1 |
=head1 NAME |
2 |
|
3 |
Convert::BER::XS - I<very> low level BER en-/decoding |
4 |
|
5 |
=head1 SYNOPSIS |
6 |
|
7 |
use Convert::BER::XS ':all'; |
8 |
|
9 |
my $ber = ber_decode $buf, $Convert::BER::XS::SNMP_PROFILE |
10 |
or die "unable to decode SNMP message"; |
11 |
|
12 |
# The above results in a data structure consisting of |
13 |
# (class, tag, # constructed, data) |
14 |
# tuples. Below is such a message, SNMPv1 trap |
15 |
# with a Cisco mac change notification. |
16 |
# Did you know that Cisco is in the news almost |
17 |
# every week because of some backdoor password |
18 |
# or other extremely stupid security bug? |
19 |
|
20 |
[ ASN_UNIVERSAL, ASN_SEQUENCE, 1, |
21 |
[ |
22 |
[ ASN_UNIVERSAL, ASN_INTEGER32, 0, 0 ], # snmp version 1 |
23 |
[ ASN_UNIVERSAL, 4, 0, "public" ], # community |
24 |
[ ASN_CONTEXT, 4, 1, # CHOICE, constructed - trap PDU |
25 |
[ |
26 |
[ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.2" ], # enterprise oid |
27 |
[ ASN_APPLICATION, SNMP_IPADDRESS, 0, "10.0.0.1" ], # SNMP IpAddress |
28 |
[ ASN_UNIVERSAL, ASN_INTEGER32, 0, 6 ], # generic trap |
29 |
[ ASN_UNIVERSAL, ASN_INTEGER32, 0, 1 ], # specific trap |
30 |
[ ASN_APPLICATION, SNMP_TIMETICKS, 0, 1817903850 ], # SNMP TimeTicks |
31 |
[ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # the varbindlist |
32 |
[ |
33 |
[ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # a single varbind, "key value" pair |
34 |
[ |
35 |
[ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.1.1.8.1.2.1" ], |
36 |
[ ASN_UNIVERSAL, ASN_OCTET_STRING, 0, "...data..." # the value |
37 |
] |
38 |
] |
39 |
], |
40 |
... |
41 |
|
42 |
# let's decode it a bit with some helper functions |
43 |
|
44 |
my $msg = ber_is_seq $ber |
45 |
or die "SNMP message does not start with a sequence"; |
46 |
|
47 |
ber_is $msg->[0], ASN_UNIVERSAL, ASN_INTEGER32, 0 |
48 |
or die "SNMP message does not start with snmp version\n"; |
49 |
|
50 |
# message is SNMP v1 or v2c? |
51 |
if ($msg->[0][BER_DATA] == 0 || $msg->[0][BER_DATA] == 1) { |
52 |
|
53 |
# message is v1 trap? |
54 |
if (ber_is $msg->[2], ASN_CONTEXT, 4, 1) { |
55 |
my $trap = $msg->[2][BER_DATA]; |
56 |
|
57 |
# check whether trap is a cisco mac notification mac changed message |
58 |
if ( |
59 |
(ber_is_oid $trap->[0], "1.3.6.1.4.1.9.9.215.2") # cmnInterfaceObjects |
60 |
and (ber_is_i32 $trap->[2], 6) |
61 |
and (ber_is_i32 $trap->[3], 1) # mac changed msg |
62 |
) { |
63 |
... and so on |
64 |
|
65 |
# finally, let's encode it again and hope it results in the same bit pattern |
66 |
|
67 |
my $buf = ber_encode $ber, $Convert::BER::XS::SNMP_PROFILE; |
68 |
|
69 |
=head1 DESCRIPTION |
70 |
|
71 |
WARNING: Before release 1.0, the API is not considered stable in any way. |
72 |
|
73 |
This module implements a I<very> low level BER/DER en-/decoder. |
74 |
|
75 |
It is tuned for low memory and high speed, while still maintaining some |
76 |
level of user-friendlyness. |
77 |
|
78 |
=head2 EXPORT TAGS AND CONSTANTS |
79 |
|
80 |
By default this module doesn't export any symbols, but if you don't want |
81 |
to break your keyboard, editor or eyesigh with extreemly long names, I |
82 |
recommend importing the C<:all> tag. Still, you can selectively import |
83 |
things: |
84 |
|
85 |
=over |
86 |
|
87 |
=item :all |
88 |
|
89 |
All of the below. Really. Rcommended for at least first steps, or if you |
90 |
don't care about a few kilobytes of wasted memory (and namespace). |
91 |
|
92 |
=item :const |
93 |
|
94 |
All of the stricly ASN.1-related constants defined by this module, the |
95 |
same as C<:const_asn :const_index>. Notably, this does not contain |
96 |
C<:const_ber_type> and C<:const_snmp>. |
97 |
|
98 |
A good set to get everything you need to decode and match BER data would be |
99 |
C<:decode :const>. |
100 |
|
101 |
=item C<:const_index>> |
102 |
|
103 |
The BER tuple array index constants: |
104 |
|
105 |
BER_CLASS BER_TAG BER_CONSTRUCTED BER_DATA |
106 |
|
107 |
=item C<:const_asn> |
108 |
|
109 |
ASN class values (these are C<0>, C<1>, C<2> and C<3>, reespectively - |
110 |
exactly thw two topmost bits from the identifdier octet shifted 6 bits to |
111 |
the right): |
112 |
|
113 |
ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE |
114 |
|
115 |
ASN tag values (some of which are aliases, such as C<ASN_OID>). Their |
116 |
numerical value corresponds exactly to the numbers used in BER/X.690. |
117 |
|
118 |
ASN_BOOLEAN ASN_INTEGER32 ASN_BIT_STRING ASN_OCTET_STRING ASN_NULL ASN_OBJECT_IDENTIFIER |
119 |
ASN_OBJECT_DESCRIPTOR ASN_OID ASN_EXTERNAL ASN_REAL ASN_SEQUENCE ASN_ENUMERATED |
120 |
ASN_EMBEDDED_PDV ASN_UTF8_STRING ASN_RELATIVE_OID ASN_SET ASN_NUMERIC_STRING |
121 |
ASN_PRINTABLE_STRING ASN_TELETEX_STRING ASN_T61_STRING ASN_VIDEOTEX_STRING ASN_IA5_STRING |
122 |
ASN_ASCII_STRING ASN_UTC_TIME ASN_GENERALIZED_TIME ASN_GRAPHIC_STRING ASN_VISIBLE_STRING |
123 |
ASN_ISO646_STRING ASN_GENERAL_STRING ASN_UNIVERSAL_STRING ASN_CHARACTER_STRING ASN_BMP_STRING |
124 |
|
125 |
=item C<:const_ber_type> |
126 |
|
127 |
The BER type constants, explained in the PROFILES section. |
128 |
|
129 |
BER_TYPE_BYTES BER_TYPE_UTF8 BER_TYPE_UCS2 BER_TYPE_UCS4 BER_TYPE_INT |
130 |
BER_TYPE_OID BER_TYPE_RELOID BER_TYPE_NULL BER_TYPE_BOOL BER_TYPE_REAL |
131 |
BER_TYPE_IPADDRESS BER_TYPE_CROAK |
132 |
|
133 |
=item C<:const_snmp> |
134 |
|
135 |
Constants only relevant to SNMP. These are the tag values used by SNMP in |
136 |
the C<ASN_APPLICATION> namespace and have the exact numerical value as in |
137 |
BER/RFC 2578. |
138 |
|
139 |
SNMP_IPADDRESS SNMP_COUNTER32 SNMP_UNSIGNED32 SNMP_TIMETICKS SNMP_OPAQUE SNMP_COUNTER64 |
140 |
|
141 |
=item C<:decode> |
142 |
|
143 |
C<ber_decode> and the match helper functions: |
144 |
|
145 |
ber_decode ber_is ber_is_seq ber_is_i32 ber_is_oid |
146 |
|
147 |
=item C<:encode> |
148 |
|
149 |
C<ber_encode> and the construction helper functions: |
150 |
|
151 |
ber_encode ber_i32 |
152 |
|
153 |
=back |
154 |
|
155 |
=head2 ASN.1/BER/DER/... BASICS |
156 |
|
157 |
ASN.1 is a strange language that can be used to describe protocols and |
158 |
data structures. It supports various mappings to JSON, XML, but most |
159 |
importantly, to a various binary encodings such as BER, that is the topic |
160 |
of this module, and is used in SNMP or LDAP for example. |
161 |
|
162 |
While ASN.1 defines a schema that is useful to interpret encoded data, |
163 |
the BER encoding is actually somewhat self-describing: you might not know |
164 |
whether something is a string or a number or a sequence or something else, |
165 |
but you can nevertheless decode the overall structure, even if you end up |
166 |
with just a binary blob for the actual value. |
167 |
|
168 |
This works because BER values are tagged with a type and a namespace, |
169 |
and also have a flag that says whether a value consists of subvalues (is |
170 |
"constructed") or not (is "primitive"). |
171 |
|
172 |
Tags are simple integers, and ASN.1 defines a somewhat weird assortment of |
173 |
those - for example, you have 32 bit signed integers and 16(!) different |
174 |
string types, but there is no unsigned32 type for example. Different |
175 |
applications work around this in different ways, for example, SNMP defines |
176 |
application-specific Gauge32, Counter32 and Unsigned32, which are mapped |
177 |
to two different tags: you can distinguish between Counter32 and the |
178 |
others, but not between Gause32 and Unsigned32, without the ASN.1 schema. |
179 |
|
180 |
Ugh. |
181 |
|
182 |
=head2 DECODED BER REPRESENTATION |
183 |
|
184 |
This module represents every BER value as a 4-element tuple (actually an |
185 |
array-reference): |
186 |
|
187 |
[CLASS, TAG, CONSTRUCTED, DATA] |
188 |
|
189 |
To avoid non-descriptive hardcoded array index numbers, this module |
190 |
defines symbolic constants to access these members: C<BER_CLASS>, |
191 |
C<BER_TAG>, C<BER_CONSTRUCTED> and C<BER_DATA>. |
192 |
|
193 |
Also, the first three members are integers with a little caveat: for |
194 |
performance reasons, these are readonly and shared, so you must not modify |
195 |
them (increment, assign to them etc.) in any way. You may modify the |
196 |
I<DATA> member, and you may re-assign the array itself, e.g.: |
197 |
|
198 |
$ber = ber_decode $binbuf; |
199 |
|
200 |
# the following is NOT legal: |
201 |
$ber->[BER_CLASS] = ASN_PRIVATE; # ERROR, CLASS/TAG/CONSTRUCTED are READ ONLY(!) |
202 |
|
203 |
# but all of the following are fine: |
204 |
$ber->[BER_DATA] = "string"; |
205 |
$ber->[BER_DATA] = [ASN_UNIVERSAL, ASN_INTEGER32, 0, 123]; |
206 |
@$ber = (ASN_APPLICATION, SNMP_TIMETICKS, 0, 1000); |
207 |
|
208 |
I<CLASS> is something like a namespace for I<TAG>s - there is the |
209 |
C<ASN_UNIVERSAL> namespace which defines tags common to all ASN.1 |
210 |
implementations, the C<ASN_APPLICATION> namespace which defines tags for |
211 |
specific applications (for example, the SNMP C<Unsigned32> type is in this |
212 |
namespace), a special-purpose context namespace (C<ASN_CONTEXT>, used e.g. |
213 |
for C<CHOICE>) and a private namespace (C<ASN_PRIVATE>). |
214 |
|
215 |
The meaning of the I<TAG> depends on the namespace, and defines a |
216 |
(partial) interpretation of the data value. For example, right now, SNMP |
217 |
application namespace knowledge ix hardcoded into this module, so it |
218 |
knows that SNMP C<Unsigned32> values need to be decoded into actual perl |
219 |
integers. |
220 |
|
221 |
The most common tags in the C<ASN_UNIVERSAL> namespace are |
222 |
C<ASN_INTEGER32>, C<ASN_BIT_STRING>, C<ASN_NULL>, C<ASN_OCTET_STRING>, |
223 |
C<ASN_OBJECT_IDENTIFIER>, C<ASN_SEQUENCE>, C<ASN_SET> and |
224 |
C<ASN_IA5_STRING>. |
225 |
|
226 |
The most common tags in SNMP's C<ASN_APPLICATION> namespace |
227 |
are C<SNMP_IPADDRESS>, C<SNMP_COUNTER32>, C<SNMP_UNSIGNED32>, |
228 |
C<SNMP_TIMETICKS>, C<SNMP_OPAQUE> and C<SNMP_COUNTER64>. |
229 |
|
230 |
The I<CONSTRUCTED> flag is really just a boolean - if it is false, the |
231 |
the value is "primitive" and contains no subvalues, kind of like a |
232 |
non-reference perl scalar. IF it is true, then the value is "constructed" |
233 |
which just means it contains a list of subvalues which this module will |
234 |
en-/decode as BER tuples themselves. |
235 |
|
236 |
The I<DATA> value is either a reference to an array of further tuples (if |
237 |
the value is I<CONSTRUCTED>), some decoded representation of the value, |
238 |
if this module knows how to decode it (e.g. for the integer types above) |
239 |
or a binary string with the raw octets if this module doesn't know how to |
240 |
interpret the namespace/tag. |
241 |
|
242 |
Thus, you can always decode a BER data structure and at worst you get a |
243 |
string in place of some nice decoded value. |
244 |
|
245 |
See the SYNOPSIS for an example of such an encoded tuple representation. |
246 |
|
247 |
=head2 DECODING AND ENCODING |
248 |
|
249 |
=over |
250 |
|
251 |
=item $tuple = ber_decoded $bindata |
252 |
|
253 |
Decodes binary BER data in C<$bindata> and returns the resulting BER |
254 |
tuple. Croaks on any decoding error, so the returned C<$tuple> is always |
255 |
valid. |
256 |
|
257 |
=item $bindata = ber_encode $tuple |
258 |
|
259 |
Encodes the BER tuple into a BER/DER data structure. |
260 |
|
261 |
=back |
262 |
|
263 |
=head2 HELPER FUNCTIONS |
264 |
|
265 |
Working with a 4-tuple for every value can be annoying. Or, rather, I<is> |
266 |
annoying. To reduce this a bit, this module defines a number of helper |
267 |
functions, both to match BER tuples and to conmstruct BER tuples: |
268 |
|
269 |
=head3 MATCH HELPERS |
270 |
|
271 |
Thse functions accept a BER tuple as first argument and either paertially |
272 |
or fully match it. They often come in two forms, one which exactly matches |
273 |
a value, and one which only matches the type and returns the value. |
274 |
|
275 |
They do check whether valid tuples are passed in and croak otherwise. As |
276 |
a ease-of-use exception, they usually also accept C<undef> instead of a |
277 |
tuple reference. in which case they silently fail to match. |
278 |
|
279 |
=over |
280 |
|
281 |
=item $bool = ber_is $tuple, $class, $tag, $constructed, $data |
282 |
|
283 |
This takes a BER C<$tuple> and matches its elements agains the privded |
284 |
values, all of which are optional - values that are either missing or |
285 |
C<undef> will be ignored, the others will be matched exactly (e.g. as if |
286 |
you used C<==> or C<eq> (for C<$data>)). |
287 |
|
288 |
Some examples: |
289 |
|
290 |
ber_is $tuple, ASN_UNIVERSAL, ASN_SEQUENCE, 1 |
291 |
orf die "tuple is not an ASN SEQUENCE"; |
292 |
|
293 |
ber_is $tuple, ASN_UNIVERSAL, ASN_NULL |
294 |
or die "tuple is not an ASN NULL value"; |
295 |
|
296 |
ber_is $tuple, ASN_UNIVERSAL, ASN_INTEGER32, 0, 50 |
297 |
or die "BER integer must be 50"; |
298 |
|
299 |
=item $seq = ber_is_seq $tuple |
300 |
|
301 |
Returns the sequence members (the array of subvalues) if the C<$tuple> is |
302 |
an ASN SEQUENCE, i.e. the C<BER_DATA> member. If the C<$tuple> is not a |
303 |
sequence it returns C<undef>. For example, SNMP version 1/2c/3 packets all |
304 |
consist of an outer SEQUENCE value: |
305 |
|
306 |
my $ber = ber_decode $snmp_data; |
307 |
|
308 |
my $snmp = ber_is_seq $ber |
309 |
or die "SNMP packet invalid: does not start with SEQUENCE"; |
310 |
|
311 |
# now we know $snmp is a sequence, so decode the SNMP version |
312 |
|
313 |
my $version = ber_is_i32 $snmp->[0] |
314 |
or die "SNMP packet invalid: does not start with version number"; |
315 |
|
316 |
=item $bool = ber_is_i32 $tuple, $i32 |
317 |
|
318 |
Returns a true value if the C<$tuple> represents an ASN INTEGER32 with |
319 |
the value C<$i32>. |
320 |
|
321 |
=item $i32 = ber_is_i32 $tuple |
322 |
|
323 |
Returns true (and extracts the integer value) if the C<$tuple> is an ASN |
324 |
INTEGER32. For C<0>, this function returns a special value that is 0 but |
325 |
true. |
326 |
|
327 |
=item $bool = ber_is_oid $tuple, $oid_string |
328 |
|
329 |
Returns true if the C<$tuple> represents an ASN_OBJECT_IDENTIFIER |
330 |
that exactly matches C<$oid_string>. Example: |
331 |
|
332 |
ber_is_oid $tuple, "1.3.6.1.4" |
333 |
or die "oid must be 1.3.6.1.4"; |
334 |
|
335 |
=item $oid = ber_is_oid $tuple |
336 |
|
337 |
Returns true (and extracts the OID string) if the C<$tuple> is an ASN |
338 |
OBJECT IDENTIFIER. Otherwise, it returns C<undef>. |
339 |
|
340 |
=back |
341 |
|
342 |
=head3 CONSTRUCTION HELPERS |
343 |
|
344 |
=over |
345 |
|
346 |
=item $tuple = ber_i32 $value |
347 |
|
348 |
Constructs a new C<ASN_INTEGER32> tuple. |
349 |
|
350 |
=back |
351 |
|
352 |
=head2 RELATIONSHIP TO L<Convert::BER> and L<Convert::ASN1> |
353 |
|
354 |
This module is I<not> the XS version of L<Convert::BER>, but a different |
355 |
take at doing the same thing. I imagine this module would be a good base |
356 |
for speeding up either of these, or write a similar module, or write your |
357 |
own LDAP or SNMP module for example. |
358 |
|
359 |
=cut |
360 |
|
361 |
package Convert::BER::XS; |
362 |
|
363 |
use common::sense; |
364 |
|
365 |
use XSLoader (); |
366 |
use Exporter qw(import); |
367 |
|
368 |
our $VERSION; |
369 |
|
370 |
BEGIN { |
371 |
$VERSION = 0.8; |
372 |
XSLoader::load __PACKAGE__, $VERSION; |
373 |
} |
374 |
|
375 |
our %EXPORT_TAGS = ( |
376 |
const_index => [qw( |
377 |
BER_CLASS BER_TAG BER_CONSTRUCTED BER_DATA |
378 |
)], |
379 |
const_asn => [qw( |
380 |
ASN_BOOLEAN ASN_INTEGER32 ASN_BIT_STRING ASN_OCTET_STRING ASN_NULL ASN_OBJECT_IDENTIFIER |
381 |
ASN_OBJECT_DESCRIPTOR ASN_OID ASN_EXTERNAL ASN_REAL ASN_SEQUENCE ASN_ENUMERATED |
382 |
ASN_EMBEDDED_PDV ASN_UTF8_STRING ASN_RELATIVE_OID ASN_SET ASN_NUMERIC_STRING |
383 |
ASN_PRINTABLE_STRING ASN_TELETEX_STRING ASN_T61_STRING ASN_VIDEOTEX_STRING ASN_IA5_STRING |
384 |
ASN_ASCII_STRING ASN_UTC_TIME ASN_GENERALIZED_TIME ASN_GRAPHIC_STRING ASN_VISIBLE_STRING |
385 |
ASN_ISO646_STRING ASN_GENERAL_STRING ASN_UNIVERSAL_STRING ASN_CHARACTER_STRING ASN_BMP_STRING |
386 |
|
387 |
ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE |
388 |
)], |
389 |
const_ber_type => [qw( |
390 |
BER_TYPE_BYTES BER_TYPE_UTF8 BER_TYPE_UCS2 BER_TYPE_UCS4 BER_TYPE_INT |
391 |
BER_TYPE_OID BER_TYPE_RELOID BER_TYPE_NULL BER_TYPE_BOOL BER_TYPE_REAL |
392 |
BER_TYPE_IPADDRESS BER_TYPE_CROAK |
393 |
)], |
394 |
const_snmp => [qw( |
395 |
SNMP_IPADDRESS SNMP_COUNTER32 SNMP_UNSIGNED32 SNMP_TIMETICKS SNMP_OPAQUE SNMP_COUNTER64 |
396 |
)], |
397 |
decode => [qw( |
398 |
ber_decode |
399 |
ber_is ber_is_seq ber_is_i32 ber_is_oid |
400 |
)], |
401 |
encode => [qw( |
402 |
ber_encode |
403 |
ber_i32 |
404 |
)], |
405 |
); |
406 |
|
407 |
our @EXPORT_OK = map @$_, values %EXPORT_TAGS; |
408 |
|
409 |
$EXPORT_TAGS{all} = \@EXPORT_OK; |
410 |
$EXPORT_TAGS{const} = [map @{ $EXPORT_TAGS{$_} }, qw(const_index const_asn)]; |
411 |
use Data::Dump; ddx \%EXPORT_TAGS; |
412 |
|
413 |
=head1 PROFILES |
414 |
|
415 |
While any BER data can be correctly encoded and decoded out of the box, it |
416 |
can be inconvenient to have to manually decode some values into a "better" |
417 |
format: for instance, SNMP TimeTicks values are decoded into the raw octet |
418 |
strings of their BER representation, which is quite hard to decode. With |
419 |
profiles, you can change which class/tag combinations map to which decoder |
420 |
function inside C<ber_decode> (and of course also which encoder functions |
421 |
are used in C<ber_encode>). |
422 |
|
423 |
This works by mapping specific class/tag combinations to an internal "ber |
424 |
type". |
425 |
|
426 |
The default profile supports the standard ASN.1 types, but no |
427 |
application-specific ones. This means that class/tag combinations not in |
428 |
the base set of ASN.1 are decoded into their raw octet strings. |
429 |
|
430 |
C<Convert::BER::XS> defines two profile variables you can use out of the box: |
431 |
|
432 |
=over |
433 |
|
434 |
=item C<$Convert::BER::XS::DEFAULT_PROFILE> |
435 |
|
436 |
This is the default profile, i.e. the profile that is used when no |
437 |
profile is specified for de-/encoding. |
438 |
|
439 |
You can modify it, but remember that this modifies the defaults for all |
440 |
callers that rely on the default profile. |
441 |
|
442 |
=item C<$Convert::BER::XS::SNMP_PROFILE> |
443 |
|
444 |
A profile with mappings for SNMP-specific application tags added. This is |
445 |
useful when de-/encoding SNMP data. |
446 |
|
447 |
Example: |
448 |
|
449 |
$ber = ber_decode $data, $Convert::BER::XS::SNMP_PROFILE; |
450 |
|
451 |
=back |
452 |
|
453 |
=head2 The Convert::BER::XS::Profile class |
454 |
|
455 |
=over |
456 |
|
457 |
=item $profile = new Convert::BER::XS::Profile |
458 |
|
459 |
Create a new profile. The profile will be identical to the default |
460 |
profile. |
461 |
|
462 |
=item $profile->set ($class, $tag, $type) |
463 |
|
464 |
Sets the mapping for the given C<$class>/C<$tag> combination to C<$type>, |
465 |
which must be one of the C<BER_TYPE_*> constants. |
466 |
|
467 |
Note that currently, the mapping is stored in a flat array, so large |
468 |
values of C<$tag> will consume large amounts of memory. |
469 |
|
470 |
Example: |
471 |
|
472 |
$profile = new Convert::BER::XS::Profile; |
473 |
$profile->set (ASN_APPLICATION, SNMP_COUNTER32, BER_TYPE_INT); |
474 |
$ber = ber_decode $data, $profile; |
475 |
|
476 |
=item $type = $profile->get ($class, $tag) |
477 |
|
478 |
Returns the BER type mapped to the given C<$class>/C<$tag> combination. |
479 |
|
480 |
=back |
481 |
|
482 |
=head2 BER TYPES |
483 |
|
484 |
This lists the predefined BER types - you can map any C<CLASS>/C<TAG> |
485 |
combination to any C<BER_TYPE_*>. |
486 |
|
487 |
=over |
488 |
|
489 |
=item C<BER_TYPE_BYTES> |
490 |
|
491 |
The raw octets of the value. This is the default type for unknown tags and |
492 |
de-/encodes the value as if it were an octet string, i.e. by copying the |
493 |
raw bytes. |
494 |
|
495 |
=item C<BER_TYPE_UTF8> |
496 |
|
497 |
Like C<BER_TYPE_BYTES>, but decodes the value as if it were a UTF-8 string |
498 |
(without validation!) and encodes a perl unicode string into a UTF-8 BER |
499 |
string. |
500 |
|
501 |
=item C<BER_TYPE_UCS2> |
502 |
|
503 |
Similar to C<BER_TYPE_UTF8>, but treats the BER value as UCS-2 encoded |
504 |
string. |
505 |
|
506 |
=item C<BER_TYPE_UCS4> |
507 |
|
508 |
Similar to C<BER_TYPE_UTF8>, but treats the BER value as UCS-4 encoded |
509 |
string. |
510 |
|
511 |
=item C<BER_TYPE_INT> |
512 |
|
513 |
Encodes and decodes a BER integer value to a perl integer scalar. This |
514 |
should correctly handle 64 bit signed and unsigned values. |
515 |
|
516 |
=item C<BER_TYPE_OID> |
517 |
|
518 |
Encodes and decodes an OBJECT IDENTIFIER into dotted form without leading |
519 |
dot, e.g. C<1.3.6.1.213>. |
520 |
|
521 |
=item C<BER_TYPE_RELOID> |
522 |
|
523 |
Same as C<BER_TYPE_OID> but uses relative object identifier |
524 |
encoding: ASN.1 has this hack of encoding the first two OID components |
525 |
into a single integer in a weird attempt to save an insignificant amount |
526 |
of space in an otherwise wasteful encoding, and relative OIDs are |
527 |
basically OIDs without this hack. The practical difference is that the |
528 |
second component of an OID can only have the values 1..40, while relative |
529 |
OIDs do not have this restriction. |
530 |
|
531 |
=item C<BER_TYPE_NULL> |
532 |
|
533 |
Decodes an C<ASN_NULL> value into C<undef>, and always encodes a |
534 |
C<ASN_NULL> type, regardless of the perl value. |
535 |
|
536 |
=item C<BER_TYPE_BOOL> |
537 |
|
538 |
Decodes an C<ASN_BOOLEAN> value into C<0> or C<1>, and encodes a perl |
539 |
boolean value into an C<ASN_BOOLEAN>. |
540 |
|
541 |
=item C<BER_TYPE_REAL> |
542 |
|
543 |
Decodes/encodes a BER real value. NOT IMPLEMENTED. |
544 |
|
545 |
=item C<BER_TYPE_IPADDRESS> |
546 |
|
547 |
Decodes/encodes a four byte string into an IPv4 dotted-quad address string |
548 |
in Perl. Given the obsolete nature of this type, this is a low-effort |
549 |
implementation that simply uses C<sprintf> and C<sscanf>-style conversion, |
550 |
so it won't handle all string forms supported by C<inet_aton> for example. |
551 |
|
552 |
=item C<BER_TYPE_CROAK> |
553 |
|
554 |
Always croaks when encountered during encoding or decoding - the |
555 |
default behaviour when encountering an unknown type is to treat it as |
556 |
C<BER_TYPE_BYTES>. When you don't want that but instead prefer a hard |
557 |
error for some types, then C<BER_TYPE_CROAK> is for you. |
558 |
|
559 |
=back |
560 |
|
561 |
=cut |
562 |
|
563 |
our $DEFAULT_PROFILE = new Convert::BER::XS::Profile; |
564 |
our $SNMP_PROFILE = new Convert::BER::XS::Profile; |
565 |
|
566 |
# additional SNMP application types |
567 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_IPADDRESS , BER_TYPE_IPADDRESS); |
568 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER32 , BER_TYPE_INT); |
569 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_UNSIGNED32, BER_TYPE_INT); |
570 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_TIMETICKS , BER_TYPE_INT); |
571 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_OPAQUE , BER_TYPE_IPADDRESS); |
572 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER64 , BER_TYPE_INT); |
573 |
|
574 |
$DEFAULT_PROFILE->_set_default; |
575 |
|
576 |
1; |
577 |
|
578 |
=head2 LIMITATIONS/NOTES |
579 |
|
580 |
This module can only en-/decode 64 bit signed and unsigned integers, and |
581 |
only when your perl supports those. |
582 |
|
583 |
This module does not generally care about ranges, i.e. it will happily |
584 |
de-/encode 64 bit integers into an C<ASN_INTEGER32> value, or a negative |
585 |
number into an C<SNMP_COUNTER64>. |
586 |
|
587 |
OBJECT IDENTIFIEERs cannot have unlimited length, although the limit is |
588 |
much larger than e.g. the one imposed by SNMP or other protocols,a nd is |
589 |
about 4kB. |
590 |
|
591 |
REAL values are not supported and will currently croak. |
592 |
|
593 |
This module has undergone little to no testing so far. |
594 |
|
595 |
=head2 ITHREADS SUPPORT |
596 |
|
597 |
This module is unlikely to work when the (officially discouraged) ithreads |
598 |
are in use. |
599 |
|
600 |
=head1 AUTHOR |
601 |
|
602 |
Marc Lehmann <schmorp@schmorp.de> |
603 |
http://software.schmorp.de/pkg/Convert-BER-XS |
604 |
|
605 |
=cut |
606 |
|