV/123" may be created to
maintain the service information for the handle service that
manages handles under the naming authority "123" and any of its
sub-naming authorities. Similarly, a service handle "0.SERV/a.b.c"
may be created to host the service information for the handle
service that manages handles under the naming authority "a.b.c".
The use of service handles raises several special considerations.
Multiple levels of service handle redirection should be avoided due
to their lack of efficiency, but are not signaled as an error.
Looped reference of service handles or HS_SERV values that point to
non-existent service handles should be caught and error conditions
passed back to the user.
3.2.5 Alias Handle: HS_ALIAS
In practice, it is very possible that a digital object may have
multiple names that will identify the object. The Handle System
supports such feature via the pre-defined data type HS_ALIAS. A
HS_ALIAS value is a handle value whose <type> field is HS_ALIAS and
whose <data> field contains a reference to another handle. A handle
with a HS_ALIAS value is an alias handle to the handle referenced
in the HS_ALIAS value. A alias handle should not have any
additional handle values other than HS_ALIAS or HS_ADMIN (for
administration) values. This is necessary to prevent any
inconsistency between a handle and its aliases.
During a handle resolution, a client may get back an HS_ALIAS
value. This indicates that the handle in question is an alias
handle. The client may then retry the query against the handle
specified in the HS_ALIAS value until final results are obtained.
The use of alias handle introduces a number of special
considerations. For example, multiple levels of aliases should be
avoided for the sake of efficiency, but are not signaled as an
error. Alias loops and aliases that point to non-existent handles
should be caught and error conditions passed back to the user.
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One potential use of alias handle would be to support the transfer
of ownership of any named resource. When a resource identified by a
handle transfers from one organization to another, a new handle for
the resource may be created. To avoid inconsistency and any broken
reference, the handle used before the ownership transfer may be
changed into an alias handle and has its HS_ALIAS value pointing to
the newly created handle.
3.2.6 Primary Site: HS_PRIMARY
HS_PRIMARY is a pre-defined data type used to designate the primary
service sites for any given handle. A handle service with multiple
primary service sites is called a multi-primary service. Otherwise
it is called a single-primary service. Each handle managed by a
multi-primary handle service may specify its primary service sites
in terms of a HS_PRIMARY value. A HS_PRIMARY value is a handle
value whose <type> field is HS_PRIMARY and whose <data> field
contains a list of references to HS_SITE values. Each of these
HS_SITE defines a primary service site for the handle.
There can be at most one HS_PRIMARY value assigned to each handle.
Otherwise it is an error. A handle with no HS_PRIMARY value but
managed by a multi-primary handle service is not an error. In this
case, every primary service site of the handle service will also be
the primary site for the handle. Handles managed by a single-
primary handle service do not need any HS_PRIMARY values and any
such values should be ignored.
3.2.7 Handle Value List: HS_VLIST
HS_VLIST is a pre-defined data type that allows a handle value to
be used as a reference to a list of other handle values. An
HS_VLIST value is a handle value whose <type> is HS_VLIST and whose
<data> consists of a 4-byte unsigned integer followed by a list of
references to other handle values. The integer specifies the number
of references in the list. The references may refer to handle
values under the same handle or handle values from any other
handles. Each reference is encoded as an UTF8-string followed by a
4-byte unsigned integer that identifies the referenced handle and
its value index.
HS_VLIST values may be used to define administrator groups for
handles. In this case, each reference in the HS_VLIST defines a
member of the administrator group and the HS_VLIST value identifies
the group as a whole. Client software must be careful, however, to
avoid cyclic definition of value references.
4. Handle System Service Model
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The Handle System is a distributed global name service. It consists
of a single distributed Global Handle Registry (GHR) and unlimited
number of Local Handle Services (LHS). These service components
provide the name service (both resolution and administration) on
behalf of handle system client components. Handle system client
components may also choose to use handle system middle-ware
components (e.g., the handle system caching service) for
efficiency. This section describes these components and their
relationships to each other.
4.1 Handle System Service Components
The Handle System defines a hierarchical service model. At the top
level is the single distributed global handle service, also known
as the Global Handle Registry (GHR). Underneath the GHR, there can
be any number of Local Handle Services (LHSs). Each LHS must be
registered with the GHR to manage handles under a distinct set of
naming authorities. Naming authorities are managed by the GHR via
naming authority handles (i.e., handles under the naming authority
"0.NA"). A naming authority handle can also be used to locate the
service information (in terms of HS_SITE values) that describes the
handle service responsible for handles under the naming authority.
From the service information, clients can choose a service site and
locate the responsible server for their handle requests.
Handle system service components are scalable and extensible to
accommodate any large amount of service load. A handle service,
global or local, may consist of multiple service sites, replicating
each other. Each service site may also consist of a cluster of
computers working together to serve its respective namespace.
Having multiple service sites avoids any single point of failure
and allows load balancing among these service sites. Using multiple
servers at any service site distributes the service load into
multiple server processes and allows less powerful computers to be
utilized for the name service.
4.1.1 Global Handle Registry (GHR)
The Global Handle Registry (GHR) is mainly used to manage naming
authority handles and to provide service information for every
naming authority under the Handle System. The GHR may also be used
to manage and provide resolution and administration service to non-
naming-authority handles. Unlike any LHS, which mostly manages
handles under a few naming authorities, the GHR is primarily used
to register naming authorities and provide service information for
every LHS. In other words, the GHR is the single root service that
registers every LHS and provides their service information via the
use of naming authority handle(s). Every naming authority under the
Handle System must be registered under the GHR as a naming
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authority handle. The naming authority handle provides the service
information of the handle service that manages all the handles
under the naming authority. The service information may be provided
in terms of a set of HS_SITE values, or a HS_SERV value that refers
to a service handle, as described earlier.
The GHR may consist of multiple service sites, each described in a
HS_SITE value. These HS_SITE values are assigned to the designated
naming authority handle "0.NA/0.NA", also called the root handle.
The root handle is the naming authority handle that maintains the
service information for GHR. Top level naming authorities can only
be created by administrators of the root handle.
In order to communicate with the GHR, client software needs the GHR
service information beforehand. The service information may be
distributed initially with the client software, or obtained from
some other secure sources (e.g., postal mail, secure web site,
etc.). Client software may keep the service information to
communicate with the GHR until the service information becomes
expired (according to its TTL). The GHR must update its service
information (assigned to the root handle) every time it changes its
configuration. Client software with out-dated service information
will be notified of the update every time it communicates with the
GHR. The GHR must be maintained in such a way that any client
software with out-dated GHR service information can still query the
root handle for the latest update.
Fig. 4.1.1 shows the GHR service information in terms of a set of
HS_SITE values. The GHR may consist of a number of service sites,
each described in a HS_SITE value. The figure shows a GHR service
site located in US East Coast, as indicated in the <AttributeList>.
------------------------------------------------------------
------------------------------------------------------------ |
----------------------------------------------------------- | |
| | | |
| <index>: 3 | | |
| <type>: HS_SITE | | |
| <data>: | | |
| Version: 1 | | |
| ProtocolVersion: 2.1 | | |
| SerialNumber: 1 | | |
| PrimaryMask: | | |
| MultiPrimary: TRUE | | |
| PrimarySite: TRUE | | |
| HashOption: HASH_BY_HANDLE | | |
| HashFilter: {empty UTF8-String} | | |
| AttributeList: 1 | | |
| Description: Service site at US East Coast | | |
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| NumOfServer: 3 | | |
| | | |
| ------------------------------------------ | | |
| ------------------------------------------ | | | |
| ------------------------------------------ || | | |
| | ServerID: 1 ||| | | |
| | Address: :FFFF:132.151.2.150 ||| | | |
| | PublicKeyRecord: HS_DSAKEY, iQCuR2Rnw... ||| | | |
| | ServiceInterface ||| | | |
| | ServiceType: Resolution & Admin ||| | | |
| | TransmissionProtocol: TCP & UDP || | | |
| | PortNumber: 2641 | | | |
| ------------------------------------------ | | |
| | | |
| <TTL>: 24 hours | | |
| <permission>: PUBLIC_READ, ADMIN_WRITE | | |
| <reference>: {empty} | |-
| |-
-----------------------------------------------------------
Figure 4.1.1: GHR service information
The GHR and its service information provide an entry point for any
client software to communicate with the Handle System. For any
given handle, client software can query the GHR for its naming
authority handle. This will return the service information of the
LHS that manages every handle under the naming authority. The
service information will direct the client software to the handle
server within the LHS that manages the handle.
4.1.2 Local Handle Service (LHS)
A Local Handle Services (LHS) manages handles under given sets of
naming authorities. Each naming authority defines a "local"
namespace that consists of all of the handles under the naming
authority. Note that a LHS is not a "local" service in terms of any
network topology. It is called a "Local" Handle Service because it
typically manages a restricted (local) namespace.
A naming authority is "homed" at a LHS if all handles under the
naming authority are managed by the LHS. A LHS may be home to
multiple naming authorities. On the other hand, a naming authority
may only be "homed" at one LHS. Note that a naming authority may
also be homed at the GHR.
------------------------------------------------------------
------------------------------------------------------------ |
----------------------------------------------------------- | |
| | | |
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| <index>: 3 | | |
| <type>: HS_SITE | | |
| <data>: | | |
| Version: 1 | | |
| ProtocolVersion: 2.1 | | |
| SerialNumber: 1 | | |
| PrimaryMask: | | |
| MultiPrimary: FALSE | | |
| PrimarySite: TRUE | | |
| HashOption: HASH_BY_LOCALNAME | | |
| HashFilter: {empty UTF8-String} | | |
| AttributeList: 1 | | |
| Description: Local Service for "10" | | |
| NumOfServer: 2 | | |
| | | |
| ----------------------------------------- | | |
| ----------------------------------------- | | | |
| | ServerID: 1 || | | |
| | Address: :FFFF:132.151.3.150 || | | |
| | PublicKeyRecord: HS_DSAKEY, iQCuR2R... || | | |
| | ServiceInteface: || | | |
| | ServiceType: Resolution & Admin || | | |
| | TransmissionProtocol: TCP & UDP || | | |
| | PortNumber: 2641 |' | | |
| -----------------------------------------' | | |
| | | |
| <TTL>: 24 hours | | |
| <permission>: PUBLIC_READ, ADMIN_WRITE | |-
| <reference>: {empty} |-
-----------------------------------------------------------
Figure 4.1.2: LHS service information
Like the GHR, a LHS may also consist of many service sites with
each site described by an HS_SITE value. The set of HS_SITE values
for any LHS may be assigned to a service handle or to the relevant
naming authority handle(s). Fig. 4.1.2 shows an example of HS_SITE
values for a LHS. These HS_SITE values are assigned to the naming
authority handle "0.NA/10". This suggests that the naming authority
"10" is "homed" at the LHS specified in these HS_SITE values.
Clients may query the GHR to obtain the service information in
order to communicate with the LHS. Administrators of the naming
authority handle are responsible for maintaining the service
information and keeping it up to date.
Note that a LHS may refer its clients to another LHS in response to
a service request. This allows the LHS to further distribute its
service in a hierarchical fashion.
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4.2 Handle System Middle-Ware Components
Handle system middle-ware components currently include handle
system caching servers and handle system proxy servers. These
handle system middle-ware components are clients to handle system
service components, but servers to handle system client software.
Handle system middle-ware components are used to provide additional
interfaces to the basic handle service. For example, a handle
system caching server may be used to share resolution results
within a local community. Additionally, a handle system proxy
server can be used to bypass any organizational firewall via HTTP
tunneling.
4.2.1 Handle System Caching Service
Handle system caching service can be used to reduce the network
traffic between handle system clients and servers. Caching handle
data, including the service information of any LHS, allows re-use
of information obtained from earlier queries.
Each handle value contains a <TTL> (Time to Live) field that tells
a caching service how long the cached value may be regarded as
valid. A zero-value TTL indicates that the value can only be used
for the transaction in progress and should not be cached. A caching
service may obtain its data directly from a handle service, or from
another caching service that eventually gets its data from the
handle service.
A caching service may be defined in terms of an HS_SITE value and
may consist of multiple caching servers. For any given handle,
clients can find the responsible caching server within the caching
service by using the same hashing algorithm as used in locating the
handle server within any handle service.
Caching services are not part of any handle system administration
or authentication hierarchy. The handle system protocol does not
authenticate any response from a caching service. Clients are
responsible to set up their trust relationship with the caching
service that they select. They will also rely on the caching
service to properly authenticate any response from any handle
server.
4.2.2 Handle System Proxy Server
Handle system proxy servers can be used to enable handle resolution
via other Internet protocols. For example, CNRI has built and made
available a Handle System HTTP Proxy Server that will process any
handle resolution in terms of HTTP protocol. The current DNS
address for the proxy server is at "hdl.handle.net". The proxy
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server allows any handle to be resolved via a HTTP URL. The URL can
be constructed as "http://hdl.handle.net/<handle>", where <handle>
can be any handle from the Handle System. For example, the handle
"ncstrl.vatech_cs/tr-93-35" can be resolved via the HTTP URL
"http://hdl.handle.net/ncstrl.vatech_cs/tr-93-35" from any web
browser. In this case, the URL is sent to the proxy server in terms
of a HTTP request. The proxy server will query the Handle System
for the handle data and return the results in terms of HTTP
response.
Using HTTP URLs allows handles to be resolved from standard web
browsers without any additional client software. However, such
reference to the handle also ties itself to the proxy server. If
the proxy server changes its DNS name or otherwise becomes invalid,
the reference (i.e. the HTTP URL) to the handle will break. Thus
the selection or use of proxy server should be carefully evaluated.
Proxy servers are not part of any handle system administration or
authentication hierarchy. The handle system protocol does not
authenticate any response from a proxy server. Clients are
responsible to set up their trust relationship with the proxy
server that they select. They will also rely on the proxy server to
properly authenticate any response from any handle server.
4.3 Handle System Client Components
Handle system client components are client software that
communicates with the handle system service components. Client
software may speak the handle system protocol and send its request
directly to a service component. The response from the service
component may be the final answer to the request, or a referral to
another service component. The client software will have to follow
the referral in order to complete the transaction.
Client software may also be configured to tunnel its request via a
middle-ware component. The middle-ware component will thus be
responsible for obtaining the final result and returning it to the
client. Unlike service components, middle-ware components will only
return final results of client's request. No service referral will
be returned from middle-ware components.
Various handle system client components may be developed for
various applications. The CNRI Handle System Resolver [17] is one
such component. The resolver extends web browsers (e.g. Netscape or
Microsoft Internet Explorer) in such a way that handles can be
resolved directly in terms of "hdl:" Uniform Resource Identifiers
(URIs). The Grail web browser [18], a freely downloadable software
developed in Python [19], also supports the "hdl:" URI scheme and
will resolve handles accordingly. For example, the handle
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"10.1045/july95-arms" may be resolved by entering its handle URI as
"hdl:10.1045/july95-arms" into any of these resolver-enabled
browsers. Details of the handle URI syntax will be specified in a
separate document.
5. Handle System Operation Model
Handle System operations can be categorized into resolution and
administration. Clients use the handle resolution service to query
for any handle values. Handle administration allows clients to
manage handles, including adding and deleting handles, and updating
their values. It also deals with naming authority administration
via naming authority handles. This section explains how various
handle system components work together to accomplish these service
operations.
Both resolution and administration may require authentication of
the client. The authentication can be done via the handle system
authentication protocol described later in this section. Whether
authentication is required or not depends on the kind of operation
involved and the permissions assigned to the relevant handle value,
and policies deployed by the relevant service components.
The handle system protocol specifies the syntax and semantics of
each message exchanged between handle system clients and its server
components. This section provides a high level overview of the
protocol used to accomplish any service operation. The exact
programmatic detail of each message (i.e. their byte layout or
syntax) is specified in a separate document [8].
5.1 Handle System Service Request and Response
The Handle System provides its service in response to client
requests. A client may send a request to any handle server to
provoke a response. The response either provides an answer to the
request, or a status code with associated information that either
refers the request to another service component, asks for client
authentication, or signals some error status.
Each handle under the Handle System is managed by its home service.
The naming authority handle provides the service information (in
terms of HS_SERV or HS_SITE values) of the handle service that
manages all handles under the naming authority. Any handle request
must be directed to the home service of the handle in question.
Clients may find the home service by querying the corresponding
naming authority handle against the GHR. Alternatively, this
information may be found in a local cache or even be part of a
local client configuration. Given the service information, clients
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may select a service site and locate the responsible handle server
within the site.
To resolve the handle "ncstrl.vatech_cs/te-93-35", for example,
client software needs to know the home service for the naming
authority "ncstrl.vatech_cs". The home service can be obtained by
querying the naming authority handle "0.NA/ncstrl.vatech_cs"
against the GHR. The GHR will return the service information in
terms of the HS_SITE values assigned to the naming authority
handle. From the service information, clients can pick a service
site, find the responsible handle server within the site, and send
the resolution request to the handle server.
Clients may require digital signatures from a handle server in
order to authenticate any response from the server. The signature
can be generated using the server's private key. Clients may verify
the signature using the public key available from the service
information (refer to the <PublicKeyRecord> entry discussed in
3.2.2).
A communication session may also be established between any client
and handle server. Each session is identified by a unique session
ID managed by the server. A session may be used to manage requests
that require multiple interactions. It may also be used to share
any TCP connection or authentication information among multiple
service transactions. Each session may establish a session key and
use it to authenticate any message exchanged within the session. It
may also be used to encrypt any message between the client and the
server to achieve data confidentiality.
The following diagram shows a handle resolution process in terms of
messages exchanged between client software and handle system
service components. In this case, the client is trying to resolve
the handle "ncstrl.vatech_cs/tr-93-35". It assumes that the client
has yet obtained the service information of the LHS "homed" by the
naming authority "ncstrl.vatech.cs". The client has to get the
service information from the naming authority handle managed by the
GHR. The service information allows the client to locate the
responsible LHS and query for the handle value.
[HS Client] ----------------------------> [Global Handle Registry]
1. ask for the service
information from the
naming authority handle
"0.NA/ncstrl.vatech_cs"
[HS Client] <---------------------------- [Global Handle Registry]
2. service information for
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the naming authority
"ncstrl.vatech_cs"
[HS Client] ----------------------------> [Local Handle Service]
3. query the handle
"ncstrl.vatech_cs/tr-93-35"
against the responsible
handle server
... ...
(optional client authentication, depending on the service request)
... ...
[HS Client] <---------------------------- [Local Handle Service]
4. query result from the handle
server + (optional) server
signature
Figure 5.1: Handle resolution example
In Figure 5.1, the client is configured to communicate with the GHR
for any handle service. In this case, the client first queries the
GHR to find the home service for the handle's naming authority. The
GHR returns the service information of the LHS that manages every
handle under the naming authority. From the service information,
the client can find the responsible handle server and query the
server for the handle. The server may set up a session to
authenticate the client if any of the handle value requires
authentication. Otherwise, the server will simply return the handle
value to the client. The server may send a digital signature as
part of its response if required by the client.
The above procedure assumes that the client software already has
the GHR service information. That information was likely obtained
from the client software distribution. The GHR will notify the
client software if it learns that the service information used by
the client software is out of date. Client software may retrieve
the latest service information from the root handle "0.NA/0.NA".
The root handle also maintains the public key that may be used to
authenticate the service information.
Note that a client may cache the service information of any naming
authority so that subsequent queries for handles under the same
naming authority may reuse the service information and bypass the
first two steps shown in Figure 5.1. Client software may also be
configured to query a caching or proxy server directly for any
handle. In this case, the caching or proxy server will act as the
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[HS Client] in Figure 5.1 before returning the query result to the
client.
Client software under certain organization may also elect to bypass
the GHR and communicate directly with a LHS managed by the
organization. Doing so may achieve quicker response for handles
managed under the LHS. The client software will be referred to the
GHR for handles not managed by the LHS.
5.2 Handle System Authentication Protocol
The Handle System supports handle administration over the public
Internet. Access controls can be defined on each handle value. The
handle system authentication protocol is the protocol used by any
handle server to authenticate handle administrator upon any
administration request. The authentication is also necessary when
clients query for handle values that are read-only by the handle
administrator. Handle administration include adding, deleting or
modifying handle values, and adding or deleting handles. Naming
authority administrations are carried out as handle administrations
over the corresponding naming authority handles.
The handle system authentication protocol does not perform any
server authentication. However, a client may authenticate any
server response by asking the server to sign its response with
digital signature.
By default, the Handle System authenticates clients via a
challenge-response protocol. That is, after receiving a client's
request, the server issues a challenge to the client if
authentication is necessary. To be authenticated as the
administrator, the client has to return a challenge-response, a
message that demonstrates procession of the administrator's secret.
The secret may be the private key or the secret key of the
administrator. This challenge-response allows the server to
authenticate the client as the handle administrator. Upon
successful authentication, the server will fulfill the client's
request if the administrator is given sufficient permission.
For example, suppose a client sends a request to the handle server
to add a new handle value. The server will issue a challenge to the
client in order to authenticate the client as one of the handle
administrators. If the client possesses the private key of the
administrator, she can use it to sign the server's challenge and
return the signature as part of her challenge-response. The server
will validate the signature in order to authenticate the client.
The client will be notified if the validation fails. Otherwise, the
server will further check if the administrator has the permission
to add the handle value. If so, the server will add the handle
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value and report success to the client. Otherwise, a permission-
denied message will be returned.
The following diagram shows a typical authentication process in
terms of the messages exchanged between the client and the handle
server.
[Client] --------------------------------> [Handle Server]
1. client request
+ (optional) client credential
[Client] <-------------------------------- [Handle Server]
2. server's challenge to client
+ (i.e., nonce + MD5 of client request)
[Client] -------------------------------> [Handle Server]
3. reference to handle administrator
+ challenge-response from client
[Client] <------------------------------- [Handle Server]
4. server acknowledgement
Figure 5.2: Handle system authentication process
In Figure 5.2, the client sends an administration request to the
handle server (along with optional credential discussed later). The
server decides that client authentication is required and issues a
challenge to the client. The client identifies itself as a handle
administrator and returns the challenge-response to the server. The
server authenticates the client as the administrator based on the
challenge-response. It also checks to see if the administrator is
authorized for the administration request. If so, the server will
fulfill the request and acknowledge the client.
Handle servers must authenticate the client before fulfilling any
request that requires administrator privilege. The exact
authentication process varies depending on whether public key or
secret key is used by the administrator. It also depends on whether
the handle used to store the administrator's key is managed by the
same handle server or not.
When public key is used, the challenge-response from the client
contains its digital signature over the server's challenge. The
server can authenticate the client by verifying the digital
signature based on the administrator's public key. If secret key is
used, the challenge-response from the client carries the Message
Authenticate Code (MAC) generated using the secret key. The server
may authenticate the client by generating the same MAC using the
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administrator's secret key and comparing it against the challenge-
response.
The reference to handle administrator in Fig 5.2 is also called a
key-reference. It refers to a handle value that contains the key
used by the administrator. If the key-reference is managed by the
same handle server (e.g., a handle value assigned to the same
handle), the server may use the key directly to do the
authentication. If the key-reference is managed by some other
handle server (whether or not within the same handle service), the
server will have to send a verification-request to this other
handle server, call it the key-server, in order to authenticate the
client. The verification-request to the key-server carries both the
server's challenge and the client's challenge-response. The key-
server will return a verification-response, signed using the key-
server's private key. The content of the verification-response will
depend on the handle value referenced by the key-reference. If the
key-reference refers to a public key used by the administrator, the
verification-response will contain the public key of the
administrator. Otherwise, the key-server will verify the challenge-
response on behalf of the requesting server and return the result
in the verification-response. The following diagram shows the
control flow of the authentication process where the key-reference
refers to a handle value that contains the administrator's public
(or secret) key and the key-server is some other handle server.
-------- -------------
| | 1. client request. | |
| | -------------------------------> | |
| | | |
| | 2. session ID | |
| | + server's challenge | |
| Handle | <------------------------------- | Handle |
| system | | server |
| client | 3. session ID | receiving |
| | + response to the challenge | client |
| | + administrator reference | request |
| | --------------------------------> | |
| | | |
| | 6. server acknowledgement | |
| | <------------------------------- | |
-------- -------------
| ^
4. Verification | | 5. verifi-
request | | cation
| | response
| | (signed)
V |
--------------------------
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| The handle server (the |
| key-server) that manages |
| the key referenced by |
| the key-reference |
--------------------------
Figure 5.3: Authentication process requiring verification
from a second handle server
Secret key based authentication via a second handle server, i.e.,
the key server, provides a convenient way to share a common secret
key (e.g. pass phrase) among handles managed by different handle
servers. However, it should not be used to manage highly sensitive
handles or handle data. The authentication process itself is
expensive and relies on a third party, i.e., the key-server, for
proper operation. Additionally, the secret key itself is subject to
dictionary attack since the key-server cannot determine whether the
verification-request comes from a legitimate handle server. A
handle service may set its local policy so that secret key based
authentication can only be carried out if the handle server
(receiving the client request) is also the key-server.
Local handle services may define additional local policies for
authentication and/or authorization. Handle system service
components may also choose to use other Internet authentication
mechanisms such as Kerberos [20] or some Transport Layer Security
protocol [21]. Details of these will be addressed in a separate
document.
6. Security Considerations
Handle System security considerations are discussed in the "Handle
System Overview" [1] and that discussion applies equally to this
document.
The Handle System delegates handle administration to each handle
administrator who may or may not be the server administrator.
Handle administrators are allowed to choose their own public/secret
keys used for authentication. The security of handle system
authentication depends on the proper key selection and its
maintenance by the handle administrator. Handle administrators must
choose and protect their authentication keys carefully in order to
protect the handle data. Handle server implementations may deploy
policies that regulate the selection of public/secret keys used for
authentication. For example, a handle server may require that any
authentication key must be no less than certain number of bits. It
may also prohibit the use of secret keys because of the potential
dictionary attack.
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The handle system data model supports execution permission
(PUBLIC_EXECUTE, ADMIN_EXECUTE) for each handle value. While this
allows better sharing of network resources, it also raises many
security considerations. Execution privilege should be restricted
within the permissions of certain user account (corresponding to
the handle administrator) on the server to prevent system-wide
disruption. Switching between computing platforms for the server
should also be careful to avoid any unexpected behavior.
Implementations may choose not to support the execution permission,
or provide options so that it can be disabled.
To protect against any irresponsible use of system resource, handle
servers may implement quota control. The quota control can be used
to put limits on the number of handles under a naming authority,
the number of handle values allowed for any given handle, the
maximum size of any handle value, and the number of sub-naming
authorities under a naming authority. Handle servers must report
error if the result of a handle administration violates any of
these limits.
References and Bibliography
[1] S. Sun, L. Lannom, "Handle System Overview", IETF draft, work
in progress.
[2] P. Mockapetris, "DOMAIN NAMES - CONCEPTS AND FACILITIES",
RFC1034
[3] P. Mockapetris, "DOMAIN NAMES - IMPLEMENTATION AND
SPECIFICATION", RFC1035
[4] M. Wahl, T. Howes, and S. Kille, "Lightweight Directory Access
Protocol (v3)", RFC 2251
[5] D. Crocker, Ed., P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234
[6] F. Yergeau, "UTF-8, A Transform Format for Unicode and
ISO10646", RFC2044
[7] The Unicode Consortium, "The Unicode Standard, Version 2.0",
Addison-Wesley Developers Press, 1996. ISBN 0-201-48345-9
[8] S. Sun, S. Reilly, L. Lannom, "Handle System Protocol
Specification", IETF draft, work in progress.
[9] T. Berners-Lee, L. Masinter, M. McCahill, et al., "Uniform
Resource Locators (URL)", RFC1738
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[10] R. Housley, W. Polk, W. Ford, D. Solo, "Internet X.509 Public
Key Infrastructure - Certificate and Certificate Revocation List
(CRL) Profile", RFC 3280
[11] Federal Information Processing Standards Publication (FIPS
PUB) 46-1, Data Encryption Standard, Reaffirmed 1988 January 22
(supersedes FIPS PUB 46, 1977 January 15).
[12] Federal Information Processing Standards Publication (FIPS
PUB) 81, DES Modes of Operation, 1980 December 2.
[13] D. Balenson, "Privacy Enhancement for Internet Electronic
Mail: Part III: Algorithms, Modes, and Identifiers", RFC 1423,
February 1993
[14] R. Rivest, " The MD5 Message-Digest Algorithm", RFC 1321
[15] S. Deering, R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 1883
[16] R. Hinden, S. Deering, "IP Version 6 Addressing Architecture",
RFC2373
[17] CNRI Handle System Resolver, http://www.handle.net/resolver
[18] Grail browser home page, http://grail.cnri.reston.va.us/grail/
[19] Python language website, http://www.python.org/
[20] J. Kohl, and C. Neuman, "The Kerberos Network Authentication
Service (V5)", RFC1510
[21] T. Dierks, C. Allen, "The TLS Protocol Version 1.0", RFC2246
[22] R. Kahn, R. Wilensky, "A Framework for Distributed Digital
Object Services, May 1995, http://www.cnri.reston.va.us/k-w.html
[23] American National Standards Institute. ANSI X9.52-1998,
Triple Data Encryption Algorithm Modes of Operation. 1998.
Author's Addresses
Sam X. Sun
Corporation for National Research Initiatives (CNRI)
1895 Preston White Dr. Suite 100
Reston, VA 20191
Phone: 703-262-5316
Email: ssun@cnri.reston.va.us
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Sean Reilly
Corporation for National Research Initiatives (CNRI)
1895 Preston White Dr. Suite 100
Reston, VA 20191
Phone: 703-620-8990
Email: sreilly@cnri.reston.va.us
Larry Lannom
Corporation for National Research Initiatives (CNRI)
1895 Preston White Dr. Suite 100
Reston, VA 20191
Phone: 703-620-8990
Email: llannom@cnri.reston.va.us
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