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This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.
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This Internet-Draft will expire on August 6, 2004.
Copyright (C) The Internet Society (2004). All Rights Reserved.
This document defines extensions to the FTP specification STD9, RFC959, "FILE TRANSFER PROTOCOL (FTP)". These extensions provide the ability for a FTP Client to modify the last modification time, the creation time, or multiple facts (last modification time, creation time, operating system permissions, etc.) of a file in the server-FTP process NVFS. These extensions are implemented by three new optional commands: "MFMT" (Modify File Modification Time), "MFCT" (Modify File Creation Time), and "MFF" (Modify File Facts).
Comments should be directed to David Somers (dsomers@trevezel.com).
1.
Introduction
2.
Document Conventions
2.1
Basic Tokens
2.2
Pathnames
2.3
Times
2.4
Server Replies
2.5
Interpreting Examples
3.
Modify File Modification Time (MFMT)
3.1
Syntax
3.2
Error responses
3.3
FEAT response for MFMT
3.3.1
Example FEAT response
3.4
MFMT Examples
4.
Modify File Creation Time (MFCT)
4.1
Syntax
4.2
Error responses
4.3
FEAT response for MFCT
4.3.1
Example FEAT response
4.4
MFCT Examples
5.
Modify File Facts (MFF)
5.1
Syntax
5.1.1
Create fact
5.1.2
Modify fact
5.2
Operating System specific facts
5.2.1
Example Operating System specific facts
5.3
Local/Experimental "X." facts
5.4
Error responses
5.5
FEAT response for MFF
5.5.1
Example FEAT responses
5.6
MFF Examples
6.
IANA Considerations
6.1
The OS Specific fact registry
7.
Security Considerations
§
Normative References
§
Author's Address
A.
Acknowledgements
§
Intellectual Property and Copyright Statements
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The File Transfer Protocol (FTP) currently defined in STD 9, RFC 959 [1], and in place on the Internet allows files to be transferred between a server-FTP and a user-FTP, and vice versa. When a file is transferred from the user-FTP to the server-FTP, the creation time, last modification time, and operating system facts (for example, file permissions) can not be specified. The NVFS typically sets these to default values.
This document defines extensions to the File Transfer Protocol, specifically three new optional commands "MFMT", "MFCT", and "MFF" which allow the last modification time, creation time, or a list of facts to be modified for an object in the NVFS.
The MFF command is complimentary to the MLSx commands as detailed in [5]. The MLSx commands are used to standardize retrieving the file and directory information returned by the Server-FTP process; the MFF command aims to standardize modifying the facts for the file and directory objects in the NVFS.
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This document makes use of the conventions in [2]. That provides the interpretation of capitalized imperative words like MUST, SHOULD, etc.
This document also uses notation defined in [1]. In particular, the terms "reply", "user", "NVFS", "file", "pathname", "FTP commands", "DTP", "user-FTP process", "user-PI", "user-DTP", "server-FTP process", "server-PI", "server-DTP", "mode", "type", "NVT", "control connection", "data connection", and "ASCII", are all used here as defined there.
Syntax required is defined using the Augmented BNF defined in [3]. Some general ABNF definitions are required throughout the document, those will be defined later in this section. At first reading, it may be wise to simply recall that these definitions exist here, and skip to the next section.
This document defines basic tokens as specified in section 2.1 of [5].
This document defines pathnames as specified in section 2.2 of [5].
This document defines times as specified in section 2.3 of [5].
This document defines server replies as specified in section 2.4 of [5].
This document defines server replies as specified in section 2.5 of [5].
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The FTP command, MODIFY FILE MODIFICATION TIME (MFMT), is used to modify the last modification time of a file.
It should be noted that similar functionality has been implemented by some server-PIs as the command MDTM. However, the use of MDTM to modify the last modification time of a file conflicts with the use of the MDTM command to retrieve the last modification time of a file as defined in [5]. It is proposed that the MFMT command be used instead of abusing MDTM for such purposes.
The syntax of the MFMT command is:
mfmt = "MFMT" SP time-val SP pathname CRLF
As with all FTP commands, the "MFMT" command label is interpreted in a case insensitive manner.
The "time-val" specifies the last modification time to be applied to the file.
The "pathname" specifies an object in the NVFS.
The server-PI will respond to the MFMT command with a 213 reply, or an error response if the object does not exist, the last modification time could not be modified, or some other error has occurred.
mfmt-response = "213" SP "Modify=" time-val ";" SP pathname CRLF /
error-response
The "time-val" in the response MUST be the modified last modification time of the file. This value MAY not be the same as that requested due to constraints of the NVFS to store the last modification time (for example, it may only have sufficient resolution to store the last modification time to the nearest minute instead of to the thousandths of a second that "time-val" MAY be specified to).
Where the command is correctly parsed, but the pathname identifies no existing entity, then a 550 reply SHOULD be sent. Where the command can not be correctly parsed, a 500 or 501 reply SHOULD be sent. Various 4xy replies are also possible in appropriate circumstances.
Where a server-FTP process supports MFMT, as specified here, it MUST include the response to the FEAT command [4]:
mfmt-feat = SP "MFMT" CRLF
The initial space shown in the mfmt-feat response is that required by the FEAT command.
This string "MFMT" is not case sensitive, but SHOULD be transmitted in upper case. Where MFMT is not supported, the MFMT line MUST NOT be included in the FEAT response.
C> feat S> 211- <any descriptive text> S> ... S> MFMT S> ... S> 211 end
The ellipses indicate place holders where other features may be included, and are not required. The one space indentation of the feature lines is mandatory [4].
To modify the last modification time of a file called "Fred.txt" to July 17, 2002 21:07:15,
C> MFMT 20020717210715 Fred.txt S> 213 Modify=20020717210715; Fred.txt
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The FTP command, MODIFY FILE CREATION TIME (MFCT), is used to modify the last modification time of a file.
Implementers of this command on UNIX(TM) systems should note that the unix "stat" "st_ctime" field does not give creation time, and that unix file systems do not record creation time at all. Unix (and POSIX) implementations will normally not support this command.
The syntax of the MFCT command is:
mfct = "MFCT" SP time-val SP pathname CRLF
As with all FTP commands, the "MFCT" command label is interpreted in a case insensitive manner.
The "time-val" specifies the creation time to be applied to the file.
The "pathname" specifies an object in the NVFS.
The server-PI will respond to the MFCT command with a 213 reply, or an error response if the object does not exist, the creation time could not be modified, or some other error has occurred.
mfct-response = "213" SP "Create=" time-val ";" SP pathname CRLF /
error-response
The "time-val" in the response MUST be the modified creation time of the file. This value MAY not be the same as that requested due to constraints of the NVFS to store the creation time (for example, it may only have sufficient resolution to store the creation time to the nearest minute instead of to the thousandths of a second that "time-val" MAY be specified to).
Where the command is correctly parsed, but the pathname identifies no existing entity, then a 550 reply SHOULD be sent. Where the command can not be correctly parsed, a 500 or 501 reply SHOULD be sent. Various 4xy replies are also possible in appropriate circumstances.
Where a server-FTP process supports MFCT, as specified here, it MUST include the response to the FEAT command [4]:
mfct-feat = SP "MFCT" CRLF
The initial space shown in the mfct-feat response is that required by the FEAT command.
This string "MFCT" is not case sensitive, but SHOULD be transmitted in upper case. Where MFCT is not supported, the MFCT line MUST NOT be included in the FEAT response.
C> feat S> 211- <any descriptive text> S> ... S> MFCT S> ... S> 211 end
The ellipses indicate place holders where other features may be included, and are not required. The one space indentation of the feature lines is mandatory [4].
To modify the creation time of a file called "Jim.txt" in the current directory to July 17, 2002 21:22:30,
C> MFCT 20020717212230 Jim.txt S> 213 Create=20020717212230; Jim.txt
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The FTP command, MODIFY FILE FACTS (MFF), is used to modify one or more facts of a file. These facts are attributes such as creation time, last modification time, or operating system specific attributes such as file permissions.
This command is complimentary to the MLSx commands as detailed in [5]. The MLSx commands are used to standardize retrieving the file and directory information returned by the Server-FTP process; the MFF command aims to standardize modifying the facts for the file and directory objects in the NVFS.
When only modifying the creation time or the modification time of a file, it is RECOMMENDED that the MFCT or MFMT commands be used instead.
The syntax of the MFF command is:
mff = "MFF" [ mff-facts ] SP pathname CRLF mff-facts = 1*( mff-fact ";" ) mff-fact = mff-standardfact / mff-osfact / mff-localfact mff-standardfact = mff-createtimefact / mff-modifytimefact mff-createtimefact = "Create" "=" time-val mff-modifytimefact = "Modify" "=" time-val mff-osfact = <IANA assigned OS name> "." token "=" *SCHAR mff-localfact = "X." token "=" *SCHAR
As with all FTP commands, the "MFF" command label is interpreted in a case insensitive manner.
The "mff-facts" are a series of facts as keyword=value pairs each followed by a semi-colon (";") character. Fact keyword names are case-insensitive.
The "pathname" specifies an object in the NVFS.
The server-PI will respond to the MFF command with a 213 reply containing a list of the facts that MUST detail the new values for all the facts specified in the request, or an error response.
mff-response = "213" SP 1*( mff-fact ";") SP pathname CRLF /
error-response
The order of the "mff-fact" keyword=value pairs returned in the response MAY be in any order.
The "time-val" in the response MAY not be the same as that requested due to constraints of the NVFS to store such times (for example, it may only have sufficient resolution to store the last modification time to the nearest minute instead of to the thousandths of a second that "time-val" MAY be specified to).
The error response MUST be returned if any of the following conditions happen:
The object does not exist.
A fact could not be modified, for example due to insufficient access control permissions.
An unknown fact was specified.
When an error response is returned, the client-PI MUST make no assumptions about which, if any, facts have been modified. The client-PI can issue an MLST (if the server-PI supports MLST) to determine what attributes have been modified.
The Create fact is used to modify the creation time of the object specified by "pathname".
Implementers of this fact on UNIX(TM) systems should note that the unix "stat" "st_ctime" field does not give creation time, and that unix file systems do not record creation time at all. Unix (and POSIX) implementations will normally not support this fact.
The Modify fact is used to modify the last modification time of the object specified by "pathname".
Facts that are specific to an operating system, or file system, SHOULD be specified by keywords that are prefixed by an IANA operating system name (ftp://ftp.iana.org/assignments/operating-system-names).
Implementation Note: It is envisioned that the operating system specific facts will be identical to those used by the MLSx command as detailed in [5]; implementers can then use the same logic to process facts whether for MLSx or MFF.
The specification of Operating Systems specific facts is explicitly outside the scope of this document. Such specifications SHOULD be documented elsewhere (that is, in an internet draft, RFC, etc.)
The following examples are only indicative of how it is anticipated that some Operating System specific facts could be implemented.
UNIX.mode -- Unix file mode (expressed in octal)
WINDOWS-NT.SIS.Author -- Windows NT,
Summary Information Stream, Author property
Implementations may define keywords for experimental, or private, use. All such keywords MUST begin with the two character sequence "X.". As type names are case-insensitive, "X." and "x." are equivalent.
Where the command is correctly parsed, but the pathname identifies no existing entity, then a 550 reply SHOULD be sent. Where the command can not be correctly parsed, a 500 or 501 reply SHOULD be sent. If an unknown fact is provided, a 504 reply SHOULD be sent. Various 4xy replies are also possible in appropriate circumstances.
Where a server-FTP process supports MFF, as specified here, it MUST include in the response to the FEAT command [4], a feature line containing the string "MFF". This string is not case sensitive, but SHOULD be transmitted in upper case. As well as indicating MFF support, the MFF feature line indicates which MFF facts are available for modification by the server-FTP process. Where MFF is not supported, the MFF line MUST NOT be included in the FEAT response.
mff-feat = SP "MFF" SP factlist CRLF factlist = 1*( factname ";" )
The initial space shown in the mff-feat response is that required by the FEAT command.
C> feat S> 211- <any descriptive text> S> ... S> MFF Modify; S> ... S> 211 end
This server-FTP process indicates that it supports MFF, and only supports modification of the last modification time of an object in the NVFS.
C> feat S> 211- <any descriptive text> S> ... S> MFF Create;Modify;WINDOWS-NT.SIS.Author; S> ... S> 211 end
This server-FTP process indicates that it supports MFF, and supports modification of the creation time, last modification time, and an operating system specific fact called "WINDOWS-NT.SIS.Author" of an object in the NVFS.
The ellipses indicate place holders where other features may be included, and are not required. The one space indentation of the feature lines is mandatory [4].
To modify the creation time of a file called "Sheila.txt" to July 17, 2002 21:22:30,
C> MFF Create=20020717212230; Sheila.txt S> 213 Create=20020717212230; Sheila.txt
Note that the above could also be achieved using the MFCT command, thus:
C> MFCT 20020717212230 Sheila.txt S> 213 Create=20020717212230; Sheila.txt
To modify the permissions on a Unix-based NVFS for the file called "Bob.txt" to (octal) 777,
C> MFF UNIX.mode=777; Bob.txt S> 213 UNIX.mode=777; Bob.txt
To modify the permissions on a Unix-based NVFS for the file called "Fred.txt" to (octal) 777, and the creation time to July 18, 2002 01:28:45,
C> MFF UNIX.mode=777;Create=20020718012845; Fred.txt S> 213 Create=20020718012845;UNIX.mode=777; Fred.txt
If the same request was made to a server-FTP process that does not support the UNIX.mode fact,
C> MFF UNIX.mode=777;Create=20020718012845; Fred.txt S> 504 Parameter Not Implemented (UNIX.mode)
The creation date may or may not have been modified by the server-PI before the server-PI determined that the UNIX.mode fact was not implemented.
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This specification makes use of some lists of values currently maintained by the IANA. It does not add any values to any existing registries.
The MFF command reuses the OS Specific fact registry that is used by the MLSx commands as detailed in [5]
The OS names for the OS portion of the fact name must be taken from the IANA's list of registered OS names. To add a fact name to this OS specific registry of OS specific facts, an applicant must send to the IANA a request, in which is specified the OS name, the OS specific fact name, a definition of the syntax of the fact value, which must conform to the syntax of a token as given in this document, and a specification of the semantics to be associated with the particular fact and its values. Upon receipt of such an application, and if the combination of OS name and OS specific fact name has not been previously defined, the IANA will add the specification to the registry.
Any examples of OS specific facts found in this document are to be treated as examples of possible OS specific facts, and do not form a part of the IANA's registry merely because of being included in this document.
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No significant security issues, not already present in the FTP protocol, are believed to have been created by this extension.
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| [1] | Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9, RFC 959, October 1985. |
| [2] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 (TXT, HTML, XML). |
| [3] | Crocker, D., "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. |
| [4] | Hethmon, P., "Feature negotiation mechanism for the File Transfer Protocol", RFC 2389, August 1998 (TXT, HTML, XML). |
| [5] | Elz, R. and P. Hethmon, "Extensions to FTP", draft-ietf-ftpext-mlst-16 (work in progress), September 2002. |
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| David M. P. Somers | |
| Trevezel Systems GmbH | |
| Postfach 3483 | |
| Trier D-54224 | |
| GERMANY | |
| EMail: | dsomers@trevezel.com |
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Thank you to the authors and editors of [5] for the facts in their MLSx command which have been hijaaked (in the nicest possible way) by the MFF command herein.
A big thanks for xml2rfc which greatly helped in the production of this document.
And finally, thanks to all those who have commented on earlier drafts of this document.
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