1engine(3) OpenSSL engine(3)
2
6 engine - ENGINE cryptographic module support
7
9 #include <openssl/engine.h>
10 ENGINE *ENGINE_get_first(void);
12 ENGINE *ENGINE_get_last(void);
13 ENGINE *ENGINE_get_next(ENGINE *e);
14 ENGINE *ENGINE_get_prev(ENGINE *e);
15 int ENGINE_add(ENGINE *e);
17 int ENGINE_remove(ENGINE *e);
18 ENGINE *ENGINE_by_id(const char *id);
20 int ENGINE_init(ENGINE *e);
22 int ENGINE_finish(ENGINE *e);
23 void ENGINE_load_openssl(void);
25 void ENGINE_load_dynamic(void);
26 #ifndef OPENSSL_NO_STATIC_ENGINE
27 void ENGINE_load_4758cca(void);
28 void ENGINE_load_aep(void);
29 void ENGINE_load_atalla(void);
30 void ENGINE_load_chil(void);
31 void ENGINE_load_cswift(void);
32 void ENGINE_load_gmp(void);
33 void ENGINE_load_nuron(void);
34 void ENGINE_load_sureware(void);
35 void ENGINE_load_ubsec(void);
36 #endif
37 void ENGINE_load_cryptodev(void);
38 void ENGINE_load_builtin_engines(void);
39 void ENGINE_cleanup(void);
41 ENGINE *ENGINE_get_default_RSA(void);
43 ENGINE *ENGINE_get_default_DSA(void);
44 ENGINE *ENGINE_get_default_ECDH(void);
45 ENGINE *ENGINE_get_default_ECDSA(void);
46 ENGINE *ENGINE_get_default_DH(void);
47 ENGINE *ENGINE_get_default_RAND(void);
48 ENGINE *ENGINE_get_cipher_engine(int nid);
49 ENGINE *ENGINE_get_digest_engine(int nid);
50 int ENGINE_set_default_RSA(ENGINE *e);
52 int ENGINE_set_default_DSA(ENGINE *e);
53 int ENGINE_set_default_ECDH(ENGINE *e);
54 int ENGINE_set_default_ECDSA(ENGINE *e);
55 int ENGINE_set_default_DH(ENGINE *e);
56 int ENGINE_set_default_RAND(ENGINE *e);
57 int ENGINE_set_default_ciphers(ENGINE *e);
58 int ENGINE_set_default_digests(ENGINE *e);
59 int ENGINE_set_default_string(ENGINE *e, const char *list);
60 int ENGINE_set_default(ENGINE *e, unsigned int flags);
62 unsigned int ENGINE_get_table_flags(void);
64 void ENGINE_set_table_flags(unsigned int flags);
65 int ENGINE_register_RSA(ENGINE *e);
67 void ENGINE_unregister_RSA(ENGINE *e);
68 void ENGINE_register_all_RSA(void);
69 int ENGINE_register_DSA(ENGINE *e);
70 void ENGINE_unregister_DSA(ENGINE *e);
71 void ENGINE_register_all_DSA(void);
72 int ENGINE_register_ECDH(ENGINE *e);
73 void ENGINE_unregister_ECDH(ENGINE *e);
74 void ENGINE_register_all_ECDH(void);
75 int ENGINE_register_ECDSA(ENGINE *e);
76 void ENGINE_unregister_ECDSA(ENGINE *e);
77 void ENGINE_register_all_ECDSA(void);
78 int ENGINE_register_DH(ENGINE *e);
79 void ENGINE_unregister_DH(ENGINE *e);
80 void ENGINE_register_all_DH(void);
81 int ENGINE_register_RAND(ENGINE *e);
82 void ENGINE_unregister_RAND(ENGINE *e);
83 void ENGINE_register_all_RAND(void);
84 int ENGINE_register_STORE(ENGINE *e);
85 void ENGINE_unregister_STORE(ENGINE *e);
86 void ENGINE_register_all_STORE(void);
87 int ENGINE_register_ciphers(ENGINE *e);
88 void ENGINE_unregister_ciphers(ENGINE *e);
89 void ENGINE_register_all_ciphers(void);
90 int ENGINE_register_digests(ENGINE *e);
91 void ENGINE_unregister_digests(ENGINE *e);
92 void ENGINE_register_all_digests(void);
93 int ENGINE_register_complete(ENGINE *e);
94 int ENGINE_register_all_complete(void);
95 int ENGINE_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f)(void));
97 int ENGINE_cmd_is_executable(ENGINE *e, int cmd);
98 int ENGINE_ctrl_cmd(ENGINE *e, const char *cmd_name,
99 long i, void *p, void (*f)(void), int cmd_optional);
100 int ENGINE_ctrl_cmd_string(ENGINE *e, const char *cmd_name, const char *arg,
101 int cmd_optional);
102 int ENGINE_set_ex_data(ENGINE *e, int idx, void *arg);
104 void *ENGINE_get_ex_data(const ENGINE *e, int idx);
105 int ENGINE_get_ex_new_index(long argl, void *argp, CRYPTO_EX_new *new_func,
107 CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func);
108 ENGINE *ENGINE_new(void);
110 int ENGINE_free(ENGINE *e);
111 int ENGINE_up_ref(ENGINE *e);
112 int ENGINE_set_id(ENGINE *e, const char *id);
114 int ENGINE_set_name(ENGINE *e, const char *name);
115 int ENGINE_set_RSA(ENGINE *e, const RSA_METHOD *rsa_meth);
116 int ENGINE_set_DSA(ENGINE *e, const DSA_METHOD *dsa_meth);
117 int ENGINE_set_ECDH(ENGINE *e, const ECDH_METHOD *dh_meth);
118 int ENGINE_set_ECDSA(ENGINE *e, const ECDSA_METHOD *dh_meth);
119 int ENGINE_set_DH(ENGINE *e, const DH_METHOD *dh_meth);
120 int ENGINE_set_RAND(ENGINE *e, const RAND_METHOD *rand_meth);
121 int ENGINE_set_STORE(ENGINE *e, const STORE_METHOD *rand_meth);
122 int ENGINE_set_destroy_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR destroy_f);
123 int ENGINE_set_init_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR init_f);
124 int ENGINE_set_finish_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR finish_f);
125 int ENGINE_set_ctrl_function(ENGINE *e, ENGINE_CTRL_FUNC_PTR ctrl_f);
126 int ENGINE_set_load_privkey_function(ENGINE *e, ENGINE_LOAD_KEY_PTR loadpriv_f);
127 int ENGINE_set_load_pubkey_function(ENGINE *e, ENGINE_LOAD_KEY_PTR loadpub_f);
128 int ENGINE_set_ciphers(ENGINE *e, ENGINE_CIPHERS_PTR f);
129 int ENGINE_set_digests(ENGINE *e, ENGINE_DIGESTS_PTR f);
130 int ENGINE_set_flags(ENGINE *e, int flags);
131 int ENGINE_set_cmd_defns(ENGINE *e, const ENGINE_CMD_DEFN *defns);
132 const char *ENGINE_get_id(const ENGINE *e);
134 const char *ENGINE_get_name(const ENGINE *e);
135 const RSA_METHOD *ENGINE_get_RSA(const ENGINE *e);
136 const DSA_METHOD *ENGINE_get_DSA(const ENGINE *e);
137 const ECDH_METHOD *ENGINE_get_ECDH(const ENGINE *e);
138 const ECDSA_METHOD *ENGINE_get_ECDSA(const ENGINE *e);
139 const DH_METHOD *ENGINE_get_DH(const ENGINE *e);
140 const RAND_METHOD *ENGINE_get_RAND(const ENGINE *e);
141 const STORE_METHOD *ENGINE_get_STORE(const ENGINE *e);
142 ENGINE_GEN_INT_FUNC_PTR ENGINE_get_destroy_function(const ENGINE *e);
143 ENGINE_GEN_INT_FUNC_PTR ENGINE_get_init_function(const ENGINE *e);
144 ENGINE_GEN_INT_FUNC_PTR ENGINE_get_finish_function(const ENGINE *e);
145 ENGINE_CTRL_FUNC_PTR ENGINE_get_ctrl_function(const ENGINE *e);
146 ENGINE_LOAD_KEY_PTR ENGINE_get_load_privkey_function(const ENGINE *e);
147 ENGINE_LOAD_KEY_PTR ENGINE_get_load_pubkey_function(const ENGINE *e);
148 ENGINE_CIPHERS_PTR ENGINE_get_ciphers(const ENGINE *e);
149 ENGINE_DIGESTS_PTR ENGINE_get_digests(const ENGINE *e);
150 const EVP_CIPHER *ENGINE_get_cipher(ENGINE *e, int nid);
151 const EVP_MD *ENGINE_get_digest(ENGINE *e, int nid);
152 int ENGINE_get_flags(const ENGINE *e);
153 const ENGINE_CMD_DEFN *ENGINE_get_cmd_defns(const ENGINE *e);
154 EVP_PKEY *ENGINE_load_private_key(ENGINE *e, const char *key_id,
156 UI_METHOD *ui_method, void *callback_data);
157 EVP_PKEY *ENGINE_load_public_key(ENGINE *e, const char *key_id,
158 UI_METHOD *ui_method, void *callback_data);
159 void ENGINE_add_conf_module(void);
161
163 These functions create, manipulate, and use cryptographic modules in
164 the form of ENGINE objects. These objects act as containers for
165 implementations of cryptographic algorithms, and support a reference-
166 counted mechanism to allow them to be dynamically loaded in and out of
167 the running application.
168 The cryptographic functionality that can be provided by an ENGINE
170 implementation includes the following abstractions;
171 RSA_METHOD - for providing alternative RSA implementations
173 DSA_METHOD, DH_METHOD, RAND_METHOD, ECDH_METHOD, ECDSA_METHOD,
174 STORE_METHOD - similarly for other OpenSSL APIs
175 EVP_CIPHER - potentially multiple cipher algorithms (indexed by 'nid')
176 EVP_DIGEST - potentially multiple hash algorithms (indexed by 'nid')
177 key-loading - loading public and/or private EVP_PKEY keys
178 Reference counting and handles
180 Due to the modular nature of the ENGINE API, pointers to ENGINEs need
181 to be treated as handles - ie. not only as pointers, but also as
182 references to the underlying ENGINE object. Ie. one should obtain a new
183 reference when making copies of an ENGINE pointer if the copies will be
184 used (and released) independently.
185 ENGINE objects have two levels of reference-counting to match the way
187 in which the objects are used. At the most basic level, each ENGINE
188 pointer is inherently a structural reference - a structural reference
189 is required to use the pointer value at all, as this kind of reference
190 is a guarantee that the structure can not be deallocated until the
191 reference is released.
192 However, a structural reference provides no guarantee that the ENGINE
194 is initiliased and able to use any of its cryptographic
195 implementations. Indeed it's quite possible that most ENGINEs will not
196 initialise at all in typical environments, as ENGINEs are typically
197 used to support specialised hardware. To use an ENGINE's functionality,
198 you need a functional reference. This kind of reference can be
199 considered a specialised form of structural reference, because each
200 functional reference implicitly contains a structural reference as well
201 - however to avoid difficult-to-find programming bugs, it is
202 recommended to treat the two kinds of reference independently. If you
203 have a functional reference to an ENGINE, you have a guarantee that the
204 ENGINE has been initialised ready to perform cryptographic operations
205 and will remain uninitialised until after you have released your
206 reference.
207 Structural references
209 This basic type of reference is used for instantiating new ENGINEs,
211 iterating across OpenSSL's internal linked-list of loaded ENGINEs,
212 reading information about an ENGINE, etc. Essentially a structural
213 reference is sufficient if you only need to query or manipulate the
214 data of an ENGINE implementation rather than use its functionality.
215 The ENGINE_new() function returns a structural reference to a new
217 (empty) ENGINE object. There are other ENGINE API functions that return
218 structural references such as; ENGINE_by_id(), ENGINE_get_first(),
219 ENGINE_get_last(), ENGINE_get_next(), ENGINE_get_prev(). All structural
220 references should be released by a corresponding to call to the
221 ENGINE_free() function - the ENGINE object itself will only actually be
222 cleaned up and deallocated when the last structural reference is
223 released.
224 It should also be noted that many ENGINE API function calls that accept
226 a structural reference will internally obtain another reference -
227 typically this happens whenever the supplied ENGINE will be needed by
228 OpenSSL after the function has returned. Eg. the function to add a new
229 ENGINE to OpenSSL's internal list is ENGINE_add() - if this function
230 returns success, then OpenSSL will have stored a new structural
231 reference internally so the caller is still responsible for freeing
232 their own reference with ENGINE_free() when they are finished with it.
233 In a similar way, some functions will automatically release the
234 structural reference passed to it if part of the function's job is to
235 do so. Eg. the ENGINE_get_next() and ENGINE_get_prev() functions are
236 used for iterating across the internal ENGINE list - they will return a
237 new structural reference to the next (or previous) ENGINE in the list
238 or NULL if at the end (or beginning) of the list, but in either case
239 the structural reference passed to the function is released on behalf
240 of the caller.
241 To clarify a particular function's handling of references, one should
243 always consult that function's documentation "man" page, or failing
244 that the openssl/engine.h header file includes some hints.
245 Functional references
247 As mentioned, functional references exist when the cryptographic
249 functionality of an ENGINE is required to be available. A functional
250 reference can be obtained in one of two ways; from an existing
251 structural reference to the required ENGINE, or by asking OpenSSL for
252 the default operational ENGINE for a given cryptographic purpose.
253 To obtain a functional reference from an existing structural reference,
255 call the ENGINE_init() function. This returns zero if the ENGINE was
256 not already operational and couldn't be successfully initialised (eg.
257 lack of system drivers, no special hardware attached, etc), otherwise
258 it will return non-zero to indicate that the ENGINE is now operational
259 and will have allocated a new functional reference to the ENGINE. All
260 functional references are released by calling ENGINE_finish() (which
261 removes the implicit structural reference as well).
262 The second way to get a functional reference is by asking OpenSSL for a
264 default implementation for a given task, eg. by
265 ENGINE_get_default_RSA(), ENGINE_get_default_cipher_engine(), etc.
266 These are discussed in the next section, though they are not usually
267 required by application programmers as they are used automatically when
268 creating and using the relevant algorithm-specific types in OpenSSL,
269 such as RSA, DSA, EVP_CIPHER_CTX, etc.
270 Default implementations
272 For each supported abstraction, the ENGINE code maintains an internal
273 table of state to control which implementations are available for a
274 given abstraction and which should be used by default. These
275 implementations are registered in the tables and indexed by an 'nid'
276 value, because abstractions like EVP_CIPHER and EVP_DIGEST support many
277 distinct algorithms and modes, and ENGINEs can support arbitrarily many
278 of them. In the case of other abstractions like RSA, DSA, etc, there
279 is only one "algorithm" so all implementations implicitly register
280 using the same 'nid' index.
281 When a default ENGINE is requested for a given
283 abstraction/algorithm/mode, (eg. when calling RSA_new_method(NULL)), a
284 "get_default" call will be made to the ENGINE subsystem to process the
285 corresponding state table and return a functional reference to an
286 initialised ENGINE whose implementation should be used. If no ENGINE
287 should (or can) be used, it will return NULL and the caller will
288 operate with a NULL ENGINE handle - this usually equates to using the
289 conventional software implementation. In the latter case, OpenSSL will
290 from then on behave the way it used to before the ENGINE API existed.
291 Each state table has a flag to note whether it has processed this
293 "get_default" query since the table was last modified, because to
294 process this question it must iterate across all the registered ENGINEs
295 in the table trying to initialise each of them in turn, in case one of
296 them is operational. If it returns a functional reference to an ENGINE,
297 it will also cache another reference to speed up processing future
298 queries (without needing to iterate across the table). Likewise, it
299 will cache a NULL response if no ENGINE was available so that future
300 queries won't repeat the same iteration unless the state table changes.
301 This behaviour can also be changed; if the ENGINE_TABLE_FLAG_NOINIT
302 flag is set (using ENGINE_set_table_flags()), no attempted
303 initialisations will take place, instead the only way for the state
304 table to return a non-NULL ENGINE to the "get_default" query will be if
305 one is expressly set in the table. Eg. ENGINE_set_default_RSA() does
306 the same job as ENGINE_register_RSA() except that it also sets the
307 state table's cached response for the "get_default" query. In the case
308 of abstractions like EVP_CIPHER, where implementations are indexed by
309 'nid', these flags and cached-responses are distinct for each 'nid'
310 value.
311 Application requirements
313 This section will explain the basic things an application programmer
314 should support to make the most useful elements of the ENGINE
315 functionality available to the user. The first thing to consider is
316 whether the programmer wishes to make alternative ENGINE modules
317 available to the application and user. OpenSSL maintains an internal
318 linked list of "visible" ENGINEs from which it has to operate - at
319 start-up, this list is empty and in fact if an application does not
320 call any ENGINE API calls and it uses static linking against openssl,
321 then the resulting application binary will not contain any alternative
322 ENGINE code at all. So the first consideration is whether any/all
323 available ENGINE implementations should be made visible to OpenSSL -
324 this is controlled by calling the various "load" functions, eg.
325 /* Make the "dynamic" ENGINE available */
327 void ENGINE_load_dynamic(void);
328 /* Make the CryptoSwift hardware acceleration support available */
329 void ENGINE_load_cswift(void);
330 /* Make support for nCipher's "CHIL" hardware available */
331 void ENGINE_load_chil(void);
332 ...
333 /* Make ALL ENGINE implementations bundled with OpenSSL available */
334 void ENGINE_load_builtin_engines(void);
335 Having called any of these functions, ENGINE objects would have been
337 dynamically allocated and populated with these implementations and
338 linked into OpenSSL's internal linked list. At this point it is
339 important to mention an important API function;
340 void ENGINE_cleanup(void);
342 If no ENGINE API functions are called at all in an application, then
344 there are no inherent memory leaks to worry about from the ENGINE
345 functionality, however if any ENGINEs are loaded, even if they are
346 never registered or used, it is necessary to use the ENGINE_cleanup()
347 function to correspondingly cleanup before program exit, if the caller
348 wishes to avoid memory leaks. This mechanism uses an internal callback
349 registration table so that any ENGINE API functionality that knows it
350 requires cleanup can register its cleanup details to be called during
351 ENGINE_cleanup(). This approach allows ENGINE_cleanup() to clean up
352 after any ENGINE functionality at all that your program uses, yet
353 doesn't automatically create linker dependencies to all possible ENGINE
354 functionality - only the cleanup callbacks required by the
355 functionality you do use will be required by the linker.
356 The fact that ENGINEs are made visible to OpenSSL (and thus are linked
358 into the program and loaded into memory at run-time) does not mean they
359 are "registered" or called into use by OpenSSL automatically - that
360 behaviour is something for the application to control. Some
361 applications will want to allow the user to specify exactly which
362 ENGINE they want used if any is to be used at all. Others may prefer to
363 load all support and have OpenSSL automatically use at run-time any
364 ENGINE that is able to successfully initialise - ie. to assume that
365 this corresponds to acceleration hardware attached to the machine or
366 some such thing. There are probably numerous other ways in which
367 applications may prefer to handle things, so we will simply illustrate
368 the consequences as they apply to a couple of simple cases and leave
369 developers to consider these and the source code to openssl's builtin
370 utilities as guides.
371 Using a specific ENGINE implementation
373 Here we'll assume an application has been configured by its user or
375 admin to want to use the "ACME" ENGINE if it is available in the
376 version of OpenSSL the application was compiled with. If it is
377 available, it should be used by default for all RSA, DSA, and symmetric
378 cipher operation, otherwise OpenSSL should use its builtin software as
379 per usual. The following code illustrates how to approach this;
380 ENGINE *e;
382 const char *engine_id = "ACME";
383 ENGINE_load_builtin_engines();
384 e = ENGINE_by_id(engine_id);
385 if(!e)
386 /* the engine isn't available */
387 return;
388 if(!ENGINE_init(e)) {
389 /* the engine couldn't initialise, release 'e' */
390 ENGINE_free(e);
391 return;
392 }
393 if(!ENGINE_set_default_RSA(e))
394 /* This should only happen when 'e' can't initialise, but the previous
395 * statement suggests it did. */
396 abort();
397 ENGINE_set_default_DSA(e);
398 ENGINE_set_default_ciphers(e);
399 /* Release the functional reference from ENGINE_init() */
400 ENGINE_finish(e);
401 /* Release the structural reference from ENGINE_by_id() */
402 ENGINE_free(e);
403 Automatically using builtin ENGINE implementations
405 Here we'll assume we want to load and register all ENGINE
407 implementations bundled with OpenSSL, such that for any cryptographic
408 algorithm required by OpenSSL - if there is an ENGINE that implements
409 it and can be initialise, it should be used. The following code
410 illustrates how this can work;
411 /* Load all bundled ENGINEs into memory and make them visible */
413 ENGINE_load_builtin_engines();
414 /* Register all of them for every algorithm they collectively implement */
415 ENGINE_register_all_complete();
416 That's all that's required. Eg. the next time OpenSSL tries to set up
418 an RSA key, any bundled ENGINEs that implement RSA_METHOD will be
419 passed to ENGINE_init() and if any of those succeed, that ENGINE will
420 be set as the default for RSA use from then on.
421 Advanced configuration support
423 There is a mechanism supported by the ENGINE framework that allows each
424 ENGINE implementation to define an arbitrary set of configuration
425 "commands" and expose them to OpenSSL and any applications based on
426 OpenSSL. This mechanism is entirely based on the use of name-value
427 pairs and assumes ASCII input (no unicode or UTF for now!), so it is
428 ideal if applications want to provide a transparent way for users to
429 provide arbitrary configuration "directives" directly to such ENGINEs.
430 It is also possible for the application to dynamically interrogate the
431 loaded ENGINE implementations for the names, descriptions, and input
432 flags of their available "control commands", providing a more flexible
433 configuration scheme. However, if the user is expected to know which
434 ENGINE device he/she is using (in the case of specialised hardware,
435 this goes without saying) then applications may not need to concern
436 themselves with discovering the supported control commands and simply
437 prefer to pass settings into ENGINEs exactly as they are provided by
438 the user.
439 Before illustrating how control commands work, it is worth mentioning
441 what they are typically used for. Broadly speaking there are two uses
442 for control commands; the first is to provide the necessary details to
443 the implementation (which may know nothing at all specific to the host
444 system) so that it can be initialised for use. This could include the
445 path to any driver or config files it needs to load, required network
446 addresses, smart-card identifiers, passwords to initialise protected
447 devices, logging information, etc etc. This class of commands typically
448 needs to be passed to an ENGINE before attempting to initialise it, ie.
449 before calling ENGINE_init(). The other class of commands consist of
450 settings or operations that tweak certain behaviour or cause certain
451 operations to take place, and these commands may work either before or
452 after ENGINE_init(), or in some cases both. ENGINE implementations
453 should provide indications of this in the descriptions attached to
454 builtin control commands and/or in external product documentation.
455 Issuing control commands to an ENGINE
457 Let's illustrate by example; a function for which the caller supplies
459 the name of the ENGINE it wishes to use, a table of string-pairs for
460 use before initialisation, and another table for use after
461 initialisation. Note that the string-pairs used for control commands
462 consist of a command "name" followed by the command "parameter" - the
463 parameter could be NULL in some cases but the name can not. This
464 function should initialise the ENGINE (issuing the "pre" commands
465 beforehand and the "post" commands afterwards) and set it as the
466 default for everything except RAND and then return a boolean success or
467 failure.
468 int generic_load_engine_fn(const char *engine_id,
470 const char **pre_cmds, int pre_num,
471 const char **post_cmds, int post_num)
472 {
473 ENGINE *e = ENGINE_by_id(engine_id);
474 if(!e) return 0;
475 while(pre_num--) {
476 if(!ENGINE_ctrl_cmd_string(e, pre_cmds[0], pre_cmds[1], 0)) {
477 fprintf(stderr, "Failed command (%s - %s:%s)\n", engine_id,
478 pre_cmds[0], pre_cmds[1] ? pre_cmds[1] : "(NULL)");
479 ENGINE_free(e);
480 return 0;
481 }
482 pre_cmds += 2;
483 }
484 if(!ENGINE_init(e)) {
485 fprintf(stderr, "Failed initialisation\n");
486 ENGINE_free(e);
487 return 0;
488 }
489 /* ENGINE_init() returned a functional reference, so free the structural
490 * reference from ENGINE_by_id(). */
491 ENGINE_free(e);
492 while(post_num--) {
493 if(!ENGINE_ctrl_cmd_string(e, post_cmds[0], post_cmds[1], 0)) {
494 fprintf(stderr, "Failed command (%s - %s:%s)\n", engine_id,
495 post_cmds[0], post_cmds[1] ? post_cmds[1] : "(NULL)");
496 ENGINE_finish(e);
497 return 0;
498 }
499 post_cmds += 2;
500 }
501 ENGINE_set_default(e, ENGINE_METHOD_ALL & ~ENGINE_METHOD_RAND);
502 /* Success */
503 return 1;
504 }
505 Note that ENGINE_ctrl_cmd_string() accepts a boolean argument that can
507 relax the semantics of the function - if set non-zero it will only
508 return failure if the ENGINE supported the given command name but
509 failed while executing it, if the ENGINE doesn't support the command
510 name it will simply return success without doing anything. In this case
511 we assume the user is only supplying commands specific to the given
512 ENGINE so we set this to FALSE.
513 Discovering supported control commands
515 It is possible to discover at run-time the names, numerical-ids,
517 descriptions and input parameters of the control commands supported by
518 an ENGINE using a structural reference. Note that some control commands
519 are defined by OpenSSL itself and it will intercept and handle these
520 control commands on behalf of the ENGINE, ie. the ENGINE's ctrl()
521 handler is not used for the control command. openssl/engine.h defines
522 an index, ENGINE_CMD_BASE, that all control commands implemented by
523 ENGINEs should be numbered from. Any command value lower than this
524 symbol is considered a "generic" command is handled directly by the
525 OpenSSL core routines.
526 It is using these "core" control commands that one can discover the the
528 control commands implemented by a given ENGINE, specifically the
529 commands;
530 #define ENGINE_HAS_CTRL_FUNCTION 10
532 #define ENGINE_CTRL_GET_FIRST_CMD_TYPE 11
533 #define ENGINE_CTRL_GET_NEXT_CMD_TYPE 12
534 #define ENGINE_CTRL_GET_CMD_FROM_NAME 13
535 #define ENGINE_CTRL_GET_NAME_LEN_FROM_CMD 14
536 #define ENGINE_CTRL_GET_NAME_FROM_CMD 15
537 #define ENGINE_CTRL_GET_DESC_LEN_FROM_CMD 16
538 #define ENGINE_CTRL_GET_DESC_FROM_CMD 17
539 #define ENGINE_CTRL_GET_CMD_FLAGS 18
540 Whilst these commands are automatically processed by the OpenSSL
542 framework code, they use various properties exposed by each ENGINE to
543 process these queries. An ENGINE has 3 properties it exposes that can
544 affect how this behaves; it can supply a ctrl() handler, it can specify
545 ENGINE_FLAGS_MANUAL_CMD_CTRL in the ENGINE's flags, and it can expose
546 an array of control command descriptions. If an ENGINE specifies the
547 ENGINE_FLAGS_MANUAL_CMD_CTRL flag, then it will simply pass all these
548 "core" control commands directly to the ENGINE's ctrl() handler (and
549 thus, it must have supplied one), so it is up to the ENGINE to reply to
550 these "discovery" commands itself. If that flag is not set, then the
551 OpenSSL framework code will work with the following rules;
552 if no ctrl() handler supplied;
554 ENGINE_HAS_CTRL_FUNCTION returns FALSE (zero),
555 all other commands fail.
556 if a ctrl() handler was supplied but no array of control commands;
557 ENGINE_HAS_CTRL_FUNCTION returns TRUE,
558 all other commands fail.
559 if a ctrl() handler and array of control commands was supplied;
560 ENGINE_HAS_CTRL_FUNCTION returns TRUE,
561 all other commands proceed processing ...
562 If the ENGINE's array of control commands is empty then all other
564 commands will fail, otherwise; ENGINE_CTRL_GET_FIRST_CMD_TYPE returns
565 the identifier of the first command supported by the ENGINE,
566 ENGINE_GET_NEXT_CMD_TYPE takes the identifier of a command supported by
567 the ENGINE and returns the next command identifier or fails if there
568 are no more, ENGINE_CMD_FROM_NAME takes a string name for a command and
569 returns the corresponding identifier or fails if no such command name
570 exists, and the remaining commands take a command identifier and return
571 properties of the corresponding commands. All except
572 ENGINE_CTRL_GET_FLAGS return the string length of a command name or
573 description, or populate a supplied character buffer with a copy of the
574 command name or description. ENGINE_CTRL_GET_FLAGS returns a bitwise-
575 OR'd mask of the following possible values;
576 #define ENGINE_CMD_FLAG_NUMERIC (unsigned int)0x0001
578 #define ENGINE_CMD_FLAG_STRING (unsigned int)0x0002
579 #define ENGINE_CMD_FLAG_NO_INPUT (unsigned int)0x0004
580 #define ENGINE_CMD_FLAG_INTERNAL (unsigned int)0x0008
581 If the ENGINE_CMD_FLAG_INTERNAL flag is set, then any other flags are
583 purely informational to the caller - this flag will prevent the command
584 being usable for any higher-level ENGINE functions such as
585 ENGINE_ctrl_cmd_string(). "INTERNAL" commands are not intended to be
586 exposed to text-based configuration by applications, administrations,
587 users, etc. These can support arbitrary operations via ENGINE_ctrl(),
588 including passing to and/or from the control commands data of any
589 arbitrary type. These commands are supported in the discovery
590 mechanisms simply to allow applications determinie if an ENGINE
591 supports certain specific commands it might want to use (eg.
592 application "foo" might query various ENGINEs to see if they implement
593 "FOO_GET_VENDOR_LOGO_GIF" - and ENGINE could therefore decide whether
594 or not to support this "foo"-specific extension).
595 Future developments
597 The ENGINE API and internal architecture is currently being reviewed.
598 Slated for possible release in 0.9.8 is support for transparent loading
599 of "dynamic" ENGINEs (built as self-contained shared-libraries). This
600 would allow ENGINE implementations to be provided independently of
601 OpenSSL libraries and/or OpenSSL-based applications, and would also
602 remove any requirement for applications to explicitly use the "dynamic"
603 ENGINE to bind to shared-library implementations.
604
606 rsa(3), dsa(3), dh(3), rand(3)
6071.0.1e 2013-02-11 engine(3)