[ViewVC] Diff of: cvs/CBOR-XS/README

Comparing CBOR-XS/README (file contents):
Revision 1.17 by root, Wed Apr 27 09:40:18 2016 UTC vs.
Revision 1.22 by root, Thu Oct 21 01:14:58 2021 UTC

…		…
33	with the added ability of supporting serialisation of Perl objects.	33	with the added ability of supporting serialisation of Perl objects.
34	(JSON often compresses better than CBOR though, so if you plan to	34	(JSON often compresses better than CBOR though, so if you plan to
35	compress the data later and speed is less important you might want to	35	compress the data later and speed is less important you might want to
36	compare both formats first).	36	compare both formats first).
37		37
		38	The primary goal of this module is to be correct and the secondary
		39	goal is to be fast. To reach the latter goal it was written in C.
		40
38	To give you a general idea about speed, with texts in the megabyte	41	To give you a general idea about speed, with texts in the megabyte
39	range, "CBOR::XS" usually encodes roughly twice as fast as Storable or	42	range, "CBOR::XS" usually encodes roughly twice as fast as Storable or
40	JSON::XS and decodes about 15%-30% faster than those. The shorter the	43	JSON::XS and decodes about 15%-30% faster than those. The shorter the
41	data, the worse Storable performs in comparison.	44	data, the worse Storable performs in comparison.
42		45
…		…
47	In addition to the core CBOR data format, this module implements a	50	In addition to the core CBOR data format, this module implements a
48	number of extensions, to support cyclic and shared data structures (see	51	number of extensions, to support cyclic and shared data structures (see
49	"allow_sharing" and "allow_cycles"), string deduplication (see	52	"allow_sharing" and "allow_cycles"), string deduplication (see
50	"pack_strings") and scalar references (always enabled).	53	"pack_strings") and scalar references (always enabled).
51		54
52	The primary goal of this module is to be correct and the secondary
53	goal is to be fast. To reach the latter goal it was written in C.
54
55	See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and	55	See MAPPING, below, on how CBOR::XS maps perl values to CBOR values and
56	vice versa.	56	vice versa.
57		57
58	FUNCTIONAL INTERFACE	58	FUNCTIONAL INTERFACE
59	The following convenience methods are provided by this module. They are	59	The following convenience methods are provided by this module. They are
…		…
78		78
79	The mutators for flags all return the CBOR object again and thus	79	The mutators for flags all return the CBOR object again and thus
80	calls can be chained:	80	calls can be chained:
81		81
82	my $cbor = CBOR::XS->new->encode ({a => [1,2]});	82	my $cbor = CBOR::XS->new->encode ({a => [1,2]});
		83
		84	$cbor = new_safe CBOR::XS
		85	Create a new, safe/secure CBOR::XS object. This is similar to "new",
		86	but configures the coder object to be safe to use with untrusted
		87	data. Currently, this is equivalent to:
		88
		89	my $cbor = CBOR::XS
		90	->new
		91	->validate_utf8
		92	->forbid_objects
		93	->filter (\&CBOR::XS::safe_filter)
		94	->max_size (1e8);
		95
		96	But is more future proof (it is better to crash because of a change
		97	than to be exploited in other ways).
83		98
84	$cbor = $cbor->max_depth ([$maximum_nesting_depth])	99	$cbor = $cbor->max_depth ([$maximum_nesting_depth])
85	$max_depth = $cbor->get_max_depth	100	$max_depth = $cbor->get_max_depth
86	Sets the maximum nesting level (default 512) accepted while encoding	101	Sets the maximum nesting level (default 512) accepted while encoding
87	or decoding. If a higher nesting level is detected in CBOR data or a	102	or decoding. If a higher nesting level is detected in CBOR data or a
…		…
101		116
102	Note that nesting is implemented by recursion in C. The default	117	Note that nesting is implemented by recursion in C. The default
103	value has been chosen to be as large as typical operating systems	118	value has been chosen to be as large as typical operating systems
104	allow without crashing.	119	allow without crashing.
105		120
106	See SECURITY CONSIDERATIONS, below, for more info on why this is	121	See "SECURITY CONSIDERATIONS", below, for more info on why this is
107	useful.	122	useful.
108		123
109	$cbor = $cbor->max_size ([$maximum_string_size])	124	$cbor = $cbor->max_size ([$maximum_string_size])
110	$max_size = $cbor->get_max_size	125	$max_size = $cbor->get_max_size
111	Set the maximum length a CBOR string may have (in bytes) where	126	Set the maximum length a CBOR string may have (in bytes) where
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115	exception. This setting has no effect on "encode" (yet).	130	exception. This setting has no effect on "encode" (yet).
116		131
117	If no argument is given, the limit check will be deactivated (same	132	If no argument is given, the limit check will be deactivated (same
118	as when 0 is specified).	133	as when 0 is specified).
119		134
120	See SECURITY CONSIDERATIONS, below, for more info on why this is	135	See "SECURITY CONSIDERATIONS", below, for more info on why this is
121	useful.	136	useful.
122		137
123	$cbor = $cbor->allow_unknown ([$enable])	138	$cbor = $cbor->allow_unknown ([$enable])
124	$enabled = $cbor->get_allow_unknown	139	$enabled = $cbor->get_allow_unknown
125	If $enable is true (or missing), then "encode" will not throw an	140	If $enable is true (or missing), then "encode" will not throw an
…		…
141	instead will emit a reference to the earlier value.	156	instead will emit a reference to the earlier value.
142		157
143	This means that such values will only be encoded once, and will not	158	This means that such values will only be encoded once, and will not
144	result in a deep cloning of the value on decode, in decoders	159	result in a deep cloning of the value on decode, in decoders
145	supporting the value sharing extension. This also makes it possible	160	supporting the value sharing extension. This also makes it possible
146	to encode cyclic data structures (which need "allow_cycles" to ne	161	to encode cyclic data structures (which need "allow_cycles" to be
147	enabled to be decoded by this module).	162	enabled to be decoded by this module).
148		163
149	It is recommended to leave it off unless you know your communication	164	It is recommended to leave it off unless you know your communication
150	partner supports the value sharing extensions to CBOR	165	partner supports the value sharing extensions to CBOR
151	(<http://cbor.schmorp.de/value-sharing>), as without decoder	166	(<http://cbor.schmorp.de/value-sharing>), as without decoder
152	support, the resulting data structure might be unusable.	167	support, the resulting data structure might be unusable.
153		168
154	Detecting shared values incurs a runtime overhead when values are	169	Detecting shared values incurs a runtime overhead when values are
155	encoded that have a reference counter large than one, and might	170	encoded that have a reference counter large than one, and might
156	unnecessarily increase the encoded size, as potentially shared	171	unnecessarily increase the encoded size, as potentially shared
157	values are encode as shareable whether or not they are actually	172	values are encoded as shareable whether or not they are actually
158	shared.	173	shared.
159		174
160	At the moment, only targets of references can be shared (e.g.	175	At the moment, only targets of references can be shared (e.g.
161	scalars, arrays or hashes pointed to by a reference). Weirder	176	scalars, arrays or hashes pointed to by a reference). Weirder
162	constructs, such as an array with multiple "copies" of the same	177	constructs, such as an array with multiple "copies" of the same
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185	cyclic data structures using weak references when this option is	200	cyclic data structures using weak references when this option is
186	off, instead of throwing an error.	201	off, instead of throwing an error.
187		202
188	This option does not affect "encode" in any way - shared values and	203	This option does not affect "encode" in any way - shared values and
189	references will always be encoded properly if present.	204	references will always be encoded properly if present.
		205
		206	$cbor = $cbor->forbid_objects ([$enable])
		207	$enabled = $cbor->get_forbid_objects
		208	Disables the use of the object serialiser protocol.
		209
		210	If $enable is true (or missing), then "encode" will will throw an
		211	exception when it encounters perl objects that would be encoded
		212	using the perl-object tag (26). When "decode" encounters such tags,
		213	it will fall back to the general filter/tagged logic as if this were
		214	an unknown tag (by default resulting in a "CBOR::XC::Tagged"
		215	object).
		216
		217	If $enable is false (the default), then "encode" will use the
		218	Types::Serialiser object serialisation protocol to serialise objects
		219	into perl-object tags, and "decode" will do the same to decode such
		220	tags.
		221
		222	See "SECURITY CONSIDERATIONS", below, for more info on why
		223	forbidding this protocol can be useful.
190		224
191	$cbor = $cbor->pack_strings ([$enable])	225	$cbor = $cbor->pack_strings ([$enable])
192	$enabled = $cbor->get_pack_strings	226	$enabled = $cbor->get_pack_strings
193	If $enable is true (or missing), then "encode" will try not to	227	If $enable is true (or missing), then "encode" will try not to
194	encode the same string twice, but will instead encode a reference to	228	encode the same string twice, but will instead encode a reference to
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243	perl strings as CBOR byte strings.	277	perl strings as CBOR byte strings.
244		278
245	This option does not affect "decode" in any way.	279	This option does not affect "decode" in any way.
246		280
247	This option has similar advantages and disadvantages as "text_keys".	281	This option has similar advantages and disadvantages as "text_keys".
248	In addition, this option effectively removes the ability to encode	282	In addition, this option effectively removes the ability to
249	byte strings, which might break some "FREEZE" and "TO_CBOR" methods	283	automatically encode byte strings, which might break some "FREEZE"
250	that rely on this, such as bignum encoding, so this option is mainly	284	and "TO_CBOR" methods that rely on this.
251	useful for very simple data.	285
		286	A workaround is to use explicit type casts, which are unaffected by
		287	this option.
252		288
253	$cbor = $cbor->validate_utf8 ([$enable])	289	$cbor = $cbor->validate_utf8 ([$enable])
254	$enabled = $cbor->get_validate_utf8	290	$enabled = $cbor->get_validate_utf8
255	If $enable is true (or missing), then "decode" will validate that	291	If $enable is true (or missing), then "decode" will validate that
256	elements (text strings) containing UTF-8 data in fact contain valid	292	elements (text strings) containing UTF-8 data in fact contain valid
…		…
297	When the filter is cleared (the default state), the default filter	333	When the filter is cleared (the default state), the default filter
298	function, "CBOR::XS::default_filter", is used. This function simply	334	function, "CBOR::XS::default_filter", is used. This function simply
299	looks up the tag in the %CBOR::XS::FILTER hash. If an entry exists	335	looks up the tag in the %CBOR::XS::FILTER hash. If an entry exists
300	it must be a code reference that is called with tag and value, and	336	it must be a code reference that is called with tag and value, and
301	is responsible for decoding the value. If no entry exists, it	337	is responsible for decoding the value. If no entry exists, it
302	returns no values.	338	returns no values. "CBOR::XS" provides a number of default filter
		339	functions already, the the %CBOR::XS::FILTER hash can be freely
		340	extended with more.
		341
		342	"CBOR::XS" additionally provides an alternative filter function that
		343	is supposed to be safe to use with untrusted data (which the default
		344	filter might not), called "CBOR::XS::safe_filter", which works the
		345	same as the "default_filter" but uses the %CBOR::XS::SAFE_FILTER
		346	variable instead. It is prepopulated with the tag decoding functions
		347	that are deemed safe (basically the same as %CBOR::XS::FILTER
		348	without all the bignum tags), and can be extended by user code as
		349	wlel, although, obviously, one should be very careful about adding
		350	decoding functions here, since the expectation is that they are safe
		351	to use on untrusted data, after all.
303		352
304	Example: decode all tags not handled internally into	353	Example: decode all tags not handled internally into
305	"CBOR::XS::Tagged" objects, with no other special handling (useful	354	"CBOR::XS::Tagged" objects, with no other special handling (useful
306	when working with potentially "unsafe" CBOR data).	355	when working with potentially "unsafe" CBOR data).
307		356
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313	$CBOR::XS::FILTER{1347375694} = sub {	362	$CBOR::XS::FILTER{1347375694} = sub {
314	my ($tag, $value);	363	my ($tag, $value);
315		364
316	"tag 1347375694 value $value"	365	"tag 1347375694 value $value"
317	};	366	};
		367
		368	Example: provide your own filter function that looks up tags in your
		369	own hash:
		370
		371	my %my_filter = (
		372	998347484 => sub {
		373	my ($tag, $value);
		374
		375	"tag 998347484 value $value"
		376	};
		377	);
		378
		379	my $coder = CBOR::XS->new->filter (sub {
		380	&{ $my_filter{$_[0]} or return }
		381	});
		382
		383	Example: use the safe filter function (see "SECURITY CONSIDERATIONS"
		384	for more considerations on security).
		385
		386	CBOR::XS->new->filter (\&CBOR::XS::safe_filter)->decode ($cbor_data);
318		387
319	$cbor_data = $cbor->encode ($perl_scalar)	388	$cbor_data = $cbor->encode ($perl_scalar)
320	Converts the given Perl data structure (a scalar value) to its CBOR	389	Converts the given Perl data structure (a scalar value) to its CBOR
321	representation.	390	representation.
322		391
…		…
330	will silently stop parsing there and return the number of characters	399	will silently stop parsing there and return the number of characters
331	consumed so far.	400	consumed so far.
332		401
333	This is useful if your CBOR texts are not delimited by an outer	402	This is useful if your CBOR texts are not delimited by an outer
334	protocol and you need to know where the first CBOR string ends amd	403	protocol and you need to know where the first CBOR string ends amd
335	the next one starts.	404	the next one starts - CBOR strings are self-delimited, so it is
		405	possible to concatenate CBOR strings without any delimiters or size
		406	fields and recover their data.
336		407
337	CBOR::XS->new->decode_prefix ("......")	408	CBOR::XS->new->decode_prefix ("......")
338	=> ("...", 3)	409	=> ("...", 3)
339		410
340	INCREMENTAL PARSING	411	INCREMENTAL PARSING
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389	$cbor->incr_reset	460	$cbor->incr_reset
390	Resets the incremental decoder. This throws away any saved state, so	461	Resets the incremental decoder. This throws away any saved state, so
391	that subsequent calls to "incr_parse" or "incr_parse_multiple" start	462	that subsequent calls to "incr_parse" or "incr_parse_multiple" start
392	to parse a new CBOR value from the beginning of the $buffer again.	463	to parse a new CBOR value from the beginning of the $buffer again.
393		464
394	This method can be caled at any time, but it must be called if you	465	This method can be called at any time, but it must be called if
395	want to change your $buffer or there was a decoding error and you	466	you want to change your $buffer or there was a decoding error and
396	want to reuse the $cbor object for future incremental parsings.	467	you want to reuse the $cbor object for future incremental parsings.
397		468
398	MAPPING	469	MAPPING
399	This section describes how CBOR::XS maps Perl values to CBOR values and	470	This section describes how CBOR::XS maps Perl values to CBOR values and
400	vice versa. These mappings are designed to "do the right thing" in most	471	vice versa. These mappings are designed to "do the right thing" in most
401	circumstances automatically, preserving round-tripping characteristics	472	circumstances automatically, preserving round-tripping characteristics
…		…
513	$x .= ""; # another, more awkward way to stringify	584	$x .= ""; # another, more awkward way to stringify
514	print $x; # perl does it for you, too, quite often	585	print $x; # perl does it for you, too, quite often
515		586
516	You can force whether a string is encoded as byte or text string by	587	You can force whether a string is encoded as byte or text string by
517	using "utf8::upgrade" and "utf8::downgrade" (if "text_strings" is	588	using "utf8::upgrade" and "utf8::downgrade" (if "text_strings" is
518	disabled):	589	disabled).
519		590
520	utf8::upgrade $x; # encode $x as text string	591	utf8::upgrade $x; # encode $x as text string
521	utf8::downgrade $x; # encode $x as byte string	592	utf8::downgrade $x; # encode $x as byte string
		593
		594	More options are available, see "TYPE CASTS", below, and the
		595	"text_keys" and "text_strings" options.
522		596
523	Perl doesn't define what operations up- and downgrade strings, so if	597	Perl doesn't define what operations up- and downgrade strings, so if
524	the difference between byte and text is important, you should up- or	598	the difference between byte and text is important, you should up- or
525	downgrade your string as late as possible before encoding. You can	599	downgrade your string as late as possible before encoding. You can
526	also force the use of CBOR text strings by using "text_keys" or	600	also force the use of CBOR text strings by using "text_keys" or
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540	possible representation. Floating-point values will use either the	614	possible representation. Floating-point values will use either the
541	IEEE single format if possible without loss of precision, otherwise	615	IEEE single format if possible without loss of precision, otherwise
542	the IEEE double format will be used. Perls that use formats other	616	the IEEE double format will be used. Perls that use formats other
543	than IEEE double to represent numerical values are supported, but	617	than IEEE double to represent numerical values are supported, but
544	might suffer loss of precision.	618	might suffer loss of precision.
		619
		620	TYPE CASTS
		621	EXPERIMENTAL: As an experimental extension, "CBOR::XS" allows you to
		622	force specific CBOR types to be used when encoding. That allows you to
		623	encode types not normally accessible (e.g. half floats) as well as force
		624	string types even when "text_strings" is in effect.
		625
		626	Type forcing is done by calling a special "cast" function which keeps a
		627	copy of the value and returns a new value that can be handed over to any
		628	CBOR encoder function.
		629
		630	The following casts are currently available (all of which are unary
		631	operators, that is, have a prototype of "$"):
		632
		633	CBOR::XS::as_int $value
		634	Forces the value to be encoded as some form of (basic, not bignum)
		635	integer type.
		636
		637	CBOR::XS::as_text $value
		638	Forces the value to be encoded as (UTF-8) text values.
		639
		640	CBOR::XS::as_bytes $value
		641	Forces the value to be encoded as a (binary) string value.
		642
		643	Example: encode a perl string as binary even though "text_strings"
		644	is in effect.
		645
		646	CBOR::XS->new->text_strings->encode ([4, "text", CBOR::XS::bytes "bytevalue"]);
		647
		648	CBOR::XS::as_bool $value
		649	Converts a Perl boolean (which can be any kind of scalar) into a
		650	CBOR boolean. Strictly the same, but shorter to write, than:
		651
		652	$value ? Types::Serialiser::true : Types::Serialiser::false
		653
		654	CBOR::XS::as_float16 $value
		655	Forces half-float (IEEE 754 binary16) encoding of the given value.
		656
		657	CBOR::XS::as_float32 $value
		658	Forces single-float (IEEE 754 binary32) encoding of the given value.
		659
		660	CBOR::XS::as_float64 $value
		661	Forces double-float (IEEE 754 binary64) encoding of the given value.
		662
		663	CBOR::XS::as_cbor $cbor_text
		664	Not a type cast per-se, this type cast forces the argument to be
		665	encoded as-is. This can be used to embed pre-encoded CBOR data.
		666
		667	Note that no checking on the validity of the $cbor_text is done -
		668	it's the callers responsibility to correctly encode values.
		669
		670	CBOR::XS::as_map [key => value...]
		671	Treat the array reference as key value pairs and output a CBOR map.
		672	This allows you to generate CBOR maps with arbitrary key types (or,
		673	if you don't care about semantics, duplicate keys or pairs in a
		674	custom order), which is otherwise hard to do with Perl.
		675
		676	The single argument must be an array reference with an even number
		677	of elements.
		678
		679	Note that only the reference to the array is copied, the array
		680	itself is not. Modifications done to the array before calling an
		681	encoding function will be reflected in the encoded output.
		682
		683	Example: encode a CBOR map with a string and an integer as keys.
		684
		685	encode_cbor CBOR::XS::as_map [string => "value", 5 => "value"]
545		686
546	OBJECT SERIALISATION	687	OBJECT SERIALISATION
547	This module implements both a CBOR-specific and the generic	688	This module implements both a CBOR-specific and the generic
548	Types::Serialier object serialisation protocol. The following	689	Types::Serialier object serialisation protocol. The following
549	subsections explain both methods.	690	subsections explain both methods.
…		…
840	interoperability is improved in the future, then the goal will be to	981	interoperability is improved in the future, then the goal will be to
841	ensure that decoded JSON data will round-trip encoding and decoding to	982	ensure that decoded JSON data will round-trip encoding and decoding to
842	CBOR intact.	983	CBOR intact.
843		984
844	SECURITY CONSIDERATIONS	985	SECURITY CONSIDERATIONS
845	When you are using CBOR in a protocol, talking to untrusted potentially	986	Tl;dr... if you want to decode or encode CBOR from untrusted sources,
846	hostile creatures requires relatively few measures.	987	you should start with a coder object created via "new_safe" (which
		988	implements the mitigations explained below):
847		989
		990	my $coder = CBOR::XS->new_safe;
		991
		992	my $data = $coder->decode ($cbor_text);
		993	my $cbor = $coder->encode ($data);
		994
		995	Longer version: When you are using CBOR in a protocol, talking to
		996	untrusted potentially hostile creatures requires some thought:
		997
		998	Security of the CBOR decoder itself
848	First of all, your CBOR decoder should be secure, that is, should not	999	First and foremost, your CBOR decoder should be secure, that is,
849	have any buffer overflows. Obviously, this module should ensure that and	1000	should not have any buffer overflows or similar bugs that could
		1001	potentially be exploited. Obviously, this module should ensure that
850	I am trying hard on making that true, but you never know.	1002	and I am trying hard on making that true, but you never know.
851		1003
		1004	CBOR::XS can invoke almost arbitrary callbacks during decoding
		1005	CBOR::XS supports object serialisation - decoding CBOR can cause
		1006	calls to any "THAW" method in any package that exists in your
		1007	process (that is, CBOR::XS will not try to load modules, but any
		1008	existing "THAW" method or function can be called, so they all have
		1009	to be secure).
		1010
		1011	Less obviously, it will also invoke "TO_CBOR" and "FREEZE" methods -
		1012	even if all your "THAW" methods are secure, encoding data structures
		1013	from untrusted sources can invoke those and trigger bugs in those.
		1014
		1015	So, if you are not sure about the security of all the modules you
		1016	have loaded (you shouldn't), you should disable this part using
		1017	"forbid_objects" or using "new_safe".
		1018
		1019	CBOR can be extended with tags that call library code
		1020	CBOR can be extended with tags, and "CBOR::XS" has a registry of
		1021	conversion functions for many existing tags that can be extended via
		1022	third-party modules (see the "filter" method).
		1023
		1024	If you don't trust these, you should configure the "safe" filter
		1025	function, "CBOR::XS::safe_filter" ("new_safe" does this), which by
		1026	default only includes conversion functions that are considered
		1027	"safe" by the author (but again, they can be extended by third party
		1028	modules).
		1029
		1030	Depending on your level of paranoia, you can use the "safe" filter:
		1031
		1032	$cbor->filter (\&CBOR::XS::safe_filter);
		1033
		1034	... your own filter...
		1035
		1036	$cbor->filter (sub { ... do your stuffs here ... });
		1037
		1038	... or even no filter at all, disabling all tag decoding:
		1039
		1040	$cbor->filter (sub { });
		1041
		1042	This is never a problem for encoding, as the tag mechanism only
		1043	exists in CBOR texts.
		1044
		1045	Resource-starving attacks: object memory usage
852	Second, you need to avoid resource-starving attacks. That means you	1046	You need to avoid resource-starving attacks. That means you should
853	should limit the size of CBOR data you accept, or make sure then when	1047	limit the size of CBOR data you accept, or make sure then when your
854	your resources run out, that's just fine (e.g. by using a separate	1048	resources run out, that's just fine (e.g. by using a separate
855	process that can crash safely). The size of a CBOR string in octets is	1049	process that can crash safely). The size of a CBOR string in octets
856	usually a good indication of the size of the resources required to	1050	is usually a good indication of the size of the resources required
857	decode it into a Perl structure. While CBOR::XS can check the size of	1051	to decode it into a Perl structure. While CBOR::XS can check the
		1052	size of the CBOR text (using "max_size" - done by "new_safe"), it
858	the CBOR text, it might be too late when you already have it in memory,	1053	might be too late when you already have it in memory, so you might
859	so you might want to check the size before you accept the string.	1054	want to check the size before you accept the string.
860		1055
		1056	As for encoding, it is possible to construct data structures that
		1057	are relatively small but result in large CBOR texts (for example by
		1058	having an array full of references to the same big data structure,
		1059	which will all be deep-cloned during encoding by default). This is
		1060	rarely an actual issue (and the worst case is still just running out
		1061	of memory), but you can reduce this risk by using "allow_sharing".
		1062
		1063	Resource-starving attacks: stack overflows
861	Third, CBOR::XS recurses using the C stack when decoding objects and	1064	CBOR::XS recurses using the C stack when decoding objects and
862	arrays. The C stack is a limited resource: for instance, on my amd64	1065	arrays. The C stack is a limited resource: for instance, on my amd64
863	machine with 8MB of stack size I can decode around 180k nested arrays	1066	machine with 8MB of stack size I can decode around 180k nested
864	but only 14k nested CBOR objects (due to perl itself recursing deeply on	1067	arrays but only 14k nested CBOR objects (due to perl itself
865	croak to free the temporary). If that is exceeded, the program crashes.	1068	recursing deeply on croak to free the temporary). If that is
866	To be conservative, the default nesting limit is set to 512. If your	1069	exceeded, the program crashes. To be conservative, the default
867	process has a smaller stack, you should adjust this setting accordingly	1070	nesting limit is set to 512. If your process has a smaller stack,
868	with the "max_depth" method.	1071	you should adjust this setting accordingly with the "max_depth"
		1072	method.
869		1073
		1074	Resource-starving attacks: CPU en-/decoding complexity
		1075	CBOR::XS will use the Math::BigInt, Math::BigFloat and Math::BigRat
		1076	libraries to represent encode/decode bignums. These can be very slow
		1077	(as in, centuries of CPU time) and can even crash your program (and
		1078	are generally not very trustworthy). See the next section on bignum
		1079	security for details.
		1080
		1081	Data breaches: leaking information in error messages
		1082	CBOR::XS might leak contents of your Perl data structures in its
		1083	error messages, so when you serialise sensitive information you
		1084	might want to make sure that exceptions thrown by CBOR::XS will not
		1085	end up in front of untrusted eyes.
		1086
		1087	Something else...
870	Something else could bomb you, too, that I forgot to think of. In that	1088	Something else could bomb you, too, that I forgot to think of. In
871	case, you get to keep the pieces. I am always open for hints, though...	1089	that case, you get to keep the pieces. I am always open for hints,
872		1090	though...
873	Also keep in mind that CBOR::XS might leak contents of your Perl data
874	structures in its error messages, so when you serialise sensitive
875	information you might want to make sure that exceptions thrown by
876	CBOR::XS will not end up in front of untrusted eyes.
877		1091
878	BIGNUM SECURITY CONSIDERATIONS	1092	BIGNUM SECURITY CONSIDERATIONS
879	CBOR::XS provides a "TO_CBOR" method for both Math::BigInt and	1093	CBOR::XS provides a "TO_CBOR" method for both Math::BigInt and
880	Math::BigFloat that tries to encode the number in the simplest possible	1094	Math::BigFloat that tries to encode the number in the simplest possible
881	way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag	1095	way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
…		…
923		1137
924	LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT	1138	LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
925	On perls that were built without 64 bit integer support (these are rare	1139	On perls that were built without 64 bit integer support (these are rare
926	nowadays, even on 32 bit architectures, as all major Perl distributions	1140	nowadays, even on 32 bit architectures, as all major Perl distributions
927	are built with 64 bit integer support), support for any kind of 64 bit	1141	are built with 64 bit integer support), support for any kind of 64 bit
928	integer in CBOR is very limited - most likely, these 64 bit values will	1142	value in CBOR is very limited - most likely, these 64 bit values will be
929	be truncated, corrupted, or otherwise not decoded correctly. This also	1143	truncated, corrupted, or otherwise not decoded correctly. This also
930	includes string, array and map sizes that are stored as 64 bit integers.	1144	includes string, float, array and map sizes that are stored as 64 bit
		1145	integers.
931		1146
932	THREADS	1147	THREADS
933	This module is not guaranteed to be thread safe and there are no plans	1148	This module is not guaranteed to be thread safe and there are no plans
934	to change this until Perl gets thread support (as opposed to the	1149	to change this until Perl gets thread support (as opposed to the
935	horribly slow so-called "threads" which are simply slow and bloated	1150	horribly slow so-called "threads" which are simply slow and bloated

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Comparing CBOR-XS/README (file contents): Revision 1.17 by root, Wed Apr 27 09:40:18 2016 UTC vs. Revision 1.22 by root, Thu Oct 21 01:14:58 2021 UTC

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Comparing CBOR-XS/README (file contents):
Revision 1.17 by root, Wed Apr 27 09:40:18 2016 UTC vs.
Revision 1.22 by root, Thu Oct 21 01:14:58 2021 UTC