INTERNET-DRAFT H. Sugano
S. Fujimoto
Fujitsu
F. Mazzoldi
A. Diacakis
Personity, Inc.
G. Hudson
MIT
J. D. Ramsdell
The MITRE Corporation
Expires: April 2002 October 2001
Presence and Instant Messaging Protocol (PRIM)
Server-Server Protocol Specification
<draft-ietf-prim-server-00.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
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The list of Internet-Draft Shadow Directories can be accessed at
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Please send comments to the authors or to the prim@ml.fujitsulabs.com
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
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Abstract
The architecture and specifications of the Presence and Instant
Messaging protocols (PRIM) are described. PRIM defines a set of
protocols for the Presence and Instant Messaging services which
satisfy the IMPP requirements [RFC2779]. PRIM is also designed so as
to conform with the Common Profile for Instant Messaging (CPIM)
specification being developed in the IMPP WG. This memo describes
the PRIM Server-Server protocol specification.
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Table of Contents
1. Introduction ......................................... 5
1.1. Design Principles .................................... 5
1.2. Terminology .......................................... 6
2. Architecture ......................................... 6
2.1. Overall Architecture ................................. 6
2.2. Presence Model ....................................... 7
2.2.1. Presence Servers ..................................... 7
2.2.2. Presence Subscriptions ............................... 7
2.2.3. PRESENCE INFORMATION ................................. 8
2.3. Instant Messaging Model .............................. 8
3. Identifier Namespace ................................. 8
4. Establishing Connections ............................. 10
4.1. Server-server Connections ............................ 10
4.2. Connections and Services ............................. 10
4.3. Name Resolution ...................................... 11
4.4. Shared Connections ................................... 11
5. Command Structure .................................... 12
5.1. Generic Commands ..................................... 12
5.1.1. Command Headers ...................................... 12
5.1.2. Command Body ......................................... 13
5.2. Requests ............................................. 13
5.2.1. Method ............................................... 14
5.2.2. Version .............................................. 14
5.2.3. Request Identifier ................................... 15
5.2.4. Content Length ....................................... 15
5.3. Responses ............................................ 15
6. Command Headers ...................................... 16
6.1. General Headers ...................................... 16
6.1.1. From ................................................. 16
6.1.2. To ................................................... 17
6.1.3. Domain ............................................... 17
6.1.4. Auth-State ........................................... 17
6.1.5. SASL-Mechanism ....................................... 17
6.1.6. Redirect ............................................. 18
6.1.7. Server-Address ....................................... 18
6.1.8. AStrength ............................................ 18
6.1.9. Date ................................................. 20
6.2. Entity Headers ....................................... 20
6.2.1. Content-Type ......................................... 20
6.3. Presence Headers ..................................... 20
6.3.1. Duration ............................................. 20
6.3.2. Subscription-ID ...................................... 20
6.4. IM Headers ........................................... 21
6.4.1. Message-ID ........................................... 21
6.4.2. Conversation-ID ...................................... 21
6.4.3. Reply-To ............................................. 21
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7. Command Specifications ............................... 21
7.1. Presence Service Commands ............................ 21
7.1.1. SUBSCRIBE - Placement and renewal of SUBSCRIPTION .... 22
7.1.2. UNSUBSCRIBE - Removal of SUBSCRIPTION ................ 23
7.1.3. NOTIFY - Propagation of PRESENCE INFORMATION ......... 24
7.2. Instant Messaging Service Commands ................... 25
7.2.1. SEND - Sending Messages .............................. 25
7.3. General Commands ..................................... 27
7.3.1. LOGIN - Connection Setup ............................. 27
7.3.2. STARTTLS - Secuire Connection Setup .................. 28
7.3.3. LOGOUT - Connection Shutdown ......................... 29
7.3.4. PING - Testing a connectionG ......................... 29
7.3.5. VERIFYSERVER - Verifying a server's authority ........ 29
8. Response Codes ....................................... 30
9. Authentication ....................................... 33
9.1. Server-Server Authentication ......................... 33
9.2. Authentication Using LOGIN ........................... 34
10. Presence Information Data Format (PIDF) ............. 36
11. IM Format ........................................... 36
12. Security Considerations ............................. 37
13. References .......................................... 37
14. Acknowledgements .................................... 38
15. Author's Addresses .................................. 38
16. Full Copyright Statement ............................ 39
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1. Introduction
Instant Messaging and Presence (IM/P) services provide users a way to
know others are available to communicate with them primarily by
exchanging short text messages and possibly by other communications
media such as voice and/or video. The PRIM, PResence and Instant
Messaging, protocols are designed for such services so that these
services can be provided by a set of servers distributed across a
large number of administrative domains.
PRIM specifications are classified into two parts; a client-server
protocol specification and a server-server protocol specification.
The former is the protocol for clients of the PRIM IM/P services to
communicate with the IM/P servers exchanging PRESENCE INFORMATION and
INSTANT MESSAGES, and it is mainly used within a single
administrative domain. On the other hand, the latter is the protocol
for the IM/P servers to communicate with other servers possibly in
the different domains. This separation is meaningful because of the
simplified architecture of PRIM described below.
This memo gives the PRIM server-server protocol specification. This
serves as a protocol not only for communications between the PRIM
servers, but also for communications between different domains that
may internally use other protocols than PRIM. This is accomplished by
gatewaying the internal protocol to the PRIM protocol. The
specification of the PRIM client-server protocol is presented in a
separate document.
The PRIM specifications are developed on the basis of the IMPP
activities such as the Model and Requirements documents for the IM/P
services [RFC2778,RFC2779]. PRIM is also designed to conform to the
Common Profile for Instant Messaging (CPIM) specifications being
developed by the IMPP WG. This enables that users of PRIM services
exchange PRESENCE INFORMATION and INSTANT MESSAGES with the users of
the services which use other CPIM compatible protocols.
1.1. Design Principles
Some of the design principles on which the PRIM specifications are
based are as follows. Note that the latter two are only relevant to
the PRIM client-server protocol.
o Transfer protocol directly atop of TCP
PRIM assumes TCP as the basic transport mechanism for INSTANT
MESSAGES and PRESENCE INFORMATION. TCP provides a sufficiently
reliable transport infrastructure which is required by both INSTANT
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MESSAGING and PRESENCE SERVICES.
o Long-lived Client/Server connections
PRIM uses long-lived client/server TCP connections in order to
receive INSTANT MESSAGES and PRESENCE INFORMATION NOTIFICATIONS.
Note that this is the prevailing model used by most Presence and IM
systems today. It brings the following advantages:
- Overhead is reduced, because authentication is performed once, at
the beginning of the connection. This is important, for example,
when PRESENCE INFORMATION NOTIFICATIONS occur frequently.
- Connections are firewall friendly, because USER AGENTS initiate
connections from inside a firewall that can carry NOTIFICATIONS or
messages initiated from the outside.
o Selective Presence Publication
[RFC2779] stipulates various requirements for access control; 2.3.x
and several in section 5. Among others, we consider the feature of
"Polite Blocking" (5.1.15, 5.2.3) to be very important for PRESENCE
SERVICES. This protocol contains a mechanism for such selective
PRESENCE INFORMATION publication as well as in-band access control.
1.2. Terminology
[RFC2778] and [RFC2779] define the terminology for the PRESENCE and
INSTANT MESSAGING fields. Please refer to those documents for a
complete glossary of the UPPER CASED terms.
The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in RFC 2119 [34].
2. Architecture
This section describes an overall PRIM architecture for both client-
server and server-server protocols.
2.1. Overall Architecture
The PRIM architecture involves two components: Service Domains and
USER AGENTS. A Service Domain in the context of PRIM is an
administrative entity where a PRINCIPAL has its identifier as an
entity such as PRESENTITY/WATCHER and SENDER/INBOX to enjoy the
PRESENCE and INSTANT MESSAGING SERVICES. A PRINCIPAL's Service
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Domain is called its Home Domain, and the PRINCIPAL connects to its
Home Domain via a USER AGENT to access PRESENCE and INSTANT MESSAGING
SERVICES.
A Service Domain consists of PRESENCE and/or INSTANT MESSAGING
SERVERS together with USER AGENTS. A USER AGENT only communicates
with the SERVERS in its HOME DOMAIN, and the PRIM client-server
protocol is used by the USER AGENT and SERVERS. A SERVER can
communicate with other SERVERS using the PRIM server-server protocol
specified in this memo. The protocol commands transferred by this
protocol are those either initiated by the SERVER itself or relayed
on behalf of USER AGENTS. These SERVERS may be located in different
Service Domains.
The PRIM protocols are both connection-based, i.e. every protocol
commands are transferred through a TCP connection. A USER AGENT
communicating with a SERVER exchanges the protocol commands through a
client-server connection established between the SERVER and the USER
AGENT. Similarly, a SERVER communicating with another SERVER
exchanges the protocol commands using a server-server connection
between the two SERVERS.
2.2. Presence Model
2.2.1. Presence Servers
Presence servers are primary components of PRESENCE SERVICE. A
presence server in a Service Domain stores and manages PRESENCE
INFORMATION published by PRESENTITIES in that domain and
SUBSCRIPTIONS from SUBSCRIBERS to the PRESENTITIES. The SUBSCRIBERS
may be located in the same domain and may subscribe from different
domains. If a presence server receives a request for a PRESENTITY in
a different domain, it forwards the request to the target domain
using an inter-domain server-server connection.
When a part of PRESENCE INFORMATION of a PRESENTITY is changed,
NOTIFICATION messages for relevant SUBSCRIBERS to that particular
PRESENTITY will be issued by the presence server.
2.2.2. Presence Subscriptions
WATCHERS can subscribe to a PRESENTITY in order to receive
NOTIFICATIONS when the PRESENCE INFORMATION of that PRESENTITY
changes.
SUBSCRIPTIONS have a duration under which they are in effect. This
duration is specified at the time that the subscription is placed or
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renewed. Once that period elapses, the SUBSCRIPTION has to be either
renewed by the SUBSCRIBER, or else it MUST be removed by the
PRESENTITY's Presence Server.
This renewal may be either issued by the USER AGENT, or by the
SUBSCRIBER's Presence Server on behalf of the SUBSCRIBER.
2.2.3. PRESENCE INFORMATION
PRESENCE INFORMATION transported by the PRIM protocol consists of one
or more PRESENCE TUPLEs, as defined by the IMPP model document
[RFC2778]. PRIM adopts the CPIM Presence Information Data Format
[CPIM-PIDF] as its presence data format.
2.3. Instant Messaging Model
INSTANT MESSAGING SERVICE provides a functionality of sending and
receiving INSTANT MESSAGES for PRINCIPALS. USER AGENTS are able to
exchange INSTANT MESSAGES with a client-server connection to the
INSTANT MESSAGING SERVERS. An INSTANT MESSAGING SERVER provides an
INSTANT INBOX for receiving Instant Messages.
When a USER AGENT wishes to start receiving INSTANT MESSAGES, it
starts listening to that INSTANT INBOX. Conversely, when it no
longer wishes to receive INSTANT MESSAGES from that INSTANT INBOX, it
stops listening to the INBOX.
INSTANT INBOXes have two states, as described in RFC 2779: OPEN and
CLOSED. An INBOX is OPEN when at least one PRINCIPAL is listening to
that INBOX. It is CLOSED when there are no PRINCIPALS listening to
the INBOX.
If an INSTANT MESSAGE is sent to an INBOX that has multiple
PRINCIPALS listening, the message is considered to be delivered
successfully if at least one PRINCIPAL receives it.
3. Identifier Namespace
This section defines the syntax of identifiers which appear as the
protocol elements. The ABNF [RFC 2234] is used for the syntax
definitions.
The next ABNF defines a Presence or IM identifiers, which are used to
identify PRESENTITIES and INSTANT INBOXes respectively. It also
defines IP address formats to be referred in some header definitions.
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presence-id = word-pres ":" local-part "@" domain
im-id = word-im ":" local-part "@" domain
local-part = 1*( unreserved / escaped )
unreserved = ALPHA / DIGIT / "!" / "$" / "&" / "'" / "*"
/ "." / "+" / "-" / "/" / "=" / "?" / "_" / "~"
escaped = "%" hex-char hex-char
hex-char = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
/ "a" / "b" / "c" / "d" / "e" / "f"
domain = 1*domain-label *("." 1*domain-label)
domain-label = 1*( unreserved / escaped )
word-pres = %x70.72.65.73 ; "pres"
word-im = %x69.6D ; "im"
decimal-byte = 1*3DIGIT
ALPHA = <defined by RFC 2234 -- 'A'-'Z' / 'a'-'z'>
DIGIT = <defined by RFC 2234 -- '0'-'9'>
hex4 = 1*4hex-char
hexseq = hex4 *(":" hex4)
ip6-address = hexseq / hexseq "::" [ hexseq ] / "::" [ hexseq ]
ip4-address = "::" 1*1decimal-byte 3*3("." 1*1decimal-byte)
The PRIM Presence and IM identifiers are defined so as to align with
CPIM [CPIM]. They have the form of URI [RFC2396] and the same URI
schemes are selected for Presence identifiers ("pres:") and IM
identifiers ("im:").
The syntax for the "local-part" and "domain" of those identifiers are
similar to that for email addresses, specified as addr-spec in
[RFC822]. But, the characters defined in this specification is
restricted so as to conform to the URI syntax [RFC2396]. The
characters which are not allowed in this definition MUST be escaped.
Also note that, unlike a mailto: URL [RFC 2368], a pres: or im: URL
cannot contain multiple addresses.
Moreover, The syntax for "domain-label" here is so defined that it
will be conformant to the prospective specification of the
Internationalized Domain Name [IDN]. A string for "domain" MUST be a
valid domain name according to the rules currently in existence.
Followings are some examples of valid Presence and IM identifiers:
pres:joe@example.net
im:%22Jane%20Smith%22@domain.com
A PRIM USER AGENT SHOULD recognize a PRESENTITY or INSTANT INBOX
identifier without the scheme if it is entered in a PRESENCE or
INSTANT MESSAGING context. Similarly, a USER AGENT SHOULD display a
PRESENCE or INSTANT MESSAGING identifier without the scheme if it is
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displayed in a PRESENCE or INSTANT MESSAGING context.
A PRINCIPAL may or may not have the same IDENTIFIER for its
PRESENTITY and its IM INBOX. However, for an integrated Presence and
IM service, the service SHOULD NOT assign the IDENTIFIERS which are
different only in the scheme part to different PRINCIPALS.
4. Establishing Connections
4.1. Server-server Connections
A Presence or Instant Messaging Server send a command to another
server through a server-server connection. The command may be the one
issued by the server itself or the one issued originally by a USER
AGENT and forwarded. It can reuse an existing connection to the
destination server if already exists. If there is no connection to
the destination, the originating server tries to establish a new
connection. To do that, it will resolve the name of the recipient of
the command to locate the destination server.
When a server establishes a connection to another server, that
connection end-point can be authorized to communicate on behalf of
multiple PRESENTITIES or INBOXES. For example, if server A receives a
subscription request from server B, on behalf of user
thanos@personity.com, server A MUST verify that server B is one of
the servers of the personity.com domain. If so, it will then accept
other requests from server B that pertain to users of the
personity.com domain.
PRIM provides several methods to authenticate and authorize servers,
which are described in section 1x.x.
The connection may be closed by either side at any time when there
are no outstanding commands on the connection from that server's
point of view. A server which has received a command may close the
connection if it encounters a serious error during the processing of
the command. In this case, the server SHOULD respond with "400 Bad
Request" error if possible before closing the connection. Any
commands sent to a server which closed the connection before sending
a reply can safely be assumed to have gone unprocessed.
4.2. Connections and Services
PRIM specifications allow the separation of PRESENCE SERVICE and
INSTANT MESSAGING SERVICE, i.e. the specifications allow a server
only providing one of those services. A server (and a USER AGENT as
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well) may establish two distinct connections for the two services
even though they are provided by the same domain. Of course, a server
which serves only one of these services may establish only one
connection for that service to a single domain.
4.3. Name Resolution
For the server location, PRIM reuses the existing Domain Name
Services to achieve this. The domain name resolution is performed
with the domain name of the destination address of the PRIM command
to be transported.
A server MUST discover a remote domain's server using the following
algorithm: the server performs a SRV [RFC 2782] lookup for the remote
domain using the protocol "tcp" and the service "prim-pr" (for
PRESENCE) or "prim-im" (for INSTANT MESSAGING). If the two SRV
lookups for the "prim-pr" and "prim-im" services in a domain return
the same host and port number, the server MAY establish a single
connection to that host/port to enjoy the two services.
If no SRV record is present, the server performs an A lookup on the
remote domain and uses the resulting IP addresses with the allocated
port [xxx] for PRESENCE or [xxx] for INSTANT MESSAGING.
Note: The protocol is capable of using two different TCP ports: one
for the PRESENCE SERVICE and one for the INSTANT MESSAGING SERVICE.
However, the usage of one or two ports will be possible for different
needs. The protocol ensures there is no ambiguity between commands
received from different services.
4.4. Shared Connections
When a domain provides both the PRESENCE and INSTANT MESSAGING
SERVICES in a single host and port, it has been declared using the
DNS SRV RR as stated in the previous section. In that case, the
initiating server MAY open a single connection and authenticate
itself once on that connection using one of available authentication
methods.
The server can differentiate between the presence and instant
messaging service commands by the command name itself. The "general"
commands such as LOGIN, STARTTLS, or PING do not care which services
they are used for in a shared connection. If the STARTTLS command is
needed for the connection, one STARTTLS command is sufficient.
If a server received a command for the service it does not provide
for some unexpected reason, the server MUST respond with '501 Not
Implemented' error.
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5. Command Structure
This section describes the structure of generic PRIM commands and
also gives a classification of PRIM requests based on the connections
on which they are transported. The details of the requests
specifications are described separately in the later sections.
5.1. Generic Commands
A connection transports a sequence of commands. The underlying
character set for commands is Unicode, represented in UTF-8 [RFC
2279]. Command bodies are an exception; they should be treated as
unprocessed octets. An implementation MUST properly handle arbitrary
binary data in the body. A command is either a request or a
response.
PRIM-command = request / response
Requests and responses use the generic command format of [RFC822] for
transferring entities (the body of the command). Both types of
command consist of a start-line, one or more command-header fields
(also known as "headers"), an empty line (i.e., a line with nothing
preceding the CRLF) indicating the end of the header fields, and an
optional command-body.
generic-command = start-line
*command-header
CRLF
[ command-body ]
start-line = request-line / response-line
Receivers of commands SHOULD ignore any empty line(s) received where
a start-line is expected.
5.1.1. Command Headers
PRIM command-header fields follow the same syntactic restriction as
specified by [CPIM-MSGFMT]. Thus, each header field consists of a
header name followed by a colon ("%x3A"), a single whitespace
("%x20") and a field value. Header names are case-sensitive. The
entire header MUST be contained in a single line.
Command header fields are categorized into four types; general-
header, presence-header, im-header, and entity-header. General-
header fields are applicable to both of PRIM Presence and Instant
Messaging Protocols, and used for controlling the basic behavior of
the PRIM applications, such as connection management and delivery of
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the commands. Presence-header fields and im-header fields are
included as a meta-data of the content of the commands of the
Presence and Instant Messaging Protocols respectively. Entity-header
fields describes the common feature of the body of the command.
command-header = (general-header ;
/ presence-header ;
/ im-header ;
/ entity-header ;
)
5.1.2. Command Body
Some commands of the PRIM Presence and Instant Messaging Protocols
can contain a command-body. The command-body is used to carry
presence information, instant message, or other information.
5.2. Requests
A generic PRIM request includes the method to be applied to the
resource, the protocol version, and the data needed for asynchronous
requests.
request-line = method
SP version
SP request-identifier
SP content-length
CRLF
As PRIM specifies two kinds of protocols for Presence and Instant
Messaging Services, a PRIM request is classified into two categories.
request = (presence-request / im-request)
presence-request = request-line
*((general-header
/ presence-header
/ entity-header) CRLF)
CRLF
[ command-body ]
im-request = request-line
*((general-header
/ im-header
/ entity-header) CRLF)
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CRLF
[ command-body ]
5.2.1. Method
The method token indicates the method to be performed on the
resource. Here, methods are categorized into three groups; presence
methods for presence services, IM methods for instant messaging
services, and general methods for both. In section 8.4, these are
further classified for the detailed specifications.
method = general-method
/ presence-method
/ im-method
general-method = "LOGIN" ; Section 7.3.1
/ "STARTTLS" ; Section 7.3.2
/ "LOGOUT" ; Section 7.3.3
/ "PING" ; Section 7.3.4
/ "VERIFYSERVER" ; Section 7.3.5
presence-method = "SUBSCRIBE" ; Section 7.1.1
/ "UNSUBSCRIBE" ; Section 7.1.2
/ "NOTIFY" ; Section 7.1.3
im-method = "SEND" ; Section 7.2.1
5.2.2. Version
The version identifies the version of the protocol in use. It
contains the name string specifying the protocol and the major and
minor version numbers.
version = "PRIM" "/" 1*DIGIT "." 1*DIGIT
PRIM adopts the similar protocol versioning policy to those described
in RFC 2145 [RFC2145] and RFC 2616 [HTTP1.1]. Thus, the protocol
version is intended to allow the sender to indicate the format of a
command and its capability for understanding further communication.
See RFC 2616 and 2145 for more detailed explanations.
A PRIM application SHOULD send a command version equal to the highest
version for which it is at least conditionally compliant, and whose
major version is no higher than the highest version supported by the
other end, if it is known. A PRIM application MUST NOT send a
version for which it is not at least conditionally compliant.
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A server MAY send a 505 (Version Not Supported) response if cannot
send a response using the major version used in the client's request.
5.2.3. Request Identifier
Request identifiers are used to implement asynchronous requests.
request-identifier = 1*[ALPHA / DIGIT] / "-"
An endpoint of a connection is responsible for generating request
identifiers, and the request identifiers are used to match responses
it receives with the requests it has sent. The other endpoint of a
connection is responsible for labeling a response with the identifier
it received in the request. An identifier may be reused after the
endpoint receives the response to the request with the identifier.
The request identifier of a command is "-" if and only if the request
expects no reply. If an endpoint receives a request with the request
identifier "-", it MUST NOT send any response to the request.
5.2.4. Content Length
The content-length header contains the length of the command body in
bytes.
content-length = 1*DIGIT
5.3. Responses
A response includes many of the same fields as a request with the
addition of a status code and a response phrase.
response-line = version
SP request-identifier
SP content-length
SP status-code
SP response-phrase
CRLF
The request identifier in the response MUST NOT be "-".
The status-code is a 3 digit code and the response-phrase is a short
message description. The values are defined in Section 8.
Some status codes are common to all commands, whereas others are only
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used by a subset of commands. Common status codes to all commands
are:
200 OK
300 Redirect
400 Bad Request
401 Unauthorized (except for LOGIN)
402 Forbidden (except for LOGIN, STARTTLS, PING)
501 Internal Server Error
503 Version Not Supported
6. Command Headers
Command headers are defined as follows:
general-header = (from-header
/ to-header
/ auth-state-header
/ SASL-mechanism-header
/ redirect-header
/ server-address-header
/ astrength-header
/ date-header
)
presence-header = duration-header
im-header = (message-id-header
/ conversation-id-header
/ reply-to-header
)
entity-header = content-type-header
6.1. General Headers
6.1.1. From
Identifies the PRESENTITY or INBOX that issued this command, or that
it was issued on behalf of.
from-header = "From: " ( presence-id / im-id )
The value of this header is either "presence-id" or "im-id".
"presence-id" MUST be used only if the underlying method is a
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"presence-method" or "general-method". "im-id" MUST be used only if
the underlying method is an "im-method" or "general-method".
The receiving end of a command SHOULD always check that the sender is
authorized to send commands on behalf of the identifier in the from-
header, as described in Sections 13.
6.1.2. To
Specifies the PRESENTITY or INBOX this command is intended to.
to-header = "To: " ( presence-id / im-id )
The value of this header is either "presence-id" or "im-id".
"presence-id" MUST be used only if the underlying method is a
"presence-method" or "general-method". "im-id" MUST be used only if
the underlying method is an "im-method" or "general-method".
6.1.3. Domain
Identifies the domain when used with the LOGIN command in the
server-server connection.
domain-header = "Domain: " domain
The value of this header MUST be a valid domain name.
6.1.4. Auth-State
Indicates the status in the authentication process in the LOGIN
command.
auth-state-header = "Auth-State: "
( "init"
/ "continue"
/ "abort" )
6.1.5. SASL-Mechanism
Specifies the SASL mechanism in the LOGIN request or the response to
the LOGIN request. In the request, the SASL mechanism the USER AGENT
wants to use MUST be specified. When used in the response, one or
more mechanisms which the server supports MAY be specified.
SASL-mechanism-header = "SASL-Mech: " mechanisms
mechanisms = mechanism [ *(SP mechanism) ]
mechanism = 1*20(ALPHA / DIGIT / "-" / "_")
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6.1.6. Redirect
When a server cannot handle requests from a USER AGENT or other
server, it issues an error response "300 Redirect" which includes the
redirect-header. This lets the caller know that its request cannot
be handled at this server and an alternative server address and port
are provided.
redirect-header = "Redirect: " address SP port
address = domain / ip4-address / ip6-address
port = 1*DIGIT
6.1.7. Server-Address
Indicates the IP address for the server that is initiating the
connection. This header is used in the VERIFYSERVER method to show
the address of the server that needs verification (see Sections 10.5
and 13.2).
server-address-header = "Server-Address: "
( ip4-address / ip6-address )
6.1.8. AStrength
When a server acts as a relay, it MUST communicate to the next node a
rough indication of the authentication strength of the previous hops
using the "Astrength" header unless the servers already have
knowledge about the relaying server's authentication strength through
some out-of-band manner. If the servers acknowledge the
authentication strength of the other end, the AStrength header MAY
NOT appear in the relayed request.
The syntax for the Astrength header is:
astrength-header = "AStrength: " astrength
astrength = "strong" / "medium" / "weak" / "none"
The meanings of the astrength values are:
strong Command authenticity and integrity cannot be
compromised by an attacker who has full
control of all network links, assuming no
compromise of keying materials, installed
software, or cryptographic algorithms.
medium Command authenticity or integrity could be
compromised by a packet substitution or DNS
spoofing attack.
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weak Command could be forged by an attacker who has
previously been a passive listener on one or
more network links.
none Command could be forged by an attacker with no
special information.
Examples of medium protection include one-time passwords [RFC 2289]
and HTTP digest authentication [RFC 2617 section 3]. Examples of
weak protection include cleartext passwords or security protocols
subject to replay attacks.
If a server or USER AGENT receives a command with no Astrength
header, it should assume that the equivalent Astrength is "none".
A server relaying a command MUST communicate the weaker of the
strength of the connection it received the command on and the
Astrength value communicated from the last entity.
A server MAY choose to reject a command with a "410 AStrength Too
Weak" error because it does not come with sufficient authentication
strength (either as reported by the Astrength value or based on the
connection from the immediate requester). A relay MUST NOT reject a
response on the basis of insufficient authentication strength.
Note that, separately from connection-level authentication, an
operation may be authenticated using an end-to-end signature. The
Astrength header does not bear any relation to this kind of
authentication.
An example scenario: a PRIM USER AGENT connects to a server for
example.net and authenticates using a weak mechanism. It then issues
a "send" command from alice@example.net to bob@domain.com. The
example.net server connects to domain.com, authenticates using
DNSSEC- signed public keys and forwards the IM with "Astrength: weak"
because the previous link was authenticated with a weak. The
domain.com server sends the command to the clients receiving commands
for bob@domain.com with "Astrength: weak" since that was the
authentication value claimed by example.net, even though domain.com
received the command over a strongly authenticated link.
Another example scenario: a PRIM client connects to a server for
example.net and authenticates using some strong SASL mechanism as
alice. It then issues a "send" command from alice@example.net to
bob@domain.com. The example.net server connects to domain.com and
authenticates, but example.net's public key DNS record is not signed,
so it could have been forged by a DNS spoofing attack. The
example.net server sends the IM with "Astrength: strong" because it
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received the command from Alice over a strongly authenticated link;
however, the domain.com server will weaken the Astrength to "Medium"
when forwarding the command to Bob's clients.
6.1.9. Date
Specifies the date and time this command was originally issued. PRIM
adopts the date syntax as defined in Section 15.5, i.e. specified in
[RFC1123].
date-header = "Date: " date-time
; as defined in Section 15.5
[It will be affected by the CPIM specification because it would be
preferable to have the same format with it. Need more discussions.]
6.2. Entity Headers
6.2.1. Content-Type
A command-body MUST NOT be included unless the description of the
particular method allows it. If a command-body is included, the
protocol command headers MUST include a Content-Type as specified in
[RFC 2045].
The Content-Transfer-Encoding header from [RFC 2045] is not necessary
and MUST NOT be included in any command or response. An
implementation which receives a Content-Transfer-Encoding header
should reject the command with an error 400 Bad Request.
6.3. Presence Headers
6.3.1. Duration
When used with a SUBSCRIBE command and its response, it specifies the
amount of seconds the caused subscription SHOULD remain in effect
for.
duration-header = "Duration: " 1*DIGIT
6.3.2. Subscription-ID
Specifies the unique identifier of the subscription in the watcher
and presentity pair. This header MUST appear in the SUBSCRIBE and
NOTIFY commands, and in the responses to SUBSCRIBE commands.
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subscription-id-header = "Subscription-ID: " 1*(unreserved / escaped)
6.4. IM Headers
6.4.1. Message-ID
The message-id-header specifies the identifier of each IM, which
distinguishes the message from others. The sender must generate a
globally unique message-id for each IM sent.
message-id-header = "Message-ID" 1*(DIGIT / ALPHA) ": " im-id
6.4.2. Conversation-ID
The conversation-id is used in the SEND command to identify the
conversation channel shared by the participants of an IM exchange. A
"conversation channel" means a virtual channel which consists of a
thread of IMs. When a PRINCIPAL replies to an IM, the reply MUST
have the same conversation-id header.
conversation-id-header = "Conversation-ID: " 1*(unreserved / escaped)
6.4.3. Reply-To
The reply-to-header is optionally specified in a SEND command. It
indicates an INSTANT INBOX identifier where the sender would prefer
to receive any replies. The recipient SHOULD use the "reply-to"
header, instead of the "from" header, if the former exists.
reply-to-header = "Reply-To: " im-id
7. Command Specifications
This section describes the command specifications for the PRIM
commands used on the server-server connections. The commands are
those for establishing connections, and exchanging PRESENCE
INFORMATION and INSTANT MESSAGES.
In header descriptions below, the sign (o) on the right hand of a
header indicates that the header is optional.
7.1. Presence Service Commands
This section describes the details of the protocol for the PRESENCE
SERVICE.
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7.1.1. SUBSCRIBE - Placement and renewal of SUBSCRIPTION
Headers: Request Response
---------------------------------------------------------------
from-header from-header
to-header to-header
duration-header duration-header
subscription-id-header subscription-id-header
date-header
astrength-header (o)
content-type-header (o)
---------------------------------------------------------------
The SUBSCRIBE method is used to express a WATCHER's interest on the
PRESENCE INFORMATION of a PRESENTITY. There are two scenarios where
the method is issued: when a
o WATCHER wishes to establish a new SUBSCRIPTION to a PRESENTITY,
or
o Presence Server or USER AGENT needs to renew a SUBSCRIPTION on
behalf of a WATCHER
from-header: identifies the WATCHER requesting the SUBSCRIPTION.
to-header: specifies the PRESENTITY to subscribe to.
duration-header: specifies the amount of seconds that this
subscription is valid for.
subscription-id-header: specifies the unique identifier of the
subscription within the watcher (requester) and the presentity.
date-header: specifies date and time when the command is generated.
astrength-header: specifies the authentication strength of the
previous hops as described in Section 6.1.8.
The SUBSCRIBE command MAY have a command-body in order to present a
piece of information to the target presence server. The meaning of
the command-body depends on the services or implementations.
A response to the SUBSCRIBE command contains no command-body. After a
successful (200 or 201) response to the command, a NOTIFY command
which carries the presence information of the target PRESENTITY MUST
be immediately invoked.
If the value of the duration-header of a SUBSCRIBE command is zero,
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no subscription is established. In this case, if the subscription-
id-header's value is the same one as an existing SUBSCRIPTION of the
WATCHER to the PRESENTITY, that SUBSCRIPTION MUST be removed. If the
value of the subscription-id-header does not match any of the
existing SUBSCRIPTIONS of the WATCHER to the PRESENTITY, it has no
impact on these SUBSCRIPTIONS and the SUBSCRIBE command behaves like
"fetching" the PRESENCE INFORMATION.
The Return Codes are:
200 OK: The SUBSCRIPTION was placed successfully. The command
contains no command-body.
201 Duration Adjusted: The SUBSCRIPTION was placed successfully,
yet a different duration was set and this is indicated in the
duration- header of the response.
402 Forbidden: The PRESENTITY authenticated in the current
connection does not have rights (through the current ACL) to
SUBSCRIBE to the PRESENTITY requested. No command-body is present.
403 Resource Not Found: The PRESENTITY does not exist. No command-
body is present.
404 Subscription Not Found: The subscription specified by the
subscription-id-header does not exist in the case of renewing
SUBSCRIBE requests. No command-body is present.
505 Too Many Subscriptions: The maximum amount of SUBSCRIPTIONS
placed by the system administrator or by the targeted PRESENTITY
has been reached. No command-body is present.
If a SUBSCRIPTION already exists between a WATCHER and a PRESENTITY,
then a successful SUBSCRIBE request from the WATCHER updates the
duration of the SUBSCRIPTION to the value carried in the request.
7.1.2. UNSUBSCRIBE - Removal of SUBSCRIPTION
Headers: Request Response
---------------------------------------------------------------
from-header from-header
to-header to-header
astrength-header (o)
---------------------------------------------------------------
The UNSUBSCRIBE method indicates that the WATCHER is no longer
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interested in receiving NOTIFICATIONS for changes in PRESENCE
INFORMATION of a PRESENTITY.
It may either be issued by a USER AGENT or a Presence Server on
behalf of the WATCHER.
The from-header identifies the WATCHER requesting the SUBSCRIPTION
cancellation.
The to-header specifies the PRESENTITY to unsubscribe from.
The Response MUST NOT carry a command-body. The Return Codes in the
Response are:
200 OK: The SUBSCRIPTION was removed.
404 Subscription Not Found: there is no SUBSCRIPTION from the
specified WATCHER to the specified PRESENTITY.
Note: When the duration of a SUBSCRIPTION elapses, without the
reception of a renewal, the Presence Server MUST assume an implicit
UNSUBSCRIBE method has been received.
7.1.3. NOTIFY - Propagation of PRESENCE INFORMATION
Headers: Request Response
---------------------------------------------------------------
from-header from-header
to-header to-header
subscription-id-header
astrength-header (o)
duration-header (o)
date-header
content-type-header
---------------------------------------------------------------
The NOTIFY command informs WATCHERS when the PRESENCE INFORMATION of
the PRESENTITY they have SUBSCRIPTIONS to has changed. Also, it MUST
be issued immediately after processing of successful SUBSCRIBE
commands. The NOTIFY will carry the whole PRESENCE INFORMATION and
not just the modified tuple.
The command-body carries a presence document corresponding to the
PRESENCE INFORMATION for the PRESENTITY. The body MUST be a data of
the Content-Type "message/cpim" [CPIM-MSGFMT] containing an
"application/cpim-pidf+xml" data [CPIM-PIDF], or just a data of the
"application/cpim-pidf+xml" type.
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The headers for this command are:
from-header: identifies the PRESENTITY this NOTIFICATION is about.
to-header: specifies the WATCHER that needs to receive this
information.
astrength-header: specifies the authentication strength of the
previous hops as described in Section 6.1.8.
duration-header: specifies the amount of remaining seconds that the
corresponding subscription is valid for. Optional.
date-header: specifies date and time when the command is generated.
content-type-header: specifies the content type of the command-
body.
The Response MUST NOT carry any command-body.
The NOTIFY command MAY contain the duration-header that specifies the
amount of remaining seconds of the corresponding SUBSCRIPTION. If
the value of the duration-header is zero, the NOTIFY command informs
the WATCHER that the SUBSCRIPTION has been canceled by some means.
No future NOTIFICATIONS will be sent to this WATCHER.
The Return Codes are:
200 OK: the PRESENCE INFORMATION was received and processed
correctly.
400 Bad Request: The command was malformed or the command-body did
not carry a valid XML document. The PRESENCE INFORMATION was not
accepted.
403 Resource Not Found: no such WATCHER exists.
7.2. Instant Messaging Service Commands
This section describes the details of the commands for the INSTANT
MESSAGE SERVICE.
7.2.1. SEND - Sending Messages
Headers: Request Response
---------------------------------------------------------------
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from-header from-header
to-header to-header
message-id-header message-id-header
conversation-id-header conversation-id-header
date-header
astrength-header (o)
content-type-header
---------------------------------------------------------------
[Note. It would be necessary to make the "SEND" command syntax
compatible with the CPIM specification. We need more discussion.]
The SEND command is used to transport an INSTANT MESSAGE.
The command-body carries an INSTANT MESSAGE, as described in section
11.
The headers for this command are:
from-header: identifies the SENDER of the message.
to-header: identifies the INSTANT INBOX the message is sent to.
astrength-header: indicates the lowest authentication strength for
previous hops of the command.
message-id-header: specifies a unique identifier for each INSTANT
MESSAGE.
conversation-id-header: specifies a unique identifier to
distinguish a given conversation thread between multiple
participants.
date-header: specifies date and time when the command is generated.
content-type-header: specifies the content type of the command-
body.
The response to this method MUST NOT carry any command-body, and MAY
have the following return codes:
101 Unknown Delivery Status: The IM Service cannot assure that the
message was delivered.
200 OK: the INSTANT MESSAGE was delivered at least to one PRINCIPAL
that was listening to the recipient INSTANT INBOX.
402 Forbidden: The PRINCIPAL authenticated in the current
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connection does not have rights (through the current ACL) to send
messages to the recipient INSTANT INBOX.
408 Inbox Is Closed: the INSTANT MESSAGE could not be delivered
because the recipient INSTANT INBOX was closed. This may be issued
by either the IM Server if there is no-one listening to that inbox,
or by a USER AGENT if it decides to block the sender (see
explanation below).
The response code sent by the IM Server hosting the recipient INSTANT
INBOX is always the most positive response from all the connections
listening to that INBOX. Thus, if at least one USER AGENT
acknowledges the message, then its server will acknowledge it too.
Note: It is important to remember that PRESENCE INFORMATION may be
revealed through the responses to INSTANT MESSAGES. For example, it
may be possible for someone to "ping" an INSTANT INBOX by sending
messages to it, in order to deduce PRESENCE INFORMATION from the
state of that INBOX. USER AGENT implementations can prevent that if
necessary by returning 408 Inbox Is Closed if the sender of an
INSTANT MESSAGE should not know that the INBOX is OPEN.
7.3. General Commands
The commands described in this section apply to both the PRESENCE and
INSTANT MESSAGING services.
7.3.1. LOGIN - Connection Setup
Headers: Request Response
---------------------------------------------------------------
domain-header domain-header
auth-state-header auth-state-header
SASL-mechanism-header SASL-mechanism-header
---------------------------------------------------------------
For a server-server connection, the initiating host MAY issue a LOGIN
request prior to sending any presence or IM commands in order to
authenticate itself as an authoritative host in the initiating
domain. The domain MUST be presented with the domain-header.
If the authentication process is not successful the TCP connection
MUST be dropped. The LOGIN request MAY be preceded by the STARTTLS
request when the implementations support TLS for a secure connection.
Any other requests that are received before the authentication
completed MUST receive an "Unauthorized" response.
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The authentication process is not necessarily completed in a single
request/response pair, but it can be fulfilled in a sequence of the
request/response pairs. The auth-state-header MUST be used to
indicate the state of the authentication process.
The command-body in the LOGIN request and its response MAY carry the
authentication information for the respective SASL mechanism.
See section 9 for the details of authentication procedures.
Return Codes:
100 Authentication Continued: This response may possibly carry a
command-body with information pertaining to the SASL challenge, and
a SASL-mechanism-header specifying the SASL mechanism supported by
the server. The originator needs to send other LOGIN command, with
auth-state-header as "continue", and the response to the challenge
in the command-body.
200 OK: The sender is authenticated and the connection may be used
to transport further commands.
406 Authorization Failed: The operation failed to authenticate the
connection. No further commands are allowed and the receiver MUST
terminate the connection.
409 Already Authenticated: This is returned if a LOGIN command has
already succeeded.
7.3.2. STARTTLS - Secuire Connection Setup
Headers: Request Response
---------------------------------------------------------------
none none
---------------------------------------------------------------
A server MAY issue STARTTLS request to upgrade a TCP connection to a
TLS [TLS] enabled one. Implementations that support TLS MAY issue a
STARTTLS request prior to issuing any other requests.
Once the client credentials are successfully exchanged using TLS
negotiation, the "EXTERNAL" SASL mechanism MAY be used in the
subsequent LOGIN process. The "PLAIN" SASL mechanism SHOULD NOT be
used if the STARTTLS upgrading process fails to establish a fully
strong encryption layer.
The Request and the response MUST NOT carry a command-body.
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Return Codes:
200 OK: The TLS negotiation should start. Once a STARTTLS command
issued, the initiator MUST NOT issue further requests until a
server response is received and the TLS negotiation is completed.
501 Not Implemented: TLS is not implemented and thus the client
must authenticate itself using the LOGIN method.
7.3.3. LOGOUT - Connection Shutdown
Headers: Request
---------------------------------------------------------------
none
---------------------------------------------------------------
The receiver of the LOGOUT command MUST NOT send any response.
7.3.4. PING - Testing a connectionG
Headers: Request
---------------------------------------------------------------
none
---------------------------------------------------------------
When a peer in a connection wants to verify if the connection is
alive, it may send a PING command. No response is expected from the
other peer.
A successful transmission of a PING does not guarantee its reception
at the other end, nor does it verify that all is well with its peer.
However the transmission of the PING may provoke an error, and
thereby causing the sending peer to realize there is a problem with
the connection. If this happens the USER AGENT or server assumes an
implicit LOGOUT command.
7.3.5. VERIFYSERVER - Verifying a server's authority
Headers: Request Response
---------------------------------------------------------------
server-address-header server-address-header
---------------------------------------------------------------
As described in section 13.2, when a server needs to verify whether
another server (known through its IP address) belongs to a given
domain, it performs one or more DNS lookups. Large domains with a
significant amount of servers might not be able to publish every
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entry for every server, due to DNS limitations. Thus a DNS lookup
might not be sufficient to determine whether a given server belongs
to a given domain.
If it is not possible to verify the domain of a server through a DNS
lookup, a VERIFYSERVER command can be issued.
The VERIFYSERVER MAY be issued in a new TCP connection, without
previous LOGIN. The verifying server will issue the command to any
of the addresses returned in the DNS lookup.
The server-address-header specifies the IP address of the server that
needs verification.
The response MUST NOT have a command body.
Return Codes:
200 OK: the server does belong to that domain.
403 Resource Not Found: the server does not belong to this domain.
8. Response Codes
The policy for assigning response codes follows the convention used
in HTTP/1.1 [HTTP1.1].
o 1xx: Informational - Request received, continuing process
o 2xx: Success - The action was successfully received, understood,
and accepted
o 3xx: Redirection - Further action must be taken in order to
complete the request
o 4xx: Request Error - The request contains bad syntax or cannot be
fulfilled
o 5xx: Server Error - The server failed to fulfill an apparently
valid request
100 Authentication Continued
The request for authentication has been accepted and the
authentication process is continued.
101 Unknown Delivery Status
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The server was unable to determine that the message was
successfully delivered to an INSTANT INBOX or that the transmission
failed. This could be because the message was delivered on a best-
effort basis, or it was delivered to an "offline" message store.
200 OK
The request has been successfully processed.
201 Duration Adjusted
The SUBSCRIPTION was placed successfully, yet its duration was not
acceptable to the server. A new duration was set and this was
indicated in the duration-header of the response.
300 Redirect
The server was unable to deal with the request and instructs the
caller to reconnect to a different server and reissue the operation
there.
400 Bad Request
The request could not be understood by the server due to malformed
syntax of the headers or malformed content. The requesting host
SHOULD NOT repeat the request without modifications.
401 Unauthorized
The request requires authentication. If received this response,
the requesting host MUST authenticate itself through the LOGIN
request.
402 Forbidden
The server understood the request, but it has not been authorized.
403 Resource Not Found
The specified resource was not found at the server.
404 Subscription Not Found
The SUBSCRIPTION specified in the Subscription-ID header was not
found at the resource.
406 Authentication Failed
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The authentication process has failed. The reason for it is one of
the following:
o The authentication process using the specified SASL-Mechanism
failed.
o The LOGIN request specifies an inappropriate SASL Mechanism.
o In the midst of the authentication process, the requester tries to
start another authentication process by specifying 'Auth-State:
init'.
407 Timeout
The server timed-out after waiting for a response from another
client or server.
408 Inbox Is Closed
The INSTANT INBOX is not currently accepting messages.
409 Already Authenticated
The connection was authenticated previously through a LOGIN
command.
410 Astrength Too Weak
The command was rejected because the server requires a higher level
of security and this could not be provided.
500 Internal Server Error
The request has not been fulfilled because of the error internal to
the server.
501 Not Implemented
The server does not support the functionality required to fulfill
the request. This response is typically returned when the server
has received a request of the services it does not provide.
502 Bad Gateway
The server, while acting as a gateway or proxy, received an invalid
response from the other PRIM or non-PRIM server it accessed in
attempting to fulfill the request.
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503 Version Not Supported
The server or client does not support the specified protocol
version used for the request.
504 Gateway Timeout
The server, while acting as a gateway or proxy, did not receive a
timely response from the other PRIM or non-PRIM server it accessed
in attempting to fulfill the request.
505 Too Many Subscriptions
The SUBSCRIBE request has not been fulfilled because the request
exceeds the specified maximum number of SUBSCRIPTIONS at the
resource. When this status code is received, the client SHOULD NOT
retry the SUBSCRIPTION immediately.
9. Authentication
PRIM implements security on a per-connection basis: each connection
end-point is authenticated in order to establish the PRESENTITIES
and INBOXES on behalf of which that end-point can communicate.
After authentication succeeds, the other end-point will accept
requests pertaining to those PRESENTITIES or INBOXES, and direct
requests to them over that connection.
9.1. Server-Server Authentication
When a server establishes a connection to another server, that
connection end-point can be authorized to communicate on behalf of
multiple PRESENTITIES or INBOXES. This is usually performed by
authenticating the end-point as a valid host of the initiating
domain.
The connection end-points MAY use a LOGIN command for the
authentication. But, if two end-points have authenticated each other
with an out-of-band method (e.g. TLS) or they have enough knowledge
about the other end-point for their purpose (e.g. IP address), it MAY
NOT use such a particular command. If the connection uses TLS, then
the domains served by each end-point are established in the
beginning, through the certificates provided.
Another type of authorization can take place throughout the duration
of the connection. Each end-point will establish that a domain is
being served by the other end-point when the first request pertaining
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to that domain is received. This can happen more than once per
connection.
Verification that a given server is responsible for a given domain is
done by performing a name resolution (as described in section 7.2).
It is possible that due to DNS limitations, in the case of a domain
with a large number of servers, only partial DNS records are
advertised. Thus, the address of the server initiating the
connection may not be in the records received. In this case a
VERIFYSERVER method is performed to establish whether the initiating
server has authority over the corresponding domain. This is
described in Section 10.5.
9.2. Authentication Using LOGIN
When a server establishes a connection to a server, it MAY issue a
LOGIN command to authenticate itself as a valid host representing its
domain. The LOGIN authentication procedure in PRIM uses SASL [SASL].
The LOGIN request and response MUST include a SASL-Mechanism header
field so that the end-points could negotiate the SASL mechanism to be
used. As SASL mechanisms, every PRIM implementation MUST implement
PLAIN [SASL-PLAIN] and is RECOMMENDED to implement CRAM-MD5 [CRAM-
MD5], and EXTERNAL [SASL]. It MAY also implement other mechanisms as
needed.
The LOGIN authentication procedure is sketched as follows;
(1) The initial LOGIN request
A server issues a LOGIN request including the Auth-State header
with the value "init". It MUST also contain the Domain header
specifying the initiating domain and the SASL-Mechanism header
whose value is a comma-separated list of SASL mechanisms the
initiating host is capable to use in the descending order of
preference.
[Example]
LOGIN PRIM/1.0 0224 0
Domain: prim.fujitsu.com
Auth-State: init
SASL-Mech: CRAM-MD5,PLAIN
If the LOGIN request is acceptable, the target server SHOULD
respond with '100 Authentication Continued' response. It MUST
contains the SASL-Mechanism header with the value of at least one
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selected SASL mechanism by the server. If a challenge-response
mechanism is selected, the response MUST contain a challenge data
in the body.
PRIM/1.0 0224 48 100 Authentication Continued
Domain: prim.fujitsu.com
Auth-State: init
SASL-Mech: CRAM-MD5
<20010226095208.1018677043.foo1.bar.fujitsu.com>
(2) The subsequent LOGIN requests
If an initiating server receives a '100 Authentication Continued'
response to the initial LOGIN request, it SHOULD try another LOGIN
request with the header 'Auth-State: continue'. This LOGIN request
MUST contain the SASL-Mechanism header with the single value of
selected SASL mechanism.
The LOGIN request MAY contain the domain's authentication
information in the body required by the selected mechanism. Details
in the case of CRAM-MD5, PLAIN, and EXTERNAL are described in the
following subsections.
If the LOGIN request is validated, the target server respond with a
'200 OK' response. If the same PRINCIPAL is already authenticated
by a preceding LOGIN procedure, the server MAY respond with a '409
Already Authenticated'. Otherwise, a '406 Authentication Failed'
response SHOULD be returned to the USER AGENT. In this case, the
USER AGENT MUST NOT send any other request commands in this
connection.
(2-a) CRAM-MD5
The USER AGENT calculates the response data using the keyed MD5
algorithm [KEYED-MD5] where the key is the shared pass phrase and
the text is the challenge data. Then, it sends the hexadecimal
string of the response octets prepended by the user name and CRLF
in the body of the LOGIN request.
[Example]
LOGIN PRIM/1.0 0225 50
Domain: prim.fujitsu.com
Auth-State: continue
SASL-Mech: CRAM-MD5
Content-Type: text/plain
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INTERNET DRAFT PRIM Specification March 2001
prim.fujitsu.com
106d12b16fc323dc2f3d19b587f8d0ff
(2-b) PLAIN
The PLAIN mechanism SHOULD be used only on a fully secured
connection, such as one already encrypted with TLS. In this case,
the body part of the LOGIN request contains the user name and the
pass phrase in a plain text separated by CRLF.
[Example]
LOGIN PRIM/1.0 84505230 27
Domain: prim.fujitsu.com
Auth-State: continue
SASL-Mech: PLAIN
Content-Type: text/plain
prim.fujitsu.com
hi there!
(2-c) EXTERNAL
The EXTERNAL mechanism is intended to be used in the case that the
PRINCIPAL has been already authenticated with some external
authentication method, such as TLS mutual authentication. The LOGIN
command using this mechanism contains nothing in the body.
10. Presence Information Data Format (PIDF)
PRIM adopts CPIM Presence Information Data Format [CPIM-PIDF] as
its presence data format. This brings CPIM conformance to PRIM
with its native presence data format. The content-type
"application/cpim-pidf+xml" is defined in that specification.
See the reference for detailed information.
11. IM Format
INSTANT MESSAGES are opaque payloads transferred by SEND commands
tagged by a MIME [MIME] content type.
A SEND command MUST contain a Content-Type header which specifies
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INTERNET DRAFT PRIM Specification March 2001
the content type of the payload. It MAY contain any proper MIME
header which may not be defined here.
For the CPIM conformance, A USER AGENT MUST understand and generate
messages of the content type 'message/cpim'[CPIM-MSG]. In
particular, a USER AGENT MUST generate an INSTANT MESSAGE of the
type 'message/cpim' if it sends the message to other domains which
do not or may not understand PRIM. The correspondence between the
PRIM and CPIM message format is described in Section 17.
The PRIM servers MUST forward the message as is when the message is
relayed to the clients or other servers. That is, the servers MUST
NOT delete or modify any header which appears in the command.
12. Security Considerations
There exists many kind of security threats in the Presence / Instant
Messaging services and applications as described in the IMPP
Requirements [RFC 1778] and the CPIM document [CPIM].
PRIM specifies mechanisms to achieve connection security and to
realize access control including presence publication control.
The future PRIM specifications will conform to the expected CPIM data
formats for secure and interoperable Presence information and IM
exchanges [CPIM,CPIM-MSG]. It will acquire the message level
security such as end-to-end confidentiality and integrity.
13. References
[CPIM] D. Crocker et al., "A Common Profile for Instant Messaging
(CPIM)", draft-ietf-impp-cpim-01.txt, Work in Progress.
[CPIM-MSG] D. Atkins and G. Klyne, "Common Presence and Instant
Messaging Message Format", draft-ietf-impp-cpim-msgfmt-00.txt,
Work in Progress.
[CRAM-MD5] J.Klensin, R.Catoe and P. Krumviede, "IMAP/POP AUTHorize
Extension for Simple Challenge/Response", RFC 2195, September 997.
[HTTP1.1] R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter,
P. Leach, and T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999
Mazzoldi et al. [Page 37]
INTERNET DRAFT PRIM Specification March 2001
[MIME] Multipurpose Internet Mail Extensions. See RFC 822, RFC 2045,
RFC 2046, RFC 2047, RFC 2048, and RFC 2049.
[OpenPGP] J. Callas, etc., "OpenPGP Message Format", RFC2440,
November 1998.
[RFC822] Crocker, D., "Standard for the format of ARPA Internet text
messages", RFC 822, STD 11, Aug 1982.
[RFC1123] R. Braden, "Requirements for Internet Hosts -- Application
and Support", RFC 1123, October 1989
[RFC1738] T. Berners-Lee, L. Masinter, M. McCahill, "Uniform Resource
Locators", RFC 1738, December 1994.
[RFC2778] M. Day, J. Rosenberg, H. Sugano, "A Model for Presence and
Instant Messaging", RFC 2778, February 2000.
[RFC2779] M.Day, S.Aggarwal, G.Mohr, and J.Vincent, "Instant
Messaging / Presence Protocol Requirements", RFC 2779, February 2000.
[SASL] J. Myers, "Simple Authentication and Security Layer (SASL)",
RFC2222, October 1997.
[SASL-PLAIN] C. Newman, "Using TLS with IMAP, POP3 and ACAP",
RFC2595, June 1999.
[SMIME] P. Hoffman, Ed, "S/MIME Version 3 Message Specification",
RFC2633, June 1999.
[TLS] T.Dierks, and C. Allen, "The TLS Protocol Version 1.0",
RFC2246, January 1999.
[URI] T. Berners-Lee, R. Fielding, L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC2396, August 1998.
[XML] Extensible Mark Up Language. A W3C recommendation. See
http://www.w3.org/TR/1998/REC-xml-19980210 for the 10 February 1998
version.
14. Acknowledgements
The authors greatly appreciate helpful comments from John Stracke and
Harald Alvestrand.
15. Author's Addresses
Mazzoldi et al. [Page 38]
INTERNET DRAFT PRIM Specification March 2001
F. Mazzoldi
flo@personity.com
Personity, Inc.
4516 Henry Street, Suite 113
Pittsburgh PA 15213
USA
A. Diacakis
thanos@personity.com
Personity, Inc.
4516 Henry Street, Suite 113
Pittsburgh, PA 15213
USA
S. Fujimoto
shingo_fujimoto@jp.fujitsu.com
Fujitsu Laboratories Ltd.
64, Nishiwaki
Ohkubo-cho
Akashi 674
Japan
G. Hudson
ghudson@mit.edu
Massachusetts Institue of Technology
Cambridge, MA 02139
USA
J. D. Ramsdell
ramsdell@mitre.org
The MITRE Corporation
202 Burlington Road
Bedford, MA 01730-1420
USA
H. Sugano
sugano.h@jp.fujitsu.com
Fujitsu Laboratories Ltd.
64, Nishiwaki
Ohkubo-cho
Akashi 674
Japan
16. Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
Mazzoldi et al. [Page 39]
INTERNET DRAFT PRIM Specification March 2001
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC editor function is currently provided by the
Internet Society.
Mazzoldi et al. [Page 40]
