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

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.51 by root, Sun Apr 24 19:16:15 2016 UTC vs.
Revision 1.69 by root, Sat Nov 9 07:23:31 2019 UTC

…		…
38	with the added ability of supporting serialisation of Perl objects. (JSON	38	with the added ability of supporting serialisation of Perl objects. (JSON
39	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
40	data later and speed is less important you might want to compare both	40	data later and speed is less important you might want to compare both
41	formats first).	41	formats first).
42		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.
		45
43	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,
44	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
45	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
46	data, the worse L<Storable> performs in comparison.	49	data, the worse L<Storable> performs in comparison.
47		50
…		…
52	In addition to the core CBOR data format, this module implements a	55	In addition to the core CBOR data format, this module implements a
53	number of extensions, to support cyclic and shared data structures	56	number of extensions, to support cyclic and shared data structures
54	(see C<allow_sharing> and C<allow_cycles>), string deduplication (see	57	(see C<allow_sharing> and C<allow_cycles>), string deduplication (see
55	C<pack_strings>) and scalar references (always enabled).	58	C<pack_strings>) and scalar references (always enabled).
56		59
57	The primary goal of this module is to be I<correct> and the secondary goal
58	is to be I<fast>. To reach the latter goal it was written in C.
59
60	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
61	vice versa.	61	vice versa.
62		62
63	=cut	63	=cut
64		64
65	package CBOR::XS;	65	package CBOR::XS;
66		66
67	use common::sense;	67	use common::sense;
68		68
69	our $VERSION = 1.41;	69	our $VERSION = 1.71;
70	our @ISA = qw(Exporter);	70	our @ISA = qw(Exporter);
71		71
72	our @EXPORT = qw(encode_cbor decode_cbor);	72	our @EXPORT = qw(encode_cbor decode_cbor);
73		73
74	use Exporter;	74	use Exporter;
…		…
112		112
113	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
114	be chained:	114	be chained:
115		115
116	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	}
117		142
118	=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])	143	=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])
119		144
120	=item $max_depth = $cbor->get_max_depth	145	=item $max_depth = $cbor->get_max_depth
121		146
…		…
137		162
138	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
139	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
140	crashing.	165	crashing.
141		166
142	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.
143		168
144	=item $cbor = $cbor->max_size ([$maximum_string_size])	169	=item $cbor = $cbor->max_size ([$maximum_string_size])
145		170
146	=item $max_size = $cbor->get_max_size	171	=item $max_size = $cbor->get_max_size
147		172
…		…
152	effect on C<encode> (yet).	177	effect on C<encode> (yet).
153		178
154	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
155	C<0> is specified).	180	C<0> is specified).
156		181
157	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.
158		183
159	=item $cbor = $cbor->allow_unknown ([$enable])	184	=item $cbor = $cbor->allow_unknown ([$enable])
160		185
161	=item $enabled = $cbor->get_allow_unknown	186	=item $enabled = $cbor->get_allow_unknown
162		187
…		…
180	reference to the earlier value.	205	reference to the earlier value.
181		206
182	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
183	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
184	sharing extension. This also makes it possible to encode cyclic data	209	sharing extension. This also makes it possible to encode cyclic data
185	structures (which need C<allow_cycles> to ne enabled to be decoded by this	210	structures (which need C<allow_cycles> to be enabled to be decoded by this
186	module).	211	module).
187		212
188	It is recommended to leave it off unless you know your	213	It is recommended to leave it off unless you know your
189	communication partner supports the value sharing extensions to CBOR	214	communication partner supports the value sharing extensions to CBOR
190	(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the	215	(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the
191	resulting data structure might be unusable.	216	resulting data structure might be unusable.
192		217
193	Detecting shared values incurs a runtime overhead when values are encoded	218	Detecting shared values incurs a runtime overhead when values are encoded
194	that have a reference counter large than one, and might unnecessarily	219	that have a reference counter large than one, and might unnecessarily
195	increase the encoded size, as potentially shared values are encode as	220	increase the encoded size, as potentially shared values are encoded as
196	shareable whether or not they are actually shared.	221	shareable whether or not they are actually shared.
197		222
198	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,
199	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
200	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
…		…
226	throwing an error.	251	throwing an error.
227		252
228	This option does not affect C<encode> in any way - shared values and	253	This option does not affect C<encode> in any way - shared values and
229	references will always be encoded properly if present.	254	references will always be encoded properly if present.
230		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
231	=item $cbor = $cbor->pack_strings ([$enable])	275	=item $cbor = $cbor->pack_strings ([$enable])
232		276
233	=item $enabled = $cbor->get_pack_strings	277	=item $enabled = $cbor->get_pack_strings
234		278
235	If C<$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
…		…
247	the standard CBOR way.	291	the standard CBOR way.
248		292
249	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
250	always be decoded properly if present.	294	always be decoded properly if present.
251		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 encode byte
		336	strings, which might break some C<FREEZE> and C<TO_CBOR> methods that rely
		337	on this, such as bignum encoding, so this option is mainly useful for very
		338	simple data.
		339
252	=item $cbor = $cbor->validate_utf8 ([$enable])	340	=item $cbor = $cbor->validate_utf8 ([$enable])
253		341
254	=item $enabled = $cbor->get_validate_utf8	342	=item $enabled = $cbor->get_validate_utf8
255		343
256	If C<$enable> is true (or missing), then C<decode> will validate that	344	If C<$enable> is true (or missing), then C<decode> will validate that
…		…
293	replace the tagged value in the decoded data structure, or no values,	381	replace the tagged value in the decoded data structure, or no values,
294	which will result in default handling, which currently means the decoder	382	which will result in default handling, which currently means the decoder
295	creates a C<CBOR::XS::Tagged> object to hold the tag and the value.	383	creates a C<CBOR::XS::Tagged> object to hold the tag and the value.
296		384
297	When the filter is cleared (the default state), the default filter	385	When the filter is cleared (the default state), the default filter
298	function, C<CBOR::XS::default_filter>, is used. This function simply looks	386	function, C<CBOR::XS::default_filter>, is used. This function simply
299	up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be	387	looks up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists
300	a code reference that is called with tag and value, and is responsible for	388	it must be a code reference that is called with tag and value, and is
301	decoding the value. If no entry exists, it returns no values.	389	responsible for decoding the value. If no entry exists, it returns no
		390	values. C<CBOR::XS> provides a number of default filter functions already,
		391	the the C<%CBOR::XS::FILTER> hash can be freely extended with more.
		392
		393	C<CBOR::XS> additionally provides an alternative filter function that is
		394	supposed to be safe to use with untrusted data (which the default filter
		395	might not), called C<CBOR::XS::safe_filter>, which works the same as
		396	the C<default_filter> but uses the C<%CBOR::XS::SAFE_FILTER> variable
		397	instead. It is prepopulated with the tag decoding functions that are
		398	deemed safe (basically the same as C<%CBOR::XS::FILTER> without all
		399	the bignum tags), and can be extended by user code as wlel, although,
		400	obviously, one should be very careful about adding decoding functions
		401	here, since the expectation is that they are safe to use on untrusted
		402	data, after all.
302		403
303	Example: decode all tags not handled internally into C<CBOR::XS::Tagged>	404	Example: decode all tags not handled internally into C<CBOR::XS::Tagged>
304	objects, with no other special handling (useful when working with	405	objects, with no other special handling (useful when working with
305	potentially "unsafe" CBOR data).	406	potentially "unsafe" CBOR data).
306		407
…		…
312	$CBOR::XS::FILTER{1347375694} = sub {	413	$CBOR::XS::FILTER{1347375694} = sub {
313	my ($tag, $value);	414	my ($tag, $value);
314		415
315	"tag 1347375694 value $value"	416	"tag 1347375694 value $value"
316	};	417	};
		418
		419	Example: provide your own filter function that looks up tags in your own
		420	hash:
		421
		422	my %my_filter = (
		423	998347484 => sub {
		424	my ($tag, $value);
		425
		426	"tag 998347484 value $value"
		427	};
		428	);
		429
		430	my $coder = CBOR::XS->new->filter (sub {
		431	&{ $my_filter{$_[0]} or return }
		432	});
		433
		434
		435	Example: use the safe filter function (see L<SECURITY CONSIDERATIONS> for
		436	more considerations on security).
		437
		438	CBOR::XS->new->filter (\&CBOR::XS::safe_filter)->decode ($cbor_data);
317		439
318	=item $cbor_data = $cbor->encode ($perl_scalar)	440	=item $cbor_data = $cbor->encode ($perl_scalar)
319		441
320	Converts the given Perl data structure (a scalar value) to its CBOR	442	Converts the given Perl data structure (a scalar value) to its CBOR
321	representation.	443	representation.
…		…
396		518
397	Resets the incremental decoder. This throws away any saved state, so that	519	Resets the incremental decoder. This throws away any saved state, so that
398	subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse	520	subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse
399	a new CBOR value from the beginning of the C<$buffer> again.	521	a new CBOR value from the beginning of the C<$buffer> again.
400		522
401	This method can be caled at any time, but it I<must> be called if you want	523	This method can be called at any time, but it I<must> be called if you want
402	to change your C<$buffer> or there was a decoding error and you want to	524	to change your C<$buffer> or there was a decoding error and you want to
403	reuse the C<$cbor> object for future incremental parsings.	525	reuse the C<$cbor> object for future incremental parsings.
404		526
405	=back	527	=back
406		528
…		…
544	my $x = 3.1; # some variable containing a number	666	my $x = 3.1; # some variable containing a number
545	"$x"; # stringified	667	"$x"; # stringified
546	$x .= ""; # another, more awkward way to stringify	668	$x .= ""; # another, more awkward way to stringify
547	print $x; # perl does it for you, too, quite often	669	print $x; # perl does it for you, too, quite often
548		670
549	You can force whether a string ie encoded as byte or text string by using	671	You can force whether a string is encoded as byte or text string by using
550	C<utf8::upgrade> and C<utf8::downgrade>):	672	C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled):
551		673
552	utf8::upgrade $x; # encode $x as text string	674	utf8::upgrade $x; # encode $x as text string
553	utf8::downgrade $x; # encode $x as byte string	675	utf8::downgrade $x; # encode $x as byte string
554		676
555	Perl doesn't define what operations up- and downgrade strings, so if the	677	Perl doesn't define what operations up- and downgrade strings, so if the
556	difference between byte and text is important, you should up- or downgrade	678	difference between byte and text is important, you should up- or downgrade
557	your string as late as possible before encoding.	679	your string as late as possible before encoding. You can also force the
		680	use of CBOR text strings by using C<text_keys> or C<text_strings>.
558		681
559	You can force the type to be a CBOR number by numifying it:	682	You can force the type to be a CBOR number by numifying it:
560		683
561	my $x = "3"; # some variable containing a string	684	my $x = "3"; # some variable containing a string
562	$x += 0; # numify it, ensuring it will be dumped as a number	685	$x += 0; # numify it, ensuring it will be dumped as a number
…		…
663	"$self" # encode url string	786	"$self" # encode url string
664	}	787	}
665		788
666	sub URI::THAW {	789	sub URI::THAW {
667	my ($class, $serialiser, $uri) = @_;	790	my ($class, $serialiser, $uri) = @_;
668
669	$class->new ($uri)	791	$class->new ($uri)
670	}	792	}
671		793
672	Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For	794	Unlike C<TO_CBOR>, multiple values can be returned by C<FREEZE>. For
673	example, a C<FREEZE> method that returns "type", "id" and "variant" values	795	example, a C<FREEZE> method that returns "type", "id" and "variant" values
…		…
883		1005
884	These tags are decoded into L<Math::BigInt> objects. The corresponding	1006	These tags are decoded into L<Math::BigInt> objects. The corresponding
885	C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR	1007	C<Math::BigInt::TO_CBOR> method encodes "small" bigints into normal CBOR
886	integers, and others into positive/negative CBOR bignums.	1008	integers, and others into positive/negative CBOR bignums.
887		1009
888	=item 4, 5 (decimal fraction/bigfloat)	1010	=item 4, 5, 264, 265 (decimal fraction/bigfloat)
889		1011
890	Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>	1012	Both decimal fractions and bigfloats are decoded into L<Math::BigFloat>
891	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>	1013	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>
892	encodes into a decimal fraction.	1014	encodes into a decimal fraction (either tag 4 or 264).
893		1015
894	CBOR cannot represent bigfloats with I<very> large exponents - conversion	1016	NaN and infinities are not encoded properly, as they cannot be represented
895	of such big float objects is undefined.	1017	in CBOR.
896		1018
897	Also, NaN and infinities are not encoded properly.	1019	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
		1020
		1021	=item 30 (rational numbers)
		1022
		1023	These tags are decoded into L<Math::BigRat> objects. The corresponding
		1024	C<Math::BigRat::TO_CBOR> method encodes rational numbers with denominator
		1025	C<1> via their numerator only, i.e., they become normal integers or
		1026	C<bignums>.
		1027
		1028	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
898		1029
899	=item 21, 22, 23 (expected later JSON conversion)	1030	=item 21, 22, 23 (expected later JSON conversion)
900		1031
901	CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these	1032	CBOR::XS is not a CBOR-to-JSON converter, and will simply ignore these
902	tags.	1033	tags.
…		…
925	CBOR intact.	1056	CBOR intact.
926		1057
927		1058
928	=head1 SECURITY CONSIDERATIONS	1059	=head1 SECURITY CONSIDERATIONS
929		1060
930	When you are using CBOR in a protocol, talking to untrusted potentially	1061	Tl;dr... if you want to decode or encode CBOR from untrusted sources, you
931	hostile creatures requires relatively few measures.	1062	should start with a coder object created via C<new_safe> (which implements
		1063	the mitigations explained below):
932		1064
		1065	my $coder = CBOR::XS->new_safe;
		1066
		1067	my $data = $coder->decode ($cbor_text);
		1068	my $cbor = $coder->encode ($data);
		1069
		1070	Longer version: When you are using CBOR in a protocol, talking to
		1071	untrusted potentially hostile creatures requires some thought:
		1072
		1073	=over 4
		1074
		1075	=item Security of the CBOR decoder itself
		1076
933	First of all, your CBOR decoder should be secure, that is, should not have	1077	First and foremost, your CBOR decoder should be secure, that is, should
		1078	not have any buffer overflows or similar bugs that could potentially be
934	any buffer overflows. Obviously, this module should ensure that and I am	1079	exploited. Obviously, this module should ensure that and I am trying hard
935	trying hard on making that true, but you never know.	1080	on making that true, but you never know.
936		1081
		1082	=item CBOR::XS can invoke almost arbitrary callbacks during decoding
		1083
		1084	CBOR::XS supports object serialisation - decoding CBOR can cause calls
		1085	to I<any> C<THAW> method in I<any> package that exists in your process
		1086	(that is, CBOR::XS will not try to load modules, but any existing C<THAW>
		1087	method or function can be called, so they all have to be secure).
		1088
		1089	Less obviously, it will also invoke C<TO_CBOR> and C<FREEZE> methods -
		1090	even if all your C<THAW> methods are secure, encoding data structures from
		1091	untrusted sources can invoke those and trigger bugs in those.
		1092
		1093	So, if you are not sure about the security of all the modules you
		1094	have loaded (you shouldn't), you should disable this part using
		1095	C<forbid_objects> or using C<new_safe>.
		1096
		1097	=item CBOR can be extended with tags that call library code
		1098
		1099	CBOR can be extended with tags, and C<CBOR::XS> has a registry of
		1100	conversion functions for many existing tags that can be extended via
		1101	third-party modules (see the C<filter> method).
		1102
		1103	If you don't trust these, you should configure the "safe" filter function,
		1104	C<CBOR::XS::safe_filter> (C<new_safe> does this), which by default only
		1105	includes conversion functions that are considered "safe" by the author
		1106	(but again, they can be extended by third party modules).
		1107
		1108	Depending on your level of paranoia, you can use the "safe" filter:
		1109
		1110	$cbor->filter (\&CBOR::XS::safe_filter);
		1111
		1112	... your own filter...
		1113
		1114	$cbor->filter (sub { ... do your stuffs here ... });
		1115
		1116	... or even no filter at all, disabling all tag decoding:
		1117
		1118	$cbor->filter (sub { });
		1119
		1120	This is never a problem for encoding, as the tag mechanism only exists in
		1121	CBOR texts.
		1122
		1123	=item Resource-starving attacks: object memory usage
		1124
937	Second, you need to avoid resource-starving attacks. That means you should	1125	You need to avoid resource-starving attacks. That means you should limit
938	limit the size of CBOR data you accept, or make sure then when your	1126	the size of CBOR data you accept, or make sure then when your resources
939	resources run out, that's just fine (e.g. by using a separate process that	1127	run out, that's just fine (e.g. by using a separate process that can
940	can crash safely). The size of a CBOR string in octets is usually a good	1128	crash safely). The size of a CBOR string in octets is usually a good
941	indication of the size of the resources required to decode it into a Perl	1129	indication of the size of the resources required to decode it into a Perl
942	structure. While CBOR::XS can check the size of the CBOR text, it might be	1130	structure. While CBOR::XS can check the size of the CBOR text (using
943	too late when you already have it in memory, so you might want to check	1131	C<max_size> - done by C<new_safe>), it might be too late when you already
944	the size before you accept the string.	1132	have it in memory, so you might want to check the size before you accept
		1133	the string.
945		1134
		1135	As for encoding, it is possible to construct data structures that are
		1136	relatively small but result in large CBOR texts (for example by having an
		1137	array full of references to the same big data structure, which will all be
		1138	deep-cloned during encoding by default). This is rarely an actual issue
		1139	(and the worst case is still just running out of memory), but you can
		1140	reduce this risk by using C<allow_sharing>.
		1141
		1142	=item Resource-starving attacks: stack overflows
		1143
946	Third, CBOR::XS recurses using the C stack when decoding objects and	1144	CBOR::XS recurses using the C stack when decoding objects and arrays. The
947	arrays. The C stack is a limited resource: for instance, on my amd64	1145	C stack is a limited resource: for instance, on my amd64 machine with 8MB
948	machine with 8MB of stack size I can decode around 180k nested arrays but	1146	of stack size I can decode around 180k nested arrays but only 14k nested
949	only 14k nested CBOR objects (due to perl itself recursing deeply on croak	1147	CBOR objects (due to perl itself recursing deeply on croak to free the
950	to free the temporary). If that is exceeded, the program crashes. To be	1148	temporary). If that is exceeded, the program crashes. To be conservative,
951	conservative, the default nesting limit is set to 512. If your process	1149	the default nesting limit is set to 512. If your process has a smaller
952	has a smaller stack, you should adjust this setting accordingly with the	1150	stack, you should adjust this setting accordingly with the C<max_depth>
953	C<max_depth> method.	1151	method.
		1152
		1153	=item Resource-starving attacks: CPU en-/decoding complexity
		1154
		1155	CBOR::XS will use the L<Math::BigInt>, L<Math::BigFloat> and
		1156	L<Math::BigRat> libraries to represent encode/decode bignums. These can be
		1157	very slow (as in, centuries of CPU time) and can even crash your program
		1158	(and are generally not very trustworthy). See the next section on bignum
		1159	security for details.
		1160
		1161	=item Data breaches: leaking information in error messages
		1162
		1163	CBOR::XS might leak contents of your Perl data structures in its error
		1164	messages, so when you serialise sensitive information you might want to
		1165	make sure that exceptions thrown by CBOR::XS will not end up in front of
		1166	untrusted eyes.
		1167
		1168	=item Something else...
954		1169
955	Something else could bomb you, too, that I forgot to think of. In that	1170	Something else could bomb you, too, that I forgot to think of. In that
956	case, you get to keep the pieces. I am always open for hints, though...	1171	case, you get to keep the pieces. I am always open for hints, though...
957		1172
958	Also keep in mind that CBOR::XS might leak contents of your Perl data	1173	=back
959	structures in its error messages, so when you serialise sensitive	1174
960	information you might want to make sure that exceptions thrown by CBOR::XS	1175
961	will not end up in front of untrusted eyes.	1176	=head1 BIGNUM SECURITY CONSIDERATIONS
		1177
		1178	CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and
		1179	L<Math::BigFloat> that tries to encode the number in the simplest possible
		1180	way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
		1181	4) or an arbitrary-exponent decimal fraction (tag 264). Rational numbers
		1182	(L<Math::BigRat>, tag 30) can also contain bignums as members.
		1183
		1184	CBOR::XS will also understand base-2 bigfloat or arbitrary-exponent
		1185	bigfloats (tags 5 and 265), but it will never generate these on its own.
		1186
		1187	Using the built-in L<Math::BigInt::Calc> support, encoding and decoding
		1188	decimal fractions is generally fast. Decoding bigints can be slow for very
		1189	big numbers (tens of thousands of digits, something that could potentially
		1190	be caught by limiting the size of CBOR texts), and decoding bigfloats or
		1191	arbitrary-exponent bigfloats can be I<extremely> slow (minutes, decades)
		1192	for large exponents (roughly 40 bit and longer).
		1193
		1194	Additionally, L<Math::BigInt> can take advantage of other bignum
		1195	libraries, such as L<Math::GMP>, which cannot handle big floats with large
		1196	exponents, and might simply abort or crash your program, due to their code
		1197	quality.
		1198
		1199	This can be a concern if you want to parse untrusted CBOR. If it is, you
		1200	might want to disable decoding of tag 2 (bigint) and 3 (negative bigint)
		1201	types. You should also disable types 5 and 265, as these can be slow even
		1202	without bigints.
		1203
		1204	Disabling bigints will also partially or fully disable types that rely on
		1205	them, e.g. rational numbers that use bignums.
		1206
962		1207
963	=head1 CBOR IMPLEMENTATION NOTES	1208	=head1 CBOR IMPLEMENTATION NOTES
964		1209
965	This section contains some random implementation notes. They do not	1210	This section contains some random implementation notes. They do not
966	describe guaranteed behaviour, but merely behaviour as-is implemented	1211	describe guaranteed behaviour, but merely behaviour as-is implemented
…		…
1007		1252
1008	Please refrain from using rt.cpan.org or any other bug reporting	1253	Please refrain from using rt.cpan.org or any other bug reporting
1009	service. I put the contact address into my modules for a reason.	1254	service. I put the contact address into my modules for a reason.
1010		1255
1011	=cut	1256	=cut
		1257
		1258	# clumsy and slow hv_store-in-hash helper function
		1259	sub _hv_store {
		1260	$_[0]{$_[1]} = $_[2];
		1261	}
1012		1262
1013	our %FILTER = (	1263	our %FILTER = (
1014	0 => sub { # rfc4287 datetime, utf-8	1264	0 => sub { # rfc4287 datetime, utf-8
1015	require Time::Piece;	1265	require Time::Piece;
1016	# Time::Piece::Strptime uses the "incredibly flexible date parsing routine"	1266	# Time::Piece::Strptime uses the "incredibly flexible date parsing routine"
…		…
1052	4 => sub { # decimal fraction, array	1302	4 => sub { # decimal fraction, array
1053	require Math::BigFloat;	1303	require Math::BigFloat;
1054	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])	1304	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
1055	},	1305	},
1056		1306
		1307	264 => sub { # decimal fraction with arbitrary exponent
		1308	require Math::BigFloat;
		1309	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
		1310	},
		1311
1057	5 => sub { # bigfloat, array	1312	5 => sub { # bigfloat, array
1058	require Math::BigFloat;	1313	require Math::BigFloat;
1059	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])	1314	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1315	},
		1316
		1317	265 => sub { # bigfloat with arbitrary exponent
		1318	require Math::BigFloat;
		1319	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1320	},
		1321
		1322	30 => sub { # rational number
		1323	require Math::BigRat;
		1324	Math::BigRat->new ("$_[1][0]/$_[1][1]") # separate parameters only work in recent versons
1060	},	1325	},
1061		1326
1062	21 => sub { pop }, # expected conversion to base64url encoding	1327	21 => sub { pop }, # expected conversion to base64url encoding
1063	22 => sub { pop }, # expected conversion to base64 encoding	1328	22 => sub { pop }, # expected conversion to base64 encoding
1064	23 => sub { pop }, # expected conversion to base16 encoding	1329	23 => sub { pop }, # expected conversion to base16 encoding
…		…
1074	# 34 # base64 rfc46484, utf-8	1339	# 34 # base64 rfc46484, utf-8
1075	# 35 # regex pcre/ecma262, utf-8	1340	# 35 # regex pcre/ecma262, utf-8
1076	# 36 # mime message rfc2045, utf-8	1341	# 36 # mime message rfc2045, utf-8
1077	);	1342	);
1078		1343
1079	sub CBOR::XS::default_filter {	1344	sub default_filter {
1080	&{ $FILTER{$_[0]} or return }	1345	&{ $FILTER{$_[0]} or return }
		1346	}
		1347
		1348	our %SAFE_FILTER = map { $_ => $FILTER{$_} } 0, 1, 21, 22, 23, 32;
		1349
		1350	sub safe_filter {
		1351	&{ $SAFE_FILTER{$_[0]} or return }
1081	}	1352	}
1082		1353
1083	sub URI::TO_CBOR {	1354	sub URI::TO_CBOR {
1084	my $uri = $_[0]->as_string;	1355	my $uri = $_[0]->as_string;
1085	utf8::upgrade $uri;	1356	utf8::upgrade $uri;
1086	tag 32, $uri	1357	tag 32, $uri
1087	}	1358	}
1088		1359
1089	sub Math::BigInt::TO_CBOR {	1360	sub Math::BigInt::TO_CBOR {
1090	if ($_[0] >= -2147483648 && $_[0] <= 2147483647) {	1361	if (-2147483648 <= $_[0] && $_[0] <= 2147483647) {
1091	$_[0]->numify	1362	$_[0]->numify
1092	} else {	1363	} else {
1093	my $hex = substr $_[0]->as_hex, 2;	1364	my $hex = substr $_[0]->as_hex, 2;
1094	$hex = "0$hex" if 1 & length $hex; # sigh	1365	$hex = "0$hex" if 1 & length $hex; # sigh
1095	tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex	1366	tag $_[0] >= 0 ? 2 : 3, pack "H*", $hex
1096	}	1367	}
1097	}	1368	}
1098		1369
1099	sub Math::BigFloat::TO_CBOR {	1370	sub Math::BigFloat::TO_CBOR {
1100	my ($m, $e) = $_[0]->parts;	1371	my ($m, $e) = $_[0]->parts;
		1372
		1373	-9223372036854775808 <= $e && $e <= 18446744073709551615
1101	tag 4, [$e->numify, $m]	1374	? tag 4, [$e->numify, $m]
		1375	: tag 264, [$e, $m]
		1376	}
		1377
		1378	sub Math::BigRat::TO_CBOR {
		1379	my ($n, $d) = $_[0]->parts;
		1380
		1381	# older versions of BigRat need *1, as they not always return numbers
		1382
		1383	$d*1 == 1
		1384	? $n*1
		1385	: tag 30, [$n1, $d1]
1102	}	1386	}
1103		1387
1104	sub Time::Piece::TO_CBOR {	1388	sub Time::Piece::TO_CBOR {
1105	tag 1, 0 + $_[0]->epoch	1389	tag 1, 0 + $_[0]->epoch
1106	}	1390	}

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Comparing CBOR-XS/XS.pm (file contents): Revision 1.51 by root, Sun Apr 24 19:16:15 2016 UTC vs. Revision 1.69 by root, Sat Nov 9 07:23:31 2019 UTC

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Comparing CBOR-XS/XS.pm (file contents):
Revision 1.51 by root, Sun Apr 24 19:16:15 2016 UTC vs.
Revision 1.69 by root, Sat Nov 9 07:23:31 2019 UTC