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, OBJ_add_sigid
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
38 int OBJ_add_sigid(int signid, int dig_id, int pkey_id);
39
40Deprecated since OpenSSL 1.1.0, can be hidden entirely by defining
41B<OPENSSL_API_COMPAT> with a suitable version value, see
42L<openssl_user_macros(7)>:
43
44 void OBJ_cleanup(void);
45
46=head1 DESCRIPTION
47
48The ASN1 object utility functions process ASN1_OBJECT structures which are
49a representation of the ASN1 OBJECT IDENTIFIER (OID) type.
50For convenience, OIDs are usually represented in source code as numeric
51identifiers, or B<NID>s.  OpenSSL has an internal table of OIDs that
52are generated when the library is built, and their corresponding NIDs
53are available as defined constants.  For the functions below, application
54code should treat all returned values -- OIDs, NIDs, or names -- as
55constants.
56
57OBJ_nid2obj(), OBJ_nid2ln() and OBJ_nid2sn() convert the NID I<n> to
58an ASN1_OBJECT structure, its long name and its short name respectively,
59or B<NULL> if an error occurred.
60
61OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() return the corresponding NID
62for the object I<o>, the long name I<ln> or the short name I<sn> respectively
63or NID_undef if an error occurred.
64
65OBJ_txt2nid() returns NID corresponding to text string I<s>. I<s> can be
66a long name, a short name or the numerical representation of an object.
67
68OBJ_txt2obj() converts the text string I<s> into an ASN1_OBJECT structure.
69If I<no_name> is 0 then long names and short names will be interpreted
70as well as numerical forms. If I<no_name> is 1 only the numerical form
71is acceptable.
72
73OBJ_obj2txt() converts the B<ASN1_OBJECT> I<a> into a textual representation.
74The representation is written as a null terminated string to I<buf>
75at most I<buf_len> bytes are written, truncating the result if necessary.
76The total amount of space required is returned. If I<no_name> is 0 then
77if the object has a long or short name then that will be used, otherwise
78the numerical form will be used. If I<no_name> is 1 then the numerical
79form will always be used.
80
81i2t_ASN1_OBJECT() is the same as OBJ_obj2txt() with the I<no_name> set to zero.
82
83OBJ_cmp() compares I<a> to I<b>. If the two are identical 0 is returned.
84
85OBJ_dup() returns a copy of I<o>.
86
87OBJ_create() adds a new object to the internal table. I<oid> is the
88numerical form of the object, I<sn> the short name and I<ln> the
89long name. A new NID is returned for the created object in case of
90success and NID_undef in case of failure.
91
92OBJ_length() returns the size of the content octets of I<obj>.
93
94OBJ_get0_data() returns a pointer to the content octets of I<obj>.
95The returned pointer is an internal pointer which B<must not> be freed.
96
97OBJ_add_sigid() creates a new composite "Signature Algorithm" that associates a
98given NID with two other NIDs - one representing the underlying signature
99algorithm and the other representing a digest algorithm to be used in
100conjunction with it. I<signid> represents the NID for the composite "Signature
101Algorithm", I<dig_id> is the NID for the digest algorithm and I<pkey_id> is the
102NID for the underlying signature algorithm.
103
104OBJ_cleanup() releases any resources allocated by creating new objects.
105
106=head1 NOTES
107
108Objects in OpenSSL can have a short name, a long name and a numerical
109identifier (NID) associated with them. A standard set of objects is
110represented in an internal table. The appropriate values are defined
111in the header file B<objects.h>.
112
113For example the OID for commonName has the following definitions:
114
115 #define SN_commonName                   "CN"
116 #define LN_commonName                   "commonName"
117 #define NID_commonName                  13
118
119New objects can be added by calling OBJ_create().
120
121Table objects have certain advantages over other objects: for example
122their NIDs can be used in a C language switch statement. They are
123also static constant structures which are shared: that is there
124is only a single constant structure for each table object.
125
126Objects which are not in the table have the NID value NID_undef.
127
128Objects do not need to be in the internal tables to be processed,
129the functions OBJ_txt2obj() and OBJ_obj2txt() can process the numerical
130form of an OID.
131
132Some objects are used to represent algorithms which do not have a
133corresponding ASN.1 OBJECT IDENTIFIER encoding (for example no OID currently
134exists for a particular algorithm). As a result they B<cannot> be encoded or
135decoded as part of ASN.1 structures. Applications can determine if there
136is a corresponding OBJECT IDENTIFIER by checking OBJ_length() is not zero.
137
138These functions cannot return B<const> because an B<ASN1_OBJECT> can
139represent both an internal, constant, OID and a dynamically-created one.
140The latter cannot be constant because it needs to be freed after use.
141
142=head1 RETURN VALUES
143
144OBJ_nid2obj() returns an B<ASN1_OBJECT> structure or B<NULL> is an
145error occurred.
146
147OBJ_nid2ln() and OBJ_nid2sn() returns a valid string or B<NULL>
148on error.
149
150OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() and OBJ_txt2nid() return
151a NID or B<NID_undef> on error.
152
153OBJ_add_sigid() returns 1 on success or 0 on error.
154
155=head1 EXAMPLES
156
157Create an object for B<commonName>:
158
159 ASN1_OBJECT *o = OBJ_nid2obj(NID_commonName);
160
161Check if an object is B<commonName>
162
163 if (OBJ_obj2nid(obj) == NID_commonName)
164     /* Do something */
165
166Create a new NID and initialize an object from it:
167
168 int new_nid = OBJ_create("1.2.3.4", "NewOID", "New Object Identifier");
169 ASN1_OBJECT *obj = OBJ_nid2obj(new_nid);
170
171Create a new object directly:
172
173 obj = OBJ_txt2obj("1.2.3.4", 1);
174
175=head1 BUGS
176
177OBJ_obj2txt() is awkward and messy to use: it doesn't follow the
178convention of other OpenSSL functions where the buffer can be set
179to B<NULL> to determine the amount of data that should be written.
180Instead I<buf> must point to a valid buffer and I<buf_len> should
181be set to a positive value. A buffer length of 80 should be more
182than enough to handle any OID encountered in practice.
183
184Neither OBJ_create() nor OBJ_add_sigid() do any locking and are thus not
185thread safe.  Moreover, none of the other functions should be called while
186concurrent calls to these two functions are possible.
187
188=head1 SEE ALSO
189
190L<ERR_get_error(3)>
191
192=head1 HISTORY
193
194OBJ_cleanup() was deprecated in OpenSSL 1.1.0 by L<OPENSSL_init_crypto(3)>
195and should not be used.
196
197=head1 COPYRIGHT
198
199Copyright 2002-2021 The OpenSSL Project Authors. All Rights Reserved.
200
201Licensed under the Apache License 2.0 (the "License").  You may not use
202this file except in compliance with the License.  You can obtain a copy
203in the file LICENSE in the source distribution or at
204L<https://www.openssl.org/source/license.html>.
205
206=cut
207