OBER_GET_STRING(3) | Library Functions Manual | OBER_GET_STRING(3)

# NAME

`ober_get_null`, `ober_get_eoc`, `ober_get_integer`, `ober_get_enumerated`, `ober_get_boolean`, `ober_get_string`, `ober_get_nstring`, `ober_get_ostring`, `ober_get_bitstring`, `ober_get_oid`, `ober_getpos`, `ober_scanf_elements` — access properties of ASN.1 objects decoded from BER

# SYNOPSIS

System Utilities Library (libutil, -lutil)
`#include <sys/types.h>`
`#include <ber.h>`

int
`ober_get_null`(struct ber_element *root);

int
`ober_get_eoc`(struct ber_element *root);

int
`ober_get_integer`(struct ber_element *root, long long *val);

int
`ober_get_enumerated`(struct ber_element *root, long long *val);

int
`ober_get_boolean`(struct ber_element *root, int *bool);

int
`ober_get_string`(struct ber_element *root, char **charbuf);

int
`ober_get_nstring`(struct ber_element *root, void **buf, size_t *size);

int
`ober_get_ostring`(struct ber_element *root, struct ber_octetstring *ostring);

int
`ober_get_bitstring`(struct ber_element *root, void **buf, size_t *size);

int
`ober_get_oid`(struct ber_element *root, struct ber_oid *oid);

off_t
`ober_getpos`(struct ber_element *elm);

int
`ober_scanf_elements`(struct ber_element *root, char *format, ...);

# DESCRIPTION

Functions which take two arguments save the value contained in the root element into the storage location pointed to by the second argument. If the storage location is `NULL` then only a type check is performed. Additionally, `ober_get_nstring`() and `ober_get_bitstring`() save the number of bytes contained in the string into *size. If buf is `NULL` and size is not `NULL`, size is set. size must not be `NULL` to return a valid buf.

`ober_scanf_elements`() retrieves the values from zero or more elements starting at root. For each character in fmt, arguments of the types given in the following table are consumed and passed to the function listed, processing one ber_element per character. The following characters are valid:

character | function | arguments
$ | see below | 0
B | `ober_get_bitstring`() | 2: void **, size_t *
b | `ober_get_boolean`() | 1: int *
d | `ober_get_integer`() | 1: int *
E | `ober_get_enumerated`() | 1: long long *
e | see below | 1: struct ber_element **
i | `ober_get_integer`() | 1: long long *
o | `ober_get_oid`() | 1: struct ber_oid *
p | `ober_getpos`() | 1: off_t *
S | see below | 0
s | `ober_get_string`() | 1: char **
t | see below | 2: int *, unsigned int *
x | `ober_get_nstring`() | 2: void **, size_t *
( or { | see below | 0
) or } | see below | 0
. | `ober_get_eoc`() | 0
0 | `ober_get_null`() | 0

For ‘e’, ‘p’, ‘S’, and ‘t’, the type of the element is not checked. For ‘p’ and ‘t’, the pointer is not incremented to the next element. For ‘e’, a pointer to the element is stored in the corresponding pointer variable. For ‘S’, the element is skipped without extracting any information from it. For ‘t’, the class and type of the element are stored in the two corresponding variables, but if the element contains a value, that value is ignored. A ‘$’ mandates the end of a sequence or set.

For an opening parenthesis or brace, it is checked that the element is a sequence or a set, and parsing continues with its children. For a closing parenthesis or brace, parsing of the current sequence or set is ended and parsing continues with the element following the sequence or set.

# RETURN VALUES

`ober_getpos`() returns the value of be_offs.

`ober_scanf_elements`() returns 0 for success or -1 when encountering elements that do not agree with the expectations of fmt or when fmt is syntactically invalid. Even when `ober_scanf_elements`() fails, some of the arguments may already have been filled in.

The other functions return 0 if root is of the requested type or -1 otherwise.

# SEE ALSO

ober_add_string(3), ober_oid_cmp(3), ober_read_elements(3), ober_set_header(3)

# STANDARDS

ITU-T Recommendation X.690, also known as ISO/IEC 8825-1: Information technology - ASN.1 encoding rules.

# HISTORY

These functions first appeared as internal functions in snmpd(8) in OpenBSD 4.2 and were moved to libutil in OpenBSD 6.6.

# AUTHORS

The BER library was written by Claudio Jeker <claudio@openbsd.org>, Marc Balmer <marc@openbsd.org> and Reyk Floeter <reyk@openbsd.org>.

June 13, 2025 | Debian