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1 .\"
2 .\" Copyright (c) 2004-2005
3 .\" Hartmut Brandt.
4 .\" All rights reserved.
5 .\" Copyright (c) 2001-2003
6 .\" Fraunhofer Institute for Open Communication Systems (FhG Fokus).
7 .\" All rights reserved.
8 .\"
9 .\" Author: Harti Brandt <harti@FreeBSD.org>
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32 .\" $Begemot: bsnmp/lib/asn1.3,v 1.9 2005/10/04 08:46:49 brandt_h Exp $
33 .\"
34 .Dd October 4, 2005
35 .Dt ASN1 3
36 .Os
37 .Sh NAME
38 .Nm asn_get_header ,
39 .Nm asn_put_header ,
40 .Nm asn_put_temp_header ,
41 .Nm asn_commit_header ,
42 .Nm asn_get_integer_raw ,
43 .Nm asn_get_integer ,
44 .Nm asn_put_integer ,
45 .Nm asn_get_octetstring_raw ,
46 .Nm asn_get_octetstring ,
47 .Nm asn_put_octetstring ,
48 .Nm asn_get_null_raw ,
49 .Nm asn_get_null ,
50 .Nm asn_put_null ,
51 .Nm asn_put_exception ,
52 .Nm asn_get_objid_raw ,
53 .Nm asn_get_objid ,
54 .Nm asn_put_objid ,
55 .Nm asn_get_sequence ,
56 .Nm asn_get_ipaddress_raw ,
57 .Nm asn_get_ipaddress ,
58 .Nm asn_put_ipaddress ,
59 .Nm asn_get_uint32_raw ,
60 .Nm asn_put_uint32 ,
61 .Nm asn_get_counter64_raw ,
62 .Nm asn_put_counter64 ,
63 .Nm asn_get_timeticks ,
64 .Nm asn_put_timeticks ,
65 .Nm asn_skip ,
66 .Nm asn_slice_oid ,
67 .Nm asn_append_oid ,
68 .Nm asn_compare_oid ,
69 .Nm asn_is_suboid ,
70 .Nm asn_oid2str_r ,
71 .Nm asn_oid2str
72 .Nd "ASN.1 library for SNMP"
73 .Sh LIBRARY
74 Begemot SNMP library
75 .Pq libbsnmp, -lbsnmp
76 .Sh SYNOPSIS
77 .In bsnmp/asn1.h
78 .Ft enum asn_err
79 .Fn asn_get_header "struct asn_buf *buf" "u_char *type" "asn_len_t *lenp"
80 .Ft enum asn_err
81 .Fn asn_put_header "struct asn_buf *buf" "u_char type" "asn_len_t len"
82 .Ft enum asn_err
83 .Fn asn_put_temp_header "struct asn_buf *buf" "u_char type" "u_char **ptr"
84 .Ft enum asn_err
85 .Fn asn_commit_header "struct asn_buf *buf" "u_char *ptr"
86 .Ft enum asn_err
87 .Fn asn_get_integer_raw "struct asn_buf *buf" "asn_len_t len" "int32_t *res"
88 .Ft enum asn_err
89 .Fn asn_get_integer "struct asn_buf *buf" "int32_t *res"
90 .Ft enum asn_err
91 .Fn asn_put_integer "struct asn_buf *buf" "int32_t arg"
92 .Ft enum asn_err
93 .Fn asn_get_octetstring_raw "struct asn_buf *buf" "asn_len_t len" "u_char *out" "u_int *outsize"
94 .Ft enum asn_err
95 .Fn asn_get_octetstring "struct asn_buf *buf" "u_char *out" "u_int *outsize"
96 .Ft enum asn_err
97 .Fn asn_put_octetstring "struct asn_buf *buf" "const u_char *str" "u_int strsize"
98 .Ft enum asn_err
99 .Fn asn_get_null_raw "struct asn_buf *buf" "asn_len_t len"
100 .Ft enum asn_err
101 .Fn asn_get_null "struct asn_buf *buf"
102 .Ft enum asn_err
103 .Fn asn_put_null "struct asn_buf *buf"
104 .Ft enum asn_err
105 .Fn asn_put_exception "struct asn_buf *buf" "u_int type"
106 .Ft enum asn_err
107 .Fn asn_get_objid_raw "struct asn_buf *buf" "asn_len_t len" "struct asn_oid *oid"
108 .Ft enum asn_err
109 .Fn asn_get_objid "struct asn_buf *buf" "struct asn_oid *oid"
110 .Ft enum asn_err
111 .Fn asn_put_objid "struct asn_buf *buf" "const struct asn_oid *oid"
112 .Ft enum asn_err
113 .Fn asn_get_sequence "struct asn_buf *buf" "asn_len_t *lenp"
114 .Ft enum asn_err
115 .Fn asn_get_ipaddress_raw "struct asn_buf *buf" "asn_len_t len" "u_char *ipa"
116 .Ft enum asn_err
117 .Fn asn_get_ipaddress "struct asn_buf *buf" "u_char *ipa"
118 .Ft enum asn_err
119 .Fn asn_put_ipaddress "struct asn_buf *buf" "const u_char *ipa"
120 .Ft enum asn_err
121 .Fn asn_get_uint32_raw "struct asn_buf *buf" "asn_len_t len" "u_int32_t *res"
122 .Ft enum asn_err
123 .Fn asn_put_uint32 "struct asn_buf *buf" "u_char type" "u_int32_t val"
124 .Ft enum asn_err
125 .Fn asn_get_counter64_raw "struct asn_buf *buf" "asn_len_t len" "u_int64_t *res"
126 .Ft enum asn_err
127 .Fn asn_put_counter64 "struct asn_buf *buf" "u_int64_t val"
128 .Ft enum asn_err
129 .Fn asn_get_timeticks "struct asn_buf *buf" "u_int32_t *valp"
130 .Ft enum asn_err
131 .Fn asn_put_timeticks "struct asn_buf *buf" "u_int32_t val"
132 .Ft enum asn_err
133 .Fn asn_skip "struct asn_buf *buf" "asn_len_t len"
134 .Ft void
135 .Fn asn_slice_oid "struct asn_oid *dest" "const struct asn_oid *src" "u_int from" "u_int to"
136 .Ft void
137 .Fn asn_append_oid "struct asn_oid *to" "const struct asn_oid *from"
138 .Ft int
139 .Fn asn_compare_oid "const struct asn_oid *oid1" "const struct asn_oid *oid2"
140 .Ft int
141 .Fn asn_is_suboid "const struct asn_oid *oid1" "const struct asn_oid *oid2"
142 .Ft char *
143 .Fn asn_oid2str_r "const struct asn_oid *oid" "char *buf"
144 .Ft char *
145 .Fn asn_oid2str "const struct asn_oid *oid"
146 .Sh DESCRIPTION
147 The ASN.1 library contains routines to handle ASN.1 encoding for SNMP.
148 It supports only the restricted form of ASN.1 as required by SNMP.
149 There are two basic structures used throughout the library:
150 .Bd -literal -offset indent
151 /* these restrictions are in the SMI */
152 #define ASN_MAXID 0xffffffff
153 #define ASN_MAXOIDLEN 128
155 /* type of subidentifiers */
156 typedef u_int32_t asn_subid_t;
158 struct asn_oid {
159 u_int len;
160 asn_subid_t subs[ASN_MAXOIDLEN];
161 };
162 .Ed
163 .Pp
164 This structure represents an OID with the restrictions defined in the SNMP
165 SMI.
166 .Fa len
167 holds the current length of the OID and
168 .Fa subs
169 holds the elements of the OID.
170 .Bd -literal -offset indent
171 struct asn_buf {
172 union {
173 u_char *ptr;
174 const u_char *cptr;
175 } asn_u;
176 size_t asn_len;
177 };
178 #define asn_cptr asn_u.cptr
179 #define asn_ptr asn_u.ptr
180 .Ed
181 .Pp
182 This structure is used to encode and decode ASN.1.
183 It describes the output
184 buffer for encoding routines and the input buffer for decoding routines.
185 For encoding
186 .Fa asn_len
187 holds the number of remaining free octets in the buffer.
188 The first free byte is pointed to by
189 .Fa asn_ptr .
190 For decoding
191 .Fa asn_len
192 holds the number of remaining bytes to decode.
193 The next byte to decode is pointed to by
194 .Fa asn_cptr .
195 .Pp
196 Most of the functions return an error code
197 .Fa "enum asn_error" :
198 .Bd -literal -offset indent
199 enum asn_err {
200 /* conversion was ok */
201 ASN_ERR_OK = 0,
202 /* conversion failed and stopped */
203 ASN_ERR_FAILED = 1 | 0x1000,
204 /* length field bad, value skipped */
205 ASN_ERR_BADLEN = 2,
206 /* out of buffer, stopped */
207 ASN_ERR_EOBUF = 3 | 0x1000,
208 /* length ok, but value is out of range */
209 ASN_ERR_RANGE = 4,
210 /* not the expected tag, stopped */
211 ASN_ERR_TAG = 5 | 0x1000,
212 };
213 #define ASN_ERR_STOPPED(E) (((E) & 0x1000) != 0)
214 .Ed
215 .Pp
216 If
217 .Fn ASN_ERR_STOPPED
218 returns true, the error was fatal and processing has stopped at the point
219 of error.
220 .Pp
221 The function
222 .Fn asn_get_header
223 reads the next header from the input octet stream.
224 It returns the tag in the variable pointed to by
225 .Fa type
226 (note that only single byte tags are supported) and the decoded length field
227 in the value pointed to by
228 .Fa lenp
229 (this is restricted to a unsigned 32-bit value).
230 All errors in this function are fatal and stop processing.
231 .Pp
232 The function
233 .Fn asn_put_header
234 writes an ASN.1 header.
235 .Fa type
236 is the tag to write and is restricted to one byte tags (i.e., tags
237 lesser or equal than 0x30).
238 .Fa len
239 is the length of the value and is restricted to 16-bit.
240 .Pp
241 The functions
242 .Fn asn_put_temp_header
243 and
244 .Fn asn_commit_header
245 are used to write a header when the length of the value is not known in
246 advance, for example, for sequences.
247 .Fn asn_put_temp_header
248 writes a header with the given tag
249 .Fa type
250 and space for the maximum supported length field and sets the pointer pointed
251 to by
252 .Fa ptr
253 to the begin of this length field.
254 This pointer must then be fed into
255 .Fn asn_commit_header
256 directly after writing the value to the buffer.
257 The function will compute the
258 length, insert it into the right place and shift the value if the resulting
259 length field is shorter than the estimated one.
260 .Pp
261 The function
262 .Fn asn_get_integer_raw
263 is used to decode a signed integer value (32-bit).
264 It assumes, that the
265 header of the integer has been decoded already.
266 .Fa len
267 is the length obtained from the ASN.1 header and the integer will be returned
268 in the value pointed to by
269 .Fa res .
270 .Pp
271 The function
272 .Fn asn_get_integer
273 decodes a complete 32-bit signed integer including the header.
274 If the tag is wrong
275 .Li ASN_ERR_TAG
276 is returned.
277 The function
278 .Fn asn_put_integer
279 encodes a 32-bit signed integer.
280 .Pp
281 The function
282 .Fn asn_get_octetstring_raw
283 decodes the value field of an ASN.1 octet string.
284 The length obtained from the header must be fed into the
285 .Fa len
286 argument and
287 .Fa out
288 must point to a buffer to receive the octet string.
289 On entry to the function
290 .Fa outsize
291 must point to the size of the buffer.
292 On exit
293 .Fa outsize
294 will point to the number of octets decoded (if no error occurs this will be
295 equal to
296 .Fa len ).
297 The function
298 .Fn asn_get_octetstring
299 decodes an octetstring including the header.
300 .Fa out
301 must point to a buffer to receive the string,
302 .Fa outsize
303 must point to the size of the buffer.
304 On exit of the function
305 .Fa outsize
306 will point to the number of octets decoded.
307 The function
308 .Fn asn_put_octetstring
309 encodes an octetstring (including the header).
310 .Fa str
311 points to the string to encode and
312 .Fa strsize
313 is the length of the string (the string may contain embedded
314 .Li NUL Ns s).
315 .Pp
316 The function
317 .Fn asn_get_null_raw
318 decodes a null value.
319 .Fa len
320 is the length obtained from the header and must be 0.
321 The function
322 .Fn asn_get_null
323 decodes a null including the header and the function
324 .Fn asn_put_null
325 encodes a null.
326 .Pp
327 The function
328 .Fn asn_put_exception
329 is used to encode an SNMPv2 exception.
330 The exception type is
331 .Fa type .
332 .Pp
333 The function
334 .Fn asn_get_objid_raw
335 is used to decode an OID value.
336 .Fa len
337 must be the value length obtained from the header and
338 .Fa oid
339 will receive the decoded OID.
340 The function
341 .Fn asn_get_objid
342 decodes a complete OID (including the header) and the function
343 .Fn asn_put_objid
344 encodes a complete OID.
345 .Pp
346 The function
347 .Fn asn_get_sequence
348 decodes a sequence header.
349 The length of the sequence value will be stored in the value pointed to by
350 .Fa lenp .
351 .Pp
352 The function
353 .Fn asn_get_ipaddress_raw
354 decodes an IP address value.
355 .Fa len
356 is the length from the header and must be 4.
357 .Fa ipa
358 will receive the decoded IP address and must point to a buffer of at least
359 four bytes.
360 The function
361 .Fn asn_get_ipaddress
362 decodes a complete IP address (including the header) and
363 .Fn asn_put_ipaddress
364 encodes an IP address.
365 .Pp
366 The function
367 .Fn asn_get_uint32_raw
368 decodes an unsigned 32-bit integer value.
369 .Fa len
370 is the length from the header and
371 .Fa res
372 will get the decoded value.
373 The function
374 .Fn asn_put_uint32
375 encodes an unsigned 32-bit integer value and inserts the tag given in
376 .Fa type
377 into the header.
378 .Pp
379 The function
380 .Fn asn_get_counter64_raw
381 decodes an unsigned 64-bit integer value.
382 .Fa len
383 must be the value length from the header.
384 The resulting value is stored into the variable pointed to by
385 .Fa res .
386 The function
387 .Fn asn_put_counter64
388 encodes a complete unsigned 64-bit value.
389 .Pp
390 The function
391 .Fn asn_get_timeticks
392 decodes an ASN.1 object of type
393 .Li TIMETICKS
394 and the function
395 .Fn asn_put_timeticks
396 encodes such an object.
397 .Pp
398 The function
399 .Fn asn_skip
400 can be used to skip
401 .Fa len
402 bytes in the input buffer.
403 .Pp
404 The function
405 .Fn asn_slice_oid
406 splits a part out from an OID.
407 It takes all the subids from the OID pointed to by
408 .Fa src
409 starting with the subid at position
410 .Fa from
411 (the first subid being subid 0) up to, but not including, subid
412 .Fa to
413 and generates a new OID in
414 .Fa dest .
415 If
416 .Fa to
417 is less or equal to
418 .Fa from
419 the resulting OID will have a length of zero.
420 .Pp
421 The function
422 .Fn asn_append_oid
423 appends the OID
424 .Fa from
425 to the OID
426 .Fa to
427 given that the resulting OID is not too long.
428 If the maximum length is exceeded the result is undefined.
429 .Pp
430 The function
431 .Fn asn_compare_oid
432 compares two oids and returns the values
433 .Li -1 ,
434 .Li 0 or
435 .Li +1
436 when
437 .Fa oid1
438 is lesser than, equal, or larger than
439 .Fa oid2
440 resp.
441 .Pp
442 The function
443 .Fn asn_is_suboid
444 returns 1 if
445 .Fa oid1
446 is equal to the leading part of
447 .Fa oid2 .
448 It returns 0 otherwise.
449 .Pp
450 The function
451 .Fn asn_oid2str_r
452 makes a printable string from
453 .Fa oid .
454 The buffer pointed to by
455 .Fa str
456 must be large enough to hold the result.
457 The constant
458 .Li ASN_OIDSTRLEN
459 is defined to be the length of the maximum string generated by this function
460 (including the trailing NUL).
461 The function
462 .Fn asn_oid2str
463 makes a printable string from
464 .Fa oid
465 into a private buffer that is overwritten by each call.
466 .Sh DIAGNOSTICS
467 When an error occurs in any of the function the function pointed to
468 by the global pointer
469 .Bd -literal -offset indent
470 extern void (*asn_error)(const struct asn_buf *, const char *, ...);
471 .Ed
472 .Pp
473 is called with the current buffer (this may be
474 .Li NULL )
475 and a
476 .Xr printf 3
477 style format string.
478 There is a default error handler in the library that prints a message
479 starting with
480 .Sq ASN.1:
481 followed by the error message and an optional dump of the buffer.
482 .Sh SEE ALSO
483 .Xr gensnmptree 1 ,
484 .Xr bsnmpd 1 ,
485 .Xr bsnmpagent 3 ,
486 .Xr bsnmpclient 3 ,
487 .Xr bsnmplib 3
488 .Sh STANDARDS
489 This implementation conforms to the applicable IETF RFCs and ITU-T
490 recommendations.
491 .Sh AUTHORS
492 .An Hartmut Brandt Aq harti@FreeBSD.org