Title
draft-hallambaker-jsonbcd-04
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
|
|
|---|---|---|---|
| Author | Phillip Hallam-Baker | ||
| Last updated | 2016-03-08 | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-hallambaker-jsonbcd-04
Network Working Group P. Hallam-Baker
Internet-Draft Comodo Group Inc.
Intended status: Informational March 8, 2016
Expires: September 9, 2016
Title
draft-hallambaker-jsonbcd-04
Abstract
Binary Encodings for JavaScript Object Notation: JSON-B, JSON-C,
JSON-D
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 September 9, 2016.
Copyright Notice
Copyright (c) 2016 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.
Hallam-Baker Expires September 9, 2016 [Page 1]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
1. Abstract
Three binary encodings for JavaScript Object Notation (JSON) are
presented. JSON-B (Binary) is a strict superset of the JSON encoding
that permits efficient binary encoding of intrinsic JavaScript data
types. JSON-C (Compact) is a strict superset of JSON-B that supports
compact representation of repeated data strings with short numeric
codes. JSON-D (Data) supports additional binary data types for
integer and floating point representations for use in scientific
applications where conversion between binary and decimal
representations would cause a loss of precision.
2. Definitions
2.1. Requirements Language
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].
3. Introduction
JavaScript Object Notation (JSON) is a simple text encoding for the
JavaScript Data model that has found wide application beyond its
original field of use. In particular JSON has rapidly become a
preferred encoding for Web Services.
JSON encoding supports just four fundamental data types (integer,
floating point, string and boolean), arrays and objects which consist
of a list of tag-value pairs.
Although the JSON encoding is sufficient for many purposes it is not
always efficient. In particular there is no efficient representation
for blocks of binary data. Use of base64 encoding increases data
volume by 33%. This overhead increases exponentially in applications
where nested binary encodings are required making use of JSON
encoding unsatisfactory in cryptographic applications where nested
binary structures are frequently required.
Another source of inefficiency in JSON encoding is the repeated
occurrence of object tags. A JSON encoding containing an array of a
hundred objects such as {"first":1,"second":2} will contain a hundred
occurrences of the string "first" (seven bytes) and a hundred
occurrences of the string "second" (eight bytes). Using two byte
code sequences in place of strings allows a saving of 11 bytes per
object without loss of information, a saving of 50%.
Hallam-Baker Expires September 9, 2016 [Page 2]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
A third objection to the use of JSON encoding is that floating point
numbers can only be represented in decimal form and this necessarily
involves a loss of precision when converting between binary and
decimal representations. While such issues are rarely important in
network applications they can be critical in scientific applications.
It is not acceptable for saving and restoring a data set to change
the result of a calculation.
3.1. Objectives
The following were identified as core objectives for a binary JSON
encoding:
o
* Low overhead encoding and decoding
* Easy to convert existing encoders and decoders to add binary
support
* Efficient encoding of binary data
* Ability to convert from JSON to binary encoding in a streaming
mode (i.e. without reading the entire binary data block before
beginning encoding.
* Lossless encoding of JavaScript data types
* The ability to support JSON tag compression and extended data
types are considered desirable but not essential for typical
network applications.
Three binary encodings are defined:
JSON-B (Binary)
Simply encodes JSON data in binary. Only the JavaScript data model
is supported (i.e. atomic types are integers, double or string).
Integers may be 8, 16, 32 or 64 bits either signed or unsigned.
Floating points are IEEE 754 binary64 format [IEEE-754]. Supports
chunked encoding for binary and UTF-8 string types.
JSON-C (Compact)
As JSON-B but with support for representing JSON tags in numeric code
form (16 bit code space). This is done for both compact encoding and
to allow simplification of encoders/decoders in constrained
Hallam-Baker Expires September 9, 2016 [Page 3]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
environments. Codes may be defined inline or by reference to a known
dictionary of codes referenced via a digest value.
JSON-D (Data)
As JSON-C but with support for representing additional data types
without loss of precision. In particular other IEEE 754 floating
point formats, both binary and decimal and Intel's 80 bit floating
point, plus 128 bit integers and bignum integers.
4. Extended JSON Grammar
The JSON-B, JSON-C and JSON-D encodings are all based on the JSON
grammar [RFC4627] using the same syntactic structure but different
lexical encodings.
JSON-B0 and JSON-C0 replace the JSON lexical encodings for strings
and numbers with binary encodings. JSON-B1 and JSON-C1 allow either
lexical encoding to be used. Thus any valid JSON encoding is a valid
JSON-B1 or JSON-C1 encoding.
The grammar of JSON-B, JSON-C and JSON-D is a superset of the JSON
grammar. The following productions are added to the grammar:
x-value
Binary encodings for data values. As the binary value encodings are
all self delimiting
x-member
An object member where the value is specified as an X-value and thus
does not require a value-separator.
b-value
Binary data encodings defined in JSON-B.
b-string
Defined length string encoding defined in JSON-B.
c-def
Tag code definition defined in JSON-C. These may only appear before
the beginning of an Object or Array and before any preceeding white
space.
Hallam-Baker Expires September 9, 2016 [Page 4]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
c-tag
Tag code value defined in JSON-C.
d-value
Additional binary data encodings defined in JSON-D for use in
scientific data applications.
The JSON grammar is modified to permit the use of x-value productions
in place of ( value value-separator ) :
JSON-text = (object / array)
object = *cdef begin-object [
*( member value-separator | x-member )
(member | x-member) ] end-object
member = tag value
x-member = tag x-value
tag = string name-separator | b-string | c-tag
array = *cdef begin-array [ *( value value-separator | x-value )
(value | x-value) ] end-array
x-value = b-value / d-value
value = false / null / true / object / array / number / string
name-separator = ws %x3A ws ; : colon
value-separator = ws %x2C ws ; , comma
The following lexical values are unchanged:
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
ws = *( %x20 %x09 %x0A %x0D )
false = %x66.61.6c.73.65 ; false
null = %x6e.75.6c.6c ; null
true = %x74.72.75.65 ; true
The productions number and string are defined as before:
Hallam-Baker Expires September 9, 2016 [Page 5]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
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
string = quotation-mark *char quotation-mark
char = unescaped /
escape ( %x22 / %x5C / %x2F / %x62 / %x66 /
%x6E / %x72 / %x74 / %x75 4HEXDIG )
escape = %x5C ; \
quotation-mark = %x22 ; "
unescaped = %x20-21 / %x23-5B / %x5D-10FFFF
5. JSON-B
The JSON-B encoding defines the b-value and b-string productions:
b-value = b-atom | b-string | b-data | b-integer |
b-float
b-string = *( string-chunk ) string-term
b-data = *( data-chunk ) data-last
b-integer = p-int8 | p-int16 | p-int32 | p-int64 | p-bignum16 |
n-int8 | n-int16 | n-int32 | n-int64 | n-bignum16
b-float = binary64
The lexical encodings of the productions are defined in the following
table where the column 'tag' specifies the byte code that begins the
production, 'Fixed' specifies the number of data bytes that follow
and 'Length' specifies the number of bytes used to define the length
of a variable length field following the data bytes:
+--------------+-----+-------+--------+-----------------------------+
| Production | Tag | Fixed | Length | Data Description |
+--------------+-----+-------+--------+-----------------------------+
| string-term | x80 | - | 1 | Terminal String 8 bit |
Hallam-Baker Expires September 9, 2016 [Page 6]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
| | | | | length |
| | | | | |
| string-term | x81 | - | 2 | Terminal String 16 bit |
| | | | | length |
| | | | | |
| string-term | x82 | - | 4 | Terminal String 32 bit |
| | | | | length |
| | | | | |
| string-term | x83 | - | 8 | Terminal String 64 bit |
| | | | | length |
| | | | | |
| string-chunk | x84 | - | 1 | Non-Terminal String 8 bit |
| | | | | length |
| | | | | |
| string-chunk | x85 | - | 2 | Non-Terminal String 16 bit |
| | | | | length |
| | | | | |
| string-chunk | x86 | - | 4 | Non-Terminal String 32 bit |
| | | | | length |
| | | | | |
| string-chunk | x87 | - | 8 | Non-Terminal String 64 bit |
| | | | | length |
| | | | | |
| data-term | x88 | - | 1 | Terminal Data 8 bit length |
Hallam-Baker Expires September 9, 2016 [Page 7]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
| | | | | |
| data-term | x89 | - | 2 | Terminal Data 16 bit length |
| | | | | |
| data-term | x8A | - | 4 | Terminal Data 32 bit length |
| | | | | |
| data-term | x8B | - | 8 | Terminal Data 64 bit length |
| | | | | |
| data-chunk | x8C | - | 1 | Non-Terminal Data 8 bit |
| | | | | length |
| | | | | |
| data-chunk | x8D | - | 2 | Non-Terminal Data 16 bit |
| | | | | length |
| | | | | |
| data-chunk | x8E | - | 4 | Non-Terminal Data 32 bit |
| | | | | length |
| | | | | |
| data-chunk | x8F | - | 8 | Non-Terminal String 64 bit |
| | | | | length |
| | | | | |
| p-int8 | xA0 | 1 | - | Positive 8 bit Integer |
| | | | | |
| p-int16 | xA1 | 2 | - | Positive 16 bit Integer |
| | | | | |
| p-int32 | xA2 | 4 | - | Positive 32 bit Integer |
Hallam-Baker Expires September 9, 2016 [Page 8]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
| | | | | |
| p-int64 | xA3 | 8 | - | Positive 64 bit Integer |
| | | | | |
| p-bignum16 | xA5 | - | 2 | Positive Bignum 16 bit |
| | | | | length |
| | | | | |
| n-int8 | xA8 | 1 | - | Negative 8 bit Integer |
| | | | | |
| n-int16 | xA9 | 2 | - | Negative 16 bit Integer |
| | | | | |
| n-int32 | xAA | 4 | - | Negative 32 bit Integer |
| | | | | |
| n-int64 | xAB | 8 | - | Negative 64 bit Integer |
| | | | | |
| n-bignum16 | xAD | - | 2 | Negative Bignum 16 bit |
| | | | | length |
| | | | | |
| binary64 | x92 | 8 | - | IEEE 754 Floating Point |
| | | | | binary64 |
| | | | | |
| b-value | xB0 | - | - | True |
| | | | | |
| b-value | xB1 | - | - | False |
| | | | | |
Hallam-Baker Expires September 9, 2016 [Page 9]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
| b-value | xB2 | - | - | Null |
+--------------+-----+-------+--------+-----------------------------+
A data type commonly used in networking that is not defined in this
scheme is a datetime representation. To define such a data type, a
string containing a date-time value in Internet type format is
typically used.
5.1. JSON-B Examples
The following examples show examples of using JSON-B encoding:
A0 2A 42 (as 8 bit integer)
A1 00 2A 42 (as 16 bit integer)
A2 00 00 00 2A 42 (as 32 bit integer)
A3 00 00 00 00 00 00 00 2A 42 (as 64 bit integer)
A5 00 01 42 42 (as Bignum)
80 05 48 65 6c 6c 6f "Hello" (single chunk)
81 00 05 48 65 6c 6c 6f "Hello" (single chunk)
84 05 48 65 6c 6c 6f 80 00 "Hello" (as two chunks)
92 3f f0 00 00 00 00 00 00 1.0
92 40 24 00 00 00 00 00 00 10.0
92 40 09 21 fb 54 44 2e ea 3.14159265359
92 bf f0 00 00 00 00 00 00 -1.0
B0 true
B1 false
B2 null
6. JSON-C
JSON-C (Compressed) permits numeric code values to be substituted for
strings and binary data. Tag codes MAY be 8, 16 or 32 bits long
encoded in network byte order.
Tag codes MUST be defined before they are referenced. A Tag code MAY
be defined before the corresponding data or string value is used or
at the same time that it is used.
A dictionary is a list of tag code definitions. An encoding MAY
incorporate definitions from a dictionary using the dict-hash
production. The dict hash production specifies a (positive) offset
value to be added to the entries in the dictionary and a hash code
identifier consisting of the ASN.1 OID value sequence for the
Hallam-Baker Expires September 9, 2016 [Page 10]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
cryptographic digest used to compute the hash value followed by the
hash value in network byte order.
+------------+-----+-------+--------+-------------------------------+
| Production | Tag | Fixed | Length | Data Description |
+------------+-----+-------+--------+-------------------------------+
| c-tag | xC0 | 1 | - | 8 bit tag code |
| | | | | |
| c-tag | xC1 | 2 | - | 16 bit tag code |
| | | | | |
| c-tag | xC2 | 4 | - | 32 bit tag code |
| | | | | |
| c-def | xC4 | 1 | - | 8 bit tag definition |
| | | | | |
| c-def | xC5 | 2 | - | 16 bit tag definition |
| | | | | |
| c-def | xC6 | 4 | - | 32 bit tag definition |
| | | | | |
| c-tag | xC8 | 1 | - | 8 bit tag code & definition |
| | | | | |
| c-tag | xC9 | 2 | - | 16 bit tag code & definition |
| | | | | |
| c-tag | xCA | 4 | - | 32 bit tag code & definition |
| | | | | |
| c-def | xCC | 1 | - | 8 bit tag dictionary |
| | | | | definition |
Hallam-Baker Expires September 9, 2016 [Page 11]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
| | | | | |
| c-def | xCD | 2 | - | 16 bit tag dictionary |
| | | | | definition |
| | | | | |
| c-def | xCE | 4 | - | 32 bit tag dictionary |
| | | | | definition |
| | | | | |
| dict-hash | xD0 | 4 | 1 | Hash of dictionary |
+------------+-----+-------+--------+-------------------------------+
All integer values are encoded in Network Byte Order (most
significant byte first).
6.1. JSON-C Examples
The following examples show examples of using JSON-C encoding:
C8 20 80 05 48 65 6c 6c 6f "Hello" 20 = "Hello"
C4 21 80 05 48 65 6c 6c 6f 21 = "Hello"
C0 20 "Hello"
C1 00 20 "Hello"
D0 00 00 01 00 1B 277 = "Hello"
06 09 60 86 48 01 65 03
04 02 01 OID for SHA-2-256
e3 b0 c4 42 98 fc 1c 14
9a fb f4 c8 99 6f b9 24
27 ae 41 e4 64 9b 93 4c
a4 95 99 1b 78 52 b8 55 SHA-256(C4 21 80 05 48 65 6c 6c 6f)
[2.16.840.1.101.3.4.2.1]
7. JSON-D (Data)
JSON-B and JSON-C only support the two numeric types defined in the
JavaScript data model: Integers and 64 bit floating point values.
JSON-D (Data) defines binary encodings for additional data types that
are commonly used in scientific applications. These comprise
positive and negative 128 bit integers, six additional floating point
representations defined by IEEE 754 [RFC2119] and the Intel extended
precision 80 bit floating point representation.
Hallam-Baker Expires September 9, 2016 [Page 12]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
Should the need arise, even bigger bignums could be defined with the
length specified as a 32 bit value permitting bignums of up to 2^35
bits to be represented.
d-value = d-integer | d-float
d-float = binary16 | binary32 | binary128 | binary80 |
decimal32 | decimal64 | decimal 128
8.
+------------+-----+-------+--------+-------------------------------+
| Production | Tag | Fixed | Length | Data Description |
+------------+-----+-------+--------+-------------------------------+
| p-int128 | xA4 | 16 | - | Positive 128 bit Integer |
| | | | | |
| n-in7128 | xAC | 16 | - | Negative 128 bit Integer |
| | | | | |
| binary16 | x90 | 2 | - | IEEE 754 Floating Point |
| | | | | binary16 |
| | | | | |
| binary32 | x91 | 4 | - | IEEE 754 Floating Point |
| | | | | binary32 |
| | | | | |
| binary128 | x94 | 16 | - | IEEE 754 Floating Point |
| | | | | binary128 |
| | | | | |
| intel80 | x95 | 10 | - | Intel 80 bit extended binary |
| | | | | Floating Point |
Hallam-Baker Expires September 9, 2016 [Page 13]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
| | | | | |
| decimal32 | x96 | 4 | - | IEEE 754 Floating Point |
| | | | | decimal32 |
| | | | | |
| decimal64 | x97 | 8 | - | IEEE 754 Floating Point |
| | | | | decimal64 |
| | | | | |
| decimal128 | x98 | 18 | - | IEEE 754 Floating Point |
| | | | | decimal128 |
+------------+-----+-------+--------+-------------------------------+
9.
10. Acknowledgements
This work was assisted by conversations with Nico Williams and other
participants on the applications area mailing list.
11. Security Considerations
A correctly implemented data encoding mechanism should not introduce
new security vulnerabilities. However, experience demonstrates that
some data encoding approaches are more prone to introduce
vulnerabilities when incorrectly implemented than others.
In particular, whenever variable length data formats are used, the
possibility of a buffer overrun vulnerability is introduced. While
best practice suggests that a coding language with native mechanisms
for bounds checking is the best protection against such errors, such
approaches are not always followed. While such vulnerabilities are
most commonly seen in the design of decoders, it is possible for the
same vulnerabilities to be exploited in encoders.
A common source of such errors is the case where nested length
encodings are used. For example, a decoder relies on an outermost
length encoding that specifies a length on 50 bytes to allocate
memory for the entire result and then attempts to copy a string with
a declared length of 1000 bytes within the sequence.
Hallam-Baker Expires September 9, 2016 [Page 14]
Internet-Draft JSON-B, JSON-C, JSON-D March 2016
The extensions to the JSON encoding described in this document are
designed to avoid such errors. Length encodings are only used to
define the length of x-value constructions which are always terminal
and cannot have nested data entries.
12. IANA Considerations
[TBS list out all the code points that require an IANA registration]
13. Normative References
[IEEE-754]
"[Reference Not Found!]".
Author's Address
Phillip Hallam-BakerPhillip Hallam-Baker
Comodo Group Inc.
Email: philliph@comodo.com
Hallam-Baker Expires September 9, 2016 [Page 15]