1.\" 2.\" Copyright (c) 2001-2003 3.\" Fraunhofer Institute for Open Communication Systems (FhG Fokus). 4.\" All rights reserved. 5.\" 6.\" Author: Harti Brandt <harti@freebsd.org> 7.\" 8.\" Redistribution of this software and documentation and use in source and 9.\" binary forms, with or without modification, are permitted provided that 10.\" the following conditions are met: 11.\" 12.\" 1. Redistributions of source code or documentation must retain the above 13.\" copyright notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. Neither the name of the Institute nor the names of its contributors 18.\" may be used to endorse or promote products derived from this software 19.\" without specific prior written permission. 20.\" 21.\" THIS SOFTWARE AND DOCUMENTATION IS PROVIDED BY FRAUNHOFER FOKUS 22.\" AND ITS CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, 23.\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 24.\" FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 25.\" FRAUNHOFER FOKUS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 27.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 28.\" OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 29.\" LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 30.\" NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 31.\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32.\" 33.\" $Begemot: bsnmp/lib/asn1.3,v 1.4 2004/04/13 17:01:31 novo Exp $ 34.\" 35.Dd August 15, 2002 36.Dt asn1 3 37.Os 38.Sh NAME 39.Nm asn_get_header , 40.Nm asn_put_header , 41.Nm asn_put_temp_header , 42.Nm asn_commit_header , 43.Nm asn_get_integer_raw , 44.Nm asn_get_integer , 45.Nm asn_put_integer , 46.Nm asn_get_octetstring_raw , 47.Nm asn_get_octetstring , 48.Nm asn_put_octetstring , 49.Nm asn_get_null_raw , 50.Nm asn_get_null , 51.Nm asn_put_null , 52.Nm asn_put_exception , 53.Nm asn_get_objid_raw , 54.Nm asn_get_objid , 55.Nm asn_put_objid , 56.Nm asn_get_sequence , 57.Nm asn_get_ipaddress_raw , 58.Nm asn_get_ipaddress , 59.Nm asn_put_ipaddress , 60.Nm asn_get_uint32_raw , 61.Nm asn_put_uint32 , 62.Nm asn_get_counter64_raw , 63.Nm asn_put_counter64 , 64.Nm asn_get_timeticks , 65.Nm asn_put_timeticks , 66.Nm asn_skip , 67.Nm asn_slice_oid , 68.Nm asn_append_oid , 69.Nm asn_compare_oid , 70.Nm asn_is_suboid , 71.Nm asn_oid2str_r , 72.Nm asn_oid2str 73.Nd "ASN.1 library for SNMP" 74.Sh LIBRARY 75Begemot SNMP library 76.Pq libbsnmp, -lbsnmp 77.Sh SYNOPSIS 78.In bsnmp/asn1.h 79.Ft enum asn_err 80.Fn asn_get_header "struct asn_buf *buf" "u_char *type" "asn_len_t *lenp" 81.Ft enum asn_err 82.Fn asn_put_header "struct asn_buf *buf" "u_char type" "asn_len_t len" 83.Ft enum asn_err 84.Fn asn_put_temp_header "struct asn_buf *buf" "u_char type" "u_char **ptr" 85.Ft enum asn_err 86.Fn asn_commit_header "struct asn_buf *buf" "u_char *ptr" 87.Ft enum asn_err 88.Fn asn_get_integer_raw "struct asn_buf *buf" "asn_len_t len" "int32_t *res" 89.Ft enum asn_err 90.Fn asn_get_integer "struct asn_buf *buf" "int32_t *res" 91.Ft enum asn_err 92.Fn asn_put_integer "struct asn_buf *buf" "int32_t arg" 93.Ft enum asn_err 94.Fn asn_get_octetstring_raw "struct asn_buf *buf" "asn_len_t len" "u_char *out" "u_int *outsize" 95.Ft enum asn_err 96.Fn asn_get_octetstring "struct asn_buf *buf" "u_char *out" "u_int *outsize" 97.Ft enum asn_err 98.Fn asn_put_octetstring "struct asn_buf *buf" "const u_char *str" "u_int strsize" 99.Ft enum asn_err 100.Fn asn_get_null_raw "struct asn_buf *buf" "asn_len_t len" 101.Ft enum asn_err 102.Fn asn_get_null "struct asn_buf *buf" 103.Ft enum asn_err 104.Fn asn_put_null "struct asn_buf *buf" 105.Ft enum asn_err 106.Fn asn_put_exception "struct asn_buf *buf" "u_int type" 107.Ft enum asn_err 108.Fn asn_get_objid_raw "struct asn_buf *buf" "asn_len_t len" "struct asn_oid *oid" 109.Ft enum asn_err 110.Fn asn_get_objid "struct asn_buf *buf" "struct asn_oid *oid" 111.Ft enum asn_err 112.Fn asn_put_objid "struct asn_buf *buf" "const struct asn_oid *oid" 113.Ft enum asn_err 114.Fn asn_get_sequence "struct asn_buf *buf" "asn_len_t *lenp" 115.Ft enum asn_err 116.Fn asn_get_ipaddress_raw "struct asn_buf *buf" "asn_len_t len" "u_char *ipa" 117.Ft enum asn_err 118.Fn asn_get_ipaddress "struct asn_buf *buf" "u_char *ipa" 119.Ft enum asn_err 120.Fn asn_put_ipaddress "struct asn_buf *buf" "const u_char *ipa" 121.Ft enum asn_err 122.Fn asn_get_uint32_raw "struct asn_buf *buf" "asn_len_t len" "u_int32_t *res" 123.Ft enum asn_err 124.Fn asn_put_uint32 "struct asn_buf *buf" "u_char type" "u_int32_t val" 125.Ft enum asn_err 126.Fn asn_get_counter64_raw "struct asn_buf *buf" "asn_len_t len" "u_int64_t *res" 127.Ft enum asn_err 128.Fn asn_put_counter64 "struct asn_buf *buf" "u_int64_t val" 129.Ft enum asn_err 130.Fn asn_get_timeticks "struct asn_buf *buf" "u_int32_t *valp" 131.Ft enum asn_err 132.Fn asn_put_timeticks "struct asn_buf *buf" "u_int32_t val" 133.Ft enum asn_err 134.Fn asn_skip "struct asn_buf *buf" "asn_len_t len" 135.Ft void 136.Fn asn_slice_oid "struct asn_oid *dest" "const struct asn_oid *src" "u_int from" "u_int to" 137.Ft void 138.Fn asn_append_oid "struct asn_oid *to" "const struct asn_oid *from" 139.Ft int 140.Fn asn_compare_oid "const struct asn_oid *oid1" "const struct asn_oid *oid2" 141.Ft int 142.Fn asn_is_suboid "const struct asn_oid *oid1" "const struct asn_oid *oid2" 143.Ft char * 144.Fn asn_oid2str_r "const struct asn_oid *oid" "char *buf" 145.Ft char * 146.Fn asn_oid2str "const struct asn_oid *oid" 147.Sh DESCRIPTION 148The ASN.1 library contains routines to handle ASN.1 encoding for SNMP. 149It supports only the restricted form of ASN.1 as required by SNMP. There 150are two basic structures used throughout the library: 151.Bd -literal -offset indent 152/* these restrictions are in the SMI */ 153#define ASN_MAXID 0xffffffff 154#define ASN_MAXOIDLEN 128 155 156/* type of subidentifiers */ 157typedef u_int32_t asn_subid_t; 158 159struct asn_oid { 160 u_int len; 161 asn_subid_t subs[ASN_MAXOIDLEN]; 162}; 163.Ed 164.Pp 165This structure represents an OID with the restrictions defined in the SNMP 166SMI. 167.Fa len 168holds the current length of the OID and 169.Fa subs 170holds the elements of the OID. 171.Bd -literal -offset indent 172struct asn_buf { 173 union { 174 u_char *ptr; 175 const u_char *cptr; 176 } asn_u; 177 size_t asn_len; 178}; 179#define asn_cptr asn_u.cptr 180#define asn_ptr asn_u.ptr 181.Ed 182.Pp 183This structure is used to encode and decode ASN.1. It describes the output 184buffer for encoding routines and the input buffer for decoding routines. 185For encoding 186.Fa asn_len 187holds the number of remaining free octets in the buffer. The first free byte 188is pointed to by 189.Fa asn_ptr . 190For decoding 191.Fa asn_len 192holds the number of remaining bytes to decode. The next byte to decode is pointed 193to by 194.Fa asn_cptr . 195.Pp 196Most of the functions return an error code 197.Fa "enum asn_error" : 198.Bd -literal -offset indent 199enum 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 216If 217.Fn ASN_ERR_STOPPED 218returns true, the error was fatal and processing has stopped at the point 219of error. 220.Pp 221The function 222.Fn asn_get_header 223reads the next header from the input octet stream. It returns the tag 224in the variable pointed to by 225.Fa type 226(note that only single byte tags are supported) and the decoded length field 227in the value pointed to by 228.Fa lenp 229(this is restricted to a unsigned 32-bit value). All errors in this function 230are fatal and stop processing. 231.Pp 232The function 233.Fn asn_put_header 234writes an ASN.1 header. 235.Fa type 236is the tag to write and is restricted to one byte tags (i.e. tags 237lesser or equal than 0x30). 238.Fa len 239is the length of the value and is restricted to 16-bit. 240.Pp 241The functions 242.Fn asn_put_temp_header 243and 244.Fn asn_commit_header 245are used to write a header when the length of the value is not known in 246advance, for example, for sequences. 247.Fn asn_put_temp_header 248writes a header with the given tag 249.Fa type 250and space for the maximum supported length field and sets the pointer pointed 251to by 252.Fa ptr 253to the begin of this length field. This pointer must then be fed into 254.Fn asn_commit_header 255directly after writing the value to the buffer. The function will compute the 256length, insert it into the right place and shift the value if the resulting 257length field is shorter than the estimated one. 258.Pp 259The function 260.Fn asn_get_integer_raw 261is used to decode a signed integer value (32-bit). It assumes, that the 262header of the integer has been decoded already. 263.Fa len 264is the length obtained from the ASN.1 header and the integer will be returned 265in the value pointed to by 266.Fa res . 267.Pp 268The function 269.Fn asn_get_integer 270decodes a complete 32-bit signed integer including the header. If the 271tag is wrong 272.Li ASN_ERR_TAG 273is returned. 274The function 275.Fn asn_put_integer 276encodes a 32-bit signed integer. 277.Pp 278The function 279.Fn asn_get_octetstring_raw 280decodes the value field of an ASN.1 octet string. The length obtained from the 281header must be fed into the 282.Fa len 283argument and 284.Fa out 285must point to a buffer to receive the octet string. On entry to the function 286.Fa outsize 287must point to the size of the buffer. On exit 288.Fa outsize 289will point to the number of octets decoded (if no error occurs this will be 290equal to 291.Fa len ). 292The function 293.Fn asn_get_octetstring 294decodes an octetstring including the header. 295.Fa out 296must point to a buffer to receive the string, 297.Fa outsize 298must point to the size of the buffer. On exit of the function 299.Fa outsize 300will point to the number of octets decoded. 301The function 302.Fn asn_put_octetstring 303encodes an octetstring (including the header). 304.Fa str 305points to the string to encode and 306.Fa strsize 307is the length of the string (the string may contain embedded 308.Li NUL Ns s). 309.Pp 310The function 311.Fn asn_get_null_raw 312decodes a null value. 313.Fa len 314is the length obtained from the header and must be 0. 315The function 316.Fn asn_get_null 317decodes a null including the header and the function 318.Fn asn_put_null 319encodes a null. 320.Pp 321The function 322.Fn asn_put_exception 323is used to encode an SNMPv2 exception. The exception type is 324.Fa type . 325.Pp 326The function 327.Fn asn_get_objid_raw 328is used to decode an OID value. 329.Fa len 330must be the value length obtained from the header and 331.Fa oid 332will receive the decoded OID. 333The function 334.Fn asn_get_objid 335decodes a complete OID (including the header) and the function 336.Fn asn_put_objid 337encodes a complete OID. 338.Pp 339The function 340.Fn asn_get_sequence 341decodes a sequence header. 342The length of the sequence value will be stored in the value pointed to by 343.Fa lenp . 344.Pp 345The function 346.Fn asn_get_ipaddress_raw 347decodes an IP address value. 348.Fa len 349is the length from the header and must be 4. 350.Fa ipa 351will receive the decoded IP address and must point to a buffer of at least 352four bytes. 353The function 354.Fn asn_get_ipaddress 355decodes a complete IP address (including the header) and 356.Fn asn_put_ipaddress 357encodes an IP address. 358.Pp 359The function 360.Fn asn_get_uint32_raw 361decodes an unsigned 32-bit integer value. 362.Fa len 363is the length from the header and 364.Fa res 365will get the decoded value. 366The function 367.Fn asn_put_uint32 368encodes an unsigned 32-bit integer value and inserts the tag given in 369.Fa type 370into the header. 371.Pp 372The function 373.Fn asn_get_counter64_raw 374decodes an unsigned 64-bit integer value. 375.Fa len 376must be the value length from the header. The resulting value is 377stored into the variable pointed to by 378.Fa res . 379The function 380.Fn asn_put_counter64 381encodes a complete unsigned 64-bit value. 382.Pp 383The function 384.Fn asn_get_timeticks 385decodes an ASN.1 object of type 386.Li TIMETICKS 387and the function 388.Fn asn_put_timeticks 389encodes such an object. 390.Pp 391The function 392.Fn asn_skip 393can be used to skip 394.Fa len 395bytes in the input buffer. 396.Pp 397The function 398.Fn asn_slice_oid 399splits a part out from an OID. It takes all the subids from the OID 400pointed to by 401.Fa src 402starting with the subid at position 403.Fa from 404(the first subid beeing subid 0) up to, but not including, subid 405.Fa to 406and generates a new OID in 407.Fa dest . 408If 409.Fa to 410is less or equal to 411.Fa from 412the resulting OID will have a length of zero. 413.Pp 414The function 415.Fn asn_append_oid 416appends the OID 417.Fa from 418to the OID 419.Fa to 420given that the resulting OID is not too long. If the maximum length is exceeded 421the result is undefined. 422.Pp 423The function 424.Fn asn_compare_oid 425compares two oids and returns the values 426.Li -1 , 427.Li 0 or 428.Li +1 429when 430.Fa oid1 431is lesser than, equal, or larger than 432.Fa oid2 433resp. 434.Pp 435The function 436.Fn asn_is_suboid 437returns 1 if 438.Fa oid1 439is equal to the leading part of 440.Fa oid2 . 441It returns 0 otherwise. 442.Pp 443The function 444.Fn asn_oid2str_r 445makes a printable string from 446.Fa oid . 447The buffer pointed to by 448.Fa str 449must be large enough to hold the result. The constant 450.Li ASN_OIDSTRLEN 451is defined to be the length of the maximum string generated by this function 452(including the trailing NUL). 453The function 454.Fn asn_oid2str 455makes a printable string from 456.Fa oid 457into a private buffer that is overwritten by each call. 458.Sh DIAGNOSTICS 459When an error occures in any of the function the function pointed to 460by the global pointer 461.Bd -literal -offset indent 462extern void (*asn_error)(const struct asn_buf *, const char *, ...); 463.Ed 464.Pp 465is called with the current buffer (this may be 466.Li NULL ) 467and a 468.Xr printf 3 469style format string. 470There is a default error handler in the library that prints a message 471starting with 472.Sq ASN.1: 473followed by the error message and an optional dump of the buffer. 474.Sh SEE ALSO 475.Xr snmpd 1 , 476.Xr gensnmptree 1 , 477.Xr bsnmplib 3 478.Xr bsnmpclient 3 , 479.Xr bsnmpagent 3 480.Sh STANDARDS 481This implementation conforms to the applicable IETF RFCs and ITU-T 482recommendations. 483.Sh AUTHORS 484.An Hartmut Brandt Aq harti@freebsd.org 485