1ENGINE_ADD(3) OpenSSL ENGINE_ADD(3)
2
6 ENGINE_get_DH, ENGINE_get_DSA, ENGINE_by_id, ENGINE_get_cipher_engine,
7 ENGINE_get_default_DH, ENGINE_get_default_DSA, ENGINE_get_default_RAND,
8 ENGINE_get_default_RSA, ENGINE_get_digest_engine, ENGINE_get_first,
9 ENGINE_get_last, ENGINE_get_next, ENGINE_get_prev, ENGINE_new,
10 ENGINE_get_ciphers, ENGINE_get_ctrl_function, ENGINE_get_digests,
11 ENGINE_get_destroy_function, ENGINE_get_finish_function,
12 ENGINE_get_init_function, ENGINE_get_load_privkey_function,
13 ENGINE_get_load_pubkey_function, ENGINE_load_private_key,
14 ENGINE_load_public_key, ENGINE_get_RAND, ENGINE_get_RSA, ENGINE_get_id,
15 ENGINE_get_name, ENGINE_get_cmd_defns, ENGINE_get_cipher,
16 ENGINE_get_digest, ENGINE_add, ENGINE_cmd_is_executable, ENGINE_ctrl,
17 ENGINE_ctrl_cmd, ENGINE_ctrl_cmd_string, ENGINE_finish, ENGINE_free,
18 ENGINE_get_flags, ENGINE_init, ENGINE_register_DH, ENGINE_register_DSA,
19 ENGINE_register_RAND, ENGINE_register_RSA,
20 ENGINE_register_all_complete, ENGINE_register_ciphers,
21 ENGINE_register_complete, ENGINE_register_digests, ENGINE_remove,
22 ENGINE_set_DH, ENGINE_set_DSA, ENGINE_set_RAND, ENGINE_set_RSA,
23 ENGINE_set_ciphers, ENGINE_set_cmd_defns, ENGINE_set_ctrl_function,
24 ENGINE_set_default, ENGINE_set_default_DH, ENGINE_set_default_DSA,
25 ENGINE_set_default_RAND, ENGINE_set_default_RSA,
26 ENGINE_set_default_ciphers, ENGINE_set_default_digests,
27 ENGINE_set_default_string, ENGINE_set_destroy_function,
28 ENGINE_set_digests, ENGINE_set_finish_function, ENGINE_set_flags,
29 ENGINE_set_id, ENGINE_set_init_function,
30 ENGINE_set_load_privkey_function, ENGINE_set_load_pubkey_function,
31 ENGINE_set_name, ENGINE_up_ref, ENGINE_get_table_flags, ENGINE_cleanup,
32 ENGINE_load_builtin_engines, ENGINE_register_all_DH,
33 ENGINE_register_all_DSA, ENGINE_register_all_RAND,
34 ENGINE_register_all_RSA, ENGINE_register_all_ciphers,
35 ENGINE_register_all_digests, ENGINE_set_table_flags,
36 ENGINE_unregister_DH, ENGINE_unregister_DSA, ENGINE_unregister_RAND,
37 ENGINE_unregister_RSA, ENGINE_unregister_ciphers,
38 ENGINE_unregister_digests - ENGINE cryptographic module support
39
41 #include <openssl/engine.h>
42 ENGINE *ENGINE_get_first(void);
44 ENGINE *ENGINE_get_last(void);
45 ENGINE *ENGINE_get_next(ENGINE *e);
46 ENGINE *ENGINE_get_prev(ENGINE *e);
47 int ENGINE_add(ENGINE *e);
49 int ENGINE_remove(ENGINE *e);
50 ENGINE *ENGINE_by_id(const char *id);
52 int ENGINE_init(ENGINE *e);
54 int ENGINE_finish(ENGINE *e);
55 void ENGINE_load_builtin_engines(void);
57 ENGINE *ENGINE_get_default_RSA(void);
59 ENGINE *ENGINE_get_default_DSA(void);
60 ENGINE *ENGINE_get_default_DH(void);
61 ENGINE *ENGINE_get_default_RAND(void);
62 ENGINE *ENGINE_get_cipher_engine(int nid);
63 ENGINE *ENGINE_get_digest_engine(int nid);
64 int ENGINE_set_default_RSA(ENGINE *e);
66 int ENGINE_set_default_DSA(ENGINE *e);
67 int ENGINE_set_default_DH(ENGINE *e);
68 int ENGINE_set_default_RAND(ENGINE *e);
69 int ENGINE_set_default_ciphers(ENGINE *e);
70 int ENGINE_set_default_digests(ENGINE *e);
71 int ENGINE_set_default_string(ENGINE *e, const char *list);
72 int ENGINE_set_default(ENGINE *e, unsigned int flags);
74 unsigned int ENGINE_get_table_flags(void);
76 void ENGINE_set_table_flags(unsigned int flags);
77 int ENGINE_register_RSA(ENGINE *e);
79 void ENGINE_unregister_RSA(ENGINE *e);
80 void ENGINE_register_all_RSA(void);
81 int ENGINE_register_DSA(ENGINE *e);
82 void ENGINE_unregister_DSA(ENGINE *e);
83 void ENGINE_register_all_DSA(void);
84 int ENGINE_register_DH(ENGINE *e);
85 void ENGINE_unregister_DH(ENGINE *e);
86 void ENGINE_register_all_DH(void);
87 int ENGINE_register_RAND(ENGINE *e);
88 void ENGINE_unregister_RAND(ENGINE *e);
89 void ENGINE_register_all_RAND(void);
90 int ENGINE_register_ciphers(ENGINE *e);
91 void ENGINE_unregister_ciphers(ENGINE *e);
92 void ENGINE_register_all_ciphers(void);
93 int ENGINE_register_digests(ENGINE *e);
94 void ENGINE_unregister_digests(ENGINE *e);
95 void ENGINE_register_all_digests(void);
96 int ENGINE_register_complete(ENGINE *e);
97 int ENGINE_register_all_complete(void);
98 int ENGINE_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f)(void));
100 int ENGINE_cmd_is_executable(ENGINE *e, int cmd);
101 int ENGINE_ctrl_cmd(ENGINE *e, const char *cmd_name,
102 long i, void *p, void (*f)(void), int cmd_optional);
103 int ENGINE_ctrl_cmd_string(ENGINE *e, const char *cmd_name, const char *arg,
104 int cmd_optional);
105 ENGINE *ENGINE_new(void);
107 int ENGINE_free(ENGINE *e);
108 int ENGINE_up_ref(ENGINE *e);
109 int ENGINE_set_id(ENGINE *e, const char *id);
111 int ENGINE_set_name(ENGINE *e, const char *name);
112 int ENGINE_set_RSA(ENGINE *e, const RSA_METHOD *rsa_meth);
113 int ENGINE_set_DSA(ENGINE *e, const DSA_METHOD *dsa_meth);
114 int ENGINE_set_DH(ENGINE *e, const DH_METHOD *dh_meth);
115 int ENGINE_set_RAND(ENGINE *e, const RAND_METHOD *rand_meth);
116 int ENGINE_set_destroy_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR destroy_f);
117 int ENGINE_set_init_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR init_f);
118 int ENGINE_set_finish_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR finish_f);
119 int ENGINE_set_ctrl_function(ENGINE *e, ENGINE_CTRL_FUNC_PTR ctrl_f);
120 int ENGINE_set_load_privkey_function(ENGINE *e, ENGINE_LOAD_KEY_PTR loadpriv_f);
121 int ENGINE_set_load_pubkey_function(ENGINE *e, ENGINE_LOAD_KEY_PTR loadpub_f);
122 int ENGINE_set_ciphers(ENGINE *e, ENGINE_CIPHERS_PTR f);
123 int ENGINE_set_digests(ENGINE *e, ENGINE_DIGESTS_PTR f);
124 int ENGINE_set_flags(ENGINE *e, int flags);
125 int ENGINE_set_cmd_defns(ENGINE *e, const ENGINE_CMD_DEFN *defns);
126 const char *ENGINE_get_id(const ENGINE *e);
128 const char *ENGINE_get_name(const ENGINE *e);
129 const RSA_METHOD *ENGINE_get_RSA(const ENGINE *e);
130 const DSA_METHOD *ENGINE_get_DSA(const ENGINE *e);
131 const DH_METHOD *ENGINE_get_DH(const ENGINE *e);
132 const RAND_METHOD *ENGINE_get_RAND(const ENGINE *e);
133 ENGINE_GEN_INT_FUNC_PTR ENGINE_get_destroy_function(const ENGINE *e);
134 ENGINE_GEN_INT_FUNC_PTR ENGINE_get_init_function(const ENGINE *e);
135 ENGINE_GEN_INT_FUNC_PTR ENGINE_get_finish_function(const ENGINE *e);
136 ENGINE_CTRL_FUNC_PTR ENGINE_get_ctrl_function(const ENGINE *e);
137 ENGINE_LOAD_KEY_PTR ENGINE_get_load_privkey_function(const ENGINE *e);
138 ENGINE_LOAD_KEY_PTR ENGINE_get_load_pubkey_function(const ENGINE *e);
139 ENGINE_CIPHERS_PTR ENGINE_get_ciphers(const ENGINE *e);
140 ENGINE_DIGESTS_PTR ENGINE_get_digests(const ENGINE *e);
141 const EVP_CIPHER *ENGINE_get_cipher(ENGINE *e, int nid);
142 const EVP_MD *ENGINE_get_digest(ENGINE *e, int nid);
143 int ENGINE_get_flags(const ENGINE *e);
144 const ENGINE_CMD_DEFN *ENGINE_get_cmd_defns(const ENGINE *e);
145 EVP_PKEY *ENGINE_load_private_key(ENGINE *e, const char *key_id,
147 UI_METHOD *ui_method, void *callback_data);
148 EVP_PKEY *ENGINE_load_public_key(ENGINE *e, const char *key_id,
149 UI_METHOD *ui_method, void *callback_data);
150 Deprecated:
152 #if OPENSSL_API_COMPAT < 0x10100000L
154 void ENGINE_cleanup(void)
155 #endif
156
158 These functions create, manipulate, and use cryptographic modules in
159 the form of ENGINE objects. These objects act as containers for
160 implementations of cryptographic algorithms, and support a reference-
161 counted mechanism to allow them to be dynamically loaded in and out of
162 the running application.
163 The cryptographic functionality that can be provided by an ENGINE
165 implementation includes the following abstractions;
166 RSA_METHOD - for providing alternative RSA implementations
168 DSA_METHOD, DH_METHOD, RAND_METHOD, ECDH_METHOD, ECDSA_METHOD,
169 - similarly for other OpenSSL APIs
170 EVP_CIPHER - potentially multiple cipher algorithms (indexed by 'nid')
171 EVP_DIGEST - potentially multiple hash algorithms (indexed by 'nid')
172 key-loading - loading public and/or private EVP_PKEY keys
173 Reference counting and handles
175 Due to the modular nature of the ENGINE API, pointers to ENGINEs need
176 to be treated as handles - i.e. not only as pointers, but also as
177 references to the underlying ENGINE object. Ie. one should obtain a new
178 reference when making copies of an ENGINE pointer if the copies will be
179 used (and released) independently.
180 ENGINE objects have two levels of reference-counting to match the way
182 in which the objects are used. At the most basic level, each ENGINE
183 pointer is inherently a structural reference - a structural reference
184 is required to use the pointer value at all, as this kind of reference
185 is a guarantee that the structure can not be deallocated until the
186 reference is released.
187 However, a structural reference provides no guarantee that the ENGINE
189 is initialised and able to use any of its cryptographic
190 implementations. Indeed it's quite possible that most ENGINEs will not
191 initialise at all in typical environments, as ENGINEs are typically
192 used to support specialised hardware. To use an ENGINE's functionality,
193 you need a functional reference. This kind of reference can be
194 considered a specialised form of structural reference, because each
195 functional reference implicitly contains a structural reference as well
196 - however to avoid difficult-to-find programming bugs, it is
197 recommended to treat the two kinds of reference independently. If you
198 have a functional reference to an ENGINE, you have a guarantee that the
199 ENGINE has been initialised and is ready to perform cryptographic
200 operations, and will remain initialised until after you have released
201 your reference.
202 Structural references
204 This basic type of reference is used for instantiating new ENGINEs,
206 iterating across OpenSSL's internal linked-list of loaded ENGINEs,
207 reading information about an ENGINE, etc. Essentially a structural
208 reference is sufficient if you only need to query or manipulate the
209 data of an ENGINE implementation rather than use its functionality.
210 The ENGINE_new() function returns a structural reference to a new
212 (empty) ENGINE object. There are other ENGINE API functions that return
213 structural references such as; ENGINE_by_id(), ENGINE_get_first(),
214 ENGINE_get_last(), ENGINE_get_next(), ENGINE_get_prev(). All structural
215 references should be released by a corresponding to call to the
216 ENGINE_free() function - the ENGINE object itself will only actually be
217 cleaned up and deallocated when the last structural reference is
218 released.
219 It should also be noted that many ENGINE API function calls that accept
221 a structural reference will internally obtain another reference -
222 typically this happens whenever the supplied ENGINE will be needed by
223 OpenSSL after the function has returned. Eg. the function to add a new
224 ENGINE to OpenSSL's internal list is ENGINE_add() - if this function
225 returns success, then OpenSSL will have stored a new structural
226 reference internally so the caller is still responsible for freeing
227 their own reference with ENGINE_free() when they are finished with it.
228 In a similar way, some functions will automatically release the
229 structural reference passed to it if part of the function's job is to
230 do so. Eg. the ENGINE_get_next() and ENGINE_get_prev() functions are
231 used for iterating across the internal ENGINE list - they will return a
232 new structural reference to the next (or previous) ENGINE in the list
233 or NULL if at the end (or beginning) of the list, but in either case
234 the structural reference passed to the function is released on behalf
235 of the caller.
236 To clarify a particular function's handling of references, one should
238 always consult that function's documentation "man" page, or failing
239 that the openssl/engine.h header file includes some hints.
240 Functional references
242 As mentioned, functional references exist when the cryptographic
244 functionality of an ENGINE is required to be available. A functional
245 reference can be obtained in one of two ways; from an existing
246 structural reference to the required ENGINE, or by asking OpenSSL for
247 the default operational ENGINE for a given cryptographic purpose.
248 To obtain a functional reference from an existing structural reference,
250 call the ENGINE_init() function. This returns zero if the ENGINE was
251 not already operational and couldn't be successfully initialised (e.g.
252 lack of system drivers, no special hardware attached, etc), otherwise
253 it will return nonzero to indicate that the ENGINE is now operational
254 and will have allocated a new functional reference to the ENGINE. All
255 functional references are released by calling ENGINE_finish() (which
256 removes the implicit structural reference as well).
257 The second way to get a functional reference is by asking OpenSSL for a
259 default implementation for a given task, e.g. by
260 ENGINE_get_default_RSA(), ENGINE_get_default_cipher_engine(), etc.
261 These are discussed in the next section, though they are not usually
262 required by application programmers as they are used automatically when
263 creating and using the relevant algorithm-specific types in OpenSSL,
264 such as RSA, DSA, EVP_CIPHER_CTX, etc.
265 Default implementations
267 For each supported abstraction, the ENGINE code maintains an internal
268 table of state to control which implementations are available for a
269 given abstraction and which should be used by default. These
270 implementations are registered in the tables and indexed by an 'nid'
271 value, because abstractions like EVP_CIPHER and EVP_DIGEST support many
272 distinct algorithms and modes, and ENGINEs can support arbitrarily many
273 of them. In the case of other abstractions like RSA, DSA, etc, there
274 is only one "algorithm" so all implementations implicitly register
275 using the same 'nid' index.
276 When a default ENGINE is requested for a given
278 abstraction/algorithm/mode, (e.g. when calling RSA_new_method(NULL)),
279 a "get_default" call will be made to the ENGINE subsystem to process
280 the corresponding state table and return a functional reference to an
281 initialised ENGINE whose implementation should be used. If no ENGINE
282 should (or can) be used, it will return NULL and the caller will
283 operate with a NULL ENGINE handle - this usually equates to using the
284 conventional software implementation. In the latter case, OpenSSL will
285 from then on behave the way it used to before the ENGINE API existed.
286 Each state table has a flag to note whether it has processed this
288 "get_default" query since the table was last modified, because to
289 process this question it must iterate across all the registered ENGINEs
290 in the table trying to initialise each of them in turn, in case one of
291 them is operational. If it returns a functional reference to an ENGINE,
292 it will also cache another reference to speed up processing future
293 queries (without needing to iterate across the table). Likewise, it
294 will cache a NULL response if no ENGINE was available so that future
295 queries won't repeat the same iteration unless the state table changes.
296 This behaviour can also be changed; if the ENGINE_TABLE_FLAG_NOINIT
297 flag is set (using ENGINE_set_table_flags()), no attempted
298 initialisations will take place, instead the only way for the state
299 table to return a non-NULL ENGINE to the "get_default" query will be if
300 one is expressly set in the table. Eg. ENGINE_set_default_RSA() does
301 the same job as ENGINE_register_RSA() except that it also sets the
302 state table's cached response for the "get_default" query. In the case
303 of abstractions like EVP_CIPHER, where implementations are indexed by
304 'nid', these flags and cached-responses are distinct for each 'nid'
305 value.
306 Application requirements
308 This section will explain the basic things an application programmer
309 should support to make the most useful elements of the ENGINE
310 functionality available to the user. The first thing to consider is
311 whether the programmer wishes to make alternative ENGINE modules
312 available to the application and user. OpenSSL maintains an internal
313 linked list of "visible" ENGINEs from which it has to operate - at
314 start-up, this list is empty and in fact if an application does not
315 call any ENGINE API calls and it uses static linking against openssl,
316 then the resulting application binary will not contain any alternative
317 ENGINE code at all. So the first consideration is whether any/all
318 available ENGINE implementations should be made visible to OpenSSL -
319 this is controlled by calling the various "load" functions.
320 The fact that ENGINEs are made visible to OpenSSL (and thus are linked
322 into the program and loaded into memory at run-time) does not mean they
323 are "registered" or called into use by OpenSSL automatically - that
324 behaviour is something for the application to control. Some
325 applications will want to allow the user to specify exactly which
326 ENGINE they want used if any is to be used at all. Others may prefer to
327 load all support and have OpenSSL automatically use at run-time any
328 ENGINE that is able to successfully initialise - i.e. to assume that
329 this corresponds to acceleration hardware attached to the machine or
330 some such thing. There are probably numerous other ways in which
331 applications may prefer to handle things, so we will simply illustrate
332 the consequences as they apply to a couple of simple cases and leave
333 developers to consider these and the source code to openssl's builtin
334 utilities as guides.
335 If no ENGINE API functions are called within an application, then
337 OpenSSL will not allocate any internal resources. Prior to OpenSSL
338 1.1.0, however, if any ENGINEs are loaded, even if not registered or
339 used, it was necessary to call ENGINE_cleanup() before the program
340 exits.
341 Using a specific ENGINE implementation
343 Here we'll assume an application has been configured by its user or
345 admin to want to use the "ACME" ENGINE if it is available in the
346 version of OpenSSL the application was compiled with. If it is
347 available, it should be used by default for all RSA, DSA, and symmetric
348 cipher operations, otherwise OpenSSL should use its builtin software as
349 per usual. The following code illustrates how to approach this;
350 ENGINE *e;
352 const char *engine_id = "ACME";
353 ENGINE_load_builtin_engines();
354 e = ENGINE_by_id(engine_id);
355 if (!e)
356 /* the engine isn't available */
357 return;
358 if (!ENGINE_init(e)) {
359 /* the engine couldn't initialise, release 'e' */
360 ENGINE_free(e);
361 return;
362 }
363 if (!ENGINE_set_default_RSA(e))
364 /*
365 * This should only happen when 'e' can't initialise, but the previous
366 * statement suggests it did.
367 */
368 abort();
369 ENGINE_set_default_DSA(e);
370 ENGINE_set_default_ciphers(e);
371 /* Release the functional reference from ENGINE_init() */
372 ENGINE_finish(e);
373 /* Release the structural reference from ENGINE_by_id() */
374 ENGINE_free(e);
375 Automatically using builtin ENGINE implementations
377 Here we'll assume we want to load and register all ENGINE
379 implementations bundled with OpenSSL, such that for any cryptographic
380 algorithm required by OpenSSL - if there is an ENGINE that implements
381 it and can be initialised, it should be used. The following code
382 illustrates how this can work;
383 /* Load all bundled ENGINEs into memory and make them visible */
385 ENGINE_load_builtin_engines();
386 /* Register all of them for every algorithm they collectively implement */
387 ENGINE_register_all_complete();
388 That's all that's required. Eg. the next time OpenSSL tries to set up
390 an RSA key, any bundled ENGINEs that implement RSA_METHOD will be
391 passed to ENGINE_init() and if any of those succeed, that ENGINE will
392 be set as the default for RSA use from then on.
393 Advanced configuration support
395 There is a mechanism supported by the ENGINE framework that allows each
396 ENGINE implementation to define an arbitrary set of configuration
397 "commands" and expose them to OpenSSL and any applications based on
398 OpenSSL. This mechanism is entirely based on the use of name-value
399 pairs and assumes ASCII input (no unicode or UTF for now!), so it is
400 ideal if applications want to provide a transparent way for users to
401 provide arbitrary configuration "directives" directly to such ENGINEs.
402 It is also possible for the application to dynamically interrogate the
403 loaded ENGINE implementations for the names, descriptions, and input
404 flags of their available "control commands", providing a more flexible
405 configuration scheme. However, if the user is expected to know which
406 ENGINE device he/she is using (in the case of specialised hardware,
407 this goes without saying) then applications may not need to concern
408 themselves with discovering the supported control commands and simply
409 prefer to pass settings into ENGINEs exactly as they are provided by
410 the user.
411 Before illustrating how control commands work, it is worth mentioning
413 what they are typically used for. Broadly speaking there are two uses
414 for control commands; the first is to provide the necessary details to
415 the implementation (which may know nothing at all specific to the host
416 system) so that it can be initialised for use. This could include the
417 path to any driver or config files it needs to load, required network
418 addresses, smart-card identifiers, passwords to initialise protected
419 devices, logging information, etc etc. This class of commands typically
420 needs to be passed to an ENGINE before attempting to initialise it,
421 i.e. before calling ENGINE_init(). The other class of commands consist
422 of settings or operations that tweak certain behaviour or cause certain
423 operations to take place, and these commands may work either before or
424 after ENGINE_init(), or in some cases both. ENGINE implementations
425 should provide indications of this in the descriptions attached to
426 builtin control commands and/or in external product documentation.
427 Issuing control commands to an ENGINE
429 Let's illustrate by example; a function for which the caller supplies
431 the name of the ENGINE it wishes to use, a table of string-pairs for
432 use before initialisation, and another table for use after
433 initialisation. Note that the string-pairs used for control commands
434 consist of a command "name" followed by the command "parameter" - the
435 parameter could be NULL in some cases but the name can not. This
436 function should initialise the ENGINE (issuing the "pre" commands
437 beforehand and the "post" commands afterwards) and set it as the
438 default for everything except RAND and then return a boolean success or
439 failure.
440 int generic_load_engine_fn(const char *engine_id,
442 const char **pre_cmds, int pre_num,
443 const char **post_cmds, int post_num)
444 {
445 ENGINE *e = ENGINE_by_id(engine_id);
446 if (!e) return 0;
447 while (pre_num--) {
448 if (!ENGINE_ctrl_cmd_string(e, pre_cmds[0], pre_cmds[1], 0)) {
449 fprintf(stderr, "Failed command (%s - %s:%s)\n", engine_id,
450 pre_cmds[0], pre_cmds[1] ? pre_cmds[1] : "(NULL)");
451 ENGINE_free(e);
452 return 0;
453 }
454 pre_cmds += 2;
455 }
456 if (!ENGINE_init(e)) {
457 fprintf(stderr, "Failed initialisation\n");
458 ENGINE_free(e);
459 return 0;
460 }
461 /*
462 * ENGINE_init() returned a functional reference, so free the structural
463 * reference from ENGINE_by_id().
464 */
465 ENGINE_free(e);
466 while (post_num--) {
467 if (!ENGINE_ctrl_cmd_string(e, post_cmds[0], post_cmds[1], 0)) {
468 fprintf(stderr, "Failed command (%s - %s:%s)\n", engine_id,
469 post_cmds[0], post_cmds[1] ? post_cmds[1] : "(NULL)");
470 ENGINE_finish(e);
471 return 0;
472 }
473 post_cmds += 2;
474 }
475 ENGINE_set_default(e, ENGINE_METHOD_ALL & ~ENGINE_METHOD_RAND);
476 /* Success */
477 return 1;
478 }
479 Note that ENGINE_ctrl_cmd_string() accepts a boolean argument that can
481 relax the semantics of the function - if set nonzero it will only
482 return failure if the ENGINE supported the given command name but
483 failed while executing it, if the ENGINE doesn't support the command
484 name it will simply return success without doing anything. In this case
485 we assume the user is only supplying commands specific to the given
486 ENGINE so we set this to FALSE.
487 Discovering supported control commands
489 It is possible to discover at run-time the names, numerical-ids,
491 descriptions and input parameters of the control commands supported by
492 an ENGINE using a structural reference. Note that some control commands
493 are defined by OpenSSL itself and it will intercept and handle these
494 control commands on behalf of the ENGINE, i.e. the ENGINE's ctrl()
495 handler is not used for the control command. openssl/engine.h defines
496 an index, ENGINE_CMD_BASE, that all control commands implemented by
497 ENGINEs should be numbered from. Any command value lower than this
498 symbol is considered a "generic" command is handled directly by the
499 OpenSSL core routines.
500 It is using these "core" control commands that one can discover the
502 control commands implemented by a given ENGINE, specifically the
503 commands:
504 ENGINE_HAS_CTRL_FUNCTION
506 ENGINE_CTRL_GET_FIRST_CMD_TYPE
507 ENGINE_CTRL_GET_NEXT_CMD_TYPE
508 ENGINE_CTRL_GET_CMD_FROM_NAME
509 ENGINE_CTRL_GET_NAME_LEN_FROM_CMD
510 ENGINE_CTRL_GET_NAME_FROM_CMD
511 ENGINE_CTRL_GET_DESC_LEN_FROM_CMD
512 ENGINE_CTRL_GET_DESC_FROM_CMD
513 ENGINE_CTRL_GET_CMD_FLAGS
514 Whilst these commands are automatically processed by the OpenSSL
516 framework code, they use various properties exposed by each ENGINE to
517 process these queries. An ENGINE has 3 properties it exposes that can
518 affect how this behaves; it can supply a ctrl() handler, it can specify
519 ENGINE_FLAGS_MANUAL_CMD_CTRL in the ENGINE's flags, and it can expose
520 an array of control command descriptions. If an ENGINE specifies the
521 ENGINE_FLAGS_MANUAL_CMD_CTRL flag, then it will simply pass all these
522 "core" control commands directly to the ENGINE's ctrl() handler (and
523 thus, it must have supplied one), so it is up to the ENGINE to reply to
524 these "discovery" commands itself. If that flag is not set, then the
525 OpenSSL framework code will work with the following rules:
526 if no ctrl() handler supplied;
528 ENGINE_HAS_CTRL_FUNCTION returns FALSE (zero),
529 all other commands fail.
530 if a ctrl() handler was supplied but no array of control commands;
531 ENGINE_HAS_CTRL_FUNCTION returns TRUE,
532 all other commands fail.
533 if a ctrl() handler and array of control commands was supplied;
534 ENGINE_HAS_CTRL_FUNCTION returns TRUE,
535 all other commands proceed processing ...
536 If the ENGINE's array of control commands is empty then all other
538 commands will fail, otherwise; ENGINE_CTRL_GET_FIRST_CMD_TYPE returns
539 the identifier of the first command supported by the ENGINE,
540 ENGINE_GET_NEXT_CMD_TYPE takes the identifier of a command supported by
541 the ENGINE and returns the next command identifier or fails if there
542 are no more, ENGINE_CMD_FROM_NAME takes a string name for a command and
543 returns the corresponding identifier or fails if no such command name
544 exists, and the remaining commands take a command identifier and return
545 properties of the corresponding commands. All except
546 ENGINE_CTRL_GET_FLAGS return the string length of a command name or
547 description, or populate a supplied character buffer with a copy of the
548 command name or description. ENGINE_CTRL_GET_FLAGS returns a bitwise-
549 OR'd mask of the following possible values:
550 ENGINE_CMD_FLAG_NUMERIC
552 ENGINE_CMD_FLAG_STRING
553 ENGINE_CMD_FLAG_NO_INPUT
554 ENGINE_CMD_FLAG_INTERNAL
555 If the ENGINE_CMD_FLAG_INTERNAL flag is set, then any other flags are
557 purely informational to the caller - this flag will prevent the command
558 being usable for any higher-level ENGINE functions such as
559 ENGINE_ctrl_cmd_string(). "INTERNAL" commands are not intended to be
560 exposed to text-based configuration by applications, administrations,
561 users, etc. These can support arbitrary operations via ENGINE_ctrl(),
562 including passing to and/or from the control commands data of any
563 arbitrary type. These commands are supported in the discovery
564 mechanisms simply to allow applications to determine if an ENGINE
565 supports certain specific commands it might want to use (e.g.
566 application "foo" might query various ENGINEs to see if they implement
567 "FOO_GET_VENDOR_LOGO_GIF" - and ENGINE could therefore decide whether
568 or not to support this "foo"-specific extension).
569
571 OPENSSL_ENGINES
572 The path to the engines directory. Ignored in set-user-ID and set-
573 group-ID programs.
574
576 ENGINE_get_first(), ENGINE_get_last(), ENGINE_get_next() and
577 ENGINE_get_prev() return a valid ENGINE structure or NULL if an error
578 occurred.
579 ENGINE_add() and ENGINE_remove() return 1 on success or 0 on error.
581 ENGINE_by_id() returns a valid ENGINE structure or NULL if an error
583 occurred.
584 ENGINE_init() and ENGINE_finish() return 1 on success or 0 on error.
586 All ENGINE_get_default_TYPE() functions, ENGINE_get_cipher_engine() and
588 ENGINE_get_digest_engine() return a valid ENGINE structure on success
589 or NULL if an error occurred.
590 All ENGINE_set_default_TYPE() functions return 1 on success or 0 on
592 error.
593 ENGINE_set_default() returns 1 on success or 0 on error.
595 ENGINE_get_table_flags() returns an unsigned integer value representing
597 the global table flags which are used to control the registration
598 behaviour of ENGINE implementations.
599 All ENGINE_register_TYPE() functions return 1 on success or 0 on error.
601 ENGINE_register_complete() and ENGINE_register_all_complete() always
603 return 1.
604 ENGINE_ctrl() returns a positive value on success or others on error.
606 ENGINE_cmd_is_executable() returns 1 if cmd is executable or 0
608 otherwise.
609 ENGINE_ctrl_cmd() and ENGINE_ctrl_cmd_string() return 1 on success or 0
611 on error.
612 ENGINE_new() returns a valid ENGINE structure on success or NULL if an
614 error occurred.
615 ENGINE_free() always returns 1.
617 ENGINE_up_ref() returns 1 on success or 0 on error.
619 ENGINE_set_id() and ENGINE_set_name() return 1 on success or 0 on
621 error.
622 All other ENGINE_set_* functions return 1 on success or 0 on error.
624 ENGINE_get_id() and ENGINE_get_name() return a string representing the
626 identifier and the name of the ENGINE e respectively.
627 ENGINE_get_RSA(), ENGINE_get_DSA(), ENGINE_get_DH() and
629 ENGINE_get_RAND() return corresponding method structures for each
630 algorithms.
631 ENGINE_get_destroy_function(), ENGINE_get_init_function(),
633 ENGINE_get_finish_function(), ENGINE_get_ctrl_function(),
634 ENGINE_get_load_privkey_function(), ENGINE_get_load_pubkey_function(),
635 ENGINE_get_ciphers() and ENGINE_get_digests() return corresponding
636 function pointers of the callbacks.
637 ENGINE_get_cipher() returns a valid EVP_CIPHER structure on success or
639 NULL if an error occurred.
640 ENGINE_get_digest() returns a valid EVP_MD structure on success or NULL
642 if an error occurred.
643 ENGINE_get_flags() returns an integer representing the ENGINE flags
645 which are used to control various behaviours of an ENGINE.
646 ENGINE_get_cmd_defns() returns an ENGINE_CMD_DEFN structure or NULL if
648 it's not set.
649 ENGINE_load_private_key() and ENGINE_load_public_key() return a valid
651 EVP_PKEY structure on success or NULL if an error occurred.
652
654 OPENSSL_init_crypto(3), RSA_new_method(3), DSA_new(3), DH_new(3),
655 RAND_bytes(3), config(5)
656
658 ENGINE_cleanup() was deprecated in OpenSSL 1.1.0 by the automatic
659 cleanup done by OPENSSL_cleanup() and should not be used.
660
662 Copyright 2002-2021 The OpenSSL Project Authors. All Rights Reserved.
663 Licensed under the OpenSSL license (the "License"). You may not use
665 this file except in compliance with the License. You can obtain a copy
666 in the file LICENSE in the source distribution or at
667 <https://www.openssl.org/source/license.html>.
6681.1.1q 2023-02-06 ENGINE_ADD(3)