1CRYPTO_GET_EX_NEW_INDEX(3) OpenSSL CRYPTO_GET_EX_NEW_INDEX(3)
2
6 CRYPTO_EX_new, CRYPTO_EX_free, CRYPTO_EX_dup, CRYPTO_free_ex_index,
7 CRYPTO_get_ex_new_index, CRYPTO_set_ex_data, CRYPTO_get_ex_data,
8 CRYPTO_free_ex_data, CRYPTO_new_ex_data - functions supporting
9 application-specific data
10
12 #include <openssl/crypto.h>
13 int CRYPTO_get_ex_new_index(int class_index,
15 long argl, void *argp,
16 CRYPTO_EX_new *new_func,
17 CRYPTO_EX_dup *dup_func,
18 CRYPTO_EX_free *free_func);
19 typedef void CRYPTO_EX_new(void *parent, void *ptr, CRYPTO_EX_DATA *ad,
21 int idx, long argl, void *argp);
22 typedef void CRYPTO_EX_free(void *parent, void *ptr, CRYPTO_EX_DATA *ad,
23 int idx, long argl, void *argp);
24 typedef int CRYPTO_EX_dup(CRYPTO_EX_DATA *to, const CRYPTO_EX_DATA *from,
25 void *from_d, int idx, long argl, void *argp);
26 int CRYPTO_new_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *ad)
28 int CRYPTO_set_ex_data(CRYPTO_EX_DATA *r, int idx, void *arg);
30 void *CRYPTO_get_ex_data(CRYPTO_EX_DATA *r, int idx);
32 void CRYPTO_free_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *r);
34 int CRYPTO_free_ex_index(int class_index, int idx);
36
38 Several OpenSSL structures can have application-specific data attached
39 to them, known as "exdata." The specific structures are:
40 APP
42 BIO
43 DH
44 DRBG
45 DSA
46 EC_KEY
47 ENGINE
48 RSA
49 SSL
50 SSL_CTX
51 SSL_SESSION
52 UI
53 UI_METHOD
54 X509
55 X509_STORE
56 X509_STORE_CTX
57 Each is identified by an CRYPTO_EX_INDEX_xxx define in the crypto.h
59 header file. In addition, CRYPTO_EX_INDEX_APP is reserved for
60 applications to use this facility for their own structures.
61 The API described here is used by OpenSSL to manipulate exdata for
63 specific structures. Since the application data can be anything at all
64 it is passed and retrieved as a void * type.
65 The CRYPTO_EX_DATA type is opaque. To initialize the exdata part of a
67 structure, call CRYPTO_new_ex_data(). This is only necessary for
68 CRYPTO_EX_INDEX_APP objects.
69 Exdata types are identified by an index, an integer guaranteed to be
71 unique within structures for the lifetime of the program. Applications
72 using exdata typically call CRYPTO_get_ex_new_index at startup, and
73 store the result in a global variable, or write a wrapper function to
74 provide lazy evaluation. The class_index should be one of the
75 CRYPTO_EX_INDEX_xxx values. The argl and argp parameters are saved to
76 be passed to the callbacks but are otherwise not used. In order to
77 transparently manipulate exdata, three callbacks must be provided. The
78 semantics of those callbacks are described below.
79 When copying or releasing objects with exdata, the callback functions
81 are called in increasing order of their index value.
82 If a dynamic library can be unloaded, it should call
84 CRYPTO_free_ex_index() when this is done. This will replace the
85 callbacks with no-ops so that applications don't crash. Any existing
86 exdata will be leaked.
87 To set or get the exdata on an object, the appropriate type-specific
89 routine must be used. This is because the containing structure is
90 opaque and the CRYPTO_EX_DATA field is not accessible. In both API's,
91 the idx parameter should be an already-created index value.
92 When setting exdata, the pointer specified with a particular index is
94 saved, and returned on a subsequent "get" call. If the application is
95 going to release the data, it must make sure to set a NULL value at the
96 index, to avoid likely double-free crashes.
97 The function CRYPTO_free_ex_data is used to free all exdata attached to
99 a structure. The appropriate type-specific routine must be used. The
100 class_index identifies the structure type, the obj is be the pointer to
101 the actual structure, and r is a pointer to the structure's exdata
102 field.
103 Callback Functions
105 This section describes how the callback functions are used.
106 Applications that are defining their own exdata using
107 CYPRTO_EX_INDEX_APP must call them as described here.
108 When a structure is initially allocated (such as RSA_new()) then the
110 new_func() is called for every defined index. There is no requirement
111 that the entire parent, or containing, structure has been set up. The
112 new_func() is typically used only to allocate memory to store the
113 exdata, and perhaps an "initialized" flag within that memory. The
114 exdata value should be set by calling CRYPTO_set_ex_data().
115 When a structure is free'd (such as SSL_CTX_free()) then the
117 free_func() is called for every defined index. Again, the state of the
118 parent structure is not guaranteed. The free_func() may be called with
119 a NULL pointer.
120 Both new_func() and free_func() take the same parameters. The parent
122 is the pointer to the structure that contains the exdata. The ptr is
123 the current exdata item; for new_func() this will typically be NULL.
124 The r parameter is a pointer to the exdata field of the object. The
125 idx is the index and is the value returned when the callbacks were
126 initially registered via CRYPTO_get_ex_new_index() and can be used if
127 the same callback handles different types of exdata.
128 dup_func() is called when a structure is being copied. This is only
130 done for SSL, SSL_SESSION, EC_KEY objects and BIO chains via
131 BIO_dup_chain(). The to and from parameters are pointers to the
132 destination and source CRYPTO_EX_DATA structures, respectively. The
133 from_d parameter needs to be cast to a void **pptr as the API has
134 currently the wrong signature; that will be changed in a future
135 version. The *pptr is a pointer to the source exdata. When the
136 dup_func() returns, the value in *pptr is copied to the destination
137 ex_data. If the pointer contained in *pptr is not modified by the
138 dup_func(), then both to and from will point to the same data. The
139 idx, argl and argp parameters are as described for the other two
140 callbacks. If the dup_func() returns 0 the whole CRYPTO_dup_ex_data()
141 will fail.
142
144 CRYPTO_get_ex_new_index() returns a new index or -1 on failure.
145 CRYPTO_free_ex_index() and CRYPTO_set_ex_data() return 1 on success or
147 0 on failure.
148 CRYPTO_get_ex_data() returns the application data or NULL on failure;
150 note that NULL may be a valid value.
151 dup_func() should return 0 for failure and 1 for success.
153
155 Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.
156 Licensed under the OpenSSL license (the "License"). You may not use
158 this file except in compliance with the License. You can obtain a copy
159 in the file LICENSE in the source distribution or at
160 <https://www.openssl.org/source/license.html>.
1611.1.1 2018-09-11 CRYPTO_GET_EX_NEW_INDEX(3)