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

Comparing CBOR-XS/XS.pm (file contents):
Revision 1.67 by root, Thu Nov 15 19:52:41 2018 UTC vs.
Revision 1.71 by root, Sun Nov 29 21:32:01 2020 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
…		…
51		54
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
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		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
…		…
215	(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
216	resulting data structure might be unusable.	216	resulting data structure might be unusable.
217		217
218	Detecting shared values incurs a runtime overhead when values are encoded	218	Detecting shared values incurs a runtime overhead when values are encoded
219	that have a reference counter large than one, and might unnecessarily	219	that have a reference counter large than one, and might unnecessarily
220	increase the encoded size, as potentially shared values are encode as	220	increase the encoded size, as potentially shared values are encoded as
221	shareable whether or not they are actually shared.	221	shareable whether or not they are actually shared.
222		222
223	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,
224	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
225	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
…		…
330	strings as CBOR byte strings.	330	strings as CBOR byte strings.
331		331
332	This option does not affect C<decode> in any way.	332	This option does not affect C<decode> in any way.
333		333
334	This option has similar advantages and disadvantages as C<text_keys>. In	334	This option has similar advantages and disadvantages as C<text_keys>. In
335	addition, this option effectively removes the ability to encode byte	335	addition, this option effectively removes the ability to automatically
336	strings, which might break some C<FREEZE> and C<TO_CBOR> methods that rely	336	encode byte strings, which might break some C<FREEZE> and C<TO_CBOR>
337	on this, such as bignum encoding, so this option is mainly useful for very	337	methods that rely on this.
338	simple data.	338
		339	A workaround is to use explicit type casts, which are unaffected by this option.
339		340
340	=item $cbor = $cbor->validate_utf8 ([$enable])	341	=item $cbor = $cbor->validate_utf8 ([$enable])
341		342
342	=item $enabled = $cbor->get_validate_utf8	343	=item $enabled = $cbor->get_validate_utf8
343		344
…		…
453	when there is trailing garbage after the CBOR string, it will silently	454	when there is trailing garbage after the CBOR string, it will silently
454	stop parsing there and return the number of characters consumed so far.	455	stop parsing there and return the number of characters consumed so far.
455		456
456	This is useful if your CBOR texts are not delimited by an outer protocol	457	This is useful if your CBOR texts are not delimited by an outer protocol
457	and you need to know where the first CBOR string ends amd the next one	458	and you need to know where the first CBOR string ends amd the next one
458	starts.	459	starts - CBOR strings are self-delimited, so it is possible to concatenate
		460	CBOR strings without any delimiters or size fields and recover their data.
459		461
460	CBOR::XS->new->decode_prefix ("......")	462	CBOR::XS->new->decode_prefix ("......")
461	=> ("...", 3)	463	=> ("...", 3)
462		464
463	=back	465	=back
…		…
667	"$x"; # stringified	669	"$x"; # stringified
668	$x .= ""; # another, more awkward way to stringify	670	$x .= ""; # another, more awkward way to stringify
669	print $x; # perl does it for you, too, quite often	671	print $x; # perl does it for you, too, quite often
670		672
671	You can force whether a string is encoded as byte or text string by using	673	You can force whether a string is encoded as byte or text string by using
672	C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled):	674	C<utf8::upgrade> and C<utf8::downgrade> (if C<text_strings> is disabled).
673		675
674	utf8::upgrade $x; # encode $x as text string	676	utf8::upgrade $x; # encode $x as text string
675	utf8::downgrade $x; # encode $x as byte 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.
676		681
677	Perl doesn't define what operations up- and downgrade strings, so if the	682	Perl doesn't define what operations up- and downgrade strings, so if the
678	difference between byte and text is important, you should up- or downgrade	683	difference between byte and text is important, you should up- or downgrade
679	your string as late as possible before encoding. You can also force the	684	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>.	685	use of CBOR text strings by using C<text_keys> or C<text_strings>.
…		…
695	format will be used. Perls that use formats other than IEEE double to	700	format will be used. Perls that use formats other than IEEE double to
696	represent numerical values are supported, but might suffer loss of	701	represent numerical values are supported, but might suffer loss of
697	precision.	702	precision.
698		703
699	=back	704	=back
		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:: }
700		764
701	=head2 OBJECT SERIALISATION	765	=head2 OBJECT SERIALISATION
702		766
703	This module implements both a CBOR-specific and the generic	767	This module implements both a CBOR-specific and the generic
704	L<Types::Serialier> object serialisation protocol. The following	768	L<Types::Serialier> object serialisation protocol. The following
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1057		1121
1058		1122
1059	=head1 SECURITY CONSIDERATIONS	1123	=head1 SECURITY CONSIDERATIONS
1060		1124
1061	Tl;dr... if you want to decode or encode CBOR from untrusted sources, you	1125	Tl;dr... if you want to decode or encode CBOR from untrusted sources, you
1062	should start with a coder object created via C<new_safe>:	1126	should start with a coder object created via C<new_safe> (which implements
		1127	the mitigations explained below):
1063		1128
1064	my $coder = CBOR::XS->new_safe;	1129	my $coder = CBOR::XS->new_safe;
1065		1130
1066	my $data = $coder->decode ($cbor_text);	1131	my $data = $coder->decode ($cbor_text);
1067	my $cbor = $coder->encode ($data);	1132	my $cbor = $coder->encode ($data);
…		…
1089	even if all your C<THAW> methods are secure, encoding data structures from	1154	even if all your C<THAW> methods are secure, encoding data structures from
1090	untrusted sources can invoke those and trigger bugs in those.	1155	untrusted sources can invoke those and trigger bugs in those.
1091		1156
1092	So, if you are not sure about the security of all the modules you	1157	So, if you are not sure about the security of all the modules you
1093	have loaded (you shouldn't), you should disable this part using	1158	have loaded (you shouldn't), you should disable this part using
1094	C<forbid_objects>.	1159	C<forbid_objects> or using C<new_safe>.
1095		1160
1096	=item CBOR can be extended with tags that call library code	1161	=item CBOR can be extended with tags that call library code
1097		1162
1098	CBOR can be extended with tags, and C<CBOR::XS> has a registry of	1163	CBOR can be extended with tags, and C<CBOR::XS> has a registry of
1099	conversion functions for many existing tags that can be extended via	1164	conversion functions for many existing tags that can be extended via
1100	third-party modules (see the C<filter> method).	1165	third-party modules (see the C<filter> method).
1101		1166
1102	If you don't trust these, you should configure the "safe" filter function,	1167	If you don't trust these, you should configure the "safe" filter function,
1103	C<CBOR::XS::safe_filter>, which by default only includes conversion	1168	C<CBOR::XS::safe_filter> (C<new_safe> does this), which by default only
1104	functions that are considered "safe" by the author (but again, they can be	1169	includes conversion functions that are considered "safe" by the author
1105	extended by third party modules).	1170	(but again, they can be extended by third party modules).
1106		1171
1107	Depending on your level of paranoia, you can use the "safe" filter:	1172	Depending on your level of paranoia, you can use the "safe" filter:
1108		1173
1109	$cbor->filter (\&CBOR::XS::safe_filter);	1174	$cbor->filter (\&CBOR::XS::safe_filter);
1110		1175
…		…
1125	the size of CBOR data you accept, or make sure then when your resources	1190	the size of CBOR data you accept, or make sure then when your resources
1126	run out, that's just fine (e.g. by using a separate process that can	1191	run out, that's just fine (e.g. by using a separate process that can
1127	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
1128	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
1129	structure. While CBOR::XS can check the size of the CBOR text (using	1194	structure. While CBOR::XS can check the size of the CBOR text (using
1130	C<max_size>), it might be too late when you already have it in memory, so	1195	C<max_size> - done by C<new_safe>), it might be too late when you already
1131	you might want to check 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.
1132		1198
1133	As for encoding, it is possible to construct data structures that are	1199	As for encoding, it is possible to construct data structures that are
1134	relatively small but result in large CBOR texts (for example by having an	1200	relatively small but result in large CBOR texts (for example by having an
1135	array full of references to the same big data structure, which will all be	1201	array full of references to the same big data structure, which will all be
1136	deep-cloned during encoding by default). This is rarely an actual issue	1202	deep-cloned during encoding by default). This is rarely an actual issue
…		…
1149	method.	1215	method.
1150		1216
1151	=item Resource-starving attacks: CPU en-/decoding complexity	1217	=item Resource-starving attacks: CPU en-/decoding complexity
1152		1218
1153	CBOR::XS will use the L<Math::BigInt>, L<Math::BigFloat> and	1219	CBOR::XS will use the L<Math::BigInt>, L<Math::BigFloat> and
1154	L<Math::BigRat> libraries to represent encode/decode bignums. These can	1220	L<Math::BigRat> libraries to represent encode/decode bignums. These can be
1155	be very slow (as in, centuries of CPU time) and can even crash your	1221	very slow (as in, centuries of CPU time) and can even crash your program
1156	program (and are generally not very trustworthy). See the next section for	1222	(and are generally not very trustworthy). See the next section on bignum
1157	details.	1223	security for details.
1158		1224
1159	=item Data breaches: leaking information in error messages	1225	=item Data breaches: leaking information in error messages
1160		1226
1161	CBOR::XS might leak contents of your Perl data structures in its error	1227	CBOR::XS might leak contents of your Perl data structures in its error
1162	messages, so when you serialise sensitive information you might want to	1228	messages, so when you serialise sensitive information you might want to
…		…
1225	=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT	1291	=head1 LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
1226		1292
1227	On perls that were built without 64 bit integer support (these are rare	1293	On perls that were built without 64 bit integer support (these are rare
1228	nowadays, even on 32 bit architectures, as all major Perl distributions	1294	nowadays, even on 32 bit architectures, as all major Perl distributions
1229	are built with 64 bit integer support), support for any kind of 64 bit	1295	are built with 64 bit integer support), support for any kind of 64 bit
1230	integer in CBOR is very limited - most likely, these 64 bit values will	1296	value in CBOR is very limited - most likely, these 64 bit values will
1231	be truncated, corrupted, or otherwise not decoded correctly. This also	1297	be truncated, corrupted, or otherwise not decoded correctly. This also
1232	includes string, array and map sizes that are stored as 64 bit integers.	1298	includes string, float, array and map sizes that are stored as 64 bit
		1299	integers.
1233		1300
1234		1301
1235	=head1 THREADS	1302	=head1 THREADS
1236		1303
1237	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

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Comparing CBOR-XS/XS.pm (file contents): Revision 1.67 by root, Thu Nov 15 19:52:41 2018 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 1.67 by root, Thu Nov 15 19:52:41 2018 UTC vs.
Revision 1.71 by root, Sun Nov 29 21:32:01 2020 UTC