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

Comparing Convert-BER-XS/XS.pm (file contents):
Revision 1.1 by root, Fri Apr 19 16:19:36 2019 UTC vs.
Revision 1.6 by root, Fri Apr 19 20:38:38 2019 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	Convert::BER::XS - I<very> low level BER decoding	3	Convert::BER::XS - I<very> low level BER en-/decoding
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use Convert::BER::XS ':all';	7	use Convert::BER::XS ':all';
8		8
9	my $ber = ber_decode $buf	9	my $ber = ber_decode $buf
10	or die "unable to decode SNMP v1/v2c Message";	10	or die "unable to decode SNMP message";
		11
		12	# The above results in a data structure consisting of (class, tag,
		13	# constructed, data) tuples. Below is such a message, SNMPv1 trap
		14	# with a Cisco mac change notification.
		15	# Did you know that Cisco is in the news almost every week because
		16	# of some backdoor password or other extremely stupid security bug?
		17
		18	[ ASN_UNIVERSAL, ASN_SEQUENCE, 1,
		19	[
		20	[ ASN_UNIVERSAL, ASN_INTEGER32, 0, 0 ], # snmp version 1
		21	[ ASN_UNIVERSAL, 4, 0, "public" ], # community
		22	[ ASN_CONTEXT, 4, 1, # CHOICE, constructed - trap PDU
		23	[
		24	[ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.2" ], # enterprise oid
		25	[ ASN_APPLICATION, 0, 0, "\x0a\x00\x00\x01" ], # SNMP IpAddress, 10.0.0.1
		26	[ ASN_UNIVERSAL, ASN_INTEGER32, 0, 6 ], # generic trap
		27	[ ASN_UNIVERSAL, ASN_INTEGER32, 0, 1 ], # specific trap
		28	[ ASN_APPLICATION, ASN_TIMETICKS, 0, 1817903850 ], # SNMP TimeTicks
		29	[ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # the varbindlist
		30	[
		31	[ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # a single varbind, "key value" pair
		32	[
		33	[ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.1.1.8.1.2.1" ], # the oid
		34	[ ASN_UNIVERSAL, ASN_OCTET_STRING, 0, "...data..." # the value
		35	]
		36	]
		37	],
		38	...
		39
		40	# let's decode it a bit with some helper functions
11		41
12	my $msg = ber_is_seq $ber	42	my $msg = ber_is_seq $ber
13	or die "SNMP message does not start with a sequence";	43	or die "SNMP message does not start with a sequence";
14		44
15	ber_is $msg->[0], ASN_UNIVERSAL, ASN_INTEGER32, 0	45	ber_is $msg->[0], ASN_UNIVERSAL, ASN_INTEGER32, 0
16	or die "SNMP message does not start with snmp version\n";	46	or die "SNMP message does not start with snmp version\n";
17		47
		48	# message is SNMP v1 or v2c?
18	if ($msg->[0][BER_DATA] == 0 \|\| $msg->[0][BER_DATA] == 1) {	49	if ($msg->[0][BER_DATA] == 0 \|\| $msg->[0][BER_DATA] == 1) {
		50
19	# message is SNMP v1 or v2c	51	# message is v1 trap?
20
21	if (ber_is $msg->[2], ASN_CONTEXT, 4, 1) {	52	if (ber_is $msg->[2], ASN_CONTEXT, 4, 1) {
22	# message is v1 trap
23	my $trap = $msg->[2][BER_DATA];	53	my $trap = $msg->[2][BER_DATA];
24		54
25	# check whether trap is a cisco mac notification mac changed message	55	# check whether trap is a cisco mac notification mac changed message
26	if (	56	if (
27	(ber_is_oid $trap->[0], "1.3.6.1.4.1.9.9.215.2") # cmnInterfaceObjects	57	(ber_is_oid $trap->[0], "1.3.6.1.4.1.9.9.215.2") # cmnInterfaceObjects
28	and (ber_is_i32 $trap->[2], 6)	58	and (ber_is_i32 $trap->[2], 6)
29	and (ber_is_i32 $trap->[3], 1) # mac changed msg	59	and (ber_is_i32 $trap->[3], 1) # mac changed msg
30	) {	60	) {
31	... and so on	61	... and so on
32		62
		63	# finally, let's encode it again and hope it results in the same bit pattern
		64
		65	my $buf = ber_encode $ber;
		66
33	=head1 DESCRIPTION	67	=head1 DESCRIPTION
34		68
35	This module implements a I<very> low level BER/DER decoder, and in the	69	This module implements a I<very> low level BER/DER en-/decoder.
36	future, probably also an encoder (tell me if you want an encoder, this
37	might speed up the process of getting one).
38		70
39	If is tuned for low memory and high speed, while still maintaining some	71	If is tuned for low memory and high speed, while still maintaining some
40	level of user-friendlyness.	72	level of user-friendlyness.
41		73
42	Currently, not much is documented, as this is an initial release to	74	Currently, not much is documented, as this is an initial release to
43	reserve CPAN namespace, stay tuned for a few days.	75	reserve CPAN namespace, stay tuned for a few days.
44		76
		77	=head2 ASN.1/BER/DER/... BASICS
		78
		79	ASN.1 is a strange language that can be sed to describe protocols and
		80	data structures. It supports various mappings to JSON, XML, but most
		81	importantly, to a various binary encodings such as BER, that is the topic
		82	of this module, and is used in SNMP or LDAP for example.
		83
		84	While ASN.1 defines a schema that is useful to interpret encoded data,
		85	the BER encoding is actually somehat self-describing: you might not know
		86	whether something is a string or a number or a sequence or something else,
		87	but you can nevertheless decode the overall structure, even if you end up
		88	with just a binary blob for the actual value.
		89
		90	This works because BER values are tagged with a type and a namespace,
		91	and also have a flag that says whther a value consists of subvalues (is
		92	"constructed") or not (is "primitive").
		93
		94	Tags are simple integers, and ASN.1 defines a somewhat weird assortment of
		95	those - for example, you have 32 bit signed integers and 16(!) different
		96	string types, but there is no unsigned32 type for example. Different
		97	applications work around this in different ways, for example, SNMP defines
		98	application-specific Gauge32, Counter32 and Unsigned32, which are mapped
		99	to two different tags: you can distinguish between Counter32 and the
		100	others, but not between Gause32 and Unsigned32, without the ASN.1 schema.
		101
		102	Ugh.
		103
		104	=head2 DECODED BER REPRESENTATION
		105
		106	This module represents every BER value as a 4-element tuple (actually an
		107	array-reference):
		108
		109	[CLASS, TAG, CONSTRUCTED, DATA]
		110
		111	To avoid non-descriptive hardcoded array index numbers, this module
		112	defines symbolic constants to access these members: C<BER_CLASS>,
		113	C<BER_TAG>, C<BER_CONSTRUCTED> and C<BER_DATA>.
		114
		115	Also, the first three members are integers with a little caveat: for
		116	performance reasons, these are readonly and shared, so you must not modify
		117	them (increment, assign to them etc.) in any way. You may modify the
		118	I<DATA> member, and you may re-assign the array itself, e.g.:
		119
		120	$ber = ber_decode $binbuf;
		121
		122	# the following is NOT legal:
		123	$ber->[BER_CLASS] = ASN_PRIVATE; # ERROR, readonly(!)
		124
		125	# but all of the following are fine:
		126	$ber->[BER_DATA] = "string";
		127	$ber->[BER_DATA] = [ASN_UNIVERSAL, ASN_INTEGER32, 0, 123];
		128	@$ber = (ASN_APPLICATION, SNMP_TIMETICKS, 1000);
		129
		130	I<CLASS> is something like a namespace for I<TAG>s - there is the
		131	C<ASN_UNIVERSAL> namespace which defines tags common to all ASN.1
		132	implementations, the C<ASN_APPLICATION> namespace which defines tags for
		133	specific applications (for example, the SNMP C<Unsigned32> type is in this
		134	namespace), a special-purpose context namespace (C<ASN_CONTEXT>, used e.g.
		135	for C<CHOICE>) and a private namespace (C<ASN_PRIVATE>).
		136
		137	The meaning of the I<TAG> depends on the namespace, and defines a
		138	(partial) interpretation of the data value. For example, right now, SNMP
		139	application namespace knowledge ix hardcoded into this module, so it
		140	knows that SNMP C<Unsigned32> values need to be decoded into actual perl
		141	integers.
		142
		143	The most common tags in the C<ASN_UNIVERSAL> namespace are
		144	C<ASN_INTEGER32>, C<ASN_BIT_STRING>, C<ASN_NULL>, C<ASN_OCTET_STRING>,
		145	C<ASN_OBJECT_IDENTIFIER>, C<ASN_SEQUENCE>, C<ASN_SET> and
		146	C<ASN_IA5_STRING>.
		147
		148	The most common tags in SNMP's C<ASN_APPLICATION> namespace
		149	are C<SNMP_IPADDRESS>, C<SNMP_COUNTER32>, C<SNMP_UNSIGNED32>,
		150	C<SNMP_TIMETICKS>, C<SNMP_OPAQUE> and C<SNMP_COUNTER64>.
		151
		152	The I<CONSTRUCTED> flag is really just a boolean - if it is false, the
		153	the value is "primitive" and contains no subvalues, kind of like a
		154	non-reference perl scalar. IF it is true, then the value is "constructed"
		155	which just means it contains a list of subvalues which this module will
		156	en-/decode as BER tuples themselves.
		157
		158	The I<DATA> value is either a reference to an array of further tuples (if
		159	the value is I<CONSTRUCTED>), some decoded representation of the value,
		160	if this module knows how to decode it (e.g. for the integer types above)
		161	or a binary string with the raw octets if this module doesn't know how to
		162	interpret the namespace/tag.
		163
		164	Thus, you can always decode a BER data structure and at worst you get a
		165	string in place of some nice decoded value.
		166
		167	See the SYNOPSIS for an example of such an encoded tuple representation.
		168
		169	=head2 HELPER FUNCTIONS
		170
		171	Working with a 4-tuple for every value can be annoying. Or, rather, I<is>
		172	annoying. To reduce this a bit, this module defines a number of helper
		173	functions, both to match BER tuples and to conmstruct BER tuples:
		174
		175	=head3 MATCH HELPERS
		176
		177	Thse functions accept a BER tuple as first argument and either paertially
		178	or fully match it. They often come in two forms, one which exactly matches
		179	a value, and one which only matches the type and returns the value.
		180
		181	They do check whether valid tuples are passed in and croak otherwise. As
		182	a ease-of-use exception, they usually also accept C<undef> instead of a
		183	tuple reference. in which case they silently fail to match.
		184
		185	=over
		186
		187	=item $bool = ber_is $tuple, $class, $tag, $constructed, $data
		188
		189	This takes a BER C<$tuple> and matches its elements agains the privded
		190	values, all of which are optional - values that are either missing or
		191	C<undef> will be ignored, the others will be matched exactly (e.g. as if
		192	you used C<==> or C<eq> (for C<$data>)).
		193
		194	Some examples:
		195
		196	ber_is $tuple, ASN_UNIVERSAL, ASN_SEQUENCE, 1
		197	orf die "tuple is not an ASN SEQUENCE";
		198
		199	ber_is $tuple, ASN_UNIVERSAL, ASN_NULL
		200	or die "tuple is not an ASN NULL value";
		201
		202	ber_is $tuple, ASN_UNIVERSAL, ASN_INTEGER32, 0, 50
		203	or die "BER integer must be 50";
		204
		205	=item $seq = ber_is_seq $tuple
		206
		207	Returns the sequence members (the array of subvalues) if the C<$tuple> is
		208	an ASN SEQUENCE, i.e. the C<BER_DATA> member. If the C<$tuple> is not a
		209	sequence it returns C<undef>. For example, SNMP version 1/2c/3 packets all
		210	consist of an outer SEQUENCE value:
		211
		212	my $ber = ber_decode $snmp_data;
		213
		214	my $snmp = ber_is_seq $ber
		215	or die "SNMP packet invalid: does not start with SEQUENCE";
		216
		217	# now we know $snmp is a sequence, so decode the SNMP version
		218
		219	my $version = ber_is_i32 $snmp->[0]
		220	or die "SNMP packet invalid: does not start with version number";
		221
		222	=item $bool = ber_is_i32 $tuple, $i32
		223
		224	Returns a true value if the C<$tuple> represents an ASN INTEGER32 with
		225	the value C<$i32>.
		226
		227	=item $i32 = ber_is_i32 $tuple
		228
		229	Returns true (and extracts the integer value) if the C<$tuple> is an ASN
		230	INTEGER32. For C<0>, this function returns a special value that is 0 but
		231	true.
		232
		233	=item $bool = ber_is_oid $tuple, $oid_string
		234
		235	Returns true if the C<$tuple> represents an ASN_OBJECT_IDENTIFIER
		236	that exactly matches C$oid_string>. Exmaple:
		237
		238	ber_is_oid $tuple, "1.3.6.1.4"
		239	or die "oid must be 1.3.6.1.4";
		240
		241	=item $oid = ber_is_oid $tuple
		242
		243	Returns true (and extracts the OID string) if the C<$tuple> is an ASN
		244	OBJECT IDENTIFIER. Otherwise, it returns C<undef>.
		245
		246	=back
		247
		248	=head3 CONSTRUCTION HELPERS
		249
		250	=over
		251
		252	=item $tuple = ber_i32 $value
		253
		254	Constructs a new C<ASN_INTEGER32> tuple.
		255
		256	=back
		257
		258	=head2 RELATIONSHIP TO L<Convert::BER> and L<Convert::ASN1>
		259
		260	This module is I<not> the XS version of L<Convert::BER>, but a different
		261	take at doing the same thing. I imagine this module would be a good base
		262	for speeding up either of these, or write a similar module, or write your
		263	own LDAP or SNMP module for example.
		264
45	=cut	265	=cut
46		266
47	package Convert::BER::XS;	267	package Convert::BER::XS;
48		268
49	use common::sense;	269	use common::sense;
50		270
51	use XSLoader ();	271	use XSLoader ();
52	use Exporter qw(import);	272	use Exporter qw(import);
53		273
54	our $VERSION = '0.0';	274	our $VERSION = 0.1;
55		275
56	XSLoader::load __PACKAGE__, $VERSION;	276	XSLoader::load __PACKAGE__, $VERSION;
57		277
58	our %EXPORT_TAGS = (	278	our %EXPORT_TAGS = (
59	all => [qw(	279	const => [qw(
		280	BER_CLASS BER_TAG BER_CONSTRUCTED BER_DATA
		281
		282	ASN_BOOLEAN ASN_INTEGER32 ASN_BIT_STRING ASN_OCTET_STRING ASN_NULL ASN_OBJECT_IDENTIFIER ASN_TAG_BER ASN_TAG_MASK
		283	ASN_CONSTRUCTED ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE ASN_CLASS_MASK ASN_CLASS_SHIFT
		284	ASN_SEQUENCE
		285
		286	SNMP_IPADDRESS SNMP_COUNTER32 SNMP_UNSIGNED32 SNMP_TIMETICKS SNMP_OPAQUE SNMP_COUNTER64
		287	)],
		288	encode => [qw(
60	ber_decode	289	ber_decode
61	ber_is ber_is_seq ber_is_i32 ber_is_oid	290	ber_is ber_is_seq ber_is_i32 ber_is_oid
62	BER_CLASS BER_TAG BER_CONSTRUCTED BER_DATA	291	)],
63	ASN_BOOLEAN ASN_INTEGER32 ASN_BIT_STRING ASN_OCTET_STRING ASN_NULL ASN_OBJECT_IDENTIFIER ASN_TAG_BER ASN_TAG_MASK	292	decode => [qw(
64	ASN_CONSTRUCTED ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE ASN_CLASS_MASK ASN_CLASS_SHIFT	293	ber_encode
65	ASN_SEQUENCE ASN_IPADDRESS ASN_COUNTER32 ASN_UNSIGNED32 ASN_TIMETICKS ASN_OPAQUE ASN_COUNTER64
66	)],	294	)],
67	);	295	);
68		296
69	our @EXPORT_OK = map @$_, values %EXPORT_TAGS;	297	our @EXPORT_OK = map @$_, values %EXPORT_TAGS;
70		298
		299	$EXPORT_TAGS{all} = \@EXPORT_OK;
		300
71	1;	301	1;
		302
		303	=head2 BUGS / SHORTCOMINGs
		304
		305	This module does have a number of SNMPisms hardcoded, such as the SNMP
		306	tags for Unsigned32 and so on. More configurability is needed, and, if
		307	ever implemented, will come in a form similar to how L<JSON::XS> and
		308	L<CBOR::XS> respresent things, namely with an object-oriented interface.
72		309
73	=head1 AUTHOR	310	=head1 AUTHOR
74		311
75	Marc Lehmann <schmorp@schmorp.de>	312	Marc Lehmann <schmorp@schmorp.de>
76	http://software.schmorp.de/pkg/Convert-BER-XS	313	http://software.schmorp.de/pkg/Convert-BER-XS

Diff Legend

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

Comparing Convert-BER-XS/XS.pm (file contents): Revision 1.1 by root, Fri Apr 19 16:19:36 2019 UTC vs. Revision 1.6 by root, Fri Apr 19 20:38:38 2019 UTC

Diff Legend

Comparing Convert-BER-XS/XS.pm (file contents):
Revision 1.1 by root, Fri Apr 19 16:19:36 2019 UTC vs.
Revision 1.6 by root, Fri Apr 19 20:38:38 2019 UTC