xref: /openssl/doc/man3/OBJ_nid2obj.pod (revision b79da97c) 
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
40The following function has been deprecated since OpenSSL 1.1.0, and can be
41hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
42see L<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.
74Unless I<buf> is NULL,
75the representation is written as a NUL-terminated string to I<buf>, where
76at most I<buf_len> bytes are written, truncating the result if necessary.
77In any case it returns the total string length, excluding the NUL character,
78required for non-truncated representation, or -1 on error.
79If I<no_name> is 0 then if the object has a long or short name
80then that will be used, otherwise the numerical form will be used.
81If I<no_name> is 1 then the numerical form will always be used.
82
83i2t_ASN1_OBJECT() is the same as OBJ_obj2txt() with the I<no_name> set to zero.
84
85OBJ_cmp() compares I<a> to I<b>. If the two are identical 0 is returned.
86
87OBJ_dup() returns a copy of I<o>.
88
89OBJ_create() adds a new object to the internal table. I<oid> is the
90numerical form of the object, I<sn> the short name and I<ln> the
91long name. A new NID is returned for the created object in case of
92success and NID_undef in case of failure.  Any of I<oid>, I<sn> and
93I<ln> may be NULL, but not all at once.
94
95OBJ_length() returns the size of the content octets of I<obj>.
96
97OBJ_get0_data() returns a pointer to the content octets of I<obj>.
98The returned pointer is an internal pointer which B<must not> be freed.
99
100OBJ_add_sigid() creates a new composite "Signature Algorithm" that associates a
101given NID with two other NIDs - one representing the underlying signature
102algorithm and the other representing a digest algorithm to be used in
103conjunction with it. I<signid> represents the NID for the composite "Signature
104Algorithm", I<dig_id> is the NID for the digest algorithm and I<pkey_id> is the
105NID for the underlying signature algorithm. As there are signature algorithms
106that do not require a digest, NID_undef is a valid I<dig_id>.
107
108OBJ_cleanup() releases any resources allocated by creating new objects.
109
110=head1 NOTES
111
112Objects in OpenSSL can have a short name, a long name and a numerical
113identifier (NID) associated with them. A standard set of objects is
114represented in an internal table. The appropriate values are defined
115in the header file B<objects.h>.
116
117For example the OID for commonName has the following definitions:
118
119 #define SN_commonName                   "CN"
120 #define LN_commonName                   "commonName"
121 #define NID_commonName                  13
122
123New objects can be added by calling OBJ_create().
124
125Table objects have certain advantages over other objects: for example
126their NIDs can be used in a C language switch statement. They are
127also static constant structures which are shared: that is there
128is only a single constant structure for each table object.
129
130Objects which are not in the table have the NID value NID_undef.
131
132Objects do not need to be in the internal tables to be processed,
133the functions OBJ_txt2obj() and OBJ_obj2txt() can process the numerical
134form of an OID.
135
136Some objects are used to represent algorithms which do not have a
137corresponding ASN.1 OBJECT IDENTIFIER encoding (for example no OID currently
138exists for a particular algorithm). As a result they B<cannot> be encoded or
139decoded as part of ASN.1 structures. Applications can determine if there
140is a corresponding OBJECT IDENTIFIER by checking OBJ_length() is not zero.
141
142These functions cannot return B<const> because an B<ASN1_OBJECT> can
143represent both an internal, constant, OID and a dynamically-created one.
144The latter cannot be constant because it needs to be freed after use.
145
146These functions were not thread safe in OpenSSL 3.0 and before.
147
148=head1 RETURN VALUES
149
150OBJ_nid2obj() returns an B<ASN1_OBJECT> structure or B<NULL> is an
151error occurred.
152
153OBJ_nid2ln() and OBJ_nid2sn() returns a valid string or B<NULL>
154on error.
155
156OBJ_obj2nid(), OBJ_ln2nid(), OBJ_sn2nid() and OBJ_txt2nid() return
157a NID or B<NID_undef> on error.
158
159OBJ_add_sigid() returns 1 on success or 0 on error.
160
161i2t_ASN1_OBJECT() an OBJ_obj2txt() return -1 on error.
162On success, they return the length of the string written to I<buf> if I<buf> is
163not NULL and I<buf_len> is big enough, otherwise the total string length.
164Note that this does not count the trailing NUL character.
165
166=head1 EXAMPLES
167
168Create an object for B<commonName>:
169
170 ASN1_OBJECT *o = OBJ_nid2obj(NID_commonName);
171
172Check if an object is B<commonName>
173
174 if (OBJ_obj2nid(obj) == NID_commonName)
175     /* Do something */
176
177Create a new NID and initialize an object from it:
178
179 int new_nid = OBJ_create("1.2.3.4", "NewOID", "New Object Identifier");
180 ASN1_OBJECT *obj = OBJ_nid2obj(new_nid);
181
182Create a new object directly:
183
184 obj = OBJ_txt2obj("1.2.3.4", 1);
185
186=head1 SEE ALSO
187
188L<ERR_get_error(3)>
189
190=head1 HISTORY
191
192OBJ_cleanup() was deprecated in OpenSSL 1.1.0 by L<OPENSSL_init_crypto(3)>
193and should not be used.
194
195=head1 COPYRIGHT
196
197Copyright 2002-2021 The OpenSSL Project Authors. All Rights Reserved.
198
199Licensed under the Apache License 2.0 (the "License").  You may not use
200this file except in compliance with the License.  You can obtain a copy
201in the file LICENSE in the source distribution or at
202L<https://www.openssl.org/source/license.html>.
203
204=cut
205