[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 1.71 by root, Sun Nov 29 21:32:01 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<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 = 1.71;
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
…		…
186	as an array, is referenced multiple times), but instead will emit a	204	as an array, is referenced multiple times), but instead will emit a
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.	209	sharing extension. This also makes it possible to encode cyclic data
		210	structures (which need C<allow_cycles> to be enabled to be decoded by this
		211	module).
192		212
193	It is recommended to leave it off unless you know your	213	It is recommended to leave it off unless you know your
194	communication partner supports the value sharing extensions to CBOR	214	communication partner supports the value sharing extensions to CBOR
195	(http://cbor.schmorp.de/value-sharing).	215	(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the
		216	resulting data structure might be unusable.
196		217
197	Detecting shared values incurs a runtime overhead when values are encoded	218	Detecting shared values incurs a runtime overhead when values are encoded
198	that have a reference counter large than one, and might unnecessarily	219	that have a reference counter large than one, and might unnecessarily
199	increase the encoded size, as potentially shared values are encode as	220	increase the encoded size, as potentially shared values are encoded as
200	sharable whether or not they are actually shared.	221	shareable whether or not they are actually shared.
201		222
202	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,
203	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
204	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
205	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
206	for L<Storable>).	227	with L<Storable>).
207		228
208	If C<$enable> is false (the default), then C<encode> will encode	229	If C<$enable> is false (the default), then C<encode> will encode shared
209	exception when it encounters anything it cannot encode as CBOR.	230	data structures repeatedly, unsharing them in the process. Cyclic data
		231	structures cannot be encoded in this mode.
210		232
211	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
212	references will always be decoded properly if present.	234	references will always be decoded properly if present.
213		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
214	=item $cbor = $cbor->allow_stringref ([$enable])	275	=item $cbor = $cbor->pack_strings ([$enable])
215		276
216	=item $enabled = $cbor->get_allow_stringref	277	=item $enabled = $cbor->get_pack_strings
217		278
218	If C<$enable> is true (or missing), then C<encode> will try not to encode	279	If C<$enable> is true (or missing), then C<encode> will try not to encode
219	the same string twice, but will instead encode a reference to the string	280	the same string twice, but will instead encode a reference to the string
220	instead. Depending on your data format. this can save a lot of space, but	281	instead. Depending on your data format, this can save a lot of space, but
221	also results in a very large runtime overhead (expect encoding times to be	282	also results in a very large runtime overhead (expect encoding times to be
222	2-4 times as high as without).	283	2-4 times as high as without).
223		284
224	It is recommended to leave it off unless you know your	285	It is recommended to leave it off unless you know your
225	communications partner supports the stringref extension to CBOR	286	communications partner supports the stringref extension to CBOR
226	(http://cbor.schmorp.de/stringref).	287	(L<http://cbor.schmorp.de/stringref>), as without decoder support, the
		288	resulting data structure might not be usable.
227		289
228	If C<$enable> is false (the default), then C<encode> will encode	290	If C<$enable> is false (the default), then C<encode> will encode strings
229	exception when it encounters anything it cannot encode as CBOR.	291	the standard CBOR way.
230		292
231	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
232	always be decoded properly if present.	294	always be decoded properly if present.
		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.
233		365
234	=item $cbor = $cbor->filter ([$cb->($tag, $value)])	366	=item $cbor = $cbor->filter ([$cb->($tag, $value)])
235		367
236	=item $cb_or_undef = $cbor->get_filter	368	=item $cb_or_undef = $cbor->get_filter
237		369
…		…
250	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,
251	which will result in default handling, which currently means the decoder	383	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.	384	creates a C<CBOR::XS::Tagged> object to hold the tag and the value.
253		385
254	When the filter is cleared (the default state), the default filter	386	When the filter is cleared (the default state), the default filter
255	function, C<CBOR::XS::default_filter>, is used. This function simply looks	387	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	388	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	389	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.	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.
259		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
260	Example: decode all tags not handled internally into CBOR::XS::Tagged	405	Example: decode all tags not handled internally into C<CBOR::XS::Tagged>
261	objects, with no other special handling (useful when working with	406	objects, with no other special handling (useful when working with
262	potentially "unsafe" CBOR data).	407	potentially "unsafe" CBOR data).
263		408
264	CBOR::XS->new->filter (sub { })->decode ($cbor_data);	409	CBOR::XS->new->filter (sub { })->decode ($cbor_data);
265		410
…		…
269	$CBOR::XS::FILTER{1347375694} = sub {	414	$CBOR::XS::FILTER{1347375694} = sub {
270	my ($tag, $value);	415	my ($tag, $value);
271		416
272	"tag 1347375694 value $value"	417	"tag 1347375694 value $value"
273	};	418	};
		419
		420	Example: provide your own filter function that looks up tags in your own
		421	hash:
		422
		423	my %my_filter = (
		424	998347484 => sub {
		425	my ($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);
274		440
275	=item $cbor_data = $cbor->encode ($perl_scalar)	441	=item $cbor_data = $cbor->encode ($perl_scalar)
276		442
277	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
278	representation.	444	representation.
…		…
288	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
289	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.
290		456
291	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
292	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
293	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.
294		461
295	CBOR::XS->new->decode_prefix ("......")	462	CBOR::XS->new->decode_prefix ("......")
296	=> ("...", 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.
297		528
298	=back	529	=back
299		530
300		531
301	=head1 MAPPING	532	=head1 MAPPING
…		…
319	CBOR integers become (numeric) perl scalars. On perls without 64 bit	550	CBOR integers become (numeric) perl scalars. On perls without 64 bit
320	support, 64 bit integers will be truncated or otherwise corrupted.	551	support, 64 bit integers will be truncated or otherwise corrupted.
321		552
322	=item byte strings	553	=item byte strings
323		554
324	Byte strings will become octet strings in Perl (the byte values 0..255	555	Byte strings will become octet strings in Perl (the Byte values 0..255
325	will simply become characters of the same value in Perl).	556	will simply become characters of the same value in Perl).
326		557
327	=item UTF-8 strings	558	=item UTF-8 strings
328		559
329	UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be	560	UTF-8 strings in CBOR will be decoded, i.e. the UTF-8 octets will be
…		…
352	=item tagged values	583	=item tagged values
353		584
354	Tagged items consists of a numeric tag and another CBOR value.	585	Tagged items consists of a numeric tag and another CBOR value.
355		586
356	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 >>
357	for details.	588	for details on which tags are handled how.
358		589
359	=item anything else	590	=item anything else
360		591
361	Anything else (e.g. unsupported simple values) will raise a decoding	592	Anything else (e.g. unsupported simple values) will raise a decoding
362	error.	593	error.
…		…
365		596
366		597
367	=head2 PERL -> CBOR	598	=head2 PERL -> CBOR
368		599
369	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
370	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
371	a Perl value.	602	is meant by a perl value.
372		603
373	=over 4	604	=over 4
374		605
375	=item hash references	606	=item hash references
376		607
377	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
378	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
379	order.	610	order. This order can be different each time a hash is encoded.
380		611
381	Currently, tied hashes will use the indefinite-length format, while normal	612	Currently, tied hashes will use the indefinite-length format, while normal
382	hashes will use the fixed-length format.	613	hashes will use the fixed-length format.
383		614
384	=item array references	615	=item array references
385		616
386	Perl array references become fixed-length CBOR arrays.	617	Perl array references become fixed-length CBOR arrays.
387		618
388	=item other references	619	=item other references
389		620
390	Other unblessed references are generally not allowed and will cause an	621	Other unblessed references will be represented using
391	exception to be thrown, except for references to the integers C<0> and	622	the indirection tag extension (tag value C<22098>,
392	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.
393		627
394	=item CBOR::XS::Tagged objects	628	=item CBOR::XS::Tagged objects
395		629
396	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]>
397	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
398	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
399	create such objects.	633	create such objects.
400		634
401	=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error	635	=item Types::Serialiser::true, Types::Serialiser::false, Types::Serialiser::error
402		636
403	These special values become CBOR true, CBOR false and CBOR undefined	637	These special values become CBOR true, CBOR false and CBOR undefined
…		…
420	# dump as number	654	# dump as number
421	encode_cbor [2] # yields [2]	655	encode_cbor [2] # yields [2]
422	encode_cbor [-3.0e17] # yields [-3e+17]	656	encode_cbor [-3.0e17] # yields [-3e+17]
423	my $value = 5; encode_cbor [$value] # yields [5]	657	my $value = 5; encode_cbor [$value] # yields [5]
424		658
425	# used as string, so dump as string	659	# used as string, so dump as string (either byte or text)
426	print $value;	660	print $value;
427	encode_cbor [$value] # yields ["5"]	661	encode_cbor [$value] # yields ["5"]
428		662
429	# undef becomes null	663	# undef becomes null
430	encode_cbor [undef] # yields [null]	664	encode_cbor [undef] # yields [null]
…		…
433		667
434	my $x = 3.1; # some variable containing a number	668	my $x = 3.1; # some variable containing a number
435	"$x"; # stringified	669	"$x"; # stringified
436	$x .= ""; # another, more awkward way to stringify	670	$x .= ""; # another, more awkward way to stringify
437	print $x; # perl does it for you, too, quite often	671	print $x; # perl does it for you, too, quite often
		672
		673	You can force whether a string is encoded as byte or text string by using
		674	C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled).
		675
		676	utf8::upgrade $x; # encode $x as text string
		677	utf8::downgrade $x; # encode $x as byte string
		678
		679	More options are available, see L<TYPE CASTS>, below, and the C<text_keys>
		680	and C<text_strings> options.
		681
		682	Perl doesn't define what operations up- and downgrade strings, so if the
		683	difference between byte and text is important, you should up- or downgrade
		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>.
438		686
439	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:
440		688
441	my $x = "3"; # some variable containing a string	689	my $x = "3"; # some variable containing a string
442	$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
…		…
453	represent numerical values are supported, but might suffer loss of	701	represent numerical values are supported, but might suffer loss of
454	precision.	702	precision.
455		703
456	=back	704	=back
457		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_text $value
		722
		723	Forces the value to be encoded as (UTF-8) text values.
		724
		725	=item CBOR::XS::as_bytes $value
		726
		727	Forces the value to be encoded as a (binary) string value.
		728
		729	=item CBOR::XS::as_float16 $value
		730
		731	Forces half-float (IEEE 754 binary16) encoding of the given value.
		732
		733	=item CBOR::XS::as_float32 $value
		734
		735	Forces single-float (IEEE 754 binary32) encoding of the given value.
		736
		737	=item CBOR::XS::as_float64 $value
		738
		739	Forces double-float (IEEE 754 binary64) encoding of the given value.
		740
		741	=item, CBOR::XS::as_cbor $cbor_text
		742
		743	Bot a type cast per-se, this type cast forces the argument to eb encoded
		744	as-is. This can be used to embed pre-encoded CBOR data.
		745
		746	Note that no checking on the validity of the C<$cbor_text> is done - it's
		747	the callers responsibility to correctly encode values.
		748
		749	=back
		750
		751	Example: encode a perl string as binary even though C<text_strings> is in
		752	effect.
		753
		754	CBOR::XS->new->text_strings->encode ([4, "text", CBOR::XS::bytes "bytevalue"]);
		755
		756	=cut
		757
		758	sub CBOR::XS::as_cbor ($) { bless [$_[0], 0, undef], CBOR::XS::Tagged:: }
		759	sub CBOR::XS::as_bytes ($) { bless [$_[0], 1, undef], CBOR::XS::Tagged:: }
		760	sub CBOR::XS::as_text ($) { bless [$_[0], 2, undef], CBOR::XS::Tagged:: }
		761	sub CBOR::XS::as_float16 ($) { bless [$_[0], 3, undef], CBOR::XS::Tagged:: }
		762	sub CBOR::XS::as_float32 ($) { bless [$_[0], 4, undef], CBOR::XS::Tagged:: }
		763	sub CBOR::XS::as_float64 ($) { bless [$_[0], 5, undef], CBOR::XS::Tagged:: }
		764
458	=head2 OBJECT SERIALISATION	765	=head2 OBJECT SERIALISATION
		766
		767	This module implements both a CBOR-specific and the generic
		768	L<Types::Serialier> object serialisation protocol. The following
		769	subsections explain both methods.
		770
		771	=head3 ENCODING
459		772
460	This module knows two way to serialise a Perl object: The CBOR-specific	773	This module knows two way to serialise a Perl object: The CBOR-specific
461	way, and the generic way.	774	way, and the generic way.
462		775
463	Whenever the encoder encounters a Perl object that it cnanot serialise	776	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	777	directly (most of them), it will first look up the C<TO_CBOR> method on
465	it.	778	it.
466		779
467	If it has a C<TO_CBOR> method, it will call it with the object as only	780	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	781	argument, and expects exactly one return value, which it will then
…		…
474		787
475	The C<FREEZE> method can return any number of values (i.e. zero or	788	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	789	more). These will be encoded as CBOR perl object, together with the
477	classname.	790	classname.
478		791
		792	These methods I<MUST NOT> change the data structure that is being
		793	serialised. Failure to comply to this can result in memory corruption -
		794	and worse.
		795
479	If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail	796	If an object supports neither C<TO_CBOR> nor C<FREEZE>, encoding will fail
480	with an error.	797	with an error.
481		798
		799	=head3 DECODING
		800
482	Objects encoded via C<TO_CBOR> cannot be automatically decoded, but	801	Objects encoded via C<TO_CBOR> cannot (normally) be automatically decoded,
483	objects encoded via C<FREEZE> can be decoded using the following protocol:	802	but objects encoded via C<FREEZE> can be decoded using the following
		803	protocol:
484		804
485	When an encoded CBOR perl object is encountered by the decoder, it will	805	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	806	look up the C<THAW> method, by using the stored classname, and will fail
487	if the method cannot be found.	807	if the method cannot be found.
488		808
489	After the lookup it will call the C<THAW> method with the stored classname	809	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	810	as first argument, the constant string C<CBOR> as second argument, and all
491	values returned by C<FREEZE> as remaining arguments.	811	values returned by C<FREEZE> as remaining arguments.
492		812
493	=head4 EXAMPLES	813	=head3 EXAMPLES
494		814
495	Here is an example C<TO_CBOR> method:	815	Here is an example C<TO_CBOR> method:
496		816
497	sub My::Object::TO_CBOR {	817	sub My::Object::TO_CBOR {
498	my ($obj) = @_;	818	my ($obj) = @_;
…		…
509		829
510	sub URI::TO_CBOR {	830	sub URI::TO_CBOR {
511	my ($self) = @_;	831	my ($self) = @_;
512	my $uri = "$self"; # stringify uri	832	my $uri = "$self"; # stringify uri
513	utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string	833	utf8::upgrade $uri; # make sure it will be encoded as UTF-8 string
514	CBOR::XS::tagged 32, "$_[0]"	834	CBOR::XS::tag 32, "$_[0]"
515	}	835	}
516		836
517	This will encode URIs as a UTF-8 string with tag 32, which indicates an	837	This will encode URIs as a UTF-8 string with tag 32, which indicates an
518	URI.	838	URI.
519		839
…		…
530	"$self" # encode url string	850	"$self" # encode url string
531	}	851	}
532		852
533	sub URI::THAW {	853	sub URI::THAW {
534	my ($class, $serialiser, $uri) = @_;	854	my ($class, $serialiser, $uri) = @_;
535
536	$class->new ($uri)	855	$class->new ($uri)
537	}	856	}
538		857
539	Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For	858	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	859	example, a C<FREEZE> method that returns "type", "id" and "variant" values
…		…
671	additional tags (such as base64url).	990	additional tags (such as base64url).
672		991
673	=head2 ENFORCED TAGS	992	=head2 ENFORCED TAGS
674		993
675	These tags are always handled when decoding, and their handling cannot be	994	These tags are always handled when decoding, and their handling cannot be
676	overriden by the user.	995	overridden by the user.
677		996
678	=over 4	997	=over 4
679		998
680	=item <unassigned> (perl-object, L<http://cbor.schmorp.de/perl-object>)	999	=item 26 (perl-object, L<http://cbor.schmorp.de/perl-object>)
681		1000
682	These tags are automatically created (and decoded) for serialisable	1001	These tags are automatically created (and decoded) for serialisable
683	objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object	1002	objects using the C<FREEZE/THAW> methods (the L<Types::Serialier> object
684	serialisation protocol). See L<OBJECT SERIALISATION> for details.	1003	serialisation protocol). See L<OBJECT SERIALISATION> for details.
685		1004
686	=item <unassigned>, <unassigned> (sharable, sharedref, L <http://cbor.schmorp.de/value-sharing>)	1005	=item 28, 29 (shareable, sharedref, L<http://cbor.schmorp.de/value-sharing>)
687		1006
688	These tags are automatically decoded when encountered, resulting in	1007	These tags are automatically decoded when encountered (and they do not
		1008	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	1009	shared values in the decoded object. They are only encoded, however, when
690	C<allow_sharable> is enabled.	1010	C<allow_sharing> is enabled.
691		1011
		1012	Not all shared values can be successfully decoded: values that reference
		1013	themselves will I<currently> decode as C<undef> (this is not the same
		1014	as a reference pointing to itself, which will be represented as a value
		1015	that contains an indirect reference to itself - these will be decoded
		1016	properly).
		1017
		1018	Note that considerably more shared value data structures can be decoded
		1019	than will be encoded - currently, only values pointed to by references
		1020	will be shared, others will not. While non-reference shared values can be
		1021	generated in Perl with some effort, they were considered too unimportant
		1022	to be supported in the encoder. The decoder, however, will decode these
		1023	values as shared values.
		1024
692	=item <unassigned>, <unassigned> (stringref-namespace, stringref, L <http://cbor.schmorp.de/stringref>)	1025	=item 256, 25 (stringref-namespace, stringref, L<http://cbor.schmorp.de/stringref>)
693		1026
694	These tags are automatically decoded when encountered. They are only	1027	These tags are automatically decoded when encountered. They are only
695	encoded, however, when C<allow_stringref> is enabled.	1028	encoded, however, when C<pack_strings> is enabled.
696		1029
697	=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)	1030	=item 22098 (indirection, L<http://cbor.schmorp.de/indirection>)
698		1031
699	This tag is automatically generated when a reference are encountered (with	1032	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	1033	the exception of hash and array references). It is converted to a reference
701	when decoding.	1034	when decoding.
702		1035
703	=item 55799 (self-describe CBOR, RFC 7049)	1036	=item 55799 (self-describe CBOR, RFC 7049)
704		1037
705	This value is not generated on encoding (unless explicitly requested by	1038	This value is not generated on encoding (unless explicitly requested by
…		…
708	=back	1041	=back
709		1042
710	=head2 NON-ENFORCED TAGS	1043	=head2 NON-ENFORCED TAGS
711		1044
712	These tags have default filters provided when decoding. Their handling can	1045	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	1046	be overridden by changing the C<%CBOR::XS::FILTER> entry for the tag, or by
714	providing a custom C<filter> callback when decoding.	1047	providing a custom C<filter> callback when decoding.
715		1048
716	When they result in decoding into a specific Perl class, the module	1049	When they result in decoding into a specific Perl class, the module
717	usually provides a corresponding C<TO_CBOR> method as well.	1050	usually provides a corresponding C<TO_CBOR> method as well.
718		1051
…		…
721	provide these modules. The decoding usually fails with an exception if the	1054	provide these modules. The decoding usually fails with an exception if the
722	required module cannot be loaded.	1055	required module cannot be loaded.
723		1056
724	=over 4	1057	=over 4
725		1058
		1059	=item 0, 1 (date/time string, seconds since the epoch)
		1060
		1061	These tags are decoded into L<Time::Piece> objects. The corresponding
		1062	C<Time::Piece::TO_CBOR> method always encodes into tag 1 values currently.
		1063
		1064	The L<Time::Piece> API is generally surprisingly bad, and fractional
		1065	seconds are only accidentally kept intact, so watch out. On the plus side,
		1066	the module comes with perl since 5.10, which has to count for something.
		1067
726	=item 2, 3 (positive/negative bignum)	1068	=item 2, 3 (positive/negative bignum)
727		1069
728	These tags are decoded into L<Math::BigInt> objects. The corresponding	1070	These tags are decoded into L<Math::BigInt> objects. The corresponding
729	C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR	1071	C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR
730	integers, and others into positive/negative CBOR bignums.	1072	integers, and others into positive/negative CBOR bignums.
731		1073
732	=item 4, 5 (decimal fraction/bigfloat)	1074	=item 4, 5, 264, 265 (decimal fraction/bigfloat)
733		1075
734	Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>	1076	Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>
735	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>	1077	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>
736	encodes into a decimal fraction.	1078	encodes into a decimal fraction (either tag 4 or 264).
737		1079
738	CBOR cannot represent bigfloats with I<very> large exponents - conversion	1080	NaN and infinities are not encoded properly, as they cannot be represented
739	of such big float objects is undefined.	1081	in CBOR.
740		1082
741	Also, NaN and infinities are not encoded properly.	1083	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
		1084
		1085	=item 30 (rational numbers)
		1086
		1087	These tags are decoded into L<Math::BigRat> objects. The corresponding
		1088	C<Math::BigRat::TO_CBOR> method encodes rational numbers with denominator
		1089	C<1> via their numerator only, i.e., they become normal integers or
		1090	C<bignums>.
		1091
		1092	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
742		1093
743	=item 21, 22, 23 (expected later JSON conversion)	1094	=item 21, 22, 23 (expected later JSON conversion)
744		1095
745	CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these	1096	CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these
746	tags.	1097	tags.
…		…
751	C<URI::TO_CBOR> method again results in a CBOR URI value.	1102	C<URI::TO_CBOR> method again results in a CBOR URI value.
752		1103
753	=back	1104	=back
754		1105
755	=cut	1106	=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		1107
799	=head1 CBOR and JSON	1108	=head1 CBOR and JSON
800		1109
801	CBOR is supposed to implement a superset of the JSON data model, and is,	1110	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	1111	with some coercion, able to represent all JSON texts (something that other
…		…
811	CBOR intact.	1120	CBOR intact.
812		1121
813		1122
814	=head1 SECURITY CONSIDERATIONS	1123	=head1 SECURITY CONSIDERATIONS
815		1124
816	When you are using CBOR in a protocol, talking to untrusted potentially	1125	Tl;dr... if you want to decode or encode CBOR from untrusted sources, you
817	hostile creatures requires relatively few measures.	1126	should start with a coder object created via C<new_safe> (which implements
		1127	the mitigations explained below):
818		1128
		1129	my $coder = CBOR::XS->new_safe;
		1130
		1131	my $data = $coder->decode ($cbor_text);
		1132	my $cbor = $coder->encode ($data);
		1133
		1134	Longer version: When you are using CBOR in a protocol, talking to
		1135	untrusted potentially hostile creatures requires some thought:
		1136
		1137	=over 4
		1138
		1139	=item Security of the CBOR decoder itself
		1140
819	First of all, your CBOR decoder should be secure, that is, should not have	1141	First and foremost, your CBOR decoder should be secure, that is, should
		1142	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	1143	exploited. Obviously, this module should ensure that and I am trying hard
821	trying hard on making that true, but you never know.	1144	on making that true, but you never know.
822		1145
		1146	=item CBOR::XS can invoke almost arbitrary callbacks during decoding
		1147
		1148	CBOR::XS supports object serialisation - decoding CBOR can cause calls
		1149	to I<any> C<THAW> method in I<any> package that exists in your process
		1150	(that is, CBOR::XS will not try to load modules, but any existing C<THAW>
		1151	method or function can be called, so they all have to be secure).
		1152
		1153	Less obviously, it will also invoke C<TO_CBOR> and C<FREEZE> methods -
		1154	even if all your C<THAW> methods are secure, encoding data structures from
		1155	untrusted sources can invoke those and trigger bugs in those.
		1156
		1157	So, if you are not sure about the security of all the modules you
		1158	have loaded (you shouldn't), you should disable this part using
		1159	C<forbid_objects> or using C<new_safe>.
		1160
		1161	=item CBOR can be extended with tags that call library code
		1162
		1163	CBOR can be extended with tags, and C<CBOR::XS> has a registry of
		1164	conversion functions for many existing tags that can be extended via
		1165	third-party modules (see the C<filter> method).
		1166
		1167	If you don't trust these, you should configure the "safe" filter function,
		1168	C<CBOR::XS::safe_filter> (C<new_safe> does this), which by default only
		1169	includes conversion functions that are considered "safe" by the author
		1170	(but again, they can be extended by third party modules).
		1171
		1172	Depending on your level of paranoia, you can use the "safe" filter:
		1173
		1174	$cbor->filter (\&CBOR::XS::safe_filter);
		1175
		1176	... your own filter...
		1177
		1178	$cbor->filter (sub { ... do your stuffs here ... });
		1179
		1180	... or even no filter at all, disabling all tag decoding:
		1181
		1182	$cbor->filter (sub { });
		1183
		1184	This is never a problem for encoding, as the tag mechanism only exists in
		1185	CBOR texts.
		1186
		1187	=item Resource-starving attacks: object memory usage
		1188
823	Second, you need to avoid resource-starving attacks. That means you should	1189	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	1190	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	1191	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	1192	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	1193	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	1194	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	1195	C<max_size> - done by C<new_safe>), it might be too late when you already
830	the size before you accept the string.	1196	have it in memory, so you might want to check the size before you accept
		1197	the string.
831		1198
		1199	As for encoding, it is possible to construct data structures that are
		1200	relatively small but result in large CBOR texts (for example by having an
		1201	array full of references to the same big data structure, which will all be
		1202	deep-cloned during encoding by default). This is rarely an actual issue
		1203	(and the worst case is still just running out of memory), but you can
		1204	reduce this risk by using C<allow_sharing>.
		1205
		1206	=item Resource-starving attacks: stack overflows
		1207
832	Third, CBOR::XS recurses using the C stack when decoding objects and	1208	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	1209	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	1210	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	1211	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	1212	temporary). If that is exceeded, the program crashes. To be conservative,
837	conservative, the default nesting limit is set to 512. If your process	1213	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	1214	stack, you should adjust this setting accordingly with the C<max_depth>
839	C<max_depth> method.	1215	method.
		1216
		1217	=item Resource-starving attacks: CPU en-/decoding complexity
		1218
		1219	CBOR::XS will use the L<Math::BigInt>, L<Math::BigFloat> and
		1220	L<Math::BigRat> libraries to represent encode/decode bignums. These can be
		1221	very slow (as in, centuries of CPU time) and can even crash your program
		1222	(and are generally not very trustworthy). See the next section on bignum
		1223	security for details.
		1224
		1225	=item Data breaches: leaking information in error messages
		1226
		1227	CBOR::XS might leak contents of your Perl data structures in its error
		1228	messages, so when you serialise sensitive information you might want to
		1229	make sure that exceptions thrown by CBOR::XS will not end up in front of
		1230	untrusted eyes.
		1231
		1232	=item Something else...
840		1233
841	Something else could bomb you, too, that I forgot to think of. In that	1234	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...	1235	case, you get to keep the pieces. I am always open for hints, though...
843		1236
844	Also keep in mind that CBOR::XS might leak contents of your Perl data	1237	=back
845	structures in its error messages, so when you serialise sensitive	1238
846	information you might want to make sure that exceptions thrown by CBOR::XS	1239
847	will not end up in front of untrusted eyes.	1240	=head1 BIGNUM SECURITY CONSIDERATIONS
		1241
		1242	CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and
		1243	L<Math::BigFloat> that tries to encode the number in the simplest possible
		1244	way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
		1245	4) or an arbitrary-exponent decimal fraction (tag 264). Rational numbers
		1246	(L<Math::BigRat>, tag 30) can also contain bignums as members.
		1247
		1248	CBOR::XS will also understand base-2 bigfloat or arbitrary-exponent
		1249	bigfloats (tags 5 and 265), but it will never generate these on its own.
		1250
		1251	Using the built-in L<Math::BigInt::Calc> support, encoding and decoding
		1252	decimal fractions is generally fast. Decoding bigints can be slow for very
		1253	big numbers (tens of thousands of digits, something that could potentially
		1254	be caught by limiting the size of CBOR texts), and decoding bigfloats or
		1255	arbitrary-exponent bigfloats can be I<extremely> slow (minutes, decades)
		1256	for large exponents (roughly 40 bit and longer).
		1257
		1258	Additionally, L<Math::BigInt> can take advantage of other bignum
		1259	libraries, such as L<Math::GMP>, which cannot handle big floats with large
		1260	exponents, and might simply abort or crash your program, due to their code
		1261	quality.
		1262
		1263	This can be a concern if you want to parse untrusted CBOR. If it is, you
		1264	might want to disable decoding of tag 2 (bigint) and 3 (negative bigint)
		1265	types. You should also disable types 5 and 265, as these can be slow even
		1266	without bigints.
		1267
		1268	Disabling bigints will also partially or fully disable types that rely on
		1269	them, e.g. rational numbers that use bignums.
		1270
848		1271
849	=head1 CBOR IMPLEMENTATION NOTES	1272	=head1 CBOR IMPLEMENTATION NOTES
850		1273
851	This section contains some random implementation notes. They do not	1274	This section contains some random implementation notes. They do not
852	describe guaranteed behaviour, but merely behaviour as-is implemented	1275	describe guaranteed behaviour, but merely behaviour as-is implemented
…		…
861	Only the double data type is supported for NV data types - when Perl uses	1284	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	1285	long double to represent floating point values, they might not be encoded
863	properly. Half precision types are accepted, but not encoded.	1286	properly. Half precision types are accepted, but not encoded.
864		1287
865	Strict mode and canonical mode are not implemented.	1288	Strict mode and canonical mode are not implemented.
		1289
		1290
		1291	=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
		1292
		1293	On perls that were built without 64 bit integer support (these are rare
		1294	nowadays, even on 32 bit architectures, as all major Perl distributions
		1295	are built with 64 bit integer support), support for any kind of 64 bit
		1296	value in CBOR is very limited - most likely, these 64 bit values will
		1297	be truncated, corrupted, or otherwise not decoded correctly. This also
		1298	includes string, float, array and map sizes that are stored as 64 bit
		1299	integers.
866		1300
867		1301
868	=head1 THREADS	1302	=head1 THREADS
869		1303
870	This module is I<not> guaranteed to be thread safe and there are no	1304	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	1318	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.	1319	service. I put the contact address into my modules for a reason.
886		1320
887	=cut	1321	=cut
888		1322
		1323	# clumsy and slow hv_store-in-hash helper function
		1324	sub _hv_store {
		1325	$_[0]{$_[1]} = $_[2];
		1326	}
		1327
889	our %FILTER = (	1328	our %FILTER = (
890	# 0 # rfc4287 datetime, utf-8	1329	0 => sub { # rfc4287 datetime, utf-8
891	# 1 # unix timestamp, any	1330	require Time::Piece;
		1331	# Time::Piece::Strptime uses the "incredibly flexible date parsing routine"
		1332	# from FreeBSD, which can't parse ISO 8601, RFC3339, RFC4287 or much of anything
		1333	# else either. Whats incredibe over standard strptime totally escapes me.
		1334	# doesn't do fractional times, either. sigh.
		1335	# In fact, it's all a lie, it uses whatever strptime it wants, and of course,
		1336	# they are all incompatible. The openbsd one simply ignores %z (but according to the
		1337	# docs, it would be much more incredibly flexible indeed. If it worked, that is.).
		1338	scalar eval {
		1339	my $s = $_[1];
		1340
		1341	$s =~ s/Z$/+00:00/;
		1342	$s =~ s/(\.[0-9]+)?([+-][0-9][0-9]):([0-9][0-9])$//
		1343	or die;
		1344
		1345	my $b = $1 - ($2 * 60 + $3) * 60; # fractional part + offset. hopefully
		1346	my $d = Time::Piece->strptime ($s, "%Y-%m-%dT%H:%M:%S");
		1347
		1348	Time::Piece::gmtime ($d->epoch + $b)
		1349	} \|\| die "corrupted CBOR date/time string ($_[0])";
		1350	},
		1351
		1352	1 => sub { # seconds since the epoch, possibly fractional
		1353	require Time::Piece;
		1354	scalar Time::Piece::gmtime (pop)
		1355	},
892		1356
893	2 => sub { # pos bigint	1357	2 => sub { # pos bigint
894	require Math::BigInt;	1358	require Math::BigInt;
895	Math::BigInt->new ("0x" . unpack "H*", pop)	1359	Math::BigInt->new ("0x" . unpack "H*", pop)
896	},	1360	},
…		…
903	4 => sub { # decimal fraction, array	1367	4 => sub { # decimal fraction, array
904	require Math::BigFloat;	1368	require Math::BigFloat;
905	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])	1369	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
906	},	1370	},
907		1371
		1372	264 => sub { # decimal fraction with arbitrary exponent
		1373	require Math::BigFloat;
		1374	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
		1375	},
		1376
908	5 => sub { # bigfloat, array	1377	5 => sub { # bigfloat, array
909	require Math::BigFloat;	1378	require Math::BigFloat;
910	scalar Math::BigFloat->new ($_[1][1])->blsft ($_[1][0], 2)	1379	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1380	},
		1381
		1382	265 => sub { # bigfloat with arbitrary exponent
		1383	require Math::BigFloat;
		1384	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1385	},
		1386
		1387	30 => sub { # rational number
		1388	require Math::BigRat;
		1389	Math::BigRat->new ("$_[1][0]/$_[1][1]") # separate parameters only work in recent versons
911	},	1390	},
912		1391
913	21 => sub { pop }, # expected conversion to base64url encoding	1392	21 => sub { pop }, # expected conversion to base64url encoding
914	22 => sub { pop }, # expected conversion to base64 encoding	1393	22 => sub { pop }, # expected conversion to base64 encoding
915	23 => sub { pop }, # expected conversion to base16 encoding	1394	23 => sub { pop }, # expected conversion to base16 encoding
…		…
925	# 34 # base64 rfc46484, utf-8	1404	# 34 # base64 rfc46484, utf-8
926	# 35 # regex pcre/ecma262, utf-8	1405	# 35 # regex pcre/ecma262, utf-8
927	# 36 # mime message rfc2045, utf-8	1406	# 36 # mime message rfc2045, utf-8
928	);	1407	);
929		1408
930	sub CBOR::XS::default_filter {	1409	sub default_filter {
931	&{ $FILTER{$_[0]} or return }	1410	&{ $FILTER{$_[0]} or return }
		1411	}
		1412
		1413	our %SAFE_FILTER = map { $_ => $FILTER{$_} } 0, 1, 21, 22, 23, 32;
		1414
		1415	sub safe_filter {
		1416	&{ $SAFE_FILTER{$_[0]} or return }
932	}	1417	}
933		1418
934	sub URI::TO_CBOR {	1419	sub URI::TO_CBOR {
935	my $uri = $_[0]->as_string;	1420	my $uri = $_[0]->as_string;
936	utf8::upgrade $uri;	1421	utf8::upgrade $uri;
937	CBOR::XS::tag 32, $uri	1422	tag 32, $uri
938	}	1423	}
939		1424
940	sub Math::BigInt::TO_CBOR {	1425	sub Math::BigInt::TO_CBOR {
941	if ($_[0] >= -2147483648 && $_[0] <= 2147483647) {	1426	if (-2147483648 <= $_[0] && $_[0] <= 2147483647) {
942	$_[0]->numify	1427	$_[0]->numify
943	} else {	1428	} else {
944	my $hex = substr $_[0]->as_hex, 2;	1429	my $hex = substr $_[0]->as_hex, 2;
945	$hex = "0$hex" if 1 & length $hex; # sigh	1430	$hex = "0$hex" if 1 & length $hex; # sigh
946	CBOR::XS::tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex	1431	tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
947	}	1432	}
948	}	1433	}
949		1434
950	sub Math::BigFloat::TO_CBOR {	1435	sub Math::BigFloat::TO_CBOR {
951	my ($m, $e) = $_[0]->parts;	1436	my ($m, $e) = $_[0]->parts;
		1437
		1438	-9223372036854775808 <= $e && $e <= 18446744073709551615
952	CBOR::XS::tag 4, [$e->numify, $m]	1439	? tag 4, [$e->numify, $m]
		1440	: tag 264, [$e, $m]
		1441	}
		1442
		1443	sub Math::BigRat::TO_CBOR {
		1444	my ($n, $d) = $_[0]->parts;
		1445
		1446	# older versions of BigRat need *1, as they not always return numbers
		1447
		1448	$d*1 == 1
		1449	? $n*1
		1450	: tag 30, [$n1, $d1]
		1451	}
		1452
		1453	sub Time::Piece::TO_CBOR {
		1454	tag 1, 0 + $_[0]->epoch
953	}	1455	}
954		1456
955	XSLoader::load "CBOR::XS", $VERSION;	1457	XSLoader::load "CBOR::XS", $VERSION;
956		1458
957	=head1 SEE ALSO	1459	=head1 SEE ALSO

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing CBOR-XS/XS.pm (file contents): Revision 1.24 by root, Fri Nov 22 16:18:59 2013 UTC vs. Revision 1.71 by root, Sun Nov 29 21:32:01 2020 UTC

Diff Legend

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.24 by root, Fri Nov 22 16:18:59 2013 UTC vs.
Revision 1.71 by root, Sun Nov 29 21:32:01 2020 UTC