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

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.24 by root, Fri Nov 22 16:18:59 2013 UTC vs.
Revision 1.82 by root, Sat May 8 07:08:12 2021 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<allow_stringref>) 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 = 1.83;
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	->validate_utf8
		127	->forbid_objects
		128	->filter (\&CBOR::XS::safe_filter)
		129	->max_size (1e8);
		130
		131	But is more future proof (it is better to crash because of a change than
		132	to be exploited in other ways).
		133
		134	=cut
		135
		136	sub new_safe {
		137	CBOR::XS
		138	->new
		139	->validate_utf8
		140	->forbid_objects
		141	->filter (\&CBOR::XS::safe_filter)
		142	->max_size (1e8)
		143	}
124		144
125	=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])	145	=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])
126		146
127	=item $max_depth = $cbor->get_max_depth	147	=item $max_depth = $cbor->get_max_depth
128		148
…		…
144		164
145	Note that nesting is implemented by recursion in C. The default value has	165	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	166	been chosen to be as large as typical operating systems allow without
147	crashing.	167	crashing.
148		168
149	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	169	See L<SECURITY CONSIDERATIONS>, below, for more info on why this is useful.
150		170
151	=item $cbor = $cbor->max_size ([$maximum_string_size])	171	=item $cbor = $cbor->max_size ([$maximum_string_size])
152		172
153	=item $max_size = $cbor->get_max_size	173	=item $max_size = $cbor->get_max_size
154		174
…		…
159	effect on C<encode> (yet).	179	effect on C<encode> (yet).
160		180
161	If no argument is given, the limit check will be deactivated (same as when	181	If no argument is given, the limit check will be deactivated (same as when
162	C<0> is specified).	182	C<0> is specified).
163		183
164	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	184	See L<SECURITY CONSIDERATIONS>, below, for more info on why this is useful.
165		185
166	=item $cbor = $cbor->allow_unknown ([$enable])	186	=item $cbor = $cbor->allow_unknown ([$enable])
167		187
168	=item $enabled = $cbor->get_allow_unknown	188	=item $enabled = $cbor->get_allow_unknown
169		189
…		…
186	as an array, is referenced multiple times), but instead will emit a	206	as an array, is referenced multiple times), but instead will emit a
187	reference to the earlier value.	207	reference to the earlier value.
188		208
189	This means that such values will only be encoded once, and will not result	209	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	210	in a deep cloning of the value on decode, in decoders supporting the value
191	sharing extension.	211	sharing extension. This also makes it possible to encode cyclic data
		212	structures (which need C<allow_cycles> to be enabled to be decoded by this
		213	module).
192		214
193	It is recommended to leave it off unless you know your	215	It is recommended to leave it off unless you know your
194	communication partner supports the value sharing extensions to CBOR	216	communication partner supports the value sharing extensions to CBOR
195	(http://cbor.schmorp.de/value-sharing).	217	(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the
		218	resulting data structure might be unusable.
196		219
197	Detecting shared values incurs a runtime overhead when values are encoded	220	Detecting shared values incurs a runtime overhead when values are encoded
198	that have a reference counter large than one, and might unnecessarily	221	that have a reference counter large than one, and might unnecessarily
199	increase the encoded size, as potentially shared values are encode as	222	increase the encoded size, as potentially shared values are encoded as
200	sharable whether or not they are actually shared.	223	shareable whether or not they are actually shared.
201		224
202	At the moment, only targets of references can be shared (e.g. scalars,	225	At the moment, only targets of references can be shared (e.g. scalars,
203	arrays or hashes pointed to by a reference). Weirder constructs, such as	226	arrays or hashes pointed to by a reference). Weirder constructs, such as
204	an array with multiple "copies" of the I<same> string, which are hard but	227	an array with multiple "copies" of the I<same> string, which are hard but
205	not impossible to create in Perl, are not supported (this is the same as	228	not impossible to create in Perl, are not supported (this is the same as
206	for L<Storable>).	229	with L<Storable>).
207		230
208	If C<$enable> is false (the default), then C<encode> will encode	231	If C<$enable> is false (the default), then C<encode> will encode shared
209	exception when it encounters anything it cannot encode as CBOR.	232	data structures repeatedly, unsharing them in the process. Cyclic data
		233	structures cannot be encoded in this mode.
210		234
211	This option does not affect C<decode> in any way - shared values and	235	This option does not affect C<decode> in any way - shared values and
212	references will always be decoded properly if present.	236	references will always be decoded properly if present.
213		237
		238	=item $cbor = $cbor->allow_cycles ([$enable])
		239
		240	=item $enabled = $cbor->get_allow_cycles
		241
		242	If C<$enable> is true (or missing), then C<decode> will happily decode
		243	self-referential (cyclic) data structures. By default these will not be
		244	decoded, as they need manual cleanup to avoid memory leaks, so code that
		245	isn't prepared for this will not leak memory.
		246
		247	If C<$enable> is false (the default), then C<decode> will throw an error
		248	when it encounters a self-referential/cyclic data structure.
		249
		250	FUTURE DIRECTION: the motivation behind this option is to avoid I<real>
		251	cycles - future versions of this module might chose to decode cyclic data
		252	structures using weak references when this option is off, instead of
		253	throwing an error.
		254
		255	This option does not affect C<encode> in any way - shared values and
		256	references will always be encoded properly if present.
		257
		258	=item $cbor = $cbor->forbid_objects ([$enable])
		259
		260	=item $enabled = $cbor->get_forbid_objects
		261
		262	Disables the use of the object serialiser protocol.
		263
		264	If C<$enable> is true (or missing), then C<encode> will will throw an
		265	exception when it encounters perl objects that would be encoded using the
		266	perl-object tag (26). When C<decode> encounters such tags, it will fall
		267	back to the general filter/tagged logic as if this were an unknown tag (by
		268	default resulting in a C<CBOR::XC::Tagged> object).
		269
		270	If C<$enable> is false (the default), then C<encode> will use the
		271	L<Types::Serialiser> object serialisation protocol to serialise objects
		272	into perl-object tags, and C<decode> will do the same to decode such tags.
		273
		274	See L<SECURITY CONSIDERATIONS>, below, for more info on why forbidding this
		275	protocol can be useful.
		276
214	=item $cbor = $cbor->allow_stringref ([$enable])	277	=item $cbor = $cbor->pack_strings ([$enable])
215		278
216	=item $enabled = $cbor->get_allow_stringref	279	=item $enabled = $cbor->get_pack_strings
217		280
218	If C<$enable> is true (or missing), then C<encode> will try not to encode	281	If C<$enable> is true (or missing), then C<encode> will try not to encode
219	the same string twice, but will instead encode a reference to the string	282	the same string twice, but will instead encode a reference to the string
220	instead. Depending on your data format. this can save a lot of space, but	283	instead. Depending on your data format, this can save a lot of space, but
221	also results in a very large runtime overhead (expect encoding times to be	284	also results in a very large runtime overhead (expect encoding times to be
222	2-4 times as high as without).	285	2-4 times as high as without).
223		286
224	It is recommended to leave it off unless you know your	287	It is recommended to leave it off unless you know your
225	communications partner supports the stringref extension to CBOR	288	communications partner supports the stringref extension to CBOR
226	(http://cbor.schmorp.de/stringref).	289	(L<http://cbor.schmorp.de/stringref>), as without decoder support, the
		290	resulting data structure might not be usable.
227		291
228	If C<$enable> is false (the default), then C<encode> will encode	292	If C<$enable> is false (the default), then C<encode> will encode strings
229	exception when it encounters anything it cannot encode as CBOR.	293	the standard CBOR way.
230		294
231	This option does not affect C<decode> in any way - string references will	295	This option does not affect C<decode> in any way - string references will
232	always be decoded properly if present.	296	always be decoded properly if present.
		297
		298	=item $cbor = $cbor->text_keys ([$enable])
		299
		300	=item $enabled = $cbor->get_text_keys
		301
		302	If C<$enabled> is true (or missing), then C<encode> will encode all
		303	perl hash keys as CBOR text strings/UTF-8 string, upgrading them as needed.
		304
		305	If C<$enable> is false (the default), then C<encode> will encode hash keys
		306	normally - upgraded perl strings (strings internally encoded as UTF-8) as
		307	CBOR text strings, and downgraded perl strings as CBOR byte strings.
		308
		309	This option does not affect C<decode> in any way.
		310
		311	This option is useful for interoperability with CBOR decoders that don't
		312	treat byte strings as a form of text. It is especially useful as Perl
		313	gives very little control over hash keys.
		314
		315	Enabling this option can be slow, as all downgraded hash keys that are
		316	encoded need to be scanned and converted to UTF-8.
		317
		318	=item $cbor = $cbor->text_strings ([$enable])
		319
		320	=item $enabled = $cbor->get_text_strings
		321
		322	This option works similar to C<text_keys>, above, but works on all strings
		323	(including hash keys), so C<text_keys> has no further effect after
		324	enabling C<text_strings>.
		325
		326	If C<$enabled> is true (or missing), then C<encode> will encode all perl
		327	strings as CBOR text strings/UTF-8 strings, upgrading them as needed.
		328
		329	If C<$enable> is false (the default), then C<encode> will encode strings
		330	normally (but see C<text_keys>) - upgraded perl strings (strings
		331	internally encoded as UTF-8) as CBOR text strings, and downgraded perl
		332	strings as CBOR byte strings.
		333
		334	This option does not affect C<decode> in any way.
		335
		336	This option has similar advantages and disadvantages as C<text_keys>. In
		337	addition, this option effectively removes the ability to automatically
		338	encode byte strings, which might break some C<FREEZE> and C<TO_CBOR>
		339	methods that rely on this.
		340
		341	A workaround is to use explicit type casts, which are unaffected by this option.
		342
		343	=item $cbor = $cbor->validate_utf8 ([$enable])
		344
		345	=item $enabled = $cbor->get_validate_utf8
		346
		347	If C<$enable> is true (or missing), then C<decode> will validate that
		348	elements (text strings) containing UTF-8 data in fact contain valid UTF-8
		349	data (instead of blindly accepting it). This validation obviously takes
		350	extra time during decoding.
		351
		352	The concept of "valid UTF-8" used is perl's concept, which is a superset
		353	of the official UTF-8.
		354
		355	If C<$enable> is false (the default), then C<decode> will blindly accept
		356	UTF-8 data, marking them as valid UTF-8 in the resulting data structure
		357	regardless of whether that's true or not.
		358
		359	Perl isn't too happy about corrupted UTF-8 in strings, but should
		360	generally not crash or do similarly evil things. Extensions might be not
		361	so forgiving, so it's recommended to turn on this setting if you receive
		362	untrusted CBOR.
		363
		364	This option does not affect C<encode> in any way - strings that are
		365	supposedly valid UTF-8 will simply be dumped into the resulting CBOR
		366	string without checking whether that is, in fact, true or not.
233		367
234	=item $cbor = $cbor->filter ([$cb->($tag, $value)])	368	=item $cbor = $cbor->filter ([$cb->($tag, $value)])
235		369
236	=item $cb_or_undef = $cbor->get_filter	370	=item $cb_or_undef = $cbor->get_filter
237		371
…		…
250	replace the tagged value in the decoded data structure, or no values,	384	replace the tagged value in the decoded data structure, or no values,
251	which will result in default handling, which currently means the decoder	385	which will result in default handling, which currently means the decoder
252	creates a C<CBOR::XS::Tagged> object to hold the tag and the value.	386	creates a C<CBOR::XS::Tagged> object to hold the tag and the value.
253		387
254	When the filter is cleared (the default state), the default filter	388	When the filter is cleared (the default state), the default filter
255	function, C<CBOR::XS::default_filter>, is used. This function simply looks	389	function, C<CBOR::XS::default_filter>, is used. This function simply
256	up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be	390	looks up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists
257	a code reference that is called with tag and value, and is responsible for	391	it must be a code reference that is called with tag and value, and is
258	decoding the value. If no entry exists, it returns no values.	392	responsible for decoding the value. If no entry exists, it returns no
		393	values. C<CBOR::XS> provides a number of default filter functions already,
		394	the the C<%CBOR::XS::FILTER> hash can be freely extended with more.
259		395
		396	C<CBOR::XS> additionally provides an alternative filter function that is
		397	supposed to be safe to use with untrusted data (which the default filter
		398	might not), called C<CBOR::XS::safe_filter>, which works the same as
		399	the C<default_filter> but uses the C<%CBOR::XS::SAFE_FILTER> variable
		400	instead. It is prepopulated with the tag decoding functions that are
		401	deemed safe (basically the same as C<%CBOR::XS::FILTER> without all
		402	the bignum tags), and can be extended by user code as wlel, although,
		403	obviously, one should be very careful about adding decoding functions
		404	here, since the expectation is that they are safe to use on untrusted
		405	data, after all.
		406
260	Example: decode all tags not handled internally into CBOR::XS::Tagged	407	Example: decode all tags not handled internally into C<CBOR::XS::Tagged>
261	objects, with no other special handling (useful when working with	408	objects, with no other special handling (useful when working with
262	potentially "unsafe" CBOR data).	409	potentially "unsafe" CBOR data).
263		410
264	CBOR::XS->new->filter (sub { })->decode ($cbor_data);	411	CBOR::XS->new->filter (sub { })->decode ($cbor_data);
265		412
…		…
269	$CBOR::XS::FILTER{1347375694} = sub {	416	$CBOR::XS::FILTER{1347375694} = sub {
270	my ($tag, $value);	417	my ($tag, $value);
271		418
272	"tag 1347375694 value $value"	419	"tag 1347375694 value $value"
273	};	420	};
		421
		422	Example: provide your own filter function that looks up tags in your own
		423	hash:
		424
		425	my %my_filter = (
		426	998347484 => sub {
		427	my ($tag, $value);
		428
		429	"tag 998347484 value $value"
		430	};
		431	);
		432
		433	my $coder = CBOR::XS->new->filter (sub {
		434	&{ $my_filter{$_[0]} or return }
		435	});
		436
		437
		438	Example: use the safe filter function (see L<SECURITY CONSIDERATIONS> for
		439	more considerations on security).
		440
		441	CBOR::XS->new->filter (\&CBOR::XS::safe_filter)->decode ($cbor_data);
274		442
275	=item $cbor_data = $cbor->encode ($perl_scalar)	443	=item $cbor_data = $cbor->encode ($perl_scalar)
276		444
277	Converts the given Perl data structure (a scalar value) to its CBOR	445	Converts the given Perl data structure (a scalar value) to its CBOR
278	representation.	446	representation.
…		…
288	when there is trailing garbage after the CBOR string, it will silently	456	when there is trailing garbage after the CBOR string, it will silently
289	stop parsing there and return the number of characters consumed so far.	457	stop parsing there and return the number of characters consumed so far.
290		458
291	This is useful if your CBOR texts are not delimited by an outer protocol	459	This is useful if your CBOR texts are not delimited by an outer protocol
292	and you need to know where the first CBOR string ends amd the next one	460	and you need to know where the first CBOR string ends amd the next one
293	starts.	461	starts - CBOR strings are self-delimited, so it is possible to concatenate
		462	CBOR strings without any delimiters or size fields and recover their data.
294		463
295	CBOR::XS->new->decode_prefix ("......")	464	CBOR::XS->new->decode_prefix ("......")
296	=> ("...", 3)	465	=> ("...", 3)
		466
		467	=back
		468
		469	=head2 INCREMENTAL PARSING
		470
		471	In some cases, there is the need for incremental parsing of JSON
		472	texts. While this module always has to keep both CBOR text and resulting
		473	Perl data structure in memory at one time, it does allow you to parse a
		474	CBOR stream incrementally, using a similar to using "decode_prefix" to see
		475	if a full CBOR object is available, but is much more efficient.
		476
		477	It basically works by parsing as much of a CBOR string as possible - if
		478	the CBOR data is not complete yet, the pasrer will remember where it was,
		479	to be able to restart when more data has been accumulated. Once enough
		480	data is available to either decode a complete CBOR value or raise an
		481	error, a real decode will be attempted.
		482
		483	A typical use case would be a network protocol that consists of sending
		484	and receiving CBOR-encoded messages. The solution that works with CBOR and
		485	about anything else is by prepending a length to every CBOR value, so the
		486	receiver knows how many octets to read. More compact (and slightly slower)
		487	would be to just send CBOR values back-to-back, as C<CBOR::XS> knows where
		488	a CBOR value ends, and doesn't need an explicit length.
		489
		490	The following methods help with this:
		491
		492	=over 4
		493
		494	=item @decoded = $cbor->incr_parse ($buffer)
		495
		496	This method attempts to decode exactly one CBOR value from the beginning
		497	of the given C<$buffer>. The value is removed from the C<$buffer> on
		498	success. When C<$buffer> doesn't contain a complete value yet, it returns
		499	nothing. Finally, when the C<$buffer> doesn't start with something
		500	that could ever be a valid CBOR value, it raises an exception, just as
		501	C<decode> would. In the latter case the decoder state is undefined and
		502	must be reset before being able to parse further.
		503
		504	This method modifies the C<$buffer> in place. When no CBOR value can be
		505	decoded, the decoder stores the current string offset. On the next call,
		506	continues decoding at the place where it stopped before. For this to make
		507	sense, the C<$buffer> must begin with the same octets as on previous
		508	unsuccessful calls.
		509
		510	You can call this method in scalar context, in which case it either
		511	returns a decoded value or C<undef>. This makes it impossible to
		512	distinguish between CBOR null values (which decode to C<undef>) and an
		513	unsuccessful decode, which is often acceptable.
		514
		515	=item @decoded = $cbor->incr_parse_multiple ($buffer)
		516
		517	Same as C<incr_parse>, but attempts to decode as many CBOR values as
		518	possible in one go, instead of at most one. Calls to C<incr_parse> and
		519	C<incr_parse_multiple> can be interleaved.
		520
		521	=item $cbor->incr_reset
		522
		523	Resets the incremental decoder. This throws away any saved state, so that
		524	subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse
		525	a new CBOR value from the beginning of the C<$buffer> again.
		526
		527	This method can be called at any time, but it I<must> be called if you want
		528	to change your C<$buffer> or there was a decoding error and you want to
		529	reuse the C<$cbor> object for future incremental parsings.
297		530
298	=back	531	=back
299		532
300		533
301	=head1 MAPPING	534	=head1 MAPPING
…		…
319	CBOR integers become (numeric) perl scalars. On perls without 64 bit	552	CBOR integers become (numeric) perl scalars. On perls without 64 bit
320	support, 64 bit integers will be truncated or otherwise corrupted.	553	support, 64 bit integers will be truncated or otherwise corrupted.
321		554
322	=item byte strings	555	=item byte strings
323		556
324	Byte strings will become octet strings in Perl (the byte values 0..255	557	Byte strings will become octet strings in Perl (the Byte values 0..255
325	will simply become characters of the same value in Perl).	558	will simply become characters of the same value in Perl).
326		559
327	=item UTF-8 strings	560	=item UTF-8 strings
328		561
329	UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be	562	UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be
…		…
352	=item tagged values	585	=item tagged values
353		586
354	Tagged items consists of a numeric tag and another CBOR value.	587	Tagged items consists of a numeric tag and another CBOR value.
355		588
356	See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>	589	See L<TAG HANDLING AND EXTENSIONS> and the description of C<< ->filter >>
357	for details.	590	for details on which tags are handled how.
358		591
359	=item anything else	592	=item anything else
360		593
361	Anything else (e.g. unsupported simple values) will raise a decoding	594	Anything else (e.g. unsupported simple values) will raise a decoding
362	error.	595	error.
…		…
365		598
366		599
367	=head2 PERL -> CBOR	600	=head2 PERL -> CBOR
368		601
369	The mapping from Perl to CBOR is slightly more difficult, as Perl is a	602	The mapping from Perl to CBOR is slightly more difficult, as Perl is a
370	truly typeless language, so we can only guess which CBOR type is meant by	603	typeless language. That means this module can only guess which CBOR type
371	a Perl value.	604	is meant by a perl value.
372		605
373	=over 4	606	=over 4
374		607
375	=item hash references	608	=item hash references
376		609
377	Perl hash references become CBOR maps. As there is no inherent ordering in	610	Perl hash references become CBOR maps. As there is no inherent ordering in
378	hash keys (or CBOR maps), they will usually be encoded in a pseudo-random	611	hash keys (or CBOR maps), they will usually be encoded in a pseudo-random
379	order.	612	order. This order can be different each time a hash is encoded.
380		613
381	Currently, tied hashes will use the indefinite-length format, while normal	614	Currently, tied hashes will use the indefinite-length format, while normal
382	hashes will use the fixed-length format.	615	hashes will use the fixed-length format.
383		616
384	=item array references	617	=item array references
385		618
386	Perl array references become fixed-length CBOR arrays.	619	Perl array references become fixed-length CBOR arrays.
387		620
388	=item other references	621	=item other references
389		622
390	Other unblessed references are generally not allowed and will cause an	623	Other unblessed references will be represented using
391	exception to be thrown, except for references to the integers C<0> and	624	the indirection tag extension (tag value C<22098>,
392	C<1>, which get turned into false and true in CBOR.	625	L<http://cbor.schmorp.de/indirection>). CBOR decoders are guaranteed
		626	to be able to decode these values somehow, by either "doing the right
		627	thing", decoding into a generic tagged object, simply ignoring the tag, or
		628	something else.
393		629
394	=item CBOR::XS::Tagged objects	630	=item CBOR::XS::Tagged objects
395		631
396	Objects of this type must be arrays consisting of a single C<[tag, value]>	632	Objects of this type must be arrays consisting of a single C<[tag, value]>
397	pair. The (numerical) tag will be encoded as a CBOR tag, the value will	633	pair. The (numerical) tag will be encoded as a CBOR tag, the value will
398	be encoded as appropriate for the value. You cna use C<CBOR::XS::tag> to	634	be encoded as appropriate for the value. You must use C<CBOR::XS::tag> to
399	create such objects.	635	create such objects.
400		636
401	=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error	637	=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error
402		638
403	These special values become CBOR true, CBOR false and CBOR undefined	639	These special values become CBOR true, CBOR false and CBOR undefined
…		…
420	# dump as number	656	# dump as number
421	encode_cbor [2] # yields [2]	657	encode_cbor [2] # yields [2]
422	encode_cbor [-3.0e17] # yields [-3e+17]	658	encode_cbor [-3.0e17] # yields [-3e+17]
423	my $value = 5; encode_cbor [$value] # yields [5]	659	my $value = 5; encode_cbor [$value] # yields [5]
424		660
425	# used as string, so dump as string	661	# used as string, so dump as string (either byte or text)
426	print $value;	662	print $value;
427	encode_cbor [$value] # yields ["5"]	663	encode_cbor [$value] # yields ["5"]
428		664
429	# undef becomes null	665	# undef becomes null
430	encode_cbor [undef] # yields [null]	666	encode_cbor [undef] # yields [null]
…		…
433		669
434	my $x = 3.1; # some variable containing a number	670	my $x = 3.1; # some variable containing a number
435	"$x"; # stringified	671	"$x"; # stringified
436	$x .= ""; # another, more awkward way to stringify	672	$x .= ""; # another, more awkward way to stringify
437	print $x; # perl does it for you, too, quite often	673	print $x; # perl does it for you, too, quite often
		674
		675	You can force whether a string is encoded as byte or text string by using
		676	C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled).
		677
		678	utf8::upgrade $x; # encode $x as text string
		679	utf8::downgrade $x; # encode $x as byte string
		680
		681	More options are available, see L<TYPE CASTS>, below, and the C<text_keys>
		682	and C<text_strings> options.
		683
		684	Perl doesn't define what operations up- and downgrade strings, so if the
		685	difference between byte and text is important, you should up- or downgrade
		686	your string as late as possible before encoding. You can also force the
		687	use of CBOR text strings by using C<text_keys> or C<text_strings>.
438		688
439	You can force the type to be a CBOR number by numifying it:	689	You can force the type to be a CBOR number by numifying it:
440		690
441	my $x = "3"; # some variable containing a string	691	my $x = "3"; # some variable containing a string
442	$x += 0; # numify it, ensuring it will be dumped as a number	692	$x += 0; # numify it, ensuring it will be dumped as a number
…		…
453	represent numerical values are supported, but might suffer loss of	703	represent numerical values are supported, but might suffer loss of
454	precision.	704	precision.
455		705
456	=back	706	=back
457		707
		708	=head2 TYPE CASTS
		709
		710	B<EXPERIMENTAL>: As an experimental extension, C<CBOR::XS> allows you to
		711	force specific CBOR types to be used when encoding. That allows you to
		712	encode types not normally accessible (e.g. half floats) as well as force
		713	string types even when C<text_strings> is in effect.
		714
		715	Type forcing is done by calling a special "cast" function which keeps a
		716	copy of the value and returns a new value that can be handed over to any
		717	CBOR encoder function.
		718
		719	The following casts are currently available (all of which are unary
		720	operators, that is, have a prototype of C<$>):
		721
		722	=over
		723
		724	=item CBOR::XS::as_int $value
		725
		726	Forces the value to be encoded as some form of (basic, not bignum) integer
		727	type.
		728
		729	=item CBOR::XS::as_text $value
		730
		731	Forces the value to be encoded as (UTF-8) text values.
		732
		733	=item CBOR::XS::as_bytes $value
		734
		735	Forces the value to be encoded as a (binary) string value.
		736
		737	Example: encode a perl string as binary even though C<text_strings> is in
		738	effect.
		739
		740	CBOR::XS->new->text_strings->encode ([4, "text", CBOR::XS::bytes "bytevalue"]);
		741
		742	=item CBOR::XS::as_bool $value
		743
		744	Converts a Perl boolean (which can be any kind of scalar) into a CBOR
		745	boolean. Strictly the same, but shorter to write, than:
		746
		747	$value ? Types::Serialiser::true : Types::Serialiser::false
		748
		749	=item CBOR::XS::as_float16 $value
		750
		751	Forces half-float (IEEE 754 binary16) encoding of the given value.
		752
		753	=item CBOR::XS::as_float32 $value
		754
		755	Forces single-float (IEEE 754 binary32) encoding of the given value.
		756
		757	=item CBOR::XS::as_float64 $value
		758
		759	Forces double-float (IEEE 754 binary64) encoding of the given value.
		760
		761	=item CBOR::XS::as_cbor $cbor_text
		762
		763	Not a type cast per-se, this type cast forces the argument to be encoded
		764	as-is. This can be used to embed pre-encoded CBOR data.
		765
		766	Note that no checking on the validity of the C<$cbor_text> is done - it's
		767	the callers responsibility to correctly encode values.
		768
		769	=item CBOR::XS::as_map [key => value...]
		770
		771	Treat the array reference as key value pairs and output a CBOR map. This
		772	allows you to generate CBOR maps with arbitrary key types (or, if you
		773	don't care about semantics, duplicate keys or pairs in a custom order),
		774	which is otherwise hard to do with Perl.
		775
		776	The single argument must be an array reference with an even number of
		777	elements.
		778
		779	Note that only the reference to the array is copied, the array itself is
		780	not. Modifications done to the array before calling an encoding function
		781	will be reflected in the encoded output.
		782
		783	Example: encode a CBOR map with a string and an integer as keys.
		784
		785	encode_cbor CBOR::XS::as_map [string => "value", 5 => "value"]
		786
		787	=back
		788
		789	=cut
		790
		791	sub CBOR::XS::as_cbor ($) { bless [$_[0], 0, undef], CBOR::XS::Tagged:: }
		792	sub CBOR::XS::as_int ($) { bless [$_[0], 1, undef], CBOR::XS::Tagged:: }
		793	sub CBOR::XS::as_bytes ($) { bless [$_[0], 2, undef], CBOR::XS::Tagged:: }
		794	sub CBOR::XS::as_text ($) { bless [$_[0], 3, undef], CBOR::XS::Tagged:: }
		795	sub CBOR::XS::as_float16 ($) { bless [$_[0], 4, undef], CBOR::XS::Tagged:: }
		796	sub CBOR::XS::as_float32 ($) { bless [$_[0], 5, undef], CBOR::XS::Tagged:: }
		797	sub CBOR::XS::as_float64 ($) { bless [$_[0], 6, undef], CBOR::XS::Tagged:: }
		798
		799	sub CBOR::XS::as_bool ($) { $_[0] ? $Types::Serialiser::true : $Types::Serialiser::false }
		800
		801	sub CBOR::XS::as_map ($) {
		802	ARRAY:: eq ref $_[0]
		803	and $#{ $_[0] } & 1
		804	or do { require Carp; Carp::croak ("CBOR::XS::as_map only acepts array references with an even number of elements, caught") };
		805
		806	bless [$_[0], 7, undef], CBOR::XS::Tagged::
		807	}
		808
458	=head2 OBJECT SERIALISATION	809	=head2 OBJECT SERIALISATION
		810
		811	This module implements both a CBOR-specific and the generic
		812	L<Types::Serialier> object serialisation protocol. The following
		813	subsections explain both methods.
		814
		815	=head3 ENCODING
459		816
460	This module knows two way to serialise a Perl object: The CBOR-specific	817	This module knows two way to serialise a Perl object: The CBOR-specific
461	way, and the generic way.	818	way, and the generic way.
462		819
463	Whenever the encoder encounters a Perl object that it cnanot serialise	820	Whenever the encoder encounters a Perl object that it cannot serialise
464	directly (most of them), it will first look up the C<TO_CBOR> method on	821	directly (most of them), it will first look up the C<TO_CBOR> method on
465	it.	822	it.
466		823
467	If it has a C<TO_CBOR> method, it will call it with the object as only	824	If it has a C<TO_CBOR> method, it will call it with the object as only
468	argument, and expects exactly one return value, which it will then	825	argument, and expects exactly one return value, which it will then
…		…
474		831
475	The C<FREEZE> method can return any number of values (i.e. zero or	832	The C<FREEZE> method can return any number of values (i.e. zero or
476	more). These will be encoded as CBOR perl object, together with the	833	more). These will be encoded as CBOR perl object, together with the
477	classname.	834	classname.
478		835
		836	These methods I<MUST NOT> change the data structure that is being
		837	serialised. Failure to comply to this can result in memory corruption -
		838	and worse.
		839
479	If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail	840	If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail
480	with an error.	841	with an error.
481		842
		843	=head3 DECODING
		844
482	Objects encoded via C<TO_CBOR> cannot be automatically decoded, but	845	Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded,
483	objects encoded via C<FREEZE> can be decoded using the following protocol:	846	but objects encoded via C<FREEZE> can be decoded using the following
		847	protocol:
484		848
485	When an encoded CBOR perl object is encountered by the decoder, it will	849	When an encoded CBOR perl object is encountered by the decoder, it will
486	look up the C<THAW> method, by using the stored classname, and will fail	850	look up the C<THAW> method, by using the stored classname, and will fail
487	if the method cannot be found.	851	if the method cannot be found.
488		852
489	After the lookup it will call the C<THAW> method with the stored classname	853	After the lookup it will call the C<THAW> method with the stored classname
490	as first argument, the constant string C<CBOR> as second argument, and all	854	as first argument, the constant string C<CBOR> as second argument, and all
491	values returned by C<FREEZE> as remaining arguments.	855	values returned by C<FREEZE> as remaining arguments.
492		856
493	=head4 EXAMPLES	857	=head3 EXAMPLES
494		858
495	Here is an example C<TO_CBOR> method:	859	Here is an example C<TO_CBOR> method:
496		860
497	sub My::Object::TO_CBOR {	861	sub My::Object::TO_CBOR {
498	my ($obj) = @_;	862	my ($obj) = @_;
…		…
509		873
510	sub URI::TO_CBOR {	874	sub URI::TO_CBOR {
511	my ($self) = @_;	875	my ($self) = @_;
512	my $uri = "$self"; # stringify uri	876	my $uri = "$self"; # stringify uri
513	utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string	877	utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string
514	CBOR::XS::tagged 32, "$_[0]"	878	CBOR::XS::tag 32, "$_[0]"
515	}	879	}
516		880
517	This will encode URIs as a UTF-8 string with tag 32, which indicates an	881	This will encode URIs as a UTF-8 string with tag 32, which indicates an
518	URI.	882	URI.
519		883
…		…
530	"$self" # encode url string	894	"$self" # encode url string
531	}	895	}
532		896
533	sub URI::THAW {	897	sub URI::THAW {
534	my ($class, $serialiser, $uri) = @_;	898	my ($class, $serialiser, $uri) = @_;
535
536	$class->new ($uri)	899	$class->new ($uri)
537	}	900	}
538		901
539	Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For	902	Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For
540	example, a C<FREEZE> method that returns "type", "id" and "variant" values	903	example, a C<FREEZE> method that returns "type", "id" and "variant" values
…		…
671	additional tags (such as base64url).	1034	additional tags (such as base64url).
672		1035
673	=head2 ENFORCED TAGS	1036	=head2 ENFORCED TAGS
674		1037
675	These tags are always handled when decoding, and their handling cannot be	1038	These tags are always handled when decoding, and their handling cannot be
676	overriden by the user.	1039	overridden by the user.
677		1040
678	=over 4	1041	=over 4
679		1042
680	=item <unassigned> (perl-object, L<http://cbor.schmorp.de/perl-object>)	1043	=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>)
681		1044
682	These tags are automatically created (and decoded) for serialisable	1045	These tags are automatically created (and decoded) for serialisable
683	objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object	1046	objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object
684	serialisation protocol). See L<OBJECT SERIALISATION> for details.	1047	serialisation protocol). See L<OBJECT SERIALISATION> for details.
685		1048
686	=item <unassigned>, <unassigned> (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>)	1049	=item 28, 29 (shareable, sharedref, L<http://cbor.schmorp.de/value-sharing>)
687		1050
688	These tags are automatically decoded when encountered, resulting in	1051	These tags are automatically decoded when encountered (and they do not
		1052	result in a cyclic data structure, see C<allow_cycles>), resulting in
689	shared values in the decoded object. They are only encoded, however, when	1053	shared values in the decoded object. They are only encoded, however, when
690	C<allow_sharable> is enabled.	1054	C<allow_sharing> is enabled.
691		1055
		1056	Not all shared values can be successfully decoded: values that reference
		1057	themselves will I<currently> decode as C<undef> (this is not the same
		1058	as a reference pointing to itself, which will be represented as a value
		1059	that contains an indirect reference to itself - these will be decoded
		1060	properly).
		1061
		1062	Note that considerably more shared value data structures can be decoded
		1063	than will be encoded - currently, only values pointed to by references
		1064	will be shared, others will not. While non-reference shared values can be
		1065	generated in Perl with some effort, they were considered too unimportant
		1066	to be supported in the encoder. The decoder, however, will decode these
		1067	values as shared values.
		1068
692	=item <unassigned>, <unassigned> (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>)	1069	=item 256, 25 (stringref-namespace, stringref, L<http://cbor.schmorp.de/stringref>)
693		1070
694	These tags are automatically decoded when encountered. They are only	1071	These tags are automatically decoded when encountered. They are only
695	encoded, however, when C<allow_stringref> is enabled.	1072	encoded, however, when C<pack_strings> is enabled.
696		1073
697	=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)	1074	=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
698		1075
699	This tag is automatically generated when a reference are encountered (with	1076	This tag is automatically generated when a reference are encountered (with
700	the exception of hash and array refernces). It is converted to a reference	1077	the exception of hash and array references). It is converted to a reference
701	when decoding.	1078	when decoding.
702		1079
703	=item 55799 (self-describe CBOR, RFC 7049)	1080	=item 55799 (self-describe CBOR, RFC 7049)
704		1081
705	This value is not generated on encoding (unless explicitly requested by	1082	This value is not generated on encoding (unless explicitly requested by
…		…
708	=back	1085	=back
709		1086
710	=head2 NON-ENFORCED TAGS	1087	=head2 NON-ENFORCED TAGS
711		1088
712	These tags have default filters provided when decoding. Their handling can	1089	These tags have default filters provided when decoding. Their handling can
713	be overriden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by	1090	be overridden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by
714	providing a custom C<filter> callback when decoding.	1091	providing a custom C<filter> callback when decoding.
715		1092
716	When they result in decoding into a specific Perl class, the module	1093	When they result in decoding into a specific Perl class, the module
717	usually provides a corresponding C<TO_CBOR> method as well.	1094	usually provides a corresponding C<TO_CBOR> method as well.
718		1095
…		…
721	provide these modules. The decoding usually fails with an exception if the	1098	provide these modules. The decoding usually fails with an exception if the
722	required module cannot be loaded.	1099	required module cannot be loaded.
723		1100
724	=over 4	1101	=over 4
725		1102
		1103	=item 0, 1 (date/time string, seconds since the epoch)
		1104
		1105	These tags are decoded into L<Time::Piece> objects. The corresponding
		1106	C<Time::Piece::TO_CBOR> method always encodes into tag 1 values currently.
		1107
		1108	The L<Time::Piece> API is generally surprisingly bad, and fractional
		1109	seconds are only accidentally kept intact, so watch out. On the plus side,
		1110	the module comes with perl since 5.10, which has to count for something.
		1111
726	=item 2, 3 (positive/negative bignum)	1112	=item 2, 3 (positive/negative bignum)
727		1113
728	These tags are decoded into L<Math::BigInt> objects. The corresponding	1114	These tags are decoded into L<Math::BigInt> objects. The corresponding
729	C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR	1115	C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR
730	integers, and others into positive/negative CBOR bignums.	1116	integers, and others into positive/negative CBOR bignums.
731		1117
732	=item 4, 5 (decimal fraction/bigfloat)	1118	=item 4, 5, 264, 265 (decimal fraction/bigfloat)
733		1119
734	Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>	1120	Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>
735	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>	1121	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>
736	encodes into a decimal fraction.	1122	encodes into a decimal fraction (either tag 4 or 264).
737		1123
738	CBOR cannot represent bigfloats with I<very> large exponents - conversion	1124	NaN and infinities are not encoded properly, as they cannot be represented
739	of such big float objects is undefined.	1125	in CBOR.
740		1126
741	Also, NaN and infinities are not encoded properly.	1127	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
		1128
		1129	=item 30 (rational numbers)
		1130
		1131	These tags are decoded into L<Math::BigRat> objects. The corresponding
		1132	C<Math::BigRat::TO_CBOR> method encodes rational numbers with denominator
		1133	C<1> via their numerator only, i.e., they become normal integers or
		1134	C<bignums>.
		1135
		1136	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
742		1137
743	=item 21, 22, 23 (expected later JSON conversion)	1138	=item 21, 22, 23 (expected later JSON conversion)
744		1139
745	CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these	1140	CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these
746	tags.	1141	tags.
…		…
751	C<URI::TO_CBOR> method again results in a CBOR URI value.	1146	C<URI::TO_CBOR> method again results in a CBOR URI value.
752		1147
753	=back	1148	=back
754		1149
755	=cut	1150	=cut
756
757	our %FILTER = (
758	# 0 # rfc4287 datetime, utf-8
759	# 1 # unix timestamp, any
760
761	2 => sub { # pos bigint
762	require Math::BigInt;
763	Math::BigInt->new ("0x" . unpack "H*", pop)
764	},
765
766	3 => sub { # neg bigint
767	require Math::BigInt;
768	-Math::BigInt->new ("0x" . unpack "H*", pop)
769	},
770
771	4 => sub { # decimal fraction, array
772	require Math::BigFloat;
773	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
774	},
775
776	5 => sub { # bigfloat, array
777	require Math::BigFloat;
778	scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2)
779	},
780
781	21 => sub { pop }, # expected conversion to base64url encoding
782	22 => sub { pop }, # expected conversion to base64 encoding
783	23 => sub { pop }, # expected conversion to base16 encoding
784
785	# 24 # embedded cbor, byte string
786
787	32 => sub {
788	require URI;
789	URI->new (pop)
790	},
791
792	# 33 # base64url rfc4648, utf-8
793	# 34 # base64 rfc46484, utf-8
794	# 35 # regex pcre/ecma262, utf-8
795	# 36 # mime message rfc2045, utf-8
796	);
797
798		1151
799	=head1 CBOR and JSON	1152	=head1 CBOR and JSON
800		1153
801	CBOR is supposed to implement a superset of the JSON data model, and is,	1154	CBOR is supposed to implement a superset of the JSON data model, and is,
802	with some coercion, able to represent all JSON texts (something that other	1155	with some coercion, able to represent all JSON texts (something that other
…		…
811	CBOR intact.	1164	CBOR intact.
812		1165
813		1166
814	=head1 SECURITY CONSIDERATIONS	1167	=head1 SECURITY CONSIDERATIONS
815		1168
816	When you are using CBOR in a protocol, talking to untrusted potentially	1169	Tl;dr... if you want to decode or encode CBOR from untrusted sources, you
817	hostile creatures requires relatively few measures.	1170	should start with a coder object created via C<new_safe> (which implements
		1171	the mitigations explained below):
818		1172
		1173	my $coder = CBOR::XS->new_safe;
		1174
		1175	my $data = $coder->decode ($cbor_text);
		1176	my $cbor = $coder->encode ($data);
		1177
		1178	Longer version: When you are using CBOR in a protocol, talking to
		1179	untrusted potentially hostile creatures requires some thought:
		1180
		1181	=over 4
		1182
		1183	=item Security of the CBOR decoder itself
		1184
819	First of all, your CBOR decoder should be secure, that is, should not have	1185	First and foremost, your CBOR decoder should be secure, that is, should
		1186	not have any buffer overflows or similar bugs that could potentially be
820	any buffer overflows. Obviously, this module should ensure that and I am	1187	exploited. Obviously, this module should ensure that and I am trying hard
821	trying hard on making that true, but you never know.	1188	on making that true, but you never know.
822		1189
		1190	=item CBOR::XS can invoke almost arbitrary callbacks during decoding
		1191
		1192	CBOR::XS supports object serialisation - decoding CBOR can cause calls
		1193	to I<any> C<THAW> method in I<any> package that exists in your process
		1194	(that is, CBOR::XS will not try to load modules, but any existing C<THAW>
		1195	method or function can be called, so they all have to be secure).
		1196
		1197	Less obviously, it will also invoke C<TO_CBOR> and C<FREEZE> methods -
		1198	even if all your C<THAW> methods are secure, encoding data structures from
		1199	untrusted sources can invoke those and trigger bugs in those.
		1200
		1201	So, if you are not sure about the security of all the modules you
		1202	have loaded (you shouldn't), you should disable this part using
		1203	C<forbid_objects> or using C<new_safe>.
		1204
		1205	=item CBOR can be extended with tags that call library code
		1206
		1207	CBOR can be extended with tags, and C<CBOR::XS> has a registry of
		1208	conversion functions for many existing tags that can be extended via
		1209	third-party modules (see the C<filter> method).
		1210
		1211	If you don't trust these, you should configure the "safe" filter function,
		1212	C<CBOR::XS::safe_filter> (C<new_safe> does this), which by default only
		1213	includes conversion functions that are considered "safe" by the author
		1214	(but again, they can be extended by third party modules).
		1215
		1216	Depending on your level of paranoia, you can use the "safe" filter:
		1217
		1218	$cbor->filter (\&CBOR::XS::safe_filter);
		1219
		1220	... your own filter...
		1221
		1222	$cbor->filter (sub { ... do your stuffs here ... });
		1223
		1224	... or even no filter at all, disabling all tag decoding:
		1225
		1226	$cbor->filter (sub { });
		1227
		1228	This is never a problem for encoding, as the tag mechanism only exists in
		1229	CBOR texts.
		1230
		1231	=item Resource-starving attacks: object memory usage
		1232
823	Second, you need to avoid resource-starving attacks. That means you should	1233	You need to avoid resource-starving attacks. That means you should limit
824	limit the size of CBOR data you accept, or make sure then when your	1234	the size of CBOR data you accept, or make sure then when your resources
825	resources run out, that's just fine (e.g. by using a separate process that	1235	run out, that's just fine (e.g. by using a separate process that can
826	can crash safely). The size of a CBOR string in octets is usually a good	1236	crash safely). The size of a CBOR string in octets is usually a good
827	indication of the size of the resources required to decode it into a Perl	1237	indication of the size of the resources required to decode it into a Perl
828	structure. While CBOR::XS can check the size of the CBOR text, it might be	1238	structure. While CBOR::XS can check the size of the CBOR text (using
829	too late when you already have it in memory, so you might want to check	1239	C<max_size> - done by C<new_safe>), it might be too late when you already
830	the size before you accept the string.	1240	have it in memory, so you might want to check the size before you accept
		1241	the string.
831		1242
		1243	As for encoding, it is possible to construct data structures that are
		1244	relatively small but result in large CBOR texts (for example by having an
		1245	array full of references to the same big data structure, which will all be
		1246	deep-cloned during encoding by default). This is rarely an actual issue
		1247	(and the worst case is still just running out of memory), but you can
		1248	reduce this risk by using C<allow_sharing>.
		1249
		1250	=item Resource-starving attacks: stack overflows
		1251
832	Third, CBOR::XS recurses using the C stack when decoding objects and	1252	CBOR::XS recurses using the C stack when decoding objects and arrays. The
833	arrays. The C stack is a limited resource: for instance, on my amd64	1253	C stack is a limited resource: for instance, on my amd64 machine with 8MB
834	machine with 8MB of stack size I can decode around 180k nested arrays but	1254	of stack size I can decode around 180k nested arrays but only 14k nested
835	only 14k nested CBOR objects (due to perl itself recursing deeply on croak	1255	CBOR objects (due to perl itself recursing deeply on croak to free the
836	to free the temporary). If that is exceeded, the program crashes. To be	1256	temporary). If that is exceeded, the program crashes. To be conservative,
837	conservative, the default nesting limit is set to 512. If your process	1257	the default nesting limit is set to 512. If your process has a smaller
838	has a smaller stack, you should adjust this setting accordingly with the	1258	stack, you should adjust this setting accordingly with the C<max_depth>
839	C<max_depth> method.	1259	method.
		1260
		1261	=item Resource-starving attacks: CPU en-/decoding complexity
		1262
		1263	CBOR::XS will use the L<Math::BigInt>, L<Math::BigFloat> and
		1264	L<Math::BigRat> libraries to represent encode/decode bignums. These can be
		1265	very slow (as in, centuries of CPU time) and can even crash your program
		1266	(and are generally not very trustworthy). See the next section on bignum
		1267	security for details.
		1268
		1269	=item Data breaches: leaking information in error messages
		1270
		1271	CBOR::XS might leak contents of your Perl data structures in its error
		1272	messages, so when you serialise sensitive information you might want to
		1273	make sure that exceptions thrown by CBOR::XS will not end up in front of
		1274	untrusted eyes.
		1275
		1276	=item Something else...
840		1277
841	Something else could bomb you, too, that I forgot to think of. In that	1278	Something else could bomb you, too, that I forgot to think of. In that
842	case, you get to keep the pieces. I am always open for hints, though...	1279	case, you get to keep the pieces. I am always open for hints, though...
843		1280
844	Also keep in mind that CBOR::XS might leak contents of your Perl data	1281	=back
845	structures in its error messages, so when you serialise sensitive	1282
846	information you might want to make sure that exceptions thrown by CBOR::XS	1283
847	will not end up in front of untrusted eyes.	1284	=head1 BIGNUM SECURITY CONSIDERATIONS
		1285
		1286	CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and
		1287	L<Math::BigFloat> that tries to encode the number in the simplest possible
		1288	way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
		1289	4) or an arbitrary-exponent decimal fraction (tag 264). Rational numbers
		1290	(L<Math::BigRat>, tag 30) can also contain bignums as members.
		1291
		1292	CBOR::XS will also understand base-2 bigfloat or arbitrary-exponent
		1293	bigfloats (tags 5 and 265), but it will never generate these on its own.
		1294
		1295	Using the built-in L<Math::BigInt::Calc> support, encoding and decoding
		1296	decimal fractions is generally fast. Decoding bigints can be slow for very
		1297	big numbers (tens of thousands of digits, something that could potentially
		1298	be caught by limiting the size of CBOR texts), and decoding bigfloats or
		1299	arbitrary-exponent bigfloats can be I<extremely> slow (minutes, decades)
		1300	for large exponents (roughly 40 bit and longer).
		1301
		1302	Additionally, L<Math::BigInt> can take advantage of other bignum
		1303	libraries, such as L<Math::GMP>, which cannot handle big floats with large
		1304	exponents, and might simply abort or crash your program, due to their code
		1305	quality.
		1306
		1307	This can be a concern if you want to parse untrusted CBOR. If it is, you
		1308	might want to disable decoding of tag 2 (bigint) and 3 (negative bigint)
		1309	types. You should also disable types 5 and 265, as these can be slow even
		1310	without bigints.
		1311
		1312	Disabling bigints will also partially or fully disable types that rely on
		1313	them, e.g. rational numbers that use bignums.
		1314
848		1315
849	=head1 CBOR IMPLEMENTATION NOTES	1316	=head1 CBOR IMPLEMENTATION NOTES
850		1317
851	This section contains some random implementation notes. They do not	1318	This section contains some random implementation notes. They do not
852	describe guaranteed behaviour, but merely behaviour as-is implemented	1319	describe guaranteed behaviour, but merely behaviour as-is implemented
…		…
861	Only the double data type is supported for NV data types - when Perl uses	1328	Only the double data type is supported for NV data types - when Perl uses
862	long double to represent floating point values, they might not be encoded	1329	long double to represent floating point values, they might not be encoded
863	properly. Half precision types are accepted, but not encoded.	1330	properly. Half precision types are accepted, but not encoded.
864		1331
865	Strict mode and canonical mode are not implemented.	1332	Strict mode and canonical mode are not implemented.
		1333
		1334
		1335	=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
		1336
		1337	On perls that were built without 64 bit integer support (these are rare
		1338	nowadays, even on 32 bit architectures, as all major Perl distributions
		1339	are built with 64 bit integer support), support for any kind of 64 bit
		1340	value in CBOR is very limited - most likely, these 64 bit values will
		1341	be truncated, corrupted, or otherwise not decoded correctly. This also
		1342	includes string, float, array and map sizes that are stored as 64 bit
		1343	integers.
866		1344
867		1345
868	=head1 THREADS	1346	=head1 THREADS
869		1347
870	This module is I<not> guaranteed to be thread safe and there are no	1348	This module is I<not> guaranteed to be thread safe and there are no
…		…
884	Please refrain from using rt.cpan.org or any other bug reporting	1362	Please refrain from using rt.cpan.org or any other bug reporting
885	service. I put the contact address into my modules for a reason.	1363	service. I put the contact address into my modules for a reason.
886		1364
887	=cut	1365	=cut
888		1366
		1367	# clumsy and slow hv_store-in-hash helper function
		1368	sub _hv_store {
		1369	$_[0]{$_[1]} = $_[2];
		1370	}
		1371
889	our %FILTER = (	1372	our %FILTER = (
890	# 0 # rfc4287 datetime, utf-8	1373	0 => sub { # rfc4287 datetime, utf-8
891	# 1 # unix timestamp, any	1374	require Time::Piece;
		1375	# Time::Piece::Strptime uses the "incredibly flexible date parsing routine"
		1376	# from FreeBSD, which can't parse ISO 8601, RFC3339, RFC4287 or much of anything
		1377	# else either. Whats incredibe over standard strptime totally escapes me.
		1378	# doesn't do fractional times, either. sigh.
		1379	# In fact, it's all a lie, it uses whatever strptime it wants, and of course,
		1380	# they are all incompatible. The openbsd one simply ignores %z (but according to the
		1381	# docs, it would be much more incredibly flexible indeed. If it worked, that is.).
		1382	scalar eval {
		1383	my $s = $_[1];
		1384
		1385	$s =~ s/Z$/+00:00/;
		1386	$s =~ s/(\.[0-9]+)?([+-][0-9][0-9]):([0-9][0-9])$//
		1387	or die;
		1388
		1389	my $b = $1 - ($2 * 60 + $3) * 60; # fractional part + offset. hopefully
		1390	my $d = Time::Piece->strptime ($s, "%Y-%m-%dT%H:%M:%S");
		1391
		1392	Time::Piece::gmtime ($d->epoch + $b)
		1393	} \|\| die "corrupted CBOR date/time string ($_[0])";
		1394	},
		1395
		1396	1 => sub { # seconds since the epoch, possibly fractional
		1397	require Time::Piece;
		1398	scalar Time::Piece::gmtime (pop)
		1399	},
892		1400
893	2 => sub { # pos bigint	1401	2 => sub { # pos bigint
894	require Math::BigInt;	1402	require Math::BigInt;
895	Math::BigInt->new ("0x" . unpack "H*", pop)	1403	Math::BigInt->new ("0x" . unpack "H*", pop)
896	},	1404	},
…		…
903	4 => sub { # decimal fraction, array	1411	4 => sub { # decimal fraction, array
904	require Math::BigFloat;	1412	require Math::BigFloat;
905	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])	1413	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
906	},	1414	},
907		1415
		1416	264 => sub { # decimal fraction with arbitrary exponent
		1417	require Math::BigFloat;
		1418	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
		1419	},
		1420
908	5 => sub { # bigfloat, array	1421	5 => sub { # bigfloat, array
909	require Math::BigFloat;	1422	require Math::BigFloat;
910	scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2)	1423	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1424	},
		1425
		1426	265 => sub { # bigfloat with arbitrary exponent
		1427	require Math::BigFloat;
		1428	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1429	},
		1430
		1431	30 => sub { # rational number
		1432	require Math::BigRat;
		1433	Math::BigRat->new ("$_[1][0]/$_[1][1]") # separate parameters only work in recent versons
911	},	1434	},
912		1435
913	21 => sub { pop }, # expected conversion to base64url encoding	1436	21 => sub { pop }, # expected conversion to base64url encoding
914	22 => sub { pop }, # expected conversion to base64 encoding	1437	22 => sub { pop }, # expected conversion to base64 encoding
915	23 => sub { pop }, # expected conversion to base16 encoding	1438	23 => sub { pop }, # expected conversion to base16 encoding
…		…
925	# 34 # base64 rfc46484, utf-8	1448	# 34 # base64 rfc46484, utf-8
926	# 35 # regex pcre/ecma262, utf-8	1449	# 35 # regex pcre/ecma262, utf-8
927	# 36 # mime message rfc2045, utf-8	1450	# 36 # mime message rfc2045, utf-8
928	);	1451	);
929		1452
930	sub CBOR::XS::default_filter {	1453	sub default_filter {
931	&{ $FILTER{$_[0]} or return }	1454	&{ $FILTER{$_[0]} or return }
		1455	}
		1456
		1457	our %SAFE_FILTER = map { $_ => $FILTER{$_} } 0, 1, 21, 22, 23, 32;
		1458
		1459	sub safe_filter {
		1460	&{ $SAFE_FILTER{$_[0]} or return }
932	}	1461	}
933		1462
934	sub URI::TO_CBOR {	1463	sub URI::TO_CBOR {
935	my $uri = $_[0]->as_string;	1464	my $uri = $_[0]->as_string;
936	utf8::upgrade $uri;	1465	utf8::upgrade $uri;
937	CBOR::XS::tag 32, $uri	1466	tag 32, $uri
938	}	1467	}
939		1468
940	sub Math::BigInt::TO_CBOR {	1469	sub Math::BigInt::TO_CBOR {
941	if ($_[0] >= -2147483648 && $_[0] <= 2147483647) {	1470	if (-2147483648 <= $_[0] && $_[0] <= 2147483647) {
942	$_[0]->numify	1471	$_[0]->numify
943	} else {	1472	} else {
944	my $hex = substr $_[0]->as_hex, 2;	1473	my $hex = substr $_[0]->as_hex, 2;
945	$hex = "0$hex" if 1 & length $hex; # sigh	1474	$hex = "0$hex" if 1 & length $hex; # sigh
946	CBOR::XS::tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex	1475	tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
947	}	1476	}
948	}	1477	}
949		1478
950	sub Math::BigFloat::TO_CBOR {	1479	sub Math::BigFloat::TO_CBOR {
951	my ($m, $e) = $_[0]->parts;	1480	my ($m, $e) = $_[0]->parts;
		1481
		1482	-9223372036854775808 <= $e && $e <= 18446744073709551615
952	CBOR::XS::tag 4, [$e->numify, $m]	1483	? tag 4, [$e->numify, $m]
		1484	: tag 264, [$e, $m]
		1485	}
		1486
		1487	sub Math::BigRat::TO_CBOR {
		1488	my ($n, $d) = $_[0]->parts;
		1489
		1490	# older versions of BigRat need *1, as they not always return numbers
		1491
		1492	$d*1 == 1
		1493	? $n*1
		1494	: tag 30, [$n1, $d1]
		1495	}
		1496
		1497	sub Time::Piece::TO_CBOR {
		1498	tag 1, 0 + $_[0]->epoch
953	}	1499	}
954		1500
955	XSLoader::load "CBOR::XS", $VERSION;	1501	XSLoader::load "CBOR::XS", $VERSION;
956		1502
957	=head1 SEE ALSO	1503	=head1 SEE ALSO

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Comparing CBOR-XS/XS.pm (file contents): Revision 1.24 by root, Fri Nov 22 16:18:59 2013 UTC vs. Revision 1.82 by root, Sat May 8 07:08:12 2021 UTC

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Comparing CBOR-XS/XS.pm (file contents):
Revision 1.24 by root, Fri Nov 22 16:18:59 2013 UTC vs.
Revision 1.82 by root, Sat May 8 07:08:12 2021 UTC