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Versions: (RFC 4627) 00 01 02 03 04 05 06 07 08 09 10 RFC 7158

Operations Area Working Group                               D. Crockford
Internet-Draft                                                  JSON.org
Intended status: Standards Track                           June 06, 2013
Expires: December 08, 2013


                    The JSON Data Interchange Format
                     draft-ietf-json-rfc4627bis-01

Abstract

   JSON is a lightweight, text-based, language-independent data
   interchange format.  It was derived from the ECMAScript Programming
   Language Standard.  JSON defines a small set of formatting rules for
   the portable representation of structured data.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 08, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   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 Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   2
     1.2.  Changes from RFC 4627 . . . . . . . . . . . . . . . . . .   3
   2.  JSON Grammar  . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Values  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Objects . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Arrays  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.4.  Numbers . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.5.  Strings . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Parsers . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Generators  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   JSON is a text format for the serialization of structured data.  It
   was inspired by the object literals of JavaScript, as defined in the
   ECMAScript Programming Language Standard, Fifth Edition[ECMA].

   JSON can represent four primitive types (strings, numbers, booleans,
   and null) and two structured types (objects and arrays).

   A string is a sequence of zero or more characters.

   An object is an unordered collection of zero or more name/value
   pairs, where a name is a string and a value is a string, number,
   boolean, null, object, or array.

   An array is an ordered sequence of zero or more values.

   The terms "object" and "array" come from the conventions of
   JavaScript.

   JSON's design goals were for it to be minimal, portable, textual, and
   a subset of JavaScript.  JSON stands for JavaScript Object Notation.

1.1.  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 [RFC2119].





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   The grammatical rules in this document are to be interpreted as
   described in [RFC5234].

1.2.  Changes from RFC 4627

   This section lists all changes between this document and the text in
   RFC 4627.

   o  Applied errata #607 from RFC 4627 to correctly align the artwork
      for the definition of "object".

2.  JSON Grammar

   A JSON text is a sequence of tokens.  The set of tokens includes six
   structural characters, strings, numbers, and three literal names.

   A JSON text is a serialized object or array.

   JSON-text = object / array


   These are the six structural characters:

      begin-array     = ws %x5B ws  ; [ left square bracket

      begin-object    = ws %x7B ws  ; { left curly bracket

      end-array       = ws %x5D ws  ; ] right square bracket

      end-object      = ws %x7D ws  ; } right curly bracket

      name-separator  = ws %x3A ws  ; : colon

      value-separator = ws %x2C ws  ; , comma


   Insignificant whitespace is allowed before or after any of the six
   structural characters.

   ws = *(
           %x20 /              ; Space
           %x09 /              ; Horizontal tab
           %x0A /              ; Line feed or New line
           %x0D                ; Carriage return
       )






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2.1.  Values

   A JSON value MUST be an object, array, number, or string, or one of
   the following three literal names:

   false null true


   The literal names MUST be lowercase.  No other literal names are
   allowed.

      value = false / null / true / object / array / number / string

      false = %x66.61.6c.73.65   ; false

      null  = %x6e.75.6c.6c      ; null

      true  = %x74.72.75.65      ; true


2.2.  Objects

   An object structure is represented as a pair of curly brackets
   surrounding zero or more name/value pairs (or members).  A name is a
   string.  A single colon comes after each name, separating the name
   from the value.  A single comma separates a value from a following
   name.  The names within an object SHOULD be unique.  If a key is
   duplicated, a parser MAY reject.  If it does not reject, then it MUST
   take only the last of the duplicated key pairs.

      object = begin-object [ member *( value-separator member ) ]
               end-object

      member = string name-separator value


2.3.  Arrays

   An array structure is represented as square brackets surrounding zero
   or more values (or elements).  Elements are separated by commas.

   array = begin-array [ value *( value-separator value ) ] end-array


2.4.  Numbers

   A number is represented in base 10 with no superfluous leading zeroes
   or punctuation such as commas or spaces.  It may have a preceding



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   minus sign.  It may have a "."-prefixed fractional part.  It may have
   an exponent, prefixed by "e" or "E" and optionally "+" or "-".

   Numeric values that cannot be represented as sequences of digits
   (such as Infinity and NaN) are not permitted.

      number = [ minus ] int [ frac ] [ exp ]

      decimal-point = %x2E       ; .

      digit1-9 = %x31-39         ; 1-9

      e = %x65 / %x45            ; e E

      exp = e [ minus / plus ] 1*DIGIT

      frac = decimal-point 1*DIGIT

      int = zero / ( digit1-9 *DIGIT )

      minus = %x2D               ; -

      plus = %x2B                ; +

      zero = %x30                ; 0


2.5.  Strings

   The representation of strings is similar to conventions used in the C
   family of programming languages.  A string is a sequence of code
   units wrapped with quotation marks.  All characters may be placed
   within the quotation marks except for the characters that must be
   escaped: quotation mark, reverse solidus, and the control characters
   (U+0000 through U+001F).

   Any character may be escaped.  If the character is in the Basic
   Multilingual Plane (U+0000 through U+FFFF), then it may be
   represented as a six-character sequence: a reverse solidus, followed
   by the lowercase letter u, followed by four hexadecimal digits that
   encode the character's Unicode code point.  The hexadecimal letters A
   though F can be upper or lowercase.  So, for example, a string
   containing only a single reverse solidus character may be represented
   as "\u005C".







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   Alternatively, there are two-character sequence escape
   representations of some popular characters.  So, for example, a
   string containing only a single reverse solidus character may be
   represented more compactly as "\\".

      string = quotation-mark *char quotation-mark

      char = unescaped /
          escape (
              %x22 /          ; "    quotation mark  U+0022
              %x5C /          ; \    reverse solidus U+005C
              %x2F /          ; /    solidus         U+002F
              %x62 /          ; b    backspace       U+0008
              %x66 /          ; f    form feed       U+000C
              %x6E /          ; n    line feed       U+000A
              %x72 /          ; r    carriage return U+000D
              %x74 /          ; t    tab             U+0009
              %x75 4HEXDIG )  ; uXXXX                U+XXXX

      escape = %x5C           ; \

      quotation-mark = %x22   ; "

      unescaped = %x20-21 / %x23-5B / %x5D-10FFFF


   The following four cases MUST all produce the same result:

   "\u002F"
   "\u002F"
   "\/"
   "/"


   To escape an extended character that is not in the Basic Multilingual
   Plane, the character is represented as a twelve-character sequence,
   encoding the UTF-16 surrogate pair.  So for example, a string
   containing only the G clef character (U+1D11E) may be represented as
   "\uD834\uDD1E".  A generator SHOULD NOT emit unpaired surrogates.  A
   parser MAY reject JSON text containing unpaired surrogates.

3.  Parsers

   A JSON parser transforms a JSON text into another representation.  A
   JSON parser MUST accept all texts that conform to the JSON grammar.
   A JSON parser MAY accept non-JSON forms or extensions.





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   An implementation may set limits on the size of texts that it
   accepts.  An implementation may set limits on the maximum depth of
   nesting.  An implementation may set limits on the range of numbers.
   An implementation may set limits on the length and character contents
   of strings.

4.  Generators

   A JSON generator produces JSON text.  The resulting text MUST
   strictly conform to the JSON grammar.

5.  Security Considerations

   With any data format, it is important to encode correctly.  Care must
   be taken when constructing JSON texts by concatenation.  For example:

   account = 4627;
   comment = "\",\"account\":262";   // provided by attacker
   json_text = "(\"account\":" + account + ",\"comment\":\"" + comment + "\"}";


   The result will be

   {"account":4627,"comment":"","account":262}


   which some parsers MAY see as being the same as

   {"comment":"","account":262}


   This confusion allows an attacker to modify the account property or
   any other property.

   It is much wiser to use JSON generators, which are available in many
   forms for most programming languages, to do the encoding, avoiding
   the confusion hazard.

   JSON is so similar to some programming languages that the native
   parsing ability of the language processors can be used to parse JSON
   texts.  This should be avoided because the native parser will accept
   code which is not JSON.

   For example, JavaScript's eval() function is able parse JSON text,
   but is can also parse programs.  If an attacker can inject code into
   the JSON text (as we saw above), then it can compromise the system.
   JSON parsers should always be used instead.




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   The web browser's script tag is an alias for the eval() function.  It
   should not be used to deliver JSON text to web browsers.

6.  Examples

   This is a JSON object:

   {
     "Image": {
         "Width":  800,
         "Height": 600,
         "Title":  "View from 15th Floor",
         "Thumbnail": {
             "Url":    "http://www.example.com/image/481989943",
             "Height": 125,
             "Width":  "100"
         },
         "IDs": [116, 943, 234, 38793]
       }
   }


   Its Image member is an object whose Thumbnail member is an object and
   whose IDs member is an array of numbers.

   This is a JSON array containing two objects:

   [
     {
        "precision": "zip",
        "Latitude":  37.7668,
        "Longitude": -122.3959,
        "Address":   "",
        "City":      "SAN FRANCISCO",
        "State":     "CA",
        "Zip":       "94107",
        "Country":   "US"
     },
     {
        "precision": "zip",
        "Latitude":  37.371991,
        "Longitude": -122.026020,
        "Address":   "",
        "City":      "SUNNYVALE",
        "State":     "CA",
        "Zip":       "94085",
        "Country":   "US"
     }



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   ]


7.  Normative References

   [ECMA]     European Computer Manufacturers Association, "ECMAScript
              Language Specification Fifth Edition ", December 2009,
              <http://www.ecma-international.org/publications/files/
              ecma-st/ECMA-262.pdf>.

   [RFC0020]  Cerf, V., "ASCII format for network interchange", RFC 20,
              October 1969.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [UNICODE]  The Unicode Consortium, "The Unicode Standard, Version 6.2
              ", 2012, <http://www.unicode.org/versions/Unicode6.2.0/>.

Author's Address

   Douglas Crockford
   JSON.org

   Email: douglas@crockford.com























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