One document matched: draft-ietf-json-rfc4627bis-01.xml
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<rfc
category="std"
docName="draft-ietf-json-rfc4627bis-01"
ipr="trust200902"
>
<front>
<title abbrev="JSON bis">The JSON Data Interchange Format</title>
<author fullname="Douglas Crockford" initials="D." surname="Crockford">
<organization>JSON.org</organization>
<address>
<email>douglas@crockford.com</email>
</address>
</author>
<date year="2013" month="June"/>
<area>Operations and Management</area>
<workgroup>Operations Area Working Group</workgroup>
<abstract>
<t>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.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>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<xref target="ECMA"/>.</t>
<t>JSON can represent four primitive types (strings, numbers, booleans,
and null) and two structured types (objects and arrays).</t>
<t>A string is a sequence of zero or more characters.</t>
<t>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.</t>
<t>An array is an ordered sequence of zero or more values.</t>
<t>The terms "object" and "array" come from the conventions of
JavaScript.</t>
<t>JSON's design goals were for it to be minimal, portable, textual, and
a subset of JavaScript. JSON stands for JavaScript Object Notation.</t>
<section title="Conventions Used in This Document">
<t>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 <xref target="RFC2119" />.</t>
<t>The grammatical rules in this document are to be interpreted as
described in <xref target="RFC5234" />.</t>
</section>
<section title="Changes from RFC 4627">
<t>This section lists all changes between this document
and the text in RFC 4627.</t>
<t><list style="symbols">
<t>Applied errata #607 from RFC 4627 to correctly align the artwork for the
definition of "object".</t>
</list></t>
</section>
</section>
<section title="JSON Grammar">
<t>A JSON text is a sequence of tokens. The set of tokens includes six
structural characters, strings, numbers, and three literal names.</t>
<t>A JSON text is a serialized object or array.</t>
<figure><artwork>
JSON-text = object / array
</artwork></figure>
<t>These are the six structural characters:</t>
<figure><artwork>
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
</artwork></figure>
<t>Insignificant whitespace is allowed before or after any of the six
structural characters.</t>
<figure><artwork>
ws = *(
%x20 / ; Space
%x09 / ; Horizontal tab
%x0A / ; Line feed or New line
%x0D ; Carriage return
)
</artwork></figure>
<section title="Values">
<t>A JSON value MUST be an object, array, number, or string, or one of
the following three literal names:</t>
<figure><artwork>
false null true
</artwork></figure>
<t>The literal names MUST be lowercase. No other literal names are
allowed.</t>
<figure><artwork>
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
</artwork></figure>
</section>
<section title="Objects">
<t>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.</t>
<figure><artwork>
object = begin-object [ member *( value-separator member ) ]
end-object
member = string name-separator value
</artwork></figure>
</section>
<section title="Arrays">
<t>An array structure is represented as square brackets surrounding zero
or more values (or elements). Elements are separated by commas.</t>
<figure><artwork>
array = begin-array [ value *( value-separator value ) ] end-array
</artwork></figure>
</section>
<section title="Numbers">
<t>A number is represented in base 10 with no superfluous leading zeroes or
punctuation such as commas or spaces. It may have a preceding minus sign.
It may have a "."-prefixed fractional part. It may have an exponent,
prefixed by "e" or "E" and optionally "+" or "-".
</t>
<t>Numeric values that cannot be represented as sequences of digits
(such as Infinity and NaN) are not permitted.</t>
<figure><artwork>
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
</artwork></figure>
</section>
<section title="Strings">
<t>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).</t>
<t>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".</t>
<t>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 "\\".</t>
<figure><artwork>
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
</artwork></figure>
<t>The following four cases MUST all produce the same result:</t>
<figure><artwork>
"\u002F"
"\u002F"
"\/"
"/"
</artwork></figure>
<t>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.</t>
</section>
</section>
<section title="Parsers">
<t>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.</t>
<t>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.</t>
</section>
<section title="Generators">
<t>A JSON generator produces JSON text. The resulting text MUST
strictly conform to the JSON grammar.</t>
</section>
<section title="Security Considerations">
<t>With any data format, it is important to encode correctly. Care must be
taken when constructing JSON texts by concatenation. For example:</t>
<figure><artwork>
account = 4627;
comment = "\",\"account\":262"; // provided by attacker
json_text = "(\"account\":" + account + ",\"comment\":\"" + comment + "\"}";
</artwork></figure>
<t>The result will be</t>
<figure><artwork>
{"account":4627,"comment":"","account":262}
</artwork></figure>
<t>which some parsers MAY see as being the same as</t>
<figure><artwork>
{"comment":"","account":262}
</artwork></figure>
<t>This confusion allows an attacker to modify the account property or any
other property.</t>
<t>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.</t>
<t>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.</t>
<t>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.</t>
<t>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.</t>
</section>
<section title="Examples">
<t>This is a JSON object:</t>
<figure><artwork>
{
"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]
}
}
</artwork></figure>
<t>Its Image member is an object whose Thumbnail member is an object
and whose IDs member is an array of numbers.</t>
<t>This is a JSON array containing two objects:</t>
<figure><artwork>
[
{
"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"
}
]
</artwork></figure>
</section>
</middle>
<back>
<references title="Normative References">
<reference anchor="ECMA" target="http://www.ecma-international.org/publications/files/ecma-st/ECMA-262.pdf">
<front>
<title abbrev="ECMAScript 5th">
ECMAScript Language Specification Fifth Edition
</title>
<author>
<organization>European Computer Manufacturers Association</organization>
<address />
</author>
<date month="December" year="2009"/>
</front>
</reference>
&RFC0020;
&RFC2119;
&RFC5234;
<reference anchor="UNICODE" target="http://www.unicode.org/versions/Unicode6.2.0/">
<front>
<title abbrev="Unicode 6.2">
The Unicode Standard, Version 6.2
</title>
<author>
<organization>The Unicode Consortium</organization>
<address />
</author>
<date year="2012"/>
</front>
</reference>
</references>
</back>
</rfc>
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