… | |
… | |
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 | |
11 | |
12 | # the above results in a data structure consisting of (class, tag, |
12 | # The above results in a data structure consisting of (class, tag, |
13 | # constructed, data) tuples. here is such a message, SNMPv1 trap |
13 | # constructed, data) tuples. Below is such a message, SNMPv1 trap |
14 | # with a cisoc mac change notification |
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? |
15 | |
17 | |
16 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, |
18 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, |
17 | [ |
19 | [ |
18 | [ ASN_UNIVERSAL, ASN_INTEGER32, 0, 0 ], # snmp version 1 |
20 | [ ASN_UNIVERSAL, ASN_INTEGER32, 0, 0 ], # snmp version 1 |
19 | [ ASN_UNIVERSAL, 4, 0, "public" ], # community |
21 | [ ASN_UNIVERSAL, 4, 0, "public" ], # community |
20 | [ ASN_CONTEXT, 4, 1, # CHOICE, constructed |
22 | [ ASN_CONTEXT, 4, 1, # CHOICE, constructed - trap PDU |
21 | [ |
23 | [ |
22 | [ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.2" ], # enterprise oid |
24 | [ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.2" ], # enterprise oid |
23 | [ ASN_APPLICATION, 0, 0, "\x0a\x00\x00\x01" ], # SNMP IpAddress, 10.0.0.1 |
25 | [ ASN_APPLICATION, 0, 0, "\x0a\x00\x00\x01" ], # SNMP IpAddress, 10.0.0.1 |
24 | [ ASN_UNIVERSAL, ASN_INTEGER32, 0, 6 ], # generic trap |
26 | [ ASN_UNIVERSAL, ASN_INTEGER32, 0, 6 ], # generic trap |
25 | [ ASN_UNIVERSAL, ASN_INTEGER32, 0, 1 ], # specific trap |
27 | [ ASN_UNIVERSAL, ASN_INTEGER32, 0, 1 ], # specific trap |
26 | [ ASN_APPLICATION, ASN_TIMETICKS, 0, 1817903850 ], # SNMP TimeTicks |
28 | [ ASN_APPLICATION, ASN_TIMETICKS, 0, 1817903850 ], # SNMP TimeTicks |
27 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # the varbindlist |
29 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # the varbindlist |
28 | [ |
30 | [ |
29 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # a single varbind, "key value" pair |
31 | [ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # a single varbind, "key value" pair |
30 | [ |
32 | [ |
31 | [ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.1.1.8.1.2.1" ], # the oid |
33 | [ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.1.1.8.1.2.1" ], |
32 | [ ASN_UNIVERSAL, ASN_OCTET_STRING, 0, "...data..." # the value |
34 | [ ASN_UNIVERSAL, ASN_OCTET_STRING, 0, "...data..." # the value |
33 | ] |
35 | ] |
34 | ] |
36 | ] |
35 | ], |
37 | ], |
36 | ... |
38 | ... |
… | |
… | |
62 | |
64 | |
63 | my $buf = ber_encode $ber; |
65 | my $buf = ber_encode $ber; |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 DESCRIPTION |
66 | |
68 | |
|
|
69 | WARNING: Before release 1.0, the API is not considered stable in any way. |
|
|
70 | |
67 | This module implements a I<very> low level BER/DER en-/decoder. |
71 | This module implements a I<very> low level BER/DER en-/decoder. |
68 | |
72 | |
69 | If is tuned for low memory and high speed, while still maintaining some |
73 | If is tuned for low memory and high speed, while still maintaining some |
70 | level of user-friendlyness. |
74 | level of user-friendlyness. |
71 | |
75 | |
… | |
… | |
78 | data structures. It supports various mappings to JSON, XML, but most |
82 | data structures. It supports various mappings to JSON, XML, but most |
79 | importantly, to a various binary encodings such as BER, that is the topic |
83 | importantly, to a various binary encodings such as BER, that is the topic |
80 | of this module, and is used in SNMP or LDAP for example. |
84 | of this module, and is used in SNMP or LDAP for example. |
81 | |
85 | |
82 | While ASN.1 defines a schema that is useful to interpret encoded data, |
86 | While ASN.1 defines a schema that is useful to interpret encoded data, |
83 | the BER encoding is actually somehat self-describing: you might not know |
87 | the BER encoding is actually somewhat self-describing: you might not know |
84 | whether something is a string or a number or a sequence or something else, |
88 | whether something is a string or a number or a sequence or something else, |
85 | but you can nevertheless decode the overall structure, even if you end up |
89 | but you can nevertheless decode the overall structure, even if you end up |
86 | with just a binary blob for the actual value. |
90 | with just a binary blob for the actual value. |
87 | |
91 | |
88 | This works because BER values are tagged with a type and a namespace, |
92 | This works because BER values are tagged with a type and a namespace, |
… | |
… | |
104 | This module represents every BER value as a 4-element tuple (actually an |
108 | This module represents every BER value as a 4-element tuple (actually an |
105 | array-reference): |
109 | array-reference): |
106 | |
110 | |
107 | [CLASS, TAG, CONSTRUCTED, DATA] |
111 | [CLASS, TAG, CONSTRUCTED, DATA] |
108 | |
112 | |
|
|
113 | To avoid non-descriptive hardcoded array index numbers, this module |
|
|
114 | defines symbolic constants to access these members: C<BER_CLASS>, |
|
|
115 | C<BER_TAG>, C<BER_CONSTRUCTED> and C<BER_DATA>. |
|
|
116 | |
|
|
117 | Also, the first three members are integers with a little caveat: for |
|
|
118 | performance reasons, these are readonly and shared, so you must not modify |
|
|
119 | them (increment, assign to them etc.) in any way. You may modify the |
|
|
120 | I<DATA> member, and you may re-assign the array itself, e.g.: |
|
|
121 | |
|
|
122 | $ber = ber_decode $binbuf; |
|
|
123 | |
|
|
124 | # the following is NOT legal: |
|
|
125 | $ber->[BER_CLASS] = ASN_PRIVATE; # ERROR, CLASS/TAG/CONSTRUCTED are READ ONLY(!) |
|
|
126 | |
|
|
127 | # but all of the following are fine: |
|
|
128 | $ber->[BER_DATA] = "string"; |
|
|
129 | $ber->[BER_DATA] = [ASN_UNIVERSAL, ASN_INTEGER32, 0, 123]; |
|
|
130 | @$ber = (ASN_APPLICATION, SNMP_TIMETICKS, 0, 1000); |
|
|
131 | |
109 | I<CLASS> is something like a namespace for I<TAG>s - there is the |
132 | I<CLASS> is something like a namespace for I<TAG>s - there is the |
110 | C<ASN_UNIVERSAL> namespace which defines tags common to all ASN.1 |
133 | C<ASN_UNIVERSAL> namespace which defines tags common to all ASN.1 |
111 | implementations, the C<ASN_APPLICATION> namespace which defines tags for |
134 | implementations, the C<ASN_APPLICATION> namespace which defines tags for |
112 | specific applications (for example, the SNMP C<Unsigned32> type is in this |
135 | specific applications (for example, the SNMP C<Unsigned32> type is in this |
113 | namespace), a special-purpose context namespace (C<ASN_CONTEXT>, used e.g. |
136 | namespace), a special-purpose context namespace (C<ASN_CONTEXT>, used e.g. |
… | |
… | |
143 | Thus, you can always decode a BER data structure and at worst you get a |
166 | Thus, you can always decode a BER data structure and at worst you get a |
144 | string in place of some nice decoded value. |
167 | string in place of some nice decoded value. |
145 | |
168 | |
146 | See the SYNOPSIS for an example of such an encoded tuple representation. |
169 | See the SYNOPSIS for an example of such an encoded tuple representation. |
147 | |
170 | |
|
|
171 | =head2 DECODING AND ENCODING |
|
|
172 | |
|
|
173 | =over |
|
|
174 | |
|
|
175 | =item $tuple = ber_decoded $bindata |
|
|
176 | |
|
|
177 | Decodes binary BER data in C<$bindata> and returns the resulting BER |
|
|
178 | tuple. Croaks on any decoding error, so the returned C<$tuple> is always |
|
|
179 | valid. |
|
|
180 | |
|
|
181 | =item $bindata = ber_encode $tuple |
|
|
182 | |
|
|
183 | Encodes the BER tuple into a BER/DER data structure. |
|
|
184 | |
|
|
185 | =back |
|
|
186 | |
|
|
187 | =head2 HELPER FUNCTIONS |
|
|
188 | |
|
|
189 | Working with a 4-tuple for every value can be annoying. Or, rather, I<is> |
|
|
190 | annoying. To reduce this a bit, this module defines a number of helper |
|
|
191 | functions, both to match BER tuples and to conmstruct BER tuples: |
|
|
192 | |
|
|
193 | =head3 MATCH HELPERS |
|
|
194 | |
|
|
195 | Thse functions accept a BER tuple as first argument and either paertially |
|
|
196 | or fully match it. They often come in two forms, one which exactly matches |
|
|
197 | a value, and one which only matches the type and returns the value. |
|
|
198 | |
|
|
199 | They do check whether valid tuples are passed in and croak otherwise. As |
|
|
200 | a ease-of-use exception, they usually also accept C<undef> instead of a |
|
|
201 | tuple reference. in which case they silently fail to match. |
|
|
202 | |
|
|
203 | =over |
|
|
204 | |
|
|
205 | =item $bool = ber_is $tuple, $class, $tag, $constructed, $data |
|
|
206 | |
|
|
207 | This takes a BER C<$tuple> and matches its elements agains the privded |
|
|
208 | values, all of which are optional - values that are either missing or |
|
|
209 | C<undef> will be ignored, the others will be matched exactly (e.g. as if |
|
|
210 | you used C<==> or C<eq> (for C<$data>)). |
|
|
211 | |
|
|
212 | Some examples: |
|
|
213 | |
|
|
214 | ber_is $tuple, ASN_UNIVERSAL, ASN_SEQUENCE, 1 |
|
|
215 | orf die "tuple is not an ASN SEQUENCE"; |
|
|
216 | |
|
|
217 | ber_is $tuple, ASN_UNIVERSAL, ASN_NULL |
|
|
218 | or die "tuple is not an ASN NULL value"; |
|
|
219 | |
|
|
220 | ber_is $tuple, ASN_UNIVERSAL, ASN_INTEGER32, 0, 50 |
|
|
221 | or die "BER integer must be 50"; |
|
|
222 | |
|
|
223 | =item $seq = ber_is_seq $tuple |
|
|
224 | |
|
|
225 | Returns the sequence members (the array of subvalues) if the C<$tuple> is |
|
|
226 | an ASN SEQUENCE, i.e. the C<BER_DATA> member. If the C<$tuple> is not a |
|
|
227 | sequence it returns C<undef>. For example, SNMP version 1/2c/3 packets all |
|
|
228 | consist of an outer SEQUENCE value: |
|
|
229 | |
|
|
230 | my $ber = ber_decode $snmp_data; |
|
|
231 | |
|
|
232 | my $snmp = ber_is_seq $ber |
|
|
233 | or die "SNMP packet invalid: does not start with SEQUENCE"; |
|
|
234 | |
|
|
235 | # now we know $snmp is a sequence, so decode the SNMP version |
|
|
236 | |
|
|
237 | my $version = ber_is_i32 $snmp->[0] |
|
|
238 | or die "SNMP packet invalid: does not start with version number"; |
|
|
239 | |
|
|
240 | =item $bool = ber_is_i32 $tuple, $i32 |
|
|
241 | |
|
|
242 | Returns a true value if the C<$tuple> represents an ASN INTEGER32 with |
|
|
243 | the value C<$i32>. |
|
|
244 | |
|
|
245 | =item $i32 = ber_is_i32 $tuple |
|
|
246 | |
|
|
247 | Returns true (and extracts the integer value) if the C<$tuple> is an ASN |
|
|
248 | INTEGER32. For C<0>, this function returns a special value that is 0 but |
|
|
249 | true. |
|
|
250 | |
|
|
251 | =item $bool = ber_is_oid $tuple, $oid_string |
|
|
252 | |
|
|
253 | Returns true if the C<$tuple> represents an ASN_OBJECT_IDENTIFIER |
|
|
254 | that exactly matches C<$oid_string>. Example: |
|
|
255 | |
|
|
256 | ber_is_oid $tuple, "1.3.6.1.4" |
|
|
257 | or die "oid must be 1.3.6.1.4"; |
|
|
258 | |
|
|
259 | =item $oid = ber_is_oid $tuple |
|
|
260 | |
|
|
261 | Returns true (and extracts the OID string) if the C<$tuple> is an ASN |
|
|
262 | OBJECT IDENTIFIER. Otherwise, it returns C<undef>. |
|
|
263 | |
|
|
264 | =back |
|
|
265 | |
|
|
266 | =head3 CONSTRUCTION HELPERS |
|
|
267 | |
|
|
268 | =over |
|
|
269 | |
|
|
270 | =item $tuple = ber_i32 $value |
|
|
271 | |
|
|
272 | Constructs a new C<ASN_INTEGER32> tuple. |
|
|
273 | |
|
|
274 | =back |
|
|
275 | |
148 | =head2 RELATIONSHIP TO L<Convert::BER> and L<Convert::ASN1> |
276 | =head2 RELATIONSHIP TO L<Convert::BER> and L<Convert::ASN1> |
149 | |
277 | |
150 | This module is I<not> the XS version of L<Convert::BER>, but a different |
278 | This module is I<not> the XS version of L<Convert::BER>, but a different |
151 | take at doing the same thing. I imagine this module would be a good base |
279 | take at doing the same thing. I imagine this module would be a good base |
152 | for speeding up either of these, or write a similar module, or write your |
280 | for speeding up either of these, or write a similar module, or write your |
… | |
… | |
159 | use common::sense; |
287 | use common::sense; |
160 | |
288 | |
161 | use XSLoader (); |
289 | use XSLoader (); |
162 | use Exporter qw(import); |
290 | use Exporter qw(import); |
163 | |
291 | |
164 | our $VERSION = '0.0'; |
292 | our $VERSION = 0.2; |
165 | |
293 | |
166 | XSLoader::load __PACKAGE__, $VERSION; |
294 | XSLoader::load __PACKAGE__, $VERSION; |
167 | |
295 | |
168 | our %EXPORT_TAGS = ( |
296 | our %EXPORT_TAGS = ( |
169 | const => [qw( |
297 | const => [qw( |