openntpd-openbsd/src/lib/libutil/ber_get_string.3

.\" $OpenBSD: ber_get_string.3,v 1.7 2019/08/14 17:36:04 jmc Exp $
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.\" 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 .