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, flags, 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_INTEGER, 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_INTEGER, 0, 6 ], # generic trap |
29 |
[ ASN_UNIVERSAL, ASN_INTEGER, 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 $msg->[0], ASN_UNIVERSAL, ASN_INTEGER, 0 |
48 |
or die "SNMP message does not start with snmp version\n"; |
49 |
|
50 |
# message is SNMP v1 or v2c? |
51 |
if ($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_int $trap->[2], 6) |
61 |
and (ber_is_int $trap->[3], 1) # mac changed msg |
62 |
) { |
63 |
... and so on |
64 |
|
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# 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 |
|
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=head1 DESCRIPTION |
70 |
|
71 |
WARNING: Before release 1.0, the API is not considered stable in any way. |
72 |
|
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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 eyesight with extremely long names, I |
82 |
recommend importing the C<:all> tag. Still, you can selectively import |
83 |
things. |
84 |
|
85 |
=over |
86 |
|
87 |
=item C<:all> |
88 |
|
89 |
All of the below. Really. Recommended for at least first steps, or if you |
90 |
don't care about a few kilobytes of wasted memory (and namespace). |
91 |
|
92 |
=item C<:const> |
93 |
|
94 |
All of the strictly 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> |
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|
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The BER tuple array index constants: |
104 |
|
105 |
BER_CLASS BER_TAG BER_FLAGS BER_DATA |
106 |
|
107 |
=item C<:const_asn> |
108 |
|
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ASN class values (these are C<0>, C<1>, C<2> and C<3>, respectively - |
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exactly thw two topmost bits from the identifier octet shifted 6 bits to |
111 |
the right): |
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|
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ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE |
114 |
|
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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_INTEGER 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 |
|
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=item C<:const_snmp> |
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|
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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 |
|
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SNMP_IPADDRESS SNMP_COUNTER32 SNMP_UNSIGNED32 SNMP_GAUGE32 |
140 |
SNMP_TIMETICKS SNMP_OPAQUE SNMP_COUNTER64 |
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|
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=item C<:decode> |
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|
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C<ber_decode> and the match helper functions: |
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|
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ber_decode ber-decode_prefix |
147 |
ber_is ber_is_seq ber_is_int ber_is_oid |
148 |
|
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=item C<:encode> |
150 |
|
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C<ber_encode> and the construction helper functions: |
152 |
|
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ber_encode |
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ber_int |
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|
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=back |
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|
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=head2 ASN.1/BER/DER/... BASICS |
159 |
|
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ASN.1 is a strange language that can be used to describe protocols and |
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data structures. It supports various mappings to JSON, XML, but most |
162 |
importantly, to a various binary encodings such as BER, that is the topic |
163 |
of this module, and is used in SNMP, LDAP or X.509 for example. |
164 |
|
165 |
While ASN.1 defines a schema that is useful to interpret encoded data, |
166 |
the BER encoding is actually somewhat self-describing: you might not know |
167 |
whether something is a string or a number or a sequence or something else, |
168 |
but you can nevertheless decode the overall structure, even if you end up |
169 |
with just a binary blob for the actual value. |
170 |
|
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This works because BER values are tagged with a type and a namespace, |
172 |
and also have a flag that says whether a value consists of subvalues (is |
173 |
"constructed") or not (is "primitive"). |
174 |
|
175 |
Tags are simple integers, and ASN.1 defines a somewhat weird assortment |
176 |
of those - for example, you have one integers and 16(!) different |
177 |
string types, but there is no Unsigned32 type for example. Different |
178 |
applications work around this in different ways, for example, SNMP defines |
179 |
application-specific Gauge32, Counter32 and Unsigned32, which are mapped |
180 |
to two different tags: you can distinguish between Counter32 and the |
181 |
others, but not between Gause32 and Unsigned32, without the ASN.1 schema. |
182 |
|
183 |
Ugh. |
184 |
|
185 |
=head2 DECODED BER REPRESENTATION |
186 |
|
187 |
This module represents every BER value as a 4-element tuple (actually an |
188 |
array-reference): |
189 |
|
190 |
[CLASS, TAG, FLAGS, DATA] |
191 |
|
192 |
For example: |
193 |
|
194 |
[ASN_UNIVERSAL, ASN_INTEGER, 0, 177] # the integer 177 |
195 |
[ASN_UNIVERSAL, ASN_OCTET_STRING, 0, "john"] # the string "john" |
196 |
[ASN_UNIVERSAL, ASN_OID, 0, "1.3.6.133"] # some OID |
197 |
[ASN_UNIVERSAL, ASN_SEQUENCE, 1, [ [ASN_UNIVERSAL... # a sequence |
198 |
|
199 |
To avoid non-descriptive hardcoded array index numbers, this module |
200 |
defines symbolic constants to access these members: C<BER_CLASS>, |
201 |
C<BER_TAG>, C<BER_FLAGS> and C<BER_DATA>. |
202 |
|
203 |
Also, the first three members are integers with a little caveat: for |
204 |
performance reasons, these are readonly and shared, so you must not modify |
205 |
them (increment, assign to them etc.) in any way. You may modify the |
206 |
I<DATA> member, and you may re-assign the array itself, e.g.: |
207 |
|
208 |
$ber = ber_decode $binbuf; |
209 |
|
210 |
# the following is NOT legal: |
211 |
$ber->[BER_CLASS] = ASN_PRIVATE; # ERROR, CLASS/TAG/FLAGS are READ ONLY(!) |
212 |
|
213 |
# but all of the following are fine: |
214 |
$ber->[BER_DATA] = "string"; |
215 |
$ber->[BER_DATA] = [ASN_UNIVERSAL, ASN_INTEGER, 0, 123]; |
216 |
@$ber = (ASN_APPLICATION, SNMP_TIMETICKS, 0, 1000); |
217 |
|
218 |
I<CLASS> is something like a namespace for I<TAG>s - there is the |
219 |
C<ASN_UNIVERSAL> namespace which defines tags common to all ASN.1 |
220 |
implementations, the C<ASN_APPLICATION> namespace which defines tags for |
221 |
specific applications (for example, the SNMP C<Unsigned32> type is in this |
222 |
namespace), a special-purpose context namespace (C<ASN_CONTEXT>, used e.g. |
223 |
for C<CHOICE>) and a private namespace (C<ASN_PRIVATE>). |
224 |
|
225 |
The meaning of the I<TAG> depends on the namespace, and defines a |
226 |
(partial) interpretation of the data value. For example, SNMP defines |
227 |
extra tags in the C<ASN_APPLICATION> namespace, and to take full advantage |
228 |
of these, you need to tell this module how to handle those via profiles. |
229 |
|
230 |
The most common tags in the C<ASN_UNIVERSAL> namespace are |
231 |
C<ASN_INTEGER>, C<ASN_BIT_STRING>, C<ASN_NULL>, C<ASN_OCTET_STRING>, |
232 |
C<ASN_OBJECT_IDENTIFIER>, C<ASN_SEQUENCE>, C<ASN_SET> and |
233 |
C<ASN_IA5_STRING>. |
234 |
|
235 |
The most common tags in SNMP's C<ASN_APPLICATION> namespace are |
236 |
C<SNMP_COUNTER32>, C<SNMP_UNSIGNED32>, C<SNMP_TIMETICKS> and |
237 |
C<SNMP_COUNTER64>. |
238 |
|
239 |
The I<FLAGS> value is really just a boolean at this time (but might |
240 |
get extended) - if it is C<0>, the value is "primitive" and contains |
241 |
no subvalues, kind of like a non-reference perl scalar. If it is C<1>, |
242 |
then the value is "constructed" which just means it contains a list of |
243 |
subvalues which this module will en-/decode as BER tuples themselves. |
244 |
|
245 |
The I<DATA> value is either a reference to an array of further tuples |
246 |
(if the value is I<FLAGS>), some decoded representation of the value, if |
247 |
this module knows how to decode it (e.g. for the integer types above) or |
248 |
a binary string with the raw octets if this module doesn't know how to |
249 |
interpret the namespace/tag. |
250 |
|
251 |
Thus, you can always decode a BER data structure and at worst you get a |
252 |
string in place of some nice decoded value. |
253 |
|
254 |
See the SYNOPSIS for an example of such an encoded tuple representation. |
255 |
|
256 |
=head2 DECODING AND ENCODING |
257 |
|
258 |
=over |
259 |
|
260 |
=item $tuple = ber_decode $bindata[, $profile] |
261 |
|
262 |
Decodes binary BER data in C<$bindata> and returns the resulting BER |
263 |
tuple. Croaks on any decoding error, so the returned C<$tuple> is always |
264 |
valid. |
265 |
|
266 |
How tags are interpreted is defined by the second argument, which must |
267 |
be a C<Convert::BER::XS::Profile> object. If it is missing, the default |
268 |
profile will be used (C<$Convert::BER::XS::DEFAULT_PROFILE>). |
269 |
|
270 |
In addition to rolling your own, this module provides a |
271 |
C<$Convert::BER::XS::SNMP_PROFILE> that knows about the additional SNMP |
272 |
types. |
273 |
|
274 |
Example: decode a BER blob using the default profile - SNMP values will be |
275 |
decided as raw strings. |
276 |
|
277 |
$tuple = ber_decode $data; |
278 |
|
279 |
Example: as above, but use the provided SNMP profile. |
280 |
|
281 |
$tuple = ber_encode $data, $Convert::BER::XS::SNMP_PROFILE; |
282 |
|
283 |
=item ($tuple, $bytes) = ber_decode_prefix $bindata[, $profile] |
284 |
|
285 |
Works like C<ber_decode>, except it doesn't croak when there is data after |
286 |
the BER data, but instead returns the decoded value and the number of |
287 |
bytes it decoded. |
288 |
|
289 |
This is useful when you have BER data at the start of a buffer and other |
290 |
data after, and you need to find the length. |
291 |
|
292 |
Also, since BER is self-delimited, this can be used to decode multiple BER |
293 |
values joined together. |
294 |
|
295 |
=item $bindata = ber_encode $tuple[, $profile] |
296 |
|
297 |
Encodes the BER tuple into a BER/DER data structure. AS with |
298 |
Cyber_decode>, an optional profile can be given. |
299 |
|
300 |
The encoded data should be both BER and DER ("shortest form") compliant |
301 |
unless the input says otherwise (e.g. it uses constructed strings). |
302 |
|
303 |
=back |
304 |
|
305 |
=head2 HELPER FUNCTIONS |
306 |
|
307 |
Working with a 4-tuple for every value can be annoying. Or, rather, I<is> |
308 |
annoying. To reduce this a bit, this module defines a number of helper |
309 |
functions, both to match BER tuples and to construct BER tuples: |
310 |
|
311 |
=head3 MATCH HELPERS |
312 |
|
313 |
These functions accept a BER tuple as first argument and either partially |
314 |
or fully match it. They often come in two forms, one which exactly matches |
315 |
a value, and one which only matches the type and returns the value. |
316 |
|
317 |
They do check whether valid tuples are passed in and croak otherwise. As |
318 |
a ease-of-use exception, they usually also accept C<undef> instead of a |
319 |
tuple reference, in which case they silently fail to match. |
320 |
|
321 |
=over |
322 |
|
323 |
=item $bool = ber_is $tuple, $class, $tag, $flags, $data |
324 |
|
325 |
This takes a BER C<$tuple> and matches its elements against the provided |
326 |
values, all of which are optional - values that are either missing or |
327 |
C<undef> will be ignored, the others will be matched exactly (e.g. as if |
328 |
you used C<==> or C<eq> (for C<$data>)). |
329 |
|
330 |
Some examples: |
331 |
|
332 |
ber_is $tuple, ASN_UNIVERSAL, ASN_SEQUENCE, 1 |
333 |
orf die "tuple is not an ASN SEQUENCE"; |
334 |
|
335 |
ber_is $tuple, ASN_UNIVERSAL, ASN_NULL |
336 |
or die "tuple is not an ASN NULL value"; |
337 |
|
338 |
ber_is $tuple, ASN_UNIVERSAL, ASN_INTEGER, 0, 50 |
339 |
or die "BER integer must be 50"; |
340 |
|
341 |
=item $seq = ber_is_seq $tuple |
342 |
|
343 |
Returns the sequence members (the array of subvalues) if the C<$tuple> is |
344 |
an ASN SEQUENCE, i.e. the C<BER_DATA> member. If the C<$tuple> is not a |
345 |
sequence it returns C<undef>. For example, SNMP version 1/2c/3 packets all |
346 |
consist of an outer SEQUENCE value: |
347 |
|
348 |
my $ber = ber_decode $snmp_data; |
349 |
|
350 |
my $snmp = ber_is_seq $ber |
351 |
or die "SNMP packet invalid: does not start with SEQUENCE"; |
352 |
|
353 |
# now we know $snmp is a sequence, so decode the SNMP version |
354 |
|
355 |
my $version = ber_is_int $snmp->[0] |
356 |
or die "SNMP packet invalid: does not start with version number"; |
357 |
|
358 |
=item $bool = ber_is_int $tuple, $int |
359 |
|
360 |
Returns a true value if the C<$tuple> represents an ASN INTEGER with |
361 |
the value C<$int>. |
362 |
|
363 |
=item $int = ber_is_int $tuple |
364 |
|
365 |
Returns true (and extracts the integer value) if the C<$tuple> is an |
366 |
C<ASN_INTEGER>. For C<0>, this function returns a special value that is 0 |
367 |
but true. |
368 |
|
369 |
=item $bool = ber_is_oid $tuple, $oid_string |
370 |
|
371 |
Returns true if the C<$tuple> represents an ASN_OBJECT_IDENTIFIER |
372 |
that exactly matches C<$oid_string>. Example: |
373 |
|
374 |
ber_is_oid $tuple, "1.3.6.1.4" |
375 |
or die "oid must be 1.3.6.1.4"; |
376 |
|
377 |
=item $oid = ber_is_oid $tuple |
378 |
|
379 |
Returns true (and extracts the OID string) if the C<$tuple> is an ASN |
380 |
OBJECT IDENTIFIER. Otherwise, it returns C<undef>. |
381 |
|
382 |
=back |
383 |
|
384 |
=head3 CONSTRUCTION HELPERS |
385 |
|
386 |
=over |
387 |
|
388 |
=item $tuple = ber_int $value |
389 |
|
390 |
Constructs a new C<ASN_INTEGER> tuple. |
391 |
|
392 |
=back |
393 |
|
394 |
=head2 RELATIONSHIP TO L<Convert::BER> and L<Convert::ASN1> |
395 |
|
396 |
This module is I<not> the XS version of L<Convert::BER>, but a different |
397 |
take at doing the same thing. I imagine this module would be a good base |
398 |
for speeding up either of these, or write a similar module, or write your |
399 |
own LDAP or SNMP module for example. |
400 |
|
401 |
=cut |
402 |
|
403 |
package Convert::BER::XS; |
404 |
|
405 |
use common::sense; |
406 |
|
407 |
use XSLoader (); |
408 |
use Exporter qw(import); |
409 |
|
410 |
our $VERSION; |
411 |
|
412 |
BEGIN { |
413 |
$VERSION = 0.9; |
414 |
XSLoader::load __PACKAGE__, $VERSION; |
415 |
} |
416 |
|
417 |
our %EXPORT_TAGS = ( |
418 |
const_index => [qw( |
419 |
BER_CLASS BER_TAG BER_FLAGS BER_DATA |
420 |
)], |
421 |
const_asn => [qw( |
422 |
ASN_BOOLEAN ASN_INTEGER ASN_BIT_STRING ASN_OCTET_STRING ASN_NULL ASN_OBJECT_IDENTIFIER |
423 |
ASN_OBJECT_DESCRIPTOR ASN_OID ASN_EXTERNAL ASN_REAL ASN_SEQUENCE ASN_ENUMERATED |
424 |
ASN_EMBEDDED_PDV ASN_UTF8_STRING ASN_RELATIVE_OID ASN_SET ASN_NUMERIC_STRING |
425 |
ASN_PRINTABLE_STRING ASN_TELETEX_STRING ASN_T61_STRING ASN_VIDEOTEX_STRING ASN_IA5_STRING |
426 |
ASN_ASCII_STRING ASN_UTC_TIME ASN_GENERALIZED_TIME ASN_GRAPHIC_STRING ASN_VISIBLE_STRING |
427 |
ASN_ISO646_STRING ASN_GENERAL_STRING ASN_UNIVERSAL_STRING ASN_CHARACTER_STRING ASN_BMP_STRING |
428 |
|
429 |
ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE |
430 |
)], |
431 |
const_ber_type => [qw( |
432 |
BER_TYPE_BYTES BER_TYPE_UTF8 BER_TYPE_UCS2 BER_TYPE_UCS4 BER_TYPE_INT |
433 |
BER_TYPE_OID BER_TYPE_RELOID BER_TYPE_NULL BER_TYPE_BOOL BER_TYPE_REAL |
434 |
BER_TYPE_IPADDRESS BER_TYPE_CROAK |
435 |
)], |
436 |
const_snmp => [qw( |
437 |
SNMP_IPADDRESS SNMP_COUNTER32 SNMP_GAUGE32 SNMP_UNSIGNED32 |
438 |
SNMP_TIMETICKS SNMP_OPAQUE SNMP_COUNTER64 |
439 |
)], |
440 |
decode => [qw( |
441 |
ber_decode ber_decode_prefix |
442 |
ber_is ber_is_seq ber_is_int ber_is_oid |
443 |
)], |
444 |
encode => [qw( |
445 |
ber_encode |
446 |
ber_int |
447 |
)], |
448 |
); |
449 |
|
450 |
our @EXPORT_OK = map @$_, values %EXPORT_TAGS; |
451 |
|
452 |
$EXPORT_TAGS{all} = \@EXPORT_OK; |
453 |
$EXPORT_TAGS{const} = [map @{ $EXPORT_TAGS{$_} }, qw(const_index const_asn)]; |
454 |
|
455 |
=head1 PROFILES |
456 |
|
457 |
While any BER data can be correctly encoded and decoded out of the box, it |
458 |
can be inconvenient to have to manually decode some values into a "better" |
459 |
format: for instance, SNMP TimeTicks values are decoded into the raw octet |
460 |
strings of their BER representation, which is quite hard to decode. With |
461 |
profiles, you can change which class/tag combinations map to which decoder |
462 |
function inside C<ber_decode> (and of course also which encoder functions |
463 |
are used in C<ber_encode>). |
464 |
|
465 |
This works by mapping specific class/tag combinations to an internal "ber |
466 |
type". |
467 |
|
468 |
The default profile supports the standard ASN.1 types, but no |
469 |
application-specific ones. This means that class/tag combinations not in |
470 |
the base set of ASN.1 are decoded into their raw octet strings. |
471 |
|
472 |
C<Convert::BER::XS> defines two profile variables you can use out of the box: |
473 |
|
474 |
=over |
475 |
|
476 |
=item C<$Convert::BER::XS::DEFAULT_PROFILE> |
477 |
|
478 |
This is the default profile, i.e. the profile that is used when no |
479 |
profile is specified for de-/encoding. |
480 |
|
481 |
You can modify it, but remember that this modifies the defaults for all |
482 |
callers that rely on the default profile. |
483 |
|
484 |
=item C<$Convert::BER::XS::SNMP_PROFILE> |
485 |
|
486 |
A profile with mappings for SNMP-specific application tags added. This is |
487 |
useful when de-/encoding SNMP data. |
488 |
|
489 |
Example: |
490 |
|
491 |
$ber = ber_decode $data, $Convert::BER::XS::SNMP_PROFILE; |
492 |
|
493 |
=back |
494 |
|
495 |
=head2 The Convert::BER::XS::Profile class |
496 |
|
497 |
=over |
498 |
|
499 |
=item $profile = new Convert::BER::XS::Profile |
500 |
|
501 |
Create a new profile. The profile will be identical to the default |
502 |
profile. |
503 |
|
504 |
=item $profile->set ($class, $tag, $type) |
505 |
|
506 |
Sets the mapping for the given C<$class>/C<$tag> combination to C<$type>, |
507 |
which must be one of the C<BER_TYPE_*> constants. |
508 |
|
509 |
Note that currently, the mapping is stored in a flat array, so large |
510 |
values of C<$tag> will consume large amounts of memory. |
511 |
|
512 |
Example: |
513 |
|
514 |
$profile = new Convert::BER::XS::Profile; |
515 |
$profile->set (ASN_APPLICATION, SNMP_COUNTER32, BER_TYPE_INT); |
516 |
$ber = ber_decode $data, $profile; |
517 |
|
518 |
=item $type = $profile->get ($class, $tag) |
519 |
|
520 |
Returns the BER type mapped to the given C<$class>/C<$tag> combination. |
521 |
|
522 |
=back |
523 |
|
524 |
=head2 BER TYPES |
525 |
|
526 |
This lists the predefined BER types - you can map any C<CLASS>/C<TAG> |
527 |
combination to any C<BER_TYPE_*>. |
528 |
|
529 |
=over |
530 |
|
531 |
=item C<BER_TYPE_BYTES> |
532 |
|
533 |
The raw octets of the value. This is the default type for unknown tags and |
534 |
de-/encodes the value as if it were an octet string, i.e. by copying the |
535 |
raw bytes. |
536 |
|
537 |
=item C<BER_TYPE_UTF8> |
538 |
|
539 |
Like C<BER_TYPE_BYTES>, but decodes the value as if it were a UTF-8 string |
540 |
(without validation!) and encodes a perl unicode string into a UTF-8 BER |
541 |
string. |
542 |
|
543 |
=item C<BER_TYPE_UCS2> |
544 |
|
545 |
Similar to C<BER_TYPE_UTF8>, but treats the BER value as UCS-2 encoded |
546 |
string. |
547 |
|
548 |
=item C<BER_TYPE_UCS4> |
549 |
|
550 |
Similar to C<BER_TYPE_UTF8>, but treats the BER value as UCS-4 encoded |
551 |
string. |
552 |
|
553 |
=item C<BER_TYPE_INT> |
554 |
|
555 |
Encodes and decodes a BER integer value to a perl integer scalar. This |
556 |
should correctly handle 64 bit signed and unsigned values. |
557 |
|
558 |
=item C<BER_TYPE_OID> |
559 |
|
560 |
Encodes and decodes an OBJECT IDENTIFIER into dotted form without leading |
561 |
dot, e.g. C<1.3.6.1.213>. |
562 |
|
563 |
=item C<BER_TYPE_RELOID> |
564 |
|
565 |
Same as C<BER_TYPE_OID> but uses relative object identifier |
566 |
encoding: ASN.1 has this hack of encoding the first two OID components |
567 |
into a single integer in a weird attempt to save an insignificant amount |
568 |
of space in an otherwise wasteful encoding, and relative OIDs are |
569 |
basically OIDs without this hack. The practical difference is that the |
570 |
second component of an OID can only have the values 1..40, while relative |
571 |
OIDs do not have this restriction. |
572 |
|
573 |
=item C<BER_TYPE_NULL> |
574 |
|
575 |
Decodes an C<ASN_NULL> value into C<undef>, and always encodes a |
576 |
C<ASN_NULL> type, regardless of the perl value. |
577 |
|
578 |
=item C<BER_TYPE_BOOL> |
579 |
|
580 |
Decodes an C<ASN_BOOLEAN> value into C<0> or C<1>, and encodes a perl |
581 |
boolean value into an C<ASN_BOOLEAN>. |
582 |
|
583 |
=item C<BER_TYPE_REAL> |
584 |
|
585 |
Decodes/encodes a BER real value. NOT IMPLEMENTED. |
586 |
|
587 |
=item C<BER_TYPE_IPADDRESS> |
588 |
|
589 |
Decodes/encodes a four byte string into an IPv4 dotted-quad address string |
590 |
in Perl. Given the obsolete nature of this type, this is a low-effort |
591 |
implementation that simply uses C<sprintf> and C<sscanf>-style conversion, |
592 |
so it won't handle all string forms supported by C<inet_aton> for example. |
593 |
|
594 |
=item C<BER_TYPE_CROAK> |
595 |
|
596 |
Always croaks when encountered during encoding or decoding - the |
597 |
default behaviour when encountering an unknown type is to treat it as |
598 |
C<BER_TYPE_BYTES>. When you don't want that but instead prefer a hard |
599 |
error for some types, then C<BER_TYPE_CROAK> is for you. |
600 |
|
601 |
=back |
602 |
|
603 |
=head2 Example Profile |
604 |
|
605 |
The following creates a profile suitable for SNMP - it's exactly identical |
606 |
to the C<$Convert::BER::XS::SNMP_PROFILE> profile. |
607 |
|
608 |
our $SNMP_PROFILE = new Convert::BER::XS::Profile; |
609 |
|
610 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_IPADDRESS , BER_TYPE_IPADDRESS); |
611 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER32 , BER_TYPE_INT); |
612 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_UNSIGNED32, BER_TYPE_INT); |
613 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_TIMETICKS , BER_TYPE_INT); |
614 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_OPAQUE , BER_TYPE_IPADDRESS); |
615 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER64 , BER_TYPE_INT); |
616 |
|
617 |
=cut |
618 |
|
619 |
our $DEFAULT_PROFILE = new Convert::BER::XS::Profile; |
620 |
|
621 |
$DEFAULT_PROFILE->_set_default; |
622 |
|
623 |
# additional SNMP application types |
624 |
our $SNMP_PROFILE = new Convert::BER::XS::Profile; |
625 |
|
626 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_IPADDRESS , BER_TYPE_IPADDRESS); |
627 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER32 , BER_TYPE_INT); |
628 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_UNSIGNED32, BER_TYPE_INT); |
629 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_TIMETICKS , BER_TYPE_INT); |
630 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_OPAQUE , BER_TYPE_IPADDRESS); |
631 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER64 , BER_TYPE_INT); |
632 |
|
633 |
1; |
634 |
|
635 |
=head2 LIMITATIONS/NOTES |
636 |
|
637 |
This module can only en-/decode 64 bit signed and unsigned integers, and |
638 |
only when your perl supports those. |
639 |
|
640 |
This module does not generally care about ranges, i.e. it will happily |
641 |
de-/encode 64 bit integers into an C<ASN_INTEGER> value, or a negative |
642 |
number into an C<SNMP_COUNTER64>. |
643 |
|
644 |
OBJECT IDENTIFIEERs cannot have unlimited length, although the limit is |
645 |
much larger than e.g. the one imposed by SNMP or other protocols,a nd is |
646 |
about 4kB. |
647 |
|
648 |
Indefinite length encoding is not supported. |
649 |
|
650 |
Constructed strings are decoded just fine, but there should be a way to |
651 |
join them for convenience. |
652 |
|
653 |
REAL values are not supported and will currently croak. |
654 |
|
655 |
The encoder and decoder tend to accept more formats than should be |
656 |
strictly supported. |
657 |
|
658 |
This module has undergone little to no testing so far. |
659 |
|
660 |
=head2 ITHREADS SUPPORT |
661 |
|
662 |
This module is unlikely to work when the (officially discouraged) ithreads |
663 |
are in use. |
664 |
|
665 |
=head1 AUTHOR |
666 |
|
667 |
Marc Lehmann <schmorp@schmorp.de> |
668 |
http://software.schmorp.de/pkg/Convert-BER-XS |
669 |
|
670 |
=cut |
671 |
|