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1.\" $OpenBSD: ober_get_string.3,v 1.8 2025/06/13 18:34:00 schwarze Exp $
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3.\" Copyright (c) 2007, 2012 Reyk Floeter <reyk@openbsd.org>
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17.Dd $Mdocdate: June 13 2025 $
18.Dt OBER_GET_STRING 3
19.Os
20.Sh NAME
21.Nm ober_get_null ,
22.Nm ober_get_eoc ,
23.Nm ober_get_integer ,
24.Nm ober_get_enumerated ,
25.Nm ober_get_boolean ,
26.Nm ober_get_string ,
27.Nm ober_get_nstring ,
28.Nm ober_get_ostring ,
29.Nm ober_get_bitstring ,
30.Nm ober_get_oid ,
31.Nm ober_getpos ,
32.Nm ober_scanf_elements
33.Nd access properties of ASN.1 objects decoded from BER
34.Sh SYNOPSIS
35.Lb libutil
36.In sys/types.h
37.In ber.h
38.Ft int
39.Fn "ober_get_null" "struct ber_element *root"
40.Ft int
41.Fn "ober_get_eoc" "struct ber_element *root"
42.Ft int
43.Fn "ober_get_integer" "struct ber_element *root" "long long *val"
44.Ft int
45.Fn "ober_get_enumerated" "struct ber_element *root" "long long *val"
46.Ft int
47.Fn "ober_get_boolean" "struct ber_element *root" "int *bool"
48.Ft int
49.Fn "ober_get_string" "struct ber_element *root" "char **charbuf"
50.Ft int
51.Fn "ober_get_nstring" "struct ber_element *root" "void **buf" "size_t *size"
52.Ft int
53.Fn "ober_get_ostring" "struct ber_element *root" "struct ber_octetstring *ostring"
54.Ft int
55.Fn "ober_get_bitstring" "struct ber_element *root" "void **buf" "size_t *size"
56.Ft int
57.Fn "ober_get_oid" "struct ber_element *root" "struct ber_oid *oid"
58.Ft off_t
59.Fn "ober_getpos" "struct ber_element *elm"
60.Ft int
61.Fn "ober_scanf_elements" "struct ber_element *root" "char *format" "..."
62.Sh DESCRIPTION
63Functions which take two arguments save the value contained in the
64.Fa root
65element into the storage location pointed to by the second argument.
66If the storage location is
67.Dv NULL
68then only a type check is performed.
69Additionally,
70.Fn ober_get_nstring
71and
72.Fn ober_get_bitstring
73save the number of bytes contained in the string into
74.Pf * Fa size .
75If
76.Fa buf
77is
78.Dv NULL
79and size is not
80.Dv NULL ,
81size is set.
82.Fa size
83must not be
84.Dv NULL
85to return a valid
86.Fa buf .
87.Pp
88.Fn ober_scanf_elements
89retrieves the values from zero or more elements starting at
90.Fa root .
91For each character in
92.Fa fmt ,
93arguments of the types given in the following table are consumed
94and passed to the function listed, processing one
95.Vt ber_element
96per character.
97The following characters are valid:
98.Bl -column -offset indent\
99 characte ober_get_enumerated_ "1: struct ber_element **"
100.It Sy character Ta Sy function Ta Sy arguments
101.It $ Ta see below Ta 0
102.It B Ta Fn ober_get_bitstring Ta 2: Vt void ** , size_t *
103.It b Ta Fn ober_get_boolean Ta 1: Vt int *
104.It d Ta Fn ober_get_integer Ta 1: Vt int *
105.It E Ta Fn ober_get_enumerated Ta 1: Vt long long *
106.It e Ta see below Ta 1: Vt struct ber_element **
107.It i Ta Fn ober_get_integer Ta 1: Vt long long *
108.It o Ta Fn ober_get_oid Ta 1: Vt struct ber_oid *
109.It p Ta Fn ober_getpos Ta 1: Vt off_t *
110.It S Ta see below Ta 0
111.It s Ta Fn ober_get_string Ta 1: Vt char **
112.It t Ta see below Ta 2: Vt int * , unsigned int *
113.It x Ta Fn ober_get_nstring Ta 2: Vt void **, size_t *
114.It \&( or { Ta see below Ta 0
115.It \&) or } Ta see below Ta 0
116.It \&. Ta Fn ober_get_eoc Ta 0
117.It 0 Ta Fn ober_get_null Ta 0
118.El
119.Pp
120For
121.Sq e ,
122.Sq p ,
123.Sq S ,
124and
125.Sq t ,
126the type of the element is not checked.
127For
128.Sq p
129and
130.Sq t ,
131the pointer is not incremented to the next element.
132For
133.Sq e ,
134a pointer to the element is stored in the corresponding pointer variable.
135For
136.Sq S ,
137the element is skipped without extracting any information from it.
138For
139.Sq t ,
140the class and type of the element are stored in the two corresponding
141variables, but if the element contains a value, that value is ignored.
142A
143.Sq $
144mandates the end of a sequence or set.
145.Pp
146For an opening parenthesis or brace, it is checked that the element
147is a sequence or a set, and parsing continues with its children.
148For a closing parenthesis or brace, parsing of the current sequence
149or set is ended and parsing continues with the element following
150the sequence or set.
151.Sh RETURN VALUES
152.Fn ober_getpos
153returns the value of
154.Vt be_offs .
155.Pp
156.Fn ober_scanf_elements
157returns 0 for success or \-1 when encountering elements that do not
158agree with the expectations of
159.Fa fmt
160or when
161.Fa fmt
162is syntactically invalid.
163Even when
164.Fn ober_scanf_elements
165fails, some of the arguments may already have been filled in.
166.Pp
167The other functions return 0 if
168.Va root
169is of the requested type or \-1 otherwise.
170.Sh SEE ALSO
171.Xr ober_add_string 3 ,
172.Xr ober_oid_cmp 3 ,
173.Xr ober_read_elements 3 ,
174.Xr ober_set_header 3
175.Sh STANDARDS
176ITU-T Recommendation X.690, also known as ISO/IEC 8825-1:
177Information technology - ASN.1 encoding rules.
178.Sh HISTORY
179These functions first appeared as internal functions in
180.Xr snmpd 8
181in
182.Ox 4.2
183and were moved to libutil in
184.Ox 6.6 .
185.Sh AUTHORS
186.An -nosplit
187The BER library was written by
188.An Claudio Jeker Aq Mt claudio@openbsd.org ,
189.An Marc Balmer Aq Mt marc@openbsd.org
190and
191.An Reyk Floeter Aq Mt reyk@openbsd.org .