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Network Working Group                                           S. KilleRequest for Comments: 1779                              ISODE ConsortiumObsoletes:1485                                               March 1995Category: Standards TrackA String Representation of Distinguished NamesStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Abstract   The OSI Directory uses distinguished names as the primary keys to   entries in the directory.  Distinguished Names are encoded in ASN.1.   When a distinguished name is communicated between to users not using   a directory protocol (e.g., in a mail message), there is a need to   have a user-oriented string representation of distinguished name.   This specification defines a string format for representing names,   which is designed to give a clean representation of commonly used   names, whilst being able to represent any distinguished name.Table of Contents1.   Why a notation is needed ...................................22.   A notation for Distinguished Name ..........................22.1    Goals ................................................22.2    Informal definition ..................................22.3    Formal definition ....................................43.   Examples ...................................................64.   Acknowledgements ...........................................75.   References .................................................76.   Security Considerations ....................................87.   Author's Address ...........................................8Kille                                                           [Page 1]

RFC 1779                   DN Representation                  March 19951.  Why a notation is needed   Many OSI Applications make use of Distinguished Names (DN) as defined   in the OSI Directory, commonly known as X.500 [1].  This   specification assumes familiarity with X.500, and the concept of   Distinguished Name.  It is important to have a common format to be   able to unambiguously represent a distinguished name.  This might be   done to represent a directory name on a business card or in an email   message.  There is a need for a format to support human to human   communication, which must be string based (not ASN.1) and user   oriented.  This notation is targeted towards a general user oriented   system, and in particular to represent the names of humans.  Other   syntaxes may be more appropriate for other uses of the directory.   For example, the OSF Syntax may be more appropriate for some system   oriented uses.  (The OSF Syntax uses "/" as a separator, and forms   names in a manner intended to resemble UNIX filenames).2.  A notation for Distinguished Name2.1  Goals   The following goals are laid out:    o  To provide an unambiguous representation of a distinguished name    o  To be an intuitive format for the majority of names    o  To be fully general, and able to represent any distinguished name    o  To be amenable to a number of different layouts to achieve an       attractive representation.    o  To give a clear representation of the contents of the       distinguished name2.2  Informal definition   This notation is designed to be convenient for common forms of name.   Some examples are given.  The author's directory distinguished name   would be written:   CN=Steve Kille,   O=ISODE Consortium, C=GBKille                                                           [Page 2]

RFC 1779                   DN Representation                  March 1995   This may be folded, perhaps to display in multi-column format.  For   example:   CN=Steve Kille,   O=ISODE Consortium,   C=GB   Another name might be:   CN=Christian Huitema, O=INRIA, C=FR   Semicolon (";") may be used as an alternate separator.  The   separators may be mixed, but this usage is discouraged.   CN=Christian Huitema; O=INRIA; C=FR   In running text, this would be written as <CN=Christian Huitema;   O=INRIA; C=FR>.  Another example, shows how different attribute types   are handled:   CN=James Hacker,   L=Basingstoke,   O=Widget Inc,   C=GB   Here is an example of a multi-valued Relative Distinguished Name,   where the namespace is flat within an organisation, and department is   used to disambiguate certain names:   OU=Sales + CN=J. Smith, O=Widget Inc., C=US   The final examples show both methods quoting of a comma in an   Organisation name:   CN=L. Eagle, O="Sue, Grabbit and Runn", C=GB   CN=L. Eagle, O=Sue\, Grabbit and Runn, C=GBKille                                                           [Page 3]

RFC 1779                   DN Representation                  March 19952.3  Formal definition   A formal definition can now be given.  The structure is specified in   a BNF grammar in Figure 1.  This BNF uses the grammar defined inRFC822, with the terminals enclosed in <> [2].  This definition is in an   abstract character set, and so may be written in any character set   supporting the explicitly defined special characters.  The quoting   mechanism is used for the following cases:    o  Strings containing ",", "+", "=" or """ , <CR>, "<",       ">", "#", or ";".    o  Strings with leading or trailing spaces    o  Strings containing consecutive spaces   There is an escape mechanism from the normal user oriented form, so   that this syntax may be used to print any valid distinguished name.   This is ugly.  It is expected to be used only in pathological cases.   There are two parts to this mechanism:   1.  Attributes types are represented in a (big-endian) dotted       notation.  (e.g., OID.2.6.53).   2.  Attribute values are represented in hexadecimal (e.g.  #0A56CF).       Each pair of hex digits defines an octet, which is the ASN.1 Basic       Encoding Rules value of the Attribute Value.   The keyword specification is optional in the BNF, but mandatory for   this specification.  This is so that the same BNF may be used for the   related specification on User Friendly Naming [5].  When this   specification is followed, the attribute type keywords must always be   present.   A list of valid keywords for well known attribute types used in   naming is given in Table 1.  Keywords may contain spaces, but shall   not have leading or trailing spaces.  This is a list of keywords   which must be supported.  These are chosen because they appear in   common forms of name, and can do so in a place which does not   correspond to the default schema used.  A register of valid keywords   is maintained by the IANA.Kille                                                           [Page 4]

RFC 1779                   DN Representation                  March 1995   <name> ::= <name-component> ( <spaced-separator> )          | <name-component> <spaced-separator> <name>   <spaced-separator> ::= <optional-space>                   <separator>                   <optional-space>   <separator> ::=  "," | ";"   <optional-space> ::= ( <CR> ) *( " " )   <name-component> ::= <attribute>           | <attribute> <optional-space> "+"             <optional-space> <name-component>   <attribute> ::= <string>           | <key> <optional-space> "=" <optional-space> <string>   <key> ::= 1*( <keychar> ) | "OID." <oid> | "oid." <oid>   <keychar> ::= letters, numbers, and space   <oid> ::= <digitstring> | <digitstring> "." <oid>   <digitstring> ::= 1*<digit>   <digit> ::= digits 0-9   <string> ::= *( <stringchar> | <pair> )            | '"' *( <stringchar> | <special> | <pair> ) '"'            | "#" <hex>   <special> ::= "," | "=" | <CR> | "+" | "<" |  ">"            | "#" | ";"   <pair> ::= "\" ( <special> | "\" | '"')   <stringchar> ::= any character except <special> or "\" or '"'   <hex> ::= 2*<hexchar>   <hexchar> ::= 0-9, a-f, A-F               Figure 1:  BNF Grammar for Distinguished NameKille                                                           [Page 5]

RFC 1779                   DN Representation                  March 1995                       Key     Attribute (X.520 keys)                       ------------------------------                       CN      CommonName                       L       LocalityName                       ST      StateOrProvinceName                       O       OrganizationName                       OU      OrganizationalUnitName                       C       CountryName                       STREET  StreetAddress                      Table 1:  Standardised Keywords   Only string type attributes are considered, but other attribute   syntaxes could be supported locally (e.g., by use of the syntexes   defined in [3].)  It is assumed that the interface will translate   from the supplied string into an appropriate Directory String   encoding.  The "+" notation is used to specify multi-component RDNs.   In this case, the types for attributes in the RDN must be explicit.   The name is presented/input in a little-endian order (most   significant component last).  When an address is written in a context   where there is a need to delimit the entire address (e.g., in free   text), it is recommended that the delimiters <> are used.  The   terminator > is a special in the notation to facilitate this   delimitation.3.  Examples   This section gives a few examples of distinguished names written   using this notation:   CN=Marshall T. Rose, O=Dover Beach Consulting, L=Santa Clara,   ST=California, C=US   CN=FTAM Service, CN=Bells, OU=Computer Science,   O=University College London, C=GB   CN=Markus Kuhn, O=University of Erlangen, C=DE   CN=Steve Kille,   O=ISODE Consortium,   C=GBKille                                                           [Page 6]

RFC 1779                   DN Representation                  March 1995   CN=Steve Kille ,   O =   ISODE Consortium,   C=GB   CN=Steve Kille, O=ISODE Consortium, C=GB4.  Acknowledgements   This work was based on research work done at University College   London [4], and evolved by the IETF OSI-DS WG.   Input for this version of the document was received from:  Allan   Cargille (University of Wisconsin); John Dale (COS); Philip Gladstone   (Onsett); John Hawthorne (US Air Force); Roland Hedberg (University   of Umea); Kipp Hickman (Mosaic Communications Corp.)  Markus Kuhn   (University of Erlangen); Elisabeth Roudier (E3X); Mark Wahl (ISODE   Consortium).5.  References   [1] The Directory --- overview of concepts, models and services,       1993. CCITT X.500 Series Recommendations.   [2] Crocker, D., "Standard of the Format of ARPA-Internet Text       Messages", STD 11,RFC 822, University of Delaware, August 1982.   [3] Yeong, W., Howes, T., and S. Kille, "Lightweight Directory Access       Protocol",RFC 1777, Performance Systems International,       University of Michigan, ISODE Consortium, March 1995.   [4] S.E. Kille. Using the OSI directory to achieve user friendly       naming. Research Note RN/20/29, Department of Computer Science,       University College London, February 1990.   [5] Kille, S., "Using the OSI Directory to Achieve User Friendly       Naming",RFC 1781, ISODE Consortium, March 1995.Kille                                                           [Page 7]

RFC 1779                   DN Representation                  March 19956.  Security Considerations   Security issues are not discussed in this memo.7.  Author's Address   Steve Kille   ISODE Consortium   The Dome   The Square   Richmond, Surrey   TW9 1DT   England   Phone:  +44-181-332-9091   EMail:  S.Kille@ISODE.COM   DN: CN=Steve Kille,   O=ISODE Consortium, C=GB   UFN: S. Kille,   ISODE Consortium, GBKille                                                           [Page 8]