1=pod
2
3=head1 NAME
4
5i2t_ASN1_OBJECT,
6OBJ_length, OBJ_get0_data, OBJ_nid2obj, OBJ_nid2ln,
7OBJ_nid2sn, OBJ_obj2nid, OBJ_txt2nid, OBJ_ln2nid, OBJ_sn2nid, OBJ_cmp,
8OBJ_dup, OBJ_txt2obj, OBJ_obj2txt, OBJ_create, OBJ_cleanup
9- ASN1 object utility functions
10
11=head1 SYNOPSIS
12
13 #include <openssl/objects.h>
14
15 ASN1_OBJECT *OBJ_nid2obj(int n);
16 const char *OBJ_nid2ln(int n);
17 const char *OBJ_nid2sn(int n);
18
19 int OBJ_obj2nid(const ASN1_OBJECT *o);
20 int OBJ_ln2nid(const char *ln);
21 int OBJ_sn2nid(const char *sn);
22
23 int OBJ_txt2nid(const char *s);
24
25 ASN1_OBJECT *OBJ_txt2obj(const char *s, int no_name);
26 int OBJ_obj2txt(char *buf, int buf_len, const ASN1_OBJECT *a, int no_name);
27
28 int i2t_ASN1_OBJECT(char *buf, int buf_len, const ASN1_OBJECT *a);
29
30 int OBJ_cmp(const ASN1_OBJECT *a, const ASN1_OBJECT *b);
31 ASN1_OBJECT *OBJ_dup(const ASN1_OBJECT *o);
32
33 int OBJ_create(const char *oid, const char *sn, const char *ln);
34
35 size_t OBJ_length(const ASN1_OBJECT *obj);
36 const unsigned char *OBJ_get0_data(const ASN1_OBJECT *obj);
37
38Deprecated:
39
40 #if OPENSSL_API_COMPAT < 0x10100000L
41 void OBJ_cleanup(void)
42 #endif
43
44=head1 DESCRIPTION
45
46The ASN1 object utility functions process ASN1_OBJECT structures which are
47a representation of the ASN1 OBJECT IDENTIFIER (OID) type.
48For convenience, OIDs are usually represented in source code as numeric
49identifiers, or B<NID>s.  OpenSSL has an internal table of OIDs that
50are generated when the library is built, and their corresponding NIDs
51are available as defined constants.  For the functions below, application
52code should treat all returned values -- OIDs, NIDs, or names -- as
53constants.
54
55OBJ_nid2obj(), OBJ_nid2ln() and OBJ_nid2sn() convert the NID B<n> to
56an ASN1_OBJECT structure, its long name and its short name respectively,
57or B<NULL> if an error occurred.
58
59OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() return the corresponding NID
60for the object B<o>, the long name <ln> or the short name <sn> respectively
61or NID_undef if an error occurred.
62
63OBJ_txt2nid() returns NID corresponding to text string <s>. B<s> can be
64a long name, a short name or the numerical representation of an object.
65
66OBJ_txt2obj() converts the text string B<s> into an ASN1_OBJECT structure.
67If B<no_name> is 0 then long names and short names will be interpreted
68as well as numerical forms. If B<no_name> is 1 only the numerical form
69is acceptable.
70
71OBJ_obj2txt() converts the B<ASN1_OBJECT> B<a> into a textual representation.
72The representation is written as a null terminated string to B<buf>
73at most B<buf_len> bytes are written, truncating the result if necessary.
74The total amount of space required is returned. If B<no_name> is 0 then
75if the object has a long or short name then that will be used, otherwise
76the numerical form will be used. If B<no_name> is 1 then the numerical
77form will always be used.
78
79i2t_ASN1_OBJECT() is the same as OBJ_obj2txt() with the B<no_name> set to zero.
80
81OBJ_cmp() compares B<a> to B<b>. If the two are identical 0 is returned.
82
83OBJ_dup() returns a copy of B<o>.
84
85OBJ_create() adds a new object to the internal table. B<oid> is the
86numerical form of the object, B<sn> the short name and B<ln> the
87long name. A new NID is returned for the created object in case of
88success and NID_undef in case of failure.
89
90OBJ_length() returns the size of the content octets of B<obj>.
91
92OBJ_get0_data() returns a pointer to the content octets of B<obj>.
93The returned pointer is an internal pointer which B<must not> be freed.
94
95OBJ_cleanup() releases any resources allocated by creating new objects.
96
97=head1 NOTES
98
99Objects in OpenSSL can have a short name, a long name and a numerical
100identifier (NID) associated with them. A standard set of objects is
101represented in an internal table. The appropriate values are defined
102in the header file B<objects.h>.
103
104For example the OID for commonName has the following definitions:
105
106 #define SN_commonName                   "CN"
107 #define LN_commonName                   "commonName"
108 #define NID_commonName                  13
109
110New objects can be added by calling OBJ_create().
111
112Table objects have certain advantages over other objects: for example
113their NIDs can be used in a C language switch statement. They are
114also static constant structures which are shared: that is there
115is only a single constant structure for each table object.
116
117Objects which are not in the table have the NID value NID_undef.
118
119Objects do not need to be in the internal tables to be processed,
120the functions OBJ_txt2obj() and OBJ_obj2txt() can process the numerical
121form of an OID.
122
123Some objects are used to represent algorithms which do not have a
124corresponding ASN.1 OBJECT IDENTIFIER encoding (for example no OID currently
125exists for a particular algorithm). As a result they B<cannot> be encoded or
126decoded as part of ASN.1 structures. Applications can determine if there
127is a corresponding OBJECT IDENTIFIER by checking OBJ_length() is not zero.
128
129These functions cannot return B<const> because an B<ASN1_OBJECT> can
130represent both an internal, constant, OID and a dynamically-created one.
131The latter cannot be constant because it needs to be freed after use.
132
133=head1 RETURN VALUES
134
135OBJ_nid2obj() returns an B<ASN1_OBJECT> structure or B<NULL> is an
136error occurred.
137
138OBJ_nid2ln() and OBJ_nid2sn() returns a valid string or B<NULL>
139on error.
140
141OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() and OBJ_txt2nid() return
142a NID or B<NID_undef> on error.
143
144=head1 EXAMPLES
145
146Create an object for B<commonName>:
147
148 ASN1_OBJECT *o = OBJ_nid2obj(NID_commonName);
149
150Check if an object is B<commonName>
151
152 if (OBJ_obj2nid(obj) == NID_commonName)
153     /* Do something */
154
155Create a new NID and initialize an object from it:
156
157 int new_nid = OBJ_create("1.2.3.4", "NewOID", "New Object Identifier");
158 ASN1_OBJECT *obj = OBJ_nid2obj(new_nid);
159
160Create a new object directly:
161
162 obj = OBJ_txt2obj("1.2.3.4", 1);
163
164=head1 BUGS
165
166OBJ_obj2txt() is awkward and messy to use: it doesn't follow the
167convention of other OpenSSL functions where the buffer can be set
168to B<NULL> to determine the amount of data that should be written.
169Instead B<buf> must point to a valid buffer and B<buf_len> should
170be set to a positive value. A buffer length of 80 should be more
171than enough to handle any OID encountered in practice.
172
173=head1 SEE ALSO
174
175L<ERR_get_error(3)>
176
177=head1 HISTORY
178
179OBJ_cleanup() was deprecated in OpenSSL 1.1.0 by L<OPENSSL_init_crypto(3)>
180and should not be used.
181
182=head1 COPYRIGHT
183
184Copyright 2002-2019 The OpenSSL Project Authors. All Rights Reserved.
185
186Licensed under the OpenSSL license (the "License").  You may not use
187this file except in compliance with the License.  You can obtain a copy
188in the file LICENSE in the source distribution or at
189L<https://www.openssl.org/source/license.html>.
190
191=cut
192