Network Working Group J. Galbraith INTERNET-DRAFT Van Dyke Technologies, Inc. draft-ietf-secsh-publickeyfile-00 R. Thayer Expires June 2001 The Tillerman Group January 2000 SECSH Public Key File Format STATUS OF THIS MEMO: This document is an Internet-Draft and is in full conformance with all provisions of 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 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. Abstract This document formally documents the existing public key file format in use for exchanging public keys between different SECSH implementations. 1. Conventions used in this document 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]. 2. Introduction In order to use public key authentication, public keys must be exchanged between client and server. This document formally describes the existing public key file format, with few exceptions. Where this document departs from current practice, it also suggests a mechanism for backwards compatability. J. Galbraith, R. Thayer [Page 1]
SECSH Public Key File Format January 2000 3. Key File Format SECSH implementations must share public key files between the client and the server in order interoperate. A key file consists of a sequence of lines, each of which MUST be terminated with a <CR><LF> and MUST NOT exceed 72 bytes in length (excluding the <CR><LF> line terminator.) Because current practice is to terminate lines with <LF> only, implementations SHOULD be able to read files with lines terminated only by a <LF> for backwards compatibility reasons. 4. Begin and end markers The first line of a conforming key file MUST be a begin marker, which is the literal text: ---- BEGIN SSH2 PUBLIC KEY ---- The last line of a conforming key file MUST be a end marker, which is the literal text: ---- END SSH2 PUBLIC KEY ---- 5. Key File Header The key file header section consists of multiple RFC822 - style header fields. Each field is a line of the following format: Header-tag ':' ' ' Header-value The Header-tag MUST NOT be more than 64 bytes. The Header-value MUST NOT be more than 1024 bytes. Each line in the header MUST be less the 72 bytes. A line is continued if the last character in the line is a '\'. If the last character of a line is a '\', then the logical contents of the line is formed by removing the '\' and appending the contents of the next line. Header-tag MUST be US-ASCII. Header-value MUST be encoded in UTF-8 ([RFC-2044]). A line that is not a continuation line that has no ':' in it is assumed to be the first line of the base 64 encoded body (Section 8) Compliant implementations MUST ignore unrecognized header fields. Implementations SHOULD preserve unrecognized header fields when manipulating the key file. Existing implementations may not correctly handle unrecognized J. Galbraith, R. Thayer [Page 2]
SECSH Public Key File Format January 2000 fields. During a transition period, implementations SHOULD generate key file headers that contain only a subject field followed by a comment field. 6. Subject Header This field currently is used to store the login-name that the key was generated under. For example: Subject: user 7. Comment Header Contain a user specified comment which will be displayed when using the key. It is suggested that this field default to user@hostname for the user and machine used to generate the key. For example: Comment: user@mycompany.com 8. Public Key File Body The body of a public key file consists of the public key blob as described in [SSH-TRANS], section 4.6, "Public Key Algorithms", encoded in base 64 as specified in [RFC-2045] section 6.8, "Base64 Content-Transfer-Encoding". As with all other lines, each line in the body MUST be no longer than 72 characters and terminated with a <CR><LF> character. 9. References [SSH-TRANS] Ylonen, T., et al: "SSH Transport Layer Protocol", Internet Draft, draft-secsh-transport-09.txt [RFC-2044] Yergeau, F: "UTF-8, a Transformation Format of Unicode and ISO 10646", October 1996. [RFC-2026] S. Bradner: "The Internet Standards Process -- Revision 3", October 1996. [RFC-2119] S. Bradner: "Key words for use in RFCs to Indicate Requirement Levels", March 1997. [RFC-2045] Freed & Borenstein: "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", November 1996. J. Galbraith, R. Thayer [Page 3]
SECSH Public Key File Format January 2000 10. Author's Address Joseph Galbraith Van Dyke Technologies, Inc. 4848 Tramway Ridge Rd. Suite 101 Albuquerque, NM 87111 Email: galb@vandyke.com Phone: +1 505 332 5700 Rodney Thayer The Tillerman Group 370 Altair Way, PMB 321 Sunnyvale, CA 94086 Email: rodney@tillerman.to Phone: +1 408 757 9693 J. Galbraith, R. Thayer [Page 4]
