RFC3652 Handle System Protocol (ver 2
3652 Handle System Protocol (ver 2.1) Specification. S. Sun, S.Reilly, L. Lannom, J. Petrone. November 2003. (Format: TXT=124380 bytes) (Status: INFORMATIONAL)
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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. Sun, et al. Informational [Page 1] RFC 3652 Handle System Protocol (v2.1) November 2003 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 Sun, et al. Informational [Page 2] RFC 3652 Handle System Protocol (v2.1) November 2003 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 . . . . . . . . . . . . . . . . . . . 53 1. 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. Sun, et al. Informational [Page 3] RFC 3652 Handle System Protocol (v2.1) November 2003 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. Sun, et al. Informational [Page 4] RFC 3652 Handle System Protocol (v2.1) November 2003 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. Sun, et al. Informational [Page 5] RFC 3652 Handle System Protocol (v2.1) November 2003 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. Sun, et al. Informational [Page 6] RFC 3652 Handle System Protocol (v2.1) November 2003 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. Sun, et al. Informational [Page 7] RFC 3652 Handle System Protocol (v2.1) November 2003 .----------------------. | | ; 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 protocol 2.2.1. 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 | '---------------------------------------------------------------' Sun, et al. Informational [Page 8] RFC 3652 Handle System Protocol (v2.1) November 2003 2.2.1.1.and The and 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 is 2 and is 1. and are designed to allow future backward compatibility. A difference in indicates major variation in the protocol format and the party with the lower will have to upgrade its software to ensure precise communication. An increment in is made when additional capabilities are added to the protocol without any major change to the message format. 2.2.1.2. The 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. Sun, et al. Informational [Page 9] RFC 3652 Handle System Protocol (v2.1) November 2003 2.2.1.3. The is a four-byte unsigned integer that identifies a communication session between the client and server. Session and its 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 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 set to zero. The server must assign a unique non-zero 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 for messages exchanged under an established session. A message whose 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 . 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. Each request from a client is identified by a , a 4-byte unsigned integer set by the client. Each must be unique from all other outstanding requests from the same client. The allows the client to keep track of its requests, and any response from the server must include the correct . 2.2.1.5. Messages under the Handle protocol may be truncated during their transmission (e.g., under UDP). The 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 . The 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 to zero. Sun, et al. Informational [Page 10] RFC 3652 Handle System Protocol (v2.1) November 2003 2.2.1.6. 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 . 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. The stands for operation code, which is a four-byte unsigned integer that specifies the intended operation. The following table lists the 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. Sun, et al. Informational [Page 11] RFC 3652 Handle System Protocol (v2.1) November 2003 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 s can be found in section 3 of this document. In general, clients use the to tell the server what kind of handle operation they want to accomplish. Response from the server must maintain the same as the original request and use the to indicate the result. 2.2.2.2. The is a 4-byte unsigned integer that is given by a server to indicate the result of any service request. The list of 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. Sun, et al. Informational [Page 12] RFC 3652 Handle System Protocol (v2.1) November 2003 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 Sun, et al. Informational [Page 13] RFC 3652 Handle System Protocol (v2.1) November 2003 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 s can be found in section 3 of this document. In general, any request from a client must have its set to 0. The response message from the server must have a non-zero to indicate the result. For example, a response message from a server with set to RC_SUCCESS indicates that the server has successfully fulfilled the client's request. 2.2.2.3. The 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 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. Sun, et al. Informational [Page 14] RFC 3652 Handle System Protocol (v2.1) November 2003 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 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. Sun, et al. Informational [Page 15] RFC 3652 Handle System Protocol (v2.1) November 2003 All other bits in the field are reserved and must be set to zero. In general, servers must honor the specified in the request. If a requested option cannot be met, the server should return an error message with the proper as defined in the previous section. 2.2.2.4. The is a two-byte unsigned integer. The in a request refers to the of the HS_SITE value used by the client (to access the server). Servers can check the 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 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 set to RC_EXPIRED_SITE_INFO. 2.2.2.5. The 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 set to 0. If the server has to send a recursive request on behalf of the client, it must increment the by 1. Any response from the server must maintain the same 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 reaches a certain value. 2.2.2.6. The 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. Sun, et al. Informational [Page 16] RFC 3652 Handle System Protocol (v2.1) November 2003 2.2.2.7. The is a 4-byte unsigned integer that specifies the number of octets in the Message Body. The 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 in the Message Header. The Message Body may be empty. The exact format of the Message Body depends on the and the in the Message Header. Details of the Message Body under each and are described in section 3 of this document. For any response message, if the Message Header has its RD bit (in ) set to 1, the Message Body must begin with the message digest of the original request. The message digest is defined as follows: ::= where 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. 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 in the Message Envelope. Sun, et al. Informational [Page 17] RFC 3652 Handle System Protocol (v2.1) November 2003 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: | |---------------------------------------------------------------| | Type (UTF8-String) | |---------------------------------------------------------------| | | SignedInfo: : 4-byte unsigned integer | DigestAlgorithm: | SignedData: | '---------------------------------------------------------------' where 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. An octet that identifies the version number of the Message Credential. The version number specified in this document is zero. An octet that must be set to zero. Two octets reserved for various cryptography options. Sun, et al. Informational [Page 18] RFC 3652 Handle System Protocol (v2.1) November 2003 ::= A reference to a handle value in terms of the and the 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. A UTF8-String that indicates the type of content in the field (described below). It may contain HS_DIGEST if contains the message digest, or HS_MAC if contains the Message Authentication Code (MAC). The field will specify the signature algorithm identifier if contains a digital signature. For example, with the field set to HS_SIGNED_PSS, the field will contain the digital signature generated using the RSA-PSS algorithm [16]. If the field is set to HS_SIGNED, the field will contain the digital signature generated from a DSA public key pair. ::= where A 4-byte unsigned integer that specifies the number of octets in the field. 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. ::= where A 4-byte unsigned integer that specifies the number of octets in the . Contains the digital signature or the MAC over the Message Header and Message Body. The syntax and semantics of the signature depend on the field Sun, et al. Informational [Page 19] RFC 3652 Handle System Protocol (v2.1) November 2003 and the public key referenced in the field. For example, if the field is "HS_SIGNED" and the public key referred to by the 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 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 field must set its to a zero-length UTF8-String and its to the specified in the Message Envelope. The field must contain the MAC in its field. The MAC is the result of the one-way hash over the concatenation of the session key, the , the , 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 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 Sun, et al. Informational [Page 20] RFC 3652 Handle System Protocol (v2.1) November 2003 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 ). Each "Message Envelope i" must also set its to reflect the size of the packet. The recipient of these truncated packets can reassemble the message by concatenating these packets based on their . 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 and 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 Sun, et al. Informational [Page 21] RFC 3652 Handle System Protocol (v2.1) November 2003 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 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 in the client's request. The client should update the root service information if the 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 set to RC_NA_DELEGATE, along with the Sun, et al. Informational [Page 22] RFC 3652 Handle System Protocol (v2.1) November 2003 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 or other attributes (under the ) 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 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 given in the HS_SITE value. The result is the sequence number of the listed in the HS_SITE value. For example, if the result of the modulation is 2, the third listed in the should be selected. The 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. Sun, et al. Informational [Page 23] RFC 3652 Handle System Protocol (v2.1) November 2003 3.2.1. Query Request The Message Header of any query request must set its to OC_RESOLUTION (defined in section 2.2.2.1) and to 0. The Message Body for any query request is defined as follows: ::= where A UTF8-String (as defined in section 2.1.4) that specifies the handle to be resolved. A 4-byte unsigned integer followed by an array of 4-byte unsigned integers. The first integer indicates the number of integers in the integer array. Each number in the integer array is a handle value index and refers to a handle value to be retrieved. The client sets the first integer to zero (followed by an empty array) to ask for all the handle values regardless of their index. A 4-byte unsigned integer followed by a list of UTF8- Strings. The first integer indicates the number of UTF8-Strings in the list that follows. Each UTF8-String in the list specifies a data type. This tells the server to return all handle values whose data type is listed in the list. If a UTF8-String ends with the '.' (0x2E) character, the server must return all handle values whose data type is under the type hierarchy specified in the UTF8-String. The may contain no UTF8-String if the first integer is 0. In this case, the server must return all handle values regardless of their data type. If a query request does not specify any index or data type and the PO flag (in the Message Header) is set, the server will return all the handle values that have the PUBLIC_READ permission. Clients can also send queries without the PO flag set. In this case, the server will return all the handle values with PUBLIC_READ permission and all the handle values with ADMIN_READ permission. If the query requests a specific handle value via the value index and the value does not have PUBLIC_READ permission, the server should accept the request (and authenticate the client) even if the request has its PO flag set. Sun, et al. Informational [Page 24] RFC 3652 Handle System Protocol (v2.1) November 2003 If a query consists of a non-empty but an empty , the server should only return those handle values whose indexes are listed in the . Likewise, if a query consists of a non-empty but an empty , the server should only return those handle values whose data types are listed in the . When both and fields are non-empty, the server should return all handle values whose indexes are listed in the AND all handle values whose data types are listed in the . 3.2.2. Successful Query Response The Message Header of any query response must set its to OC_RESOLUTION. A successful query response must set its to RC_SUCCESS. The message body of the successful query response is defined as follows: ::= [ ] where Optional field as defined in section 2.2.3. A UTF8-String that specifies the handle queried by the client. A 4-byte unsigned integer followed by a list of handle values. The integer specifies the number of handle values in the list. The encoding of each handle value follows the specification given in [2] (see section 3.1). The integer is set to zero if there is no handle value that satisfies the query. Sun, et al. Informational [Page 25] RFC 3652 Handle System Protocol (v2.1) November 2003 3.2.3. Unsuccessful Query Response If a server cannot fulfill a client's request, it must return an error message. The general format for any error message from the server is specified in section 3.3 of this document. For example, a server must return an error message if the queried handle does not exist in its database. The error message will have an empty message body and have its set to RC_HANDLE_NOT_FOUND. Note that a server should NOT return an RC_HANDLE_NOT_FOUND message if the server is not responsible for the handle being queried. It is possible that the queried handle exists but is managed by another handle server (under some other handle service). When this happens, the server should either send a service referral (see section 3.4) or simply return an error message with set to RC_SERVER_NOT_RESP. The server may return an error message with set to RC_SERVER_BUSY if the server is too busy to process the request. Like RC_HANDLE_NOT_FOUND, an RC_SERVER_BUSY message also has an empty message body. Servers should return an RC_ACCESS_DENIED message if the request asks for a specific handle value (via the handle value index) that has neither PUBLIC_READ nor ADMIN_READ permission. A handle Server may ask its client to authenticate itself as the handle administrator during the resolution. This happens if any handle value in query has ADMIN_READ permission, but no PUBLIC_READ permission. Details of client authentication are described later in this document. 3.3. Error Response from Server A handle server will return an error message if it encounters an error when processing a request. Any error response from the server must maintain the same (in the message header) as the one in the original request. Each error condition is identified by a unique as defined in section 2.2.2.2 of this document. Sun, et al. Informational [Page 26] RFC 3652 Handle System Protocol (v2.1) November 2003 The Message Body of an error message may be empty. Otherwise it consists of the following data fields (unless otherwise specified): ::= [ ] [ ] where Optional field as defined in section 2.2.3. A UTF8-String that explains the error. An optional field. When not empty, it consists of a 4-byte unsigned integer followed by a list of handle value indexes. The first integer indicates the number of indexes in the list. Each index in the list is a 4-byte unsigned integer that refers to a handle value that contributed to the error. An example would be a server that is asked to add three handle values, with indexes 1, 2, and 3, and handle values with indexes of 1 and 2 already in existence. In this case, the server could return an error message with set to RC_VALUE_ALREADY_EXIST and add index 1 and 2 to the . Note that the server is not obligated to return the complete list of handle value indexes that may have caused the error. 3.4. Service Referral A handle server may receive requests for handles that are managed by some other handle server or service. When this happens, the server has the option to either return a referral message that directs the client to the proper handle service, or simply return an error message with set to RC_SERVER_NOT_RESP. Service referral also happens when ownership of handles moves from one handle service to another. It may also be used by any local handle service to delegate its service into multiple service layers. The Message Header of a service referral must maintain the same as the one in the original request and set its to RC_SERVICE_REFERRAL. Sun, et al. Informational [Page 27] RFC 3652 Handle System Protocol (v2.1) November 2003 The Message Body of any service referral is defined as follows: ::= [ ] [ ] where Optional field as defined in section 2.2.3. A UTF8-String that identifies the handle (e.g., a service handle) that maintains the referral information (i.e., the service information of the handle service in which this refers). If the is set to "0.NA/0.NA", it is referring the client to the GHR. An optional field that must be empty if the is provided. When not empty, it consists of a 4-byte unsigned integer, followed by a list of HS_SITE values. The integer specifies the number of HS_SITE values in the list. Unlike regular query responses that may consist of handle values of any data type, a service referral can only have zero or more HS_SITE values in its . The may contain an empty UTF8-String if the HS_SITE values in the are not maintained by any handle. Care must be taken by clients to avoid any loops caused by service referrals. It is also the client's responsibility to authenticate the service information obtained from the service referral. A client should always use its own copy of the GHR service information if the is set to "0.NA/0.NA". 3.5. Client Authentication Clients are asked to authenticate themselves as handle administrators when querying for any handle value with ADMIN_READ but no PUBLIC_READ permission. Client authentication is also required for any handle administration requests that require administrator privileges. This includes adding, removing, or modifying handles or handle values. Client authentication consists of multiple messages exchanged between the client and server. Such messages include the challenge from the server to the client to authenticate the client, the challenge- response from the client in response to the server's challenge, and Sun, et al. Informational [Page 28] RFC 3652 Handle System Protocol (v2.1) November 2003 the verification request and response message if secret key authentication takes place. Messages exchanged during the authentication are correlated via a unique assigned by the server. For each authentication session, the server needs to maintain the state information that includes the server's challenge, the challenge-response from the client, as well as the original client request. The authentication starts with a response message from the server that contains a challenge to the client. The client must respond to the challenge with a challenge-response message. The server validates the challenge-response, either by verifying the digital signature inside the challenge-response, or by sending a verification request to another handle server (herein referred to as the verification server), that maintains the secret key for the administrator. The purpose of the challenge and the challenge- response is to prove to the server that the client possesses the private key (or the secret key) of the handle administrator. If the authentication fails, an error response will be sent back with the set to RC_AUTHEN_FAILED. Upon successful client authentication, the server must also make sure that the administrator is authorized for the request. If the administrator has sufficient privileges, the server will process the request and send back the result. If the administrator does not have sufficient privileges, the server will return an error message with set to RC_NOT_AUTHORIZED. The following sections provide details of each message exchanged during the authentication process. 3.5.1. Challenge from Server to Client The Message Header of the CHALLENGE must keep the same as the original request and set the to RC_AUTH_NEEDED. The server must assign a non-zero unique in the Message Envelope to keep track of the authentication. It must also set the RD flag of the (see section 2.2.2.3) in the Message Header, regardless of whether the original request had the RD bit set or not. Sun, et al. Informational [Page 29] RFC 3652 Handle System Protocol (v2.1) November 2003 The Message Body of the server's CHALLENGE is defined as follows: ::= where Message Digest of the request message, as defined in section 2.2.3. A 4-byte unsigned integer followed by a random string generated by the server via a secure random number generator. The integer specifies the number of octets in the random string. The size of the random string should be no less than 20 octets. Note that the server will not sign the challenge if the client did not request the server to do so. If the client worries about whether it is speaking to the right server, it may ask the server to sign the . If the client requested the server to sign the but failed to validate the server's signature, the client should discard the server's response and reissue the request to the server. 3.5.2. Challenge-Response from Client to Server The Message Header of the CHALLENGE_RESPONSE must set its to OC_CHALLENGE_RESPONSE and its to 0. It must also keep the same (in the Message Envelope) as specified in the challenge from the server. The Message Body of the CHALLENGE_RESPONSE request is defines as follows: ::= where A UTF8-String that identifies the type of authentication key used by the client. For example, the field is set to "HS_SECKEY" if the client chooses to use a secret key for its authentication. The field is set to "HS_PUBKEY" if a public key is used instead. Sun, et al. Informational [Page 30] RFC 3652 Handle System Protocol (v2.1) November 2003 A UTF8-String that identifies the handle that holds the public or secret key of the handle administrator. A 4-byte unsigned integer that specifies the index of the handle value (of the ) that holds the public or secret key of the administrator. Contains either the Message Authentication Code (MAC) or the digital signature over the challenge from the server. If the is "HS_SECKEY", the consists of an octet followed by the MAC. The octet identifies the algorithm used to generate the MAC. For example, if the first octet is set to 0x01, the MAC is generated by MD5_Hash( + + ) where the is the administrator's secret key referenced by the and . The is the Message Body portion of the server's challenge. If the first octet in the is set to 0x02, the MAC is generated using SHA-1_Hash( + +