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 and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20.\" ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE 21.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27.\" SUCH DAMAGE. 28.\" 29.\" $Begemot: bsnmp/lib/asn1.3,v 1.5 2004/08/06 08:46:48 brandt Exp $ 30.\" 31.Dd August 15, 2002 32.Dt asn1 3 33.Os 34.Sh NAME 35.Nm asn_get_header , 36.Nm asn_put_header , 37.Nm asn_put_temp_header , 38.Nm asn_commit_header , 39.Nm asn_get_integer_raw , 40.Nm asn_get_integer , 41.Nm asn_put_integer , 42.Nm asn_get_octetstring_raw , 43.Nm asn_get_octetstring , 44.Nm asn_put_octetstring , 45.Nm asn_get_null_raw , 46.Nm asn_get_null , 47.Nm asn_put_null , 48.Nm asn_put_exception , 49.Nm asn_get_objid_raw , 50.Nm asn_get_objid , 51.Nm asn_put_objid , 52.Nm asn_get_sequence , 53.Nm asn_get_ipaddress_raw , 54.Nm asn_get_ipaddress , 55.Nm asn_put_ipaddress , 56.Nm asn_get_uint32_raw , 57.Nm asn_put_uint32 , 58.Nm asn_get_counter64_raw , 59.Nm asn_put_counter64 , 60.Nm asn_get_timeticks , 61.Nm asn_put_timeticks , 62.Nm asn_skip , 63.Nm asn_slice_oid , 64.Nm asn_append_oid , 65.Nm asn_compare_oid , 66.Nm asn_is_suboid , 67.Nm asn_oid2str_r , 68.Nm asn_oid2str 69.Nd "ASN.1 library for SNMP" 70.Sh LIBRARY 71Begemot SNMP library 72.Pq libbsnmp, -lbsnmp 73.Sh SYNOPSIS 74.In bsnmp/asn1.h 75.Ft enum asn_err 76.Fn asn_get_header "struct asn_buf *buf" "u_char *type" "asn_len_t *lenp" 77.Ft enum asn_err 78.Fn asn_put_header "struct asn_buf *buf" "u_char type" "asn_len_t len" 79.Ft enum asn_err 80.Fn asn_put_temp_header "struct asn_buf *buf" "u_char type" "u_char **ptr" 81.Ft enum asn_err 82.Fn asn_commit_header "struct asn_buf *buf" "u_char *ptr" 83.Ft enum asn_err 84.Fn asn_get_integer_raw "struct asn_buf *buf" "asn_len_t len" "int32_t *res" 85.Ft enum asn_err 86.Fn asn_get_integer "struct asn_buf *buf" "int32_t *res" 87.Ft enum asn_err 88.Fn asn_put_integer "struct asn_buf *buf" "int32_t arg" 89.Ft enum asn_err 90.Fn asn_get_octetstring_raw "struct asn_buf *buf" "asn_len_t len" "u_char *out" "u_int *outsize" 91.Ft enum asn_err 92.Fn asn_get_octetstring "struct asn_buf *buf" "u_char *out" "u_int *outsize" 93.Ft enum asn_err 94.Fn asn_put_octetstring "struct asn_buf *buf" "const u_char *str" "u_int strsize" 95.Ft enum asn_err 96.Fn asn_get_null_raw "struct asn_buf *buf" "asn_len_t len" 97.Ft enum asn_err 98.Fn asn_get_null "struct asn_buf *buf" 99.Ft enum asn_err 100.Fn asn_put_null "struct asn_buf *buf" 101.Ft enum asn_err 102.Fn asn_put_exception "struct asn_buf *buf" "u_int type" 103.Ft enum asn_err 104.Fn asn_get_objid_raw "struct asn_buf *buf" "asn_len_t len" "struct asn_oid *oid" 105.Ft enum asn_err 106.Fn asn_get_objid "struct asn_buf *buf" "struct asn_oid *oid" 107.Ft enum asn_err 108.Fn asn_put_objid "struct asn_buf *buf" "const struct asn_oid *oid" 109.Ft enum asn_err 110.Fn asn_get_sequence "struct asn_buf *buf" "asn_len_t *lenp" 111.Ft enum asn_err 112.Fn asn_get_ipaddress_raw "struct asn_buf *buf" "asn_len_t len" "u_char *ipa" 113.Ft enum asn_err 114.Fn asn_get_ipaddress "struct asn_buf *buf" "u_char *ipa" 115.Ft enum asn_err 116.Fn asn_put_ipaddress "struct asn_buf *buf" "const u_char *ipa" 117.Ft enum asn_err 118.Fn asn_get_uint32_raw "struct asn_buf *buf" "asn_len_t len" "u_int32_t *res" 119.Ft enum asn_err 120.Fn asn_put_uint32 "struct asn_buf *buf" "u_char type" "u_int32_t val" 121.Ft enum asn_err 122.Fn asn_get_counter64_raw "struct asn_buf *buf" "asn_len_t len" "u_int64_t *res" 123.Ft enum asn_err 124.Fn asn_put_counter64 "struct asn_buf *buf" "u_int64_t val" 125.Ft enum asn_err 126.Fn asn_get_timeticks "struct asn_buf *buf" "u_int32_t *valp" 127.Ft enum asn_err 128.Fn asn_put_timeticks "struct asn_buf *buf" "u_int32_t val" 129.Ft enum asn_err 130.Fn asn_skip "struct asn_buf *buf" "asn_len_t len" 131.Ft void 132.Fn asn_slice_oid "struct asn_oid *dest" "const struct asn_oid *src" "u_int from" "u_int to" 133.Ft void 134.Fn asn_append_oid "struct asn_oid *to" "const struct asn_oid *from" 135.Ft int 136.Fn asn_compare_oid "const struct asn_oid *oid1" "const struct asn_oid *oid2" 137.Ft int 138.Fn asn_is_suboid "const struct asn_oid *oid1" "const struct asn_oid *oid2" 139.Ft char * 140.Fn asn_oid2str_r "const struct asn_oid *oid" "char *buf" 141.Ft char * 142.Fn asn_oid2str "const struct asn_oid *oid" 143.Sh DESCRIPTION 144The ASN.1 library contains routines to handle ASN.1 encoding for SNMP. 145It supports only the restricted form of ASN.1 as required by SNMP. There 146are two basic structures used throughout the library: 147.Bd -literal -offset indent 148/* these restrictions are in the SMI */ 149#define ASN_MAXID 0xffffffff 150#define ASN_MAXOIDLEN 128 151 152/* type of subidentifiers */ 153typedef u_int32_t asn_subid_t; 154 155struct asn_oid { 156 u_int len; 157 asn_subid_t subs[ASN_MAXOIDLEN]; 158}; 159.Ed 160.Pp 161This structure represents an OID with the restrictions defined in the SNMP 162SMI. 163.Fa len 164holds the current length of the OID and 165.Fa subs 166holds the elements of the OID. 167.Bd -literal -offset indent 168struct asn_buf { 169 union { 170 u_char *ptr; 171 const u_char *cptr; 172 } asn_u; 173 size_t asn_len; 174}; 175#define asn_cptr asn_u.cptr 176#define asn_ptr asn_u.ptr 177.Ed 178.Pp 179This structure is used to encode and decode ASN.1. It describes the output 180buffer for encoding routines and the input buffer for decoding routines. 181For encoding 182.Fa asn_len 183holds the number of remaining free octets in the buffer. The first free byte 184is pointed to by 185.Fa asn_ptr . 186For decoding 187.Fa asn_len 188holds the number of remaining bytes to decode. The next byte to decode is pointed 189to by 190.Fa asn_cptr . 191.Pp 192Most of the functions return an error code 193.Fa "enum asn_error" : 194.Bd -literal -offset indent 195enum asn_err { 196 /* conversion was ok */ 197 ASN_ERR_OK = 0, 198 /* conversion failed and stopped */ 199 ASN_ERR_FAILED = 1 | 0x1000, 200 /* length field bad, value skipped */ 201 ASN_ERR_BADLEN = 2, 202 /* out of buffer, stopped */ 203 ASN_ERR_EOBUF = 3 | 0x1000, 204 /* length ok, but value is out of range */ 205 ASN_ERR_RANGE = 4, 206 /* not the expected tag, stopped */ 207 ASN_ERR_TAG = 5 | 0x1000, 208}; 209#define ASN_ERR_STOPPED(E) (((E) & 0x1000) != 0) 210.Ed 211.Pp 212If 213.Fn ASN_ERR_STOPPED 214returns true, the error was fatal and processing has stopped at the point 215of error. 216.Pp 217The function 218.Fn asn_get_header 219reads the next header from the input octet stream. It returns the tag 220in the variable pointed to by 221.Fa type 222(note that only single byte tags are supported) and the decoded length field 223in the value pointed to by 224.Fa lenp 225(this is restricted to a unsigned 32-bit value). All errors in this function 226are fatal and stop processing. 227.Pp 228The function 229.Fn asn_put_header 230writes an ASN.1 header. 231.Fa type 232is the tag to write and is restricted to one byte tags (i.e. tags 233lesser or equal than 0x30). 234.Fa len 235is the length of the value and is restricted to 16-bit. 236.Pp 237The functions 238.Fn asn_put_temp_header 239and 240.Fn asn_commit_header 241are used to write a header when the length of the value is not known in 242advance, for example, for sequences. 243.Fn asn_put_temp_header 244writes a header with the given tag 245.Fa type 246and space for the maximum supported length field and sets the pointer pointed 247to by 248.Fa ptr 249to the begin of this length field. This pointer must then be fed into 250.Fn asn_commit_header 251directly after writing the value to the buffer. The function will compute the 252length, insert it into the right place and shift the value if the resulting 253length field is shorter than the estimated one. 254.Pp 255The function 256.Fn asn_get_integer_raw 257is used to decode a signed integer value (32-bit). It assumes, that the 258header of the integer has been decoded already. 259.Fa len 260is the length obtained from the ASN.1 header and the integer will be returned 261in the value pointed to by 262.Fa res . 263.Pp 264The function 265.Fn asn_get_integer 266decodes a complete 32-bit signed integer including the header. If the 267tag is wrong 268.Li ASN_ERR_TAG 269is returned. 270The function 271.Fn asn_put_integer 272encodes a 32-bit signed integer. 273.Pp 274The function 275.Fn asn_get_octetstring_raw 276decodes the value field of an ASN.1 octet string. The length obtained from the 277header must be fed into the 278.Fa len 279argument and 280.Fa out 281must point to a buffer to receive the octet string. On entry to the function 282.Fa outsize 283must point to the size of the buffer. On exit 284.Fa outsize 285will point to the number of octets decoded (if no error occurs this will be 286equal to 287.Fa len ). 288The function 289.Fn asn_get_octetstring 290decodes an octetstring including the header. 291.Fa out 292must point to a buffer to receive the string, 293.Fa outsize 294must point to the size of the buffer. On exit of the function 295.Fa outsize 296will point to the number of octets decoded. 297The function 298.Fn asn_put_octetstring 299encodes an octetstring (including the header). 300.Fa str 301points to the string to encode and 302.Fa strsize 303is the length of the string (the string may contain embedded 304.Li NUL Ns s). 305.Pp 306The function 307.Fn asn_get_null_raw 308decodes a null value. 309.Fa len 310is the length obtained from the header and must be 0. 311The function 312.Fn asn_get_null 313decodes a null including the header and the function 314.Fn asn_put_null 315encodes a null. 316.Pp 317The function 318.Fn asn_put_exception 319is used to encode an SNMPv2 exception. The exception type is 320.Fa type . 321.Pp 322The function 323.Fn asn_get_objid_raw 324is used to decode an OID value. 325.Fa len 326must be the value length obtained from the header and 327.Fa oid 328will receive the decoded OID. 329The function 330.Fn asn_get_objid 331decodes a complete OID (including the header) and the function 332.Fn asn_put_objid 333encodes a complete OID. 334.Pp 335The function 336.Fn asn_get_sequence 337decodes a sequence header. 338The length of the sequence value will be stored in the value pointed to by 339.Fa lenp . 340.Pp 341The function 342.Fn asn_get_ipaddress_raw 343decodes an IP address value. 344.Fa len 345is the length from the header and must be 4. 346.Fa ipa 347will receive the decoded IP address and must point to a buffer of at least 348four bytes. 349The function 350.Fn asn_get_ipaddress 351decodes a complete IP address (including the header) and 352.Fn asn_put_ipaddress 353encodes an IP address. 354.Pp 355The function 356.Fn asn_get_uint32_raw 357decodes an unsigned 32-bit integer value. 358.Fa len 359is the length from the header and 360.Fa res 361will get the decoded value. 362The function 363.Fn asn_put_uint32 364encodes an unsigned 32-bit integer value and inserts the tag given in 365.Fa type 366into the header. 367.Pp 368The function 369.Fn asn_get_counter64_raw 370decodes an unsigned 64-bit integer value. 371.Fa len 372must be the value length from the header. The resulting value is 373stored into the variable pointed to by 374.Fa res . 375The function 376.Fn asn_put_counter64 377encodes a complete unsigned 64-bit value. 378.Pp 379The function 380.Fn asn_get_timeticks 381decodes an ASN.1 object of type 382.Li TIMETICKS 383and the function 384.Fn asn_put_timeticks 385encodes such an object. 386.Pp 387The function 388.Fn asn_skip 389can be used to skip 390.Fa len 391bytes in the input buffer. 392.Pp 393The function 394.Fn asn_slice_oid 395splits a part out from an OID. It takes all the subids from the OID 396pointed to by 397.Fa src 398starting with the subid at position 399.Fa from 400(the first subid beeing subid 0) up to, but not including, subid 401.Fa to 402and generates a new OID in 403.Fa dest . 404If 405.Fa to 406is less or equal to 407.Fa from 408the resulting OID will have a length of zero. 409.Pp 410The function 411.Fn asn_append_oid 412appends the OID 413.Fa from 414to the OID 415.Fa to 416given that the resulting OID is not too long. If the maximum length is exceeded 417the result is undefined. 418.Pp 419The function 420.Fn asn_compare_oid 421compares two oids and returns the values 422.Li -1 , 423.Li 0 or 424.Li +1 425when 426.Fa oid1 427is lesser than, equal, or larger than 428.Fa oid2 429resp. 430.Pp 431The function 432.Fn asn_is_suboid 433returns 1 if 434.Fa oid1 435is equal to the leading part of 436.Fa oid2 . 437It returns 0 otherwise. 438.Pp 439The function 440.Fn asn_oid2str_r 441makes a printable string from 442.Fa oid . 443The buffer pointed to by 444.Fa str 445must be large enough to hold the result. The constant 446.Li ASN_OIDSTRLEN 447is defined to be the length of the maximum string generated by this function 448(including the trailing NUL). 449The function 450.Fn asn_oid2str 451makes a printable string from 452.Fa oid 453into a private buffer that is overwritten by each call. 454.Sh DIAGNOSTICS 455When an error occures in any of the function the function pointed to 456by the global pointer 457.Bd -literal -offset indent 458extern void (*asn_error)(const struct asn_buf *, const char *, ...); 459.Ed 460.Pp 461is called with the current buffer (this may be 462.Li NULL ) 463and a 464.Xr printf 3 465style format string. 466There is a default error handler in the library that prints a message 467starting with 468.Sq ASN.1: 469followed by the error message and an optional dump of the buffer. 470.Sh SEE ALSO 471.Xr snmpd 1 , 472.Xr gensnmptree 1 , 473.Xr bsnmplib 3 474.Xr bsnmpclient 3 , 475.Xr bsnmpagent 3 476.Sh STANDARDS 477This implementation conforms to the applicable IETF RFCs and ITU-T 478recommendations. 479.Sh AUTHORS 480.An Hartmut Brandt Aq harti@freebsd.org 481