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Diffstat (limited to 'doc/crypto/engine.pod')
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diff --git a/doc/crypto/engine.pod b/doc/crypto/engine.pod deleted file mode 100644 index 48741ee30629..000000000000 --- a/doc/crypto/engine.pod +++ /dev/null @@ -1,599 +0,0 @@ -=pod - -=head1 NAME - -engine - ENGINE cryptographic module support - -=head1 SYNOPSIS - - #include <openssl/engine.h> - - ENGINE *ENGINE_get_first(void); - ENGINE *ENGINE_get_last(void); - ENGINE *ENGINE_get_next(ENGINE *e); - ENGINE *ENGINE_get_prev(ENGINE *e); - - int ENGINE_add(ENGINE *e); - int ENGINE_remove(ENGINE *e); - - ENGINE *ENGINE_by_id(const char *id); - - int ENGINE_init(ENGINE *e); - int ENGINE_finish(ENGINE *e); - - void ENGINE_load_openssl(void); - void ENGINE_load_dynamic(void); - #ifndef OPENSSL_NO_STATIC_ENGINE - void ENGINE_load_4758cca(void); - void ENGINE_load_aep(void); - void ENGINE_load_atalla(void); - void ENGINE_load_chil(void); - void ENGINE_load_cswift(void); - void ENGINE_load_gmp(void); - void ENGINE_load_nuron(void); - void ENGINE_load_sureware(void); - void ENGINE_load_ubsec(void); - #endif - void ENGINE_load_cryptodev(void); - void ENGINE_load_builtin_engines(void); - - void ENGINE_cleanup(void); - - ENGINE *ENGINE_get_default_RSA(void); - ENGINE *ENGINE_get_default_DSA(void); - ENGINE *ENGINE_get_default_ECDH(void); - ENGINE *ENGINE_get_default_ECDSA(void); - ENGINE *ENGINE_get_default_DH(void); - ENGINE *ENGINE_get_default_RAND(void); - ENGINE *ENGINE_get_cipher_engine(int nid); - ENGINE *ENGINE_get_digest_engine(int nid); - - int ENGINE_set_default_RSA(ENGINE *e); - int ENGINE_set_default_DSA(ENGINE *e); - int ENGINE_set_default_ECDH(ENGINE *e); - int ENGINE_set_default_ECDSA(ENGINE *e); - int ENGINE_set_default_DH(ENGINE *e); - int ENGINE_set_default_RAND(ENGINE *e); - int ENGINE_set_default_ciphers(ENGINE *e); - int ENGINE_set_default_digests(ENGINE *e); - int ENGINE_set_default_string(ENGINE *e, const char *list); - - int ENGINE_set_default(ENGINE *e, unsigned int flags); - - unsigned int ENGINE_get_table_flags(void); - void ENGINE_set_table_flags(unsigned int flags); - - int ENGINE_register_RSA(ENGINE *e); - void ENGINE_unregister_RSA(ENGINE *e); - void ENGINE_register_all_RSA(void); - int ENGINE_register_DSA(ENGINE *e); - void ENGINE_unregister_DSA(ENGINE *e); - void ENGINE_register_all_DSA(void); - int ENGINE_register_ECDH(ENGINE *e); - void ENGINE_unregister_ECDH(ENGINE *e); - void ENGINE_register_all_ECDH(void); - int ENGINE_register_ECDSA(ENGINE *e); - void ENGINE_unregister_ECDSA(ENGINE *e); - void ENGINE_register_all_ECDSA(void); - int ENGINE_register_DH(ENGINE *e); - void ENGINE_unregister_DH(ENGINE *e); - void ENGINE_register_all_DH(void); - int ENGINE_register_RAND(ENGINE *e); - void ENGINE_unregister_RAND(ENGINE *e); - void ENGINE_register_all_RAND(void); - int ENGINE_register_STORE(ENGINE *e); - void ENGINE_unregister_STORE(ENGINE *e); - void ENGINE_register_all_STORE(void); - int ENGINE_register_ciphers(ENGINE *e); - void ENGINE_unregister_ciphers(ENGINE *e); - void ENGINE_register_all_ciphers(void); - int ENGINE_register_digests(ENGINE *e); - void ENGINE_unregister_digests(ENGINE *e); - void ENGINE_register_all_digests(void); - int ENGINE_register_complete(ENGINE *e); - int ENGINE_register_all_complete(void); - - int ENGINE_ctrl(ENGINE *e, int cmd, long i, void *p, void (*f)(void)); - int ENGINE_cmd_is_executable(ENGINE *e, int cmd); - int ENGINE_ctrl_cmd(ENGINE *e, const char *cmd_name, - long i, void *p, void (*f)(void), int cmd_optional); - int ENGINE_ctrl_cmd_string(ENGINE *e, const char *cmd_name, const char *arg, - int cmd_optional); - - int ENGINE_set_ex_data(ENGINE *e, int idx, void *arg); - void *ENGINE_get_ex_data(const ENGINE *e, int idx); - - int ENGINE_get_ex_new_index(long argl, void *argp, CRYPTO_EX_new *new_func, - CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func); - - ENGINE *ENGINE_new(void); - int ENGINE_free(ENGINE *e); - int ENGINE_up_ref(ENGINE *e); - - int ENGINE_set_id(ENGINE *e, const char *id); - int ENGINE_set_name(ENGINE *e, const char *name); - int ENGINE_set_RSA(ENGINE *e, const RSA_METHOD *rsa_meth); - int ENGINE_set_DSA(ENGINE *e, const DSA_METHOD *dsa_meth); - int ENGINE_set_ECDH(ENGINE *e, const ECDH_METHOD *dh_meth); - int ENGINE_set_ECDSA(ENGINE *e, const ECDSA_METHOD *dh_meth); - int ENGINE_set_DH(ENGINE *e, const DH_METHOD *dh_meth); - int ENGINE_set_RAND(ENGINE *e, const RAND_METHOD *rand_meth); - int ENGINE_set_STORE(ENGINE *e, const STORE_METHOD *rand_meth); - int ENGINE_set_destroy_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR destroy_f); - int ENGINE_set_init_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR init_f); - int ENGINE_set_finish_function(ENGINE *e, ENGINE_GEN_INT_FUNC_PTR finish_f); - int ENGINE_set_ctrl_function(ENGINE *e, ENGINE_CTRL_FUNC_PTR ctrl_f); - int ENGINE_set_load_privkey_function(ENGINE *e, ENGINE_LOAD_KEY_PTR loadpriv_f); - int ENGINE_set_load_pubkey_function(ENGINE *e, ENGINE_LOAD_KEY_PTR loadpub_f); - int ENGINE_set_ciphers(ENGINE *e, ENGINE_CIPHERS_PTR f); - int ENGINE_set_digests(ENGINE *e, ENGINE_DIGESTS_PTR f); - int ENGINE_set_flags(ENGINE *e, int flags); - int ENGINE_set_cmd_defns(ENGINE *e, const ENGINE_CMD_DEFN *defns); - - const char *ENGINE_get_id(const ENGINE *e); - const char *ENGINE_get_name(const ENGINE *e); - const RSA_METHOD *ENGINE_get_RSA(const ENGINE *e); - const DSA_METHOD *ENGINE_get_DSA(const ENGINE *e); - const ECDH_METHOD *ENGINE_get_ECDH(const ENGINE *e); - const ECDSA_METHOD *ENGINE_get_ECDSA(const ENGINE *e); - const DH_METHOD *ENGINE_get_DH(const ENGINE *e); - const RAND_METHOD *ENGINE_get_RAND(const ENGINE *e); - const STORE_METHOD *ENGINE_get_STORE(const ENGINE *e); - ENGINE_GEN_INT_FUNC_PTR ENGINE_get_destroy_function(const ENGINE *e); - ENGINE_GEN_INT_FUNC_PTR ENGINE_get_init_function(const ENGINE *e); - ENGINE_GEN_INT_FUNC_PTR ENGINE_get_finish_function(const ENGINE *e); - ENGINE_CTRL_FUNC_PTR ENGINE_get_ctrl_function(const ENGINE *e); - ENGINE_LOAD_KEY_PTR ENGINE_get_load_privkey_function(const ENGINE *e); - ENGINE_LOAD_KEY_PTR ENGINE_get_load_pubkey_function(const ENGINE *e); - ENGINE_CIPHERS_PTR ENGINE_get_ciphers(const ENGINE *e); - ENGINE_DIGESTS_PTR ENGINE_get_digests(const ENGINE *e); - const EVP_CIPHER *ENGINE_get_cipher(ENGINE *e, int nid); - const EVP_MD *ENGINE_get_digest(ENGINE *e, int nid); - int ENGINE_get_flags(const ENGINE *e); - const ENGINE_CMD_DEFN *ENGINE_get_cmd_defns(const ENGINE *e); - - EVP_PKEY *ENGINE_load_private_key(ENGINE *e, const char *key_id, - UI_METHOD *ui_method, void *callback_data); - EVP_PKEY *ENGINE_load_public_key(ENGINE *e, const char *key_id, - UI_METHOD *ui_method, void *callback_data); - - void ENGINE_add_conf_module(void); - -=head1 DESCRIPTION - -These functions create, manipulate, and use cryptographic modules in the -form of B<ENGINE> objects. These objects act as containers for -implementations of cryptographic algorithms, and support a -reference-counted mechanism to allow them to be dynamically loaded in and -out of the running application. - -The cryptographic functionality that can be provided by an B<ENGINE> -implementation includes the following abstractions; - - RSA_METHOD - for providing alternative RSA implementations - DSA_METHOD, DH_METHOD, RAND_METHOD, ECDH_METHOD, ECDSA_METHOD, - STORE_METHOD - similarly for other OpenSSL APIs - EVP_CIPHER - potentially multiple cipher algorithms (indexed by 'nid') - EVP_DIGEST - potentially multiple hash algorithms (indexed by 'nid') - key-loading - loading public and/or private EVP_PKEY keys - -=head2 Reference counting and handles - -Due to the modular nature of the ENGINE API, pointers to ENGINEs need to be -treated as handles - ie. not only as pointers, but also as references to -the underlying ENGINE object. Ie. one should obtain a new reference when -making copies of an ENGINE pointer if the copies will be used (and -released) independently. - -ENGINE objects have two levels of reference-counting to match the way in -which the objects are used. At the most basic level, each ENGINE pointer is -inherently a B<structural> reference - a structural reference is required -to use the pointer value at all, as this kind of reference is a guarantee -that the structure can not be deallocated until the reference is released. - -However, a structural reference provides no guarantee that the ENGINE is -initialised and able to use any of its cryptographic -implementations. Indeed it's quite possible that most ENGINEs will not -initialise at all in typical environments, as ENGINEs are typically used to -support specialised hardware. To use an ENGINE's functionality, you need a -B<functional> reference. This kind of reference can be considered a -specialised form of structural reference, because each functional reference -implicitly contains a structural reference as well - however to avoid -difficult-to-find programming bugs, it is recommended to treat the two -kinds of reference independently. If you have a functional reference to an -ENGINE, you have a guarantee that the ENGINE has been initialised and -is ready to perform cryptographic operations, and will remain initialised -until after you have released your reference. - -I<Structural references> - -This basic type of reference is used for instantiating new ENGINEs, -iterating across OpenSSL's internal linked-list of loaded -ENGINEs, reading information about an ENGINE, etc. Essentially a structural -reference is sufficient if you only need to query or manipulate the data of -an ENGINE implementation rather than use its functionality. - -The ENGINE_new() function returns a structural reference to a new (empty) -ENGINE object. There are other ENGINE API functions that return structural -references such as; ENGINE_by_id(), ENGINE_get_first(), ENGINE_get_last(), -ENGINE_get_next(), ENGINE_get_prev(). All structural references should be -released by a corresponding to call to the ENGINE_free() function - the -ENGINE object itself will only actually be cleaned up and deallocated when -the last structural reference is released. - -It should also be noted that many ENGINE API function calls that accept a -structural reference will internally obtain another reference - typically -this happens whenever the supplied ENGINE will be needed by OpenSSL after -the function has returned. Eg. the function to add a new ENGINE to -OpenSSL's internal list is ENGINE_add() - if this function returns success, -then OpenSSL will have stored a new structural reference internally so the -caller is still responsible for freeing their own reference with -ENGINE_free() when they are finished with it. In a similar way, some -functions will automatically release the structural reference passed to it -if part of the function's job is to do so. Eg. the ENGINE_get_next() and -ENGINE_get_prev() functions are used for iterating across the internal -ENGINE list - they will return a new structural reference to the next (or -previous) ENGINE in the list or NULL if at the end (or beginning) of the -list, but in either case the structural reference passed to the function is -released on behalf of the caller. - -To clarify a particular function's handling of references, one should -always consult that function's documentation "man" page, or failing that -the openssl/engine.h header file includes some hints. - -I<Functional references> - -As mentioned, functional references exist when the cryptographic -functionality of an ENGINE is required to be available. A functional -reference can be obtained in one of two ways; from an existing structural -reference to the required ENGINE, or by asking OpenSSL for the default -operational ENGINE for a given cryptographic purpose. - -To obtain a functional reference from an existing structural reference, -call the ENGINE_init() function. This returns zero if the ENGINE was not -already operational and couldn't be successfully initialised (eg. lack of -system drivers, no special hardware attached, etc), otherwise it will -return non-zero to indicate that the ENGINE is now operational and will -have allocated a new B<functional> reference to the ENGINE. All functional -references are released by calling ENGINE_finish() (which removes the -implicit structural reference as well). - -The second way to get a functional reference is by asking OpenSSL for a -default implementation for a given task, eg. by ENGINE_get_default_RSA(), -ENGINE_get_default_cipher_engine(), etc. These are discussed in the next -section, though they are not usually required by application programmers as -they are used automatically when creating and using the relevant -algorithm-specific types in OpenSSL, such as RSA, DSA, EVP_CIPHER_CTX, etc. - -=head2 Default implementations - -For each supported abstraction, the ENGINE code maintains an internal table -of state to control which implementations are available for a given -abstraction and which should be used by default. These implementations are -registered in the tables and indexed by an 'nid' value, because -abstractions like EVP_CIPHER and EVP_DIGEST support many distinct -algorithms and modes, and ENGINEs can support arbitrarily many of them. -In the case of other abstractions like RSA, DSA, etc, there is only one -"algorithm" so all implementations implicitly register using the same 'nid' -index. - -When a default ENGINE is requested for a given abstraction/algorithm/mode, (eg. -when calling RSA_new_method(NULL)), a "get_default" call will be made to the -ENGINE subsystem to process the corresponding state table and return a -functional reference to an initialised ENGINE whose implementation should be -used. If no ENGINE should (or can) be used, it will return NULL and the caller -will operate with a NULL ENGINE handle - this usually equates to using the -conventional software implementation. In the latter case, OpenSSL will from -then on behave the way it used to before the ENGINE API existed. - -Each state table has a flag to note whether it has processed this -"get_default" query since the table was last modified, because to process -this question it must iterate across all the registered ENGINEs in the -table trying to initialise each of them in turn, in case one of them is -operational. If it returns a functional reference to an ENGINE, it will -also cache another reference to speed up processing future queries (without -needing to iterate across the table). Likewise, it will cache a NULL -response if no ENGINE was available so that future queries won't repeat the -same iteration unless the state table changes. This behaviour can also be -changed; if the ENGINE_TABLE_FLAG_NOINIT flag is set (using -ENGINE_set_table_flags()), no attempted initialisations will take place, -instead the only way for the state table to return a non-NULL ENGINE to the -"get_default" query will be if one is expressly set in the table. Eg. -ENGINE_set_default_RSA() does the same job as ENGINE_register_RSA() except -that it also sets the state table's cached response for the "get_default" -query. In the case of abstractions like EVP_CIPHER, where implementations are -indexed by 'nid', these flags and cached-responses are distinct for each 'nid' -value. - -=head2 Application requirements - -This section will explain the basic things an application programmer should -support to make the most useful elements of the ENGINE functionality -available to the user. The first thing to consider is whether the -programmer wishes to make alternative ENGINE modules available to the -application and user. OpenSSL maintains an internal linked list of -"visible" ENGINEs from which it has to operate - at start-up, this list is -empty and in fact if an application does not call any ENGINE API calls and -it uses static linking against openssl, then the resulting application -binary will not contain any alternative ENGINE code at all. So the first -consideration is whether any/all available ENGINE implementations should be -made visible to OpenSSL - this is controlled by calling the various "load" -functions, eg. - - /* Make the "dynamic" ENGINE available */ - void ENGINE_load_dynamic(void); - /* Make the CryptoSwift hardware acceleration support available */ - void ENGINE_load_cswift(void); - /* Make support for nCipher's "CHIL" hardware available */ - void ENGINE_load_chil(void); - ... - /* Make ALL ENGINE implementations bundled with OpenSSL available */ - void ENGINE_load_builtin_engines(void); - -Having called any of these functions, ENGINE objects would have been -dynamically allocated and populated with these implementations and linked -into OpenSSL's internal linked list. At this point it is important to -mention an important API function; - - void ENGINE_cleanup(void); - -If no ENGINE API functions are called at all in an application, then there -are no inherent memory leaks to worry about from the ENGINE functionality, -however if any ENGINEs are loaded, even if they are never registered or -used, it is necessary to use the ENGINE_cleanup() function to -correspondingly cleanup before program exit, if the caller wishes to avoid -memory leaks. This mechanism uses an internal callback registration table -so that any ENGINE API functionality that knows it requires cleanup can -register its cleanup details to be called during ENGINE_cleanup(). This -approach allows ENGINE_cleanup() to clean up after any ENGINE functionality -at all that your program uses, yet doesn't automatically create linker -dependencies to all possible ENGINE functionality - only the cleanup -callbacks required by the functionality you do use will be required by the -linker. - -The fact that ENGINEs are made visible to OpenSSL (and thus are linked into -the program and loaded into memory at run-time) does not mean they are -"registered" or called into use by OpenSSL automatically - that behaviour -is something for the application to control. Some applications -will want to allow the user to specify exactly which ENGINE they want used -if any is to be used at all. Others may prefer to load all support and have -OpenSSL automatically use at run-time any ENGINE that is able to -successfully initialise - ie. to assume that this corresponds to -acceleration hardware attached to the machine or some such thing. There are -probably numerous other ways in which applications may prefer to handle -things, so we will simply illustrate the consequences as they apply to a -couple of simple cases and leave developers to consider these and the -source code to openssl's builtin utilities as guides. - -I<Using a specific ENGINE implementation> - -Here we'll assume an application has been configured by its user or admin -to want to use the "ACME" ENGINE if it is available in the version of -OpenSSL the application was compiled with. If it is available, it should be -used by default for all RSA, DSA, and symmetric cipher operations, otherwise -OpenSSL should use its builtin software as per usual. The following code -illustrates how to approach this; - - ENGINE *e; - const char *engine_id = "ACME"; - ENGINE_load_builtin_engines(); - e = ENGINE_by_id(engine_id); - if(!e) - /* the engine isn't available */ - return; - if(!ENGINE_init(e)) { - /* the engine couldn't initialise, release 'e' */ - ENGINE_free(e); - return; - } - if(!ENGINE_set_default_RSA(e)) - /* This should only happen when 'e' can't initialise, but the previous - * statement suggests it did. */ - abort(); - ENGINE_set_default_DSA(e); - ENGINE_set_default_ciphers(e); - /* Release the functional reference from ENGINE_init() */ - ENGINE_finish(e); - /* Release the structural reference from ENGINE_by_id() */ - ENGINE_free(e); - -I<Automatically using builtin ENGINE implementations> - -Here we'll assume we want to load and register all ENGINE implementations -bundled with OpenSSL, such that for any cryptographic algorithm required by -OpenSSL - if there is an ENGINE that implements it and can be initialised, -it should be used. The following code illustrates how this can work; - - /* Load all bundled ENGINEs into memory and make them visible */ - ENGINE_load_builtin_engines(); - /* Register all of them for every algorithm they collectively implement */ - ENGINE_register_all_complete(); - -That's all that's required. Eg. the next time OpenSSL tries to set up an -RSA key, any bundled ENGINEs that implement RSA_METHOD will be passed to -ENGINE_init() and if any of those succeed, that ENGINE will be set as the -default for RSA use from then on. - -=head2 Advanced configuration support - -There is a mechanism supported by the ENGINE framework that allows each -ENGINE implementation to define an arbitrary set of configuration -"commands" and expose them to OpenSSL and any applications based on -OpenSSL. This mechanism is entirely based on the use of name-value pairs -and assumes ASCII input (no unicode or UTF for now!), so it is ideal if -applications want to provide a transparent way for users to provide -arbitrary configuration "directives" directly to such ENGINEs. It is also -possible for the application to dynamically interrogate the loaded ENGINE -implementations for the names, descriptions, and input flags of their -available "control commands", providing a more flexible configuration -scheme. However, if the user is expected to know which ENGINE device he/she -is using (in the case of specialised hardware, this goes without saying) -then applications may not need to concern themselves with discovering the -supported control commands and simply prefer to pass settings into ENGINEs -exactly as they are provided by the user. - -Before illustrating how control commands work, it is worth mentioning what -they are typically used for. Broadly speaking there are two uses for -control commands; the first is to provide the necessary details to the -implementation (which may know nothing at all specific to the host system) -so that it can be initialised for use. This could include the path to any -driver or config files it needs to load, required network addresses, -smart-card identifiers, passwords to initialise protected devices, -logging information, etc etc. This class of commands typically needs to be -passed to an ENGINE B<before> attempting to initialise it, ie. before -calling ENGINE_init(). The other class of commands consist of settings or -operations that tweak certain behaviour or cause certain operations to take -place, and these commands may work either before or after ENGINE_init(), or -in some cases both. ENGINE implementations should provide indications of -this in the descriptions attached to builtin control commands and/or in -external product documentation. - -I<Issuing control commands to an ENGINE> - -Let's illustrate by example; a function for which the caller supplies the -name of the ENGINE it wishes to use, a table of string-pairs for use before -initialisation, and another table for use after initialisation. Note that -the string-pairs used for control commands consist of a command "name" -followed by the command "parameter" - the parameter could be NULL in some -cases but the name can not. This function should initialise the ENGINE -(issuing the "pre" commands beforehand and the "post" commands afterwards) -and set it as the default for everything except RAND and then return a -boolean success or failure. - - int generic_load_engine_fn(const char *engine_id, - const char **pre_cmds, int pre_num, - const char **post_cmds, int post_num) - { - ENGINE *e = ENGINE_by_id(engine_id); - if(!e) return 0; - while(pre_num--) { - if(!ENGINE_ctrl_cmd_string(e, pre_cmds[0], pre_cmds[1], 0)) { - fprintf(stderr, "Failed command (%s - %s:%s)\n", engine_id, - pre_cmds[0], pre_cmds[1] ? pre_cmds[1] : "(NULL)"); - ENGINE_free(e); - return 0; - } - pre_cmds += 2; - } - if(!ENGINE_init(e)) { - fprintf(stderr, "Failed initialisation\n"); - ENGINE_free(e); - return 0; - } - /* ENGINE_init() returned a functional reference, so free the structural - * reference from ENGINE_by_id(). */ - ENGINE_free(e); - while(post_num--) { - if(!ENGINE_ctrl_cmd_string(e, post_cmds[0], post_cmds[1], 0)) { - fprintf(stderr, "Failed command (%s - %s:%s)\n", engine_id, - post_cmds[0], post_cmds[1] ? post_cmds[1] : "(NULL)"); - ENGINE_finish(e); - return 0; - } - post_cmds += 2; - } - ENGINE_set_default(e, ENGINE_METHOD_ALL & ~ENGINE_METHOD_RAND); - /* Success */ - return 1; - } - -Note that ENGINE_ctrl_cmd_string() accepts a boolean argument that can -relax the semantics of the function - if set non-zero it will only return -failure if the ENGINE supported the given command name but failed while -executing it, if the ENGINE doesn't support the command name it will simply -return success without doing anything. In this case we assume the user is -only supplying commands specific to the given ENGINE so we set this to -FALSE. - -I<Discovering supported control commands> - -It is possible to discover at run-time the names, numerical-ids, descriptions -and input parameters of the control commands supported by an ENGINE using a -structural reference. Note that some control commands are defined by OpenSSL -itself and it will intercept and handle these control commands on behalf of the -ENGINE, ie. the ENGINE's ctrl() handler is not used for the control command. -openssl/engine.h defines an index, ENGINE_CMD_BASE, that all control commands -implemented by ENGINEs should be numbered from. Any command value lower than -this symbol is considered a "generic" command is handled directly by the -OpenSSL core routines. - -It is using these "core" control commands that one can discover the the control -commands implemented by a given ENGINE, specifically the commands; - - #define ENGINE_HAS_CTRL_FUNCTION 10 - #define ENGINE_CTRL_GET_FIRST_CMD_TYPE 11 - #define ENGINE_CTRL_GET_NEXT_CMD_TYPE 12 - #define ENGINE_CTRL_GET_CMD_FROM_NAME 13 - #define ENGINE_CTRL_GET_NAME_LEN_FROM_CMD 14 - #define ENGINE_CTRL_GET_NAME_FROM_CMD 15 - #define ENGINE_CTRL_GET_DESC_LEN_FROM_CMD 16 - #define ENGINE_CTRL_GET_DESC_FROM_CMD 17 - #define ENGINE_CTRL_GET_CMD_FLAGS 18 - -Whilst these commands are automatically processed by the OpenSSL framework code, -they use various properties exposed by each ENGINE to process these -queries. An ENGINE has 3 properties it exposes that can affect how this behaves; -it can supply a ctrl() handler, it can specify ENGINE_FLAGS_MANUAL_CMD_CTRL in -the ENGINE's flags, and it can expose an array of control command descriptions. -If an ENGINE specifies the ENGINE_FLAGS_MANUAL_CMD_CTRL flag, then it will -simply pass all these "core" control commands directly to the ENGINE's ctrl() -handler (and thus, it must have supplied one), so it is up to the ENGINE to -reply to these "discovery" commands itself. If that flag is not set, then the -OpenSSL framework code will work with the following rules; - - if no ctrl() handler supplied; - ENGINE_HAS_CTRL_FUNCTION returns FALSE (zero), - all other commands fail. - if a ctrl() handler was supplied but no array of control commands; - ENGINE_HAS_CTRL_FUNCTION returns TRUE, - all other commands fail. - if a ctrl() handler and array of control commands was supplied; - ENGINE_HAS_CTRL_FUNCTION returns TRUE, - all other commands proceed processing ... - -If the ENGINE's array of control commands is empty then all other commands will -fail, otherwise; ENGINE_CTRL_GET_FIRST_CMD_TYPE returns the identifier of -the first command supported by the ENGINE, ENGINE_GET_NEXT_CMD_TYPE takes the -identifier of a command supported by the ENGINE and returns the next command -identifier or fails if there are no more, ENGINE_CMD_FROM_NAME takes a string -name for a command and returns the corresponding identifier or fails if no such -command name exists, and the remaining commands take a command identifier and -return properties of the corresponding commands. All except -ENGINE_CTRL_GET_FLAGS return the string length of a command name or description, -or populate a supplied character buffer with a copy of the command name or -description. ENGINE_CTRL_GET_FLAGS returns a bitwise-OR'd mask of the following -possible values; - - #define ENGINE_CMD_FLAG_NUMERIC (unsigned int)0x0001 - #define ENGINE_CMD_FLAG_STRING (unsigned int)0x0002 - #define ENGINE_CMD_FLAG_NO_INPUT (unsigned int)0x0004 - #define ENGINE_CMD_FLAG_INTERNAL (unsigned int)0x0008 - -If the ENGINE_CMD_FLAG_INTERNAL flag is set, then any other flags are purely -informational to the caller - this flag will prevent the command being usable -for any higher-level ENGINE functions such as ENGINE_ctrl_cmd_string(). -"INTERNAL" commands are not intended to be exposed to text-based configuration -by applications, administrations, users, etc. These can support arbitrary -operations via ENGINE_ctrl(), including passing to and/or from the control -commands data of any arbitrary type. These commands are supported in the -discovery mechanisms simply to allow applications determinie if an ENGINE -supports certain specific commands it might want to use (eg. application "foo" -might query various ENGINEs to see if they implement "FOO_GET_VENDOR_LOGO_GIF" - -and ENGINE could therefore decide whether or not to support this "foo"-specific -extension). - -=head2 Future developments - -The ENGINE API and internal architecture is currently being reviewed. Slated for -possible release in 0.9.8 is support for transparent loading of "dynamic" -ENGINEs (built as self-contained shared-libraries). This would allow ENGINE -implementations to be provided independently of OpenSSL libraries and/or -OpenSSL-based applications, and would also remove any requirement for -applications to explicitly use the "dynamic" ENGINE to bind to shared-library -implementations. - -=head1 SEE ALSO - -L<rsa(3)|rsa(3)>, L<dsa(3)|dsa(3)>, L<dh(3)|dh(3)>, L<rand(3)|rand(3)> - -=cut |