asn1(3)

NAME

asn_get_header, asn_put_header, asn_put_temp_header,
asn_commit_header,
asn_get_integer_raw, asn_get_integer, asn_put_integer, asn_get_octetstring_raw, asn_get_octetstring,
asn_put_octetstring,
asn_get_null_raw, asn_get_null, asn_put_null,
asn_put_exception,
asn_get_objid_raw, asn_get_objid, asn_put_objid,
asn_get_sequence,
asn_get_ipaddress_raw, asn_get_ipaddress, asn_put_ipaddress, asn_get_uint32_raw, asn_put_uint32, asn_get_counter64_raw, asn_put_counter64, asn_get_timeticks, asn_put_timeticks,
asn_skip,
asn_slice_oid, asn_append_oid, asn_compare_oid,
asn_is_suboid,
asn_oid2str_r, asn_oid2str - ASN.1 library for SNMP

LIBRARY

Begemot SNMP library (libbsnmp, -lbsnmp)

SYNOPSIS

#include <bsnmp/asn1.h>
enum asn_err
asn_get_header(struct  asn_buf *buf, u_char *type, asn_len_t
*lenp);
enum asn_err
asn_put_header(struct asn_buf *buf, u_char  type,  asn_len_t
len);
enum asn_err
asn_put_temp_header(struct asn_buf *buf, u_char type, u_char
**ptr);
enum asn_err
asn_commit_header(struct asn_buf *buf, u_char *ptr);
enum asn_err
asn_get_integer_raw(struct  asn_buf  *buf,  asn_len_t   len,
int32_t *res);
enum asn_err
asn_get_integer(struct asn_buf *buf, int32_t *res);
enum asn_err
asn_put_integer(struct asn_buf *buf, int32_t arg);
enum asn_err
asn_get_octetstring_raw(struct  asn_buf *buf, asn_len_t len,
u_char *out,
        u_int *outsize);
enum asn_err
asn_get_octetstring(struct asn_buf *buf, u_char *out,  u_int
*outsize);
enum asn_err
asn_put_octetstring(struct asn_buf *buf, const u_char *str,
        u_int strsize);
enum asn_err
asn_get_null_raw(struct asn_buf *buf, asn_len_t len);
enum asn_err
asn_get_null(struct asn_buf *buf);
enum asn_err
asn_put_null(struct asn_buf *buf);
enum asn_err
asn_put_exception(struct asn_buf *buf, u_int type);
enum asn_err
asn_get_objid_raw(struct asn_buf *buf, asn_len_t len,
        struct asn_oid *oid);
enum asn_err
asn_get_objid(struct asn_buf *buf, struct asn_oid *oid);
enum asn_err
asn_put_objid(struct  asn_buf  *buf,  const  struct  asn_oid
*oid);
enum asn_err
asn_get_sequence(struct asn_buf *buf, asn_len_t *lenp);
enum asn_err
asn_get_ipaddress_raw(struct asn_buf  *buf,  asn_len_t  len,
u_char *ipa);
enum asn_err
asn_get_ipaddress(struct asn_buf *buf, u_char *ipa);
enum asn_err
asn_put_ipaddress(struct asn_buf *buf, const u_char *ipa);
enum asn_err
asn_get_uint32_raw(struct   asn_buf   *buf,  asn_len_t  len,
u_int32_t *res);
enum asn_err
asn_put_uint32(struct asn_buf *buf, u_char  type,  u_int32_t
val);
enum asn_err
asn_get_counter64_raw(struct asn_buf *buf, asn_len_t len,
        u_int64_t *res);
enum asn_err
asn_put_counter64(struct asn_buf *buf, u_int64_t val);
enum asn_err
asn_get_timeticks(struct asn_buf *buf, u_int32_t *valp);
enum asn_err
asn_put_timeticks(struct asn_buf *buf, u_int32_t val);
enum asn_err
asn_skip(struct asn_buf *buf, asn_len_t len);
void
asn_slice_oid(struct  asn_oid  *dest,  const  struct asn_oid
*src,
        u_int from, u_int to);
void
asn_append_oid(struct  asn_oid  *to,  const  struct  asn_oid
*from);
int
asn_compare_oid(const  struct  asn_oid  *oid1,  const struct
asn_oid *oid2);
int
asn_is_suboid(const  struct  asn_oid  *oid1,  const   struct
asn_oid *oid2);
char *
asn_oid2str_r(const struct asn_oid *oid, char *buf);
char *
asn_oid2str(const struct asn_oid *oid);

DESCRIPTION

The ASN.1 library contains routines to handle ASN.1 encoding
for SNMP. It supports only the restricted form of ASN.1 as required by
SNMP. There are two basic structures used throughout the library:: /* these restrictions are in the SMI */
#define ASN_MAXID 0xffffffff
#define ASN_MAXOIDLEN 128; /* type of subidentifiers */
typedef u_int32_t asn_subid_t;; struct asn_oid {
u_int len;
asn_subid_t subs[ASN_MAXOIDLEN];; };
This structure represents an OID with the restrictions de
fined in the SNMP SMI. len holds the current length of the OID and subs
holds the elements of the OID.: struct asn_buf {
union {
u_char *ptr;
const u_char *cptr;

} asn_u;
size_t asn_len;; };
#define asn_cptr asn_u.cptr
#define asn_ptr asn_u.ptr
This structure is used to encode and decode ASN.1. It de
scribes the output buffer for encoding routines and the input buffer for
decoding routines. For encoding asn_len holds the number of remaining
free octets in
the buffer. The first free byte is pointed to by asn_ptr.
For decoding
asn_len holds the number of remaining bytes to decode. The
next byte to
decode is pointed to by asn_cptr.
Most of the functions return an error code enum asn_error:: enum asn_err {
/* conversion was ok */
ASN_ERR_OK = 0,
/* conversion failed and stopped */
ASN_ERR_FAILED = 1 | 0x1000,
/* length field bad, value skipped */
ASN_ERR_BADLEN = 2,
/* out of buffer, stopped */
ASN_ERR_EOBUF = 3 | 0x1000,
/* length ok, but value is out of range */
ASN_ERR_RANGE = 4,
/* not the expected tag, stopped */
ASN_ERR_TAG = 5 | 0x1000,; };
#define ASN_ERR_STOPPED(E) (((E) & 0x1000) != 0)
If ASN_ERR_STOPPED() returns true, the error was fatal and
processing has stopped at the point of error.
The function asn_get_header() reads the next header from the
input octet stream. It returns the tag in the variable pointed to by
type (note that only single byte tags are supported) and the decoded length
field in the value pointed to by lenp (this is restricted to a unsigned
32-bit value). All errors in this function are fatal and stop processing.
The function asn_put_header() writes an ASN.1 header. type
is the tag to write and is restricted to one byte tags (i.e., tags lesser
or equal than 0x30). len is the length of the value and is restricted to
16-bit.
The functions asn_put_temp_header() and asn_commit_header()
are used to write a header when the length of the value is not known in
advance, for
example, for sequences. asn_put_temp_header() writes a
header with the given tag type and space for the maximum supported length
field and sets the pointer pointed to by ptr to the begin of this length
field. This
pointer must then be fed into asn_commit_header() directly
after writing the value to the buffer. The function will compute the
length, insert it into the right place and shift the value if the resulting
length field is shorter than the estimated one.
The function asn_get_integer_raw() is used to decode a
signed integer value (32-bit). It assumes, that the header of the integer
has been decoded already. len is the length obtained from the ASN.1
header and the integer will be returned in the value pointed to by res.
The function asn_get_integer() decodes a complete 32-bit
signed integer including the header. If the tag is wrong ASN_ERR_TAG is
returned. The
function asn_put_integer() encodes a 32-bit signed integer.
The function asn_get_octetstring_raw() decodes the value
field of an ASN.1 octet string. The length obtained from the header
must be fed into the len argument and out must point to a buffer to receive
the octet string. On entry to the function outsize must point to the
size of the buffer. On exit outsize will point to the number of octets
decoded (if
no error occurs this will be equal to len ). The function
asn_get_octetstring() decodes an octetstring including the
header. out must point to a buffer to receive the string, outsize must
point to the size of the buffer. On exit of the function outsize will
point to the number of octets decoded. The function
asn_put_octetstring() encodes an
octetstring (including the header). str points to the
string to encode and strsize is the length of the string (the string may con
tain embedded NULs).
The function asn_get_null_raw() decodes a null value. len
is the length obtained from the header and must be 0. The function
asn_get_null()
decodes a null including the header and the function
asn_put_null()
encodes a null.
The function asn_put_exception() is used to encode an SNMPv2
exception. The exception type is type.
The function asn_get_objid_raw() is used to decode an OID
value. len must be the value length obtained from the header and oid
will receive
the decoded OID. The function asn_get_objid() decodes a
complete OID
(including the header) and the function asn_put_objid() en
codes a complete OID.
The function asn_get_sequence() decodes a sequence header.
The length of the sequence value will be stored in the value pointed to by
lenp.
The function asn_get_ipaddress_raw() decodes an IP address
value. len is the length from the header and must be 4. ipa will receive
the decoded IP address and must point to a buffer of at least four
bytes. The function asn_get_ipaddress() decodes a complete IP address (in
cluding the
header) and asn_put_ipaddress() encodes an IP address.
The function asn_get_uint32_raw() decodes an unsigned 32-bit
integer value. len is the length from the header and res will get
the decoded
value. The function asn_put_uint32() encodes an unsigned
32-bit integer value and inserts the tag given in type into the header.
The function asn_get_counter64_raw() decodes an unsigned
64-bit integer value. len must be the value length from the header. The
resulting value is stored into the variable pointed to by res. The
function
asn_put_counter64() encodes a complete unsigned 64-bit val
ue.
The function asn_get_timeticks() decodes an ASN.1 object of
type
TIMETICKS and the function asn_put_timeticks() encodes such
an object.
The function asn_skip() can be used to skip len bytes in the
input buffer.
The function asn_slice_oid() splits a part out from an OID.
It takes all the subids from the OID pointed to by src starting with the
subid at position from (the first subid being subid 0) up to, but not
including, subid to and generates a new OID in dest. If to is less or
equal to from the resulting OID will have a length of zero.
The function asn_append_oid() appends the OID from to the
OID to given that the resulting OID is not too long. If the maximum
length is exceeded the result is undefined.
The function asn_compare_oid() compares two oids and returns
the values -1, 0 or +1 when oid1 is lesser than, equal, or larger than
oid2 resp.
The function asn_is_suboid() returns 1 if oid1 is equal to
the leading part of oid2. It returns 0 otherwise.
The function asn_oid2str_r() makes a printable string from
oid. The buffer pointed to by str must be large enough to hold the
result. The constant ASN_OIDSTRLEN is defined to be the length of the
maximum string generated by this function (including the trailing NUL).
The function
asn_oid2str() makes a printable string from oid into a pri
vate buffer that is overwritten by each call.

DIAGNOSTICS

When an error occurs in any of the function the function
pointed to by the global pointer: extern void (*asn_error)(const struct asn_buf *, const; char *, ...);
is called with the current buffer (this may be NULL) and a
printf(3) style format string. There is a default error handler in
the library that prints a message starting with `ASN.1:' followed by the
error message and an optional dump of the buffer.

STANDARDS

This implementation conforms to the applicable IETF RFCs and
ITU-T recommendations.

AUTHORS

Hartmut Brandt <harti@freebsd.org>
BSD October 4, 2005

docs.sk

comprehensive documentation repository

See also

asn1(3)

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

DIAGNOSTICS

SEE ALSO

STANDARDS

AUTHORS