Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / engine.3
CommitLineData
e3261593 1.\" Automatically generated by Pod::Man 2.25 (Pod::Simple 3.19)
8b0cefbb
JR
2.\"
3.\" Standard preamble:
4.\" ========================================================================
8b0cefbb 5.de Sp \" Vertical space (when we can't use .PP)
984263bc
MD
6.if t .sp .5v
7.if n .sp
8..
8b0cefbb 9.de Vb \" Begin verbatim text
984263bc
MD
10.ft CW
11.nf
12.ne \\$1
13..
8b0cefbb 14.de Ve \" End verbatim text
984263bc 15.ft R
984263bc
MD
16.fi
17..
8b0cefbb
JR
18.\" Set up some character translations and predefined strings. \*(-- will
19.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
e257b235
PA
20.\" double quote, and \*(R" will give a right double quote. \*(C+ will
21.\" give a nicer C++. Capital omega is used to do unbreakable dashes and
22.\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
23.\" nothing in troff, for use with C<>.
24.tr \(*W-
8b0cefbb 25.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
984263bc 26.ie n \{\
8b0cefbb
JR
27. ds -- \(*W-
28. ds PI pi
29. if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
30. if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
31. ds L" ""
32. ds R" ""
33. ds C` ""
34. ds C' ""
984263bc
MD
35'br\}
36.el\{\
8b0cefbb
JR
37. ds -- \|\(em\|
38. ds PI \(*p
39. ds L" ``
40. ds R" ''
984263bc 41'br\}
8b0cefbb 42.\"
e257b235
PA
43.\" Escape single quotes in literal strings from groff's Unicode transform.
44.ie \n(.g .ds Aq \(aq
45.el .ds Aq '
46.\"
8b0cefbb 47.\" If the F register is turned on, we'll generate index entries on stderr for
01185282 48.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
8b0cefbb
JR
49.\" entries marked with X<> in POD. Of course, you'll have to process the
50.\" output yourself in some meaningful fashion.
e257b235 51.ie \nF \{\
8b0cefbb
JR
52. de IX
53. tm Index:\\$1\t\\n%\t"\\$2"
984263bc 54..
8b0cefbb
JR
55. nr % 0
56. rr F
984263bc 57.\}
e257b235
PA
58.el \{\
59. de IX
60..
61.\}
aac4ff6f 62.\"
8b0cefbb
JR
63.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
64.\" Fear. Run. Save yourself. No user-serviceable parts.
65. \" fudge factors for nroff and troff
984263bc 66.if n \{\
8b0cefbb
JR
67. ds #H 0
68. ds #V .8m
69. ds #F .3m
70. ds #[ \f1
71. ds #] \fP
984263bc
MD
72.\}
73.if t \{\
8b0cefbb
JR
74. ds #H ((1u-(\\\\n(.fu%2u))*.13m)
75. ds #V .6m
76. ds #F 0
77. ds #[ \&
78. ds #] \&
984263bc 79.\}
8b0cefbb 80. \" simple accents for nroff and troff
984263bc 81.if n \{\
8b0cefbb
JR
82. ds ' \&
83. ds ` \&
84. ds ^ \&
85. ds , \&
86. ds ~ ~
87. ds /
984263bc
MD
88.\}
89.if t \{\
8b0cefbb
JR
90. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
91. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
92. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
93. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
94. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
95. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
984263bc 96.\}
8b0cefbb 97. \" troff and (daisy-wheel) nroff accents
984263bc
MD
98.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
99.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
100.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
101.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
102.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
103.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
104.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
105.ds ae a\h'-(\w'a'u*4/10)'e
106.ds Ae A\h'-(\w'A'u*4/10)'E
8b0cefbb 107. \" corrections for vroff
984263bc
MD
108.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
109.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
8b0cefbb 110. \" for low resolution devices (crt and lpr)
984263bc
MD
111.if \n(.H>23 .if \n(.V>19 \
112\{\
8b0cefbb
JR
113. ds : e
114. ds 8 ss
115. ds o a
116. ds d- d\h'-1'\(ga
117. ds D- D\h'-1'\(hy
118. ds th \o'bp'
119. ds Th \o'LP'
120. ds ae ae
121. ds Ae AE
984263bc
MD
122.\}
123.rm #[ #] #H #V #F C
8b0cefbb
JR
124.\" ========================================================================
125.\"
126.IX Title "engine 3"
e3261593 127.TH engine 3 "2012-01-04" "1.0.0f" "OpenSSL"
e257b235
PA
128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
984263bc 132.SH "NAME"
74dab6c2 133engine \- ENGINE cryptographic module support
984263bc 134.SH "SYNOPSIS"
8b0cefbb 135.IX Header "SYNOPSIS"
984263bc
MD
136.Vb 1
137\& #include <openssl/engine.h>
e257b235 138\&
984263bc
MD
139\& ENGINE *ENGINE_get_first(void);
140\& ENGINE *ENGINE_get_last(void);
141\& ENGINE *ENGINE_get_next(ENGINE *e);
142\& ENGINE *ENGINE_get_prev(ENGINE *e);
e257b235 143\&
984263bc
MD
144\& int ENGINE_add(ENGINE *e);
145\& int ENGINE_remove(ENGINE *e);
e257b235 146\&
984263bc 147\& ENGINE *ENGINE_by_id(const char *id);
e257b235 148\&
984263bc
MD
149\& int ENGINE_init(ENGINE *e);
150\& int ENGINE_finish(ENGINE *e);
e257b235 151\&
984263bc
MD
152\& void ENGINE_load_openssl(void);
153\& void ENGINE_load_dynamic(void);
a561f9ff
SS
154\& #ifndef OPENSSL_NO_STATIC_ENGINE
155\& void ENGINE_load_4758cca(void);
156\& void ENGINE_load_aep(void);
984263bc 157\& void ENGINE_load_atalla(void);
a561f9ff
SS
158\& void ENGINE_load_chil(void);
159\& void ENGINE_load_cswift(void);
160\& void ENGINE_load_gmp(void);
984263bc 161\& void ENGINE_load_nuron(void);
984263bc 162\& void ENGINE_load_sureware(void);
a561f9ff
SS
163\& void ENGINE_load_ubsec(void);
164\& #endif
165\& void ENGINE_load_cryptodev(void);
984263bc 166\& void ENGINE_load_builtin_engines(void);
e257b235 167\&
984263bc 168\& void ENGINE_cleanup(void);
e257b235 169\&
984263bc
MD
170\& ENGINE *ENGINE_get_default_RSA(void);
171\& ENGINE *ENGINE_get_default_DSA(void);
a561f9ff
SS
172\& ENGINE *ENGINE_get_default_ECDH(void);
173\& ENGINE *ENGINE_get_default_ECDSA(void);
984263bc
MD
174\& ENGINE *ENGINE_get_default_DH(void);
175\& ENGINE *ENGINE_get_default_RAND(void);
176\& ENGINE *ENGINE_get_cipher_engine(int nid);
177\& ENGINE *ENGINE_get_digest_engine(int nid);
e257b235 178\&
984263bc
MD
179\& int ENGINE_set_default_RSA(ENGINE *e);
180\& int ENGINE_set_default_DSA(ENGINE *e);
a561f9ff
SS
181\& int ENGINE_set_default_ECDH(ENGINE *e);
182\& int ENGINE_set_default_ECDSA(ENGINE *e);
984263bc
MD
183\& int ENGINE_set_default_DH(ENGINE *e);
184\& int ENGINE_set_default_RAND(ENGINE *e);
185\& int ENGINE_set_default_ciphers(ENGINE *e);
186\& int ENGINE_set_default_digests(ENGINE *e);
187\& int ENGINE_set_default_string(ENGINE *e, const char *list);
e257b235 188\&
984263bc 189\& int ENGINE_set_default(ENGINE *e, unsigned int flags);
e257b235 190\&
984263bc
MD
191\& unsigned int ENGINE_get_table_flags(void);
192\& void ENGINE_set_table_flags(unsigned int flags);
e257b235 193\&
984263bc
MD
194\& int ENGINE_register_RSA(ENGINE *e);
195\& void ENGINE_unregister_RSA(ENGINE *e);
196\& void ENGINE_register_all_RSA(void);
197\& int ENGINE_register_DSA(ENGINE *e);
198\& void ENGINE_unregister_DSA(ENGINE *e);
199\& void ENGINE_register_all_DSA(void);
a561f9ff
SS
200\& int ENGINE_register_ECDH(ENGINE *e);
201\& void ENGINE_unregister_ECDH(ENGINE *e);
202\& void ENGINE_register_all_ECDH(void);
203\& int ENGINE_register_ECDSA(ENGINE *e);
204\& void ENGINE_unregister_ECDSA(ENGINE *e);
205\& void ENGINE_register_all_ECDSA(void);
984263bc
MD
206\& int ENGINE_register_DH(ENGINE *e);
207\& void ENGINE_unregister_DH(ENGINE *e);
208\& void ENGINE_register_all_DH(void);
209\& int ENGINE_register_RAND(ENGINE *e);
210\& void ENGINE_unregister_RAND(ENGINE *e);
211\& void ENGINE_register_all_RAND(void);
a561f9ff
SS
212\& int ENGINE_register_STORE(ENGINE *e);
213\& void ENGINE_unregister_STORE(ENGINE *e);
214\& void ENGINE_register_all_STORE(void);
984263bc
MD
215\& int ENGINE_register_ciphers(ENGINE *e);
216\& void ENGINE_unregister_ciphers(ENGINE *e);
217\& void ENGINE_register_all_ciphers(void);
218\& int ENGINE_register_digests(ENGINE *e);
219\& void ENGINE_unregister_digests(ENGINE *e);
220\& void ENGINE_register_all_digests(void);
221\& int ENGINE_register_complete(ENGINE *e);
222\& int ENGINE_register_all_complete(void);
e257b235 223\&
a561f9ff 224\& int ENGINE_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f)(void));
984263bc
MD
225\& int ENGINE_cmd_is_executable(ENGINE *e, int cmd);
226\& int ENGINE_ctrl_cmd(ENGINE *e, const char *cmd_name,
a561f9ff 227\& long i, void *p, void (*f)(void), int cmd_optional);
984263bc 228\& int ENGINE_ctrl_cmd_string(ENGINE *e, const char *cmd_name, const char *arg,
a561f9ff 229\& int cmd_optional);
e257b235 230\&
984263bc
MD
231\& int ENGINE_set_ex_data(ENGINE *e, int idx, void *arg);
232\& void *ENGINE_get_ex_data(const ENGINE *e, int idx);
e257b235 233\&
984263bc
MD
234\& int ENGINE_get_ex_new_index(long argl, void *argp, CRYPTO_EX_new *new_func,
235\& CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func);
e257b235 236\&
984263bc
MD
237\& ENGINE *ENGINE_new(void);
238\& int ENGINE_free(ENGINE *e);
a561f9ff 239\& int ENGINE_up_ref(ENGINE *e);
e257b235 240\&
984263bc
MD
241\& int ENGINE_set_id(ENGINE *e, const char *id);
242\& int ENGINE_set_name(ENGINE *e, const char *name);
243\& int ENGINE_set_RSA(ENGINE *e, const RSA_METHOD *rsa_meth);
244\& int ENGINE_set_DSA(ENGINE *e, const DSA_METHOD *dsa_meth);
a561f9ff
SS
245\& int ENGINE_set_ECDH(ENGINE *e, const ECDH_METHOD *dh_meth);
246\& int ENGINE_set_ECDSA(ENGINE *e, const ECDSA_METHOD *dh_meth);
984263bc
MD
247\& int ENGINE_set_DH(ENGINE *e, const DH_METHOD *dh_meth);
248\& int ENGINE_set_RAND(ENGINE *e, const RAND_METHOD *rand_meth);
a561f9ff 249\& int ENGINE_set_STORE(ENGINE *e, const STORE_METHOD *rand_meth);
984263bc
MD
250\& int ENGINE_set_destroy_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR destroy_f);
251\& int ENGINE_set_init_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR init_f);
252\& int ENGINE_set_finish_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR finish_f);
253\& int ENGINE_set_ctrl_function(ENGINE *e, ENGINE_CTRL_FUNC_PTR ctrl_f);
254\& int ENGINE_set_load_privkey_function(ENGINE *e, ENGINE_LOAD_KEY_PTR loadpriv_f);
255\& int ENGINE_set_load_pubkey_function(ENGINE *e, ENGINE_LOAD_KEY_PTR loadpub_f);
256\& int ENGINE_set_ciphers(ENGINE *e, ENGINE_CIPHERS_PTR f);
257\& int ENGINE_set_digests(ENGINE *e, ENGINE_DIGESTS_PTR f);
258\& int ENGINE_set_flags(ENGINE *e, int flags);
259\& int ENGINE_set_cmd_defns(ENGINE *e, const ENGINE_CMD_DEFN *defns);
e257b235 260\&
984263bc
MD
261\& const char *ENGINE_get_id(const ENGINE *e);
262\& const char *ENGINE_get_name(const ENGINE *e);
263\& const RSA_METHOD *ENGINE_get_RSA(const ENGINE *e);
264\& const DSA_METHOD *ENGINE_get_DSA(const ENGINE *e);
a561f9ff
SS
265\& const ECDH_METHOD *ENGINE_get_ECDH(const ENGINE *e);
266\& const ECDSA_METHOD *ENGINE_get_ECDSA(const ENGINE *e);
984263bc
MD
267\& const DH_METHOD *ENGINE_get_DH(const ENGINE *e);
268\& const RAND_METHOD *ENGINE_get_RAND(const ENGINE *e);
a561f9ff 269\& const STORE_METHOD *ENGINE_get_STORE(const ENGINE *e);
984263bc
MD
270\& ENGINE_GEN_INT_FUNC_PTR ENGINE_get_destroy_function(const ENGINE *e);
271\& ENGINE_GEN_INT_FUNC_PTR ENGINE_get_init_function(const ENGINE *e);
272\& ENGINE_GEN_INT_FUNC_PTR ENGINE_get_finish_function(const ENGINE *e);
273\& ENGINE_CTRL_FUNC_PTR ENGINE_get_ctrl_function(const ENGINE *e);
274\& ENGINE_LOAD_KEY_PTR ENGINE_get_load_privkey_function(const ENGINE *e);
275\& ENGINE_LOAD_KEY_PTR ENGINE_get_load_pubkey_function(const ENGINE *e);
276\& ENGINE_CIPHERS_PTR ENGINE_get_ciphers(const ENGINE *e);
277\& ENGINE_DIGESTS_PTR ENGINE_get_digests(const ENGINE *e);
278\& const EVP_CIPHER *ENGINE_get_cipher(ENGINE *e, int nid);
279\& const EVP_MD *ENGINE_get_digest(ENGINE *e, int nid);
280\& int ENGINE_get_flags(const ENGINE *e);
281\& const ENGINE_CMD_DEFN *ENGINE_get_cmd_defns(const ENGINE *e);
e257b235 282\&
984263bc
MD
283\& EVP_PKEY *ENGINE_load_private_key(ENGINE *e, const char *key_id,
284\& UI_METHOD *ui_method, void *callback_data);
285\& EVP_PKEY *ENGINE_load_public_key(ENGINE *e, const char *key_id,
286\& UI_METHOD *ui_method, void *callback_data);
e257b235 287\&
984263bc
MD
288\& void ENGINE_add_conf_module(void);
289.Ve
290.SH "DESCRIPTION"
8b0cefbb 291.IX Header "DESCRIPTION"
984263bc 292These functions create, manipulate, and use cryptographic modules in the
8b0cefbb 293form of \fB\s-1ENGINE\s0\fR objects. These objects act as containers for
984263bc
MD
294implementations of cryptographic algorithms, and support a
295reference-counted mechanism to allow them to be dynamically loaded in and
296out of the running application.
297.PP
8b0cefbb 298The cryptographic functionality that can be provided by an \fB\s-1ENGINE\s0\fR
984263bc
MD
299implementation includes the following abstractions;
300.PP
a561f9ff 301.Vb 6
e257b235 302\& RSA_METHOD \- for providing alternative RSA implementations
a561f9ff 303\& DSA_METHOD, DH_METHOD, RAND_METHOD, ECDH_METHOD, ECDSA_METHOD,
e257b235
PA
304\& STORE_METHOD \- similarly for other OpenSSL APIs
305\& EVP_CIPHER \- potentially multiple cipher algorithms (indexed by \*(Aqnid\*(Aq)
306\& EVP_DIGEST \- potentially multiple hash algorithms (indexed by \*(Aqnid\*(Aq)
307\& key\-loading \- loading public and/or private EVP_PKEY keys
984263bc 308.Ve
01185282 309.SS "Reference counting and handles"
8b0cefbb 310.IX Subsection "Reference counting and handles"
984263bc
MD
311Due to the modular nature of the \s-1ENGINE\s0 \s-1API\s0, pointers to ENGINEs need to be
312treated as handles \- ie. not only as pointers, but also as references to
a561f9ff 313the underlying \s-1ENGINE\s0 object. Ie. one should obtain a new reference when
984263bc 314making copies of an \s-1ENGINE\s0 pointer if the copies will be used (and
aac4ff6f 315released) independently.
984263bc 316.PP
8b0cefbb 317\&\s-1ENGINE\s0 objects have two levels of reference-counting to match the way in
984263bc 318which the objects are used. At the most basic level, each \s-1ENGINE\s0 pointer is
a561f9ff
SS
319inherently a \fBstructural\fR reference \- a structural reference is required
320to use the pointer value at all, as this kind of reference is a guarantee
321that the structure can not be deallocated until the reference is released.
322.PP
323However, a structural reference provides no guarantee that the \s-1ENGINE\s0 is
324initiliased and able to use any of its cryptographic
325implementations. Indeed it's quite possible that most ENGINEs will not
326initialise at all in typical environments, as ENGINEs are typically used to
984263bc 327support specialised hardware. To use an \s-1ENGINE\s0's functionality, you need a
8b0cefbb 328\&\fBfunctional\fR reference. This kind of reference can be considered a
984263bc
MD
329specialised form of structural reference, because each functional reference
330implicitly contains a structural reference as well \- however to avoid
331difficult-to-find programming bugs, it is recommended to treat the two
aac4ff6f 332kinds of reference independently. If you have a functional reference to an
8b0cefbb 333\&\s-1ENGINE\s0, you have a guarantee that the \s-1ENGINE\s0 has been initialised ready to
a561f9ff
SS
334perform cryptographic operations and will remain uninitialised
335until after you have released your reference.
984263bc 336.PP
8b0cefbb 337\&\fIStructural references\fR
984263bc 338.PP
a561f9ff
SS
339This basic type of reference is used for instantiating new ENGINEs,
340iterating across OpenSSL's internal linked-list of loaded
984263bc
MD
341ENGINEs, reading information about an \s-1ENGINE\s0, etc. Essentially a structural
342reference is sufficient if you only need to query or manipulate the data of
343an \s-1ENGINE\s0 implementation rather than use its functionality.
344.PP
345The \fIENGINE_new()\fR function returns a structural reference to a new (empty)
a561f9ff
SS
346\&\s-1ENGINE\s0 object. There are other \s-1ENGINE\s0 \s-1API\s0 functions that return structural
347references such as; \fIENGINE_by_id()\fR, \fIENGINE_get_first()\fR, \fIENGINE_get_last()\fR,
348\&\fIENGINE_get_next()\fR, \fIENGINE_get_prev()\fR. All structural references should be
349released by a corresponding to call to the \fIENGINE_free()\fR function \- the
350\&\s-1ENGINE\s0 object itself will only actually be cleaned up and deallocated when
351the last structural reference is released.
984263bc
MD
352.PP
353It should also be noted that many \s-1ENGINE\s0 \s-1API\s0 function calls that accept a
354structural reference will internally obtain another reference \- typically
355this happens whenever the supplied \s-1ENGINE\s0 will be needed by OpenSSL after
356the function has returned. Eg. the function to add a new \s-1ENGINE\s0 to
357OpenSSL's internal list is \fIENGINE_add()\fR \- if this function returns success,
358then OpenSSL will have stored a new structural reference internally so the
359caller is still responsible for freeing their own reference with
8b0cefbb 360\&\fIENGINE_free()\fR when they are finished with it. In a similar way, some
984263bc
MD
361functions will automatically release the structural reference passed to it
362if part of the function's job is to do so. Eg. the \fIENGINE_get_next()\fR and
8b0cefbb
JR
363\&\fIENGINE_get_prev()\fR functions are used for iterating across the internal
364\&\s-1ENGINE\s0 list \- they will return a new structural reference to the next (or
984263bc
MD
365previous) \s-1ENGINE\s0 in the list or \s-1NULL\s0 if at the end (or beginning) of the
366list, but in either case the structural reference passed to the function is
367released on behalf of the caller.
368.PP
369To clarify a particular function's handling of references, one should
370always consult that function's documentation \*(L"man\*(R" page, or failing that
371the openssl/engine.h header file includes some hints.
372.PP
8b0cefbb 373\&\fIFunctional references\fR
984263bc
MD
374.PP
375As mentioned, functional references exist when the cryptographic
376functionality of an \s-1ENGINE\s0 is required to be available. A functional
377reference can be obtained in one of two ways; from an existing structural
378reference to the required \s-1ENGINE\s0, or by asking OpenSSL for the default
379operational \s-1ENGINE\s0 for a given cryptographic purpose.
380.PP
381To obtain a functional reference from an existing structural reference,
382call the \fIENGINE_init()\fR function. This returns zero if the \s-1ENGINE\s0 was not
383already operational and couldn't be successfully initialised (eg. lack of
384system drivers, no special hardware attached, etc), otherwise it will
385return non-zero to indicate that the \s-1ENGINE\s0 is now operational and will
a561f9ff
SS
386have allocated a new \fBfunctional\fR reference to the \s-1ENGINE\s0. All functional
387references are released by calling \fIENGINE_finish()\fR (which removes the
388implicit structural reference as well).
984263bc
MD
389.PP
390The second way to get a functional reference is by asking OpenSSL for a
391default implementation for a given task, eg. by \fIENGINE_get_default_RSA()\fR,
8b0cefbb 392\&\fIENGINE_get_default_cipher_engine()\fR, etc. These are discussed in the next
984263bc
MD
393section, though they are not usually required by application programmers as
394they are used automatically when creating and using the relevant
395algorithm-specific types in OpenSSL, such as \s-1RSA\s0, \s-1DSA\s0, \s-1EVP_CIPHER_CTX\s0, etc.
01185282 396.SS "Default implementations"
8b0cefbb 397.IX Subsection "Default implementations"
984263bc
MD
398For each supported abstraction, the \s-1ENGINE\s0 code maintains an internal table
399of state to control which implementations are available for a given
400abstraction and which should be used by default. These implementations are
a561f9ff 401registered in the tables and indexed by an 'nid' value, because
984263bc 402abstractions like \s-1EVP_CIPHER\s0 and \s-1EVP_DIGEST\s0 support many distinct
a561f9ff
SS
403algorithms and modes, and ENGINEs can support arbitrarily many of them.
404In the case of other abstractions like \s-1RSA\s0, \s-1DSA\s0, etc, there is only one
405\&\*(L"algorithm\*(R" so all implementations implicitly register using the same 'nid'
406index.
407.PP
408When a default \s-1ENGINE\s0 is requested for a given abstraction/algorithm/mode, (eg.
409when calling RSA_new_method(\s-1NULL\s0)), a \*(L"get_default\*(R" call will be made to the
410\&\s-1ENGINE\s0 subsystem to process the corresponding state table and return a
411functional reference to an initialised \s-1ENGINE\s0 whose implementation should be
412used. If no \s-1ENGINE\s0 should (or can) be used, it will return \s-1NULL\s0 and the caller
413will operate with a \s-1NULL\s0 \s-1ENGINE\s0 handle \- this usually equates to using the
414conventional software implementation. In the latter case, OpenSSL will from
415then on behave the way it used to before the \s-1ENGINE\s0 \s-1API\s0 existed.
984263bc
MD
416.PP
417Each state table has a flag to note whether it has processed this
8b0cefbb 418\&\*(L"get_default\*(R" query since the table was last modified, because to process
984263bc
MD
419this question it must iterate across all the registered ENGINEs in the
420table trying to initialise each of them in turn, in case one of them is
421operational. If it returns a functional reference to an \s-1ENGINE\s0, it will
422also cache another reference to speed up processing future queries (without
423needing to iterate across the table). Likewise, it will cache a \s-1NULL\s0
424response if no \s-1ENGINE\s0 was available so that future queries won't repeat the
425same iteration unless the state table changes. This behaviour can also be
426changed; if the \s-1ENGINE_TABLE_FLAG_NOINIT\s0 flag is set (using
8b0cefbb
JR
427\&\fIENGINE_set_table_flags()\fR), no attempted initialisations will take place,
428instead the only way for the state table to return a non-NULL \s-1ENGINE\s0 to the
429\&\*(L"get_default\*(R" query will be if one is expressly set in the table. Eg.
430\&\fIENGINE_set_default_RSA()\fR does the same job as \fIENGINE_register_RSA()\fR except
984263bc 431that it also sets the state table's cached response for the \*(L"get_default\*(R"
a561f9ff
SS
432query. In the case of abstractions like \s-1EVP_CIPHER\s0, where implementations are
433indexed by 'nid', these flags and cached-responses are distinct for each 'nid'
434value.
01185282 435.SS "Application requirements"
8b0cefbb 436.IX Subsection "Application requirements"
984263bc
MD
437This section will explain the basic things an application programmer should
438support to make the most useful elements of the \s-1ENGINE\s0 functionality
439available to the user. The first thing to consider is whether the
440programmer wishes to make alternative \s-1ENGINE\s0 modules available to the
441application and user. OpenSSL maintains an internal linked list of
e257b235 442\&\*(L"visible\*(R" ENGINEs from which it has to operate \- at start-up, this list is
984263bc
MD
443empty and in fact if an application does not call any \s-1ENGINE\s0 \s-1API\s0 calls and
444it uses static linking against openssl, then the resulting application
445binary will not contain any alternative \s-1ENGINE\s0 code at all. So the first
446consideration is whether any/all available \s-1ENGINE\s0 implementations should be
447made visible to OpenSSL \- this is controlled by calling the various \*(L"load\*(R"
448functions, eg.
449.PP
450.Vb 9
451\& /* Make the "dynamic" ENGINE available */
452\& void ENGINE_load_dynamic(void);
453\& /* Make the CryptoSwift hardware acceleration support available */
454\& void ENGINE_load_cswift(void);
e257b235 455\& /* Make support for nCipher\*(Aqs "CHIL" hardware available */
984263bc
MD
456\& void ENGINE_load_chil(void);
457\& ...
458\& /* Make ALL ENGINE implementations bundled with OpenSSL available */
459\& void ENGINE_load_builtin_engines(void);
460.Ve
8b0cefbb 461.PP
984263bc
MD
462Having called any of these functions, \s-1ENGINE\s0 objects would have been
463dynamically allocated and populated with these implementations and linked
464into OpenSSL's internal linked list. At this point it is important to
465mention an important \s-1API\s0 function;
466.PP
467.Vb 1
468\& void ENGINE_cleanup(void);
469.Ve
8b0cefbb 470.PP
984263bc
MD
471If no \s-1ENGINE\s0 \s-1API\s0 functions are called at all in an application, then there
472are no inherent memory leaks to worry about from the \s-1ENGINE\s0 functionality,
a561f9ff 473however if any ENGINEs are loaded, even if they are never registered or
984263bc
MD
474used, it is necessary to use the \fIENGINE_cleanup()\fR function to
475correspondingly cleanup before program exit, if the caller wishes to avoid
476memory leaks. This mechanism uses an internal callback registration table
477so that any \s-1ENGINE\s0 \s-1API\s0 functionality that knows it requires cleanup can
478register its cleanup details to be called during \fIENGINE_cleanup()\fR. This
479approach allows \fIENGINE_cleanup()\fR to clean up after any \s-1ENGINE\s0 functionality
480at all that your program uses, yet doesn't automatically create linker
481dependencies to all possible \s-1ENGINE\s0 functionality \- only the cleanup
482callbacks required by the functionality you do use will be required by the
483linker.
484.PP
485The fact that ENGINEs are made visible to OpenSSL (and thus are linked into
e257b235 486the program and loaded into memory at run-time) does not mean they are
8b0cefbb 487\&\*(L"registered\*(R" or called into use by OpenSSL automatically \- that behaviour
a561f9ff 488is something for the application to control. Some applications
984263bc
MD
489will want to allow the user to specify exactly which \s-1ENGINE\s0 they want used
490if any is to be used at all. Others may prefer to load all support and have
491OpenSSL automatically use at run-time any \s-1ENGINE\s0 that is able to
492successfully initialise \- ie. to assume that this corresponds to
493acceleration hardware attached to the machine or some such thing. There are
494probably numerous other ways in which applications may prefer to handle
495things, so we will simply illustrate the consequences as they apply to a
496couple of simple cases and leave developers to consider these and the
497source code to openssl's builtin utilities as guides.
498.PP
8b0cefbb 499\&\fIUsing a specific \s-1ENGINE\s0 implementation\fR
984263bc
MD
500.PP
501Here we'll assume an application has been configured by its user or admin
502to want to use the \*(L"\s-1ACME\s0\*(R" \s-1ENGINE\s0 if it is available in the version of
503OpenSSL the application was compiled with. If it is available, it should be
504used by default for all \s-1RSA\s0, \s-1DSA\s0, and symmetric cipher operation, otherwise
505OpenSSL should use its builtin software as per usual. The following code
506illustrates how to approach this;
507.PP
e257b235 508.Vb 10
984263bc
MD
509\& ENGINE *e;
510\& const char *engine_id = "ACME";
511\& ENGINE_load_builtin_engines();
512\& e = ENGINE_by_id(engine_id);
513\& if(!e)
e257b235 514\& /* the engine isn\*(Aqt available */
984263bc
MD
515\& return;
516\& if(!ENGINE_init(e)) {
e257b235 517\& /* the engine couldn\*(Aqt initialise, release \*(Aqe\*(Aq */
984263bc
MD
518\& ENGINE_free(e);
519\& return;
520\& }
521\& if(!ENGINE_set_default_RSA(e))
e257b235 522\& /* This should only happen when \*(Aqe\*(Aq can\*(Aqt initialise, but the previous
984263bc
MD
523\& * statement suggests it did. */
524\& abort();
525\& ENGINE_set_default_DSA(e);
526\& ENGINE_set_default_ciphers(e);
527\& /* Release the functional reference from ENGINE_init() */
528\& ENGINE_finish(e);
529\& /* Release the structural reference from ENGINE_by_id() */
530\& ENGINE_free(e);
531.Ve
8b0cefbb
JR
532.PP
533\&\fIAutomatically using builtin \s-1ENGINE\s0 implementations\fR
984263bc
MD
534.PP
535Here we'll assume we want to load and register all \s-1ENGINE\s0 implementations
536bundled with OpenSSL, such that for any cryptographic algorithm required by
537OpenSSL \- if there is an \s-1ENGINE\s0 that implements it and can be initialise,
538it should be used. The following code illustrates how this can work;
539.PP
540.Vb 4
541\& /* Load all bundled ENGINEs into memory and make them visible */
542\& ENGINE_load_builtin_engines();
543\& /* Register all of them for every algorithm they collectively implement */
544\& ENGINE_register_all_complete();
545.Ve
8b0cefbb 546.PP
984263bc 547That's all that's required. Eg. the next time OpenSSL tries to set up an
8b0cefbb
JR
548\&\s-1RSA\s0 key, any bundled ENGINEs that implement \s-1RSA_METHOD\s0 will be passed to
549\&\fIENGINE_init()\fR and if any of those succeed, that \s-1ENGINE\s0 will be set as the
a561f9ff 550default for \s-1RSA\s0 use from then on.
01185282 551.SS "Advanced configuration support"
8b0cefbb 552.IX Subsection "Advanced configuration support"
984263bc 553There is a mechanism supported by the \s-1ENGINE\s0 framework that allows each
8b0cefbb
JR
554\&\s-1ENGINE\s0 implementation to define an arbitrary set of configuration
555\&\*(L"commands\*(R" and expose them to OpenSSL and any applications based on
984263bc 556OpenSSL. This mechanism is entirely based on the use of name-value pairs
a561f9ff 557and assumes \s-1ASCII\s0 input (no unicode or \s-1UTF\s0 for now!), so it is ideal if
984263bc
MD
558applications want to provide a transparent way for users to provide
559arbitrary configuration \*(L"directives\*(R" directly to such ENGINEs. It is also
560possible for the application to dynamically interrogate the loaded \s-1ENGINE\s0
561implementations for the names, descriptions, and input flags of their
562available \*(L"control commands\*(R", providing a more flexible configuration
563scheme. However, if the user is expected to know which \s-1ENGINE\s0 device he/she
564is using (in the case of specialised hardware, this goes without saying)
565then applications may not need to concern themselves with discovering the
a561f9ff
SS
566supported control commands and simply prefer to pass settings into ENGINEs
567exactly as they are provided by the user.
984263bc
MD
568.PP
569Before illustrating how control commands work, it is worth mentioning what
570they are typically used for. Broadly speaking there are two uses for
571control commands; the first is to provide the necessary details to the
572implementation (which may know nothing at all specific to the host system)
573so that it can be initialised for use. This could include the path to any
574driver or config files it needs to load, required network addresses,
a561f9ff 575smart-card identifiers, passwords to initialise protected devices,
984263bc
MD
576logging information, etc etc. This class of commands typically needs to be
577passed to an \s-1ENGINE\s0 \fBbefore\fR attempting to initialise it, ie. before
578calling \fIENGINE_init()\fR. The other class of commands consist of settings or
579operations that tweak certain behaviour or cause certain operations to take
580place, and these commands may work either before or after \fIENGINE_init()\fR, or
a561f9ff 581in some cases both. \s-1ENGINE\s0 implementations should provide indications of
984263bc
MD
582this in the descriptions attached to builtin control commands and/or in
583external product documentation.
584.PP
8b0cefbb 585\&\fIIssuing control commands to an \s-1ENGINE\s0\fR
984263bc
MD
586.PP
587Let's illustrate by example; a function for which the caller supplies the
588name of the \s-1ENGINE\s0 it wishes to use, a table of string-pairs for use before
589initialisation, and another table for use after initialisation. Note that
590the string-pairs used for control commands consist of a command \*(L"name\*(R"
591followed by the command \*(L"parameter\*(R" \- the parameter could be \s-1NULL\s0 in some
592cases but the name can not. This function should initialise the \s-1ENGINE\s0
593(issuing the \*(L"pre\*(R" commands beforehand and the \*(L"post\*(R" commands afterwards)
594and set it as the default for everything except \s-1RAND\s0 and then return a
595boolean success or failure.
596.PP
e257b235 597.Vb 10
984263bc
MD
598\& int generic_load_engine_fn(const char *engine_id,
599\& const char **pre_cmds, int pre_num,
600\& const char **post_cmds, int post_num)
601\& {
602\& ENGINE *e = ENGINE_by_id(engine_id);
603\& if(!e) return 0;
e257b235 604\& while(pre_num\-\-) {
984263bc 605\& if(!ENGINE_ctrl_cmd_string(e, pre_cmds[0], pre_cmds[1], 0)) {
e257b235 606\& fprintf(stderr, "Failed command (%s \- %s:%s)\en", engine_id,
984263bc
MD
607\& pre_cmds[0], pre_cmds[1] ? pre_cmds[1] : "(NULL)");
608\& ENGINE_free(e);
609\& return 0;
610\& }
611\& pre_cmds += 2;
612\& }
613\& if(!ENGINE_init(e)) {
614\& fprintf(stderr, "Failed initialisation\en");
615\& ENGINE_free(e);
616\& return 0;
617\& }
618\& /* ENGINE_init() returned a functional reference, so free the structural
619\& * reference from ENGINE_by_id(). */
620\& ENGINE_free(e);
e257b235 621\& while(post_num\-\-) {
984263bc 622\& if(!ENGINE_ctrl_cmd_string(e, post_cmds[0], post_cmds[1], 0)) {
e257b235 623\& fprintf(stderr, "Failed command (%s \- %s:%s)\en", engine_id,
984263bc
MD
624\& post_cmds[0], post_cmds[1] ? post_cmds[1] : "(NULL)");
625\& ENGINE_finish(e);
626\& return 0;
627\& }
628\& post_cmds += 2;
629\& }
630\& ENGINE_set_default(e, ENGINE_METHOD_ALL & ~ENGINE_METHOD_RAND);
631\& /* Success */
632\& return 1;
633\& }
634.Ve
8b0cefbb 635.PP
984263bc
MD
636Note that \fIENGINE_ctrl_cmd_string()\fR accepts a boolean argument that can
637relax the semantics of the function \- if set non-zero it will only return
638failure if the \s-1ENGINE\s0 supported the given command name but failed while
639executing it, if the \s-1ENGINE\s0 doesn't support the command name it will simply
640return success without doing anything. In this case we assume the user is
641only supplying commands specific to the given \s-1ENGINE\s0 so we set this to
8b0cefbb 642\&\s-1FALSE\s0.
984263bc 643.PP
8b0cefbb 644\&\fIDiscovering supported control commands\fR
984263bc 645.PP
e257b235 646It is possible to discover at run-time the names, numerical-ids, descriptions
a561f9ff
SS
647and input parameters of the control commands supported by an \s-1ENGINE\s0 using a
648structural reference. Note that some control commands are defined by OpenSSL
649itself and it will intercept and handle these control commands on behalf of the
650\&\s-1ENGINE\s0, ie. the \s-1ENGINE\s0's \fIctrl()\fR handler is not used for the control command.
651openssl/engine.h defines an index, \s-1ENGINE_CMD_BASE\s0, that all control commands
652implemented by ENGINEs should be numbered from. Any command value lower than
653this symbol is considered a \*(L"generic\*(R" command is handled directly by the
654OpenSSL core routines.
984263bc
MD
655.PP
656It is using these \*(L"core\*(R" control commands that one can discover the the control
657commands implemented by a given \s-1ENGINE\s0, specifically the commands;
658.PP
659.Vb 9
660\& #define ENGINE_HAS_CTRL_FUNCTION 10
661\& #define ENGINE_CTRL_GET_FIRST_CMD_TYPE 11
662\& #define ENGINE_CTRL_GET_NEXT_CMD_TYPE 12
663\& #define ENGINE_CTRL_GET_CMD_FROM_NAME 13
664\& #define ENGINE_CTRL_GET_NAME_LEN_FROM_CMD 14
665\& #define ENGINE_CTRL_GET_NAME_FROM_CMD 15
666\& #define ENGINE_CTRL_GET_DESC_LEN_FROM_CMD 16
667\& #define ENGINE_CTRL_GET_DESC_FROM_CMD 17
668\& #define ENGINE_CTRL_GET_CMD_FLAGS 18
669.Ve
8b0cefbb 670.PP
984263bc 671Whilst these commands are automatically processed by the OpenSSL framework code,
a561f9ff
SS
672they use various properties exposed by each \s-1ENGINE\s0 to process these
673queries. An \s-1ENGINE\s0 has 3 properties it exposes that can affect how this behaves;
984263bc
MD
674it can supply a \fIctrl()\fR handler, it can specify \s-1ENGINE_FLAGS_MANUAL_CMD_CTRL\s0 in
675the \s-1ENGINE\s0's flags, and it can expose an array of control command descriptions.
676If an \s-1ENGINE\s0 specifies the \s-1ENGINE_FLAGS_MANUAL_CMD_CTRL\s0 flag, then it will
677simply pass all these \*(L"core\*(R" control commands directly to the \s-1ENGINE\s0's \fIctrl()\fR
678handler (and thus, it must have supplied one), so it is up to the \s-1ENGINE\s0 to
679reply to these \*(L"discovery\*(R" commands itself. If that flag is not set, then the
680OpenSSL framework code will work with the following rules;
681.PP
682.Vb 9
683\& if no ctrl() handler supplied;
684\& ENGINE_HAS_CTRL_FUNCTION returns FALSE (zero),
685\& all other commands fail.
686\& if a ctrl() handler was supplied but no array of control commands;
687\& ENGINE_HAS_CTRL_FUNCTION returns TRUE,
688\& all other commands fail.
689\& if a ctrl() handler and array of control commands was supplied;
690\& ENGINE_HAS_CTRL_FUNCTION returns TRUE,
691\& all other commands proceed processing ...
692.Ve
8b0cefbb 693.PP
984263bc
MD
694If the \s-1ENGINE\s0's array of control commands is empty then all other commands will
695fail, otherwise; \s-1ENGINE_CTRL_GET_FIRST_CMD_TYPE\s0 returns the identifier of
696the first command supported by the \s-1ENGINE\s0, \s-1ENGINE_GET_NEXT_CMD_TYPE\s0 takes the
697identifier of a command supported by the \s-1ENGINE\s0 and returns the next command
698identifier or fails if there are no more, \s-1ENGINE_CMD_FROM_NAME\s0 takes a string
699name for a command and returns the corresponding identifier or fails if no such
700command name exists, and the remaining commands take a command identifier and
701return properties of the corresponding commands. All except
8b0cefbb 702\&\s-1ENGINE_CTRL_GET_FLAGS\s0 return the string length of a command name or description,
984263bc 703or populate a supplied character buffer with a copy of the command name or
e257b235 704description. \s-1ENGINE_CTRL_GET_FLAGS\s0 returns a bitwise-OR'd mask of the following
984263bc
MD
705possible values;
706.PP
707.Vb 4
708\& #define ENGINE_CMD_FLAG_NUMERIC (unsigned int)0x0001
709\& #define ENGINE_CMD_FLAG_STRING (unsigned int)0x0002
710\& #define ENGINE_CMD_FLAG_NO_INPUT (unsigned int)0x0004
711\& #define ENGINE_CMD_FLAG_INTERNAL (unsigned int)0x0008
712.Ve
8b0cefbb 713.PP
984263bc
MD
714If the \s-1ENGINE_CMD_FLAG_INTERNAL\s0 flag is set, then any other flags are purely
715informational to the caller \- this flag will prevent the command being usable
716for any higher-level \s-1ENGINE\s0 functions such as \fIENGINE_ctrl_cmd_string()\fR.
8b0cefbb 717\&\*(L"\s-1INTERNAL\s0\*(R" commands are not intended to be exposed to text-based configuration
984263bc
MD
718by applications, administrations, users, etc. These can support arbitrary
719operations via \fIENGINE_ctrl()\fR, including passing to and/or from the control
720commands data of any arbitrary type. These commands are supported in the
721discovery mechanisms simply to allow applications determinie if an \s-1ENGINE\s0
722supports certain specific commands it might want to use (eg. application \*(L"foo\*(R"
723might query various ENGINEs to see if they implement \*(L"\s-1FOO_GET_VENDOR_LOGO_GIF\s0\*(R" \-
724and \s-1ENGINE\s0 could therefore decide whether or not to support this \*(L"foo\*(R"\-specific
725extension).
01185282 726.SS "Future developments"
8b0cefbb 727.IX Subsection "Future developments"
984263bc
MD
728The \s-1ENGINE\s0 \s-1API\s0 and internal architecture is currently being reviewed. Slated for
729possible release in 0.9.8 is support for transparent loading of \*(L"dynamic\*(R"
e257b235 730ENGINEs (built as self-contained shared-libraries). This would allow \s-1ENGINE\s0
aac4ff6f 731implementations to be provided independently of OpenSSL libraries and/or
8b0cefbb 732OpenSSL-based applications, and would also remove any requirement for
984263bc
MD
733applications to explicitly use the \*(L"dynamic\*(R" \s-1ENGINE\s0 to bind to shared-library
734implementations.
735.SH "SEE ALSO"
74dab6c2 736.IX Header "SEE ALSO"
a561f9ff 737\&\fIrsa\fR\|(3), \fIdsa\fR\|(3), \fIdh\fR\|(3), \fIrand\fR\|(3)