Operations Area Working Group D. Crockford Internet-Draft JSON.org Intended status: Standards Track June06,05, 2013 Expires: December08,07, 2013 TheJSON Data Interchange Format draft-ietf-json-rfc4627bis-01application/json Media Type for JavaScript Object Notation (JSON) draft-ietf-json-rfc4627bis-02 AbstractJSONJavaScript Object Notation (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 working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on December08,07, 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 Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must 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. 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 .Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.GeneratorsParsers . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.Security ConsiderationsGenerators . . . . . . . . . . . . . . . . . . . . . . . . . 7 6.ExamplesIANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 87.8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9. Normative References . . . . . . . . . . . . . . . . . . . .910 Author's Address . . . . . . . . . . . . . . . . . . . . . . . .911 1. IntroductionJSONJavaScript Object Notation (JSON) is a text format for the serialization of structured data. Itwas inspired byis derived from the object literals of JavaScript, as defined in the ECMAScript Programming Language Standard,Fifth Edition[ECMA].Third 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 morecharacters.Unicode characters [UNICODE]. 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]. The grammatical rules in this document are to be interpreted as described in[RFC5234].[RFC4234]. 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 ) 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. NumbersA numberThe representation of numbers isrepresentedsimilar to that used inbase 10 with no superfluous leading zeroes or punctuation such as commas or spaces. Itmost programming languages. A number contains an integer component that mayhave a precedingbe prefixed with an optional minussign. Itsign, which mayhavebe followed by a"."-prefixed fractionalfraction part and/or an exponent part.ItOctal and hex forms are not allowed. Leading zeros are not allowed. A fraction part is a decimal point followed by one or more digits. An exponent part begins with the letter E in upper or lowercase, which mayhave an exponent, prefixedbe followed by"e"a plus or"E"minus sign. The E andoptionally "+"optional sign are followed by one or"-".more digits. 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 stringis a sequence of code units wrappedbegins and ends with quotation marks. All Unicode 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'sUnicodecode 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". 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 "\\". 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". 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-10FFFFThe following four cases MUST all produce the same result: "\u002F" "\u002F" "\/" "/" To escape an extended character that is not3. Encoding JSON text SHALL be encoded inthe Basic Multilingual Plane, the character is represented as a twelve-character sequence,Unicode. The default encoding is UTF-8. Since theUTF-16 surrogate pair. So for example,first two characters of astring containing only the G clef character (U+1D11E) may be represented as "\uD834\uDD1E". A generator SHOULD NOT emit unpaired surrogates. A parser MAY rejectJSON textcontaining unpaired surrogates. 3.will always be ASCII characters [RFC0020], it is possible to determine whether an octet stream is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking at the pattern of nulls in the first four octets. 00 00 00 xx UTF-32BE 00 xx 00 xx UTF-16BE xx 00 00 00 UTF-32LE xx 00 xx 00 UTF-16LE xx xx xx xx UTF-8 4. 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. 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.4.5. Generators A JSON generator produces JSON text. The resulting text MUST strictly conform to the JSON grammar.5. Security6. IANA ConsiderationsWith any data format, itThe MIME media type for JSON text isimportant to encode correctly. Care must be taken when constructingapplication/json. Type name: application Subtype name: json Required parameters: n/a Optional parameters: n/a Encoding considerations: 8bit if UTF-8; binary if UTF-16 or UTF-32 JSONtexts by concatenation. For example: account = 4627; comment = "\",\"account\":262"; // provided by attacker json_text = "(\"account\":" + account + ",\"comment\":\"" + comment + "\"}"; The result willmay 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 propertyrepresented using UTF-8, UTF-16, orany other property. It is much wiser to useUTF-32. When JSONgenerators, which are availableis written inmany forms for most programming languages, to do the encoding, avoiding the confusion hazard.UTF-8, JSON isso similar to some programming languages that the native parsing ability of8bit compatible. When JSON is written in UTF-16 or UTF-32, thelanguage processors canbinary content-transfer-encoding must beused to parseused. Security considerations: Generally there are security issues with scripting languages. JSONtexts. This should be avoided because the native parser will accept code whichisnot JSON. For example, JavaScript's eval() function is able parse JSON text,a subset of JavaScript, but it iscan also parse programs. If an attacker can inject code into thea safe subset that excludes assignment and invocation. A JSON text(as we saw above), then itcancompromise the system. JSON parsers should alwaysbeused instead. The web browser's script tag is an alias for thesafely passed into JavaScript's eval()function. It shouldfunction (which compiles and executes a string) if all the characters not enclosed in strings are in the set of characters that form JSON tokens. This can beusedquickly determined in JavaScript with two regular expressions and calls todeliver JSONthe test and replace methods. var my_JSON_object = !(/[^,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]/.test( text.replace(/"(\\.|[^"\\])*"/g, ''))) && eval('(' + text + ')'); Interoperability considerations: n/a Published specification: RFC 4627 Applications that use this media type: JSON has been used toweb browsers.exchange data between applications written in all of these programming languages: ActionScript, C, C#, ColdFusion, Common Lisp, E, Erlang, Java, JavaScript, Lua, Objective CAML, Perl, PHP, Python, Rebol, Ruby, and Scheme. Additional information: Magic number(s): n/a File extension(s): .json Macintosh file type code(s): TEXT Person & email address to contact for further information: Douglas Crockford douglas@crockford.com Intended usage: COMMON Restrictions on usage: none Author: Douglas Crockford douglas@crockford.com Change controller: Douglas Crockford douglas@crockford.com 7. Security Considerations See Security Considerations in Section 6. 8. 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" } ]7.9. Normative References [ECMA] European Computer Manufacturers Association, "ECMAScript Language SpecificationFifth3rd Edition ", December2009,1999, <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][RFC4234] Crocker,D.D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF",STD 68,RFC5234, January 2008.4234, October 2005. [UNICODE] The Unicode Consortium, "The Unicode Standard, Version6.24.0 ",2012, <http://www.unicode.org/versions/Unicode6.2.0/>.2003, <http://www.unicode.org/versions/Unicode4.1.0/>. Author's Address Douglas Crockford JSON.org Email: douglas@crockford.com