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

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.56 by root, Mon Apr 25 21:44:13 2016 UTC vs.
Revision 1.85 by root, Thu Nov 4 16:49:35 2021 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 = 1.5;	69	our $VERSION = 1.86;
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	->validate_utf8
		127	->forbid_objects
		128	->filter (\&CBOR::XS::safe_filter)
		129	->max_size (1e8);
		130
		131	But is more future proof (it is better to crash because of a change than
		132	to be exploited in other ways).
		133
		134	=cut
		135
		136	sub new_safe {
		137	CBOR::XS
		138	->new
		139	->validate_utf8
		140	->forbid_objects
		141	->filter (\&CBOR::XS::safe_filter)
		142	->max_size (1e8)
		143	}
117		144
118	=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])	145	=item $cbor = $cbor->max_depth ([$maximum_nesting_depth])
119		146
120	=item $max_depth = $cbor->get_max_depth	147	=item $max_depth = $cbor->get_max_depth
121		148
…		…
137		164
138	Note that nesting is implemented by recursion in C. The default value has	165	Note that nesting is implemented by recursion in C. The default value has
139	been chosen to be as large as typical operating systems allow without	166	been chosen to be as large as typical operating systems allow without
140	crashing.	167	crashing.
141		168
142	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	169	See L<SECURITY CONSIDERATIONS>, below, for more info on why this is useful.
143		170
144	=item $cbor = $cbor->max_size ([$maximum_string_size])	171	=item $cbor = $cbor->max_size ([$maximum_string_size])
145		172
146	=item $max_size = $cbor->get_max_size	173	=item $max_size = $cbor->get_max_size
147		174
…		…
152	effect on C<encode> (yet).	179	effect on C<encode> (yet).
153		180
154	If no argument is given, the limit check will be deactivated (same as when	181	If no argument is given, the limit check will be deactivated (same as when
155	C<0> is specified).	182	C<0> is specified).
156		183
157	See SECURITY CONSIDERATIONS, below, for more info on why this is useful.	184	See L<SECURITY CONSIDERATIONS>, below, for more info on why this is useful.
158		185
159	=item $cbor = $cbor->allow_unknown ([$enable])	186	=item $cbor = $cbor->allow_unknown ([$enable])
160		187
161	=item $enabled = $cbor->get_allow_unknown	188	=item $enabled = $cbor->get_allow_unknown
162		189
…		…
180	reference to the earlier value.	207	reference to the earlier value.
181		208
182	This means that such values will only be encoded once, and will not result	209	This means that such values will only be encoded once, and will not result
183	in a deep cloning of the value on decode, in decoders supporting the value	210	in a deep cloning of the value on decode, in decoders supporting the value
184	sharing extension. This also makes it possible to encode cyclic data	211	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	212	structures (which need C<allow_cycles> to be enabled to be decoded by this
186	module).	213	module).
187		214
188	It is recommended to leave it off unless you know your	215	It is recommended to leave it off unless you know your
189	communication partner supports the value sharing extensions to CBOR	216	communication partner supports the value sharing extensions to CBOR
190	(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the	217	(L<http://cbor.schmorp.de/value-sharing>), as without decoder support, the
191	resulting data structure might be unusable.	218	resulting data structure might be unusable.
192		219
193	Detecting shared values incurs a runtime overhead when values are encoded	220	Detecting shared values incurs a runtime overhead when values are encoded
194	that have a reference counter large than one, and might unnecessarily	221	that have a reference counter large than one, and might unnecessarily
195	increase the encoded size, as potentially shared values are encode as	222	increase the encoded size, as potentially shared values are encoded as
196	shareable whether or not they are actually shared.	223	shareable whether or not they are actually shared.
197		224
198	At the moment, only targets of references can be shared (e.g. scalars,	225	At the moment, only targets of references can be shared (e.g. scalars,
199	arrays or hashes pointed to by a reference). Weirder constructs, such as	226	arrays or hashes pointed to by a reference). Weirder constructs, such as
200	an array with multiple "copies" of the I<same> string, which are hard but	227	an array with multiple "copies" of the I<same> string, which are hard but
…		…
226	throwing an error.	253	throwing an error.
227		254
228	This option does not affect C<encode> in any way - shared values and	255	This option does not affect C<encode> in any way - shared values and
229	references will always be encoded properly if present.	256	references will always be encoded properly if present.
230		257
		258	=item $cbor = $cbor->forbid_objects ([$enable])
		259
		260	=item $enabled = $cbor->get_forbid_objects
		261
		262	Disables the use of the object serialiser protocol.
		263
		264	If C<$enable> is true (or missing), then C<encode> will will throw an
		265	exception when it encounters perl objects that would be encoded using the
		266	perl-object tag (26). When C<decode> encounters such tags, it will fall
		267	back to the general filter/tagged logic as if this were an unknown tag (by
		268	default resulting in a C<CBOR::XC::Tagged> object).
		269
		270	If C<$enable> is false (the default), then C<encode> will use the
		271	L<Types::Serialiser> object serialisation protocol to serialise objects
		272	into perl-object tags, and C<decode> will do the same to decode such tags.
		273
		274	See L<SECURITY CONSIDERATIONS>, below, for more info on why forbidding this
		275	protocol can be useful.
		276
231	=item $cbor = $cbor->pack_strings ([$enable])	277	=item $cbor = $cbor->pack_strings ([$enable])
232		278
233	=item $enabled = $cbor->get_pack_strings	279	=item $enabled = $cbor->get_pack_strings
234		280
235	If C<$enable> is true (or missing), then C<encode> will try not to encode	281	If C<$enable> is true (or missing), then C<encode> will try not to encode
…		…
286	strings as CBOR byte strings.	332	strings as CBOR byte strings.
287		333
288	This option does not affect C<decode> in any way.	334	This option does not affect C<decode> in any way.
289		335
290	This option has similar advantages and disadvantages as C<text_keys>. In	336	This option has similar advantages and disadvantages as C<text_keys>. In
291	addition, this option effectively removes the ability to encode byte	337	addition, this option effectively removes the ability to automatically
292	strings, which might break some C<FREEZE> and C<TO_CBOR> methods that rely	338	encode byte strings, which might break some C<FREEZE> and C<TO_CBOR>
293	on this, such as bignum encoding, so this option is mainly useful for very	339	methods that rely on this.
294	simple data.	340
		341	A workaround is to use explicit type casts, which are unaffected by this option.
295		342
296	=item $cbor = $cbor->validate_utf8 ([$enable])	343	=item $cbor = $cbor->validate_utf8 ([$enable])
297		344
298	=item $enabled = $cbor->get_validate_utf8	345	=item $enabled = $cbor->get_validate_utf8
299		346
…		…
337	replace the tagged value in the decoded data structure, or no values,	384	replace the tagged value in the decoded data structure, or no values,
338	which will result in default handling, which currently means the decoder	385	which will result in default handling, which currently means the decoder
339	creates a C<CBOR::XS::Tagged> object to hold the tag and the value.	386	creates a C<CBOR::XS::Tagged> object to hold the tag and the value.
340		387
341	When the filter is cleared (the default state), the default filter	388	When the filter is cleared (the default state), the default filter
342	function, C<CBOR::XS::default_filter>, is used. This function simply looks	389	function, C<CBOR::XS::default_filter>, is used. This function simply
343	up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists it must be	390	looks up the tag in the C<%CBOR::XS::FILTER> hash. If an entry exists
344	a code reference that is called with tag and value, and is responsible for	391	it must be a code reference that is called with tag and value, and is
345	decoding the value. If no entry exists, it returns no values.	392	responsible for decoding the value. If no entry exists, it returns no
		393	values. C<CBOR::XS> provides a number of default filter functions already,
		394	the the C<%CBOR::XS::FILTER> hash can be freely extended with more.
		395
		396	C<CBOR::XS> additionally provides an alternative filter function that is
		397	supposed to be safe to use with untrusted data (which the default filter
		398	might not), called C<CBOR::XS::safe_filter>, which works the same as
		399	the C<default_filter> but uses the C<%CBOR::XS::SAFE_FILTER> variable
		400	instead. It is prepopulated with the tag decoding functions that are
		401	deemed safe (basically the same as C<%CBOR::XS::FILTER> without all
		402	the bignum tags), and can be extended by user code as wlel, although,
		403	obviously, one should be very careful about adding decoding functions
		404	here, since the expectation is that they are safe to use on untrusted
		405	data, after all.
346		406
347	Example: decode all tags not handled internally into C<CBOR::XS::Tagged>	407	Example: decode all tags not handled internally into C<CBOR::XS::Tagged>
348	objects, with no other special handling (useful when working with	408	objects, with no other special handling (useful when working with
349	potentially "unsafe" CBOR data).	409	potentially "unsafe" CBOR data).
350		410
…		…
357	my ($tag, $value);	417	my ($tag, $value);
358		418
359	"tag 1347375694 value $value"	419	"tag 1347375694 value $value"
360	};	420	};
361		421
		422	Example: provide your own filter function that looks up tags in your own
		423	hash:
		424
		425	my %my_filter = (
		426	998347484 => sub {
		427	my ($tag, $value);
		428
		429	"tag 998347484 value $value"
		430	};
		431	);
		432
		433	my $coder = CBOR::XS->new->filter (sub {
		434	&{ $my_filter{$_[0]} or return }
		435	});
		436
		437
		438	Example: use the safe filter function (see L<SECURITY CONSIDERATIONS> for
		439	more considerations on security).
		440
		441	CBOR::XS->new->filter (\&CBOR::XS::safe_filter)->decode ($cbor_data);
		442
362	=item $cbor_data = $cbor->encode ($perl_scalar)	443	=item $cbor_data = $cbor->encode ($perl_scalar)
363		444
364	Converts the given Perl data structure (a scalar value) to its CBOR	445	Converts the given Perl data structure (a scalar value) to its CBOR
365	representation.	446	representation.
366		447
…		…
375	when there is trailing garbage after the CBOR string, it will silently	456	when there is trailing garbage after the CBOR string, it will silently
376	stop parsing there and return the number of characters consumed so far.	457	stop parsing there and return the number of characters consumed so far.
377		458
378	This is useful if your CBOR texts are not delimited by an outer protocol	459	This is useful if your CBOR texts are not delimited by an outer protocol
379	and you need to know where the first CBOR string ends amd the next one	460	and you need to know where the first CBOR string ends amd the next one
380	starts.	461	starts - CBOR strings are self-delimited, so it is possible to concatenate
		462	CBOR strings without any delimiters or size fields and recover their data.
381		463
382	CBOR::XS->new->decode_prefix ("......")	464	CBOR::XS->new->decode_prefix ("......")
383	=> ("...", 3)	465	=> ("...", 3)
384		466
385	=back	467	=back
…		…
440		522
441	Resets the incremental decoder. This throws away any saved state, so that	523	Resets the incremental decoder. This throws away any saved state, so that
442	subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse	524	subsequent calls to C<incr_parse> or C<incr_parse_multiple> start to parse
443	a new CBOR value from the beginning of the C<$buffer> again.	525	a new CBOR value from the beginning of the C<$buffer> again.
444		526
445	This method can be caled at any time, but it I<must> be called if you want	527	This method can be called at any time, but it I<must> be called if you want
446	to change your C<$buffer> or there was a decoding error and you want to	528	to change your C<$buffer> or there was a decoding error and you want to
447	reuse the C<$cbor> object for future incremental parsings.	529	reuse the C<$cbor> object for future incremental parsings.
448		530
449	=back	531	=back
450		532
…		…
589	"$x"; # stringified	671	"$x"; # stringified
590	$x .= ""; # another, more awkward way to stringify	672	$x .= ""; # another, more awkward way to stringify
591	print $x; # perl does it for you, too, quite often	673	print $x; # perl does it for you, too, quite often
592		674
593	You can force whether a string is encoded as byte or text string by using	675	You can force whether a string is encoded as byte or text string by using
594	C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled):	676	C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled).
595		677
596	utf8::upgrade $x; # encode $x as text string	678	utf8::upgrade $x; # encode $x as text string
597	utf8::downgrade $x; # encode $x as byte string	679	utf8::downgrade $x; # encode $x as byte string
		680
		681	More options are available, see L<TYPE CASTS>, below, and the C<text_keys>
		682	and C<text_strings> options.
598		683
599	Perl doesn't define what operations up- and downgrade strings, so if the	684	Perl doesn't define what operations up- and downgrade strings, so if the
600	difference between byte and text is important, you should up- or downgrade	685	difference between byte and text is important, you should up- or downgrade
601	your string as late as possible before encoding. You can also force the	686	your string as late as possible before encoding. You can also force the
602	use of CBOR text strings by using C<text_keys> or C<text_strings>.	687	use of CBOR text strings by using C<text_keys> or C<text_strings>.
…		…
618	represent numerical values are supported, but might suffer loss of	703	represent numerical values are supported, but might suffer loss of
619	precision.	704	precision.
620		705
621	=back	706	=back
622		707
		708	=head2 TYPE CASTS
		709
		710	B<EXPERIMENTAL>: As an experimental extension, C<CBOR::XS> allows you to
		711	force specific CBOR types to be used when encoding. That allows you to
		712	encode types not normally accessible (e.g. half floats) as well as force
		713	string types even when C<text_strings> is in effect.
		714
		715	Type forcing is done by calling a special "cast" function which keeps a
		716	copy of the value and returns a new value that can be handed over to any
		717	CBOR encoder function.
		718
		719	The following casts are currently available (all of which are unary
		720	operators, that is, have a prototype of C<$>):
		721
		722	=over
		723
		724	=item CBOR::XS::as_int $value
		725
		726	Forces the value to be encoded as some form of (basic, not bignum) integer
		727	type.
		728
		729	=item CBOR::XS::as_text $value
		730
		731	Forces the value to be encoded as (UTF-8) text values.
		732
		733	=item CBOR::XS::as_bytes $value
		734
		735	Forces the value to be encoded as a (binary) string value.
		736
		737	Example: encode a perl string as binary even though C<text_strings> is in
		738	effect.
		739
		740	CBOR::XS->new->text_strings->encode ([4, "text", CBOR::XS::bytes "bytevalue"]);
		741
		742	=item CBOR::XS::as_bool $value
		743
		744	Converts a Perl boolean (which can be any kind of scalar) into a CBOR
		745	boolean. Strictly the same, but shorter to write, than:
		746
		747	$value ? Types::Serialiser::true : Types::Serialiser::false
		748
		749	=item CBOR::XS::as_float16 $value
		750
		751	Forces half-float (IEEE 754 binary16) encoding of the given value.
		752
		753	=item CBOR::XS::as_float32 $value
		754
		755	Forces single-float (IEEE 754 binary32) encoding of the given value.
		756
		757	=item CBOR::XS::as_float64 $value
		758
		759	Forces double-float (IEEE 754 binary64) encoding of the given value.
		760
		761	=item CBOR::XS::as_cbor $cbor_text
		762
		763	Not a type cast per-se, this type cast forces the argument to be encoded
		764	as-is. This can be used to embed pre-encoded CBOR data.
		765
		766	Note that no checking on the validity of the C<$cbor_text> is done - it's
		767	the callers responsibility to correctly encode values.
		768
		769	=item CBOR::XS::as_map [key => value...]
		770
		771	Treat the array reference as key value pairs and output a CBOR map. This
		772	allows you to generate CBOR maps with arbitrary key types (or, if you
		773	don't care about semantics, duplicate keys or pairs in a custom order),
		774	which is otherwise hard to do with Perl.
		775
		776	The single argument must be an array reference with an even number of
		777	elements.
		778
		779	Note that only the reference to the array is copied, the array itself is
		780	not. Modifications done to the array before calling an encoding function
		781	will be reflected in the encoded output.
		782
		783	Example: encode a CBOR map with a string and an integer as keys.
		784
		785	encode_cbor CBOR::XS::as_map [string => "value", 5 => "value"]
		786
		787	=back
		788
		789	=cut
		790
		791	sub CBOR::XS::as_cbor ($) { bless [$_[0], 0, undef], CBOR::XS::Tagged:: }
		792	sub CBOR::XS::as_int ($) { bless [$_[0], 1, undef], CBOR::XS::Tagged:: }
		793	sub CBOR::XS::as_bytes ($) { bless [$_[0], 2, undef], CBOR::XS::Tagged:: }
		794	sub CBOR::XS::as_text ($) { bless [$_[0], 3, undef], CBOR::XS::Tagged:: }
		795	sub CBOR::XS::as_float16 ($) { bless [$_[0], 4, undef], CBOR::XS::Tagged:: }
		796	sub CBOR::XS::as_float32 ($) { bless [$_[0], 5, undef], CBOR::XS::Tagged:: }
		797	sub CBOR::XS::as_float64 ($) { bless [$_[0], 6, undef], CBOR::XS::Tagged:: }
		798
		799	sub CBOR::XS::as_bool ($) { $_[0] ? $Types::Serialiser::true : $Types::Serialiser::false }
		800
		801	sub CBOR::XS::as_map ($) {
		802	ARRAY:: eq ref $_[0]
		803	and $#{ $_[0] } & 1
		804	or do { require Carp; Carp::croak ("CBOR::XS::as_map only acepts array references with an even number of elements, caught") };
		805
		806	bless [$_[0], 7, undef], CBOR::XS::Tagged::
		807	}
		808
623	=head2 OBJECT SERIALISATION	809	=head2 OBJECT SERIALISATION
624		810
625	This module implements both a CBOR-specific and the generic	811	This module implements both a CBOR-specific and the generic
626	L<Types::Serialier> object serialisation protocol. The following	812	L<Types::Serialier> object serialisation protocol. The following
627	subsections explain both methods.	813	subsections explain both methods.
…		…
935	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>	1121	objects. The corresponding C<Math::BigFloat::TO_CBOR> method I<always>
936	encodes into a decimal fraction (either tag 4 or 264).	1122	encodes into a decimal fraction (either tag 4 or 264).
937		1123
938	NaN and infinities are not encoded properly, as they cannot be represented	1124	NaN and infinities are not encoded properly, as they cannot be represented
939	in CBOR.	1125	in CBOR.
		1126
		1127	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
		1128
		1129	=item 30 (rational numbers)
		1130
		1131	These tags are decoded into L<Math::BigRat> objects. The corresponding
		1132	C<Math::BigRat::TO_CBOR> method encodes rational numbers with denominator
		1133	C<1> via their numerator only, i.e., they become normal integers or
		1134	C<bignums>.
940		1135
941	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.	1136	See L<BIGNUM SECURITY CONSIDERATIONS> for more info.
942		1137
943	=item 21, 22, 23 (expected later JSON conversion)	1138	=item 21, 22, 23 (expected later JSON conversion)
944		1139
…		…
969	CBOR intact.	1164	CBOR intact.
970		1165
971		1166
972	=head1 SECURITY CONSIDERATIONS	1167	=head1 SECURITY CONSIDERATIONS
973		1168
974	When you are using CBOR in a protocol, talking to untrusted potentially	1169	Tl;dr... if you want to decode or encode CBOR from untrusted sources, you
975	hostile creatures requires relatively few measures.	1170	should start with a coder object created via C<new_safe> (which implements
		1171	the mitigations explained below):
976		1172
		1173	my $coder = CBOR::XS->new_safe;
		1174
		1175	my $data = $coder->decode ($cbor_text);
		1176	my $cbor = $coder->encode ($data);
		1177
		1178	Longer version: When you are using CBOR in a protocol, talking to
		1179	untrusted potentially hostile creatures requires some thought:
		1180
		1181	=over 4
		1182
		1183	=item Security of the CBOR decoder itself
		1184
977	First of all, your CBOR decoder should be secure, that is, should not have	1185	First and foremost, your CBOR decoder should be secure, that is, should
		1186	not have any buffer overflows or similar bugs that could potentially be
978	any buffer overflows. Obviously, this module should ensure that and I am	1187	exploited. Obviously, this module should ensure that and I am trying hard
979	trying hard on making that true, but you never know.	1188	on making that true, but you never know.
980		1189
		1190	=item CBOR::XS can invoke almost arbitrary callbacks during decoding
		1191
		1192	CBOR::XS supports object serialisation - decoding CBOR can cause calls
		1193	to I<any> C<THAW> method in I<any> package that exists in your process
		1194	(that is, CBOR::XS will not try to load modules, but any existing C<THAW>
		1195	method or function can be called, so they all have to be secure).
		1196
		1197	Less obviously, it will also invoke C<TO_CBOR> and C<FREEZE> methods -
		1198	even if all your C<THAW> methods are secure, encoding data structures from
		1199	untrusted sources can invoke those and trigger bugs in those.
		1200
		1201	So, if you are not sure about the security of all the modules you
		1202	have loaded (you shouldn't), you should disable this part using
		1203	C<forbid_objects> or using C<new_safe>.
		1204
		1205	=item CBOR can be extended with tags that call library code
		1206
		1207	CBOR can be extended with tags, and C<CBOR::XS> has a registry of
		1208	conversion functions for many existing tags that can be extended via
		1209	third-party modules (see the C<filter> method).
		1210
		1211	If you don't trust these, you should configure the "safe" filter function,
		1212	C<CBOR::XS::safe_filter> (C<new_safe> does this), which by default only
		1213	includes conversion functions that are considered "safe" by the author
		1214	(but again, they can be extended by third party modules).
		1215
		1216	Depending on your level of paranoia, you can use the "safe" filter:
		1217
		1218	$cbor->filter (\&CBOR::XS::safe_filter);
		1219
		1220	... your own filter...
		1221
		1222	$cbor->filter (sub { ... do your stuffs here ... });
		1223
		1224	... or even no filter at all, disabling all tag decoding:
		1225
		1226	$cbor->filter (sub { });
		1227
		1228	This is never a problem for encoding, as the tag mechanism only exists in
		1229	CBOR texts.
		1230
		1231	=item Resource-starving attacks: object memory usage
		1232
981	Second, you need to avoid resource-starving attacks. That means you should	1233	You need to avoid resource-starving attacks. That means you should limit
982	limit the size of CBOR data you accept, or make sure then when your	1234	the size of CBOR data you accept, or make sure then when your resources
983	resources run out, that's just fine (e.g. by using a separate process that	1235	run out, that's just fine (e.g. by using a separate process that can
984	can crash safely). The size of a CBOR string in octets is usually a good	1236	crash safely). The size of a CBOR string in octets is usually a good
985	indication of the size of the resources required to decode it into a Perl	1237	indication of the size of the resources required to decode it into a Perl
986	structure. While CBOR::XS can check the size of the CBOR text, it might be	1238	structure. While CBOR::XS can check the size of the CBOR text (using
987	too late when you already have it in memory, so you might want to check	1239	C<max_size> - done by C<new_safe>), it might be too late when you already
988	the size before you accept the string.	1240	have it in memory, so you might want to check the size before you accept
		1241	the string.
989		1242
		1243	As for encoding, it is possible to construct data structures that are
		1244	relatively small but result in large CBOR texts (for example by having an
		1245	array full of references to the same big data structure, which will all be
		1246	deep-cloned during encoding by default). This is rarely an actual issue
		1247	(and the worst case is still just running out of memory), but you can
		1248	reduce this risk by using C<allow_sharing>.
		1249
		1250	=item Resource-starving attacks: stack overflows
		1251
990	Third, CBOR::XS recurses using the C stack when decoding objects and	1252	CBOR::XS recurses using the C stack when decoding objects and arrays. The
991	arrays. The C stack is a limited resource: for instance, on my amd64	1253	C stack is a limited resource: for instance, on my amd64 machine with 8MB
992	machine with 8MB of stack size I can decode around 180k nested arrays but	1254	of stack size I can decode around 180k nested arrays but only 14k nested
993	only 14k nested CBOR objects (due to perl itself recursing deeply on croak	1255	CBOR objects (due to perl itself recursing deeply on croak to free the
994	to free the temporary). If that is exceeded, the program crashes. To be	1256	temporary). If that is exceeded, the program crashes. To be conservative,
995	conservative, the default nesting limit is set to 512. If your process	1257	the default nesting limit is set to 512. If your process has a smaller
996	has a smaller stack, you should adjust this setting accordingly with the	1258	stack, you should adjust this setting accordingly with the C<max_depth>
997	C<max_depth> method.	1259	method.
		1260
		1261	=item Resource-starving attacks: CPU en-/decoding complexity
		1262
		1263	CBOR::XS will use the L<Math::BigInt>, L<Math::BigFloat> and
		1264	L<Math::BigRat> libraries to represent encode/decode bignums. These can be
		1265	very slow (as in, centuries of CPU time) and can even crash your program
		1266	(and are generally not very trustworthy). See the next section on bignum
		1267	security for details.
		1268
		1269	=item Data breaches: leaking information in error messages
		1270
		1271	CBOR::XS might leak contents of your Perl data structures in its error
		1272	messages, so when you serialise sensitive information you might want to
		1273	make sure that exceptions thrown by CBOR::XS will not end up in front of
		1274	untrusted eyes.
		1275
		1276	=item Something else...
998		1277
999	Something else could bomb you, too, that I forgot to think of. In that	1278	Something else could bomb you, too, that I forgot to think of. In that
1000	case, you get to keep the pieces. I am always open for hints, though...	1279	case, you get to keep the pieces. I am always open for hints, though...
1001		1280
1002	Also keep in mind that CBOR::XS might leak contents of your Perl data	1281	=back
1003	structures in its error messages, so when you serialise sensitive
1004	information you might want to make sure that exceptions thrown by CBOR::XS
1005	will not end up in front of untrusted eyes.
1006		1282
1007		1283
1008	=head1 BIGNUM SECURITY CONSIDERATIONS	1284	=head1 BIGNUM SECURITY CONSIDERATIONS
1009		1285
1010	CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and	1286	CBOR::XS provides a C<TO_CBOR> method for both L<Math::BigInt> and
1011	L<Math::BigFloat> that tries to encode the number in the simplest possible	1287	L<Math::BigFloat> that tries to encode the number in the simplest possible
1012	way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag	1288	way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
1013	4) or an arbitrary-exponent decimal fraction (tag 264).	1289	4) or an arbitrary-exponent decimal fraction (tag 264). Rational numbers
		1290	(L<Math::BigRat>, tag 30) can also contain bignums as members.
1014		1291
1015	It will also understand base-2 bigfloat or arbitrary-exponent bigfloats	1292	CBOR::XS will also understand base-2 bigfloat or arbitrary-exponent
1016	(tags 5 and 265), but it will never generate these on its own.	1293	bigfloats (tags 5 and 265), but it will never generate these on its own.
1017		1294
1018	Using the built-in L<Math::BigInt::Calc> support, encoding and decoding	1295	Using the built-in L<Math::BigInt::Calc> support, encoding and decoding
1019	decimal fractions is generally fast. Decoding bigints can be slow for very	1296	decimal fractions is generally fast. Decoding bigints can be slow for very
1020	big numbers, and decoding bigfloats or arbitrary-exponent bigfloats can be	1297	big numbers (tens of thousands of digits, something that could potentially
1021	extremely slow (minutes, decades) for large exponents.	1298	be caught by limiting the size of CBOR texts), and decoding bigfloats or
		1299	arbitrary-exponent bigfloats can be I<extremely> slow (minutes, decades)
		1300	for large exponents (roughly 40 bit and longer).
1022		1301
1023	Additionally, L<Math::BigInt> can take advantage of other bignum	1302	Additionally, L<Math::BigInt> can take advantage of other bignum
1024	libraries, such as L<Math::GMP>, which cannot handle big	1303	libraries, such as L<Math::GMP>, which cannot handle big floats with large
1025	floats with large exponents, and might simply abort or crash your program,	1304	exponents, and might simply abort or crash your program, due to their code
1026	due to their code quality.	1305	quality.
1027		1306
1028	This can be a concern if you want to parse untrusted CBOR. If it is, you	1307	This can be a concern if you want to parse untrusted CBOR. If it is, you
1029	need to disable decoding of tag 2 (bigint) and 3 (negative bigint) types,	1308	might want to disable decoding of tag 2 (bigint) and 3 (negative bigint)
1030	which will also disable bigfloat support (to be sure, you can also disable	1309	types. You should also disable types 5 and 265, as these can be slow even
1031	types 4, 5, 264 and 265).	1310	without bigints.
		1311
		1312	Disabling bigints will also partially or fully disable types that rely on
		1313	them, e.g. rational numbers that use bignums.
1032		1314
1033		1315
1034	=head1 CBOR IMPLEMENTATION NOTES	1316	=head1 CBOR IMPLEMENTATION NOTES
1035		1317
1036	This section contains some random implementation notes. They do not	1318	This section contains some random implementation notes. They do not
…		…
1053	=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT	1335	=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
1054		1336
1055	On perls that were built without 64 bit integer support (these are rare	1337	On perls that were built without 64 bit integer support (these are rare
1056	nowadays, even on 32 bit architectures, as all major Perl distributions	1338	nowadays, even on 32 bit architectures, as all major Perl distributions
1057	are built with 64 bit integer support), support for any kind of 64 bit	1339	are built with 64 bit integer support), support for any kind of 64 bit
1058	integer in CBOR is very limited - most likely, these 64 bit values will	1340	value in CBOR is very limited - most likely, these 64 bit values will
1059	be truncated, corrupted, or otherwise not decoded correctly. This also	1341	be truncated, corrupted, or otherwise not decoded correctly. This also
1060	includes string, array and map sizes that are stored as 64 bit integers.	1342	includes string, float, array and map sizes that are stored as 64 bit
		1343	integers.
1061		1344
1062		1345
1063	=head1 THREADS	1346	=head1 THREADS
1064		1347
1065	This module is I<not> guaranteed to be thread safe and there are no	1348	This module is I<not> guaranteed to be thread safe and there are no
…		…
1078		1361
1079	Please refrain from using rt.cpan.org or any other bug reporting	1362	Please refrain from using rt.cpan.org or any other bug reporting
1080	service. I put the contact address into my modules for a reason.	1363	service. I put the contact address into my modules for a reason.
1081		1364
1082	=cut	1365	=cut
		1366
		1367	# clumsy and slow hv_store-in-hash helper function
		1368	sub _hv_store {
		1369	$_[0]{$_[1]} = $_[2];
		1370	}
1083		1371
1084	our %FILTER = (	1372	our %FILTER = (
1085	0 => sub { # rfc4287 datetime, utf-8	1373	0 => sub { # rfc4287 datetime, utf-8
1086	require Time::Piece;	1374	require Time::Piece;
1087	# Time::Piece::Strptime uses the "incredibly flexible date parsing routine"	1375	# Time::Piece::Strptime uses the "incredibly flexible date parsing routine"
…		…
1110	scalar Time::Piece::gmtime (pop)	1398	scalar Time::Piece::gmtime (pop)
1111	},	1399	},
1112		1400
1113	2 => sub { # pos bigint	1401	2 => sub { # pos bigint
1114	require Math::BigInt;	1402	require Math::BigInt;
1115	Math::BigInt->from_hex ("0x" . unpack "H*", pop)	1403	Math::BigInt->new ("0x" . unpack "H*", pop)
1116	},	1404	},
1117		1405
1118	3 => sub { # neg bigint	1406	3 => sub { # neg bigint
1119	require Math::BigInt;	1407	require Math::BigInt;
1120	-Math::BigInt->from_hex ("0x" . unpack "H*", pop)	1408	-Math::BigInt->new ("0x" . unpack "H*", pop)
1121	},	1409	},
1122		1410
1123	4 => sub { # decimal fraction, array	1411	4 => sub { # decimal fraction, array
1124	require Math::BigFloat;	1412	require Math::BigFloat;
1125	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])	1413	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
1126	},	1414	},
1127		1415
		1416	264 => sub { # decimal fraction with arbitrary exponent
		1417	require Math::BigFloat;
		1418	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
		1419	},
		1420
1128	5 => sub { # bigfloat, array	1421	5 => sub { # bigfloat, array
1129	require Math::BigFloat;	1422	require Math::BigFloat;
1130	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])	1423	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
1131	},	1424	},
1132		1425
		1426	265 => sub { # bigfloat with arbitrary exponent
		1427	require Math::BigFloat;
		1428	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
		1429	},
		1430
		1431	30 => sub { # rational number
		1432	require Math::BigRat;
		1433	Math::BigRat->new ("$_[1][0]/$_[1][1]") # separate parameters only work in recent versons
		1434	},
		1435
1133	21 => sub { pop }, # expected conversion to base64url encoding	1436	21 => sub { pop }, # expected conversion to base64url encoding
1134	22 => sub { pop }, # expected conversion to base64 encoding	1437	22 => sub { pop }, # expected conversion to base64 encoding
1135	23 => sub { pop }, # expected conversion to base16 encoding	1438	23 => sub { pop }, # expected conversion to base16 encoding
1136		1439
1137	# 24 # embedded cbor, byte string	1440	# 24 # embedded cbor, byte string
…		…
1143		1446
1144	# 33 # base64url rfc4648, utf-8	1447	# 33 # base64url rfc4648, utf-8
1145	# 34 # base64 rfc46484, utf-8	1448	# 34 # base64 rfc46484, utf-8
1146	# 35 # regex pcre/ecma262, utf-8	1449	# 35 # regex pcre/ecma262, utf-8
1147	# 36 # mime message rfc2045, utf-8	1450	# 36 # mime message rfc2045, utf-8
1148
1149	264 => sub { # decimal fraction with arbitrary exponent
1150	require Math::BigFloat;
1151	Math::BigFloat->new ($_[1][1] . "E" . $_[1][0])
1152	},
1153
1154	265 => sub { # bigfloat with arbitrary exponent
1155	require Math::BigFloat;
1156	scalar Math::BigFloat->new ($_[1][1]) * Math::BigFloat->new (2)->bpow ($_[1][0])
1157	},
1158	);	1451	);
1159		1452
1160	sub CBOR::XS::default_filter {	1453	sub default_filter {
1161	&{ $FILTER{$_[0]} or return }	1454	&{ $FILTER{$_[0]} or return }
		1455	}
		1456
		1457	our %SAFE_FILTER = map { $_ => $FILTER{$_} } 0, 1, 21, 22, 23, 32;
		1458
		1459	sub safe_filter {
		1460	&{ $SAFE_FILTER{$_[0]} or return }
1162	}	1461	}
1163		1462
1164	sub URI::TO_CBOR {	1463	sub URI::TO_CBOR {
1165	my $uri = $_[0]->as_string;	1464	my $uri = $_[0]->as_string;
1166	utf8::upgrade $uri;	1465	utf8::upgrade $uri;
…		…
1183	-9223372036854775808 <= $e && $e <= 18446744073709551615	1482	-9223372036854775808 <= $e && $e <= 18446744073709551615
1184	? tag 4, [$e->numify, $m]	1483	? tag 4, [$e->numify, $m]
1185	: tag 264, [$e, $m]	1484	: tag 264, [$e, $m]
1186	}	1485	}
1187		1486
		1487	sub Math::BigRat::TO_CBOR {
		1488	my ($n, $d) = $_[0]->parts;
		1489
		1490	# older versions of BigRat need *1, as they not always return numbers
		1491
		1492	$d*1 == 1
		1493	? $n*1
		1494	: tag 30, [$n1, $d1]
		1495	}
		1496
1188	sub Time::Piece::TO_CBOR {	1497	sub Time::Piece::TO_CBOR {
1189	tag 1, 0 + $_[0]->epoch	1498	tag 1, 0 + $_[0]->epoch
1190	}	1499	}
1191		1500
1192	XSLoader::load "CBOR::XS", $VERSION;	1501	XSLoader::load "CBOR::XS", $VERSION;

Diff Legend

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

Comparing CBOR-XS/XS.pm (file contents): Revision 1.56 by root, Mon Apr 25 21:44:13 2016 UTC vs. Revision 1.85 by root, Thu Nov 4 16:49:35 2021 UTC

Diff Legend

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.56 by root, Mon Apr 25 21:44:13 2016 UTC vs.
Revision 1.85 by root, Thu Nov 4 16:49:35 2021 UTC