INTERNET DRAFT S. Barber Expires: January 15, 2001 Academ Consulting Services July 2000 Network News Transport Protocol draft-ietf-nntpext-base-10.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 database, giving subscribers the ability to select only those articles they wish to read. Barber [Page 1] INTERNET DRAFT July 2000 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: CONNECTION GREETING Barber [Page 2] INTERNET DRAFT July 2000 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. Unless specifically specified as one of the valid responses for a command (such as those described later in this document), each response is contained in a single line. However, certain responses from commands may be multi-line. All multi-line 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 Barber [Page 3] INTERNET DRAFT July 2000 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. The keywords that support multi-line responses have the format of those responses described in the responses section. 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 x1x - Newsgroup selection x2x - Article selection x3x - Distribution functions x4x - Posting x8x - Nonstandard (private implementation) extensions x9x - Debugging output Barber [Page 4] INTERNET DRAFT July 2000 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. In addition, there is a debugging set of response codes that MAY be received at any time. These are described later in this section. Certain response codes contain parameters such as numbers and names in addition to the status indicator. In those cases, the number and type of such parameters MUST be fixed for each response code to simplify interpretation of the response. In all other cases, the client MUST only use the status indicator itself to determine the nature of the response. 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. All string parameters MUST begin after the separating space, and MUST end before the following separating space or the US-ASCII CRLF pair at the end of the line. (Therefore, string parameters MUST NOT contain US-ASCII spaces.) All text, if any, in the response which is not a parameter of the response must follow and be separated from the last parameter by an US-ASCII space. Also, note that the text following a response number may vary in different implementations of the server. The 3-digit numeric status indicator should be used to determine what response was sent. 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 x8x specified above. (Note that debugging is provided for explicitly in the x9x response codes.) The use of unspecified response codes for a standard command is prohibited. The status indicator pattern x9x is provided for debugging. Since much debugging output may be classed as "informative messages", it MUST be the case that responses 190 through 199 WILL be used for various debugging outputs. There is no requirement in this specification for debugging output. However, if such is provided over the connected stream, it MUST use these response codes. If appropriate to a specific implementation, other x9x codes MAY be used for debugging. (For example, response code 290 could be used to acknowledge a remote debugging request.) By default, a server implementation MUST NOT send debugging responses. Such behavior MUST only occur when specifically activated. See section XX for information on the DEBUG command. A server MUST respond to an unrecognized, unimplemented, or syntactically invalid command with a negative response code (status indicators of the form 5XX). For unrecognized commands, the 500 response code MUST be returned. This Barber [Page 5] INTERNET DRAFT July 2000 includes servers that have not implemented the optional extensions outlined later in this memo. For recognized commands where the syntax is wrong, the 501 response code MUST be returned. A server MUST respond to a command issued when the session is in an incorrect state by responding with a negative status indicator. This may be from either the 4XX or 5XX group as appropriate. 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. 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. Barber [Page 6] INTERNET DRAFT July 2000 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. Any parameters are shown in lower case. A parameter shown in [square brackets] is optional. For example,[wildmat] indicates that a wildmat may be present or omitted. A parameter that may be repeated is followed by an ellipsis. Mutually exclusive parameters are separated by a vertical bar (|) character. For example, ggg| indicates that a group name or a may be specified, but not both. Unless stated otherwise, a parameter name in lowercase represents a token described elsewhere, while one in uppercase is a literal string that is included as written. Some parameters may be case or language specific. See RFC 1036[6] for these details. In addition, certain commands make use of a pattern for selection of multiple news groups. The pattern in all cases is based on the WILDMAT format. Arguments expected to be in wildmat format will be represented by the string wildmat. This format is discussed in detail in section 5 of this memo. 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. Barber [Page 7] INTERNET DRAFT July 2000 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 504 greeting code and then immediately close the connection. 504 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 10.1). [C] QUIT [S] 205 NNTP Service exits normally Example of a normal connection from an unauthorized client [C] Initial TCP connection completed [S] 504 NNTP 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] 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 10.1). [C] QUIT Barber [Page 8] INTERNET DRAFT July 2000 [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 MAY be used by the client to indicate to the server that it is a news reading client. This command may be entered at any time. The server MUST present a greeting code (as described in section 7.1.2.1) appropriate to the server's ability to provide service to this client in this mode. 7.1.2.1 Responses 200 Hello, you can post 201 Hello, you can't post 400 Service temporarily unavailable 502 Service unavailable 7.1.2.2 MODE READER Examples Example of use of the MODE READER command by an authorized client [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 10.1). [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 Barber [Page 9] INTERNET DRAFT July 2000 [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 10.1). [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 A client NNTP supporting NNTP service extensions should query a server early in the session for extensions session by issuing the LIST EXTENSIONS command. If the NNTP server supports the NNTP service extensions it 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). If the NNTP server does not support any NNTP service extensions, it MUST generate an error response (see section 8.1.4). 8.1 LIST EXTENSIONS If successful, the server NNTP MUST respond with code 202. On failure, the server NNTP MUST respond with code 503. On error, Barber [Page 10] INTERNET DRAFT July 2000 the server NNTP MUST respond with one of codes 400, 402, 500, 501 and 502. 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 If the server NNTP implements and is able to perform the LIST EXTENSIONS command, it MUST return code 202. Text following the return code on the first line of the reply is free form, and not interpreted, and has no practical use, as this text is not expected to be revealed to end users. The syntax of other reply lines is precisely defined, and if present, MUST be exactly as specified. Each line listing an extension in the extension-listing begins with a single space. That space IS NOT optional, nor does it indicate general white space. This space guarantees that the line can never be misinterpreted as the end of the extension- listing, but is required even where there is no possibility of ambiguity. Each extension supported MUST be listed on a separate line to facilitate the possible inclusion of parameters supported by each extension command. The extension-label to be used in the response to the LIST EXTENSIONS command will be specified as each new extension is added to the NNTP command set. Often it will be the name of a new command added; however this IS NOT required. In fact, it IS NOT required that a new feature actually adds a new command or keyword. Any parameters included are to be specified with the definition of the command concerned. That specification SHALL also specify how any parameters present are to be interpreted and how each parameter is separated from other parameters. The extension-label is nominally case insensitive, however the definitions of specific labels and parameters specify the precise interpretation, and it is to be expected that those definitions will usually specify the label in a case Barber [Page 11] INTERNET DRAFT July 2000 independent manner. Where this is done, implementations are recommended to use US-ASCII upper case letters when transmitting the extension response. 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. 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 [S] 202 Extensions supported: [S] OVER [S] PAT [S] LISTGROUP [S] . The particular extensions shown here are simply examples of what may be defined in other places, no particular meaning should be attributed to them. Recall also, that the extension names returned are not command names, as such, but simply indications that the server possesses some attribute or other. The order in which the extensions are returned is of no importance, NNTP server processes are not required to implement any particular order, or even to consistently return the same order when the command is repeated. 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. Barber [Page 12] INTERNET DRAFT July 2000 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 servers without extensions A server NNTP that conforms to this memo but does not support the extensions specified here will not recognize the LIST EXTENSIONS command and MUST consequently return code 500 or code 501. The server NNTP SHALL stay in the same state after returning this code. The client NNTP may try the extensions either as the need arises or configure itself for the basic NNTP functionality defined in this document. 8.1.5 Responses from improperly implemented servers 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. Barber [Page 13] INTERNET DRAFT July 2000 9. The NEWS EXCHANGE Step During this step, two basic types of transactions occur: . article retrieval from the server . 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 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. Barber [Page 14] INTERNET DRAFT July 2000 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. . 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. . All three numbers will be zero. . 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: . articles may be removed from the group . 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) . 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. Barber [Page 15] INTERNET DRAFT July 2000 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.) 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. Barber [Page 16] INTERNET DRAFT July 2000 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 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 Barber [Page 17] INTERNET DRAFT July 2000 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 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 Barber [Page 18] INTERNET DRAFT July 2000 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 [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> Barber [Page 19] INTERNET DRAFT July 2000 [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 There are two forms to the ARTICLE command (and the related BODY, HEAD, and STAT commands), each using a different method of specifying the article to be retrieved. The first form specifies the article by using an argument which consists of a message-id in angle brackets ("<" and ">"). The article number specified in the response to this form of the command must be zero. The second form requires that the current news group be valid and specifies the message by using a numeric parameter or no parameter at all. An article, as defined by RFC 1036, consists of two parts: the article headers and the article body. When responding to an article command, the server returns the entire article contents and does not attempt to alter or translate them in any way. 9.2.1 ARTICLE ARTICLE [|nnn] This response displays the header, a blank line, then the body (text) of the specified article. The optional parameter nnn is the numeric id of an article in the current news group and Barber [Page 20] INTERNET DRAFT July 2000 should be chosen from the range of articles provided when the news group was selected. If it is omitted, the current article is assumed. Message-id is the message id of an article as shown in that article's header. The internally maintained "current article pointer" MUST NOT be altered when the message-id argument is used. This is both to facilitate the presentation of articles that may be referenced within an 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. When a valid article number is specified as the argument, the internally-maintained "current article pointer" MUST be set to point to retrieve article. This includes the case when an article number is implied by the use of no argument. 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. If there is a valid article to present in a reply to this command, a response indicating the current article number (or zero when the message-id argument is used), a message-id string, and that text is to follow MUST be returned. The message-id string is an identification string contained within angle brackets ("<" and ">"), which is derived from the header of the article itself. The Message-ID header line (required by RFC 1036) from the article must be used to supply this information. If the message-id header line is missing from the article, a single digit "0" (zero) should be supplied within the angle brackets. Since the message-id field is unique for each article, it may be used by a news reading program to skip duplicate displays of articles that have been posted more than once, or to more than one news group. 9.2.1.1 Responses 220 n article retrieved - head and body follow (n = article number, = message-id) 412 no news group has been selected 420 no current article has been selected 423 no such article number in this group 430 no such article found 502 Service unavailable Barber [Page 21] INTERNET DRAFT July 2000 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> [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 Barber [Page 22] INTERNET DRAFT July 2000 [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 [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 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 Barber [Page 23] INTERNET DRAFT July 2000 [C] ARTICLE [S] 502 Service unavailable 9.2.2 HEAD HEAD [|nnn] This response displays the header of the specified article. The optional parameter nnn is the numeric id of an article in the current news group and should be chosen from the range of articles provided when the news group was selected. If it is omitted, the current article is assumed. Message-id is the message id of an article as shown in that article's header. The internally maintained "current article pointer" MUST NOT be altered when the message-id argument is used. This is both to facilitate the presentation of articles that may be referenced within an 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. When a valid article number is specified as the argument, the internally-maintained "current article pointer" MUST be set to point to the retrieved article. This includes the case when an article number is implied by the use of no argument. 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. If there is a valid article to present in a reply to this command, a response indicating the current article number (or zero when the message-id argument is used), a message-id string, and that text is to follow MUST be returned. The message-id string returned is an identification string contained within angle brackets ("<" and ">"), which is derived from the header of the article itself. The Message-ID header line (required by RFC 1036) from the article must be used to supply this information. If the message-id header line is missing from the article, a single digit "0" (zero) should be supplied within the angle brackets. Since the message-id field is unique for each article, it may be used by a news reading program to skip duplicate displays of articles that have been posted more than once, or to more than one news group. Barber [Page 24] INTERNET DRAFT July 2000 9.2.2.1 Responses 221 n article retrieved - head follows 412 no news group has been selected 420 no current article has been selected 423 no such article number in this group 430 no such article found 502 Service unavailable 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 Barber [Page 25] INTERNET DRAFT July 2000 [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 [S] 430 No Such Article Found 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 Barber [Page 26] INTERNET DRAFT July 2000 [S] 200 NNTP Service Ready [C] HEAD [S] 502 Service unavailable 9.2.3 BODY BODY [|nnn] This response displays the body (text) of the specified article. The optional parameter nnn is the numeric id of an article in the current news group and should be chosen from the range of articles provided when the news group was selected. If it is omitted, the current article is assumed. Message-id is the message id of an article as shown in that article's header. The internally maintained "current article pointer" MUST NOT be altered when the message-id argument is used. This is both to facilitate the presentation of articles that may be referenced within an 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. When a valid article number is specified, the internally- maintained "current article pointer" MUST be set point to the retrieve article. This includes the case when an article number is implied by the use of no argument. 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. If there is a valid article to present in a reply to this command, a response indicating the current article number (or zero when the message-id argument is used), a message-id string, and that text is to follow MUST be returned. The message-id string returned is an identification string contained within angle brackets ("<" and ">"), which is derived from the header of the article itself. The Message-ID header line (required by RFC 1036) from the article must be used to supply this information. If the message-id header line is missing from the article, a single digit "0" (zero) should be supplied within the angle brackets. Since the message-id field is unique for each article, it may be used by a news reading program to skip duplicate displays of articles that have been posted more than once, or to more than one news group. Barber [Page 27] INTERNET DRAFT July 2000 9.2.3.1 Responses 222 n article retrieved - body follows 412 no news group has been selected 420 no current article has been selected 423 no such article number in this group 430 no such article found 502 Service unavailable 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 [S] 430 No Such Article Found Example of an unsuccessful retrieval of the body of an article by number [S] 200 NNTP Service Ready [C] GROUP misc.test Barber [Page 28] INTERNET DRAFT July 2000 [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 [S] 502 Service unavailable 9.2.4 STAT STAT [|nnn] This response returns only status information; no article contents are returned. The optional parameter nnn is the numeric id of an article in the current news group and should be chosen from the range of articles provided when the news group was selected. If it is omitted, the current article is assumed. Message-id is the message id of an article as shown in that article's header. The internally maintained "current article pointer" MUST NOT be altered when the message-id argument is used. This is both to facilitate the presentation of articles that may be referenced within an 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. Barber [Page 29] INTERNET DRAFT July 2000 When a valid article number is specified, the internally- maintained "current article pointer" MUST be set point to the retrieved article. This includes the case when an article number is implied by the use of no argument. 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. If there is a valid article to present in a reply to this command, a response indicating the current article number (or zero when the message-id argument is used) and a message-id string MUST be returned. The message-id string returned is an identification string contained within angle brackets ("<" and ">"), which is derived from the header of the article itself. The Message-ID header line (required by RFC 1036) from the article must be used to supply this information. If the message-id header line is missing from the article, a single digit "0" (zero) should be supplied within the angle brackets. Since the message-id field is unique for each article, it may be used by a news reading program to skip duplicate displays of articles that have been posted more than once, or to more than one news group. 9.2.4.1 Responses 223 n article retrieved - request text separately 412 no news group has been selected 420 no current article has been selected 423 no such article number in this group 430 no such article found 502 Service unavailable 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> Barber [Page 30] INTERNET DRAFT July 2000 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 [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 [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 Barber [Page 31] INTERNET DRAFT July 2000 [S] 200 NNTP Service Ready [C] STAT [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 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 . 440 posting not allowed 441 posting failed Barber [Page 32] INTERNET DRAFT July 2000 9.3.1.2 Examples Example of a successful posting [S] 200 NNTP Service Ready [C] POST [S] 340 Input article. End with . [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 [S] 340 Input article. End with . [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 Barber [Page 33] INTERNET DRAFT July 2000 [S] 440 Posting not permitted 9.3.2 IHAVE IHAVE The IHAVE command informs the server that the client has an article whose id is . 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 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 . 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 Barber [Page 34] INTERNET DRAFT July 2000 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 [S] 335 Send it. End with . [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: [C] [C] This is just a test article. [C] . [S] 235 Article transferred ok Example of sending an article to another site that rejects it [S] 200 NNTP Service Ready [C] IHAVE [S] 335 Send it. End with . [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 Barber [Page 35] INTERNET DRAFT July 2000 [C] Date: 6 Oct 1998 04:38:40 -0500 [C] Organization: Nowhere, To [C] Message-ID: [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 [S] 335 Send it. End with . [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: [C] [C] This is just a test article. [C] . [S] 436 Transfer failed Example of sending an article to another site that rejects it [S] 200 NNTP Service Ready [C] IHAVE Barber [Page 36] INTERNET DRAFT July 2000 [S] 335 Send it. End with . [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: [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 is the name of the news group, is the number of the last known article currently in that news group, is the number of the first article currently in the news group, and indicates the current status of the group on this server. Typically, the 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. The and fields will always be numeric. They may have leading zeros. The field corresponds to the "reported low water mark" and the field corresponds to the "reported high water mark" described in the GROUP command (see Section 9.1.1.1). Barber [Page 37] INTERNET DRAFT July 2000 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] . 9.4.2 LIST ACTIVE.TIMES LIST ACTIVE.TIMES [wildmat] Barber [Page 38] INTERNET DRAFT July 2000 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 [S] alt.rfc-writers.recovery 930562309 [S] tx.natives.recovery 930678923 [S] . 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 Barber [Page 39] INTERNET DRAFT July 2000 [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 [S] na North America [S] world All over the World [S] . Barber [Page 40] INTERNET DRAFT July 2000 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. 9.4.4.1 Responses 215 information follows 501 Syntax error 503 program error, function not performed Barber [Page 41] INTERNET DRAFT July 2000 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 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 wildmat patterns Barber [Page 42] INTERNET DRAFT July 2000 (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 provided. If it is not provided, the entire section should be ignored. 9.5.1 LISTGROUP extension Barber [Page 43] INTERNET DRAFT July 2000 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 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 Barber [Page 44] INTERNET DRAFT July 2000 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 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 Barber [Page 45] INTERNET DRAFT July 2000 executed, news article header fields are displayed one line at a time in the order in which they are stored in the overview database[7] 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 9.5.2.2. 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 Barber [Page 46] INTERNET DRAFT July 2000 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: . an article number . an article number followed by a dash to indicate all following . 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. 9.5.2.2.1 Responses 224 Overview information follows 412 No news group current selected Barber [Page 47] INTERNET DRAFT July 2000 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 Barber [Page 48] INTERNET DRAFT July 2000 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| [wildmat[ 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: . an article number . an article number followed by a dash to indicate all following . 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 optional argument is a message-id and no such article exists, a 430 error response shall be returned. A 502 response shall Barber [Page 49] INTERNET DRAFT July 2000 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* ? *est [S] 221 Header Follows [S] 3000234 I am just a test article [S] 3000237 Re: I am just a test article [S] . Barber [Page 50] INTERNET DRAFT July 2000 Example of a successful retrieval of header from an article by message-id [S] 200 NNTP Service Ready [C] PAT subject [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 [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 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 [C] GROUP news.group [S] 211 1234 3000234 3002322 misc.test Barber [Page 51] INTERNET DRAFT July 2000 [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 SHALL gracefully cease its attempts to service the client. 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 used as a substitute for NTP[8], but to provide information that might be useful when using the NEWNEWS command (see section 11.5). Barber [Page 52] INTERNET DRAFT July 2000 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 DEBUG Command DEBUG ON|OFF|ACK The DEBUG command is available for implementers and system administrators to use in debugging problems with a server. A client sends the command DEBUG ON to activate the use of debugging responses. The client sends the command DEBUG OFF to deactivate the use of debugging responses. A client sends the command DEBUG ACK acknowledge the presentation of a DEBUG response code. Once a DEBUG ACK has been sent the client should expect the server to respond with another debugging result code or a response code appropriate to the command sent that started the most recent protocol transaction. Servers that recognize but are not configured to permit the use of DEBUG commands will return a 502 command when the DEBUG command is used. Servers that do not recognize the DEBUG command will return a 500 error code. 11.2.1 Responses 291 DEBUG ON Acknowledged 292 DEBUG OFF Acknowledged 500 Command not recognized 502 Service unavailable 11.2.2 Examples An example of activating, running a command and then deactivating the DEBUG responses [Different servers may have different debug response codes in use for different commands. This is just an example using code 191.] Barber [Page 53] INTERNET DRAFT July 2000 [S] 200 NNTP Service Ready [C] DEBUG ON [S] 291 DEBUG ON Acknowledged [C] GROUP misc.test [S] 191 Searching active file to see if group exists [C] DEBUG ACK [S] 211 1234 3000234 3002322 misc.test [C] DEBUG OFF [S] 292 DEBUG OFF Acknowledged An example of a negative response to DEBUG ON [The server does not disconnect after presenting the negative response.] [S] 200 NNTP Service Ready [C] DEBUG ON [S] 502 Service unavailable 11.3 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. 11.3.1 Responses 100 help text follows 11.3.2 Example [S] 200 NNTP Service Ready [C] HELP Barber [Page 54] INTERNET DRAFT July 2000 [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 [S] . 11.4 NEWGROUPS NEWGROUPS date time [GMT|UTC] A list of newsgroups created since 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. 11.4.1 Responses 231 list of new newsgroups follows 11.4.2 Examples Example where there are new groups Barber [Page 55] INTERNET DRAFT July 2000 [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 [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] . 11.5 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. 11.5.1 Responses 230 list of new articles by message-id follows Barber [Page 56] INTERNET DRAFT July 2000 11.5.2 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] [S] 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 Barber [Page 57] INTERNET DRAFT July 2000 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. Associated with each such extension is a corresponding NNTP keyword value. Each service extension registered with the IANA MUST be defined in an RFC. Such RFCs either must be on the standards-track or must define an IESG-approved experimental protocol. The definition must include: . the textual name of the NNTP service extension . the label that is returned by LIST EXTENSIONS that would indicate to the client that the server supports this particular extension . any new NNTP keywords associated with the extension . the syntax and possible values of parameters associated with the new NNTP keywords . any new parameters the extension associates with any other pre-existing NNTP keywords . how support for the extension affects the behavior of a server and client NNTP . any increase in the maximum length of commands over the value specified in this memo In addition, any NNTP keyword value that starts with an upper or lower case "X" refers to a local NNTP service extension, which is used through bilateral, rather than standardized, agreement. Keywords beginning with "X" MUST NOT be used in a registered service extension. 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. Additional keywords are bound by the same rules as NNTP keywords; specifically, keywords beginning with "X" are local extensions that MUST NOT be registered or standardized and keywords not beginning with "X" must always be registered. 12.1 Initial IANA Registry The IANA's initial registry of NNTP service extensions consists of these entries: Barber [Page 58] INTERNET DRAFT July 2000 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[9] 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 augument = parameter ; excluding sequence ".." body-command = "BODY" [1*WSP (msg-id / article-number)] *WSP CRLF command = article-command / body-command / debug-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 / over-command / pat-command / post-command / quit-command / stat-command CR = %x0D Barber [Page 59] INTERNET DRAFT July 2000 CRLF = CR LF date-command = "DATE" *WSP CRLF date = 6*8DIGIT DIGIT = %x30-39 debug-command = "DEBUG" 1*WSP ("ON"/"OFF"/"ACK") *WSP CRLF 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 = 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 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 Barber [Page 60] INTERNET DRAFT July 2000 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. 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 mis-association 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. Barber [Page 61] INTERNET DRAFT July 2000 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 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. Barber [Page 62] INTERNET DRAFT July 2000 [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] Horton, M.R. and R. Adams, "Standard for interchange of USENET messages", RFC-1036, AT&T Bell Laboratories and Center for Seismic Studies, December, 1987. [7] Robertson, Rob, "FAQ: Overview database / NOV General Information", ftp://ftp.uu.net/networking/news/nntp/inn/faq- nov.Z, January, 1995. [8] Mills, David L., "Network Time Protocol (Version 3), Specification, Implementation and Analysis", RFC-1305, University of Delaware, March 1992. [9] 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. 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. Barber [Page 63] INTERNET DRAFT July 2000 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: . Wayne Davison . Clive D.W. Feather . Chris Lewis . Tom Limoncelli . Eric Schnoebelen . Rich Salz This work was motivated by the work of various newsreader authors and newsserver authors, which includes those listed below: . Rick Adams -- Original author of the NNTP extensions to the RN newsreader and last maintainer of Bnews . Stan Barber -- Original author of the NNTP extensions to the newsreaders that are part of Bnews. . Geoff Collyer -- Original author of the OVERVIEW database proposal and one of the original authors of CNEWS . Dan Curry -- Original author of the xvnews newsreader . Wayne Davision -- Author of the first threading extensions to the RN newsreader (commonly called TRN). . Geoff Huston -- Original author of ANU NEWS . Phil Lapsey -- Original author of the UNIX reference implementation . Ian Lea -- Maintainer of the TIN newsreader . Chris Lewis -- First known implementor of the AUTHINFO GENERIC extension . Rich Salz -- Original author of INN . Henry Spencer -- One of the original authors of CNEWS . Kim Storm -- Original author of the NN newsreader 18. Author's Address Stan Barber P.O. Box 300481 Houston, Texas 77230 Email: Barber [Page 64] INTERNET DRAFT July 2000 This document expires January 15, 2001. Barber [Page 65]