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Network Working Group                               S. Hardcastle-KilleRequest for Comments: 1485                             ISODE Consortium                                                              July 1993A String Representation of Distinguished Names(OSI-DS 23 (v5))Status of this Memo   This RFC specifies an IAB standards track protocol for the Internet   community, and requests discussion and suggestions for improvements.   Please refer to the current edition of the "IAB Official Protocol   Standards" 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.  Please send comments   to the author or to the discussion group <osi-ds@CS.UCL.AC.UK>.Table of Contents1.  Why a notation is needed......................................12.  A notation for Distinguished Name.............................22.1 Goals.........................................................22.2 Informal definition...........................................22.3 Formal definition.............................................33.  Examples......................................................64.  References....................................................65.  Security Considerations.......................................66.  Author's Address..............................................71.  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 [CCI88].  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 emailHardcastle-Kille                                                [Page 1]

RFC 1485                  Distinguished Names                  July 1993   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 Hardcastle-Kille, OU=Computer Science, O=University      College London, C=GB   This may be folded, perhaps to display in multi-column format.  For   example:      CN=Steve Hardcastle-Kille,      OU=Computer Science,      O=University College London,      C=GBHardcastle-Kille                                                [Page 2]

RFC 1485                  Distinguished Names                  July 1993   Another name might be:      CN=Christian Huitema, O=INRIA, C=FR   Semicolon (";") may be used as an alternate separator.      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,      CN=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 example shows quoting of a comma in an Organisation name:      CN=L. Eagle, O="Sue, Grabbit and Runn", C=GB2.3 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 <> [Cro82].  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:Hardcastle-Kille                                                [Page 3]

RFC 1485                  Distinguished Names                  July 1993      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).   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 [HK93].  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.  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 keyworkds is maintained   by the IANA.   Only string type attributes are considered, but other attribute   syntaxes could be supported locally.  It is assumed that the   interface will translate from the supplied string into   PrintableString or T.61.   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.Hardcastle-Kille                                                [Page 4]

RFC 1485                  Distinguished Names                  July 1993   <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>   <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> ::= "   <stringchar> ::= any char except <special> or "   <hex> ::= 2*<hexchar>   <hexchar> ::= 0-9, a-f, A-F               Figure 1:  BNF Grammar for Distinguished NameHardcastle-Kille                                                [Page 5]

RFC 1485                  Distinguished Names                  July 1993                        Key  Attribute (X.520 keys)                        ______________________________                        CN   CommonName                        L    LocalityName                        ST   StateOrProvinceName                        O    OrganizationName                        OU   OrganizationalUnitName                        C    CountryName                      Table 1:  Standardised Keywords3.  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=Steve Hardcastle-Kille, OU=Computer Science, O=University      College London, C=GB      CN=Steve Hardcastle-Kille, OU=Computer Science, O=University      College London, C=GB4.  References   [CCI88] The Directory --- overview of concepts, models and services,           December 1988. CCITT X.500 Series Recommendations.   [Cro82] D.H. Crocker. Standard of the format of ARPA internet text           messages.  STD 11,RFC 822, University of Delaware,           August 1982.   [HK93]  S.E. Hardcastle-Kille. Using the OSI directory to achieve           user friendly naming.RFC 1484, Department of Computer           Science, University College London, July 1993.5.  Security Considerations   Security issues are not discussed in this memo.Hardcastle-Kille                                                [Page 6]

RFC 1485                  Distinguished Names                  July 19936.  Author's Address   Steve Hardcastle-Kille   ISODE Consortium   P.O. Box 505   London   SW11 1DX   England   Phone:+44-71-223-4062   EMail:  S.Kille@ISODE.COM   DN: CN=Steve Hardcastle-Kille,   O=ISODE Consortium, C=GB   UFN: S. Hardcastle-Kille,   ISODE Consortium, GBHardcastle-Kille                                                [Page 7]