Internet DRAFT - draft-myers-acap-spec
draft-myers-acap-spec
HTTP/1.1 200 OK
Date: Tue, 09 Apr 2002 10:23:18 GMT
Server: Apache/1.3.20 (Unix)
Last-Modified: Mon, 25 Nov 1996 20:19:00 GMT
ETag: "3ddee3-16a12-3299ff34"
Accept-Ranges: bytes
Content-Length: 92690
Connection: close
Content-Type: text/plain
Network Working Group J. G. Myers
Internet Draft: ACAP Carnegie Mellon
Document: internet-drafts/draft-myers-acap-spec-01.txt November 1996
Expire in six months
ACAP -- Application Configuration Access Protocol
Status of this Memo
This document is an Internet Draft. 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. Internet Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet
Drafts as reference material or to cite them other than as a
``working draft'' or ``work in progress``.
To learn the current status of any Internet-Draft, please check the
1id-abstracts.txt listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net, nic.nordu.net, ftp.isi.edu, or
munnari.oz.au.
This document suggests a proposed protocol for the Internet
community, and requests discussion and suggestions for improvements.
Distribution of this draft is unlimited.
The protocol discussed in this document is experimental and subject
to change. Persons planning on either implementing or using this
protocol are STRONGLY URGED to get in touch with the author before
embarking on such a project.
Abstract
The Application Configuration Access Protocol (ACAP) is designed to
support remote storage and access of program option, configuration
and preference information.
Myers [Page i]
Internet DRAFT ACAP November 25, 1996
ACAP Protocol Specification
1. Conventions Used in this Document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
The protocol syntax specification uses the Augmented Backus-Naur Form
(ABNF) notation as specified in [RFC-822] with one exception; the
delimiter used with the "#" construct is a single space (SPACE) and
not one or more commas.
The "::+" extension to the ABNF notation is used to allow
nonterminals to be defined as a set of alternatives, each alternative
being defined in a separate lines. The sequence of productions:
a ::+ b
a ::+ c
a ::+ d
is equivalent to
a ::= (b) / (c) / (d)
2. Protocol Overview
2.1. Link Level
The ACAP protocol assumes a reliable data stream such as provided by
TCP. When TCP is used, an ACAP server listens on port XXXX.
2.2. Commands and Responses
An ACAP session consists of the establishment of a client/server
connection, an initial greeting from the server, and client/server
interactions. These client/server interactions consist of a client
command, server data, and a server completion result response.
All interactions transmitted by client and server are in the form of
lines; that is, strings that end with a CRLF. The protocol receiver
of an ACAP client or server is either reading a line, or is reading a
sequence of octets with a known count followed by a line. Both
clients and servers must be capable of handling lines of arbitrary
length.
Myers [Page 1]
Internet DRAFT ACAP November 25, 1996
2.2.1. Client Protocol Sender and Server Protocol Receiver
The client command begins an operation. Each client command is
prefixed with a identifier (typically a short alphanumeric string,
e.g. A0001, A0002, etc.) called a "tag". A different tag is
generated by the client for each command.
There are two cases in which a line from the client does not
represent a complete command. In one case, a command argument is
quoted with an octet count (see the description of literal in section
XXXX); in the other case, the command arguments require server
feedback (see the AUTHENTICATE command). In some of these cases, the
server sends a command continuation request response if it is ready
for the next part of the command. This response is prefixed with the
token "+".
Note: If, instead, the server detected an error in the
command, it sends a BAD completion response with tag
matching the command (as described below) to reject the
command and prevent the client from sending any more of the
command.
It is also possible for the server to send a completion or
intermediate response for some other command (if multiple
commands are in progress), or untagged data. In either
case, the command continuation request is still pending;
the client takes the appropriate action for the response,
and reads another response from the server.
The protocol receiver of an ACAP server reads a command line from the
client, parses the command and its arguments, and transmits server
data and a server command completion result response.
2.2.2. Server Protocol Sender and Client Protocol Receiver
Data transmitted by the server to the client come in four forms:
command continuation requests, command completion results,
intermediate responses, and untagged responses.
A command completion request is prefixed with the token "+".
A command completion result response indicates the success or failure
of the operation. It is tagged with the same tag as the client
command which began the operation. Thus, if more than one command is
in progress, the tag in a server completion response identifies the
command to which the response applies. There are three possible
server completion responses: OK (indicating success), NO (indicating
Myers [Page 2]
Internet DRAFT ACAP November 25, 1996
failure), or BAD (indicating protocol error such as unrecognized
command or command syntax error).
An intermediate response returns data which can only be interpreted
within the context of a command in progress. It is tagged with the
same tag as the client command which began the operation. Thus, if
more than one command is in progress, the tag in an intermediate
response identifies the command to which the response applies. A
tagged response other than "OK", "NO", or "BAD" is an intermediate
response.
An untagged response returns data or status messages which may be
interpreted outside the context of a command in progress. It is
prefixed with the token "*". Untagged data may be sent as a result
of a client command, or may be sent unilaterally by the server.
There is no syntactic difference between untagged data that resulted
from a specific command and untagged data that were sent
unilaterally.
The protocol receiver of an ACAP client reads a response line from
the server. It then takes action on the response based upon the
first token of the response, which may be a tag, a "*", or a "+" as
described above.
A client MUST be prepared to accept any server response at all times.
This includes untagged data that it may not have requested.
This topic is discussed in greater detail in the Server Responses
section.
2.3. State and Flow Diagram
An ACAP server is in one of three states. Most commands are valid in
only certain states. It is a protocol error for the client to
attempt a command while the server is in an inappropriate state for
that command. In this case, a server will respond with a BAD command
completion result.
2.3.1. Non-Authenticated State
In non-authenticated state, the user must supply authentication
credentials before most commands will be permitted. This state is
entered when a connection starts.
Myers [Page 3]
Internet DRAFT ACAP November 25, 1996
2.3.2. Authenticated State
In authenticated state, the user is authenticated and most commands
will be permitted. This state is entered when acceptable
authentication credentials have been provided.
2.3.3. Logout State
In logout state, the session is being terminated, and the server will
close the connection. This state can be entered as a result of a
client request or by unilateral server decision.
+--------------------------------------+
|initial connection and server greeting|
+--------------------------------------+
|| (1) || (2)
VV ||
+-----------------+ ||
|non-authenticated| ||
+-----------------+ ||
|| (4) || (3) ||
|| VV ||
|| +----------------+ ||
|| | authenticated | ||
|| +----------------+ ||
|| || (4) ||
VV VV VV
+--------------------------------------+
| logout and close connection |
+--------------------------------------+
(1) connection (ACAP greeting)
(2) rejected connection (BYE greeting)
(3) successful LOGIN or AUTHENTICATE command
(4) LOGOUT command, server shutdown, or connection closed
2.4. Data Formats
ACAP uses textual commands and responses. Data in ACAP can be in one
of several forms: atom, number, string, parenthesized list, or NIL.
2.4.1. Atom
An atom consists of one to 1024 non-special characters.
Myers [Page 4]
Internet DRAFT ACAP November 25, 1996
2.4.2. Number
A number consists of one or more digit characters, and represents a
numeric value.
2.4.3. String
A string is in one of two forms: literal and quoted string. The
literal form is the general form of string. The quoted string form
is an alternative that avoids the overhead of processing a literal at
the cost of restrictions of what may be in a quoted string.
A literal is a sequence of zero or more octets (including CR and LF),
prefix-quoted with an octet count in the form of an open brace ("{"),
the number of octets, close brace ("}"), and CRLF. In the case of
literals transmitted from server to client, the CRLF is immediately
followed by the octet data.
There are two forms of literals transmitted from client to server.
The form where the open brace ("{") and number of octets is
immediately followed by a close brace ("}") and CRLF is called a
synchronizing literal. When sending a synchronizing literal, the
client must wait to receive a command continuation request (described
later in this document) before sending the octet data (and the
remainder of the command). The other form of literal, the non-
synchronizing literal, is used to transmit a string from client to
server without waiting for a command continuation request. The non-
synchronizing literal differs from the synchronizing literal by
having a plus ("+") between the number of octets and the close brace
("}") and by having the octet data immediately following the CRLF.
A quoted string is a sequence of zero to 1024 7-bit characters,
excluding CR, LF, double quote (<">), or backslash ("\") with double
quote (<">) characters at each end.
The empty string is respresented as "" (a quoted string with zero
characters between double quotes), as {0} followed by CRLF (a
synchronizing literal with an octet count of 0), or as {0+} followed
by a CRLF (a non-synchronizing literal with an octet count of 0).
Note: Even if the octet count is 0, a client transmitting a
synchronizing literal must wait to receive a command
continuation request.
Myers [Page 5]
Internet DRAFT ACAP November 25, 1996
2.4.3.1. 8-bit and Binary Strings
ACAP implementations MAY transmit 8-bit octets in literals. Except
in the values of attributes whose names end with ".bin", these octets
are interpreted as UTF-8 character sequences [UTF-8]. NUL octets are
only permitted in the values of attributes whose names end with
".bin". Servers SHOULD verify any non-binary string sent by the
client has valid UTF-8 syntax before storing it.
2.5. Operational Considerations
2.5.1. Untagged Status Updates
At any time, a server can send data that the client did not request.
2.5.2. Response when no Command in Progress
Server implementations are permitted to send an untagged response
while there is no command in progress. Server implementations that
send such responses MUST deal with flow control considerations.
Specifically, they must either (1) verify that the size of the data
does not exceed the underlying transport's available window size, or
(2) use non-blocking writes.
2.5.3. Autologout Timer
If a server has an inactivity autologout timer, that timer MUST be of
at least 30 minutes' duration. The receipt of ANY command from the
client during that interval should suffice to reset the autologout
timer.
2.5.4. Multiple Commands in Progress
The client is not required to wait for the completion result response
of a command before sending another command, subject to flow control
constraints on the underlying data stream. Similarly, a server is
not required to process a command to completion before beginning
processing of the next command, unless an ambiguity would result
because of a command that would affect the results of other commands.
If there is such an ambiguity, the server executes commands to
completion in the order given by the client.
Myers [Page 6]
Internet DRAFT ACAP November 25, 1996
2.6. Datasets
The primary data structure in ACAP is the "dataset", which is a named
set of entries. Datasets are named hierarchically, with each
component of the name being preceeded by a slash ("/") and containing
one or more UTF-8 characters (other than slash).
Each entry in a dataset is a set of attribute/value pairs. Each
attribute is a hierarchical name in UTF-8, with each component of the
name being separated with a period ("."). Each attribute/value pair
may have additional metadata, this is described in section XXX.
There must be exactly one "name" attribute, whose value is unique
amongst all entries in the dataset. [OPEN ISSUE: consensus is against
using "name" for the distinguished attribute. Replacement has not
been agreed on.]
Entries in a dataset are ordered in a server-determined manner.
[OPEN ISSUE]
The value is a string containing one or more octets. The semantics
of a value are defined by the specification of its attribute. Values
of attributes ending in ".bin" contain arbitrary data. Values of
other attributes are textual and are interpreted as a sequence of
characters encoded in UTF-8.
2.7. Predefined Attributes
Attribute names which do not contain a dot (".") are reserved for
standardized attributes which have meaning in any dataset. The
following attributes are defined by the ACAP protocol.
name Contains the name of the entry.
modtime
Contains the date and time, in UTC, any value in the entry was
last modified. This value is automatically updated by the
server and may not be directly modified by the client.
The value consists of 14 or more us-ascii digits. The first
four indicate the year, the next two indicate the month, the
next two indicate the day of month, the next two indicate the
hour (0 - 23), the next two indicate the minute, and the next
two indicate the second. Any further digits indicate fractions
of a second.
The time, particularly fractions of a second, need not be
accurate. It is required, however, that any two entries in a
dataset changed by successive modifications have strictly
Myers [Page 7]
Internet DRAFT ACAP November 25, 1996
ascending modtime values.
createtime
The modtime of the operation that created the entry.
2.8. Attribute metadata
Each attribute/value pair may have additional metadata associated
with it. For completeness, the attribute and value themselves are
defined as metadata. The defined items of metadata associated with
an attribute/value pair are:
attribute
The attribute name. Read-only.
valueThe value.
value<ORIGIN.SIZE>
A substring of the value. ORIGIN is specified as a non-negative
decimal number indicating the octet position of the first desired
octet. An ORIGIN of 0 specifies the first octet of the value.
SIZE is specified as a positive, nonzero decimal number, specifying
the maximum number of octets desired. Read-only.
size The length of the value, in octets. Read-only.
acl The access control list for the attribute/value pair, if one
exists. If the attribute/value pair does not have an ACL, the null
string. Read-only [OPEN ISSUE: allow writing?]
myrights
The set of rights that the client has to the attribute/value pair.
Read-only.
Additional items of metadata may be defined in extensions to this
protocol. Servers must respond to queries of unrecognized metadata by
returning the null string [OPEN ISSUE: return error instead?].
2.9. Child Dataset Attributes
Attributes names starting with the "dataset." prefix are reserved for
standardized attributes containing information about child datasets.
The "dataset." attributes on an entry describe the child dataset with
the same relative name as the entry. For example, if the dataset
"/foo/bar" has an entry "baz" with "dataset." attributes, those
attributes pertain to the "/foo/bar/baz" dataset.
[TODO: flesh out what these are. Tentative list follows.]
Myers [Page 8]
Internet DRAFT ACAP November 25, 1996
dataset.exists "y" ; Non-empty means sub-dataset exists on this server
dataset.referlist "acap://acap3.andrew.cmu.edu/foo/bar"
; attempt to access generates [REFER] special
; information token with following contents.
; [OPEN ISSUE: multiple urls?]
; dataset.exists and dataset.referlist mutually exclusive.
; [OPEN ISSUE: Combine them?]
dataset.shadows "/foo/bar"
; What this dataset shadows
; Only meaningful if dataset.exists non-empty.
; [OPEN ISSUE: Combine?]
dataset.subscription "show"
; more limited than for mailbox lists
Myers [Page 9]
Internet DRAFT ACAP November 25, 1996
3. Protocol Specification
ACAP commands and responses are described in this section. Commands
are organized first by the state in which the command is permitted,
then by a general category of command type.
Command arguments, identified by "Arguments:" in the command
descriptions below, are described by function, not by syntax. The
precise syntax of command arguments is described in the Formal Syntax
section.
Some commands cause specific server data to be returned; these are
identified by "Data:" in the command descriptions below. See the
response descriptions in the Responses section for information on
these responses, and the Formal Syntax section for the precise syntax
of these responses. It is possible for server data to be transmitted
as a result of any command; thus, commands that do not specifically
require server data specify "no specific data for this command"
instead of "none".
The "Result:" in the command description refers to the possible
tagged status responses to a command, and any special interpretation
of these status responses.
3.1. Initial Connection
Upon session startup, the server sends one of two untagged responses:
ACAP or BYE. The untagged BYE response is described in section XXX.
3.1.1. ACAP Response
Data: capability list
The untagged ACAP response indicates the session is ready to
accept commands and contains a space-separated listing of
capabilities that the server supports. Each capability is an atom
name, possibly followed by a string argument in parenthesis.
ACAP capability names MUST be registered with IANA. [OPEN ISSUE:
ESTABLISH REGISTRY].
Client implementations SHOULD NOT require any capability name, and
MUST ignore any unknown capability names.
[TODO: initial capability list: IMPLEMENTATION, CONTEXTLIMIT,
ORDERINGS]
Myers [Page 10]
Internet DRAFT ACAP November 25, 1996
Example: S: * ACAP IMPLEMENTATION("ACME v3.5")
3.2. Any State
The following commands and responses are valid in any state.
3.2.1. NOOP Command
Arguments: none
Data: no specific data for this command (but see below)
Result: OK - noop completed
BAD - command unknown or arguments invalid
The NOOP command always succeeds. It does nothing.
Since any command can return a status update as untagged data, the
NOOP command can be used as a periodic poll for status updates
during a period of inactivity. The NOOP command can also be used
to reset any inactivity autologout timer on the server.
Example: C: a002 NOOP
S: a002 OK NOOP completed
3.2.2. LOGOUT Command
Arguments: none
Data: mandatory untagged response: BYE
Result: OK - logout completed
BAD - command unknown or arguments invalid
The LOGOUT command informs the server that the client is done with
the session. The server must send a BYE untagged response before
the (tagged) OK response, and then close the network connection.
Example: C: A023 LOGOUT
S: * BYE ACAP Server logging out
S: A023 OK LOGOUT completed
(Server and client then close the connection)
Myers [Page 11]
Internet DRAFT ACAP November 25, 1996
3.2.3. OK Response
Data: optional response code
human-readable text
The OK response indicates an information message from the server.
When tagged, it indicates successful completion of the associated
command. The human-readable text may be presented to the user as
an information message. The untagged form indicates an
information-only message; the nature of the information may be
indicated by a response code.
Example: S: * OK [ALERT] System shutdown in 10 minutes
3.2.4. NO Response
Data: optional response code
human-readable text
The NO response indicates an operational error message from the
server. When tagged, it indicates unsuccessful completion of the
associated command. The untagged form indicates a warning; the
command may still complete successfully. The human-readable text
describes the condition.
Example: C: A001 LOGIN fred secret
S: * NO [ALERT] Dataet "/addressbook/fred" is at 98% of
quota [TODO-FIX]
S: A001 OK LOGIN
...
C: A222 STORE /mailboxes "comp.mail.misc"
mailbox.creation-time "19951206103412"
S: A222 NO Permission denied
3.2.5. BAD Response
Data: optional response code
human-readable text
The BAD response indicates an error message from the server. When
tagged, it reports a protocol-level error in the client's command;
the tag indicates the command that caused the error. The untagged
form indicates a protocol-level error for which the associated
command can not be determined; it may also indicate an internal
Myers [Page 12]
Internet DRAFT ACAP November 25, 1996
server failure. The human-readable text describes the condition.
Example: C: ...empty line...
S: * BAD Empty command line
C: A443 BLURDYBLOOP
S: A443 BAD Unknown command
3.2.6. BYE Response
Data: optional response code
human-readable text
The untagged BYE response indicates that the server is about to
close the connection. The human-readable text may be displayed to
the user in a status report by the client. The BYE response may
be sent as part of a normal logout sequence, or as a panic
shutdown announcement by the server. It is also used by some
server implementations as an announcement of an inactivity
autologout.
This response is also used as one of two possible greetings at
session startup. It indicates that the server is not willing to
accept a session from this client.
Example: S: * BYE Autologout; idle for too long
3.3. Non-Authenticated State
In non-authenticated state, the AUTHENTICATE or LOGIN command
establishes authentication and enter authenticated state. The
AUTHENTICATE command provides a general mechanism for a variety of
authentication techniques, whereas the LOGIN command uses the
traditional user name and plaintext password pair.
Server implementations may allow non-authenticated access to certain
information. The convention is to use a LOGIN command with the
userid "anonymous". A password is required. It is implementation-
dependent what requirements, if any, are placed on the password and
what access restrictions are placed on anonymous users.
Once authenticated (including as anonymous), it is not possible to
re-enter non-authenticated state.
In addition to the universal commands (NOOP and LOGOUT), the
following commands are valid in non-authenticated state:
AUTHENTICATE and LOGIN.
Myers [Page 13]
Internet DRAFT ACAP November 25, 1996
3.3.1. AUTHENTICATE Command
Arguments: SASL mechanism name
optional initial response
Data: continuation data may be requested
Result: OK - authenticate completed, now in authenticated state
NO - authenticate failure: unsupported authentication
mechanism, credentials rejected
BAD - command unknown or arguments invalid,
authentication exchange cancelled
The AUTHENTICATE command indicates an authentication mechanism to
the server. If the server supports the requested authentication
mechanism, it performs an authentication protocol exchange to
authenticate and identify the user. Optionally, it also
negotiates a security layer for subsequent protocol interactions.
If the requested authentication mechanism is not supported, the
server rejects the AUTHENTICATE command by sending a tagged NO
response.
[OPEN ISSUE: Change from base64 encoded literals to using binary
literals?]
The authentication protocol exchange consists of a series of
server challenges and client answers that are specific to the
authentication mechanism. A server challenge consists of a
command continuation request response with the "+" token followed
by a BASE64 encoded string. The client answer consists of a line
consisting of a BASE64 encoded string. If the client wishes to
cancel an authentication exchange, it should issue a line with a
single "*". If the server receives such an answer, it must reject
the AUTHENTICATE command by sending a tagged BAD response.
The optional initial-response argument to the AUTHENTICATE command
is used to save a round trip when using authentication mechanisms
that are defined to send no data in the initial challenge. When
the initial-response argument is used with such a mechanism, the
initial empty challenge is not sent to the client and the server
uses the data in the initial-response argument as if it were sent
in response to the empty challenge. If the initial-response
argument to the AUTHENTICATE command is used with a mechanism
that sends data in the initial challenge, the server rejects the
AUTHENTICATE command by sending a tagged NO response.
The service name specified by this protocol's profile of SASL is
"acap".
Myers [Page 14]
Internet DRAFT ACAP November 25, 1996
If a security layer is negotiated through the SASL authentication
exchange, it takes effect immediately following the CRLF that
concludes the authentication exchange for the client, and the CRLF
of the tagged OK response for the server.
The server is not required to support any particular
authentication mechanism, nor are authentication mechanisms
required to support any protection mechanisms. If an AUTHENTICATE
command fails with a NO response, the client may try another
authentication mechanism by issuing another AUTHENTICATE command,
or may attempt to authenticate by using the LOGIN command. In
other words, the client may request authentication types in
decreasing order of preference, with the LOGIN command as a last
resort.
Example: S: * ACAP IMPLEMENTATION("Blorfysoft v3.5")
AUTH(KERBEROS_V4)
C: A001 AUTHENTICATE KERBEROS_V4
S: + AmFYig==
C: BAcAQU5EUkVXLkNNVS5FRFUAOCAsho84kLN3/IJmrMG+25a4DT
+nZImJjnTNHJUtxAA+o0KPKfHEcAFs9a3CL5Oebe/ydHJUwYFd
WwuQ1MWiy6IesKvjL5rL9WjXUb9MwT9bpObYLGOKi1Qh
S: + or//EoAADZI=
C: DiAF5A4gA+oOIALuBkAAmw==
S: A001 OK Kerberos V4 authentication successful
Note: the line breaks in the first client answer are for
editorial clarity and are not in real authenticators.
3.3.2. LOGIN Command
Arguments: user name
password
Data: no specific data for this command
Result: OK - login completed, now in authenticated state
NO - login failure: user name or password rejected
BAD - command unknown or arguments invalid
The LOGIN command identifies the user to the server and carries
the plaintext password authenticating this user.
Example: C: a001 LOGIN SMITH SESAME
S: a001 OK LOGIN completed
Myers [Page 15]
Internet DRAFT ACAP November 25, 1996
3.4. Searching
This section describes the SEARCH command, for retrieving data from
datasets.
3.4.1. SEARCH Command
Arguments: dataset or context name
optional list of modifiers
search criteria
Data: intermediate responses: ENTRY, MODTIME
Result: OK - search completed
NO - search failure: can't perform search
BAD - command unknown or arguments invalid
The SEARCH command identifies a subset of entries in a dataset and
returns information on that subset to the client.
The first argument to SEARCH identifies what is to be searched.
If the string begins with a slash ("/"), it is the name of a
dataset to be searched, otherwise it is a name of a context that
was created by a SEARCH command given previously in the session.
Following that are zero or more modifiers to the search. Each
modifier may be specified at most once. The defined modifiers
are:
LIMIT number Limits the number of intermediate ENTRY responses
that the search may generate. The numeric argument
specifies the limit. If the search matches more
entries than the limit, then no ENTRY intermediate
responses are returned. The SEARCH command still
succeeds, returning the number of matches in a
TOOMANY special information token in the tagged OK
response.
MAKECONTEXT name
The SEARCH command creates a context with the name
given in the argument to refer to the matching
entries.
If the SEARCH is successful, the context name may
then be given as an argument to subsequent SEARCH
commands to search the set of matching entries.
Myers [Page 16]
Internet DRAFT ACAP November 25, 1996
If a context with the specified name already
exists, it is first freed. If a new context may
not be created due to the server's limit on the
number of existing contexts, the command fails,
returning a TOOMANYCONTEXTS special information
token in the tagged NO response.
Contexts are discussed in more detail in section
XXX.
RETURN (metadata...)
Specifies what is to be returned in intermediate
ENTRY responses. If this modifier is not
specified, no intermediate ENTRY responses are
returned.
Inside the parentesis is a list of attributes, each
optionally followed by a parenthesized list of
metadata. If the parenthesised list of metadata is
not specified, it defaults to "(value)".
[OPEN ISSUE: wildcards?]
Following the last intermediate ENTRY response, the
server returns a single intermediate MODTIME
response.
SORT (attribute ordering...)
Specifies the order in which any resulting ENTRY
replies are to be returned to the client. The SORT
modifier takes as an argument a parenthesized list
of one or more attribute/ordering pairs. Attribute
lists the attribute to sort on, ordering specifies
the name of the collation rule to apply to the
values of the attribute. [TODO: list predefined
orderings, establish registry]. Successive
attribute/ordering pairs are used to apply ordering
of two entries only when all preceeding pairs
indicate two entries collate the same.
If the SORT modifier is used in conjunction with
the MAKECONTEXT modifier, the SORT modifier
specifies the ordering of entries in the created
context.
If no SORT modifier is specified, or none of the
attribute/ordering pairs indicates an order to two
entries, the server uses the order of the entries
Myers [Page 17]
Internet DRAFT ACAP November 25, 1996
that exists in the context or dataset being
searched.
Following the modifiers is the search criteria. Searching
criteria consist of one or more search keys. When multiple keys
are specified, the result is the intersection (AND function) of
all the messages that match those keys. For example, the criteria
COMPARE modtime +octet "19951206103400" COMPARE modtime -octet
"19960112000000" refers to all entries modified between 10:34
December 6 1995 and midnight January 12, 1996. A search key may
also be a parenthesized list of one or more search keys (e.g. for
use with the OR and NOT keys).
The currently defined search keys are as follows.
COMPARE attribute ordering value
Entries for which the specified attribute collates using
the specified ordering the same or later than the
specified value.
COMPARESTRICT attribute ordering value
Entries for which the specified attribute collates using
the specified ordering later than the specified value.
EQUAL attribute ordering value
Entries for which the specified attribute collates using
the specified ordering the same as the specified value.
NOT search-key
Entries that do not match the specified search key.
OR search-key1 search-key2
Entries that match either search key.
RANGE start end Entries which are within the specified range of the
dataset or context's ordering. The lowest-ordered entry
in the dataset or context is assigned number one, the
next lowest entry is assigned number two, and so on. The
numeric arguments specify the lowest and highest numbers
to match.
Example: C: [TODO - write examples]
3.4.2. ENTRY Response
Data: entry name
entry data
Myers [Page 18]
Internet DRAFT ACAP November 25, 1996
The ENTRY intermediate response occurs as a result of a SEARCH or
LOCK command. This is the means by which dataset entries are
returned to the client. The entry with the given name matches the
search. Following the entry name is a set of zero or more
strings, each containing the respective metadata, contained in the
entry, that was specified in the RETURN search modifier.
3.4.3. MODTIME Response
Data: modtime value
The MODTIME intermediate response occurs as a result of a SEARCH
command. It indicates that the previously returned ENTRY
responses include all updates to the returned entries up to and
including the modtime value in the argument.
3.5. Contexts
A context is an ordered subset of entries in a dataset, created by a
SEARCH command with a MAKECONTEXT modifier. Context names are
client-generated strings and must not start with the slash ('/')
character.
Contexts only have scope within the ACAP session they were created.
There is a server-imposed limit on the number of contexts that may
exist at one time within a session. The minimum value for this limit
is 100, if the server supports a larger limit it must advertise it in
a CONTEXTLIMIT capability.
3.5.1. FREECONTEXT Command
Arguments: context name
Data: no specific data for this command
Result: OK - freecontext completed
NO - freecontext failure: no such context
BAD - command unknown or arguments invalid
The FREECONTEXT command causes the server to free all state
associated with the named context. The context may no longer be
searched and the server will no longer issue any untagged
responses for the context. The context is no longer counted
against the server's limit on the number of contexts.
Example: C: A683 FREECONTEXT blurdybloop
S: A683 OK Freecontext completed
Myers [Page 19]
Internet DRAFT ACAP November 25, 1996
3.5.2. NOTIFYCONTEXT Command
Arguments: context name
list of attributes
Data: untagged responses: ADDTO REMOVEFROM CHANGE MODTIME
Result: OK - Notifycontext completed: notifications enabled for
context
NO - Notifycontext failed: no such context
BAD - command unknown or arguments invalid
The NOTIFYCONTEXT command requests the server send untagged ADDTO,
REMOVEFROM, CHANGE, and MODTIME responses for the specified
context, notifying the client of how the results of the SEARCH
command that created the context would change due to modifications
that have been made to the dataset. Following the context name is
the list of attributes to be returned in ADDTO and CHANGE
responses for the context.
[OPEN ISSUE: NOTIFYCONTEXT on contexts created from contexts, when
the parent context has been given to the FREECONTEXT or
NOTIFYCONTEXT command.]
The server may issue untagged ADDTO, REMOVEFROM, or CHANGE
notifications for a context at any time between the issuing of the
NOTIFYCONTEXT command for the context and the completion of a
FREECONTEXT command for the context. After issuing a sequence of
ADDTO, REMOVEFROM or CHANGE notifications, the server should issue
an untagged MODTIME notification indicating that the client has
all updates to the entries in the context up to and including the
given modtime value.
The client may issue a subsequent NOTIFYCONTEXT command for the
same context, this has the effect of changing the list of
attributes included in ADDTO and CHANGE responses for the context.
Example: C: Z4S9 NOTIFYCONTEXT blurdybloop
S: Z4S9 OK notifications enabled for context
Myers [Page 20]
Internet DRAFT ACAP November 25, 1996
3.5.2. UPDATECONTEXT Command
Arguments: list of context names
Data: untagged responses: ADDTO REMOVEFROM CHANGE MODTIME
Result: OK - Updatecontext completed: all updates completed
NO - Updatecontext failed: no such context
BAD - command unknown or arguments invalid
The UPDATECONTEXT command causes the server to ensure that the
client is notified of all changes to the contexts listed as
arguments up to the current time. The contexts listed in the
arguments must have been previously given to a successful
NOTIFYCONTEXT command.
While a server may issue untagged ADDTO, REMOVEFROM, CHANGE, and
MODTIME at any time, the UPDATECONTEXT command is used to "prod"
the server to send any notifications it has not sent yet.
Example: C: Z4S9 UPDATECONTEXT blurdybloop
S: Z4S9 OK client has been notified of all changes
3.5.4. ADDTO Response
Data: context name
entry name
position
attribute/value list
The untagged ADDTO response informs the client that an entry has
been added to a context. The response includes the position
number of the added entry (the first entry in the context is
numbered 1) and those attribute/value pairs contained in the entry
which match attributes specified in the last NOTIFYCONTEXT command
for the context.
Example: S: * ADDTO blurdybloop fred 15
3.5.5. REMOVEFROM Response
Data: context name
entry name
old position
The untagged REMOVEFROM response informs the client that an entry
Myers [Page 21]
Internet DRAFT ACAP November 25, 1996
has been removed from a context. The response includes the
position number that the removed entry used to have (the first
entry in the context is numbered 1).
Example: S: * REMOVEFROM blurdybloop fred 15
3.5.6. CHANGE Response
Data: context name
entry name
old position
new position
attribute/value list
The untagged CHANGE response informs the client that an entry in a
context has either changed position in the context or has changed
the values of one or more of the attributes specified in the last
NOTIFYCONTEXT command for the context.
The response includes the previous and current position numbers of
the entry (the first entry in the context is numbered 1) and those
attribute/value pairs contained in the entry which match
attributes specified in the last NOTIFYCONTEXT command for the
context.
Example: S: * CHANGE blurdybloop fred 15 10
3.5.7. MODTIME Response
Data: context name
modtime value
The untagged MODTIME response informs the client that it has
recieved all updates to entries in the context which have modtime
values less than or equal to the modtime value in the argument.
Example: S: * CHANGE blurdybloop fred 15 10
3.6. Dataset modification
The following commands and responses handle modification of datasets.
Myers [Page 22]
Internet DRAFT ACAP November 25, 1996
3.6.1. STORE Command
Arguments: dataset name
entry name
metadata list
Data: no specific data for this command
Result: OK - store completed
NO - store failure: can't store that name
invalid UTF-8 syntax
BAD - command unknown or arguments invalid
Creates or modifies the named entry in the named dataset. The
values of metadata not specified in the command are not changed.
Setting the "value" metadata of an attribute to the empty string
removes the attribute from the entry.
The reserved attribute "name" may be included in the metadata
list. Changing the value of this attribute indicates a request to
rename the entry.
The reserved attribute "modtime" may not be included in the
metadata list, but will automatically be updated. The reserved
attribute "createtime" may not be included in the metadata list,
but will automatically be set when an entry is created.
Example: C: A342 STORE Fred "Barney Rubble" addressbook.phone
"555" addressbook.email ""
S: A342 OK Store completed
3.6.2. DELETE Command
Arguments: dataset name
entry name
Data: no specific data for this command
Result: OK - delete completed
NO - delete failure: can't delete that entry
BAD - command unknown or arguments invalid
Removes the named entry from the named dataset. If there is no
such entry in the dataset, the command simply returns a tagged OK
response.
Myers [Page 23]
Internet DRAFT ACAP November 25, 1996
3.6.3. DELETEDSINCE Command
Arguments: dataset name
time
Data: untagged response: DELETEDFROM
Result: OK - Deletedfrom completed
NO - Deletedfrom failure: can't read dataset
date too far in the past
BAD - command unknown or arguments invalid
The DELETEDFROM command returns in untagged [OPEN ISSUE:
intermediate?] DELETEDFROM replies the names of entries that have
been deleted from the named dataset since the given time.
Servers may impose a limit on the number or age of deleted entry
names they keep track of. If the server does not have information
going back to the specified time, the command fails, returning a
TOOOLD special information token in the tagged NO response.
Example: C: Z4S9 DELETEDSINCE /mailboxes 19951205103412
S: * DELETEDFROM /mailboxes shared.blurdybloop
S: * DELETEDFROM /mailboxes shared.anteaters
S: Z4S9 OK DELETEDSINCE completed
C: Z4U3 DELETEDSINCE /mailboxes 19951009040854
S: Z4U3 NO [TOOOLD] Don't have that information
3.6.4. DELETEDFROM Response
Data: dataset name
entry name
The untagged DELETEDFROM response occurs as a result of a
DELETEDSINCE command. It returns the names of a dataset and an
entry that has been deleted from the dataset.
Example: S: * DELETEDFROM /mailboxes shared.blurdybloop
3.7. Dataset management
[TODO: specify/describe attributes which control sub-datasets.]
Myers [Page 24]
Internet DRAFT ACAP November 25, 1996
3.8. Access Control Lists
An access control list is a set of <identifier,rights> pairs.
Identifier is a US-ASCII string. The identifier anyone is reserved
to refer to the universal identity (all authentications, including
anonymous). All user name strings accepted by the LOGIN or
AUTHENTICATE commands to authenticate to the ACAP server are reserved
as identifiers for the corresponding user. Identifiers starting with
a dash ("-") are reserved for "negative rights", described below.
All other identifier strings have implementation-defined semantics.
Rights is a string listing a (possibly empty) set of alphanumeric
characters, each character listing a set of operations which is being
controlled. Letters are reserved for ``standard'' rights, listed
below. The set of standard rights may only be extended by a
standards-track document. Digits are reserved for implementation or
site defined rights. The currently defined standard rights are:
r - read
w - write
o - override (see
a - administer (perform SETACL)
An implementation may force rights to always or never be granted.
[Mention that rights may not be tied, as they can be in IMAP?]
It is possible for multiple identifiers in an access control list to
apply to a given user (or other authentication identity). For
example, an ACL may include rights to be granted to the identifier
matching the user, one or more implementation-defined identifiers
matching groups which include the user, and/or the identifier
"anyone". How these rights are combined to determine the user's
access is implementation-defined. An implementation may choose, for
example, to use the union of the rights granted to the applicable
identifiers. An implementation may instead choose, for example, to
only use those rights granted to the most specific identifier present
in the ACL. A client may determine the set of rights granted to the
logged-in user for a given mailbox by using the MYRIGHTS command.
When an identifier in an ACL starts with a dash ("-"), that indicates
that associated rights are to be removed from the identifier that is
prefixed by the dash. For example, if the identifier "-fred" is
granted the "w" right, that indicates that the "w" right is to be
removed from users matching the identifier "fred". Implementations
need not support having identifiers which start with a dash in ACLs.
Each attribute of each entry of a dataset may potentially have an
Myers [Page 25]
Internet DRAFT ACAP November 25, 1996
ACL. If an attribute in an entry does not have an ACL, then access
is controlled by a default ACL for that attribute in the dataset, if
it exists. If there is no default ACL for that attribute in the
dataset, access is controlled by a default ACL for that dataset. The
default ACL for a dataset must exist.
In order to perform any manipulation on an entry on a dataset, the
client must have 'r' rights on the "name" attribute of the entry.
[OPEN ISSUE: l, i, c, and/or d rights which only apply at the dataset
level? Lookup could be implemented by the 'r' right on the 'name'
attribute of that dataset's entry in the dataset list. Insertion
could be handled by the 'w' right on the "name" attribute in the
dataset. Creation and deletion of datasets are instead handled by
the 'w' right on the "dataset.exists" and related attributes in the
parent dataset.]
Many of the ACL commands and responses include an ``acl object''
parameter, for specifying what the ACL applies to. This is a
parenthesized list. The list contains just the dataset name when
referring to the default ACL for a dataset. The list contains a
dataset name and an attribute name when referring to the default ACL
for an attribute in a dataset. The list contains a dataset name, an
attribute name, and an entry name when referring to the ACL for an
attribute of an entry of a dataset.
3.8.1. SETACL Command
Arguments: acl object
authentication identifier
access rights
Data: no specific data for this command
Result: OK - setacl completed
NO - setacl failure: can't set acl
BAD - command unknown or arguments invalid
The SETACL command changes the access control list on the
specified object so that the specified identifier is granted the
permissions enumerated in rights. If the object did not
previously have an access control list, it does now.
Myers [Page 26]
Internet DRAFT ACAP November 25, 1996
3.8.2. DELETEACL Command
Arguments: acl object
optional authentication identifier
Data: no specific data for this command
Result: OK - deleteacl completed
NO - deleteacl failure: can't delete acl
BAD - command unknown or arguments invalid
If given the optional identifier argument, the DELETEACL command
removes any portion of the access control list on the specified
object for the specified identifier.
If not given the optional identifier argument, the DELETEACL
command removes the ACL from the object entirely, causing access
to be controlled by a higher-level default ACL. It is an error to
use this form of the DELETEACL command on the default ACL for a
dataset.
3.8.3. GETACL Command
Arguments: acl object
Data: untagged responses: ACL
Result: OK - getacl completed
NO - getacl failure: can't get acl
acl does not exist
BAD - command unknown or arguments invalid
The GETACL command returns the access control list for the
specified object in an untagged ACL reply. If the specified
object does not have an ACL, the command fails, returning a NOACL
special information token in the tagged NO response.
Example: C: A002 GETACL ("/mailboxes")
S: * ACL ("/mailboxes") anyone r
S: A002 OK Getacl complete
Myers [Page 27]
Internet DRAFT ACAP November 25, 1996
3.8.4. LISTRIGHTS Command
Arguments: acl object
authentication identifier
Data: untagged responses: LISTRIGHTS
Result: OK - listrights completed
NO - listrights failure: can't get rights list
BAD - command unknown or arguments invalid
The LISTRIGHTS command takes an object and an identifier and
returns information about what rights may be granted to the
identifier in the ACL for the object.
Example: C: a001 LISTRIGHTS ("/mailboxes") smith
S: * LISTRIGHTS ("/mailboxes") smith r w
S: a001 OK Listrights completed
C: a005 LISTRIGHTS ("/mailboxes" archive.imap) anyone
S: * LISTRIGHTS ("/mailboxes" archive.imap) anyone "" r w
S: a005 OK Listrights completed
3.8.5. MYRIGHTS Command
Arguments: acl object
Data: untagged responses: MYRIGHTS
Result: OK - myrights completed
NO - myrights failure: can't get rights
BAD - command unknown or arguments invalid
The MYRIGHTS command returns the set of rights that the client has
to the given object in an untagged MYRIGHTS reply.
Example: C: A003 MYRIGHTS ("/mailboxes")
S: * MYRIGHTS ("/mailboxes") r
S: A003 OK Myrights complete
Myers [Page 28]
Internet DRAFT ACAP November 25, 1996
3.8.6. ACL Response
Data: acl object
zero or more identifier rights pairs
The ACL response occurs as a result of a GETACL command. The
first list is the object for which this ACL applies. This is
followed by zero or more pairs of strings, each pair contains the
identifier for which the entry applies followed by the set of
rights that the identifier has.
3.8.7. LISTRIGHTS Response
Data: acl object
identifier
required rights
list of optional rights
The LISTRIGHTS response occurs as a result of a LISTRIGHTS
command. The first two arguments are the object and identifier
for which this rights list applies. Following the identifier is a
string containing the (possibly empty) set of rights the
identifier will always be granted in the mailbox.
Following this are zero or more strings each containing a single
right the identifier may be granted in the mailbox.
The same right may not be listed more than once in the LISTRIGHTS
command.
3.8.8. MYRIGHTS Response
Data: acl object
rights
The MYRIGHTS response occurs as a result of a MYRIGHTS command.
The first string is the object for which these rights apply. The
second string is the set of rights that the client has.
3.9. Advisory locking
These commands allow cooperating clients to synchronize their updates
to datasets.
Myers [Page 29]
Internet DRAFT ACAP November 25, 1996
3.9.1. LOCK Command
Arguments: dataset name
optional list of entry names
optional list of attribute names
Data: intermediate responses: ENTRY
Result: OK - lock completed
NO - lock failure: can't lock dataset/entry
some other client has obtained lock on dataset/entry
BAD - command unknown or arguments invalid
The LOCK command accepts as arguments a dataset name and an
optional list of entry names. It attempts to acquire an exclusive
semaphore on each of the entries in the dataset. The dataset must
exist, but the named entries need not. If the optional list of
entry names is not present, it attempts to acquire an exclusive
semaphore on the dataset as a whole.
If the command is successful, the server must ensure that no other
client will be able to successfully lock either any of the named
entries in the dataset or the dataset as a whole until the
successful client either performs a matching UNLOCK command or
closes the connection. If the optional list of entry names is not
present, the server must also ensure that no other client will be
able to lock any entry in the in the dataset.
If some other client has obtained either the semaphore on the
dataset as a whole or a semaphore on one of the named entries, the
command fails, returning a LOCKED special information token in the
tagged NO response.
If the command is successful and the optional list of attributes
is present, the server returns the values of those attributes of
those entries in intermediate ENTRY responses.
The server should ensure that the client has permission to perform
a STORE operation on at least one attribute of each of the
entries. [OPEN ISSUE: what is necessary in order to LOCK the
entire dataset--at least one entry or all entries?]
Even though other clients may not perform a LOCK operation on an
entry, servers should not prevent them from performing STORE
Myers [Page 30]
Internet DRAFT ACAP November 25, 1996
operations on the entry.
Example: C: A069 LOCK "/addressbook/fred" (barney)
(addressbook.email)
S: A069 ENTRY barney addressbook.email "barney@bedrock"
S: A069 OK Lock completed
C: A070 LOCK "/addressbook/shared" ("Bam Bam")
S: A070 NO [LOCKED] Locked by Barney on client7.do.main
3.9.2. UNLOCK Command
Arguments: dataset name
optional list of entry names
Data: no specific data for this command
Result: OK - unlock completed
NO - unlock failure: can't unlock that dataset/entry
BAD - command unknown or arguments invalid
The UNLOCK command accepts as arguments a dataset name and an
optional list of entry names. If the list of entry names is
present, it releases any semaphores the client may have previously
obtained on those entries by using the LOCK command. If the list
of entry names is not present, it removes any semaphore the client
may have on the dataset as a whole or on any entry in the dataset.
Myers [Page 31]
Internet DRAFT ACAP November 25, 1996
3.x. Server Responses - Status Responses
[TODO - put this somewhere reasonable]
Status responses may include an optional response code. A response
code consists of data inside square brackets in the form of an atom,
possibly followed by a space and arguments. The response code
contains additional information or status codes for client software
beyond the OK/NO/BAD condition, and are defined when there is a
specific action that a client can take based upon the additional
information.
The currently defined response codes are:
ALERT The human-readable text contains a special alert
that MUST be presented to the user in a fashion
that calls the user's attention to the message.
LOCKED The option or address book entry is already locked
by another client.
REFER This response code may be returned in a tagged NO
response to any command that takes a dataset name
as a parameter. It is a referral, indicating that
the command should be retried using the dataset
named in the URL given in the argument.
TOOMANY This response code may be returned in a tagged OK
response to a SEARCH command which includes the
LIMIT modifier. The argument returns the number of
matching entries.
TOOMANYCONTEXTSThis response code may be returned in a tagged NO
respose to a SEARCH command which includes the
MAKECONTEXT modifier. It indicates that a new
context may not be created due to the server's
limit on the number of existing contexts.
NOACL This response code may be returned in a tagged NO
response to a GETACL command. It indicates that
the specified object does not have an access
control list associated with it.
Additional response codes defined by particular client or server
implementations should be prefixed with an "X" until they are
added to a revision of this protocol. Client implementations
should ignore response codes that they do not recognize.
Myers [Page 32]
Internet DRAFT ACAP November 25, 1996
3.x Server Responses - Command Continuation Request
[TODO - put this somewhere reasonable]
The command completion request response is indicated by a "+" token
instead of a tag. This indicates that the server is ready to accept
the continuation of a command from the client. The remainder of this
response is a line of text.
This response is used in the AUTHENTICATE command to transmit server
data to the client, and request additional client data. This
response is also used if an argument to any command is a
synchronizing literal.
The client is not permitted to send the octets of a synchronizing
literal unless the server indicates that it expects it. This permits
the server to process commands and reject errors on a line-by-line
basis, assuming it checks for non-synchronizing literals at the end
of each line. The remainder of the command, including the CRLF that
terminates a command, follows the octets of the literal. If there
are any additional command arguments the literal octets are followed
by a space and those arguments.
Example: C: A001 LOGIN {11}
S: + Ready for additional command text
C: FRED FOOBAR {7}
S: + Ready for additional command text
C: fat man
S: A001 OK LOGIN completed
C: A044 BLURDYBLOOP {102856}
S: A044 BAD No such command as "BLURDYBLOOP"
Myers [Page 33]
Internet DRAFT ACAP November 25, 1996
4. Predefined Dataset Types
Dataset lists
[described in section "Child Dataset Attributes"]
Mailbox lists
[OPEN ISSUE: Use ACAP dataset hierarchy? How to deal with
different separator characters.]
name "INBOX.sent-mail"
mailbox.serverlist "imap2.andrew.cmu.edu imap7.andrew.cmu.edu"
mailbox.subscription "show" ; possible values:
; read - present new messages by default
; show - display in mailbox list
; todo - present all messages by default
; OPEN ISSUE: some other scheme?
mailbox.disconnected-mode "cm" ; Disconnected caching mode
; set of flags.
mailbox.creation-time "19951206103412"
mailbox.uidvalidity "807558230"
mailbox.marked "y" ; non-empty if Marked
mailbox.noselect "" ; non-empty if elect
mailbox.noinferiors "" ; non-empty if nferiors
mailbox.acl "" ; Access control list
; OPEN ISSUE: how to modify. Use IMAP4?
mailbox.separator "." ; Hierarchy separator char.
Options
name "common.from" ; Need hierarchical registry of names?
; OPEN ISSUE: use dataset hierarchy.
option.value "John Gardiner Myers <jgm+@cmu.edu>"
Addressbooks
name
addressbook.fullname
addressbook.alias ; should probably not be defined ???
addressbook.email
; may suffix .work, .home, .mobile
addressbook.phone ; Voice phone #
; may suffix .work, .home, .car, .mobile
addressbook.fax ; Fax phone #
; may suffix .work, .home, .car, .mobile
Myers [Page 34]
Internet DRAFT ACAP November 25, 1996
addressbook.pager ; Pager phone #
; may suffix .work, .home ???
addressbook.address ; Physical address
; may suffix .work, .home
; All this suffix stuff seems overboard.
addressbook.members
addressbook.expand ; Magic, expansion of email/members
Media types
name ; Name of media type
mediatype.mime ; MIME media type
mediatype.mac-code ; Macintosh type/creator code
mediatype.extension ; List of common filename extensions
mediatype.magic-number ; Magic number
Bookmarks
name
bookmark.url
Groups
name
group.members
5. Dataset Shadowing
It is possible for a dataset to ``shadow'' another. Data in the
shadowed dataset appears in the shadowing dataset, except where
explicitly overridden by data in the shadowing dataset.
The shadowed dataset specifies which values may be overridden in
shadowing datasets. If a shadowed dataset has a non-empty value for
any given attribute in an entry, the ACL for that attribute in that
entry must grant a user the 'o' right in order for the user to store
a corresponding value in a shadowing dataset.
The shadowed dataset is usually a system-wide set of defaults. The
system-wide dataset usually has one shadowing dataset per user,
allowing each user to add to or modify the defaults as appropriate.
[TODO: describe "dataset.shadows" attribute in parent dataset.]
6. Namespace conventions
[TODO]
Myers [Page 35]
Internet DRAFT ACAP November 25, 1996
6.1. Dataset Namespace
6.2 Attribute Namespace
[TODO: Have vnd. and prs. spaces. All else for published stuff
intended for interoperation.]
6.3 Option Namespace
[TODO: Have vnd. and prs. spaces. All else for published stuff
intended for interoperation. Should use dataset hierarchy, so vendor
stuff can be in vendor's own sub-tree of datasets.]
6.4 ACL Identifer Namespace
9. Formal Syntax
The following syntax specification uses the augmented Backus-Naur
Form (BNF) notation as specified in [RFC-822] with one exception; the
delimiter used with the "#" construct is a single space (SPACE) and
not one or more commas.
Except as noted otherwise, all alphabetic characters are case-
insensitive. The use of upper or lower case characters to define
token strings is for editorial clarity only. Implementations MUST
accept these strings in a case-insensitive fashion.
alpha ::= "A" / "B" / "C" / "D" / "E" / "F" / "G" / "H" / "I" /
"J" / "K" / "L" / "M" / "N" / "O" / "P" / "Q" / "R" /
"S" / "T" / "U" / "V" / "W" / "X" / "Y" / "Z" /
"a" / "b" / "c" / "d" / "e" / "f" / "g" / "h" / "i" /
"j" / "k" / "l" / "m" / "n" / "o" / "p" / "q" / "r" /
"s" / "t" / "u" / "v" / "w" / "x" / "y" / "z" /
;; Case-sensitive
astring ::= atom / string
atom ::= 1*ATOM_CHAR
ATOM_CHAR ::= <any CHAR except atom_specials>
atom_specials ::= "(" / ")" / "{" / "%" / "*" / SPACE / CTL /
quoted_specials
authenticate ::= "AUTHENTICATE" SPACE auth_type *(CRLF base64)
Myers [Page 36]
Internet DRAFT ACAP November 25, 1996
auth_type ::= atom
base64 ::= *(4base64_char) [base64_terminal]
base64_char ::= alpha / digit / "+" / "/"
base64_terminal ::= (2base64_char "==") / (3base64_char "=")
CHAR ::= <any 7-bit US-ASCII character except NUL, 0x01 - 0x7f>
CHAR8 ::= <any 8-bit octet except NUL, 0x01 - 0xff>
command ::= tag SPACE (command_any / command_auth /
command_nonauth) CRLF
;; Modal based on state
continue_req ::= "+" SPACE (resp_text / base64)
CR ::= <ASCII CR, carriage return, 0x0C>
CRLF ::= CR LF
CTL ::= <any ASCII control character and DEL, 0x00-0x1f, 0x7f>
digit ::= "0" / "1" / "2" / "3" / "4" / "5" / "6" / "7" /
"8" / "9"
LF ::= <ASCII LF, line feed, 0x0A>
literal ::= "{" number [ "+" ] "}" CRLF *OCTET
;; The number represents the number of octets
;; May only contain NUL octets in values of attributes
;; whose names end in ".bin"
number ::= 1*DIGIT
quoted ::= <"> *QUOTED_CHAR <">
QUOTED_CHAR ::= <any TEXT_CHAR except quoted_specials> /
"\" quoted_specials
quoted_specials ::= <"> / "\"
response ::= *<response_data> response_done
Myers [Page 37]
Internet DRAFT ACAP November 25, 1996
response_data ::= "*" SPACE (resp_cond_state / resp_cond_bye /
mailbox_data / option_data /
searchaddress_d / fetchaddress_d / address_data /
acl_data / myrights_data) CRLF
response_done ::= response_tagged / response_fatal
response_fatal ::= "*" SPACE resp_cond_bye CRLF
response_tagged ::= tag SPACE resp_cond_state CRLF
resp_cond_bye ::= "BYE" SPACE resp_text
;; Server will disconnect condition
resp_cond_state ::= ("OK" / "NO" / "BAD") SPACE resp_text
;; Status condition
resp_text ::= ["[" resp_text_code "]" SPACE] (text_utf8)
resp_text_code ::= "ALERT" / "LOCKED" /
atom [SPACE 1*<any TEXT_UTF8_CHAR except "]">]
SPACE ::= <ASCII SP, space, 0x20>
specials ::= "(" / ")" / "{" / qspecials
string ::= quoted / literal
tag ::= 1*<any ATOM_CHAR except "+">
text_utf8 ::= 1*TEXT_UTF8_CHAR
TEXT_CHAR ::= <any CHAR except CR and LF>
TEXT_UTF8_CHAR ::= <any UTF8_CHAR except CR and LF>
UTF8_CHAR ::= <TODO: UTF-8 character>
x_command ::= "X" atom <experimental command arguments>
initial_greeting ::= "*" SPACE "OK" *(SPACE capability) CRLF
capability ::= atom [ "(" astring ")" ]
command ::+ "LOGIN" SPACE astring SPACE astring
command ::+ "AUTHENTICATE" SPACE atom [SPACE base64-token]
Myers [Page 38]
Internet DRAFT ACAP November 25, 1996
*(CRLF base64-token)
command ::+ "NOOP"
dataset ::= astring
;; slash-separated dataset name
;; begins with slash
attribute ::= astring
;; dot-separated attribute name
;; ends in ".bin" if value not textual
metadata ::= attribute [ "(" 1#astring ")" ]
value ::= astring
command ::+ "SEARCH" SPACE (dataset / context)
*(SPACE search_modifier)
SPACE search_criteria
search_modifier ::+ "SORT" SPACE "(" 1#(attribute SPACE ordering) ")"
ordering ::= ("+" / "-") atom
; need registry of atom orderings
; predefined: octet, en-case-insensitive
; glob
; numeric-decimal
; ignore-case-diacritical-marks (define?)
search_modifier ::+ "RETURN" SPACE "(" #metadata ")"
; MUST be included
search_modifier ::+ "LIMIT" SPACE number
search_modifier ::+ "MAKECONTEXT" SPACE atom
search_criteria ::= 1#search_key
search_key ::+ "(" search_criteria ")" /
"NOT" SPACE search_key /
"OR" SPACE search_key SPACE search_key
search_key ::+ "EQUAL" SPACE attribute SPACE ordering SPACE astring
search_key ::+ "COMPARE" SPACE attribute SPACE ordering SPACE astring
search_key ::+ "COMPARESTRICT" SPACE attribute SPACE ordering SPACE astring
Myers [Page 39]
Internet DRAFT ACAP November 25, 1996
search_key ::+ "RANGE" SPACE nz_number SPACE nz_number
search_response ::= tag SPACE "ENTRY" SPACE entry_name SPACE *(astring)
/ tag SPACE "MODTIME" SPACE astring
"[REFER" SPACE url "]"
"[TOOMANY" SPACE number "]"
"[TOOMANYCONTEXTS]"
context ::= astring
; Must not start with "/", to distinguish from
; dataset
command ::+ "FREECONTEXT" SPACE context
command ::+ "NOTIFYCONTEXT" SPACE context *(SPACE metadata)
untagged_response ::+ "*" SPACE "ADDTO" SPACE context SPACE entry_name
SPACE number *(SPACE astring)
untagged_response ::+ "*" SPACE "REMOVEFROM SPACE context SPACE entry_name
SPACE number
untagged_response ::+ "*" SPACE "CHANGE" SPACE context SPACE entry_name
SPACE number SPACE number
*(SPACE astring)
untagged_response ::+ "*" SPACE "MODTIME" SPACE astring
command ::+ "STORE" SPACE dataset SPACE entry_name
1*(SPACE metadata SPACE value)
command ::+ "DELETE" SPACE dataset SPACE entry_name
command ::+ "DELETEDSINCE" SPACE dataset SPACE time
; returns DELETEDFROM untagged response, or fails
untagged_response ::+ "*" SPACE "DELETEDFROM" SPACE dataset
SPACE entry_name
command ::+ "SETACL" SPACE acl_object
SPACE identifier SPACE rights
command ::+ "DELETEACL" SPACE acl_object
SPACE identifier
Myers [Page 40]
Internet DRAFT ACAP November 25, 1996
command ::+ "GETACL" SPACE acl_object
untagged_response ::+ "ACL" SPACE acl_object
*(SPACE identifier SPACE rights)
command ::+ "MYRIGHTS" SPACE acl_object
untagged_response ::+ "MYRIGHTS" SPACE acl_object
SPACE rights
acl_object ::= "(" dataset [ SPACE attribute
[ SPACE entry_name ] ] ")"
identifier ::= astring
rights ::= astring ; "r" - read, "w" - write
"[NOACL]"
command ::+ "LOCK" SPACE dataset
[ SPACE "(" 1#entry_name ")"
[ SPACE "(" 1#attribute ")" ] ]
command ::+ "UNLOCK" SPACE dataset
[ SPACE "(" 1#entry_name ") ]
"[LOCKED]"
A protocol session is as follows:
Server: greeting
*<Client: command (first part, if it contains a literal)
*<Server: continue_req
Client: request (next part)
>
Server: response
>
Myers [Page 41]
Internet DRAFT ACAP November 25, 1996
10. Security Considerations
ACAP protocol transactions, including address book and option data,
are sent in the clear over the network unless the optional privacy
protection is negotiated in the AUTH command.
Use of the LOGIN command sends passwords in the clear. This can be
avoided by using the AUTH command instead.
Additional security considerations are discussed in the section
discussing the AUTH and LOGIN commands.
11. Author's Address
John G. Myers
Carnegie-Mellon University
5000 Forbes Ave.
Pittsburgh PA, 15213-3890
Email: jgm+@cmu.edu
Myers [Page 42]
Internet DRAFT ACAP November 25, 1996
Appendices
A. References
[IMAP4] Crispin, Mark R., "Internet Message Access Protocol -
Version 4", RFC 1730.
[SASL] Myers, J., "Simple Authentication and Security Layer (SASL)",
draft-myers-auth-sasl-xx.txt
[MIME-2] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Two: Message Header Extensions for Non-ASCII Text", RFC 1522.
[RFC-822] Crocker, D., "Standard for the Format of ARPA Internet Text
Messages", STD 11, RFC 822.
[UTF8] Yergeau, F. "UTF-8, a transformation format of Unicode and ISO
10646", RFC 2044.
Myers [Page 43]
Internet DRAFT ACAP November 25, 1996
B. ACAP Keyword Index
(command) ................................................. 26
(command) ................................................. 27
(command) ................................................. 27
(command) ................................................. 27
(command) ................................................. 28
(response) ................................................ 28
(response) ................................................ 29
(response) ................................................ 29
ACAP (response) ............................................ 10
ADDTO (response) ........................................... 21
ALERT (response code) ...................................... 32
AUTHENTICATE (command) ..................................... 14
BAD (response) ............................................. 12
BYE (response) ............................................. 13
CHANGE (response) .......................................... 22
DELETE (command) ........................................... 23
DELETEDFROM (response) ..................................... 24
DELETEDSINCE (command) ..................................... 24
ENTRY (response) ........................................... 18
FREECONTEXT (command) ...................................... 19
LOCK (command) ............................................. 30
LOGIN (command) ............................................ 15
LOGOUT (command) ........................................... 11
MODTIME (response) ......................................... 19
MODTIME (response) ......................................... 22
NO (response) .............................................. 12
NOOP (command) ............................................. 11
NOTIFYCONTEXT (command) .................................... 20
OK (response) .............................................. 12
REMOVEFROM (response) ...................................... 21
SEARCH (command) ........................................... 16
STORE (command) ............................................ 22
UNLOCK (command) ........................................... 31
UPDATECONTEXT (command) .................................... 20
Myers [Page 44]
Internet DRAFT ACAP November 25, 1996
TTTTaaaabbbblllleeee ooooffff CCCCoooonnnntttteeeennnnttttssss
Status of this Memo ............................................... i
Abstract .......................................................... i
ACAP Protocol Specification ....................................... 1
1. Conventions Used in this Document ......................... 1
2. Protocol Overview ......................................... 1
2.1. Link Level ................................................ 1
2.2. Commands and Responses .................................... 1
2.2.1. Client Protocol Sender and Server Protocol Receiver ....... 2
2.2.2. Server Protocol Sender and Client Protocol Receiver ....... 2
2.3. State and Flow Diagram .................................... 3
2.3.1. Non-Authenticated State ................................... 3
2.3.2. Authenticated State ....................................... 4
2.3.3. Logout State .............................................. 4
2.4. Data Formats .............................................. 4
2.4.1. Atom ...................................................... 4
2.4.2. Number .................................................... 5
2.4.3. String .................................................... 5
2.4.3.1. 8-bit and Binary Strings .......................... 6
2.5. Operational Considerations ................................ 6
2.5.1. Untagged Status Updates ................................... 6
2.5.2. Response when no Command in Progress ...................... 6
2.5.3. Autologout Timer .......................................... 6
2.5.4. Multiple Commands in Progress ............................. 6
2.6. Datasets .................................................. 7
2.7. Predefined Attributes ..................................... 7
2.8. Attribute metadata ........................................... 8
2.9. Child Dataset Attributes .................................. 8
3. Protocol Specification .................................... 10
3.1. Initial Connection ........................................ 10
3.1.1. ACAP Response ............................................. 10
3.2. Any State ............................................. 11
3.2.1. NOOP Command .............................................. 11
3.2.2. LOGOUT Command ............................................ 11
3.2.3. OK Response ............................................... 12
3.2.4. NO Response ............................................... 12
3.2.5. BAD Response .............................................. 12
3.2.6. BYE Response .............................................. 13
3.3. Non-Authenticated State ............................... 13
3.3.1. AUTHENTICATE Command ...................................... 14
3.3.2. LOGIN Command ............................................. 15
3.4. Searching ................................................. 16
Myers [Page iii]
Internet DRAFT ACAP November 25, 1996
3.4.1. SEARCH Command ............................................ 16
3.4.2. ENTRY Response ............................................ 18
3.4.3. MODTIME Response .......................................... 19
3.5. Contexts .................................................. 19
3.5.1. FREECONTEXT Command ....................................... 19
3.5.2. NOTIFYCONTEXT Command ..................................... 20
3.5.2. UPDATECONTEXT Command ..................................... 20
3.5.4. ADDTO Response ............................................ 21
3.5.5. REMOVEFROM Response ....................................... 21
3.5.6. CHANGE Response ........................................... 22
3.5.7. MODTIME Response .......................................... 22
3.6. Dataset modification ...................................... 22
3.6.1. STORE Command ............................................. 22
3.6.2. DELETE Command ............................................ 23
3.6.3. DELETEDSINCE Command ...................................... 24
3.6.4. DELETEDFROM Response ...................................... 24
3.7. Dataset management ........................................ 24
3.8. Access Control Lists ...................................... 25
3.8.1. SETACL Command .......................................... 26
3.8.2. DELETEACL Command .................................. 27
3.8.3. GETACL Command .......................................... 27
3.8.4. LISTRIGHTS Command .................................. 27
3.8.5. MYRIGHTS Command .......................................... 28
3.8.6. ACL Response ......................................... 28
3.8.7. LISTRIGHTS Response ................................. 29
3.8.8. MYRIGHTS Response ......................................... 29
3.9. Advisory locking .......................................... 29
3.9.1. LOCK Command .............................................. 30
3.9.2. UNLOCK Command ............................................ 31
3.x. Server Responses - Status Responses ....................... 32
3.x Server Responses - Command Continuation Request ........... 33
4. Predefined Dataset Types .................................. 34
5. Dataset Shadowing ......................................... 35
6. Namespace conventions ..................................... 35
6.1. Dataset Namespace ......................................... 36
6.2 Attribute Namespace ....................................... 36
6.3 Option Namespace .......................................... 36
6.4 ACL Identifer Namespace ................................... 36
9. Formal Syntax ............................................. 36
10. Security Considerations ................................... 42
11. Author's Address .......................................... 42
Appendices ........................................................ 43
A. References ................................................ 43
B. ACAP Keyword Index ........................................ 44
Myers [Page iv]
