1CRYPTO_GET_EX_NEW_INDEX(3ossl) OpenSSL CRYPTO_GET_EX_NEW_INDEX(3ossl)
2
6 CRYPTO_EX_new, CRYPTO_EX_free, CRYPTO_EX_dup, CRYPTO_free_ex_index,
7 CRYPTO_get_ex_new_index, CRYPTO_alloc_ex_data, CRYPTO_set_ex_data,
8 CRYPTO_get_ex_data, CRYPTO_free_ex_data, CRYPTO_new_ex_data - functions
9 supporting 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_alloc_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *ad,
30 int idx);
31 int CRYPTO_set_ex_data(CRYPTO_EX_DATA *r, int idx, void *arg);
33 void *CRYPTO_get_ex_data(const CRYPTO_EX_DATA *r, int idx);
35 void CRYPTO_free_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *r);
37 int CRYPTO_free_ex_index(int class_index, int idx);
39
41 Several OpenSSL structures can have application-specific data attached
42 to them, known as "exdata." The specific structures are:
43 BIO
45 DH
46 DSA
47 EC_KEY
48 ENGINE
49 EVP_PKEY
50 RSA
51 SSL
52 SSL_CTX
53 SSL_SESSION
54 UI
55 UI_METHOD
56 X509
57 X509_STORE
58 X509_STORE_CTX
59 In addition, the APP name is reserved for use by application code.
61 Each is identified by an CRYPTO_EX_INDEX_xxx define in the header file
63 <openssl/crypto.h>. In addition, CRYPTO_EX_INDEX_APP is reserved for
64 applications to use this facility for their own structures.
65 The API described here is used by OpenSSL to manipulate exdata for
67 specific structures. Since the application data can be anything at all
68 it is passed and retrieved as a void * type.
69 The CRYPTO_EX_DATA type is opaque. To initialize the exdata part of a
71 structure, call CRYPTO_new_ex_data(). This is only necessary for
72 CRYPTO_EX_INDEX_APP objects.
73 Exdata types are identified by an index, an integer guaranteed to be
75 unique within structures for the lifetime of the program. Applications
76 using exdata typically call CRYPTO_get_ex_new_index at startup, and
77 store the result in a global variable, or write a wrapper function to
78 provide lazy evaluation. The class_index should be one of the
79 CRYPTO_EX_INDEX_xxx values. The argl and argp parameters are saved to
80 be passed to the callbacks but are otherwise not used. In order to
81 transparently manipulate exdata, three callbacks must be provided. The
82 semantics of those callbacks are described below.
83 When copying or releasing objects with exdata, the callback functions
85 are called in increasing order of their index value.
86 If a dynamic library can be unloaded, it should call
88 CRYPTO_free_ex_index() when this is done. This will replace the
89 callbacks with no-ops so that applications don't crash. Any existing
90 exdata will be leaked.
91 To set or get the exdata on an object, the appropriate type-specific
93 routine must be used. This is because the containing structure is
94 opaque and the CRYPTO_EX_DATA field is not accessible. In both API's,
95 the idx parameter should be an already-created index value.
96 When setting exdata, the pointer specified with a particular index is
98 saved, and returned on a subsequent "get" call. If the application is
99 going to release the data, it must make sure to set a NULL value at the
100 index, to avoid likely double-free crashes.
101 The function CRYPTO_free_ex_data is used to free all exdata attached to
103 a structure. The appropriate type-specific routine must be used. The
104 class_index identifies the structure type, the obj is a pointer to the
105 actual structure, and r is a pointer to the structure's exdata field.
106 Callback Functions
108 This section describes how the callback functions are used.
109 Applications that are defining their own exdata using
110 CYPRTO_EX_INDEX_APP must call them as described here.
111 When a structure is initially allocated (such as RSA_new()) then the
113 new_func() is called for every defined index. There is no requirement
114 that the entire parent, or containing, structure has been set up. The
115 new_func() is typically used only to allocate memory to store the
116 exdata, and perhaps an "initialized" flag within that memory. The
117 exdata value may be allocated later on with CRYPTO_alloc_ex_data(), or
118 may be set by calling CRYPTO_set_ex_data().
119 When a structure is free'd (such as SSL_CTX_free()) then the
121 free_func() is called for every defined index. Again, the state of the
122 parent structure is not guaranteed. The free_func() may be called with
123 a NULL pointer.
124 Both new_func() and free_func() take the same parameters. The parent
126 is the pointer to the structure that contains the exdata. The ptr is
127 the current exdata item; for new_func() this will typically be NULL.
128 The r parameter is a pointer to the exdata field of the object. The
129 idx is the index and is the value returned when the callbacks were
130 initially registered via CRYPTO_get_ex_new_index() and can be used if
131 the same callback handles different types of exdata.
132 dup_func() is called when a structure is being copied. This is only
134 done for SSL, SSL_SESSION, EC_KEY objects and BIO chains via
135 BIO_dup_chain(). The to and from parameters are pointers to the
136 destination and source CRYPTO_EX_DATA structures, respectively. The
137 *from_d parameter is a pointer to the source exdata. When the
138 dup_func() returns, the value in *from_d is copied to the destination
139 ex_data. If the pointer contained in *pptr is not modified by the
140 dup_func(), then both to and from will point to the same data. The
141 idx, argl and argp parameters are as described for the other two
142 callbacks. If the dup_func() returns 0 the whole CRYPTO_dup_ex_data()
143 will fail.
144
146 CRYPTO_get_ex_new_index() returns a new index or -1 on failure.
147 CRYPTO_free_ex_index(), CRYPTO_alloc_ex_data() and CRYPTO_set_ex_data()
149 return 1 on success or 0 on failure.
150 CRYPTO_get_ex_data() returns the application data or NULL on failure;
152 note that NULL may be a valid value.
153 dup_func() should return 0 for failure and 1 for success.
155
157 CRYPTO_alloc_ex_data() was added in OpenSSL 3.0.
158 The signature of the dup_func() callback was changed in OpenSSL 3.0 to
160 use the type void ** for from_d. Previously this parameter was of type
161 void *.
162 Support for ENGINE "exdata" was deprecated in OpenSSL 3.0.
164
166 Copyright 2015-2021 The OpenSSL Project Authors. All Rights Reserved.
167 Licensed under the Apache License 2.0 (the "License"). You may not use
169 this file except in compliance with the License. You can obtain a copy
170 in the file LICENSE in the source distribution or at
171 <https://www.openssl.org/source/license.html>.
1723.1.1 2023-08-31 CRYPTO_GET_EX_NEW_INDEX(3ossl)