INTERNET DRAFT S. Barber
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Network News Transport Protocol
draft-ietf-nntpext-base-11.txt
1. Status of this Document
This document is an Internet-Draft and is in full conformance
with Section 10 of RFC 2026. 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 made obsolete 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 accesses at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft shadow directories can be accessed
at http://www.ietf.org/shadow.html.
This section will be updated with the appropriate verbiage
from RFC 2223 should this document has been found ready for
publication as an RFC.
This document is a product of the NNTP Working Group, chaired
by Ned Freed and Stan Barber.
2. Abstract
The Network News Transport Protocol has been in use in the
Internet for a decade and remains one of the most popular
protocols (by volume) in use today. This document is a
replacement for RFC 977 and officially updates the protocol
specification. It clarifies some vagueness in RFC 977,
includes some new base functionality and provides a specific
mechanism to add standardized extensions to NNTP.
3. Introduction
This document specifies the Network News Transport Protocol
(NNTP), which is used for the distribution, inquiry,
retrieval, and posting of net news articles using a reliable
stream-based mechanism. For news reading clients, NNTP enables
retrieval of news articles that are stored in a central
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database, giving subscribers the ability to select only those
articles they wish to read.
The netnews model provides for indexing, cross-referencing,
and expiration of aged messages. For server-to-server
interaction, NNTP is designed for efficient transmission of
net news articles over a reliable full duplex communication
method.
Every attempt is made to insure that the protocol
specification in this document is compatible with the version
specified in RFC 977[1]. However, this version does not
support the ill-defined SLAVE command and permits four digit
years to be specified in the NEWNEWS and NEWGROUPS commands.
It changes the default character set to UTF-8[2] instead of
US-ASCII[3]. It also extends the newsgroup name matching
capabilities already documented in RFC 977.
Generally, new functionality is available using new keywords.
Part of that new functionality involves a mechanism to
discover what new functionality is available to clients from a
server.
This mechanism can also be used to add more functionality as
needs merit such additions.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described
in RFC 2119[4].
An implementation is not compliant if it fails to satisfy one
or more of the MUST requirements for this protocol. An
implementation that satisfies all the MUST and all the SHOULD
requirements for its protocols is said to be "unconditionally
compliant"; one that satisfies all the MUST requirements but
not all the SHOULD requirements for NNTP is said to be
"conditionally compliant".
For the remainder of this memo, the term "client host" refers
to a host making use of the NNTP service, while the term
"server host" refers to a host that offers the NNTP service.
In addition, where examples of interactions between a client
host and a server host are provided a "[C]" will be used to
represent the client host and a "[S]" will be used to
represent the server host.
4. Basic Operation
Every NNTP session MUST involve the following in this order:
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CONNECTION
GREETING
DISCONNECTION
Other steps may occur between the GREETING and DISCONNECTION
step. They are:
CAPABILITIES DISCOVERY
NEWS EXCHANGE
CONCLUSION
NNTP operates over any reliable data stream 8-bit-wide
channel. When running over TCP/IP, the official port for the
NNTP service is 119. Initially, the server host starts the
NNTP service by listening on a TCP port. When a client host
wishes to make use of the service, it MUST establish a TCP
connection with the server host by connecting to that host on
the same port on which the server is listening. This is the
CONNECTION step. When the connection is established, the NNTP
server host MUST send a greeting. This is the GREETING step.
The client host and server host SHOULD then exchange commands
and responses (respectively) until the connection is closed or
aborted. This final step is called the DISCONNECTION step.
If there is a CONCLUSION step, it MUST immediately precede the
DISCONNECTION step. There MUST be only one CONNECTION,
CONCLUSION and DISCONNECTION step for each NNTP session. All
other steps MAY be repeated as needed. For example, the
GREETING step may be repeated if the client makes use of the
MODE READER command (See Section 7.1.2 for more on the MODE
READER command).
The character set for all NNTP commands is UTF-8. Commands in
the NNTP MUST consist of an US-ASCII case-insensitive keyword,
which MAY be followed by one or more arguments. An US-ASCII
CRLF pair MUST terminate all commands. Multiple commands MUST
NOT be on the same line. Keywords MUST consist of printable
US-ASCII characters. Unless otherwise noted elsewhere in this
document, arguments SHOULD consist of printable US-ASCII
characters. Keywords and arguments MUST be each separated by
one or more US-ASCII SPACE or US-ASCII TAB characters.
Keywords MUST be at least three US-ASCII characters and MUST
NOT exceed 12 US-ASCII characters. Command lines MUST NOT
exceed 512 octets, which includes the terminating US-ASCII
CRLF pair. Arguments MUST NOT exceed 497 octets.
Each response MUST start with a three-digit response code that
is sufficient to distinguish all responses. Certain valid
responses are defined to be multi-line; for all others, the
response is contained in a single line. All multi-line
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responses MUST adhere to the following format: After sending
the first line of the response and an US-ASCII CRLF, any
additional lines are sent, each terminated by an US-ASCII CRLF
pair. When all lines of the response have been sent, a final
line MUST be sent, consisting of a termination octet (US-ASCII
decimal code 046, ".") and an US-ASCII CRLF pair. If any line
of the multi-line response begins with the termination octet,
the line MUST be "byte-stuffed" by pre-pending the termination
octet to that line of the response. Hence, a multi-line
response is terminated with the five octets "CRLF.CRLF" (in
US-ASCII). When examining a multi-line response, the client
MUST check to see if the line begins with the termination
octet. If so and if octets other than US-ASCII CRLF follow,
the first octet of the line (the termination octet) MUST be
stripped away. If so and if US-ASCII CRLF immediately follows
the termination character, then the response from the NNTP
server is ended and the line containing ".CRLF" (in US-ASCII)
MUST NOT considered part of the multi-line response. Where a
response is multi-line, the description of the command will
define the format of the response before "byte-stuffing" takes
place.
A NNTP server MAY have an inactivity autologout timer. Such a
timer MUST be of at least three minutes duration. The receipt
of any command from the client during that interval SHOULD
suffice to reset the autologout timer. When the timer
expires, the server should close the TCP connection without
sending any response to the client.
4.1 Response Codes
Each response MUST begin with a three-digit status indicator.
These are status reports from the server and indicate the
response to the last command received from the client.
The first digit of the response broadly indicates the success,
failure, or progress of the previous command.
1xx - Informative message
2xx - Command ok
3xx - Command ok so far, send the rest of it.
4xx - Command was correct, but couldn't be performed for some
reason.
5xx - Command unimplemented, or incorrect, or a serious
program error occurred.
The next digit in the code indicates the function response
category.
x0x - Connection, setup, and miscellaneous messages
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x1x - Newsgroup selection
x2x - Article selection
x3x - Distribution functions
x4x - Posting
x8x - Reserved for authentication and authorization extensions
x9x - Reserved for private use (non-standard extensions)
Certain responses contain parameters such as numbers and names
in addition to the status indicator. In those cases, the
number and type of such parameters is fixed for each response
code to simplify interpretation by the client (any extension
MUST follow this principle as well). In all other cases, the
client MUST only use the status indicator itself to determine
the nature of the response. The exact response codes that can
be returned in response to a given command are detailed in the
description of the keyword that is the first part of the
command.
Parameters MUST be separated from the numeric status indicator
and from each other by a single US-ASCII space. All numeric
parameters MUST be in base 10 (decimal) format, and MAY have
leading zeros. String parameters MUST contain at least one
character and MUST NOT contain US-ASCII spaces, CR, LF, or
tab). The server MAY add any text after the response code or
last parameter as appropriate, and the client MUST NOT make
decisions based on this text. Such text MUST be separated from
the numeric status indicator or the last parameter by at least
one US-ASCII space.
A server MUST respond to an unrecognized, unimplemented, or
invalid command with a negative response code as follows. An
unrecognized command, or an optional command or extension that
is not implemented by the server, MUST be given a 500
response. A syntax error in a recognized command MUST be given
a 501 response. A command that is valid but not permitted
because of the current internal state of the server MUST be
given a 4XX or 5XX response.
Each recognized command MUST return 501 (as above) or one of
the response codes specifically listed in its description or
in an extension. A server MAY provide extensions to this
specification, including new commands, new features of
existing commands, and other ways of changing the internal
state of the server. However, the server MUST NOT produce any
other responses to a client that does not invoke any of the
additional features. (Therefore a client that restricts itself
to this specification will only receive the responses that are
listed).
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If a client receives an unexpected response, it SHOULD use the
first digit of the response to determine the result. For
example, an unexpected 2xx should be taken as success and an
unexpected 4xx or 5xx as failure.
Response codes not specified in this standard MAY be used for
any installation-specific additional commands also not
specified. These SHOULD be chosen to fit the pattern of x9x
specified above.
Neither this document nor any extension registered with IANA
(see section 12) will specify any response codes of the x9x
pattern. (Implementers of extensions are accordingly cautioned
not to use such responses for extensions that may subsequently
be submitted for registration.)
5. The WILDMAT format
The WILDMAT format[5] described here is based on the version
first developed by Rich Salz which was derived from the format
used in the UNIX "find" command to articulate file names. It
was developed to provide a uniform mechanism for matching
patterns in the same manner that the UNIX shell matches
filenames. Patterns are implicitly anchored at the beginning
and end of each string when testing for a match. There are
five pattern-matching operations other than a strict one-to-
one match between the pattern and the source to be checked for
a match. The first is an asterisk (*) to match any sequence of
zero or more UTF-8 characters. The second is a question mark
(?) to match any single UTF-8 character. The third specifies a
specific set of characters. The set is specified as a list of
characters, or as a range of characters where the beginning
and end of the range are separated by a minus (or dash)
character, or as any combination of lists and ranges. The dash
can also be included in the set as a character it if is the
beginning or end of the set. This set is enclosed in square
brackets. The close square bracket (]) may be used in a set if
it is the first character in the set. The fourth operation is
the same as the logical not of the third operation and is
specified the same way as the third with the addition of a
caret character (^) at the beginning of the test string just
inside the open square bracket. The final operation uses the
backslash character to invalidate the special meaning of the
open square bracket ([), the asterisk, backslash, or the
question mark. Two backslashes in sequence will result in the
evaluation of the backslash as a character with no special
meaning.
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Implementers must be careful to apply the pattern-matching
operators to whole characters encoded in UTF-8, and not two
individual octets.
5.1 Negating the wildmat pattern
The exclamation point can be used at the beginning of a wildmat
to negate it. That is, if the remainder of the pattern would
match the string then the negated pattern does not, and vice
versa. If it appears as any other character other than the first
one, it has no special meaning.
5.2 Examples
a) [^]-] -- matches any single character other than a
close square bracket or a minus sign/dash.
b) *bdc -- matches any string that ends with the string
"bdc" including the string "bdc" (without quotes).
c) [0-9a-zA-Z] -- matches any single printable
alphanumeric ASCII character.
d) a??d -- matches any four character string which
begins with a and ends with d.
e) !bc*d -- matches any string that does not start with
"bc" and end with "d" (without quotes)
f) !\\x -- matches any string that does not start with
"\x" (without quotes)
6. Format for Keyword Descriptions
On the following pages are descriptions of each keyword
recognized by the NNTP server and the responses that will be
returned by those commands. These keywords are grouped by the
functional step in which they are used.
Each keyword is shown in upper case for clarity, although the
NNTP server ignores case in the interpretation of commands.
Parameters are shown as follows:
o UPPERCASE indicates literal text to be included in the
command;
o lowercase indicates a token described elsewhere;
o [brackets] indicate that the parameter is optional;
o ellipsis... indicates that the parameter may be repeated
any number of times (it must occur at least once);
o vertical|bar indicates a choice of two mutually exclusive
parameters (exactly one must be provided).
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Parameters are case or language specific only when specified
(either in this document or in RFC 1036[6]).
The name "wildmat" for a parameter indicates that it is a
wildmat format pattern as defined in section 5.
7. The GREETING Step
7.1 Initial Connection
There is no keyword presented by the client upon initial
connection to the server. The server MUST present an
appropriate response code as a greeting to the client. This
response informs the client about what steps the client should
take to reach the news exchange step.
If the server will accept further commands from the client
including POST, the server MUST present a 200 greeting code.
If the server will accept further commands from the client,
but it is not authorized to post articles using the POST
command, the server MUST present a 201 greeting code.
Otherwise the server MUST present a 400 or 502 greeting code
and then immediately close the connection. 502 MUST be used if
the client is not permitted under any circumstances to
interact with the server and 400 otherwise.
7.1.1 Initial Connection Example
Example of a normal connection from an authorized client
[C] Initial TCP connection completed
[S] 200 NNTP Service Ready, posting permitted
Client can send commands at this point. In this example, the
client jumps directly to the conclusion step (See section 10).
[C] QUIT
[S] 205 NNTP Service exits normally
Example of a normal connection from an unauthorized client
[C] Initial TCP connection completed
[S] 502 NNTP Service Unavailable
At this point, the server closes the TCP connection.
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Example of a normal connection from an authorized client that
is not permitted to post
[C] Initial TCP connection completed
[S] 201 NNTP Service Ready, posting prohibited
Client can send commands at this point. In this example, the
client jumps directly to the conclusion step (See section 10).
[C] QUIT
[S] 205 NNTP Service exits normally
Example of a connection from any client where the server is
unable to provide service
[C] Initial TCP connection completed
[S] 400 NNTP Service temporarily unavailable
At this point, the server closes the TCP connection.
7.1.2 MODE READER
MODE READER
MODE READER SHOULD be used by the client to indicate to the
server that it is a newsreading client. This command may be
entered at any time. The server MUST present a response (as
described in section 7.1) appropriate to the server's ability
to provide service to this client in this mode.
7.1.2.1 Responses
200 Posting Permitted
201 Posting Not Permitted
400 Service temporarily unavailable
502 Service unavailable
Following a 400 or 502 response the server MUST immediately
close the connection.
Note that the response need not be the same as the one
presented during the initial greeting.
7.1.2.2 MODE READER Examples
Example of use of the MODE READER command by an authorized
client
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[C] MODE READER
[S] 200 NNTP Service Ready, posting permitted
Client can send commands at this point. In this example, the
client jumps directly to the conclusion step (See section 10).
[C] QUIT
[S] 205 NNTP Service exits normally
Example of use of MODE READER by a client not authorized to
receive service from the server as a news reader
[C] MODE READER
[S] 502 Service Unavailable
At this point, the server closes the TCP connection.
Example of a normal connection from an authorized client that
is not permitted to post
[C] MODE READER
[S] 201 NNTP Service Ready, posting prohibited
Client can send commands at this point. In this example, the
client jumps directly to the conclusion step (See section 10).
[C] QUIT
[S] 205 NNTP Service exits normally
Example of a connection from any client where the server is
unable to provide news reader service
[C] MODE READER
[S] 400 NNTP Service temporarily unavailable
At this point, the server closes the TCP connection.
8. The CAPABILITIES DISCOVERY Step
An NNTP client that wishes to use extensions to NNTP can query
the server to determine which extensions are available. This
is done with the LIST EXTENSIONS command.
If a particular extension is unavailable, the client can
attempt to work around it or it may wish to terminate the
session.
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See section 12 for further discussion of extensions.
8.1 LIST EXTENSIONS
The LIST EXTENSIONS command allows a client to determine which
extensions are supported by the server.
A client NNTP supporting NNTP service extensions SHOULD query
a server early in the session for extensions session by
issuing the LIST EXTENSIONS command. An NNTP Server that
conforms to the specification in this document MUST give a
successful response (see section 8.1.1), a failure response
(see section 8.1.2), or an error response (see section 8.1.3).
This command MAY be issued at anytime during a session. It is
not required that the client issues this command before
attempting to make use of any extension. The response
generated by this command MAY change during a session because
of other state information. However, a client NNTP MUST NOT
cache (for use in another session) any information returned if
the LIST EXTENSIONS command succeeds. That is, a client NNTP
is only able to get the current and correct information
concerning available extensions during a session by issuing a
LIST EXTENSIONS command during that session and processing
that response.
8.1.1 Successful response
A successful response starts with a 202 code and is followed
by a list of extension-labels, one per line. Each line MUST
begin with exactly one space followed by an extension-label
and optionally one or more parameters (separated by single
spaces). The extension-label and the meaning of the parameters
are specified as part of the definition of the extension. The
extension-label MUST be in uppercase.
The server MUST NOT list the same extension twice in the
response, and MUST list all supported extensions. The order in
which the extensions are listed is not significant. The server
need not even consistently return the same order.
The end of the list is defined by the usual period on a line
by itself.
A typical example reply to the LIST EXTENSIONS command might
be a multiline reply of the form:
[C] LIST EXTENSIONS
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[S] 202 Extensions supported:
[S] OVER
[S] PAT
[S] LISTGROUP
[S] .
8.1.2 Failure response
If for some reason the server NNTP is unable to list the
service extensions it supports, it MUST return code 503. No
list (not even an empty one) will be returned.
In the case of a failure response, the client NNTP may try the
extensions either as the need arises or configure itself for
the basic NNTP functionality defined in this document.
8.1.3 Error responses from extended servers
If the server NNTP recognizes the LIST EXTENSIONS command, but
due to various conditions cannot make any extensions available
to the client at the time the client issued the LIST
EXTENSIONS command, it MUST return code 402. No list (not even
an empty one) will be returned.
The client NNTP should configure itself for the basic NNTP
functionality defined in this document, or issue commands that
might change the state of the server, or issue the QUIT
command (see section 10.1) if a particular extension is
required for the client to properly operate.
If the server NNTP determines that the NNTP service is no
longer available (e.g., due to imminent system shutdown), it
must return code 400. Note that this response code should not
be generated due to an inactivity timeout as described in
section 4.
In the case of any error response outlined in this section,
the client NNTP should issue the QUIT command (see section
10.1). This will facilitate an orderly shutdown of the
session.
8.1.4 Responses from improperly implemented servers
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A server NNTP that improperly implements the LIST EXTENSIONS
command may return an empty list. Clients SHOULD accommodate
this protocol violation and interpret it as a response code
402.
The client NNTP should configure itself for the basic NNTP
functionality defined in this document, or issue commands that
might change the state of the server, or issue the QUIT
command (see section 10.1) if a particular extension is
required for the client to properly operate.
9. The NEWS EXCHANGE Step
During this step, two basic types of transactions occur:
o article retrieval from the server
o article posting to the server
9.1 Article Retrieval
News reading clients have available a variety of mechanisms to
retrieve articles via NNTP. The news articles are stored and
indexed using three types of keys. One key is the message id
of an article. According to RFC 1036, this identifier should
be globally unique. Another key is composed of the news group
name and the article number within that news group. That key
MUST be unique to a particular server (there will be only one
article with that number within a particular news group), but
is not required to be globally unique. Additionally, because
the same article can be cross-posted to multiple news groups,
there may be multiple keys that point to the same article on
the same server. The final key is the arrival timestamp,
giving the time that the article arrived at the server.
The server MUST ensure that article numbers are issued in
order of arrival timestamp; that is, articles arriving later
MUST have higher numbers than those that arrive earlier. The
server SHOULD allocate the next sequential unused number to
each new article.
Article numbers MUST lie between 1 and 4,294,967,295
inclusive. The client and server SHOULD NOT use leading zeroes
in specifying article numbers, and MUST NOT use more than 16
digits. In some situations, the value zero replaces an article
number to show some special situation.
9.1.1 Article Retrieval by News Group Name and Article Number
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The following commands are used to set the current news group
name and the "current article pointer" which is used by other
commands for article retrieval. At the start of a NNTP
session, both of these values are undefined.
9.1.1.1 GROUP
GROUP ggg
The required parameter ggg is the name of the news group to be
selected (e.g. "news.software.b"). A list of valid news groups
may be obtained by using the LIST keyword. See section 9.4
for more information on the LIST keyword.
The successful selection response will return the article
numbers of the first and last articles in the group at the
moment of selection (these numbers are referred to as the
"reported low water mark" and the "reported high water mark"),
and an estimate of the number of articles on file in the
group.
If the group is not empty, the estimate MUST be at least the
actual number of articles available, and MUST be no greater
than one more than the difference between the reported low and
high water marks. (Some implementations will actually count
the number of articles on file. Others will just subtract the
low water mark from the high water mark and add one to get an
estimate.)
If the group is empty, one of the following three situations
will occur. Clients MUST accept all three cases; servers MUST
NOT represent an empty group in any other way.
o The high water mark will be one less than the low water
mark, and the estimated article count will be zero.
Servers SHOULD use this method to show an empty group.
This is the only time that the high water mark can be
less than the low water mark.
o All three numbers will be zero.
o The high water mark is greater than or equal to the low
water mark; the estimated article count might be zero or
non-zero; if non-zero, the same requirements apply as for
a non-empty group.
The set of articles in a group may change after the GROUP
command is carried out. That is:
o articles may be removed from the group
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o articles may be reinstated in the group with the same
article number, but those articles MUST have numbers no
less than the reported low water mark (note that this is
a reinstatement of the previous article, not a new
article reusing the number)
o new articles may be added with article numbers greater
than the reported high water mark (if an article that was
the one with the highest number has been removed, the
next new article will not have the number one greater
than the reported high water mark)
Except when the group is empty and all three numbers are zero,
whenever a subsequent GROUP command for the same news group is
issued, either by the same client or a different client, the
reported low water mark in the response MUST be no less than
that in any previous response for that news group sent to any
client. The client may make use of the low water mark to
remove all remembered information about articles with lower
numbers, as these will never recur. This includes the
situation when the high water mark is one less than the low
water mark.
No similar assumption can be made about the high water mark,
as this can decrease if an article is removed, and then
increase again if it is reinstated or if new articles arrive.
When a valid group is selected by means of this command, the
internally maintained "current article pointer" MUST be set to
the first article in the group and the name of the current
news group MUST be set to the selected news group name. If an
invalid group is specified, the previously selected group, if
any, and article MUST remain selected. If an empty news group
is selected, the "current article pointer" is in an
indeterminate state and MUST NOT be used.
The GROUP keyword (or the LISTGROUP keyword, if implemented)
MUST be used by a client and a successful response received
before the any other command is used that depends on having
the "current article pointer" be valid.
9.1.1.1.1 Responses
211 n f l s group selected
(n = estimated number of articles in group, f = first
article number in the group, l = last article number
in the group, s = name of the group.)
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411 no such news group
9.1.1.1.2 GROUP Examples
Example for a group known to the server
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
Example for a group unknown to the server
[C] GROUP example.is.sob.bradner.or.barber
[S] 411 example.is.sob.bradner.or.barber is unknown
9.1.1.2 LAST
LAST
If the current news group is valid, the internally maintained
"current article pointer" MUST be set to the previous article
in the current news group. If already positioned at the first
article of the news group, an error message MUST be returned
and the current article MUST remain selected.
There MAY be no previous article in the group, although the
current article number is not the reported low water mark.
There MUST NOT be a previous article when the current article
number is the reported low water mark.
Because articles can be removed and added, the results of
multiple LAST and NEXT commands MAY not be consistent over the
life of a particular NNTP session.
If successful, a response indicating the current article
number and a message-id string MUST be returned. No article
text is sent in response to this command.
9.1.1.2.1 Responses
223 n a article retrieved - request text separately (n =
article number, a = unique article id)
412 no news group selected
420 no current article has been selected
422 no previous article in this group
9.1.1.2.2 LAST Examples
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Example of a successful article retrieval using LAST
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] NEXT
[S] 223 3000237 <668929@domain.com> retrieved
[C] LAST
[S] 223 3000234 <45223423@to.to> retrieved
Example of an attempt to retrieve an article without having
selected a group (via the GROUP command) first
[S] 200 NNTP Service ready
[C] LAST
[S] 412 no newsgroup selected
Example of an attempt to retrieve an article using the LAST
command when the current article pointer is pointing at the
first article in the group
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] LAST
[S] 422 No previous article to retrieve
Example of an attempt to retrieve an article using the LAST
command when the current group selected is empty
[S] 200 NNTP Service Ready
[C] GROUP example.empty.newsgroup
[S] 211 0 0 0 example.empty.newsgroup
[C] LAST
[S] 420 No current article selected
9.1.1.3 NEXT
NEXT
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If the current news group is valid, the internally maintained
"current article pointer" MUST be advanced to the next article
in the current news group. If no more articles remain in the
current group, an error message MUST be returned and the
current article MUST remain selected.
If successful, a response indicating the current article
number and the message-id string MUST be returned. No article
text is sent in response to this command.
9.1.1.3.1 Responses
223 n a article retrieved - request text separately (n =
article number, a = unique article id)
412 no news group selected
420 no current article has been selected
421 no next article in this group
9.1.1.3.2 NEXT Examples
Example of a successful article retrieval using NEXT
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] NEXT
[S] 223 3000237 <668929@domain.com> retrieved
Example of an attempt to retrieve an article without having
selected a group (via the GROUP command) first
[S] 200 NNTP Service ready
[C] NEXT
[S] 412 no newsgroup selected
Example of an attempt to retrieve an article using the NEXT
command when the current article pointer is pointing at the
last article in the group
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
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[C] ARTICLE 3002322
[S] 220 3002322 <411@whitehouse.gov> retrieved
[S] Path: pathost!demo!whitehouse!not-for-mail
[S] From: nobody@whitehouse.gov(Demo User)
[S] Newsgroups: misc.test
[S] Subject: I am just a test article
[S] Date: 6 Oct 1998 04:38:40 -0500
[S] Organization: The White House, Washington, DC
[S] Message-ID: <411@whitehouse.gov>
[S]
[S] This is just a test article.
[S] .
[C] NEXT
[S] 422 No next article to retrieve
Example of an attempt to retrieve an article using the NEXT
command when the current group selected is empty
[S] 200 NNTP Service Ready
[C] GROUP example.empty.newsgroup
[S] 211 0 0 0 example.empty.newsgroup
[C] NEXT
[S] 420 No current article selected
9.2 Retrieval of Articles and Article Sections
The ARTICLE, BODY, HEAD, and STAT commands are very similar.
They differ only in the parts of the article that are
presented to the client and in the successful response code.
The ARTICLE command is described here in full, while the other
commands are described in terms of the differences.
An article, as defined by RFC 1036, consists of two parts: the
article headers and the article body. When responding to one
of these commands, the server presents the entire article or
appropriate part and does not attempt to alter or translate it
in any way.
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9.2.1 ARTICLE
ARTICLE <message-id>
ARTICLE [number]
The ARTICLE command selects an article based on the arguments
and presents the header, a blank line, and the body of that
article. The command has two forms.
In the first form, a message-id is specified (including the
angle brackets), and the server presents the article with that
message-id in its headers. In this case, the server MUST NOT
alter the "current article pointer". This is both to
facilitate the presentation of articles that may be referenced
within another article being read, and because of the semantic
difficulties of determining the proper sequence and membership
of an article which may have been posted to more than one news
group.
In the second form, an article number may be specified. If so,
and if there is an article with that number in the currently
selected group, the server MUST set the current article
pointer to that number.
Then, whether or not a number was specified, the article
indicated by the current article pointer is presented to the
client.
Note that a previously valid article number MAY become invalid
if the article has been removed. A previously invalid article
number MAY become valid if the article has been reinstated,
but such an article number MUST be no less than the reported
low water mark for that group.
The server MUST NOT change the currently selected group as a
result of this command. The server MUST NOT change the current
selected article except when an article number argument was
provided and the article exists; in particular, it MUST NOT
change it following an unsuccessful response.
9.2.1.1 Responses
First form (message-id specified):
220 0 a article retrieved and follows (multiline, a =
unique article id)
430 no such article
502 service unavailable
Second form (optional article number specified):
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220 n a article retrieved and follows (multiline, n =
article number, a = unique article id)
412 no news group selected
420 no current article selected
423 no such article number in this group
502 service unavailable
The 420 response only occurs if an article number has been
specified.
In the 220 response, the first parameter is 0 for the first
form and the article number (within the current group) for the
second form. The second parameter is the message-id of the
article (within angle brackets). This is taken from the
message-id header line of the article (required by RFC 1036).
If there is no such line, the message-id "<0>" MUST be used
instead (without the double quotes).
Since the message-id field is unique for each article, it may
be used by a client to skip duplicate displays of articles
that have been posted more than once, or to more than one news
group.
The article headers and body are returned as a multiline
response following the initial response line.
9.2.1.2 Examples
Example of a successful retrieval of an article (using no
article number)
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] ARTICLE
[S] 220 3000234 <45223423@to.to>
[S] Path: pathost!demo!somewhere!not-for-mail
[S] From: nobody@nowhere.to (Demo User)
[S] Newsgroups: misc.test
[S] Subject: I am just a test article
[S] Date: 6 Oct 1998 04:38:40 -0500
[S] Organization: Nowhere, To
[S] Message-ID: <45223423@to.to>
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[S]
[S] This is just a test article.
[S] .
Example of a successful retrieval of an article by message-id
[S] 200 NNTP Service Ready
[C] ARTICLE <45223423@to.to>
[S] 220 0 <45223423@to.to>
[S] Path: pathost!demo!somewhere!not-for-mail
[S] From: nobody@nowhere.to (Demo User)
[S] Newsgroups: misc.test
[S] Subject: I am just a test article
[S] Date: 6 Oct 1998 04:38:40 -0500
[S] Organization: Nowhere, To
[S] Message-ID: <45223423@to.to>
[S]
[S] This is just a test article.
[S] .
Example of an unsuccessful retrieval of an article by message-
id
[S] 200 NNTP Service Ready
[C] ARTICLE <i.am.not.there@nowhere.to>
[S] 430 No Such Article Found
Example of an unsuccessful retrieval of an article by number
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 news.groups
[C] ARTICLE 300256
[S] 423 No such article number in this group
Example of an unsuccessful retrieval of an article by number
because no news group was selected first
[S] 200 NNTP Service Ready
[C] ARTICLE 300256
[S] 412 No news group selected
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Example of an attempt to retrieve an article when the current
group selected is empty
[S] 200 NNTP Service Ready
[C] GROUP example.empty.newsgroup
[S] 211 0 0 0 example.empty.newsgroup
[C] ARTICLE
[S] 420 No current article selected
Example of a failure due to the service being unavailable
[S] 200 NNTP Service Ready
[C] ARTICLE <i.am.a.test.article@nowhere.to>
[S] 502 Service unavailable
9.2.2 HEAD
HEAD <message-id>
HEAD [number]
The HEAD command behaves identically to the ARTICLE command
except that, if the article exists, only the headers are
presented (the blank line separating the headers and body MUST
NOT be included).
9.2.2.1 Responses
First form (message-id specified):
221 0 a article retrieved, headers follow (multiline)
430 no such article
502 service unavailable
Second form (optional article number specified):
221 n a article retrieved, headers follow (multiline)
412 no news group selected
420 no current article selected
423 no such article number in this group
502 service unavailable
Except that only the headers are included in the response, the
221 response behaves identically to the 220 response of the
ARTICLE command.
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9.2.2.2 Examples
Example of a successful retrieval of the headers in an article
(using no article number)
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] HEAD
[S] 220 3000234 <45223423@to.to>
[S] Path: pathost!demo!somewhere!not-for-mail
[S] From: nobody@nowhere.to (Demo User)
[S] Newsgroups: misc.test
[S] Subject: I am just a test article
[S] Date: 6 Oct 1998 04:38:40 -0500
[S] Organization: Nowhere, To
[S] Message-ID: <45223423@to.to>
[S] .
Example of a successful retrieval of the headers in an article
by message-id
[S] 200 NNTP Service Ready
[C] HEAD <45223423@to.to>
[S] 220 0 <45223423@to.to>
[S] Path: pathost!demo!somewhere!not-for-mail
[S] From: nobody@nowhere.to (Demo User)
[S] Newsgroups: misc.test
[S] Subject: I am just a test article
[S] Date: 6 Oct 1998 04:38:40 -0500
[S] Organization: Nowhere, To
[S] Message-ID: <45223423@to.to>
[S] .
Example of an unsuccessful retrieval of the header of an
article by message-id
[S] 200 NNTP Service Ready
[C] HEAD <i.am.not.there@nowhere.to>
[S] 430 No Such Article Found
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Example of an unsuccessful retrieval of the header of an
article by number
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] HEAD 300256
[S] 423 No such article number in this group
Example of an unsuccessful retrieval the header of an article
by number because no news group was selected first
[S] 200 NNTP Service Ready
[C] HEAD 300256
[S] 412 No news group selected
Example of an attempt to retrieve the header of an article
when the current group selected is empty
[S] 200 NNTP Service Ready
[C] GROUP example.empty.newsgroup
[S] 211 0 0 0 example.empty.newsgroup
[C] HEAD
[S] 420 No current article selected
Example of a failure due to the service being unavailable
[S] 200 NNTP Service Ready
[C] HEAD <i.am.a.test.article@nowhere.to>
[S] 502 Service unavailable
9.2.3 BODY
BODY <message-id>
BODY [number]
The BODY command behaves identically to the ARTICLE command
except that, if the article exists, only the body is presented
(the blank line separating the headers and body MUST NOT be
included).
9.2.3.1 Responses
First form (message-id specified):
222 0 a article retrieved, body follows (multiline)
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430 no such article
502 service unavailable
Second form (optional article number specified):
222 n a article retrieved, body follows (multiline)
412 no news group selected
420 no current article selected
423 no such article number in this group
502 service unavailable
Except that only the body is included in the response, the 222
response behaves identically to the 220 response of the
ARTICLE command.
9.2.3.2 Examples
Example of a successful retrieval of the body of an article
(using no article number)
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] BODY
[S] 222 3000234 <45223423@to.to>
[S] This is just a test article.
[S] .
Example of a successful retrieval of the body of an article by
message-id
[S] 200 NNTP Service Ready
[C] BODY <45223423@to.to>
[S] 222 0 <45223423@to.to>
[S] This is just a test article.
[S] .
Example of an unsuccessful retrieval of the body of an article
by message-id
[S] 200 NNTP Service Ready
[C] BODY <i.am.not.there@nowhere.to>
[S] 430 No Such Article Found
Example of an unsuccessful retrieval of the body of an article
by number
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[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] BODY 300256
[S] 423 No such article number in this group
Example of an unsuccessful retrieval of the body of an article
by number because no news group was selected first
[S] 200 NNTP Service Ready
[C] BODY 300256
[S] 412 No news group selected
Example of an attempt to retrieve the body of an article when
the current group selected is empty
[S] 200 NNTP Service Ready
[C] GROUP example.empty.newsgroup
[S] 211 0 0 0 example.empty.newsgroup
[C] BODY
[S] 420 No current article selected
Example of a failure due to the service being unavailable
[S] 200 NNTP Service Ready
[C] BODY <i.am.a.test.article@nowhere.to>
[S] 502 Service unavailable
9.2.4 STAT
STAT <message-id>
STAT [number]
The STAT command behaves identically to the ARTICLE command
except that, if the article exists, it is NOT presented to the
client.
This command allows the client to determine whether an article
exists, and in the second form what its message-id is, without
having to process an arbitrary amount of text.
9.2.4.1 Responses
First form (message-id specified):
223 0 a article exists
430 no such article
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502 service unavailable
Second form (optional article number specified):
223 n a article exists
412 no news group selected
420 no current article selected
423 no such article number in this group
502 service unavailable
The parameters of the 223 response are identical to those that
would have been given in a 220 response to the equivalent
ARTICLE command. However, the response is NOT multiline.
9.2.4.2 Examples
Example of STAT on an existing article (using no article
number)
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] STAT
[S] 223 3000234 <45223423@to.to>
Example of a STAT of an existing article by message-id
[S] 200 NNTP Service Ready
[C] STAT <45223423@to.to>
[S] 223 0 <45223423@to.to>
Example of an STAT of an article not on the server by message-
id
[S] 200 NNTP Service Ready
[C] STAT <i.am.not.there@nowhere.to>
[S] 430 No Such Article Found
Example of STAT of an article not in the server by number
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
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[C] STAT 300256
[S] 423 No such article number in this group
Example of STAT of an article by number when no news group was
selected first
[S] 200 NNTP Service Ready
[C] STAT 300256
[S] 412 No news group selected
Example of STAT of an article when the current group selected
is empty
[S] 200 NNTP Service Ready
[C] GROUP example.empty.newsgroup
[S] 211 0 0 0 example.empty.newsgroup
[C] STAT
[S] 420 No current article selected
Example of a failure due to the service being unavailable
[S] 200 NNTP Service Ready
[C] STAT <i.am.a.test.article@nowhere.to>
[S] 502 Service unavailable
9.3 Article Posting
Article posting is done in one of two modes: individual
article posting from news reading clients and article transfer
from other news servers.
9.3.1 POST
POST
If posting is allowed, response code 340 MUST be returned to
indicate that the article to be posted should be sent.
Response code 440 MUST be sent if that posting is prohibited
for some installation-dependent reason.
If posting is permitted, the article MUST be presented to the
server by the client in the format specified by RFC 1036. The
text forming the header and body of the message to be posted
MUST be sent by the client using the conventions for text
received from the news server: A single period (".") on a line
indicates the end of the text, with lines starting with a
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period in the original text having that period doubled during
transmission.
Following the presentation of the termination sequence by the
client, the server MUST return a response code indicating
success or failure of the article transfer. Note that response
codes 340 and 440 are used in direct response to the POST
command. Others are returned following the sending of the
article.
No attempt shall be made by the server to filter characters,
fold or limit lines, or otherwise process incoming text. The
intent is that the server just passes the incoming message to
be posted to the server installation's news posting software,
which is not part of this specification.
9.3.1.1 Responses
240 article received ok
340 send article to be posted. End with <CR-LF>.<CR-LF>
440 posting not allowed
441 posting failed
9.3.1.2 Examples
Example of a successful posting
[S] 200 NNTP Service Ready
[C] POST
[S] 340 Input article. End with <CR-LF>.<CR-LF>
[C] From: demo@testdomain.com(Demo User)
[C] Newsgroups: misc.test
[C] Subject: I am just a test article
[C] Organization: Testdomain, USA
[C]
[C] This is just a test article.
[C] .
[S] 240 Article received ok
Example of an unsuccessful posting
[S] 200 NNTP Service Ready
[C] POST
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[S] 340 Input article. End with <CR-LF>.<CR-LF>
[C] From: demo@testdomain.com(Demo User)
[C] Newsgroups: misc.test
[C] Subject: I am just a test article
[C] Organization: Testdomain, USA
[C]
[C] This is just a test article.
[C] .
[S] 441 Posting failed
Example of an attempt to posting when posting is not allowed
[S] 201 NNTP Service Ready, read-only
[C] POST
[S] 440 Posting not permitted
9.3.2 IHAVE
IHAVE <message-id>
The IHAVE command informs the server that the client has an
article whose id is <message-id>. If the server desires a copy
of that article, it MUST return a response instructing the
client to send the entire article. If the server does not want
the article (if, for example, the server already has a copy of
it), a response indicating that the article is not wanted MUST
be returned.
If transmission of the article is requested, the client MUST
send the entire article, including header and body, in the
manner specified for text transmission from the server. The
server MUST return a response code indicating success or
failure of the transferal of the article.
This function differs from the POST command in that it is
intended for use in transferring already-posted articles
between hosts. It SHOULD NOT be used when the client is a
personal news reading program. In particular, this function
will invoke the server's news posting program with the
appropriate settings (flags, options, etc.) to indicate that
the forthcoming article is being forwarded from another host.
However, the server MAY elect not to post or forward the
article if after further examination of the article it deems
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it inappropriate to do so. Reasons for such subsequent
rejection of an article may include such problems as
inappropriate news groups or distributions, disk space
limitations, article lengths, garbled headers, and the like.
These are typically restrictions enforced by the server host's
news software and not necessarily the NNTP server itself.
9.3.2.1 Responses
235 article transferred ok
335 send article to be transferred. End with <CR-
LF>.<CR-LF>
435 article not wanted - do not send it
436 transfer failed - try again later
437 article rejected - do not try again
Because some host news posting software may not be able to
immediately render status on the whether an article is
inappropriate for posting or forwarding, an NNTP server MAY
acknowledge the successful transfer of the article and later
silently discard it. Thus, an NNTP server MAY return the 235
acknowledgment code and later discard the received article.
9.3.2.2 Examples
Example of successfully sending an article to another site
[S] 200 NNTP Service Ready
[C] IHAVE <i.am.an.article.you.will.want@nowhere.to>
[S] 335 Send it. End with <CR-LF>.<CR-LF>
[C] Path: pathost!demo!somewhere!not-for-mail
[C] From: nobody@nowhere.to (Demo User)
[C] Newsgroups: misc.test
[C] Subject: I am just a test article
[C] Date: 6 Oct 1998 04:38:40 -0500
[C] Organization: Nowhere, To
[C] Message-ID: <i.am.a.test.article@nowhere.to>
[C]
[C] This is just a test article.
[C] .
[S] 235 Article transferred ok
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Example of sending an article to another site that rejects it
[S] 200 NNTP Service Ready
[C] IHAVE <i.am.an.article.you.will.want@nowhere.to>
[S] 335 Send it. End with <CR-LF>.<CR-LF>
[C] Path: pathost!demo!somewhere!not-for-mail
[C] From: nobody@nowhere.to (Demo User)
[C] Newsgroups: misc.test
[C] Subject: I am just a test article
[C] Date: 6 Oct 1998 04:38:40 -0500
[C] Organization: Nowhere, To
[C] Message-ID: <i.am.a.test.article@nowhere.to>
[C]
[C] This is just a test article.
[C] .
[S] 437 Article rejected. Don't send again
Example of sending an article to another site where the
transfer fails
[S] 200 NNTP Service Ready
[C] IHAVE <i.am.an.article.you.will.want@nowhere.to>
[S] 335 Send it. End with <CR-LF>.<CR-LF>
[C] Path: pathost!demo!somewhere!not-for-mail
[C] From: nobody@nowhere.to (Demo User)
[C] Newsgroups: misc.test
[C] Subject: I am just a test article
[C] Date: 6 Oct 1998 04:38:40 -0500
[C] Organization: Nowhere, To
[C] Message-ID: <i.am.a.test.article@nowhere.to>
[C]
[C] This is just a test article.
[C] .
[S] 436 Transfer failed
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Example of sending an article to another site that rejects it
[S] 200 NNTP Service Ready
[C] IHAVE <i.am.an.article.you.will.want@nowhere.to>
[S] 335 Send it. End with <CR-LF>.<CR-LF>
[C] Path: pathost!demo!somewhere!not-for-mail
[C] From: nobody@nowhere.to (Demo User)
[C] Newsgroups: misc.test
[C] Subject: I am just a test article
[C] Date: 6 Oct 1998 04:38:40 -0500
[C] Organization: Nowhere, To
[C] Message-ID: <i.am.a.test.article@nowhere.to>
[C]
[C] This is just a test article.
[C] .
[S] 435 Don't send it again
9.4 The LIST Keyword
9.4.1 LIST
LIST [ACTIVE [wildmat]]
The response to the LIST keyword with no parameters returns a
list of valid news groups and associated information. Each
news group is sent as a line of text in the following format:
group first last status
where <group> is the name of the news group, <last> is the
number of the last known article currently in that news group,
<first> is the number of the first article currently in the
news group, and <status> indicates the current status of the
group on this server. Typically, the <status> will be consist
of the US-ASCII character 'y' where posting is permitted, 'n'
where posting is not permitted and 'm' where postings will be
forwarded to the news group moderator by the news server.
Other status strings may exist. The definition of these other
values and the circumstances under which they are returned is
covered in other specifications.
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The <first> and <last> fields will always be numeric. They
may have leading zeros. The <first> field corresponds to the
"reported low water mark" and the <last> field corresponds to
the "reported high water mark" described in the GROUP command
(see Section 9.1.1.1).
The status of a news group only indicates how posts to that
news group are processed. It does not if the current client is
permitted to post. That is indicated by the status code
returned as part of the greeting.
Please note that an empty list (i.e., the text body returned
by this command consists only of the terminating period) is a
possible valid response, and indicates that there are
currently no valid news groups.
If the optional wildmat parameter is specified, the list is
limited to only the groups that match the pattern.
Specifying a single group is usually very efficient for the
server. Multiple groups may be specified by using wildmat
patterns (described in section 5).
9.4.1.1 Responses
215 list of news groups follows
9.4.1.2 Examples
Example of LIST returning a list of news groups
[S] 200 NNTP Service Ready
[C] LIST
[S] 215 list of news groups follows
[S] misc.test 3000234 3002322 y
[S] alt.fc-writers.recovery 1 4 y
[S] tx.natives.recovery 56 89 y
[S] .
Example of LIST returning no news groups
[S] 200 NNTP Service Ready
[C] LIST
[S] 215 list of news groups follows
[S] .
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9.4.2 LIST ACTIVE.TIMES
LIST ACTIVE.TIMES [wildmat]
The active.times file is maintained by some news transport
systems to contain information about who created a particular
news group and when. The format of this file includes three
fields. The first field is the name of the news group. The
second is the time when this group was created on this news
server measured in seconds since the start of January 1, 1970.
The third is the email address of the entity that created the
news group. When executed, the information is displayed
following the 215 response. When display is completed, the
server will send a period on a line by itself. If the
information is not available, the server will return the 503
error response. If the server does not recognize the command,
it SHOULD return the 501 error response.
If the optional wildmat parameter is specified, the list is
limited to only the groups that match the pattern.
Specifying a single group is usually very efficient for the
server. Multiple groups may be specified by using wildmat
patterns (described in section 5).
9.4.2.1 Responses
215 information follows
501 Syntax error
503 program error, function not performed
9.4.2.2 Examples
Example of LIST ACTIVE.TIMES returning a list of news groups
[S] 200 NNTP Service Ready
[C] LIST ACTIVE.TIMES
[S] 215 information follows
[S] misc.test 930445408 <creatme@isc.org>
[S] alt.rfc-writers.recovery 930562309 <m@nowhere.to>
[S] tx.natives.recovery 930678923 <sob@academ.com>
[S] .
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Example of LIST ACTIVE.TIMES returning an error (The server
software is not configured to maintain this information, but
does recognize the command as valid.)
[S] 200 NNTP Service Ready
[C] LIST ACTIVE.TIMES
[S] 503 program error, function not performed
Example of LIST ACTIVE.TIMES sent to a server that does not
recognize this argument (e.g. The software does not maintain
this information.)
[S] 200 NNTP Service Ready
[C] LIST ACTIVE.TIMES
[S] 501 Syntax Error
9.4.3 LIST DISTRIBUTIONS
LIST DISTRIBUTIONS
The distributions file is maintained by some news transport
systems to contain information about valid values for the
Distribution: line in a news article header and about what the
values mean. Each line contains two fields, the value and a
short explanation on the meaning of the value. When executed,
the information is displayed following the 215 response. When
display is completed, the server will send a period on a line
by itself. If the information is not available, the server
will return the 503 error response. If the server does not
recognize this command, it SHOULD return the 501 error
response.
9.4.3.1 Responses
215 information follows
501 Syntax error
503 program error, function not performed
9.4.3.2 Examples
Example of LIST DISTRIBUTIONS returning a list of news groups
[S] 200 NNTP Service Ready
[C] LIST DISTRIBUTIONS
[S] 215 information follows
[S] usa United States of America
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[S] na North America
[S] world All over the World
[S] .
Example of LIST DISTRIBUTIONS returning an error (e.g. The
server software is not configured to maintain this
information, but does recognize the command as valid.)
[S] 200 NNTP Service Ready
[C] LIST DISTRIBUTIONS
[S] 503 program error, function not performed
Example of LIST DISTRIBUTIONS sent to a server that does not
recognize the command (e.g. The server does not maintain this
information regardless of configuration.)
[S] 200 NNTP Service Ready
[C] LIST DISTRIBUTIONS
[S] 501 Syntax Error
9.4.4 LIST DISTRIB.PATS
LIST DISTRIB.PATS
The distrib.pats file is maintained by some news transport
systems to allow clients to choose a value for the
Distribution: line in the header of a news article being
posted. The information returned consists of lines, in no
particular order, each of which contains three fields
separated by colons. These fields are a weight, a group name
or wildmat pattern, and a Distribution: value, in that order.
The client MAY use this information to select a Distribution:
value based on the name of a newsgroup. To do so, it should
determine the lines whose second field matches the newsgroup
name, select that line with the highest weight (with 0 being
the lowest), and use the Distribution: field from that line.
When executed, the information is displayed following the 215
response. When display is completed, the server will send a
period on a line by itself. If the information is not
available, the server will return the 503 error response. If
this command is not recognized, the server SHOULD return the
501 error response.
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9.4.4.1 Responses
215 information follows
501 Syntax error
503 program error, function not performed
9.4.4.2 Examples
Example of LIST DISTRIB.PATS returning a list of news groups
[S] 200 NNTP Service Ready
[C] LIST DISTRIB.PATS
[S] 215 information follows
[S] 10:local.*:local
[S] .
Example of LIST DISTRIB.PATS returning an error (e.g. The
server software is not configured to maintain this
information, but does recognize the command as valid.)
[S] 200 NNTP Service Ready
[C] LIST DISTRIB.PATS
[S] 503 program error, function not performed
Example of LIST DISTRIB.PATS sent to a server that does not
recognize the command (e.g. The software does not maintain
this information regardless of configuration.)
[S] 200 NNTP Service Ready
[C] LIST DISTRIB.PATS
[S] 501 Syntax Error
9.4.5 LIST NEWSGROUPS
LIST NEWSGROUPS [wildmat]
The newsgroups file is maintained by some news transport
systems to contain the name of each news group that is
active on the server and a short description about the
purpose of each news group. Each line in the file contains
two fields, the news group name and a short explanation of
the purpose of that news group. When executed, the
information is displayed following the 215 response. When
display is completed, the server will send a period on a
line by itself. If the information is not available, the
server will return the 503 response. If the server does not
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recognize the command it should return a 501 response. If
the optional matching parameter is specified, the list is
limited to only the groups that match the pattern (no
matching is done on the group descriptions). Specifying a
single group is usually very efficient for the server, and
multiple groups may be specified by using a wildmat(see
section 5), not regular expressions. If nothing is matched
an empty list is returned, not an error.
9.4.5.1 Responses
215 information follows
501 Syntax error
503 program error, function not performed
9.4.5.2 Examples
Example of LIST NEWSGROUPS returning a list of news groups
[S] 200 NNTP Service Ready
[C] LIST NEWSGROUPS
[S] 215 information follows
[S] misc.test General Usenet testing
[S] alt.rfc-writers.recovery RFC Writers Recovery
[S] tx.natives.recovery Texas Natives Recovery
[S] .
Example of LIST NEWSGROUPS returning an error (e.g. The server
software recognizes the command as valid, but the information
is not available.)
[S] 200 NNTP Service Ready
[C] LIST NEWSGROUPS
[S] 503 program error, function not performed
9.5 Standard extensions
Each of the following sections describes an extension that a
server MAY provide. If the server provides the extension, it
MUST include the appropriate extension label in the response
to LIST EXTENSIONS. If it does not provide it, it MUST NOT
include the appropriate extension label. The descriptions of
facilities in each section are written as if the extension is
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provided. If it is not provided, the entire section should be
ignored.
9.5.1 LISTGROUP extension
This extension provides one command and has the extension
label LISTGROUP.
9.5.1.1 The LISTGROUP Command
LISTGROUP [ggg]
The LISTGROUP command is used to get a listing of all the
article numbers in a particular news group.
The optional parameter ggg is the name of the news group to
be selected (e.g. "news.software.b"). A list of valid news
groups may be obtained from the LIST command. If no group
is specified, the current group is used as the default
argument.
The successful selection response will be a list of the
article numbers in the group followed by a period on a line
by itself. The list starts on the next line following the
211 response code.
When a valid group is selected by means of this command,
the internally maintained "current article pointer" MUST be
set to the first article in the group and the name of the
current news group MUST be set to the selected news group
name. If an invalid group is specified, the previously
selected group and article remain selected. If an empty
news group is selected, the "current article pointer" may
be in an indeterminate state and should not be used.
The LISTGROUP keyword MAY be used by a client as a
replacement for the GROUP command in establishing a valid
"current article pointer." After a successful response is
received, any other command may be used that depends on
having the "current article pointer" be valid.
The group name MUST match a news group obtained from the
LIST command or an error will result, else the server will
respond with the 411 error code.
A server that does not implement this command SHOULD return
a 500 error response.
9.5.1.1.1 Responses
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211 list of article numbers follow
411 No such group
412 Not currently in news group
500 Command not recognized
9.5.1.1.2 Examples
Example of a successful execution with a group that exists on
the server
[S] 200 NNTP Service Ready
[C] LISTGROUP misc.test
[S] 211 list of article numbers follow
[S] 3000234
[S] 3000237
[S] 3000238
[S] 3000239
[S] 3002322
[S] .
Example of an unsuccessful execution with a group that does
not exist on the server
[S] 200 NNTP Service Ready
[C] LISTGROUP this.group.is.not.here
[S] 411 no such group
Example of an attempt to retrieve an article when the current
group selected is empty
[S] 200 NNTP Service Ready
[C] LISTGROUP example.empty.newsgroup
[S] 412 No current article selected
9.5.2 The OVER Extension
This extension provides two commands, OVER and LIST
OVERVIEW.FMT. The label for this extension is OVER.
9.5.2.1 LIST OVERVIEW.FMT
LIST OVERVIEW.FMT
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The overview.fmt file is maintained by some news transport
systems to contain the order in which header information is
stored in the overview databases for each news group. When
executed, news article header fields are displayed one line at
a time in the order in which they are stored in the overview
database[6] following the 215 response. When display is
completed, the server will send a period on a line by itself.
If the information is not available, the server will return
the 503 response.
If the header has the word "full" (without quotes) after the
colon, the header's name is prepended to its field in the
output returned by the server.
This is command is part of the optional OVER extension which
includes the OVER command defined in section . If the OVER
extension is not implemented, then this command MUST NOT be
implemented. If that case, the server MUST return a 501 error
response when this command is presented by the client.
9.5.2.1.1 Responses
215 information follows
501 Syntax Error
503 program error, function not performed
9.5.2.1.2 Examples
Example of LIST OVERVIEW.FMT returning a list of news groups
[S] 200 NNTP Service Ready
[C] LIST OVERVIEW.FMT
[S] 215 Order of fields in overview database.
[S] Subject:
[S] From:
[S] Date:
[S] Message-ID:
[S] .
Example of LIST OVERVIEW.FMT returning an error
[S] 200 NNTP Service Ready
[C] LIST OVERVIEW.FMT
[S] 503 program error, function not performed
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9.5.2.2 OVER
OVER [range]
The OVER command returns specific header information for the
article(s) specified from the current selected group. The
information returned in the response to this command can be
used by clients to follow discussion threads.
The optional range argument may be any of the following:
o an article number
o an article number followed by a dash to indicate all
following
o an article number followed by a dash followed by another
article number
If no argument is specified, then information from the current
article is displayed. Successful responses start with a 224
response followed by the overview information for all matched
messages. Once the output is complete, a period is sent on a
line by itself. If no argument is specified, the information
for the current article is returned. A news group must have
been selected earlier, else a 412 error response is returned.
If no articles are in the range specified, the server returns
a 420 error response. A 502 response will be returned if the
client only has permission to transfer articles. A 500
response SHOULD be returned by servers do not implement this
command.
The output consists of one line per article, sorted in
numerical order of article number. Each line consists of a
number of fields separated by an US-ASCII TAB character. The
first 8 fields MUST be the following, in order:
article number, subject, author, date, message-ID, references,
byte count, line count
The content of any subsequent field is given by the response
to the LIST OVERVIEW.FMT command. A field may be empty (in
which case there will be two adjacent US-ASCII tabs, and a
sequence of trailing US-ASCII tabs may be omitted). Any
sequence of US-ASCII space or non-printing characters in a
field MUST be replaced by a single US-ASCII space.
The server SHOULD not produce output for articles that no
longer exist.
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9.5.2.2.1 Responses
224 Overview information follows
412 No news group current selected
420 No article(s) selected
500 Command not recognized
502 Service Unavailable
9.5.2.2.2 Examples
Example of a successful retrieval of overview information for
an article (using no article number)
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] OVER
[S] 224 Overview information follows
300234|I am just a test article|nobody@nowhere.to
(Demo User)|6 Oct 1998 04:38:40 -0500|
<45223423@to.to>
[S] .
[Please note that the line that begins with 300234 is all one
line that has been wrapped for readability. A vertical bar has
been inserted to show where the US-ASCII TAB should actually
be.]
Example of an unsuccessful retrieval of overview information
on an article by number
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] OVER 300256
[S] 420 No such article in this group
Example of an unsuccessful retrieval of overview information
by number because no news group was selected first
[S] 200 NNTP Service Ready
[C] OVER
[S] 412 No news group selected
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Example of an attempt to retrieve an article when the current
group selected is empty
[S] 200 NNTP Service Ready
[C] GROUP example.empty.newsgroup
[S] 211 0 0 0 example.empty.newsgroup
[C] OVER
[S] 420 No current article selected
9.5.3 The PAT Extension
This extension provides one new command, PAT. The label for
this extension is PAT.
9.5.3.1 PAT
PAT header range|<message-id> [wildmat]
The PAT command is used to retrieve specific headers from
specific articles in the currently selected group, based on
pattern matching on the contents of the header.
The required header parameter is the name of a header line
(e.g. "subject") in a news group article. See RFC-1036 for a
list of valid header lines. The required range argument may be
any of the following:
o an article number
o an article number followed by a dash to indicate all
following
o an article number followed by a dash followed by another
article number.
The required message-id argument indicates a specific article.
The range and message-id arguments are mutually exclusive.
Additional arguments consisting of one or more wildmats,
separated by an US-ASCII space, may be specified. The default
is the single wildmat "*".
A successful response consists of a 221 code followed by the
output from the command. The output consists of one line for
each article where the relevant header line matches one or
more of the wildmats. The line consists of the article number,
a US-ASCII space, and then the contents of the header (without
the header name). A valid response includes an empty list
(indicating that there were no matches). Once the output is
complete, a period is sent on a line by itself. If the
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optional argument is a message-id and no such article exists,
a 430 error response shall be returned. A 502 response shall
be returned if the client only has permission to transfer
articles. A 500 response SHOULD be issued by all servers that
do not recognize this command.
9.5.3.1.1 Responses
221 Header follows
412 no newsgroup selected
430 no such article
500 Command not recognized
502 Service Unavailable
9.5.3.1.2 Examples
Example of a successful retrieval of subject lines from a
range of articles
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] PAT Subject 3000234-300238
[S] 221 Header Follows
[S] 3000234 I am just a test article
[S] 3000237 Re: I am just a test article
[S] 3000238 Ditto
[S] .
Example of a successful retrieval of subject lines from a
range of articles with header pattern matching
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] PAT Subject 3000234-300238 *j*
[S] 221 Header Follows
[S] 3000234 I am just a test article
[S] 3000237 Re: I am just a test article
[S] .
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Example of a successful retrieval of header from an article by
message-id
[S] 200 NNTP Service Ready
[C] GROUP misc.test
[S] 211 1234 3000234 3002322 misc.test
[C] PAT subject <i.am.a.test.article@nowhere.to>
[S] 221 Header information follows
[S] 3000345 I am just a test article
[S] .
Example of an unsuccessful retrieval of a header from an
article by message-id
[S] 200 NNTP Service Ready
[C] PAT subject <i.am.not.there@nowhere.to>
[S] 430 No Such Article Found
Example of an unsuccessful retrieval of headers from articles
by number because no news group was selected first
[S] 200 NNTP Service Ready
[C] PAT subject 300256-
[S] 412 No news group selected
Example of an unsuccessful retrieval of headers from articles
by message-id because no news group was selected first
[S] 200 NNTP Service Ready
[C] PAT subject <i.am.a.test.article@nowhere.to>
[S] 412 No news group selected
Example of retrieving header information when the current
group selected is empty
[S] 200 NNTP Service Ready
[C] GROUP example.empty.newsgroup
[S] 211 0 0 0 example.empty.newsgroup
[C] PAT subject 0-
[S] 221 Headers follow
.
Example of a failure due to restrictions configured into the
server
[S] 200 NNTP Service Ready
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[C] GROUP news.group
[S] 211 1234 3000234 3002322 misc.test
[C] PAT Subject 3000234-300238
[S] 502 Service Unavailable
10. The CONCLUSION Step
10.1 QUIT
QUIT
The server process MUST acknowledge the QUIT command and then
close the connection to the client. This is the preferred
method for a client to indicate that it has finished all its
transactions with the NNTP server.
If a client simply disconnects (or the connection times out or
some other fault occurs), the server MUST gracefully cease its
attempts to service the client, disconnecting from its end if
necessary.
10.1.1 Responses
205 closing connection - goodbye!
10.1.2 Example
[S] 200 NNTP Service Ready
[C] QUIT
[S] 205 closing connection
11. Other Keywords
There are other keywords that may be used at any time between
the beginning of a session and its termination. Using these
keywords does not alter any state information, but the
response generated from the use of these keywords may provide
useful information to clients that use them.
11.1 DATE
DATE
This command exists to help clients find out the current time
from the server's perspective. This command SHOULD NOT be
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used as a substitute for NTP[7], but to provide information
that might be useful when using the NEWNEWS command (see
section 11.4).
This command returns a one-line response code of 111 followed
by the UTC (or GMT) date and time on the server in the form
YYYYMMDDhhmmss.
11.1.1 Responses
111 YYYYMMDDhhmmss
11.1.2 Example
[S] 200 NNTP Service Ready
[C] DATE
[S] 111 19990623135624
11.2 The HELP Command
HELP
This command provides a short summary of commands that are
understood by this implementation of the server. The help text
will be presented as a textual response terminated by a single
period on a line by itself.
This text is not guaranteed to be in any particular format and
SHALL NOT be used by clients as a replacement for the LIST
EXTENSIONS command described in section 8.1.
11.2.1 Responses
100 help text follows
11.2.2 Example
[S] 200 NNTP Service Ready
[C] HELP
[S] 100 Help text follows
[S] This is some help text. There is no specific
[S] formatting requirement for this test, though
[S] it is customary for it to list the valid commands
[S] and give a brief definition of what they do
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[S] .
11.3 NEWGROUPS
NEWGROUPS date time [GMT|UTC]
A list of newsgroups created since <date and time> MUST be
listed in the same format as the LIST command.
The date is sent as 6 or 8 digits in the format [XX]YYMMDD,
where XX is the first two digits of the year, YY is the last
two digits of the year, MM is the two digits of the month
(with leading zero, if appropriate), and DD is the day of the
month (with leading zero, if appropriate). If the first two
digits of the year are not specified, the year is to be taken
from the current century if YY is smaller than or equal to the
current year, otherwise the year is from the previous century.
Time must also be specified. It must be as 6 digits HHMMSS
with HH being hours in the 24-hour clock 00-23, MM minutes 00-
59, and SS seconds 00-60, which allows for leap seconds. The
tokens "GMT" and "UTC" specifies that the date and time are
given in UTC. If the tokens "GMT" and "UTC" are omitted then
the date and time are specified in the server's local
timezone. Note that there is no way within this specification
of NNTP to establish the server's local timezone.
Note that an empty list (i.e., the text body returned by this
command consists only of the terminating period) is a possible
valid response, and indicates that there are currently no new
newsgroups.
Clients SHOULD make all queries using GMT/UTC time when
possible.
11.3.1 Responses
231 list of new newsgroups follows
11.3.2 Examples
Example where there are new groups
[S] 200 NNTP Service Ready
[C] NEWGROUPS 19990624 000000 UTC
[S] 230 list of new newsgroups follows
[S] alt.rfc-writers.recovery
[S] tx.natives.recovery
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[S] .
Example where there are no new groups
[S] 200 NNTP Service Ready
[C] NEWGROUPS 19990624 000000 UTC
[S] 230 list of new newsgroups follows
[S] .
11.4 NEWNEWS
NEWNEWS newsgroups date time [GMT]
A list of message-ids of articles posted or received to the
specified news group or groups since "date" will be listed.
The format of the listing will be one message-id per line, as
though text were being sent. Each message-id SHALL appear only
once in a response. The order of the response has no specific
significance and may vary from response to response in the
same session. A single line consisting solely of one period
followed by CR-LF will terminate the list.
Date and time are in the same format as the NEWGROUPS command.
The newsgroups parameter MUST be in wildmat format and MAY
consist of multiple wildmat constructs separated by an US-
ASCII comma character.
Note that an empty list (i.e., the text body returned by this
command consists only of the terminating period) is a possible
valid response, and indicates that there is currently no new
news.
Clients SHOULD make all queries in GMT/UTC time when possible.
11.4.1 Responses
230 list of new articles by message-id follows
11.4.2 Examples
Example where there are new articles
[S] 200 NNTP Service Ready
[C] NEWNEWS news.*,sci.* 19990624 000000
[S] 230 list of new articles by message-id follows
[S] <i.am.a.new.article@nowhere.to>
[S] <i.am.another.new.article@nowhere.to>
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Example where there are no new articles
[S] 200 NNTP Service Ready
[C] NEWNEWS alt.* 19990624 000000
[S] 230 list of new articles by message-id follows
[S] .
12. Framework for NNTP Extensions
Although NNTP is widely and robustly deployed, some parts of
the Internet community might wish to extend the NNTP service.
This memo defines a means whereby an extended NNTP client may
query the server to determine the service extensions that it
supports.
It must be emphasized that any extension to the NNTP service
should not be considered lightly. NNTP's strength comes
primarily from its simplicity. Experience with many protocols
has shown that:
Protocols with few options tend towards ubiquity, whilst
protocols with many options tend towards obscurity.
This means that each and every extension, regardless of its
benefits, must be carefully scrutinized with respect to its
implementation, deployment, and interoperability costs. In
many cases, the cost of extending the NNTP service will likely
outweigh the benefit.
Given this environment, the framework for the extensions
described in this memo consists of:
a)a mechanism for clients to determine a server's available
extensions
b)a registry of NNTP service extensions
The LIST EXTENSIONS command is described in section 8.1 of
this memo and is the mechanism for clients to use to determine
what extensions are available for client use.
The IANA shall maintain a registry of NNTP service extensions.
An extension is identified by an unique extension-label, which
is an string of 1 to 12 uppercase letters. The extension-label
will often be the name of a new command that the extension
adds. However this is not a requirement: an extension might
not add any new commands or keywords.
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October 2000
An extension is either a private extension or else it is
included in the IANA registry and is defined in an RFC. Such
RFCs either must be on the standards-track or must define an
IESG-approved experimental protocol.
The definition of an extension must include:
o a descriptive name for the extension
o the extension-label (which is returned by LIST EXTENSIONS
to
o indicate to the client that the server supports this
particular extension)
o the syntax, values, and meanings of any parameters
following the extension-label in the output of LIST
EXTENSIONS
o any new NNTP keywords associated with the extension
o the syntax and possible values of parameters associated
with the new NNTP keywords
o any new parameters the extension associates with any
other pre-existing NNTP keywords
o how support for the extension affects the behavior of a
server and client NNTP
o any increase in the maximum length of commands over the
value specified in this memo
The extension-label of private extensions MUST begin with "X".
The extension-label of registered extensions MUST NOT begin
with "X".
Any keyword values presented in the NNTP response that do not
begin with "X" MUST correspond to a standard, standards-track,
or IESG-approved experimental NNTP service extension
registered with IANA. A conforming server MUST NOT offer non
"X" prefixed keyword values that are not described in a
registered extension.
Except where stated otherwise, the commands in this document
are understood (even if not supported) by all servers and are
not described in the list of features returned by the LIST
EXTENSIONS command.
A server MAY provide additional keywords - either new commands
or new parameters to existing commands - as part of a private
extension. These new keywords MUST begin with "X".
A server MUST NOT send different response codes to basic NNTP
commands documented here or commands documented in registered
extensions in response to the availability or use of a private
extension.
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October 2000
12.1 Initial IANA Registry
The IANA's initial registry of NNTP service extensions
consists of these entries:
Service Extension NNTP Extension Label Added Behavior
----------------- -------------------- ---------------
Overview Support OVER Defined in this
document
Specific Article LISTGROUP Defined in this
Numbers document
Header Pattern PAT Defined in this
Matching document
13. Augmented BNF[8] Syntax for NNTP Commands
This syntax defines the non-terminal "command". The non-terminal
"parameter" is used for command parameters whose syntax is
specified elsewhere. The syntax is in alphabetical order. Note
that ABNF strings are case insensitive.
article-command = "ARTICLE" [1*WSP (msg-id / article-number)]
*WSP CRLF
article-number = 1*16DIGIT
argument = parameter ; excluding sequence ".."
body-command = "BODY" [1*WSP (msg-id / article-number)] *WSP
CRLF
command = article-command /
body-command /
date-command /
group-command /
head-command /
help-command /
ihave-command /
last-command /
list-active-times-command /
list-distrib-pats-command /
list-distributions-command /
list-extensions-command /
list-newsgroups-command /
list-overview-fmt-command /
list-command /
listgroup-command /
mode-reader-command /
newgroups-command /
newnews-command /
next-command /
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over-command /
pat-command /
post-command /
quit-command /
stat-command
CR = %x0D
CRLF = CR LF
date-command = "DATE" *WSP CRLF
date = 6*8DIGIT
DIGIT = %x30-39
group-command = "GROUP" 1*WSP newsgroup *WSP CRLF
head-command = "HEAD" [1*WSP (msg-id / article-number)] *WSP
CRLF
header = parameter
help-command = "HELP" *WSP CRLF
HT = %x09
ihave-command = "IHAVE" 1*WSP msg-id *WSP CRLF
last-command = "LAST" *WSP CRLF
LF = %x0A
list-active-times-command = "LIST" 1*WSP "ACTIVE.TIMES"
[1*WSP wildmat] *WSP CRLF
list-command = "LIST" [1*WSP "ACTIVE" [1*WSP wildmat]] *WSP
CRLF
list-distrib-pats-command = "LIST" 1*WSP "DISTRIB.PATS" *WSP
CRLF
list-distributions-command = "LIST" 1*WSP "DISTRIBUTIONS" *WSP
CRLF
list-extensions-command = "LIST" 1*WSP "EXTENSIONS" *WSP CRLF
list-newsgroups-command = "LIST" 1*WSP "NEWSGROUPS" [1*WSP
wildmat]
*WSP CRLF
list-overview-fmt-command = "LIST" 1*WSP "OVERVIEW.FMT" *WSP
CRLF
listgroup-command = "LISTGROUP" [1*WSP newsgroup] *WSP CRLF
mode-reader-command = "MODE" 1*WSP "READER" *WSP CRLF
msg-id = <defined in RFC822>
newgroups-command = "NEWGROUPS" 1*WSP date 1*WSP time [1*WSP
"GMT"/"UTC"] *WSP CRLF
newnews-command = "NEWNEWS" 1*WSP newsgroup *("," newsgroup)
1*WSP date 1*WSP time [1*WSP "GMT"/"UTC"]
*WSP CRLF
newsgroup = parameter
next-command = "NEXT" *WSP CRLF
over-command = "OVER" [1*WSP range] *WSP CRLF
parameter = 1*(%x21-FF) ; generic command parameter
pat-command = "PAT" 1*WSP header 1*WSP (range / msg-id)
*(1*WSP wildmat) *WSP CRLF
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post-command = "POST" *WSP CRLF
quit-command = "QUIT" *WSP CRLF
range = article-number ["-" [article-number]]
SP = %x20
stat-command = "STAT" [1*WSP (msg-id / article-number)] *WSP
CRLF
time = 6DIGIT
UTF-8-non-ascii = UTF8-2 / UTF8-3 / UTF8-4 / UTF8-5 / UTF8-6
UTF8-1 = %x80-BF
UTF8-2 = %xC0-DF UTF8-1
UTF8-3 = %xE0-EF 2UTF8-1
UTF8-4 = %xF0-F7 3UTF8-1
UTF8-5 = %xF8-FB 4UTF8-1
UTF8-6 = %xFC-FD 5UTF8-1
wildmat = ["!"]1*("*" / "?" / wildmat-exact / wildmat-set /
"\" (%x22-7F / UTF-8-non-ascii))
wildmat-exact = %x22-29 / %x2B-3E / %x40-5A / %x5D-7F / UTF-8-
non-ascii ; exclude space ! * ? [ \
wildmat-non-hyphen = %x21-2C / %x2E-7F / UTF-8-non-ascii ;
exclude space -
wildmat-set = "[" ["^"] ["]" / "-"] *(wildmat-non-hyphen"["-"
wildmat-non-hyphen]) ["-"]
WSP = SP / HT
14. Security Considerations
This section is meant to inform application developers,
information providers, and users of the security limitations
in NNTP as described by this document. The discussion does not
include definitive solutions to the problems revealed, though
it does make some suggestions for reducing security risks.
14.1 Personal and Proprietary Information
NNTP, because it was created to distribute network news
articles, will forward whatever information is stored in those
articles. Specification of that information is outside this
scope of this document, but it is likely that some personal
and/or proprietary information is available in some of those
articles. It is very important that designers and implementers
provide informative warnings to users so personal and/or
proprietary information is not disclosed inadvertently.
Additionally, effective and easily understood mechanisms to
manage the distribution of news articles must be provided to
NNTP Server administrators, so that they are able to report
with confidence what information is and is not being forwarded
in news articles passing though their servers.
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14.2 Abuse of Server Log Information
A server is in the position to save session data about a
user's requests that might identify their reading patterns or
subjects of interest. This information is clearly confidential
in nature and its handling can be constrained by law in
certain countries. People using the NNTP protocol to provide
data are responsible for ensuring that such material is not
distributed without the permission of any individuals that are
identifiable by the published results.
14.3 DNS Spoofing
Clients and Servers using NNTP rely heavily on the Domain Name
Service, and are thus generally prone to security attacks
based on the deliberate misassociation of IP addresses and DNS
names. Clients and Servers need to be cautious in assuming the
continuing validity of an IP number/DNS name association.
In particular, NNTP clients and servers SHOULD rely on their
name resolver for confirmation of an IP number/DNS name
association, rather than caching the result of previous host
name lookups. Many platforms already can cache host name
lookups locally when appropriate, and they SHOULD be
configured to do so. It is proper for these lookups to be
cached, however, only when the TTL (Time To Live) information
reported by the name server makes it likely that the cached
information will remain useful.
If NNTP clients or servers cache the results of host name
lookups in order to achieve a performance improvement, they
MUST observe the TTL information reported by DNS.
If NNTP clients or servers do not observe this rule, they
could be spoofed when a previously-accessed server's IP
address changes. As network renumbering is expected to become
increasingly common, the possibility of this form of attack
will grow. Observing this requirement thus reduces this
potential security vulnerability.
This requirement also improves the load-balancing behavior of
clients for replicated servers using the same DNS name and
reduces the likelihood of a user's experiencing failure in
accessing sites which use that strategy.
14.4 Weak Authentication and Access Control
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There is no user-based or token-based authentication in the
basic NNTP specification. Access is normally controlled by
server configuration files. Those files specify access by
using domain names or IP addresses. However, this
specification does permit the creation of extensions to the
NNTP protocol itself for such purposes. While including such
mechanisms is optional, doing so is strongly encouraged.
Other mechanisms are also available. For example, a proxy
server could be put in place that requires authentication
before connecting via the proxy to the NNTP server.
15. References
[1] Kantor, B and P. Lapsley, "Network News Transfer Protocol",
RFC-977, U.C. San Diego and U.C. Berkeley.
[2] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
RFC 2279, Alis Technologies.
[3] Coded Character Set-7-bit American Standard Code for
Information Interchange, ANSI x3.4-1986.
[4] Bradner, Scott, "Key words for use in RFCs to Indicate
Requirement Levels", RFC-2119, Harvard University.
[5] Salz, Rich, Manual Page for wildmat(3) from the INN 1.4
distribution, UUNET Technologies, Revision 1.10, April, 1992.
[6] Robertson, Rob, "FAQ: Overview database / NOV General
Information", ftp://ftp.uu.net/networking/news/nntp/inn/faq-
nov.Z, January, 1995.
[7] Mills, David L., "Network Time Protocol (Version 3),
Specification, Implementation and Analysis", RFC-1305,
University of Delaware, March 1992.
[8] Crocker, D. and Overell, P., "Augmented BNF for Syntax
Specifications: ABNF", RFC-2234, Internet Mail Consortium and
Demon Internet, Ltd.
16. Notes
UNIX is a registered trademark of the X/Open Consortium.
17. Acknowledgments
The author acknowledges the original authors of NNTP as
documented in RFC 977: Brian Kantor and Phil Lapsey.
The author gratefully acknowledges the work of the NNTP
committee chaired by Eliot Lear. The organization of this
document was influenced by the last available draft from this
working group. A special thanks to Eliot for generously
providing the original machine readable sources for that
document.
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October 2000
The author gratefully acknowledges the work of the Marshall
Rose & John G. Meyers in RFC 1939 and the work of the DRUMS
working group, specifically RFC 1869, which is the basis of
the NNTP extensions mechanism detailed in this document.
The author gratefully acknowledges the authors of RFC 2616 for
providing specific and relevant examples of security issues
that should be considered for HTTP. Since many of the same
considerations exist for NNTP, those examples that are
relevant have been included here with some minor rewrites.
The author gratefully acknowledges the comments and additional
information provided by the following individuals in preparing
one of the progenitors of this document:
o Wayne Davison <davison@armory.com>
o Clive D.W. Feather <clive@demon.net>
o Chris Lewis <clewis@bnr.ca>
o Tom Limoncelli <tal@mars.superlink.net>
o Eric Schnoebelen <eric@egsner.cirr.com>
o Rich Salz <rsalz@osf.org>
This work was motivated by the work of various newsreader
authors and newsserver authors, which includes those listed
below:
o Rick Adams-Original author of the NNTP extensions to the
RN newsreader and last maintainer of Bnews
o Stan Barber-Original author of the NNTP extensions to the
newsreaders that are part of Bnews.
o Geoff Collyer-Original author of the OVERVIEW database
proposal and one of the original authors of CNEWS
o Dan Curry-Original author of the xvnews newsreader
o Wayne Davison-Author of the first threading extensions to
the RN newsreader (commonly called TRN).
o Geoff Huston-Original author of ANU NEWS
o Phil Lapsey-Original author of the UNIX reference
implementation for NNTP
o Iain Lea-Original maintainer of the TIN newsreader
o Chris Lewis-First known implementor of the AUTHINFO
GENERIC extension
o Rich Salz-Original author of INN
o Henry Spencer-One of the original authors of CNEWS
o Kim Storm-Original author of the NN newsreader
18.Author's Address
Stan Barber
P.O. Box 300481
Houston, Texas 77230
Email: <sob@academ.com>
This document expires May 30, 2001.
Barber [Page 60]
