Network Working Group J. Klensin Internet-Draft Updates: 959 (if approved) A. Hoenes Intended status: Standards Track TR-Sys Expires: June 20, 2010 December 17, 2009 FTP Command and Extension Registry draft-klensin-ftp-registry-04 Abstract Every version of the FTP specification has added a few new commands, with the early ones summarized in RFC 959. RFC 2389 established a mechanism for specifying and negotiating FTP extensions. The number of extensions, both supported by the mechanism and some that are not, continues to increase. An IANA registry of FTP Command and Feature names is established to reduce the likelihood of conflict of names and the consequent ambiguity. This specification establishes that registry. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at 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 Internet-Draft will expire on June 20, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. Klensin & Hoenes Expires June 20, 2010 [Page 1] Internet-Draft FTP Command and Extension Registry December 2009 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Discussion List . . . . . . . . . . . . . . . . . . . . . 3 2. Registry Definition . . . . . . . . . . . . . . . . . . . . . 3 2.1. Registry Name . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Registry Format . . . . . . . . . . . . . . . . . . . . . 3 2.3. Criteria for Registration . . . . . . . . . . . . . . . . 5 2.4. Base FTP Commands . . . . . . . . . . . . . . . . . . . . 6 2.5. Obsolete Commands . . . . . . . . . . . . . . . . . . . . 6 3. Initial Contents of Registry . . . . . . . . . . . . . . . . . 7 4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7.1. Normative References . . . . . . . . . . . . . . . . . . . 10 7.2. Informative References . . . . . . . . . . . . . . . . . . 11 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 11 A.1. Changes in Version -01 . . . . . . . . . . . . . . . . . . 11 A.2. Changes in Version -02 . . . . . . . . . . . . . . . . . . 11 A.3. Changes in Version -03 . . . . . . . . . . . . . . . . . . 12 A.4. Changes in Version -04 . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Klensin & Hoenes Expires June 20, 2010 [Page 2] Internet-Draft FTP Command and Extension Registry December 2009 1. Introduction Every version of the FTP specification has added a few new commands, with the early ones summarized in RFC 959 [RFC0959]. RFC 2389 [RFC2389] established a mechanism for specifying and negotiating extensions to the FTP protocol specified in RFC 959, by means of "FEAT Strings" identifying extensions supported by the FTP server, and sent in response to a "FEAT" command. The number of extensions continues to grow, not all of them supported by FEAT. An IANA registry is established to reduce the likelihood of conflict of names and the consequent ambiguity and to encourage the sharing of information. This specification establishes that registry. 1.1. Discussion List [[ RFC Editor: please remove this section before publication. ]] Until and unless a WG is created, this proposal will be discussed on the list apps-discuss@ietf.org 2. Registry Definition 2.1. Registry Name The recommended name of this registry is "FTP Commands and Extensions". 2.2. Registry Format IANA is requested to establish a registry for FTP commands and extensions. Registration requests and registry entries should include the following: Command Name - The FTP command, either new or modified, used in the extension or with which the extension is used. Following the long-standing practice to capitalize command names in specification documents for FTP, the command names are entered in all uppercase. For extensions amending the operation of a command, a plus sign ("+") is appended to the command name. However, an extension might not be bound to one command (or a small number of commands), but affect the overall command parameter handling and/or transaction processing; in this case, the string "-N/A-" is entered. It is intended to have the registry entries ordered by ascending ASCII collation order of this column (including the "+" suffix if Klensin & Hoenes Expires June 20, 2010 [Page 3] Internet-Draft FTP Command and Extension Registry December 2009 present). Extension name - The name of the extension. FTP extensions predating RFC 2389 [RFC2389], and some extensions published after it, did not specify a keyword to identify the extension in a FEAT response. Some later specifications established FEAT strings with the respective command names as their keywords. In order to provide for keywords for future specifications in such cases, this document establishes 'placeholder' keywords to reserve reasonable feature names for future standardization. Similarly, placeholder keywords are used for the basic FTP commands specified in RFC 959 [RFC0959] and those of its predecessors that are still in use. These placeholder keywords are placed in the registry for convenience; it is not intended that they be returned in FEAT responses. To compensate for this idiosyncrasy, the column in the registry is entitled "FEAT Code", and to clearly distinguish between the two cases, defined FEAT keywords codes are listed in all uppercase, whereas 'placeholder' keywords (henceforth called "pseudo FEAT codes") are listed in lowercase. Future specifications are allowed to "upgrade" a placeholder to a true keyword unless it is specifically declared 'immutable' below, but otherwise IANA maintains uniqueness of feature names (FEAT codes) based on case- insensitive comparison. Description - A brief description of the extension and, where appropriate, the command. FEAT String - (optional in registration requests to the IANA) The string expected to be included in the response to the FEAT command [RFC2389] if the extension is supported. In many cases, the FEAT string required to identify an extension only consists of the "FEAT Code", making this item redundant. Therefore, this item should only be specified if it is intended to register a FEAT string that contains mandatory elements other than the "FEAT Code" itself. Due to space restrictions, and to allow registrants to provide additional information as well, IANA should present these registration items (if given) in numbered footnotes to the table, not in an additional table column. Klensin & Hoenes Expires June 20, 2010 [Page 4] Internet-Draft FTP Command and Extension Registry December 2009 Command Type - The type (or 'kind') of the command. Section 4.1 of RFC 959 [RFC0959] introduced a subdivision of FTP commands into three types: Access control, transfer Parameter {setting}, and Service {execution}. For clarity and as a service to the user of the registry, this subdivision is extended to all registered FTP commands, using the characteristic initial of the type, 'a', 'p', or 's', respectively, filed in the registry column entitled "type"; combinations are allowed, e.g. 'p/s'. Conformance Requirements - The support expectation for the command. RFC 959 specifies mandatory-to-implement commands and optional commands. This classification is carried over to all registered commands, using a column entitled "conf" carrying a single character -- either 'm' or 'o', for "mandatory" and "optional", respectively. Similarly, obsoleted or historic entries are left in the registry to avoid conflicts with deployed implementations, and these entries are marked with 'h' (for "historic"). Beyond the initial registrations, Standards Action [RFC5226] is needed to register new "mandatory" entries or to move such entries to "historic". Reference - A reference to an RFC or other definition of the extension and/or to implementations supporting it (see the next section). 2.3. Criteria for Registration This registry is primarily intended to avoid conflicting uses of the same extension names and command keywords for different purposes, not to demonstrate that an extension is somehow "approved". The "expert review" method will be used, but the designated expert is expected to check only that at least one of the two criteria that follow are met. 1. The extension is documented in a permanent and readily available public specification (This is the same as the "Specification Required" registration policy defined in RFC 5226 [RFC5226]. 2. The extension is actually implemented in FTP client and server systems that are generally available (not necessarily either free or unencumbered, but available). For an extension or command to be marked "mandatory" ('m' in the "conf" column), an IETF Standards Track Specification is required. An IESG Standards Action is allowed to direct IANA to change the Conformance Requirements listed for any entry. Klensin & Hoenes Expires June 20, 2010 [Page 5] Internet-Draft FTP Command and Extension Registry December 2009 2.4. Base FTP Commands The following commands are part of the base FTP specification [RFC0959] and are listed in the registry with the immutable pseudo FEAT code "base". Mandatory commands: ABOR, ACCT, ALLO, APPE, CWD, DELE, HELP, LIST, MODE, NLST, NOOP, PASS, PASV, PORT, QUIT, REIN, REST, RETR, RNFR, RNTO, SITE, STAT, STOR, STRU, TYPE, USER Optional commands: CDUP, MKD, PWD, RMD, SMNT, STOU, SYST Note: STD 3 [RFC1123] clarified and updated the status and implementation requirements of these standard FTP commands, and it contains important complementary information for the following commands: LIST, NLST, PASV, REST, SITE, STOU 2.5. Obsolete Commands The following commands were specified as experimental in an extension to an early version of the FTP specification [RFC0775] but later deprecated by RFC 1123 [RFC1123], because Standard FTP [RFC0959] specifies their standard successors. They are listed in the registry with the immutable pseudo FEAT code "hist". XCUP, XCWD, XMKD, XPWD, XRMD Implementation note: Deployed FTP clients still make use of the deprecated commands and most FTP servers support them as aliases for the standard commands. The following commands were specified as part of the "FOOBAR" IPng effort in RFC 1545 [RFC1545] and, later, RFC 1639 [RFC1639] and are now obsolete. They are listed in the registry with the immutable pseudo FEAT code "hist". LPRT, LPSV Klensin & Hoenes Expires June 20, 2010 [Page 6] Internet-Draft FTP Command and Extension Registry December 2009 3. Initial Contents of Registry As a service to users of the registry and the authors of existing specifications, all FTP commands and features published in RFCs after STD 3 [RFC1123] and up to the time of this writing are to be included into the registry upon creation. The following pseudo FEAT codes have been assigned, according to Section 2: base - FTP standard commands [RFC0959] hist - Historic experimental commands [RFC0775], [RFC1639] secu - FTP Security Extensions [RFC2228] feat - FTP Feature Negotiation [RFC2389] nat6 - FTP Extensions for NAT/IPv6 [RFC2428] +-------+------+-------------------+------+------+------------------+ | cmd | FEAT | description | type | conf | RFC#s/References | | | Code | | | | and Notes | +-------+------+-------------------+------+------+------------------+ | ABOR | base | Abort | s | m | 959 | | ACCT | base | Account | a | m | 959 | | ADAT | secu | Authentication/ | a | o | 2228, 2773, 4217 | | | | Security Data | | | | | ALLO | base | Allocate | s | m | 959 | | APPE | base | Append (with | s | m | 959 | | | | create) | | | | | AUTH | secu | Authentication/ | a | o | 2228 | | | | Security | | | | | | | Mechanism | | | | | AUTH+ | AUTH | Authentication/ | a | o | 2773, 4217 #2 | | | | Security | | | | | | | Mechanism | | | | | CCC | secu | Clear Command | a | o | 2228 | | | | Channel | | | | | CDUP | base | Change to Parent | a | o | 959 | | | | Directory | | | | | CONF | secu | Confidentiality | a | o | 2228 | | | | Protected Command | | | | | CWD | base | Change Working | a | m | 959 | | | | Directory | | | | | DELE | base | Delete File | s | m | 959 | | ENC | secu | Privacy Protected | a | o | 2228, 2773, 4217 | | | | Command | | | | | EPRT | nat6 | Extended Port | p | o | 2428 | | EPSV | nat6 | Extended Passive | p | o | 2428 | | | | Mode | | | | Klensin & Hoenes Expires June 20, 2010 [Page 7] Internet-Draft FTP Command and Extension Registry December 2009 | FEAT | feat | Feature | a | m #1 | 2389 | | | | Negotiation | | | | | HELP | base | Help | s | m | 959 | | LANG | UTF8 | Language (for | p | o | 2640 | | | | Server Messages) | | | | | LIST | base | List | s | m | 959, 1123 | | LPRT | hist | Data Port | p | h | 1545, 1639 | | | | {FOOBAR} | | | | | LPSV | hist | Passive Mode | p | h | 1545, 1639 | | | | {FOOBAR} | | | | | MDTM | MDTM | File Modification | s | o | 3659 | | | | Time | | | | | MIC | secu | Integrity | a | o | 2228, 2773, 4217 | | | | Protected Command | | | | | MKD | base | Make Directory | s | o | 959 | | MLSD | MLST | List Directory | s | o | 3659 | | | | (for machine) | | | | | MLST | MLST | List Single | s | o | 3659 | | | | Object | | | | | MODE | base | Transfer Mode | p | m | 959 | | NLST | base | Name List | s | m | 959, 1123 | | NOOP | base | No-Op | s | m | 959 | | OPTS | feat | Options | p | m #1 | 2389 | | PASS | base | Password | a | m | 959 | | PASV | base | Passive Mode | p | m | 959, 1123 | | PBSZ | secu | Protection Buffer | p | o | 2228 | | | | Size | | | | | PBSZ+ | PBSZ | Protection Buffer | p | o | 4217 | | | | Size | | | | | PORT | base | Data Port | p | m | 959 | | PROT | secu | Data Channel | p | o | 2228 | | | | Protection Level | | | | | PROT+ | PROT | Data Channel | p | o | 4217 | | | | Protection Level | | | | | PWD | base | Print Directory | s | o | 959 | | QUIT | base | Logout | a | m | 959 | | REIN | base | Reinitialize | a | m | 959 | | REST | base | Restart | s/p | m | 959, 1123 | | REST+ | REST | Restart (for | s/p | m | 3659 #3 | | | | STREAM mode) | | | | | RETR | base | Retrieve | s | m | 959 | | RMD | base | Remove Directory | s | o | 959 | | RNFR | base | Rename From | s/p | m | 959 | | RNTO | base | Rename From | s | m | 959 | | SITE | base | Site Parameters | s | m | 959, 1123 | | SIZE | SIZE | File Size | s | o | 3659 | | SMNT | base | Structure Mount | a | o | 959 | | STAT | base | Status | s | m | 959 | Klensin & Hoenes Expires June 20, 2010 [Page 8] Internet-Draft FTP Command and Extension Registry December 2009 | STOR | base | Store | s | m | 959 | | STOU | base | Store Unique | a | o | 959, 1123 | | STRU | base | File Structure | p | m | 959 | | SYST | base | System | s | o | 959 | | TYPE | base | Representation | p | m | 959 #4 | | | | Type | | | | | USER | base | User Name | a | m | 959 | | XCUP | hist | {precursor for | s | h | 775, 1123 | | | | CDUP} | | | | | XCWD | hist | {precursor for | s | h | 775, 1123 | | | | CWD} | | | | | XMKD | hist | {precursor for | s | h | 775, 1123 | | | | MKD} | | | | | XPWD | hist | {precursor for | s | h | 775, 1123 | | | | PWD} | | | | | XRMD | hist | {precursor for | s | h | 775, 1123 | | | | RMD} | | | | | -N/A- | TVFS | Trivial Virtual | p | o | 3659 | | | | File Store | | | | +-------+------+-------------------+------+------+------------------+ Table 1 Notes: #1 While an IETF Standards Action would be required to make the FEAT mechanism [RFC2389] mandatory, implementation of that extension mechanism is clearly required in conjunction with any extension or feature that depends on it. #2 FEAT String for RFC 4217: AUTH TLS FEAT String for RFC 2773: AUTH KEA-SKIPJACK #3 FEAT String: REST STREAM #4 FEAT String: TYPE {semicolon-separated list of supported types} 4. Acknowledgments Any work to update or extend FTP depends on the base specification in RFC 959. The contributions of its editors, Jon Postel and Joyce Reynolds, are gratefully acknowledged. The option negotiation mechanism specified in RFC 2389 and the accumulation of features that has followed it made this registry relevant; the authors of those documents are acknowledged as well. Barry Leiba and Alexey Melnikov made several suggestions about Klensin & Hoenes Expires June 20, 2010 [Page 9] Internet-Draft FTP Command and Extension Registry December 2009 earlier drafts of this document, most of which have been incorporated. Anthony Bryan spotted a few typographical errors. Scott Bradner suggested a clarification to the "expert review" text that has been incorporated. The authors appreciate the comments and support for this work received from FTP implementers and many IETF participants. Comments from the IESG helped to shape this document and registry to improve its utility. 5. IANA Considerations IANA is requested to establish the registry described in Section 2 using the initial content specified in Section 3 and including the body of 2.4 and 2.5 as explanatory text in the preface of the registry. New entries should be added to this registry when extensions to FTP are approved or defined in published RFCs or when extensions that are already in use and well-documented are identified. In other words, the requirement for registration is a slightly relaxed version of "Specification Required" [RFC5226] with Expert Review. See Section 2.3 for specifics and exceptions. 6. Security Considerations The creation of this registry provides improved documentation and protection against interoperability problems. It introduces no new security issues. 7. References 7.1. Normative References [RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9, RFC 959, October 1985. [RFC2389] Hethmon, P. and R. Elz, "Feature negotiation mechanism for the File Transfer Protocol", RFC 2389, August 1998. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, Klensin & Hoenes Expires June 20, 2010 [Page 10] Internet-Draft FTP Command and Extension Registry December 2009 May 2008. 7.2. Informative References [RFC0775] Mankins, D., Franklin, D., and A. Owen, "Directory oriented FTP commands", RFC 775, December 1980. [RFC1123] Braden, R., "Requirements for Internet Hosts - Application and Support", STD 3, RFC 1123, October 1989. [RFC1545] Piscitello, D., "FTP Operation Over Big Address Records (FOOBAR)", RFC 1545, November 1993. [RFC1639] Piscitello, D., "FTP Operation Over Big Address Records (FOOBAR)", RFC 1639, June 1994. [RFC2228] Horowitz, M., "FTP Security Extensions", RFC 2228, October 1997. [RFC2428] Allman, M., Ostermann, S., and C. Metz, "FTP Extensions for IPv6 and NATs", RFC 2428, September 1998. [RFC2773] Housley, R. and P. Yee, "Encryption using KEA and SKIPJACK", RFC 2773, February 2000. [RFC4217] Ford-Hutchinson, P., "Securing FTP with TLS", RFC 4217, October 2005. [RFC4844] Daigle, L. and Internet Architecture Board, "The RFC Series and RFC Editor", RFC 4844, July 2007. Appendix A. Change Log [[ RFC Editor: Please remove this Appendix before publication. ]] A.1. Changes in Version -01 Updated document to reflect new date and IPR statement. A.2. Changes in Version -02 o Several small changes in response to initial AD review. o Changed registry model from "extension" to "command" + "extension". Klensin & Hoenes Expires June 20, 2010 [Page 11] Internet-Draft FTP Command and Extension Registry December 2009 o Corrections from Alfred Hoenes, followed by adding his initial registry list and adding him as co-author. o Added description of the derivation of Table 1 to Section 3. o Swapped columns 2 and 3 in Table 1. o Consolidated "cmd" column content format to tag command amendments and FTP features without a particular command, and renamed space eating column 5 to "conf". o Added missing footnotes to Table 1. o Aligned Section 2 with Table 1, adding much information on column format; removed orphan; specified collation of entries by "cmd". o Introduced Standards Track requirement for commands in the registry to be designated as mandatory in Section 2.3 and Section 2; specified particular IESG change control for the "conf" column in the registry. o Split list in Section 2.4 into Mandatory and Optional, added pointer to RFC 1123. o Mention std. replacements per RFC 959 in Section 2.5. o Numerous editorial fixes. A.3. Changes in Version -03 Version -03 was produced in response to IETF Last Call and subsequent IESG comments: o Removed References section entry for RFC 2119 -- not used. o Added all "base" (RFC 959/ 1123) commands and obsolete commands (RFCs 0775, 1545/1639) to registry after discussion during Last Call and with IESG. Tentatively recast title and several bits of the document to refer to "FTP Commands and Extensions", not just extensions and made related text changes. o Clarified instructions to IANA including the "peer reviewed publication" requirement in Section 2.3. o Adjusted references so that those which support commands in the registry are all informative. Klensin & Hoenes Expires June 20, 2010 [Page 12] Internet-Draft FTP Command and Extension Registry December 2009 o Removed language more appropriate to a proposal than to a finished spec (e.g., a few uses of "it appears useful"). o Clarified the IANA Considerations text about "specification required" to make it consistent with Section 2.3. Specifically, specifications of a quality needed to permit interoperable implementations are not required although they are certainly desirable. o After an extended discussion about the possible role of this document in making some extensions mandatory to implement, returned it to its status as a registry specification only. The former text that made the RFC 2389 and 2428 extensions mandatory has been removed. RFC 2389 (the FEAT mechanism itself) is now identified as mandatory for the extensions that depend on it (with a new Note); RFC 2389 (the nat6 extensions) are now simply optional as far as FTP is concerned as they should probably remain unless the IETF concludes that nat6 is either required or very broadly deployed. o More editorial fixes. A.4. Changes in Version -04 Final editing patches -- probably will not be posted until after IESG signoff. o Correction of small typos spotted after -03 was posted. o Another attempt at reformatting the table for better readability. o Cleanup of comments used in the XML to keep the editors synchronized. These changes do not affect the text (or other) output forms of the document. o Changed the registration criteria (See Section 2.3) at IESG request. Klensin & Hoenes Expires June 20, 2010 [Page 13] Internet-Draft FTP Command and Extension Registry December 2009 Authors' Addresses John C Klensin 1770 Massachusetts Ave, Ste 322 Cambridge, MA 02140 USA Phone: +1 617 245 1457 Email: john+ietf@jck.com Alfred Hoenes TR-Sys Gerlinger Str. 12 Ditzingen D-71254 Germany Email: ah@TR-Sys.de Klensin & Hoenes Expires June 20, 2010 [Page 14]