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> 10.\" 11.\" Redistribution and use in source and binary forms, with or without 12.\" modification, are permitted provided that the following conditions 13.\" are met: 14.\" 1. Redistributions of source code must retain the above copyright 15.\" notice, this list of conditions and the following disclaimer. 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in the 18.\" documentation and/or other materials provided with the distribution. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 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 74Begemot 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 147The ASN.1 library contains routines to handle ASN.1 encoding for SNMP. 148It supports only the restricted form of ASN.1 as required by SNMP. 149There 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 128 154 155/* type of subidentifiers */ 156typedef u_int32_t asn_subid_t; 157 158struct asn_oid { 159 u_int len; 160 asn_subid_t subs[ASN_MAXOIDLEN]; 161}; 162.Ed 163.Pp 164This structure represents an OID with the restrictions defined in the SNMP 165SMI. 166.Fa len 167holds the current length of the OID and 168.Fa subs 169holds the elements of the OID. 170.Bd -literal -offset indent 171struct 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 182This structure is used to encode and decode ASN.1. 183It 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. 188The first free byte is pointed to by 189.Fa asn_ptr . 190For decoding 191.Fa asn_len 192holds the number of remaining bytes to decode. 193The next byte to decode is pointed to 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. 224It 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 227in the value pointed to by 228.Fa lenp 229(this is restricted to a unsigned 32-bit value). 230All errors in this function are 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. 254This pointer must then be fed into 255.Fn asn_commit_header 256directly after writing the value to the buffer. 257The function will compute the 258length, insert it into the right place and shift the value if the resulting 259length field is shorter than the estimated one. 260.Pp 261The function 262.Fn asn_get_integer_raw 263is used to decode a signed integer value (32-bit). 264It assumes, that the 265header of the integer has been decoded already. 266.Fa len 267is the length obtained from the ASN.1 header and the integer will be returned 268in the value pointed to by 269.Fa res . 270.Pp 271The function 272.Fn asn_get_integer 273decodes a complete 32-bit signed integer including the header. 274If the tag is wrong 275.Li ASN_ERR_TAG 276is returned. 277The function 278.Fn asn_put_integer 279encodes a 32-bit signed integer. 280.Pp 281The function 282.Fn asn_get_octetstring_raw 283decodes the value field of an ASN.1 octet string. 284The length obtained from the header must be fed into the 285.Fa len 286argument and 287.Fa out 288must point to a buffer to receive the octet string. 289On entry to the function 290.Fa outsize 291must point to the size of the buffer. 292On exit 293.Fa outsize 294will point to the number of octets decoded (if no error occurs this will be 295equal to 296.Fa len ). 297The function 298.Fn asn_get_octetstring 299decodes an octetstring including the header. 300.Fa out 301must point to a buffer to receive the string, 302.Fa outsize 303must point to the size of the buffer. 304On exit of the function 305.Fa outsize 306will point to the number of octets decoded. 307The function 308.Fn asn_put_octetstring 309encodes an octetstring (including the header). 310.Fa str 311points to the string to encode and 312.Fa strsize 313is the length of the string (the string may contain embedded 314.Li NUL Ns s). 315.Pp 316The function 317.Fn asn_get_null_raw 318decodes a null value. 319.Fa len 320is the length obtained from the header and must be 0. 321The function 322.Fn asn_get_null 323decodes a null including the header and the function 324.Fn asn_put_null 325encodes a null. 326.Pp 327The function 328.Fn asn_put_exception 329is used to encode an SNMPv2 exception. 330The exception type is 331.Fa type . 332.Pp 333The function 334.Fn asn_get_objid_raw 335is used to decode an OID value. 336.Fa len 337must be the value length obtained from the header and 338.Fa oid 339will receive the decoded OID. 340The function 341.Fn asn_get_objid 342decodes a complete OID (including the header) and the function 343.Fn asn_put_objid 344encodes a complete OID. 345.Pp 346The function 347.Fn asn_get_sequence 348decodes a sequence header. 349The length of the sequence value will be stored in the value pointed to by 350.Fa lenp . 351.Pp 352The function 353.Fn asn_get_ipaddress_raw 354decodes an IP address value. 355.Fa len 356is the length from the header and must be 4. 357.Fa ipa 358will receive the decoded IP address and must point to a buffer of at least 359four bytes. 360The function 361.Fn asn_get_ipaddress 362decodes a complete IP address (including the header) and 363.Fn asn_put_ipaddress 364encodes an IP address. 365.Pp 366The function 367.Fn asn_get_uint32_raw 368decodes an unsigned 32-bit integer value. 369.Fa len 370is the length from the header and 371.Fa res 372will get the decoded value. 373The function 374.Fn asn_put_uint32 375encodes an unsigned 32-bit integer value and inserts the tag given in 376.Fa type 377into the header. 378.Pp 379The function 380.Fn asn_get_counter64_raw 381decodes an unsigned 64-bit integer value. 382.Fa len 383must be the value length from the header. 384The resulting value is stored into the variable pointed to by 385.Fa res . 386The function 387.Fn asn_put_counter64 388encodes a complete unsigned 64-bit value. 389.Pp 390The function 391.Fn asn_get_timeticks 392decodes an ASN.1 object of type 393.Li TIMETICKS 394and the function 395.Fn asn_put_timeticks 396encodes such an object. 397.Pp 398The function 399.Fn asn_skip 400can be used to skip 401.Fa len 402bytes in the input buffer. 403.Pp 404The function 405.Fn asn_slice_oid 406splits a part out from an OID. 407It takes all the subids from the OID pointed to by 408.Fa src 409starting with the subid at position 410.Fa from 411(the first subid being subid 0) up to, but not including, subid 412.Fa to 413and generates a new OID in 414.Fa dest . 415If 416.Fa to 417is less or equal to 418.Fa from 419the resulting OID will have a length of zero. 420.Pp 421The function 422.Fn asn_append_oid 423appends the OID 424.Fa from 425to the OID 426.Fa to 427given that the resulting OID is not too long. 428If the maximum length is exceeded the result is undefined. 429.Pp 430The function 431.Fn asn_compare_oid 432compares two oids and returns the values 433.Li -1 , 434.Li 0 or 435.Li +1 436when 437.Fa oid1 438is lesser than, equal, or larger than 439.Fa oid2 440resp. 441.Pp 442The function 443.Fn asn_is_suboid 444returns 1 if 445.Fa oid1 446is equal to the leading part of 447.Fa oid2 . 448It returns 0 otherwise. 449.Pp 450The function 451.Fn asn_oid2str_r 452makes a printable string from 453.Fa oid . 454The buffer pointed to by 455.Fa str 456must be large enough to hold the result. 457The constant 458.Li ASN_OIDSTRLEN 459is defined to be the length of the maximum string generated by this function 460(including the trailing NUL). 461The function 462.Fn asn_oid2str 463makes a printable string from 464.Fa oid 465into a private buffer that is overwritten by each call. 466.Sh DIAGNOSTICS 467When an error occurs in any of the function the function pointed to 468by the global pointer 469.Bd -literal -offset indent 470extern void (*asn_error)(const struct asn_buf *, const char *, ...); 471.Ed 472.Pp 473is called with the current buffer (this may be 474.Li NULL ) 475and a 476.Xr printf 3 477style format string. 478There is a default error handler in the library that prints a message 479starting with 480.Sq ASN.1: 481followed 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 489This implementation conforms to the applicable IETF RFCs and ITU-T 490recommendations. 491.Sh AUTHORS 492.An Hartmut Brandt Aq harti@FreeBSD.org 493