xref: /openssl/doc/man3/X509_ATTRIBUTE.pod (revision b6461792) 
1=pod
2
3=head1 NAME
4
5X509_ATTRIBUTE, X509at_get_attr,
6X509at_get_attr_count, X509at_get_attr_by_NID, X509at_get_attr_by_OBJ,
7X509at_delete_attr,
8X509at_add1_attr,
9X509at_add1_attr_by_OBJ, X509at_add1_attr_by_NID, X509at_add1_attr_by_txt,
10X509at_get0_data_by_OBJ,
11X509_ATTRIBUTE_create, X509_ATTRIBUTE_create_by_NID,
12X509_ATTRIBUTE_create_by_OBJ, X509_ATTRIBUTE_create_by_txt,
13X509_ATTRIBUTE_set1_object, X509_ATTRIBUTE_set1_data,
14X509_ATTRIBUTE_count,
15X509_ATTRIBUTE_get0_data, X509_ATTRIBUTE_get0_object, X509_ATTRIBUTE_get0_type
16- X509 attribute functions
17
18=head1 SYNOPSIS
19
20 #include <openssl/x509.h>
21
22 typedef struct x509_attributes_st X509_ATTRIBUTE;
23
24 int X509at_get_attr_count(const STACK_OF(X509_ATTRIBUTE) *x);
25 int X509at_get_attr_by_NID(const STACK_OF(X509_ATTRIBUTE) *x, int nid,
26                            int lastpos);
27 int X509at_get_attr_by_OBJ(const STACK_OF(X509_ATTRIBUTE) *sk,
28                            const ASN1_OBJECT *obj, int lastpos);
29 X509_ATTRIBUTE *X509at_get_attr(const STACK_OF(X509_ATTRIBUTE) *x, int loc);
30 X509_ATTRIBUTE *X509at_delete_attr(STACK_OF(X509_ATTRIBUTE) *x, int loc);
31 STACK_OF(X509_ATTRIBUTE) *X509at_add1_attr(STACK_OF(X509_ATTRIBUTE) **x,
32                                            X509_ATTRIBUTE *attr);
33 STACK_OF(X509_ATTRIBUTE) *X509at_add1_attr_by_OBJ(STACK_OF(X509_ATTRIBUTE)
34                                                   **x, const ASN1_OBJECT *obj,
35                                                   int type,
36                                                   const unsigned char *bytes,
37                                                   int len);
38 STACK_OF(X509_ATTRIBUTE) *X509at_add1_attr_by_NID(STACK_OF(X509_ATTRIBUTE)
39                                                   **x, int nid, int type,
40                                                   const unsigned char *bytes,
41                                                   int len);
42 STACK_OF(X509_ATTRIBUTE) *X509at_add1_attr_by_txt(STACK_OF(X509_ATTRIBUTE)
43                                                   **x, const char *attrname,
44                                                   int type,
45                                                   const unsigned char *bytes,
46                                                   int len);
47 void *X509at_get0_data_by_OBJ(const STACK_OF(X509_ATTRIBUTE) *x,
48                               const ASN1_OBJECT *obj, int lastpos, int type);
49 X509_ATTRIBUTE *X509_ATTRIBUTE_create(int nid, int atrtype, void *value);
50 X509_ATTRIBUTE *X509_ATTRIBUTE_create_by_NID(X509_ATTRIBUTE **attr, int nid,
51                                              int atrtype, const void *data,
52                                              int len);
53 X509_ATTRIBUTE *X509_ATTRIBUTE_create_by_OBJ(X509_ATTRIBUTE **attr,
54                                              const ASN1_OBJECT *obj,
55                                              int atrtype, const void *data,
56                                              int len);
57 X509_ATTRIBUTE *X509_ATTRIBUTE_create_by_txt(X509_ATTRIBUTE **attr,
58                                              const char *atrname, int type,
59                                              const unsigned char *bytes,
60                                              int len);
61 int X509_ATTRIBUTE_set1_object(X509_ATTRIBUTE *attr, const ASN1_OBJECT *obj);
62 int X509_ATTRIBUTE_set1_data(X509_ATTRIBUTE *attr, int attrtype,
63                              const void *data, int len);
64 void *X509_ATTRIBUTE_get0_data(X509_ATTRIBUTE *attr, int idx, int atrtype,
65                                void *data);
66 int X509_ATTRIBUTE_count(const X509_ATTRIBUTE *attr);
67 ASN1_OBJECT *X509_ATTRIBUTE_get0_object(X509_ATTRIBUTE *attr);
68 ASN1_TYPE *X509_ATTRIBUTE_get0_type(X509_ATTRIBUTE *attr, int idx);
69
70=head1 DESCRIPTION
71
72B<X509_ATTRIBUTE> objects are used by many standards including X509, X509_REQ,
73PKCS12, PKCS8, PKCS7 and CMS.
74
75The B<X509_ATTRIBUTE> object is used to represent the ASN.1 Attribute as defined
76in RFC 5280, i.e.
77
78 Attribute ::= SEQUENCE {
79   type             AttributeType,
80   values    SET OF AttributeValue }
81
82 AttributeType ::= OBJECT IDENTIFIER
83 AttributeValue ::= ANY -- DEFINED BY AttributeType
84
85For example CMS defines the signing-time attribute as:
86
87  id-signingTime OBJECT IDENTIFIER ::= { iso(1) member-body(2)
88      us(840) rsadsi(113549) pkcs(1) pkcs9(9) 5 }
89
90  SigningTime ::= Time
91
92  Time ::= CHOICE {
93    utcTime UTCTime,
94    generalizedTime GeneralizedTime }
95
96In OpenSSL B<AttributeType> maps to an B<ASN1_OBJECT> object
97and B<AttributeValue> maps to a list of B<ASN1_TYPE> objects.
98
99The following functions are used for B<X509_ATTRIBUTE> objects.
100
101X509at_get_attr_by_OBJ() finds the location of the first matching object I<obj>
102in a list of attributes I<sk>. The search starts at the position after I<lastpos>.
103If the returned value is positive then it can be used on the next call to
104X509at_get_attr_by_OBJ() as the value of I<lastpos> in order to iterate through
105the remaining attributes. I<lastpos> can be set to any negative value on the
106first call, in order to start searching from the start of the list.
107
108X509at_get_attr_by_NID() is similar to X509at_get_attr_by_OBJ() except that it
109passes the numerical identifier (NID) I<nid> associated with the object.
110See <openssl/obj_mac.h> for a list of NID_*.
111
112X509at_get_attr() returns the B<X509_ATTRIBUTE> object at index I<loc> in the
113list of attributes I<x>. I<loc> should be in the range from 0 to
114X509at_get_attr_count() - 1.
115
116X509at_delete_attr() removes the B<X509_ATTRIBUTE> object at index I<loc> in
117the list of attributes I<x>.
118
119X509at_add1_attr() pushes a copy of the passed in B<X509_ATTRIBUTE> object
120to the list I<x>.
121Both I<x> and I<attr> must be non NULL or an error will occur.
122If I<*x> is NULL then a new list is created, otherwise it uses the
123passed in list. An error will occur if an existing attribute (with the same
124attribute type) already exists in the attribute list.
125
126X509at_add1_attr_by_OBJ() creates a new B<X509_ATTRIBUTE> using
127X509_ATTRIBUTE_set1_object() and X509_ATTRIBUTE_set1_data() to assign a new
128I<obj> with type I<type> and data I<bytes> of length I<len> and then pushes it
129to the attribute list I<x>. Both I<x> and I<attr> must be non NULL or an error
130will occur. If I<*x> is NULL then a new attribute list is created. If I<obj>
131already exists in the attribute list then an error occurs.
132
133X509at_add1_attr_by_NID() is similar to X509at_add1_attr_by_OBJ() except that it
134passes the numerical identifier (NID) I<nid> associated with the object.
135See <openssl/obj_mac.h> for a list of NID_*.
136
137X509at_add1_attr_by_txt() is similar to X509at_add1_attr_by_OBJ() except that it
138passes a name I<attrname> associated with the object.
139See <openssl/obj_mac.h> for a list of SN_* names.
140
141X509_ATTRIBUTE_set1_object() assigns a B<ASN1_OBJECT> I<obj>
142to the attribute I<attr>. If I<attr> contained an existing B<ASN1_OBJECT> then
143it is freed. An error occurs if either I<attr> or I<obj> are NULL, or if
144the passed in I<obj> cannot be duplicated.
145
146X509_ATTRIBUTE_set1_data() pushes a new B<ASN1_TYPE> object onto the I<attr>
147attributes list. The new object is assigned a copy of the data in I<data> of
148size I<len>.
149If I<attrtype> has flag I<MBSTRING_FLAG> set then a table lookup using the
150I<attr> attributes NID is used to set an B<ASN1_STRING> using
151ASN1_STRING_set_by_NID(), and the passed in I<data> must be in the format
152required for that object type or an error will occur.
153If I<len> is not -1 then internally ASN1_STRING_type_new() is
154used with the passed in I<attrtype>.
155If I<attrtype> is 0 the call does nothing except return 1.
156
157X509_ATTRIBUTE_create() creates a new B<X509_ATTRIBUTE> using the I<nid>
158to set the B<ASN1_OBJECT> OID and the I<atrtype> and I<value> to set the
159B<ASN1_TYPE>.
160
161X509_ATTRIBUTE_create_by_OBJ() uses X509_ATTRIBUTE_set1_object() and
162X509_ATTRIBUTE_set1_data() to assign a new I<obj> with type I<atrtype> and
163data I<data> of length I<len>. If the passed in attribute I<attr> OR I<*attr> is
164NULL then a new B<X509_ATTRIBUTE> will be returned, otherwise the passed in
165B<X509_ATTRIBUTE> is used. Note that the ASN1_OBJECT I<obj> is pushed onto the
166attributes existing list of objects, which could be an issue if the attributes
167<ASN1_OBJECT> was different.
168
169X509_ATTRIBUTE_create_by_NID() is similar to X509_ATTRIBUTE_create_by_OBJ()
170except that it passes the numerical identifier (NID) I<nid> associated with the
171object. See <openssl/obj_mac.h> for a list of NID_*.
172
173X509_ATTRIBUTE_create_by_txt() is similar to X509_ATTRIBUTE_create_by_OBJ()
174except that it passes a name I<atrname> associated with the
175object. See <openssl/obj_mac.h> for a list of SN_* names.
176
177X509_ATTRIBUTE_count() returns the number of B<ASN1_TYPE> objects in an
178attribute I<attr>.
179
180X509_ATTRIBUTE_get0_type() returns the B<ASN1_TYPE> object at index I<idx> in
181the attribute list I<attr>. I<idx> should be in the
182range of 0 to X509_ATTRIBUTE_count() - 1 or an error will occur.
183
184X509_ATTRIBUTE_get0_data() returns the data of an B<ASN1_TYPE> object at
185index I<idx> in the attribute I<attr>. I<data> is unused and can be set to NULL.
186An error will occur if the attribute type I<atrtype> does not match the type of
187the B<ASN1_TYPE> object at index I<idx> OR if I<atrtype> is either
188B<V_ASN1_BOOLEAN> or B<V_ASN1_NULL> OR if the I<idx> is not in the
189range 0 to X509_ATTRIBUTE_count() - 1.
190
191X509at_get0_data_by_OBJ() finds the first attribute in an attribute list I<x>
192that matches the I<obj> starting at index I<lastpos> and returns the data
193retrieved from the found attributes first B<ASN1_TYPE> object. An error will
194occur if the attribute type I<type> does not match the type of the B<ASN1_TYPE>
195object OR if I<type> is either B<V_ASN1_BOOLEAN> or B<V_ASN1_NULL> OR the
196attribute is not found.
197If I<lastpos> is less than -1 then an error will occur if there are multiple
198objects in the list I<x> that match I<obj>.
199If I<lastpos> is less than -2 then an error will occur if there is more than
200one B<ASN1_TYPE> object in the found attribute.
201
202=head1 RETURN VALUES
203
204X509at_get_attr_count() returns the number of attributes in the list I<x> or -1
205if I<x> is NULL.
206
207X509at_get_attr_by_OBJ() returns -1 if either the list is empty OR the object
208is not found, otherwise it returns the location of the object in the list.
209
210X509at_get_attr_by_NID() is similar to X509at_get_attr_by_OBJ(), except that
211it returns -2 if the I<nid> is not known by OpenSSL.
212
213X509at_get_attr() returns either an B<X509_ATTRIBUTE> or NULL if there is a error.
214
215X509at_delete_attr() returns either the removed B<X509_ATTRIBUTE> or NULL if
216there is a error.
217
218X509_ATTRIBUTE_count() returns -1 on error, otherwise it returns the number
219of B<ASN1_TYPE> elements.
220
221X509_ATTRIBUTE_get0_type() returns NULL on error, otherwise it returns a
222B<ASN1_TYPE> object.
223
224X509_ATTRIBUTE_get0_data() returns NULL if an error occurs,
225otherwise it returns the data associated with an B<ASN1_TYPE> object.
226
227X509_ATTRIBUTE_set1_object() and X509_ATTRIBUTE_set1_data() returns 1 on
228success, or 0 otherwise.
229
230X509_ATTRIBUTE_create(), X509_ATTRIBUTE_create_by_OBJ(),
231X509_ATTRIBUTE_create_by_NID() and X509_ATTRIBUTE_create_by_txt() return either
232a B<X509_ATTRIBUTE> on success, or NULL if there is a error.
233
234X509at_add1_attr(), X509at_add1_attr_by_OBJ(), X509at_add1_attr_by_NID() and
235X509at_add1_attr_by_txt() return NULL on error, otherwise they return a list
236of B<X509_ATTRIBUTE>.
237
238X509at_get0_data_by_OBJ() returns the data retrieved from the found attributes
239first B<ASN1_TYPE> object, or NULL if an error occurs.
240
241=head1 SEE ALSO
242
243L<ASN1_TYPE_get(3)>,
244L<ASN1_INTEGER_get(3)>,
245L<ASN1_ENUMERATED_get(3)>,
246L<ASN1_STRING_get0_data(3)>,
247L<ASN1_STRING_length(3)>,
248L<ASN1_STRING_type(3)>,
249L<X509_REQ_get_attr(3)>,
250L<EVP_PKEY_get_attr(3)>,
251L<CMS_signed_get_attr(3)>,
252L<PKCS8_pkey_get0_attrs(3)>,
253
254=head1 COPYRIGHT
255
256Copyright 2023-2024 The OpenSSL Project Authors. All Rights Reserved.
257
258Licensed under the Apache License 2.0 (the "License").  You may not use
259this file except in compliance with the License.  You can obtain a copy
260in the file LICENSE in the source distribution or at
261L<https://www.openssl.org/source/license.html>.
262
263=cut
264