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.\" $OpenBSD: ber_get_string.3,v 1.6 2019/08/14 17:21:42 martijn Exp $

.\"

.\" Copyright (c) 2007, 2012 Reyk Floeter <reyk@openbsd.org>

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.Dd $Mdocdate: August 14 2019 $

.Dt BER_GET_STRING 3

.Os

.Sh NAME

.Nm ber_get_null ,

.Nm ber_get_eoc ,

.Nm ber_get_integer ,

.Nm ber_get_enumerated ,

.Nm ber_get_boolean ,

.Nm ber_get_string ,

.Nm ber_get_nstring ,

.Nm ber_get_ostring ,

.Nm ber_get_bitstring ,

.Nm ber_get_oid ,

.Nm ber_getpos ,

.Nm ber_scanf_elements

.Nd access properties of ASN.1 objects decoded from BER

.Sh SYNOPSIS

.In sys/types.h

.In ber.h

.Ft "int"

.Fn "ber_get_null" "struct ber_element *root"

.Ft "int"

.Fn "ber_get_eoc" "struct ber_element *root"

.Ft "int"

.Fn "ber_get_integer" "struct ber_element *root" "long long *val"

.Ft "int"

.Fn "ber_get_enumerated" "struct ber_element *root" "long long *val"

.Ft "int"

.Fn "ber_get_boolean" "struct ber_element *root" "int *bool"

.Ft "int"

.Fn "ber_get_string" "struct ber_element *root" "char **charbuf"

.Ft "int"

.Fn "ber_get_nstring" "struct ber_element *root" "void **buf" "size_t *size"

.Ft "int"

.Fn "ber_get_ostring" "struct ber_element *root" "struct ber_octetstring *ostring"

.Ft "int"

.Fn "ber_get_bitstring" "struct ber_element *root" "void **buf" "size_t *size"

.Ft "int"

.Fn "ber_get_oid" "struct ber_element *root" "struct ber_oid *oid"

.Ft off_t

.Fn "ber_getpos" "struct ber_element *elm"

.Ft "int"

.Fn "ber_scanf_elements" "struct ber_element *root" "char *format" "..."

.Sh DESCRIPTION

Functions which take two arguments save the value contained in the

.Fa root

element into the storage location pointed to by the second argument.

Additionally,

.Fn ber_get_nstring

and

.Fn ber_get_bitstring

save the number of bytes contained in the string into

.Pf * Fa size .

.Pp

.Fn ber_scanf_elements

retrieves the values from zero or more elements starting at

.Fa root .

For each byte in

.Fa fmt ,

arguments of the types given in the following table are consumed

and passed to the function listed, processing one

.Vt ber_element

per byte.

The following bytes are valid:

.Bl -column -offset indent bytes ber_get_enumerated() "1: struct ber_element **"

.It Sy byte Ta Sy function Ta Sy arguments

.It B Ta Fn ber_get_bitstring  Ta 2: Vt void ** , size_t *

.It b Ta Fn ber_get_boolean    Ta 1: Vt int *

.It d Ta Fn ber_get_integer    Ta 1: Vt int *

.It E Ta Fn ber_get_enumerated Ta 1: Vt long long *

.It e Ta see below             Ta 1: Vt struct ber_element **

.It i Ta Fn ber_get_integer    Ta 1: Vt long long *

.It o Ta Fn ber_get_oid        Ta 1: Vt struct ber_oid *

.It p Ta Fn ber_getpos         Ta 1: Vt off_t *

.It S Ta see below             Ta 0

.It s Ta Fn ber_get_string     Ta 1: Vt char **

.It t Ta see below             Ta 2: Vt int * , unsigned int *

.It x Ta Fn ber_get_nstring    Ta 2: Vt void **, size_t *

.It \&( or { Ta see below      Ta 0

.It \&) or } Ta see below      Ta 0

.It \&. Ta Fn ber_get_eoc      Ta 0

.It 0 Ta Fn ber_get_null       Ta 0

.El

.Pp

For

.Sq e ,

.Sq p ,

.Sq S ,

and

.Sq t ,

the type of the element is not checked.

For

.Sq p ,

and

.Sq t

the pointer is not incremented to the next element.

For

.Sq e ,

a pointer to the element is stored in the corresponding pointer variable.

For

.Sq S ,

the element is skipped without extracting any information from it.

For

.Sq 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.

.Pp

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.

.Sh RETURN VALUES

.Fn ber_getpos

returns the value of

.Vt be_offs .

.Pp

.Fn ber_scanf_elements

returns 0 for success or \-1 when encountering elements that do not

agree with the expectations of

.Fa fmt

or when

.Fa fmt

is syntactically invalid.

Even when

.Fn ber_scanf_elements

fails, some of the arguments may already have been filled in.

.Pp

The other functions return 0 if

.Va root

is of the requested type or \-1 otherwise.

.Sh SEE ALSO

.Xr ber_add_string 3 ,

.Xr ber_oid_cmp 3 ,

.Xr ber_read_elements 3 ,

.Xr ber_set_header 3

.Sh STANDARDS

ITU-T Recommendation X.690, also known as ISO/IEC 8825-1:

Information technology - ASN.1 encoding rules.

.Sh HISTORY

These functions first appeared as internal functions in

.Xr snmpd 8

in

.Ox 4.2

and were moved to libutil in

.Ox 6.6 .

.Sh AUTHORS

.An -nosplit

The BER library was written by

.An Claudio Jeker Aq Mt claudio@openbsd.org ,

.An Marc Balmer Aq Mt marc@openbsd.org

and

								.An Reyk Floeter Aq Mt reyk@openbsd.org .