[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 1.23 by root, Fri Sep 8 20:03:06 2023 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
…		…
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 larger 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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178	code that isn't prepared for this will not leak memory.	193	code that isn't prepared for this will not leak memory.
179		194
180	If $enable is false (the default), then "decode" will throw an error	195	If $enable is false (the default), then "decode" will throw an error
181	when it encounters a self-referential/cyclic data structure.	196	when it encounters a self-referential/cyclic data structure.
182		197
183	FUTURE DIRECTION: the motivation behind this option is to avoid
184	real cycles - future versions of this module might chose to decode
185	cyclic data structures using weak references when this option is
186	off, instead of throwing an error.
187
188	This option does not affect "encode" in any way - shared values and	198	This option does not affect "encode" in any way - shared values and
189	references will always be encoded properly if present.	199	references will always be encoded properly if present.
		200
		201	$cbor = $cbor->allow_weak_cycles ([$enable])
		202	$enabled = $cbor->get_allow_weak_cycles
		203	This works like "allow_cycles" in that it allows the resulting data
		204	structures to contain cycles, but unlike "allow_cycles", those
		205	cyclic rreferences will be weak. That means that code that
		206	recurrsively walks the data structure must be prepared with cycles,
		207	but at least not special precautions must be implemented to free
		208	these data structures.
		209
		210	Only those references leading to actual cycles will be weakened -
		211	other references, e.g. when the same hash or arrray is referenced
		212	multiple times in an arrray, will be normal references.
		213
		214	This option does not affect "encode" in any way - shared values and
		215	references will always be encoded properly if present.
		216
		217	$cbor = $cbor->forbid_objects ([$enable])
		218	$enabled = $cbor->get_forbid_objects
		219	Disables the use of the object serialiser protocol.
		220
		221	If $enable is true (or missing), then "encode" will will throw an
		222	exception when it encounters perl objects that would be encoded
		223	using the perl-object tag (26). When "decode" encounters such tags,
		224	it will fall back to the general filter/tagged logic as if this were
		225	an unknown tag (by default resulting in a "CBOR::XC::Tagged"
		226	object).
		227
		228	If $enable is false (the default), then "encode" will use the
		229	Types::Serialiser object serialisation protocol to serialise objects
		230	into perl-object tags, and "decode" will do the same to decode such
		231	tags.
		232
		233	See "SECURITY CONSIDERATIONS", below, for more info on why
		234	forbidding this protocol can be useful.
190		235
191	$cbor = $cbor->pack_strings ([$enable])	236	$cbor = $cbor->pack_strings ([$enable])
192	$enabled = $cbor->get_pack_strings	237	$enabled = $cbor->get_pack_strings
193	If $enable is true (or missing), then "encode" will try not to	238	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	239	encode the same string twice, but will instead encode a reference to
…		…
243	perl strings as CBOR byte strings.	288	perl strings as CBOR byte strings.
244		289
245	This option does not affect "decode" in any way.	290	This option does not affect "decode" in any way.
246		291
247	This option has similar advantages and disadvantages as "text_keys".	292	This option has similar advantages and disadvantages as "text_keys".
248	In addition, this option effectively removes the ability to encode	293	In addition, this option effectively removes the ability to
249	byte strings, which might break some "FREEZE" and "TO_CBOR" methods	294	automatically encode byte strings, which might break some "FREEZE"
250	that rely on this, such as bignum encoding, so this option is mainly	295	and "TO_CBOR" methods that rely on this.
251	useful for very simple data.	296
		297	A workaround is to use explicit type casts, which are unaffected by
		298	this option.
252		299
253	$cbor = $cbor->validate_utf8 ([$enable])	300	$cbor = $cbor->validate_utf8 ([$enable])
254	$enabled = $cbor->get_validate_utf8	301	$enabled = $cbor->get_validate_utf8
255	If $enable is true (or missing), then "decode" will validate that	302	If $enable is true (or missing), then "decode" will validate that
256	elements (text strings) containing UTF-8 data in fact contain valid	303	elements (text strings) containing UTF-8 data in fact contain valid
…		…
297	When the filter is cleared (the default state), the default filter	344	When the filter is cleared (the default state), the default filter
298	function, "CBOR::XS::default_filter", is used. This function simply	345	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	346	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	347	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	348	is responsible for decoding the value. If no entry exists, it
302	returns no values.	349	returns no values. "CBOR::XS" provides a number of default filter
		350	functions already, the the %CBOR::XS::FILTER hash can be freely
		351	extended with more.
		352
		353	"CBOR::XS" additionally provides an alternative filter function that
		354	is supposed to be safe to use with untrusted data (which the default
		355	filter might not), called "CBOR::XS::safe_filter", which works the
		356	same as the "default_filter" but uses the %CBOR::XS::SAFE_FILTER
		357	variable instead. It is prepopulated with the tag decoding functions
		358	that are deemed safe (basically the same as %CBOR::XS::FILTER
		359	without all the bignum tags), and can be extended by user code as
		360	wlel, although, obviously, one should be very careful about adding
		361	decoding functions here, since the expectation is that they are safe
		362	to use on untrusted data, after all.
303		363
304	Example: decode all tags not handled internally into	364	Example: decode all tags not handled internally into
305	"CBOR::XS::Tagged" objects, with no other special handling (useful	365	"CBOR::XS::Tagged" objects, with no other special handling (useful
306	when working with potentially "unsafe" CBOR data).	366	when working with potentially "unsafe" CBOR data).
307		367
…		…
313	$CBOR::XS::FILTER{1347375694} = sub {	373	$CBOR::XS::FILTER{1347375694} = sub {
314	my ($tag, $value);	374	my ($tag, $value);
315		375
316	"tag 1347375694 value $value"	376	"tag 1347375694 value $value"
317	};	377	};
		378
		379	Example: provide your own filter function that looks up tags in your
		380	own hash:
		381
		382	my %my_filter = (
		383	998347484 => sub {
		384	my ($tag, $value);
		385
		386	"tag 998347484 value $value"
		387	};
		388	);
		389
		390	my $coder = CBOR::XS->new->filter (sub {
		391	&{ $my_filter{$_[0]} or return }
		392	});
		393
		394	Example: use the safe filter function (see "SECURITY CONSIDERATIONS"
		395	for more considerations on security).
		396
		397	CBOR::XS->new->filter (\&CBOR::XS::safe_filter)->decode ($cbor_data);
318		398
319	$cbor_data = $cbor->encode ($perl_scalar)	399	$cbor_data = $cbor->encode ($perl_scalar)
320	Converts the given Perl data structure (a scalar value) to its CBOR	400	Converts the given Perl data structure (a scalar value) to its CBOR
321	representation.	401	representation.
322		402
…		…
330	will silently stop parsing there and return the number of characters	410	will silently stop parsing there and return the number of characters
331	consumed so far.	411	consumed so far.
332		412
333	This is useful if your CBOR texts are not delimited by an outer	413	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	414	protocol and you need to know where the first CBOR string ends amd
335	the next one starts.	415	the next one starts - CBOR strings are self-delimited, so it is
		416	possible to concatenate CBOR strings without any delimiters or size
		417	fields and recover their data.
336		418
337	CBOR::XS->new->decode_prefix ("......")	419	CBOR::XS->new->decode_prefix ("......")
338	=> ("...", 3)	420	=> ("...", 3)
339		421
340	INCREMENTAL PARSING	422	INCREMENTAL PARSING
…		…
343	data structure in memory at one time, it does allow you to parse a CBOR	425	data structure in memory at one time, it does allow you to parse a CBOR
344	stream incrementally, using a similar to using "decode_prefix" to see if	426	stream incrementally, using a similar to using "decode_prefix" to see if
345	a full CBOR object is available, but is much more efficient.	427	a full CBOR object is available, but is much more efficient.
346		428
347	It basically works by parsing as much of a CBOR string as possible - if	429	It basically works by parsing as much of a CBOR string as possible - if
348	the CBOR data is not complete yet, the pasrer will remember where it	430	the CBOR data is not complete yet, the parser will remember where it
349	was, to be able to restart when more data has been accumulated. Once	431	was, to be able to restart when more data has been accumulated. Once
350	enough data is available to either decode a complete CBOR value or raise	432	enough data is available to either decode a complete CBOR value or raise
351	an error, a real decode will be attempted.	433	an error, a real decode will be attempted.
352		434
353	A typical use case would be a network protocol that consists of sending	435	A typical use case would be a network protocol that consists of sending
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389	$cbor->incr_reset	471	$cbor->incr_reset
390	Resets the incremental decoder. This throws away any saved state, so	472	Resets the incremental decoder. This throws away any saved state, so
391	that subsequent calls to "incr_parse" or "incr_parse_multiple" start	473	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.	474	to parse a new CBOR value from the beginning of the $buffer again.
393		475
394	This method can be caled at any time, but it must be called if you	476	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	477	you want to change your $buffer or there was a decoding error and
396	want to reuse the $cbor object for future incremental parsings.	478	you want to reuse the $cbor object for future incremental parsings.
397		479
398	MAPPING	480	MAPPING
399	This section describes how CBOR::XS maps Perl values to CBOR values and	481	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	482	vice versa. These mappings are designed to "do the right thing" in most
401	circumstances automatically, preserving round-tripping characteristics	483	circumstances automatically, preserving round-tripping characteristics
…		…
477	"CBOR::XS::tag" to create such objects.	559	"CBOR::XS::tag" to create such objects.
478		560
479	Types::Serialiser::true, Types::Serialiser::false,	561	Types::Serialiser::true, Types::Serialiser::false,
480	Types::Serialiser::error	562	Types::Serialiser::error
481	These special values become CBOR true, CBOR false and CBOR undefined	563	These special values become CBOR true, CBOR false and CBOR undefined
482	values, respectively. You can also use "\1", "\0" and "\undef"	564	values, respectively.
483	directly if you want.
484		565
485	other blessed objects	566	other blessed objects
486	Other blessed objects are serialised via "TO_CBOR" or "FREEZE". See	567	Other blessed objects are serialised via "TO_CBOR" or "FREEZE". See
487	"TAG HANDLING AND EXTENSIONS" for specific classes handled by this	568	"TAG HANDLING AND EXTENSIONS" for specific classes handled by this
488	module, and "OBJECT SERIALISATION" for generic object serialisation.	569	module, and "OBJECT SERIALISATION" for generic object serialisation.
…		…
513	$x .= ""; # another, more awkward way to stringify	594	$x .= ""; # another, more awkward way to stringify
514	print $x; # perl does it for you, too, quite often	595	print $x; # perl does it for you, too, quite often
515		596
516	You can force whether a string is encoded as byte or text string by	597	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	598	using "utf8::upgrade" and "utf8::downgrade" (if "text_strings" is
518	disabled):	599	disabled).
519		600
520	utf8::upgrade $x; # encode $x as text string	601	utf8::upgrade $x; # encode $x as text string
521	utf8::downgrade $x; # encode $x as byte string	602	utf8::downgrade $x; # encode $x as byte string
		603
		604	More options are available, see "TYPE CASTS", below, and the
		605	"text_keys" and "text_strings" options.
522		606
523	Perl doesn't define what operations up- and downgrade strings, so if	607	Perl doesn't define what operations up- and downgrade strings, so if
524	the difference between byte and text is important, you should up- or	608	the difference between byte and text is important, you should up- or
525	downgrade your string as late as possible before encoding. You can	609	downgrade your string as late as possible before encoding. You can
526	also force the use of CBOR text strings by using "text_keys" or	610	also force the use of CBOR text strings by using "text_keys" or
…		…
540	possible representation. Floating-point values will use either the	624	possible representation. Floating-point values will use either the
541	IEEE single format if possible without loss of precision, otherwise	625	IEEE single format if possible without loss of precision, otherwise
542	the IEEE double format will be used. Perls that use formats other	626	the IEEE double format will be used. Perls that use formats other
543	than IEEE double to represent numerical values are supported, but	627	than IEEE double to represent numerical values are supported, but
544	might suffer loss of precision.	628	might suffer loss of precision.
		629
		630	TYPE CASTS
		631	EXPERIMENTAL: As an experimental extension, "CBOR::XS" allows you to
		632	force specific CBOR types to be used when encoding. That allows you to
		633	encode types not normally accessible (e.g. half floats) as well as force
		634	string types even when "text_strings" is in effect.
		635
		636	Type forcing is done by calling a special "cast" function which keeps a
		637	copy of the value and returns a new value that can be handed over to any
		638	CBOR encoder function.
		639
		640	The following casts are currently available (all of which are unary
		641	operators, that is, have a prototype of "$"):
		642
		643	CBOR::XS::as_int $value
		644	Forces the value to be encoded as some form of (basic, not bignum)
		645	integer type.
		646
		647	CBOR::XS::as_text $value
		648	Forces the value to be encoded as (UTF-8) text values.
		649
		650	CBOR::XS::as_bytes $value
		651	Forces the value to be encoded as a (binary) string value.
		652
		653	Example: encode a perl string as binary even though "text_strings"
		654	is in effect.
		655
		656	CBOR::XS->new->text_strings->encode ([4, "text", CBOR::XS::bytes "bytevalue"]);
		657
		658	CBOR::XS::as_bool $value
		659	Converts a Perl boolean (which can be any kind of scalar) into a
		660	CBOR boolean. Strictly the same, but shorter to write, than:
		661
		662	$value ? Types::Serialiser::true : Types::Serialiser::false
		663
		664	CBOR::XS::as_float16 $value
		665	Forces half-float (IEEE 754 binary16) encoding of the given value.
		666
		667	CBOR::XS::as_float32 $value
		668	Forces single-float (IEEE 754 binary32) encoding of the given value.
		669
		670	CBOR::XS::as_float64 $value
		671	Forces double-float (IEEE 754 binary64) encoding of the given value.
		672
		673	CBOR::XS::as_cbor $cbor_text
		674	Not a type cast per-se, this type cast forces the argument to be
		675	encoded as-is. This can be used to embed pre-encoded CBOR data.
		676
		677	Note that no checking on the validity of the $cbor_text is done -
		678	it's the callers responsibility to correctly encode values.
		679
		680	CBOR::XS::as_map [key => value...]
		681	Treat the array reference as key value pairs and output a CBOR map.
		682	This allows you to generate CBOR maps with arbitrary key types (or,
		683	if you don't care about semantics, duplicate keys or pairs in a
		684	custom order), which is otherwise hard to do with Perl.
		685
		686	The single argument must be an array reference with an even number
		687	of elements.
		688
		689	Note that only the reference to the array is copied, the array
		690	itself is not. Modifications done to the array before calling an
		691	encoding function will be reflected in the encoded output.
		692
		693	Example: encode a CBOR map with a string and an integer as keys.
		694
		695	encode_cbor CBOR::XS::as_map [string => "value", 5 => "value"]
545		696
546	OBJECT SERIALISATION	697	OBJECT SERIALISATION
547	This module implements both a CBOR-specific and the generic	698	This module implements both a CBOR-specific and the generic
548	Types::Serialier object serialisation protocol. The following	699	Types::Serialier object serialisation protocol. The following
549	subsections explain both methods.	700	subsections explain both methods.
…		…
840	interoperability is improved in the future, then the goal will be to	991	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	992	ensure that decoded JSON data will round-trip encoding and decoding to
842	CBOR intact.	993	CBOR intact.
843		994
844	SECURITY CONSIDERATIONS	995	SECURITY CONSIDERATIONS
845	When you are using CBOR in a protocol, talking to untrusted potentially	996	Tl;dr... if you want to decode or encode CBOR from untrusted sources,
846	hostile creatures requires relatively few measures.	997	you should start with a coder object created via "new_safe" (which
		998	implements the mitigations explained below):
847		999
		1000	my $coder = CBOR::XS->new_safe;
		1001
		1002	my $data = $coder->decode ($cbor_text);
		1003	my $cbor = $coder->encode ($data);
		1004
		1005	Longer version: When you are using CBOR in a protocol, talking to
		1006	untrusted potentially hostile creatures requires some thought:
		1007
		1008	Security of the CBOR decoder itself
848	First of all, your CBOR decoder should be secure, that is, should not	1009	First and foremost, your CBOR decoder should be secure, that is,
849	have any buffer overflows. Obviously, this module should ensure that and	1010	should not have any buffer overflows or similar bugs that could
		1011	potentially be exploited. Obviously, this module should ensure that
850	I am trying hard on making that true, but you never know.	1012	and I am trying hard on making that true, but you never know.
851		1013
		1014	CBOR::XS can invoke almost arbitrary callbacks during decoding
		1015	CBOR::XS supports object serialisation - decoding CBOR can cause
		1016	calls to any "THAW" method in any package that exists in your
		1017	process (that is, CBOR::XS will not try to load modules, but any
		1018	existing "THAW" method or function can be called, so they all have
		1019	to be secure).
		1020
		1021	Less obviously, it will also invoke "TO_CBOR" and "FREEZE" methods -
		1022	even if all your "THAW" methods are secure, encoding data structures
		1023	from untrusted sources can invoke those and trigger bugs in those.
		1024
		1025	So, if you are not sure about the security of all the modules you
		1026	have loaded (you shouldn't), you should disable this part using
		1027	"forbid_objects" or using "new_safe".
		1028
		1029	CBOR can be extended with tags that call library code
		1030	CBOR can be extended with tags, and "CBOR::XS" has a registry of
		1031	conversion functions for many existing tags that can be extended via
		1032	third-party modules (see the "filter" method).
		1033
		1034	If you don't trust these, you should configure the "safe" filter
		1035	function, "CBOR::XS::safe_filter" ("new_safe" does this), which by
		1036	default only includes conversion functions that are considered
		1037	"safe" by the author (but again, they can be extended by third party
		1038	modules).
		1039
		1040	Depending on your level of paranoia, you can use the "safe" filter:
		1041
		1042	$cbor->filter (\&CBOR::XS::safe_filter);
		1043
		1044	... your own filter...
		1045
		1046	$cbor->filter (sub { ... do your stuffs here ... });
		1047
		1048	... or even no filter at all, disabling all tag decoding:
		1049
		1050	$cbor->filter (sub { });
		1051
		1052	This is never a problem for encoding, as the tag mechanism only
		1053	exists in CBOR texts.
		1054
		1055	Resource-starving attacks: object memory usage
852	Second, you need to avoid resource-starving attacks. That means you	1056	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	1057	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	1058	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	1059	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	1060	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	1061	to decode it into a Perl structure. While CBOR::XS can check the
		1062	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,	1063	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.	1064	want to check the size before you accept the string.
860		1065
		1066	As for encoding, it is possible to construct data structures that
		1067	are relatively small but result in large CBOR texts (for example by
		1068	having an array full of references to the same big data structure,
		1069	which will all be deep-cloned during encoding by default). This is
		1070	rarely an actual issue (and the worst case is still just running out
		1071	of memory), but you can reduce this risk by using "allow_sharing".
		1072
		1073	Resource-starving attacks: stack overflows
861	Third, CBOR::XS recurses using the C stack when decoding objects and	1074	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	1075	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	1076	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	1077	arrays but only 14k nested CBOR objects (due to perl itself
865	croak to free the temporary). If that is exceeded, the program crashes.	1078	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	1079	exceeded, the program crashes. To be conservative, the default
867	process has a smaller stack, you should adjust this setting accordingly	1080	nesting limit is set to 512. If your process has a smaller stack,
868	with the "max_depth" method.	1081	you should adjust this setting accordingly with the "max_depth"
		1082	method.
869		1083
		1084	Resource-starving attacks: CPU en-/decoding complexity
		1085	CBOR::XS will use the Math::BigInt, Math::BigFloat and Math::BigRat
		1086	libraries to represent encode/decode bignums. These can be very slow
		1087	(as in, centuries of CPU time) and can even crash your program (and
		1088	are generally not very trustworthy). See the next section on bignum
		1089	security for details.
		1090
		1091	Data breaches: leaking information in error messages
		1092	CBOR::XS might leak contents of your Perl data structures in its
		1093	error messages, so when you serialise sensitive information you
		1094	might want to make sure that exceptions thrown by CBOR::XS will not
		1095	end up in front of untrusted eyes.
		1096
		1097	Something else...
870	Something else could bomb you, too, that I forgot to think of. In that	1098	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...	1099	that case, you get to keep the pieces. I am always open for hints,
872		1100	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		1101
878	BIGNUM SECURITY CONSIDERATIONS	1102	BIGNUM SECURITY CONSIDERATIONS
879	CBOR::XS provides a "TO_CBOR" method for both Math::BigInt and	1103	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	1104	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	1105	way, that is, either a CBOR integer, a CBOR bigint/decimal fraction (tag
…		…
923		1147
924	LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT	1148	LIMITATIONS ON PERLS WITHOUT 64-BIT INTEGER SUPPORT
925	On perls that were built without 64 bit integer support (these are rare	1149	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	1150	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	1151	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	1152	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	1153	truncated, corrupted, or otherwise not decoded correctly. This also
930	includes string, array and map sizes that are stored as 64 bit integers.	1154	includes string, float, array and map sizes that are stored as 64 bit
		1155	integers.
931		1156
932	THREADS	1157	THREADS
933	This module is not guaranteed to be thread safe and there are no plans	1158	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	1159	to change this until Perl gets thread support (as opposed to the
935	horribly slow so-called "threads" which are simply slow and bloated	1160	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 1.23 by root, Fri Sep 8 20:03:06 2023 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 1.23 by root, Fri Sep 8 20:03:06 2023 UTC