RFC 3652
Handle System Protocol (ver 2.1) Specification
Pages: 53
Informational
Informational
Part 1 of 2 – Pages 1 to 23
Network Working Group S. Sun Request for Comments: 3652 S. Reilly Category: Informational L. Lannom J. Petrone CNRI November 2003 Handle System Protocol (ver 2.1) Specification Status of this Memo This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. IESG Note Several groups within the IETF and IRTF have discussed the Handle System and its relationship to existing systems of identifiers. The IESG wishes to point out that these discussions have not resulted in IETF consensus on the described Handle System, nor on how it might fit into the IETF architecture for identifiers. Though there has been discussion of handles as a form of URI, specifically as a URN, these documents describe an alternate view of how namespaces and identifiers might work on the Internet and include characterizations of existing systems which may not match the IETF consensus view.Abstract
The Handle System is a general-purpose global name service that allows secured name resolution and administration over the public Internet. This document describes the protocol used for client software to access the Handle System for both handle resolution and administration. The protocol specifies the procedure for a client software to locate the responsible handle server of any given handle. It also defines the messages exchanged between the client and server for any handle operation.
Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Protocol Elements. . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Conventions. . . . . . . . . . . . . . . . . . . . . . . 4 2.1.1. Data Transmission Order. . . . . . . . . . . . . 4 2.1.2. Transport Layer. . . . . . . . . . . . . . . . . 5 2.1.3. Character Case . . . . . . . . . . . . . . . . . 6 2.1.4. Standard String Type: UTF8-String. . . . . . . . 7 2.2. Common Elements. . . . . . . . . . . . . . . . . . . . . 7 2.2.1. Message Envelope . . . . . . . . . . . . . . . . 8 2.2.2. Message Header . . . . . . . . . . . . . . . . . 11 2.2.3. Message Body . . . . . . . . . . . . . . . . . . 17 2.2.4. Message Credential . . . . . . . . . . . . . . . 18 2.3. Message Transmission . . . . . . . . . . . . . . . . . . 20 3. Handle Protocol Operations . . . . . . . . . . . . . . . . . . 21 3.1. Client Bootstrapping . . . . . . . . . . . . . . . . . . 21 3.1.1. Global Handle Registry and its Service Information. . . . . . . . . . . . . . . . . . . 21 3.1.2. Locating the Handle System Service Component . . 22 3.1.3. Selecting the Responsible Server . . . . . . . . 23 3.2. Query Operation. . . . . . . . . . . . . . . . . . . . . 23 3.2.1. Query Request. . . . . . . . . . . . . . . . . . 24 3.2.2. Successful Query Response. . . . . . . . . . . . 25 3.2.3. Unsuccessful Query Response. . . . . . . . . . . 26 3.3. Error Response from Server . . . . . . . . . . . . . . . 26 3.4. Service Referral . . . . . . . . . . . . . . . . . . . . 27 3.5. Client Authentication. . . . . . . . . . . . . . . . . . 28 3.5.1. Challenge from Server to Client. . . . . . . . . 29 3.5.2. Challenge-Response from Client to Server . . . . 30 3.5.3. Challenge-Response Verification-Request. . . . . 33 3.5.4. Challenge-Response Verification-Response . . . . 33 3.6. Handle Administration. . . . . . . . . . . . . . . . . . 34 3.6.1. Add Handle Value(s). . . . . . . . . . . . . . . 34 3.6.2. Remove Handle Value(s) . . . . . . . . . . . . . 35 3.6.3. Modify Handle Value(s) . . . . . . . . . . . . . 36 3.6.4. Create Handle. . . . . . . . . . . . . . . . . . 37 3.6.5. Delete Handle. . . . . . . . . . . . . . . . . . 39 3.7. Naming Authority (NA) Administration . . . . . . . . . . 40 3.7.1. List Handle(s) under a Naming Authority. . . . . 40 3.7.2. List Sub-Naming Authorities under a Naming Authority. . . . . . . . . . . . . . . . . . . . 41 3.8. Session and Session Management . . . . . . . . . . . . . 42 3.8.1. Session Setup Request. . . . . . . . . . . . . . 43 3.8.2. Session Setup Response . . . . . . . . . . . . . 46 3.8.3. Session Key Exchange . . . . . . . . . . . . . . 47 3.8.4. Session Termination. . . . . . . . . . . . . . . 48
4. Implementation Guidelines. . . . . . . . . . . . . . . . . . . 48 4.1. Server Implementation. . . . . . . . . . . . . . . . . . 48 4.2. Client Implementation. . . . . . . . . . . . . . . . . . 49 5. Security Considerations. . . . . . . . . . . . . . . . . . . . 49 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 50 7. Informative References . . . . . . . . . . . . . . . . . . . . 50 8. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 52 9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 531. Overview
The Handle System provides a general-purpose, secured global name service for the Internet. It was originally conceived and described in a paper by Robert Kahn and Robert Wilensky [18] in 1995. The Handle System defines a client server protocol in which client software submits requests via a network to handle servers. Each request describes the operation to be performed on the server. The server will process the request and return a message indicating the result of the operation. This document specifies the protocol for client software to access a handle server for handle resolution and administration. It does not include the description of the protocol used to manage handle servers. A discussion of the management protocol is out of the scope of this document and will be made available in a separate document. The document assumes that readers are familiar with the basic concepts of the Handle System as introduced in the "Handle System Overview" [1], as well as the data model and service definition given in the "Handle System Namespace and Service Definition" [2]. The Handle System consists of a set of service components as defined in [2]. From the client's point of view, the Handle System is a distributed database for handles. Different handles under the Handle System may be maintained by different handle servers at different network locations. The Handle protocol specifies the procedure for a client to locate the responsible handle server of any given handle. It also defines the messages exchanged between the client and server for any handle operation. Some key aspects of the Handle protocol include: o The Handle protocol supports both handle resolution and administration. The protocol follows the data and service model defined in [2]. o A client may authenticate any server response based on the server's digital signature.
o A server may authenticate its client as handle administrator
via the Handle authentication protocol. The Handle
authentication protocol is a challenge-response protocol that
supports both public-key and secret-key based authentication.
o A session may be established between the client and server so
that authentication information and network resources (e.g.,
TCP connection) may be shared among multiple operations. A
session key can be established to achieve data integrity and
confidentiality.
o The protocol can be extended to support new operations.
Controls can be used to extend the existing operations. The
protocol is defined to allow future backward compatibility.
o Distributed service architecture. Support service referral
among different service components.
o Handles and their data types are based on the ISO-10646
(Unicode 2.0) character set. UTF-8 [3] is the mandated
encoding under the Handle protocol.
The Handle protocol (version 2.1) specified in this document has
changed significantly from its earlier versions. These changes are
necessary due to changes made in the Handle System data model and the
service model. Servers that implement this protocol may continue to
support earlier versions of the protocol by checking the protocol
version specified in the Message Envelope (see section 2.2.1).
2. Protocol Elements
2.1. Conventions
The following conventions are followed by the Handle protocol to
ensure interoperability among different implementations.
2.1.1. Data Transmission Order
The order of transmission of data packets follows the network byte
order (also called the Big-Endian [11]). That is, when a data-gram
consists of a group of octets, the order of transmission of those
octets follows their natural order from left to right and from top to
bottom, as they are read in English. For example, in the following
diagram, the octets are transmitted in the order they are numbered.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
.-------------------------------.
| 1 | 2 |
|-------------------------------|
| 3 | 4 |
|-------------------------------|
| 5 | 6 |
'-------------------------------'
If an octet represents a numeric quantity, the left most bit is the
most significant bit. For example, the following diagram represents
the value 170 (decimal).
0 1 2 3 4 5 6 7
.---------------.
|1 0 1 0 1 0 1 0|
'---------------'
Similarly, whenever a multi-octet field represents a numeric
quantity, the left most bit is the most significant bit and the most
significant octet of the whole field is transmitted first.
2.1.2. Transport Layer
The Handle protocol is designed so that messages may be transmitted
either as separate data-grams over UDP or as a continuous byte stream
via a TCP connection. The recommended port number for both UDP and
TCP is 2641.
UDP Usage
Messages carried by UDP are restricted to 512 bytes (not including
the IP or UDP header). Longer messages must be fragmented into
UDP packets where each packet carries a proper sequence number in
the Message Envelope (see Section 2.2.1).
The optimum retransmission policy will vary depending on the
network or server performance, but the following are recommended:
o The client should try other servers or service interfaces
before repeating a request to the same server address.
o The retransmission interval should be based on prior
statistics if possible. Overly aggressive retransmission
should be avoided to prevent network congestion. The
recommended retransmission interval is 2-5 seconds.
o When transmitting large amounts of data, TCP-friendly
congestion control, such as an interface to the Congestion
Manager [12], should be implemented whenever possible to
avoid unfair consumption of the bandwidth against TCP-based
applications. Details of the congestion control will be
discussed in a separate document.
TCP Usage
Messages under the Handle protocol can be mapped directly into a
TCP byte-stream. However, the size of each message is limited by
the range of a 4-byte unsigned integer. Longer messages may be
fragmented into multiple messages before the transmission and
reassembled at the receiving end.
Several connection management policies are recommended:
o The server should support multiple connections and should
not block other activities waiting for TCP data.
o By default, the server should close the connection after
completing the request. However, if the request asks to
keep the connection open, the server should assume that the
client will initiate connection closing.
2.1.3. Character Case
Handles are character strings based on the ISO-10646 character set
and must be encoded in UTF-8. By default, handle characters are
treated as case-sensitive under the Handle protocol. A handle
service, however, may be implemented in such a way that ASCII
characters are processed case-insensitively. For example, the Global
Handle Registry (GHR) provides a handle service where ASCII
characters are processed in a case-insensitive manner. This suggests
that ASCII characters in any naming authority are case-insensitive.
When handles are created under a case-insensitive handle server,
their original case should be preserved. To avoid any confusion, the
server should avoid creating any handle whose character string
matches that of an existing handle, ignoring the case difference.
For example, if the handle "X/Y" was already created, the server
should refuse any request to create the handle "x/y" or any of its
case variations.
2.1.4. Standard String Type: UTF8-String
Handles are transmitted as UTF8-Strings under the Handle protocol. Throughout this document, UTF8-String stands for the data type that consists of a 4-byte unsigned integer followed by a character string in UTF-8 encoding. The leading integer specifies the number of octets of the character string.2.2. Common Elements
Each message exchanged under the system protocol consists of four sections (see Fig. 2.2). Some of these sections (e.g., the Message Body) may be empty depending on the protocol operation. The Message Envelope must always be present. It has a fixed size of 20 octets. The Message Envelope does not carry any application layer information and is primarily used to help deliver the message. Content in the Message Envelope is not protected by the digital signature in the Message Credential. The Message Header must always be present as well. It has a fixed size of 24 octets and holds the common data fields of all messages exchanged between client and server. These include the operation code, the response code, and the control options for each protocol operation. Content in the Message Header is protected by the digital signature in the Message Credential. The Message Body contains data specific to each protocol operation. Its format varies according to the operation code and the response code in the Message Header. The Message Body may be empty. Content in the Message Body is protected by the digital signature in the Message Credential. The Message Credential provides a mechanism for transport security for any message exchanged between the client and server. A non-empty Message Credential may contain the digital signature from the originator of the message or the one-way Message Authentication Code (MAC) based on a pre-established session key. The Message Credential may be used to authenticate the message between the client and server. It can also be used to check data integrity after its transmission.
.----------------------. | | ; Message wrapper for proper message | Message Envelope | ; delivery. Not protected by the | | ; digital signature in the Message | | ; Credential. |----------------------| | | ; Common data fields for all handle | Message Header | ; operations. | | |----------------------| | | ; Specific data fields for each | Message Body | ; request/response. | | |----------------------| | | ; Contains digital signature or | Message Credential | ; message authentication code (MAC) | | ; upon Message Header and Message '----------------------' ; Body. Fig 2.2: Message format under the Handle protocol2.2.1. Message Envelope
Each message begins with a Message Envelope under the Handle protocol. If a message has to be truncated before its transmission, each truncated portion must also begin with a Message Envelope. The Message Envelope allows the reassembly of the message at the receiving end. It has a fixed size of 20 octets and consists of seven fields: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 .---------------------------------------------------------------. | MajorVersion | MinorVersion | MessageFlag | |---------------------------------------------------------------| | SessionId | |---------------------------------------------------------------| | RequestId | |---------------------------------------------------------------| | SequenceNumber | |---------------------------------------------------------------| | MessageLength | '---------------------------------------------------------------'
2.2.1.1. <MajorVersion> and <MinorVersion>
The <MajorVersion> and <MinorVersion> are used to identify the version of the Handle protocol. Each of them is defined as a one- byte unsigned integer. This specification defines the protocol version whose <MajorVersion> is 2 and <MinorVersion> is 1. <MajorVersion> and <MinorVersion> are designed to allow future backward compatibility. A difference in <MajorVersion> indicates major variation in the protocol format and the party with the lower <MajorVersion> will have to upgrade its software to ensure precise communication. An increment in <MinorVersion> is made when additional capabilities are added to the protocol without any major change to the message format.2.2.1.2. <MessageFlag>
The <MessageFlag> consists of two octets defined as follows: 1 1 1 1 1 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 .---------------------------------------------------------------. |CP |EC |TC | Reserved | '---------------------------------------------------------------' Bit 0 is the CP (ComPressed) flag that indicates whether the message (excluding the Message Envelope) is compressed. If the CP bit is set (to 1), the message is compressed. Otherwise, the message is not compressed. The Handle protocol uses the same compression method as used by the FTP protocol[8]. Bit 1 is the EC (EnCrypted) flag that indicates whether the message (excluding the Message Envelope) is encrypted. The EC bit should only be set under an established session where a session key is in place. If the EC bit is set (to 1), the message is encrypted using the session key. Otherwise the message is not encrypted. Bit 2 is the TC (TrunCated) flag that indicates whether this is a truncated message. Message truncation happens most often when transmitting a large message over the UDP protocol. Details of message truncation (or fragmentation) will be discussed in section 2.3. Bits 3 to 15 are currently reserved and must be set to zero.
2.2.1.3. <SessionId>
The <SessionId> is a four-byte unsigned integer that identifies a communication session between the client and server. Session and its <SessionId> are assigned by a server, either upon an explicit request from a client or when multiple message exchanges are expected to fulfill the client's request. For example, the server will assign a unique <SessionId> in its response if it has to authenticate the client. A client may explicitly ask the server to set up a session as a virtually private communication channel like SSL [4]. Requests from clients without an established session must have their <SessionId> set to zero. The server must assign a unique non-zero <SessionId> for each new session. It is also responsible for terminating those sessions that are not in use after some period of time. Both clients and servers must maintain the same <SessionId> for messages exchanged under an established session. A message whose <SessionId> is zero indicates that no session has been established. The session and its state information may be shared among multiple handle operations. They may also be shared over multiple TCP connections as well. Once a session is established, both client and server must maintain their state information according to the <SessionId>. The state information may include the stage of the conversation, the other party's authentication information, and the session key that was established for message encryption or authentication. Details of these are discussed in section 3.8.2.2.1.4. <RequestId>
Each request from a client is identified by a <RequestId>, a 4-byte unsigned integer set by the client. Each <RequestId> must be unique from all other outstanding requests from the same client. The <RequestId> allows the client to keep track of its requests, and any response from the server must include the correct <RequestId>.2.2.1.5. <SequenceNumber>
Messages under the Handle protocol may be truncated during their transmission (e.g., under UDP). The <SequenceNumber> is a 4-byte unsigned integer used as a counter to keep track of each truncated portion of the original message. The message recipient can reassemble the original message based on the <SequenceNumber>. The <SequenceNumber> must start with 0 for each message. Each truncated message must set its TC flag in the Message Envelope. Messages that are not truncated must set their <SequenceNumber> to zero.
2.2.1.6. <MessageLen>
A 4-byte unsigned integer that specifies the total number of octets of any message, excluding those in the Message Envelope. The length of any single message exchanged under the Handle protocol is limited by the range of a 4-byte unsigned integer. Longer data can be transmitted as multiple messages with a common <RequestId>.2.2.2. Message Header
The Message Header contains the common data elements among any protocol operation. It has a fixed size of 24 octets and consists of eight fields. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 .---------------------------------------------------------------. | OpCode | |---------------------------------------------------------------| | ResponseCode | |---------------------------------------------------------------| | OpFlag | |---------------------------------------------------------------| | SiteInfoSerialNumber | RecursionCount| | |---------------------------------------------------------------| | ExpirationTime | |---------------------------------------------------------------| | BodyLength | '---------------------------------------------------------------' Every message that is not truncated must have a Message Header. If a message has to be truncated for its transmission, the Message Header must appear in the first truncated portion of the message. This is different from the Message Envelope, which appears in each truncated portion of the message.2.2.2.1. <OpCode>
The <OpCode> stands for operation code, which is a four-byte unsigned integer that specifies the intended operation. The following table lists the <OpCode>s that MUST be supported by all implementations in order to conform to the base protocol specification. Each operation code is given a symbolic name that is used throughout this document for easy reference.
Op_Code Symbolic Name Remark
--------- ------------- ------
0 OC_RESERVED Reserved
1 OC_RESOLUTION Handle query
2 OC_GET_SITEINFO Get HS_SITE values
100 OC_CREATE_HANDLE Create new handle
101 OC_DELETE_HANDLE Delete existing handle
102 OC_ADD_VALUE Add handle value(s)
103 OC_REMOVE_VALUE Remove handle value(s)
104 OC_MODIFY_VALUE Modify handle value(s)
105 OC_LIST_HANDLE List handles
106 OC_LIST_NA List sub-naming authorities
200 OC_CHALLENGE_RESPONSE Response to challenge
201 OC_VERIFY_RESPONSE Verify challenge response
300
: { Reserved for handle server administration }
399
400 OC_SESSION_SETUP Session setup request
401 OC_SESSION_TERMINATE Session termination request
402 OC_SESSION_EXCHANGEKEY Session key exchange
A detailed description of each of these <OpCode>s can be found in
section 3 of this document. In general, clients use the <OpCode> to
tell the server what kind of handle operation they want to
accomplish. Response from the server must maintain the same <OpCode>
as the original request and use the <ResponseCode> to indicate the
result.
2.2.2.2. <ResponseCode>
The <ResponseCode> is a 4-byte unsigned integer that is given by a
server to indicate the result of any service request. The list of
<ResponseCode>s used in the Handle protocol is defined in the
following table. Each response code is given a symbolic name that is
used throughout this document for easy reference.
Res. Code Symbolic Name Remark
--------- ------------- ------
0 RC_RESERVED Reserved for request
1 RC_SUCCESS Success response
2 RC_ERROR General error
3 RC_SERVER_BUSY Server too busy to respond
4 RC_PROTOCOL_ERROR Corrupted or
unrecognizable message
5 RC_OPERATION_DENIED Unsupported operation
6 RC_RECUR_LIMIT_EXCEEDED Too many recursions for
the request
100 RC_HANDLE_NOT_FOUND Handle not found
101 RC_HANDLE_ALREADY_EXIST Handle already exists
102 RC_INVALID_HANDLE Encoding (or syntax) error
200 RC_VALUE_NOT_FOUND Value not found
201 RC_VALUE_ALREADY_EXIST Value already exists
202 RC_VALUE_INVALID Invalid handle value
300 RC_EXPIRED_SITE_INFO SITE_INFO out of date
301 RC_SERVER_NOT_RESP Server not responsible
302 RC_SERVICE_REFERRAL Server referral
303 RC_NA_DELEGATE Naming authority delegation
takes place.
400 RC_NOT_AUTHORIZED Not authorized/permitted
401 RC_ACCESS_DENIED No access to data
402 RC_AUTHEN_NEEDED Authentication required
403 RC_AUTHEN_FAILED Failed to authenticate
404 RC_INVALID_CREDENTIAL Invalid credential
405 RC_AUTHEN_TIMEOUT Authentication timed out
406 RC_UNABLE_TO_AUTHEN Unable to authenticate
500 RC_SESSION_TIMEOUT Session expired
501 RC_SESSION_FAILED Unable to establish session
502 RC_NO_SESSION_KEY No session yet available
503 RC_SESSION_NO_SUPPORT Session not supported
504 RC_SESSION_KEY_INVALID Invalid session key
900 RC_TRYING Request under processing
901 RC_FORWARDED Request forwarded to
another server
902 RC_QUEUED Request queued for later
processing
Response codes under 10000 are reserved for system use. Any message with a response code under 10000 but not listed above should be treated as an unknown error. Response codes above 10000 are user defined and can be used for application specific purposes. Detailed descriptions of these <ResponseCode>s can be found in section 3 of this document. In general, any request from a client must have its <ResponseCode> set to 0. The response message from the server must have a non-zero <ResponseCode> to indicate the result. For example, a response message from a server with <ResponseCode> set to RC_SUCCESS indicates that the server has successfully fulfilled the client's request.2.2.2.3. <OpFlag>
The <OpFlag> is a 32-bit bit-mask that defines various control options for protocol operation. The following figure shows the location of each option flag in the <OpFlag> field. 1 1 1 1 1 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 .---------------------------------------------------------------. |AT |CT |ENC|REC|CA |CN |KC |PO |RD | Reserved | |---------------------------------------------------------------| | Reserved | '---------------------------------------------------------------' AT - AuThoritative bit. A request with the AT bit set (to 1) indicates that the request should be directed to the primary service site (instead of any mirroring sites). A response message with the AT bit set (to 1) indicates that the message is returned from a primary server (within the primary service site). CT - CerTified bit. A request with the CT bit set (to 1) asks the server to sign its response with its digital signature. A response with the CT bit set (to 1) indicates that the message is signed. The server must sign its response if the request has its CT bit set (to 1). If the server fails to provide a valid signature in its response, the client should discard the response and treat the request as failed. ENC - ENCryption bit. A request with the ENC bit set (to 1) requires the server to encrypt its response using the pre-established session key.
REC - RECursive bit. A request with the REC bit set (to 1)
asks the server to forward the query on behalf of the
client if the request has to be processed by another
handle server. The server may honor the request by
forwarding the request to the appropriate handle server
and passing on any result back to the client. The server
may also deny any such request by sending a response
with <ResponseCode> set to RC_SERVER_NOT_RESP.
CA - Cache Authentication. A request with the CA bit set (to
1) asks the caching server (if any) to authenticate any
server response (e.g., verifying the server's signature)
on behalf of the client. A response with the CA bit set
(to 1) indicates that the response has been
authenticated by the caching server.
CN - ContiNuous bit. A message with the CN bit set (to 1)
tells the message recipient that more messages that are
part of the same request (or response) will follow. This
happens if a request (or response) has data that is too
large to fit into any single message and has to be
fragmented into multiple messages.
KC - Keep Connection bit. A message with the KC bit set
requires the message recipient to keep the TCP
connection open (after the response is sent back). This
allows the same TCP connection to be used for multiple
handle operations.
PO - Public Only bit. Used by query operations only. A query
request with the PO bit set (to 1) indicates that the
client is only asking for handle values that have the
PUB_READ permission. A request with PO bit set to zero
asks for all the handle values regardless of their read
permission. If any of the handle values require
ADMIN_READ permission, the server must authenticate the
client as the handle administrator.
RD - Request-Digest bit. A request with the RD bit set (to 1)
asks the server to include in its response the message
digest of the request. A response message with the RD
bit set (to 1) indicates that the first field in the
Message Body contains the message digest of the original
request. The message digest can be used to check the
integrity of the server response. Details of these are
discussed later in this document.
All other bits in the <OpFlag> field are reserved and must be set to zero. In general, servers must honor the <OpFlag> specified in the request. If a requested option cannot be met, the server should return an error message with the proper <ResponseCode> as defined in the previous section.2.2.2.4. <SiteInfoSerialNumber>
The <SiteInfoSerialNumber> is a two-byte unsigned integer. The <SiteInfoSerialNumber> in a request refers to the <SerialNumber> of the HS_SITE value used by the client (to access the server). Servers can check the <SiteInfoSerialNumber> in the request to find out if the client has up-to-date service information. When possible, the server should fulfill a client's request even if the service information used by the client is out-of-date. However, the response message should specify the latest version of service information in the <SiteInforSerialNumber> field. Clients with out- of-date service information can update the service information from the Global Handle Registry. If the server cannot fulfill a client's request due to expired service information, it should reject the request and return an error message with <ResponseCode> set to RC_EXPIRED_SITE_INFO.2.2.2.5. <RecursionCount>
The <RecursionCount> is a one-byte unsigned integer that specifies the number of service recursions. Service recursion happens if the server has to forward the client's request to another server. Any request directly from the client must have its <RecursionCount> set to 0. If the server has to send a recursive request on behalf of the client, it must increment the <RecursionCount> by 1. Any response from the server must maintain the same <RecursionCount> as the one in the request. To prevent an infinite loop of service recursion, the server should be configurable to stop sending a recursive request when the <RecursionCount> reaches a certain value.2.2.2.6. <ExpirationTime>
The <ExpirationTime> is a 4-byte unsigned integer that specifies the time when the message should be considered expired, relative to January 1st, 1970 GMT, in seconds. It is set to zero if no expiration is expected.
2.2.2.7. <BodyLength>
The <BodyLength> is a 4-byte unsigned integer that specifies the number of octets in the Message Body. The <BodyLength> does not count the octets in the Message Header or those in the Message Credential.2.2.3. Message Body
The Message Body always follows the Message Header. The number of octets in the Message Body can be determined from the <BodyLength> in the Message Header. The Message Body may be empty. The exact format of the Message Body depends on the <OpCode> and the <ResponseCode> in the Message Header. Details of the Message Body under each <OpCode> and <ResponseCode> are described in section 3 of this document. For any response message, if the Message Header has its RD bit (in <OpFlag>) set to 1, the Message Body must begin with the message digest of the original request. The message digest is defined as follows: <RequestDigest> ::= <DigestAlgorithmIdentifier> <MessageDigest> where <DigestAlgorithmIdentifier> An octet that identifies the algorithm used to generate the message digest. If the octet is set to 1, the digest is generated using the MD5 [9] algorithm. If the octet is set to 2, SHA-1 [10] algorithm is used. <MessageDigest> The message digest itself. It is calculated upon the Message Header and the Message Body of the original request. The length of the field is fixed according to the digest algorithm. For MD5 algorithm, the length is 16 octets. For SHA-1, the length is 20 octets. The Message Body may be truncated into multiple portions during its transmission (e.g., over UDP). Recipients of such a message may reassemble the Message Body from each portion based on the <SequenceNumber> in the Message Envelope.
2.2.4. Message Credential
The Message Credential is primarily used to carry any digital signatures signed by the message issuer. It may also carry the Message Authentication Code (MAC) if a session key has been established. The Message Credential is used to protect contents in the Message Header and the Message Body from being tampered with during transmission. The format of the Message Credential is designed to be semantically compatible with PKCS#7 [5]. Each Message Credential consists of the following fields: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 .---------------------------------------------------------------. | CredentialLength | |---------------------------------------------------------------| | Version | Reserved | Options | |---------------------------------------------------------------| | | Signer: <Handle, Index> | |---------------------------------------------------------------| | Type (UTF8-String) | |---------------------------------------------------------------| | | SignedInfo: <Length> : 4-byte unsigned integer | DigestAlgorithm: <UTF8-String> | SignedData: <Length, Signature> | '---------------------------------------------------------------' where <CredentialLength> A 4-byte unsigned integer that specifies the number of octets in the Message Credential. It must be set to zero if the message has no Message Credential. <Version> An octet that identifies the version number of the Message Credential. The version number specified in this document is zero. <Reserved> An octet that must be set to zero. <Options> Two octets reserved for various cryptography options.
<Signer> ::= <HANDLE>
<INDEX>
A reference to a handle value in terms of the <HANDLE> and the
<INDEX> of the handle value. The handle value may contain the
public key, or the X.509 certificate, that can be used to
validate the digital signature.
<Type>
A UTF8-String that indicates the type of content in the
<SignedInfo> field (described below). It may contain HS_DIGEST if
<SignedInfo> contains the message digest, or HS_MAC if
<SignedInfo> contains the Message Authentication Code (MAC). The
<Type> field will specify the signature algorithm identifier if
<SignedInfo> contains a digital signature. For example, with the
<Type> field set to HS_SIGNED_PSS, the <SignedInfo> field will
contain the digital signature generated using the RSA-PSS
algorithm [16]. If the <Type> field is set to HS_SIGNED, the
<SignedInfo> field will contain the digital signature generated
from a DSA public key pair.
<SignedInfo> ::= <Length>
<DigestAlgorithm>
<SignedData>
where
<Length>
A 4-byte unsigned integer that specifies the number of
octets in the <SignedInfo> field.
<DigestAlgorithm>
A UTF8-String that refers to the digest algorithm used to
generate the digital signature. For example, the value
"SHA-1" indicates that the SHA-1 algorithm is used to
generate the message digest for the signature.
<SignedData> ::= <LENGTH>
<SIGNATURE>
where
<LENGTH>
A 4-byte unsigned integer that specifies the number of
octets in the <SIGNATURE>.
<SIGNATURE>
Contains the digital signature or the MAC over the
Message Header and Message Body. The syntax and
semantics of the signature depend on the <Type> field
and the public key referenced in the <Signer> field.
For example, if the <Type> field is "HS_SIGNED" and
the public key referred to by the <Signer> field is
a DSA [6] public key, the signature will be the
ASN.1 octet string representation of the parameter R
and S as described in [7]. If the <Signer> field
refers to a handle value that contains a X.509
certificate, the signature should be encoded according
to RFC 3279 and RFC 3280 [14, 15].
The Message Credential may contain the message authentication code
(MAC) generated using a pre-established session key. In this case,
the <Signer> field must set its <HANDLE> to a zero-length UTF8-String
and its <INDEX> to the <SessionId> specified in the Message Envelope.
The <Signature> field must contain the MAC in its <SIGNATURE> field.
The MAC is the result of the one-way hash over the concatenation of
the session key, the <Message Header>, the <MessageBody>, and the
session key again.
The Message Credential in a response message may contain the digital
signature signed by the server. The server's public key can be found
in the service information used by the client to send the request to
the server. In this case, the client should ignore any reference in
the <Signer> field and use the public key in the service information
to verify the signature.
The Message Credential can also be used for non-repudiation purposes.
This happens if the Message Credential contains a server's digital
signature. The signature may be used as evidence to demonstrate that
the server has rendered its service in response to a client's
request.
The Message Credential provides a mechanism for safe transmission of
any message between the client and server. Any message whose Message
Header and Message Body complies with its Message Credential suggests
that the message indeed comes from its originator and assures that
the message has not been tampered with during its transmission.
2.3. Message Transmission
A large message may be truncated into multiple packets during its
transmission. For example, to fit the size limit of a UDP packet,
the message issuer must truncate any large message into multiple UDP
packets before its transmission. The message recipient must
reassemble the message from these truncated packets before further
processing. Message truncation must be carried out over the entire
message except the Message Envelope. A new Message Envelope has to
be inserted in front of each truncated packet before its
transmission. For example, a large message that consists of
.--------------------------------------------------------.
| Message Envelope | Message Header, Body, Credential |
'--------------------------------------------------------'
may be truncated into:
.--------------------------------------------.
| Message Envelope 1 | Truncated_Packet 1 |
'--------------------------------------------'
.--------------------------------------------.
| Message Envelope 2 | Truncated_Packet 2 |
'--------------------------------------------'
......
.--------------------------------------------.
| Message Envelope N | Truncated Packet N |
'--------------------------------------------'
where the "Truncated_packet 1", "Truncated_packet 2", ..., and
"Truncated_packet N" result from truncating the Message Header, the
Message Body and the Message Credential. Each "Message Envelope i"
(inserted before each truncation) must set its TC flag to 1 and
maintain the proper sequence count (in the <SequenceNumber>). Each
"Message Envelope i" must also set its <MessageLength> to reflect the
size of the packet. The recipient of these truncated packets can
reassemble the message by concatenating these packets based on their
<SequenceNumber>.
3. Handle Protocol Operations
This section describes the details of each protocol operation in
terms of messages exchanged between the client and server. It also
defines the format of the Message Body according to each <OpCode> and
<ResponseCode> in the Message Header.
3.1. Client Bootstrapping
3.1.1. Global Handle Registry and its Service Information
The service information for the Global Handle Registry (GHR) allows
clients to contact the GHR to find out the responsible service
components for their handles. The service information is a set of
HS_SITE values assigned to the root handle "0.NA/0.NA" and is also
called the root service information. The root service information may be distributed along with the client software, or be downloaded from the Handle System website at http://www.handle.net. Changes to the root service information are identified by the <SerialNumber> in the HS_SITE values. A server at GHR can find out if the root service information used by the client is outdated by checking the <SerialNumber> in the client's request. The client should update the root service information if the <ResponseCode> of the response message is RC_EXPIRED_SITE_INFO. Clients may obtain the most up-to-date root service information from the root handle. The GHR must sign the root service information using the public key specified in the outdated service information (identified in the client's request) so that the client can validate the signature.3.1.2. Locating the Handle System Service Component
Each handle under the Handle System is managed by a unique handle service component (e.g., LHS). For any given handle, the responsible service component (and its service information) can be found from its naming authority handle. Before resolving any given handle, the client needs to find the responsible service component by querying the naming authority handle from the GHR. For example, to find the responsible LHS for the handle "1000/abc", client software can query the GHR for the HS_SITE (or HS_SERV) values assigned to the naming authority handle "0.NA/1000". The set of HS_SITE values provides the service information of the LHS that manages every handle under the naming authority "1000". If no HS_SITE values are found, the client can check if there is any HS_SERV value assigned to the naming authority handle. The HS_SERV value provides the service handle that maintains the service information for the LHS. Service handles are used to manage the service information shared by different naming authorities. It is possible that the naming authority handle requested by the client does not reside at the GHR. This happens when naming authority delegation takes place. Naming authority delegation happens when a naming authority delegates an LHS to manage all its child naming authorities. In this case, the delegating naming authority must contain the service information, a set of HS_NA_DELEGATE values, of the LHS that manages its child naming authorities. All top-level naming authority handles must be registered and managed by the GHR. When a server at the GHR receives a request for a naming authority that has been delegated to an LHS, it must return a message with the <ResponseCode> set to RC_NA_DELEGATE, along with the
HS_NA_DELAGATE values from the nearest ancestor naming authority. The client can query the LHS described by the HS_NA_DELAGATE values for the delegated naming authority handle. In practice, the ancestor naming authority should make itself available to any handle server within the GHR, by replicating itself at the time of delegation. This will prevent any cross-queries among handle servers (within a service site) when the naming authority in query and the ancestor naming authority do not hash into the same handle server.3.1.3. Selecting the Responsible Server
Each handle service component is defined in terms of a set of HS_SITE values. Each of these HS_SITE values defines a service site within the service component. A service site may consist of a group of handle servers. For any given handle, the responsible handle server within the service component can be found following this procedure: 1. Select a preferred service site. Each service site is defined in terms of an HS_SITE value. The HS_SITE value may contain a <Description> or other attributes (under the <AttributeList>) to help the selection. Clients must select the primary service site for any administrative operations. 2. Locate the responsible server within the service site. This can be done as follows: Convert every ASCII character in the handle to its upper case. Calculate the MD5 hash of the converted handle string according to the <HashOption> given in the HS_SITE value. Take the last 4 bytes of the hash result as a signed integer. Modulo the absolute value of the integer by the <NumOfServer> given in the HS_SITE value. The result is the sequence number of the <ServerRecord> listed in the HS_SITE value. For example, if the result of the modulation is 2, the third <ServerRecord> listed in the <HS_SITE> should be selected. The <ServerRecord> defines the responsible handle server for the given handle.3.2. Query Operation
A query operation consists of a client sending a query request to the responsible handle server and the server returning the query result to the client. Query requests are used to retrieve handle values assigned to any given handle.