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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
5 | OSSL_METHOD_CONSTRUCT_METHOD, ossl_method_construct | |
6 | - generic method constructor | |
7 | ||
8 | =head1 SYNOPSIS | |
9 | ||
10 | #include "internal/core.h" | |
11 | ||
12 | struct ossl_method_construct_method_st { | |
13 | /* Create store */ | |
b4250010 | 14 | void *(*alloc_tmp_store)(OSSL_LIB_CTX *ctx); |
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15 | /* Remove a store */ |
16 | void (*dealloc_tmp_store)(void *store); | |
17 | /* Get an already existing method from a store */ | |
b4250010 | 18 | void *(*get)(OSSL_LIB_CTX *libctx, void *store, void *data); |
9e11fe0d | 19 | /* Store a method in a store */ |
b4250010 | 20 | int (*put)(OSSL_LIB_CTX *libctx, void *store, void *method, |
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21 | const OSSL_PROVIDER *prov, int operation_id, const char *name, |
22 | const char *propdef, void *data); | |
9e11fe0d | 23 | /* Construct a new method */ |
2e49c054 | 24 | void *(*construct)(const char *name, const OSSL_DISPATCH *fns, |
dc46e3dd | 25 | OSSL_PROVIDER *prov, void *data); |
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26 | /* Destruct a method */ |
27 | void (*destruct)(void *method); | |
28 | }; | |
29 | typedef struct ossl_method_construct_method OSSL_METHOD_CONSTRUCT_METHOD; | |
30 | ||
b4250010 | 31 | void *ossl_method_construct(OSSL_LIB_CTX *ctx, int operation_id, |
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32 | int force_cache, |
33 | OSSL_METHOD_CONSTRUCT_METHOD *mcm, void *mcm_data); | |
34 | ||
25b25b0f | 35 | |
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36 | =head1 DESCRIPTION |
37 | ||
490c8711 | 38 | All libcrypto subsystems that want to create their own methods based |
9e11fe0d | 39 | on provider dispatch tables need to do so in exactly the same way. |
490c8711 | 40 | ossl_method_construct() does this while leaving it to the subsystems |
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41 | to define more precisely how the methods are created, stored, etc. |
42 | ||
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43 | It's important to keep in mind that a method is identified by three things: |
44 | ||
45 | =over 4 | |
46 | ||
47 | =item The operation identity | |
48 | ||
49 | =item The name of the algorithm | |
50 | ||
51 | =item The properties associated with the algorithm implementation | |
52 | ||
53 | =back | |
54 | ||
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55 | =head2 Functions |
56 | ||
57 | ossl_method_construct() creates a method by asking all available | |
f7c16d48 | 58 | providers for a dispatch table given an I<operation_id>, and then |
490c8711 | 59 | calling the appropriate functions given by the subsystem specific |
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60 | method creator through I<mcm> and the data in I<mcm_data> (which is |
61 | passed by ossl_method_construct()). | |
9e11fe0d | 62 | |
490c8711 | 63 | This function assumes that the subsystem method creator implements |
a3830831 | 64 | reference counting and acts accordingly (i.e. it will call the |
490c8711 | 65 | subsystem destruct() method to decrement the reference count when |
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66 | appropriate). |
67 | ||
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68 | =head2 Structures |
69 | ||
490c8711 | 70 | A central part of constructing a subsystem specific method is to give |
9e11fe0d | 71 | ossl_method_construct a set of functions, all in the |
b4d3f203 | 72 | B<OSSL_METHOD_CONSTRUCT_METHOD> structure, which holds the following |
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73 | function pointers: |
74 | ||
75 | =over 4 | |
76 | ||
77 | =item alloc_tmp_store() | |
78 | ||
b4d3f203 | 79 | Create a temporary method store in the scope of the library context I<ctx>. |
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80 | This store is used to temporarily store methods for easier lookup, for |
81 | when the provider doesn't want its dispatch table stored in a longer | |
82 | term cache. | |
83 | ||
84 | =item dealloc_tmp_store() | |
85 | ||
86 | Remove a temporary store. | |
87 | ||
88 | =item get() | |
89 | ||
2e49c054 | 90 | Look up an already existing method from a store by name. |
9e11fe0d | 91 | |
b4d3f203 | 92 | The store may be given with I<store>. |
490c8711 | 93 | NULL is a valid value and means that a subsystem default store |
9e11fe0d | 94 | must be used. |
b4d3f203 | 95 | This default store should be stored in the library context I<libctx>. |
9e11fe0d | 96 | |
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97 | The method to be looked up should be identified with data found in I<data> |
98 | (which is the I<mcm_data> that was passed to ossl_construct_method()). | |
99 | In other words, the ossl_method_construct() caller is entirely responsible | |
100 | for ensuring the necesssary data is made available. | |
9e11fe0d | 101 | |
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102 | This function is expected to increment the method's reference count. |
103 | ||
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104 | =item put() |
105 | ||
b4d3f203 | 106 | Places the I<method> created by the construct() function (see below) |
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107 | in a store. |
108 | ||
b4d3f203 | 109 | The store may be given with I<store>. |
490c8711 | 110 | NULL is a valid value and means that a subsystem default store |
9e11fe0d | 111 | must be used. |
b4d3f203 | 112 | This default store should be stored in the library context I<libctx>. |
9e11fe0d | 113 | |
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114 | The method should be associated with the given I<operation_id>, |
115 | I<name> and property definition I<propdef> as well as any | |
116 | identification data given through I<data> (which is the I<mcm_data> | |
2ccb1b4e | 117 | that was passed to ossl_construct_method()). |
9e11fe0d | 118 | |
b4d3f203 | 119 | This function is expected to increment the I<method>'s reference count. |
a3830831 | 120 | |
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121 | =item construct() |
122 | ||
490c8711 | 123 | Constructs a subsystem method for the given I<name> and the given |
b4d3f203 | 124 | dispatch table I<fns>. |
9e11fe0d | 125 | |
b4d3f203 | 126 | The associated provider object I<prov> is passed as well, to make |
490c8711 | 127 | it possible for the subsystem constructor to keep a reference, which |
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128 | is recommended. |
129 | If such a reference is kept, the I<provider object> reference counter | |
7c95390e | 130 | must be incremented, using ossl_provider_up_ref(). |
9e11fe0d | 131 | |
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132 | This function is expected to set the method's reference count to 1. |
133 | ||
c2969ff6 | 134 | =item destruct() |
9e11fe0d | 135 | |
b4d3f203 | 136 | Decrement the I<method>'s reference count, and destruct it when |
a3830831 | 137 | the reference count reaches zero. |
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138 | |
139 | =back | |
140 | ||
141 | =head1 RETURN VALUES | |
142 | ||
143 | ossl_method_construct() returns a constructed method on success, or | |
dfabee82 | 144 | NULL on error. |
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145 | |
146 | =head1 HISTORY | |
147 | ||
2e49c054 | 148 | This functionality was added to OpenSSL 3.0. |
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149 | |
150 | =head1 COPYRIGHT | |
151 | ||
0f84cbc3 | 152 | Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved. |
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153 | |
154 | Licensed under the Apache License 2.0 (the "License"). You may not use this | |
155 | file except in compliance with the License. You can obtain a copy in the file | |
156 | LICENSE in the source distribution or at | |
157 | L<https://www.openssl.org/source/license.html>. | |
158 | ||
159 | =cut |