[ViewVC] Diff of: cvs/CBOR-XS/XS.pm

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.27 by root, Thu Nov 28 15:43:24 2013 UTC vs.
Revision 1.77 by root, Fri Dec 4 02:57:14 2020 UTC

…		…
26	substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string	26	substr $many_cbor_strings, 0, $length, ""; # remove decoded cbor string
27	}	27	}
28		28
29	=head1 DESCRIPTION	29	=head1 DESCRIPTION
30		30
31	WARNING! This module is very new, and not very well tested (that's up
32	to you to do). Furthermore, details of the implementation might change
33	freely before version 1.0. And lastly, most extensions depend on an IANA
34	assignment, and until that assignment is official, this implementation is
35	not interoperable with other implementations (even future versions of this
36	module) until the assignment is done.
37
38	You are still invited to try out CBOR, and this module.
39
40	This module converts Perl data structures to the Concise Binary Object	31	This module converts Perl data structures to the Concise Binary Object
41	Representation (CBOR) and vice versa. CBOR is a fast binary serialisation	32	Representation (CBOR) and vice versa. CBOR is a fast binary serialisation
42	format that aims to use a superset of the JSON data model, i.e. when you	33	format that aims to use an (almost) superset of the JSON data model, i.e.
43	can represent something in JSON, you should be able to represent it in	34	when you can represent something useful in JSON, you should be able to
44	CBOR.	35	represent it in CBOR.
45		36
46	In short, CBOR is a faster and very compact binary alternative to JSON,	37	In short, CBOR is a faster and quite compact binary alternative to JSON,
47	with the added ability of supporting serialisation of Perl objects. (JSON	38	with the added ability of supporting serialisation of Perl objects. (JSON
48	often compresses better than CBOR though, so if you plan to compress the	39	often compresses better than CBOR though, so if you plan to compress the
49	data later you might want to compare both formats first).	40	data later and speed is less important you might want to compare both
		41	formats first).
		42
		43	The primary goal of this module is to be I<correct> and the secondary goal
		44	is to be I<fast>. To reach the latter goal it was written in C.
50		45
51	To give you a general idea about speed, with texts in the megabyte range,	46	To give you a general idea about speed, with texts in the megabyte range,
52	C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or	47	C<CBOR::XS> usually encodes roughly twice as fast as L<Storable> or
53	L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the	48	L<JSON::XS> and decodes about 15%-30% faster than those. The shorter the
54	data, the worse L<Storable> performs in comparison.	49	data, the worse L<Storable> performs in comparison.
55		50
56	As for compactness, C<CBOR::XS> encoded data structures are usually about	51	Regarding compactness, C<CBOR::XS>-encoded data structures are usually
57	20% smaller than the same data encoded as (compact) JSON or L<Storable>.	52	about 20% smaller than the same data encoded as (compact) JSON or
		53	L<Storable>.
58		54
59	In addition to the core CBOR data format, this module implements a number	55	In addition to the core CBOR data format, this module implements a
60	of extensions, to support cyclic and self-referencing data structures	56	number of extensions, to support cyclic and shared data structures
61	(see C<allow_sharing>), string deduplication (see C<pack_strings>) and	57	(see C<allow_sharing> and C<allow_cycles>), string deduplication (see
62	scalar references (always enabled).	58	C<pack_strings>) and scalar references (always enabled).
63
64	The primary goal of this module is to be I<correct> and the secondary goal
65	is to be I<fast>. To reach the latter goal it was written in C.
66		59
67	See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and	60	See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and
68	vice versa.	61	vice versa.
69		62
70	=cut	63	=cut
71		64
72	package CBOR::XS;	65	package CBOR::XS;
73		66
74	use common::sense;	67	use common::sense;
75		68
76	our $VERSION = 0.09;	69	our $VERSION = 1.82;
77	our @ISA = qw(Exporter);	70	our @ISA = qw(Exporter);
78		71
79	our @EXPORT = qw(encode_cbor decode_cbor);	72	our @EXPORT = qw(encode_cbor decode_cbor);
80		73
81	use Exporter;	74	use Exporter;
…		…
119		112
120	The mutators for flags all return the CBOR object again and thus calls can	113	The mutators for flags all return the CBOR object again and thus calls can
121	be chained:	114	be chained:
122		115
123	my $cbor = CBOR::XS->new->encode ({a => [1,2]});	116	my $cbor = CBOR::XS->new->encode ({a => [1,2]});
		117
		118	=item $cbor = new_safe CBOR::XS
		119
		120	Create a new, safe/secure CBOR::XS object. This is similar to C<new>,
		121	but configures the coder object to be safe to use with untrusted
		122	data. Currently, this is equivalent to:
		123
		124	my $cbor = CBOR::XS
		125	->new
		126	->forbid_objects
		127	->filter (\&CBOR::XS::safe_filter)
		128	->max_size (1e8);
		129
		130	But is more future proof (it is better to crash because of a change than
		131	to be exploited in other ways).
		132
		133	=cut
		134
		135	sub new_safe {
		136	CBOR::XS
		137	->new
		138	->forbid_objects
		139	->filter (\&CBOR::XS::safe_filter)
		140	->max_size (1e8)
		141	}
124		142
125	=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])	143	=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])
126		144
127	=item $max_depth = $cbor->get_max_depth	145	=item $max_depth = $cbor->get_max_depth
128		146
…		…
144		162
145	Note that nesting is implemented by recursion in C. The default value has	163	Note that nesting is implemented by recursion in C. The default value has
146	been chosen to be as large as typical operating systems allow without	164	been chosen to be as large as typical operating systems allow without
147	crashing.	165	crashing.
148		166
149	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	167	See L<SECURITY CONSIDERATIONS>, below, for more info on why this is useful.
150		168
151	=item $cbor = $cbor->max_size ([$maximum_string_size])	169	=item $cbor = $cbor->max_size ([$maximum_string_size])
152		170
153	=item $max_size = $cbor->get_max_size	171	=item $max_size = $cbor->get_max_size
154		172
…		…
159	effect on C<encode> (yet).	177	effect on C<encode> (yet).
160		178
161	If no argument is given, the limit check will be deactivated (same as when	179	If no argument is given, the limit check will be deactivated (same as when
162	C<0> is specified).	180	C<0> is specified).
163		181
164	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	182	See L<SECURITY CONSIDERATIONS>, below, for more info on why this is useful.
165		183
166	=item $cbor = $cbor->allow_unknown ([$enable])	184	=item $cbor = $cbor->allow_unknown ([$enable])
167		185
168	=item $enabled = $cbor->get_allow_unknown	186	=item $enabled = $cbor->get_allow_unknown
169		187
…		…
187	reference to the earlier value.	205	reference to the earlier value.
188		206
189	This means that such values will only be encoded once, and will not result	207	This means that such values will only be encoded once, and will not result
190	in a deep cloning of the value on decode, in decoders supporting the value	208	in a deep cloning of the value on decode, in decoders supporting the value
191	sharing extension. This also makes it possible to encode cyclic data	209	sharing extension. This also makes it possible to encode cyclic data
192	structures.	210	structures (which need C<allow_cycles> to be enabled to be decoded by this
		211	module).
193		212
194	It is recommended to leave it off unless you know your	213	It is recommended to leave it off unless you know your
195	communication partner supports the value sharing extensions to CBOR	214	communication partner supports the value sharing extensions to CBOR
196	(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the	215	(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the
197	resulting data structure might be unusable.	216	resulting data structure might be unusable.
198		217
199	Detecting shared values incurs a runtime overhead when values are encoded	218	Detecting shared values incurs a runtime overhead when values are encoded
200	that have a reference counter large than one, and might unnecessarily	219	that have a reference counter large than one, and might unnecessarily
201	increase the encoded size, as potentially shared values are encode as	220	increase the encoded size, as potentially shared values are encoded as
202	sharable whether or not they are actually shared.	221	shareable whether or not they are actually shared.
203		222
204	At the moment, only targets of references can be shared (e.g. scalars,	223	At the moment, only targets of references can be shared (e.g. scalars,
205	arrays or hashes pointed to by a reference). Weirder constructs, such as	224	arrays or hashes pointed to by a reference). Weirder constructs, such as
206	an array with multiple "copies" of the I<same> string, which are hard but	225	an array with multiple "copies" of the I<same> string, which are hard but
207	not impossible to create in Perl, are not supported (this is the same as	226	not impossible to create in Perl, are not supported (this is the same as
…		…
212	structures cannot be encoded in this mode.	231	structures cannot be encoded in this mode.
213		232
214	This option does not affect C<decode> in any way - shared values and	233	This option does not affect C<decode> in any way - shared values and
215	references will always be decoded properly if present.	234	references will always be decoded properly if present.
216		235
		236	=item $cbor = $cbor->allow_cycles ([$enable])
		237
		238	=item $enabled = $cbor->get_allow_cycles
		239
		240	If C<$enable> is true (or missing), then C<decode> will happily decode
		241	self-referential (cyclic) data structures. By default these will not be
		242	decoded, as they need manual cleanup to avoid memory leaks, so code that
		243	isn't prepared for this will not leak memory.
		244
		245	If C<$enable> is false (the default), then C<decode> will throw an error
		246	when it encounters a self-referential/cyclic data structure.
		247
		248	FUTURE DIRECTION: the motivation behind this option is to avoid I<real>
		249	cycles - future versions of this module might chose to decode cyclic data
		250	structures using weak references when this option is off, instead of
		251	throwing an error.
		252
		253	This option does not affect C<encode> in any way - shared values and
		254	references will always be encoded properly if present.
		255
		256	=item $cbor = $cbor->forbid_objects ([$enable])
		257
		258	=item $enabled = $cbor->get_forbid_objects
		259
		260	Disables the use of the object serialiser protocol.
		261
		262	If C<$enable> is true (or missing), then C<encode> will will throw an
		263	exception when it encounters perl objects that would be encoded using the
		264	perl-object tag (26). When C<decode> encounters such tags, it will fall
		265	back to the general filter/tagged logic as if this were an unknown tag (by
		266	default resulting in a C<CBOR::XC::Tagged> object).
		267
		268	If C<$enable> is false (the default), then C<encode> will use the
		269	L<Types::Serialiser> object serialisation protocol to serialise objects
		270	into perl-object tags, and C<decode> will do the same to decode such tags.
		271
		272	See L<SECURITY CONSIDERATIONS>, below, for more info on why forbidding this
		273	protocol can be useful.
		274
217	=item $cbor = $cbor->pack_strings ([$enable])	275	=item $cbor = $cbor->pack_strings ([$enable])
218		276
219	=item $enabled = $cbor->get_pack_strings	277	=item $enabled = $cbor->get_pack_strings
220		278
221	If C<$enable> is true (or missing), then C<encode> will try not to encode	279	If C<$enable> is true (or missing), then C<encode> will try not to encode
…		…
233	the standard CBOR way.	291	the standard CBOR way.
234		292
235	This option does not affect C<decode> in any way - string references will	293	This option does not affect C<decode> in any way - string references will
236	always be decoded properly if present.	294	always be decoded properly if present.
237		295
		296	=item $cbor = $cbor->text_keys ([$enable])
		297
		298	=item $enabled = $cbor->get_text_keys
		299
		300	If C<$enabled> is true (or missing), then C<encode> will encode all
		301	perl hash keys as CBOR text strings/UTF-8 string, upgrading them as needed.
		302
		303	If C<$enable> is false (the default), then C<encode> will encode hash keys
		304	normally - upgraded perl strings (strings internally encoded as UTF-8) as
		305	CBOR text strings, and downgraded perl strings as CBOR byte strings.
		306
		307	This option does not affect C<decode> in any way.
		308
		309	This option is useful for interoperability with CBOR decoders that don't
		310	treat byte strings as a form of text. It is especially useful as Perl
		311	gives very little control over hash keys.
		312
		313	Enabling this option can be slow, as all downgraded hash keys that are
		314	encoded need to be scanned and converted to UTF-8.
		315
		316	=item $cbor = $cbor->text_strings ([$enable])
		317
		318	=item $enabled = $cbor->get_text_strings
		319
		320	This option works similar to C<text_keys>, above, but works on all strings
		321	(including hash keys), so C<text_keys> has no further effect after
		322	enabling C<text_strings>.
		323
		324	If C<$enabled> is true (or missing), then C<encode> will encode all perl
		325	strings as CBOR text strings/UTF-8 strings, upgrading them as needed.
		326
		327	If C<$enable> is false (the default), then C<encode> will encode strings
		328	normally (but see C<text_keys>) - upgraded perl strings (strings
		329	internally encoded as UTF-8) as CBOR text strings, and downgraded perl
		330	strings as CBOR byte strings.
		331
		332	This option does not affect C<decode> in any way.
		333
		334	This option has similar advantages and disadvantages as C<text_keys>. In
		335	addition, this option effectively removes the ability to automatically
		336	encode byte strings, which might break some C<FREEZE> and C<TO_CBOR>
		337	methods that rely on this.
		338
		339	A workaround is to use explicit type casts, which are unaffected by this option.
		340
		341	=item $cbor = $cbor->validate_utf8 ([$enable])
		342
		343	=item $enabled = $cbor->get_validate_utf8
		344
		345	If C<$enable> is true (or missing), then C<decode> will validate that
		346	elements (text strings) containing UTF-8 data in fact contain valid UTF-8
		347	data (instead of blindly accepting it). This validation obviously takes
		348	extra time during decoding.
		349
		350	The concept of "valid UTF-8" used is perl's concept, which is a superset
		351	of the official UTF-8.
		352
		353	If C<$enable> is false (the default), then C<decode> will blindly accept
		354	UTF-8 data, marking them as valid UTF-8 in the resulting data structure
		355	regardless of whether that's true or not.
		356
		357	Perl isn't too happy about corrupted UTF-8 in strings, but should
		358	generally not crash or do similarly evil things. Extensions might be not
		359	so forgiving, so it's recommended to turn on this setting if you receive
		360	untrusted CBOR.
		361
		362	This option does not affect C<encode> in any way - strings that are
		363	supposedly valid UTF-8 will simply be dumped into the resulting CBOR
		364	string without checking whether that is, in fact, true or not.
		365
238	=item $cbor = $cbor->filter ([$cb->($tag, $value)])	366	=item $cbor = $cbor->filter ([$cb->($tag, $value)])
239		367
240	=item $cb_or_undef = $cbor->get_filter	368	=item $cb_or_undef = $cbor->get_filter
241		369
242	Sets or replaces the tagged value decoding filter (when C<$cb> is	370	Sets or replaces the tagged value decoding filter (when C<$cb> is
…		…
254	replace the tagged value in the decoded data structure, or no values,	382	replace the tagged value in the decoded data structure, or no values,
255	which will result in default handling, which currently means the decoder	383	which will result in default handling, which currently means the decoder
256	creates a C<CBOR::XS::Tagged> object to hold the tag and the value.	384	creates a C<CBOR::XS::Tagged> object to hold the tag and the value.
257		385
258	When the filter is cleared (the default state), the default filter	386	When the filter is cleared (the default state), the default filter
259	function, C<CBOR::XS::default_filter>, is used. This function simply looks	387	function, C<CBOR::XS::default_filter>, is used. This function simply
260	up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be	388	looks up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists
261	a code reference that is called with tag and value, and is responsible for	389	it must be a code reference that is called with tag and value, and is
262	decoding the value. If no entry exists, it returns no values.	390	responsible for decoding the value. If no entry exists, it returns no
		391	values. C<CBOR::XS> provides a number of default filter functions already,
		392	the the C<%CBOR::XS::FILTER> hash can be freely extended with more.
263		393
		394	C<CBOR::XS> additionally provides an alternative filter function that is
		395	supposed to be safe to use with untrusted data (which the default filter
		396	might not), called C<CBOR::XS::safe_filter>, which works the same as
		397	the C<default_filter> but uses the C<%CBOR::XS::SAFE_FILTER> variable
		398	instead. It is prepopulated with the tag decoding functions that are
		399	deemed safe (basically the same as C<%CBOR::XS::FILTER> without all
		400	the bignum tags), and can be extended by user code as wlel, although,
		401	obviously, one should be very careful about adding decoding functions
		402	here, since the expectation is that they are safe to use on untrusted
		403	data, after all.
		404
264	Example: decode all tags not handled internally into CBOR::XS::Tagged	405	Example: decode all tags not handled internally into C<CBOR::XS::Tagged>
265	objects, with no other special handling (useful when working with	406	objects, with no other special handling (useful when working with
266	potentially "unsafe" CBOR data).	407	potentially "unsafe" CBOR data).
267		408
268	CBOR::XS->new->filter (sub { })->decode ($cbor_data);	409	CBOR::XS->new->filter (sub { })->decode ($cbor_data);
269		410
…		…
273	$CBOR::XS::FILTER{1347375694} = sub {	414	$CBOR::XS::FILTER{1347375694} = sub {
274	my ($tag, $value);	415	my ($tag, $value);
275		416
276	"tag 1347375694 value $value"	417	"tag 1347375694 value $value"
277	};	418	};
		419
		420	Example: provide your own filter function that looks up tags in your own
		421	hash:
		422
		423	my %my_filter = (
		424	998347484 => sub {
		425	my ($tag, $value);
		426
		427	"tag 998347484 value $value"
		428	};
		429	);
		430
		431	my $coder = CBOR::XS->new->filter (sub {
		432	&{ $my_filter{$_[0]} or return }
		433	});
		434
		435
		436	Example: use the safe filter function (see L<SECURITY CONSIDERATIONS> for
		437	more considerations on security).
		438
		439	CBOR::XS->new->filter (\&CBOR::XS::safe_filter)->decode ($cbor_data);
278		440
279	=item $cbor_data = $cbor->encode ($perl_scalar)	441	=item $cbor_data = $cbor->encode ($perl_scalar)
280		442
281	Converts the given Perl data structure (a scalar value) to its CBOR	443	Converts the given Perl data structure (a scalar value) to its CBOR
282	representation.	444	representation.
…		…
292	when there is trailing garbage after the CBOR string, it will silently	454	when there is trailing garbage after the CBOR string, it will silently
293	stop parsing there and return the number of characters consumed so far.	455	stop parsing there and return the number of characters consumed so far.
294		456
295	This is useful if your CBOR texts are not delimited by an outer protocol	457	This is useful if your CBOR texts are not delimited by an outer protocol
296	and you need to know where the first CBOR string ends amd the next one	458	and you need to know where the first CBOR string ends amd the next one
297	starts.	459	starts - CBOR strings are self-delimited, so it is possible to concatenate
		460	CBOR strings without any delimiters or size fields and recover their data.
298		461
299	CBOR::XS->new->decode_prefix ("......")	462	CBOR::XS->new->decode_prefix ("......")
300	=> ("...", 3)	463	=> ("...", 3)
		464
		465	=back
		466
		467	=head2 INCREMENTAL PARSING
		468
		469	In some cases, there is the need for incremental parsing of JSON
		470	texts. While this module always has to keep both CBOR text and resulting
		471	Perl data structure in memory at one time, it does allow you to parse a
		472	CBOR stream incrementally, using a similar to using "decode_prefix" to see
		473	if a full CBOR object is available, but is much more efficient.
		474
		475	It basically works by parsing as much of a CBOR string as possible - if
		476	the CBOR data is not complete yet, the pasrer will remember where it was,
		477	to be able to restart when more data has been accumulated. Once enough
		478	data is available to either decode a complete CBOR value or raise an
		479	error, a real decode will be attempted.
		480
		481	A typical use case would be a network protocol that consists of sending
		482	and receiving CBOR-encoded messages. The solution that works with CBOR and
		483	about anything else is by prepending a length to every CBOR value, so the
		484	receiver knows how many octets to read. More compact (and slightly slower)
		485	would be to just send CBOR values back-to-back, as C<CBOR::XS> knows where
		486	a CBOR value ends, and doesn't need an explicit length.
		487
		488	The following methods help with this:
		489
		490	=over 4
		491
		492	=item @decoded = $cbor->incr_parse ($buffer)
		493
		494	This method attempts to decode exactly one CBOR value from the beginning
		495	of the given C<$buffer>. The value is removed from the C<$buffer> on
		496	success. When C<$buffer> doesn't contain a complete value yet, it returns
		497	nothing. Finally, when the C<$buffer> doesn't start with something
		498	that could ever be a valid CBOR value, it raises an exception, just as
		499	C<decode> would. In the latter case the decoder state is undefined and
		500	must be reset before being able to parse further.
		501
		502	This method modifies the C<$buffer> in place. When no CBOR value can be
		503	decoded, the decoder stores the current string offset. On the next call,
		504	continues decoding at the place where it stopped before. For this to make
		505	sense, the C<$buffer> must begin with the same octets as on previous
		506	unsuccessful calls.
		507
		508	You can call this method in scalar context, in which case it either
		509	returns a decoded value or C<undef>. This makes it impossible to
		510	distinguish between CBOR null values (which decode to C<undef>) and an
		511	unsuccessful decode, which is often acceptable.
		512
		513	=item @decoded = $cbor->incr_parse_multiple ($buffer)
		514
		515	Same as C<incr_parse>, but attempts to decode as many CBOR values as
		516	possible in one go, instead of at most one. Calls to C<incr_parse> and
		517	C<incr_parse_multiple> can be interleaved.
		518
		519	=item $cbor->incr_reset
		520
		521	Resets the incremental decoder. This throws away any saved state, so that
		522	subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse
		523	a new CBOR value from the beginning of the C<$buffer> again.
		524
		525	This method can be called at any time, but it I<must> be called if you want
		526	to change your C<$buffer> or there was a decoding error and you want to
		527	reuse the C<$cbor> object for future incremental parsings.
301		528
302	=back	529	=back
303		530
304		531
305	=head1 MAPPING	532	=head1 MAPPING
…		…
356	=item tagged values	583	=item tagged values
357		584
358	Tagged items consists of a numeric tag and another CBOR value.	585	Tagged items consists of a numeric tag and another CBOR value.
359		586
360	See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>	587	See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>
361	for details.	588	for details on which tags are handled how.
362		589
363	=item anything else	590	=item anything else
364		591
365	Anything else (e.g. unsupported simple values) will raise a decoding	592	Anything else (e.g. unsupported simple values) will raise a decoding
366	error.	593	error.
…		…
369		596
370		597
371	=head2 PERL -> CBOR	598	=head2 PERL -> CBOR
372		599
373	The mapping from Perl to CBOR is slightly more difficult, as Perl is a	600	The mapping from Perl to CBOR is slightly more difficult, as Perl is a
374	truly typeless language, so we can only guess which CBOR type is meant by	601	typeless language. That means this module can only guess which CBOR type
375	a Perl value.	602	is meant by a perl value.
376		603
377	=over 4	604	=over 4
378		605
379	=item hash references	606	=item hash references
380		607
381	Perl hash references become CBOR maps. As there is no inherent ordering in	608	Perl hash references become CBOR maps. As there is no inherent ordering in
382	hash keys (or CBOR maps), they will usually be encoded in a pseudo-random	609	hash keys (or CBOR maps), they will usually be encoded in a pseudo-random
383	order.	610	order. This order can be different each time a hash is encoded.
384		611
385	Currently, tied hashes will use the indefinite-length format, while normal	612	Currently, tied hashes will use the indefinite-length format, while normal
386	hashes will use the fixed-length format.	613	hashes will use the fixed-length format.
387		614
388	=item array references	615	=item array references
389		616
390	Perl array references become fixed-length CBOR arrays.	617	Perl array references become fixed-length CBOR arrays.
391		618
392	=item other references	619	=item other references
393		620
394	Other unblessed references are generally not allowed and will cause an	621	Other unblessed references will be represented using
395	exception to be thrown, except for references to the integers C<0> and	622	the indirection tag extension (tag value C<22098>,
396	C<1>, which get turned into false and true in CBOR.	623	L<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed
		624	to be able to decode these values somehow, by either "doing the right
		625	thing", decoding into a generic tagged object, simply ignoring the tag, or
		626	something else.
397		627
398	=item CBOR::XS::Tagged objects	628	=item CBOR::XS::Tagged objects
399		629
400	Objects of this type must be arrays consisting of a single C<[tag, value]>	630	Objects of this type must be arrays consisting of a single C<[tag, value]>
401	pair. The (numerical) tag will be encoded as a CBOR tag, the value will	631	pair. The (numerical) tag will be encoded as a CBOR tag, the value will
402	be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to	632	be encoded as appropriate for the value. You must use C<CBOR::XS::tag> to
403	create such objects.	633	create such objects.
404		634
405	=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error	635	=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error
406		636
407	These special values become CBOR true, CBOR false and CBOR undefined	637	These special values become CBOR true, CBOR false and CBOR undefined
…		…
438	my $x = 3.1; # some variable containing a number	668	my $x = 3.1; # some variable containing a number
439	"$x"; # stringified	669	"$x"; # stringified
440	$x .= ""; # another, more awkward way to stringify	670	$x .= ""; # another, more awkward way to stringify
441	print $x; # perl does it for you, too, quite often	671	print $x; # perl does it for you, too, quite often
442		672
443	You can force whether a string ie encoded as byte or text string by using	673	You can force whether a string is encoded as byte or text string by using
444	C<utf8::upgrade> and C<utf8::downgrade>):	674	C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled).
445		675
446	utf8::upgrade $x; # encode $x as text string	676	utf8::upgrade $x; # encode $x as text string
447	utf8::downgrade $x; # encode $x as byte string	677	utf8::downgrade $x; # encode $x as byte string
448		678
		679	More options are available, see L<TYPE CASTS>, below, and the C<text_keys>
		680	and C<text_strings> options.
		681
449	Perl doesn't define what operations up- and downgrade strings, so if the	682	Perl doesn't define what operations up- and downgrade strings, so if the
450	difference between byte and text is important, you should up- or downgrade	683	difference between byte and text is important, you should up- or downgrade
451	your string as late as possible before encoding.	684	your string as late as possible before encoding. You can also force the
		685	use of CBOR text strings by using C<text_keys> or C<text_strings>.
452		686
453	You can force the type to be a CBOR number by numifying it:	687	You can force the type to be a CBOR number by numifying it:
454		688
455	my $x = "3"; # some variable containing a string	689	my $x = "3"; # some variable containing a string
456	$x += 0; # numify it, ensuring it will be dumped as a number	690	$x += 0; # numify it, ensuring it will be dumped as a number
…		…
467	represent numerical values are supported, but might suffer loss of	701	represent numerical values are supported, but might suffer loss of
468	precision.	702	precision.
469		703
470	=back	704	=back
471		705
		706	=head2 TYPE CASTS
		707
		708	B<EXPERIMENTAL>: As an experimental extension, C<CBOR::XS> allows you to
		709	force specific cbor types to be used when encoding. That allows you to
		710	encode types not normally accessible (e.g. half floats) as well as force
		711	string types even when C<text_strings> is in effect.
		712
		713	Type forcing is done by calling a special "cast" function which keeps a
		714	copy of the value and returns a new value that can be handed over to any
		715	CBOR encoder function.
		716
		717	The following casts are currently available (all of which are unary operators):
		718
		719	=over
		720
		721	=item CBOR::XS::as_int $value
		722
		723	Forces the value to be encoded as some form of (basic, not bignum) integer
		724	type.
		725
		726	=item CBOR::XS::as_text $value
		727
		728	Forces the value to be encoded as (UTF-8) text values.
		729
		730	=item CBOR::XS::as_bytes $value
		731
		732	Forces the value to be encoded as a (binary) string value.
		733
		734	Example: encode a perl string as binary even though C<text_strings> is in
		735	effect.
		736
		737	CBOR::XS->new->text_strings->encode ([4, "text", CBOR::XS::bytes "bytevalue"]);
		738
		739	=item CBOR::XS::as_bool $value
		740
		741	Converts a Perl boolean (which can be any kind of scalar) into a CBOR
		742	boolean. Strictly the same, but shorter to write, than:
		743
		744	$value ? Types::Serialiser::true : Types::Serialiser::false
		745
		746	=item CBOR::XS::as_float16 $value
		747
		748	Forces half-float (IEEE 754 binary16) encoding of the given value.
		749
		750	=item CBOR::XS::as_float32 $value
		751
		752	Forces single-float (IEEE 754 binary32) encoding of the given value.
		753
		754	=item CBOR::XS::as_float64 $value
		755
		756	Forces double-float (IEEE 754 binary64) encoding of the given value.
		757
		758	=item CBOR::XS::as_cbor $cbor_text
		759
		760	Not a type cast per-se, this type cast forces the argument to eb encoded
		761	as-is. This can be used to embed pre-encoded CBOR data.
		762
		763	Note that no checking on the validity of the C<$cbor_text> is done - it's
		764	the callers responsibility to correctly encode values.
		765
		766	=item CBOR::XS::as_map [key => value...]
		767
		768	Treat the array reference as key value pairs and output a CBOR map. This
		769	allows you to generate CBOR maps with arbitrary key types (or, if you
		770	don't care about semantics, duplicate keys or prairs in a custom order),
		771	which is otherwise hard to do with Perl.
		772
		773	The single argument must be an array reference with an even number of
		774	elements.
		775
		776	Example: encode a CBOR map with a string and an integer as keys.
		777
		778	encode_cbor CBOR::XS::as_map [string => "value", 5 => "value"]
		779
		780	=back
		781
		782	=cut
		783
		784	sub CBOR::XS::as_cbor ($) { bless [$_[0], 0, undef], CBOR::XS::Tagged:: }
		785	sub CBOR::XS::as_int ($) { bless [$_[0], 1, undef], CBOR::XS::Tagged:: }
		786	sub CBOR::XS::as_bytes ($) { bless [$_[0], 2, undef], CBOR::XS::Tagged:: }
		787	sub CBOR::XS::as_text ($) { bless [$_[0], 3, undef], CBOR::XS::Tagged:: }
		788	sub CBOR::XS::as_float16 ($) { bless [$_[0], 4, undef], CBOR::XS::Tagged:: }
		789	sub CBOR::XS::as_float32 ($) { bless [$_[0], 5, undef], CBOR::XS::Tagged:: }
		790	sub CBOR::XS::as_float64 ($) { bless [$_[0], 6, undef], CBOR::XS::Tagged:: }
		791
		792	sub CBOR::XS::as_bool ($) { $_[0] ? $Types::Serialiser::true : $Types::Serialiser::false }
		793
		794	sub CBOR::XS::as_map ($) {
		795	ARRAY:: eq ref $_[0]
		796	and $#{ $_[0] } & 1
		797	or do { require Carp; Carp::croak ("CBOR::XS::as_map only acepts array references with an even number of elements, found ") };
		798
		799	bless [$_[0], 7, undef], CBOR::XS::Tagged::
		800	}
		801
472	=head2 OBJECT SERIALISATION	802	=head2 OBJECT SERIALISATION
		803
		804	This module implements both a CBOR-specific and the generic
		805	L<Types::Serialier> object serialisation protocol. The following
		806	subsections explain both methods.
		807
		808	=head3 ENCODING
473		809
474	This module knows two way to serialise a Perl object: The CBOR-specific	810	This module knows two way to serialise a Perl object: The CBOR-specific
475	way, and the generic way.	811	way, and the generic way.
476		812
477	Whenever the encoder encounters a Perl object that it cnanot serialise	813	Whenever the encoder encounters a Perl object that it cannot serialise
478	directly (most of them), it will first look up the C<TO_CBOR> method on	814	directly (most of them), it will first look up the C<TO_CBOR> method on
479	it.	815	it.
480		816
481	If it has a C<TO_CBOR> method, it will call it with the object as only	817	If it has a C<TO_CBOR> method, it will call it with the object as only
482	argument, and expects exactly one return value, which it will then	818	argument, and expects exactly one return value, which it will then
…		…
488		824
489	The C<FREEZE> method can return any number of values (i.e. zero or	825	The C<FREEZE> method can return any number of values (i.e. zero or
490	more). These will be encoded as CBOR perl object, together with the	826	more). These will be encoded as CBOR perl object, together with the
491	classname.	827	classname.
492		828
		829	These methods I<MUST NOT> change the data structure that is being
		830	serialised. Failure to comply to this can result in memory corruption -
		831	and worse.
		832
493	If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail	833	If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail
494	with an error.	834	with an error.
495		835
		836	=head3 DECODING
		837
496	Objects encoded via C<TO_CBOR> cannot be automatically decoded, but	838	Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded,
497	objects encoded via C<FREEZE> can be decoded using the following protocol:	839	but objects encoded via C<FREEZE> can be decoded using the following
		840	protocol:
498		841
499	When an encoded CBOR perl object is encountered by the decoder, it will	842	When an encoded CBOR perl object is encountered by the decoder, it will
500	look up the C<THAW> method, by using the stored classname, and will fail	843	look up the C<THAW> method, by using the stored classname, and will fail
501	if the method cannot be found.	844	if the method cannot be found.
502		845
503	After the lookup it will call the C<THAW> method with the stored classname	846	After the lookup it will call the C<THAW> method with the stored classname
504	as first argument, the constant string C<CBOR> as second argument, and all	847	as first argument, the constant string C<CBOR> as second argument, and all
505	values returned by C<FREEZE> as remaining arguments.	848	values returned by C<FREEZE> as remaining arguments.
506		849
507	=head4 EXAMPLES	850	=head3 EXAMPLES
508		851
509	Here is an example C<TO_CBOR> method:	852	Here is an example C<TO_CBOR> method:
510		853
511	sub My::Object::TO_CBOR {	854	sub My::Object::TO_CBOR {
512	my ($obj) = @_;	855	my ($obj) = @_;
…		…
523		866
524	sub URI::TO_CBOR {	867	sub URI::TO_CBOR {
525	my ($self) = @_;	868	my ($self) = @_;
526	my $uri = "$self"; # stringify uri	869	my $uri = "$self"; # stringify uri
527	utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string	870	utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string
528	CBOR::XS::tagged 32, "$_[0]"	871	CBOR::XS::tag 32, "$_[0]"
529	}	872	}
530		873
531	This will encode URIs as a UTF-8 string with tag 32, which indicates an	874	This will encode URIs as a UTF-8 string with tag 32, which indicates an
532	URI.	875	URI.
533		876
…		…
544	"$self" # encode url string	887	"$self" # encode url string
545	}	888	}
546		889
547	sub URI::THAW {	890	sub URI::THAW {
548	my ($class, $serialiser, $uri) = @_;	891	my ($class, $serialiser, $uri) = @_;
549
550	$class->new ($uri)	892	$class->new ($uri)
551	}	893	}
552		894
553	Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For	895	Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For
554	example, a C<FREEZE> method that returns "type", "id" and "variant" values	896	example, a C<FREEZE> method that returns "type", "id" and "variant" values
…		…
685	additional tags (such as base64url).	1027	additional tags (such as base64url).
686		1028
687	=head2 ENFORCED TAGS	1029	=head2 ENFORCED TAGS
688		1030
689	These tags are always handled when decoding, and their handling cannot be	1031	These tags are always handled when decoding, and their handling cannot be
690	overriden by the user.	1032	overridden by the user.
691		1033
692	=over 4	1034	=over 4
693		1035
694	=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>)	1036	=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>)
695		1037
696	These tags are automatically created (and decoded) for serialisable	1038	These tags are automatically created (and decoded) for serialisable
697	objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object	1039	objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object
698	serialisation protocol). See L<OBJECT SERIALISATION> for details.	1040	serialisation protocol). See L<OBJECT SERIALISATION> for details.
699		1041
700	=item 28, 29 (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>)	1042	=item 28, 29 (shareable, sharedref, L<http://cbor.schmorp.de/value-sharing>)
701		1043
702	These tags are automatically decoded when encountered, resulting in	1044	These tags are automatically decoded when encountered (and they do not
		1045	result in a cyclic data structure, see C<allow_cycles>), resulting in
703	shared values in the decoded object. They are only encoded, however, when	1046	shared values in the decoded object. They are only encoded, however, when
704	C<allow_sharable> is enabled.	1047	C<allow_sharing> is enabled.
705		1048
		1049	Not all shared values can be successfully decoded: values that reference
		1050	themselves will I<currently> decode as C<undef> (this is not the same
		1051	as a reference pointing to itself, which will be represented as a value
		1052	that contains an indirect reference to itself - these will be decoded
		1053	properly).
		1054
		1055	Note that considerably more shared value data structures can be decoded
		1056	than will be encoded - currently, only values pointed to by references
		1057	will be shared, others will not. While non-reference shared values can be
		1058	generated in Perl with some effort, they were considered too unimportant
		1059	to be supported in the encoder. The decoder, however, will decode these
		1060	values as shared values.
		1061
706	=item 256, 25 (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>)	1062	=item 256, 25 (stringref-namespace, stringref, L<http://cbor.schmorp.de/stringref>)
707		1063
708	These tags are automatically decoded when encountered. They are only	1064	These tags are automatically decoded when encountered. They are only
709	encoded, however, when C<pack_strings> is enabled.	1065	encoded, however, when C<pack_strings> is enabled.
710		1066
711	=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)	1067	=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
712		1068
713	This tag is automatically generated when a reference are encountered (with	1069	This tag is automatically generated when a reference are encountered (with
714	the exception of hash and array refernces). It is converted to a reference	1070	the exception of hash and array references). It is converted to a reference
715	when decoding.	1071	when decoding.
716		1072
717	=item 55799 (self-describe CBOR, RFC 7049)	1073	=item 55799 (self-describe CBOR, RFC 7049)
718		1074
719	This value is not generated on encoding (unless explicitly requested by	1075	This value is not generated on encoding (unless explicitly requested by
…		…
722	=back	1078	=back
723		1079
724	=head2 NON-ENFORCED TAGS	1080	=head2 NON-ENFORCED TAGS
725		1081
726	These tags have default filters provided when decoding. Their handling can	1082	These tags have default filters provided when decoding. Their handling can
727	be overriden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by	1083	be overridden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by
728	providing a custom C<filter> callback when decoding.	1084	providing a custom C<filter> callback when decoding.
729		1085
730	When they result in decoding into a specific Perl class, the module	1086	When they result in decoding into a specific Perl class, the module
731	usually provides a corresponding C<TO_CBOR> method as well.	1087	usually provides a corresponding C<TO_CBOR> method as well.
732		1088
…		…
735	provide these modules. The decoding usually fails with an exception if the	1091	provide these modules. The decoding usually fails with an exception if the
736	required module cannot be loaded.	1092	required module cannot be loaded.
737		1093
738	=over 4	1094	=over 4
739		1095
		1096	=item 0, 1 (date/time string, seconds since the epoch)
		1097
		1098	These tags are decoded into L<Time::Piece> objects. The corresponding
		1099	C<Time::Piece::TO_CBOR> method always encodes into tag 1 values currently.
		1100
		1101	The L<Time::Piece> API is generally surprisingly bad, and fractional
		1102	seconds are only accidentally kept intact, so watch out. On the plus side,
		1103	the module comes with perl since 5.10, which has to count for something.
		1104
740	=item 2, 3 (positive/negative bignum)	1105	=item 2, 3 (positive/negative bignum)
741		1106
742	These tags are decoded into L<Math::BigInt> objects. The corresponding	1107	These tags are decoded into L<Math::BigInt> objects. The corresponding
743	C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR	1108	C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR
744	integers, and others into positive/negative CBOR bignums.	1109	integers, and others into positive/negative CBOR bignums.
745		1110
746	=item 4, 5 (decimal fraction/bigfloat)	1111	=item 4, 5, 264, 265 (decimal fraction/bigfloat)
747		1112
748	Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>	1113	Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>
749	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>	1114	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>
750	encodes into a decimal fraction.	1115	encodes into a decimal fraction (either tag 4 or 264).
751		1116
752	CBOR cannot represent bigfloats with I<very> large exponents - conversion	1117	NaN and infinities are not encoded properly, as they cannot be represented
753	of such big float objects is undefined.	1118	in CBOR.
754		1119
755	Also, NaN and infinities are not encoded properly.	1120	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
		1121
		1122	=item 30 (rational numbers)
		1123
		1124	These tags are decoded into L<Math::BigRat> objects. The corresponding
		1125	C<Math::BigRat::TO_CBOR> method encodes rational numbers with denominator
		1126	C<1> via their numerator only, i.e., they become normal integers or
		1127	C<bignums>.
		1128
		1129	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
756		1130
757	=item 21, 22, 23 (expected later JSON conversion)	1131	=item 21, 22, 23 (expected later JSON conversion)
758		1132
759	CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these	1133	CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these
760	tags.	1134	tags.
…		…
765	C<URI::TO_CBOR> method again results in a CBOR URI value.	1139	C<URI::TO_CBOR> method again results in a CBOR URI value.
766		1140
767	=back	1141	=back
768		1142
769	=cut	1143	=cut
770
771	our %FILTER = (
772	# 0 # rfc4287 datetime, utf-8
773	# 1 # unix timestamp, any
774
775	2 => sub { # pos bigint
776	require Math::BigInt;
777	Math::BigInt->new ("0x" . unpack "H*", pop)
778	},
779
780	3 => sub { # neg bigint
781	require Math::BigInt;
782	-Math::BigInt->new ("0x" . unpack "H*", pop)
783	},
784
785	4 => sub { # decimal fraction, array
786	require Math::BigFloat;
787	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
788	},
789
790	5 => sub { # bigfloat, array
791	require Math::BigFloat;
792	scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2)
793	},
794
795	21 => sub { pop }, # expected conversion to base64url encoding
796	22 => sub { pop }, # expected conversion to base64 encoding
797	23 => sub { pop }, # expected conversion to base16 encoding
798
799	# 24 # embedded cbor, byte string
800
801	32 => sub {
802	require URI;
803	URI->new (pop)
804	},
805
806	# 33 # base64url rfc4648, utf-8
807	# 34 # base64 rfc46484, utf-8
808	# 35 # regex pcre/ecma262, utf-8
809	# 36 # mime message rfc2045, utf-8
810	);
811
812		1144
813	=head1 CBOR and JSON	1145	=head1 CBOR and JSON
814		1146
815	CBOR is supposed to implement a superset of the JSON data model, and is,	1147	CBOR is supposed to implement a superset of the JSON data model, and is,
816	with some coercion, able to represent all JSON texts (something that other	1148	with some coercion, able to represent all JSON texts (something that other
…		…
825	CBOR intact.	1157	CBOR intact.
826		1158
827		1159
828	=head1 SECURITY CONSIDERATIONS	1160	=head1 SECURITY CONSIDERATIONS
829		1161
830	When you are using CBOR in a protocol, talking to untrusted potentially	1162	Tl;dr... if you want to decode or encode CBOR from untrusted sources, you
831	hostile creatures requires relatively few measures.	1163	should start with a coder object created via C<new_safe> (which implements
		1164	the mitigations explained below):
832		1165
		1166	my $coder = CBOR::XS->new_safe;
		1167
		1168	my $data = $coder->decode ($cbor_text);
		1169	my $cbor = $coder->encode ($data);
		1170
		1171	Longer version: When you are using CBOR in a protocol, talking to
		1172	untrusted potentially hostile creatures requires some thought:
		1173
		1174	=over 4
		1175
		1176	=item Security of the CBOR decoder itself
		1177
833	First of all, your CBOR decoder should be secure, that is, should not have	1178	First and foremost, your CBOR decoder should be secure, that is, should
		1179	not have any buffer overflows or similar bugs that could potentially be
834	any buffer overflows. Obviously, this module should ensure that and I am	1180	exploited. Obviously, this module should ensure that and I am trying hard
835	trying hard on making that true, but you never know.	1181	on making that true, but you never know.
836		1182
		1183	=item CBOR::XS can invoke almost arbitrary callbacks during decoding
		1184
		1185	CBOR::XS supports object serialisation - decoding CBOR can cause calls
		1186	to I<any> C<THAW> method in I<any> package that exists in your process
		1187	(that is, CBOR::XS will not try to load modules, but any existing C<THAW>
		1188	method or function can be called, so they all have to be secure).
		1189
		1190	Less obviously, it will also invoke C<TO_CBOR> and C<FREEZE> methods -
		1191	even if all your C<THAW> methods are secure, encoding data structures from
		1192	untrusted sources can invoke those and trigger bugs in those.
		1193
		1194	So, if you are not sure about the security of all the modules you
		1195	have loaded (you shouldn't), you should disable this part using
		1196	C<forbid_objects> or using C<new_safe>.
		1197
		1198	=item CBOR can be extended with tags that call library code
		1199
		1200	CBOR can be extended with tags, and C<CBOR::XS> has a registry of
		1201	conversion functions for many existing tags that can be extended via
		1202	third-party modules (see the C<filter> method).
		1203
		1204	If you don't trust these, you should configure the "safe" filter function,
		1205	C<CBOR::XS::safe_filter> (C<new_safe> does this), which by default only
		1206	includes conversion functions that are considered "safe" by the author
		1207	(but again, they can be extended by third party modules).
		1208
		1209	Depending on your level of paranoia, you can use the "safe" filter:
		1210
		1211	$cbor->filter (\&CBOR::XS::safe_filter);
		1212
		1213	... your own filter...
		1214
		1215	$cbor->filter (sub { ... do your stuffs here ... });
		1216
		1217	... or even no filter at all, disabling all tag decoding:
		1218
		1219	$cbor->filter (sub { });
		1220
		1221	This is never a problem for encoding, as the tag mechanism only exists in
		1222	CBOR texts.
		1223
		1224	=item Resource-starving attacks: object memory usage
		1225
837	Second, you need to avoid resource-starving attacks. That means you should	1226	You need to avoid resource-starving attacks. That means you should limit
838	limit the size of CBOR data you accept, or make sure then when your	1227	the size of CBOR data you accept, or make sure then when your resources
839	resources run out, that's just fine (e.g. by using a separate process that	1228	run out, that's just fine (e.g. by using a separate process that can
840	can crash safely). The size of a CBOR string in octets is usually a good	1229	crash safely). The size of a CBOR string in octets is usually a good
841	indication of the size of the resources required to decode it into a Perl	1230	indication of the size of the resources required to decode it into a Perl
842	structure. While CBOR::XS can check the size of the CBOR text, it might be	1231	structure. While CBOR::XS can check the size of the CBOR text (using
843	too late when you already have it in memory, so you might want to check	1232	C<max_size> - done by C<new_safe>), it might be too late when you already
844	the size before you accept the string.	1233	have it in memory, so you might want to check the size before you accept
		1234	the string.
845		1235
		1236	As for encoding, it is possible to construct data structures that are
		1237	relatively small but result in large CBOR texts (for example by having an
		1238	array full of references to the same big data structure, which will all be
		1239	deep-cloned during encoding by default). This is rarely an actual issue
		1240	(and the worst case is still just running out of memory), but you can
		1241	reduce this risk by using C<allow_sharing>.
		1242
		1243	=item Resource-starving attacks: stack overflows
		1244
846	Third, CBOR::XS recurses using the C stack when decoding objects and	1245	CBOR::XS recurses using the C stack when decoding objects and arrays. The
847	arrays. The C stack is a limited resource: for instance, on my amd64	1246	C stack is a limited resource: for instance, on my amd64 machine with 8MB
848	machine with 8MB of stack size I can decode around 180k nested arrays but	1247	of stack size I can decode around 180k nested arrays but only 14k nested
849	only 14k nested CBOR objects (due to perl itself recursing deeply on croak	1248	CBOR objects (due to perl itself recursing deeply on croak to free the
850	to free the temporary). If that is exceeded, the program crashes. To be	1249	temporary). If that is exceeded, the program crashes. To be conservative,
851	conservative, the default nesting limit is set to 512. If your process	1250	the default nesting limit is set to 512. If your process has a smaller
852	has a smaller stack, you should adjust this setting accordingly with the	1251	stack, you should adjust this setting accordingly with the C<max_depth>
853	C<max_depth> method.	1252	method.
		1253
		1254	=item Resource-starving attacks: CPU en-/decoding complexity
		1255
		1256	CBOR::XS will use the L<Math::BigInt>, L<Math::BigFloat> and
		1257	L<Math::BigRat> libraries to represent encode/decode bignums. These can be
		1258	very slow (as in, centuries of CPU time) and can even crash your program
		1259	(and are generally not very trustworthy). See the next section on bignum
		1260	security for details.
		1261
		1262	=item Data breaches: leaking information in error messages
		1263
		1264	CBOR::XS might leak contents of your Perl data structures in its error
		1265	messages, so when you serialise sensitive information you might want to
		1266	make sure that exceptions thrown by CBOR::XS will not end up in front of
		1267	untrusted eyes.
		1268
		1269	=item Something else...
854		1270
855	Something else could bomb you, too, that I forgot to think of. In that	1271	Something else could bomb you, too, that I forgot to think of. In that
856	case, you get to keep the pieces. I am always open for hints, though...	1272	case, you get to keep the pieces. I am always open for hints, though...
857		1273
858	Also keep in mind that CBOR::XS might leak contents of your Perl data	1274	=back
859	structures in its error messages, so when you serialise sensitive	1275
860	information you might want to make sure that exceptions thrown by CBOR::XS	1276
861	will not end up in front of untrusted eyes.	1277	=head1 BIGNUM SECURITY CONSIDERATIONS
		1278
		1279	CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and
		1280	L<Math::BigFloat> that tries to encode the number in the simplest possible
		1281	way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
		1282	4) or an arbitrary-exponent decimal fraction (tag 264). Rational numbers
		1283	(L<Math::BigRat>, tag 30) can also contain bignums as members.
		1284
		1285	CBOR::XS will also understand base-2 bigfloat or arbitrary-exponent
		1286	bigfloats (tags 5 and 265), but it will never generate these on its own.
		1287
		1288	Using the built-in L<Math::BigInt::Calc> support, encoding and decoding
		1289	decimal fractions is generally fast. Decoding bigints can be slow for very
		1290	big numbers (tens of thousands of digits, something that could potentially
		1291	be caught by limiting the size of CBOR texts), and decoding bigfloats or
		1292	arbitrary-exponent bigfloats can be I<extremely> slow (minutes, decades)
		1293	for large exponents (roughly 40 bit and longer).
		1294
		1295	Additionally, L<Math::BigInt> can take advantage of other bignum
		1296	libraries, such as L<Math::GMP>, which cannot handle big floats with large
		1297	exponents, and might simply abort or crash your program, due to their code
		1298	quality.
		1299
		1300	This can be a concern if you want to parse untrusted CBOR. If it is, you
		1301	might want to disable decoding of tag 2 (bigint) and 3 (negative bigint)
		1302	types. You should also disable types 5 and 265, as these can be slow even
		1303	without bigints.
		1304
		1305	Disabling bigints will also partially or fully disable types that rely on
		1306	them, e.g. rational numbers that use bignums.
		1307
862		1308
863	=head1 CBOR IMPLEMENTATION NOTES	1309	=head1 CBOR IMPLEMENTATION NOTES
864		1310
865	This section contains some random implementation notes. They do not	1311	This section contains some random implementation notes. They do not
866	describe guaranteed behaviour, but merely behaviour as-is implemented	1312	describe guaranteed behaviour, but merely behaviour as-is implemented
…		…
875	Only the double data type is supported for NV data types - when Perl uses	1321	Only the double data type is supported for NV data types - when Perl uses
876	long double to represent floating point values, they might not be encoded	1322	long double to represent floating point values, they might not be encoded
877	properly. Half precision types are accepted, but not encoded.	1323	properly. Half precision types are accepted, but not encoded.
878		1324
879	Strict mode and canonical mode are not implemented.	1325	Strict mode and canonical mode are not implemented.
		1326
		1327
		1328	=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
		1329
		1330	On perls that were built without 64 bit integer support (these are rare
		1331	nowadays, even on 32 bit architectures, as all major Perl distributions
		1332	are built with 64 bit integer support), support for any kind of 64 bit
		1333	value in CBOR is very limited - most likely, these 64 bit values will
		1334	be truncated, corrupted, or otherwise not decoded correctly. This also
		1335	includes string, float, array and map sizes that are stored as 64 bit
		1336	integers.
880		1337
881		1338
882	=head1 THREADS	1339	=head1 THREADS
883		1340
884	This module is I<not> guaranteed to be thread safe and there are no	1341	This module is I<not> guaranteed to be thread safe and there are no
…		…
898	Please refrain from using rt.cpan.org or any other bug reporting	1355	Please refrain from using rt.cpan.org or any other bug reporting
899	service. I put the contact address into my modules for a reason.	1356	service. I put the contact address into my modules for a reason.
900		1357
901	=cut	1358	=cut
902		1359
		1360	# clumsy and slow hv_store-in-hash helper function
		1361	sub _hv_store {
		1362	$_[0]{$_[1]} = $_[2];
		1363	}
		1364
903	our %FILTER = (	1365	our %FILTER = (
904	# 0 # rfc4287 datetime, utf-8	1366	0 => sub { # rfc4287 datetime, utf-8
905	# 1 # unix timestamp, any	1367	require Time::Piece;
		1368	# Time::Piece::Strptime uses the "incredibly flexible date parsing routine"
		1369	# from FreeBSD, which can't parse ISO 8601, RFC3339, RFC4287 or much of anything
		1370	# else either. Whats incredibe over standard strptime totally escapes me.
		1371	# doesn't do fractional times, either. sigh.
		1372	# In fact, it's all a lie, it uses whatever strptime it wants, and of course,
		1373	# they are all incompatible. The openbsd one simply ignores %z (but according to the
		1374	# docs, it would be much more incredibly flexible indeed. If it worked, that is.).
		1375	scalar eval {
		1376	my $s = $_[1];
		1377
		1378	$s =~ s/Z$/+00:00/;
		1379	$s =~ s/(\.[0-9]+)?([+-][0-9][0-9]):([0-9][0-9])$//
		1380	or die;
		1381
		1382	my $b = $1 - ($2 * 60 + $3) * 60; # fractional part + offset. hopefully
		1383	my $d = Time::Piece->strptime ($s, "%Y-%m-%dT%H:%M:%S");
		1384
		1385	Time::Piece::gmtime ($d->epoch + $b)
		1386	} \|\| die "corrupted CBOR date/time string ($_[0])";
		1387	},
		1388
		1389	1 => sub { # seconds since the epoch, possibly fractional
		1390	require Time::Piece;
		1391	scalar Time::Piece::gmtime (pop)
		1392	},
906		1393
907	2 => sub { # pos bigint	1394	2 => sub { # pos bigint
908	require Math::BigInt;	1395	require Math::BigInt;
909	Math::BigInt->new ("0x" . unpack "H*", pop)	1396	Math::BigInt->new ("0x" . unpack "H*", pop)
910	},	1397	},
…		…
917	4 => sub { # decimal fraction, array	1404	4 => sub { # decimal fraction, array
918	require Math::BigFloat;	1405	require Math::BigFloat;
919	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])	1406	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
920	},	1407	},
921		1408
		1409	264 => sub { # decimal fraction with arbitrary exponent
		1410	require Math::BigFloat;
		1411	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
		1412	},
		1413
922	5 => sub { # bigfloat, array	1414	5 => sub { # bigfloat, array
923	require Math::BigFloat;	1415	require Math::BigFloat;
924	scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2)	1416	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1417	},
		1418
		1419	265 => sub { # bigfloat with arbitrary exponent
		1420	require Math::BigFloat;
		1421	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1422	},
		1423
		1424	30 => sub { # rational number
		1425	require Math::BigRat;
		1426	Math::BigRat->new ("$_[1][0]/$_[1][1]") # separate parameters only work in recent versons
925	},	1427	},
926		1428
927	21 => sub { pop }, # expected conversion to base64url encoding	1429	21 => sub { pop }, # expected conversion to base64url encoding
928	22 => sub { pop }, # expected conversion to base64 encoding	1430	22 => sub { pop }, # expected conversion to base64 encoding
929	23 => sub { pop }, # expected conversion to base16 encoding	1431	23 => sub { pop }, # expected conversion to base16 encoding
…		…
939	# 34 # base64 rfc46484, utf-8	1441	# 34 # base64 rfc46484, utf-8
940	# 35 # regex pcre/ecma262, utf-8	1442	# 35 # regex pcre/ecma262, utf-8
941	# 36 # mime message rfc2045, utf-8	1443	# 36 # mime message rfc2045, utf-8
942	);	1444	);
943		1445
944	sub CBOR::XS::default_filter {	1446	sub default_filter {
945	&{ $FILTER{$_[0]} or return }	1447	&{ $FILTER{$_[0]} or return }
		1448	}
		1449
		1450	our %SAFE_FILTER = map { $_ => $FILTER{$_} } 0, 1, 21, 22, 23, 32;
		1451
		1452	sub safe_filter {
		1453	&{ $SAFE_FILTER{$_[0]} or return }
946	}	1454	}
947		1455
948	sub URI::TO_CBOR {	1456	sub URI::TO_CBOR {
949	my $uri = $_[0]->as_string;	1457	my $uri = $_[0]->as_string;
950	utf8::upgrade $uri;	1458	utf8::upgrade $uri;
951	CBOR::XS::tag 32, $uri	1459	tag 32, $uri
952	}	1460	}
953		1461
954	sub Math::BigInt::TO_CBOR {	1462	sub Math::BigInt::TO_CBOR {
955	if ($_[0] >= -2147483648 && $_[0] <= 2147483647) {	1463	if (-2147483648 <= $_[0] && $_[0] <= 2147483647) {
956	$_[0]->numify	1464	$_[0]->numify
957	} else {	1465	} else {
958	my $hex = substr $_[0]->as_hex, 2;	1466	my $hex = substr $_[0]->as_hex, 2;
959	$hex = "0$hex" if 1 & length $hex; # sigh	1467	$hex = "0$hex" if 1 & length $hex; # sigh
960	CBOR::XS::tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex	1468	tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
961	}	1469	}
962	}	1470	}
963		1471
964	sub Math::BigFloat::TO_CBOR {	1472	sub Math::BigFloat::TO_CBOR {
965	my ($m, $e) = $_[0]->parts;	1473	my ($m, $e) = $_[0]->parts;
		1474
		1475	-9223372036854775808 <= $e && $e <= 18446744073709551615
966	CBOR::XS::tag 4, [$e->numify, $m]	1476	? tag 4, [$e->numify, $m]
		1477	: tag 264, [$e, $m]
		1478	}
		1479
		1480	sub Math::BigRat::TO_CBOR {
		1481	my ($n, $d) = $_[0]->parts;
		1482
		1483	# older versions of BigRat need *1, as they not always return numbers
		1484
		1485	$d*1 == 1
		1486	? $n*1
		1487	: tag 30, [$n1, $d1]
		1488	}
		1489
		1490	sub Time::Piece::TO_CBOR {
		1491	tag 1, 0 + $_[0]->epoch
967	}	1492	}
968		1493
969	XSLoader::load "CBOR::XS", $VERSION;	1494	XSLoader::load "CBOR::XS", $VERSION;
970		1495
971	=head1 SEE ALSO	1496	=head1 SEE ALSO

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Comparing CBOR-XS/XS.pm (file contents): Revision 1.27 by root, Thu Nov 28 15:43:24 2013 UTC vs. Revision 1.77 by root, Fri Dec 4 02:57:14 2020 UTC

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Comparing CBOR-XS/XS.pm (file contents):
Revision 1.27 by root, Thu Nov 28 15:43:24 2013 UTC vs.
Revision 1.77 by root, Fri Dec 4 02:57:14 2020 UTC