openssl/doc/man7/provider-base.pod

=pod

=head1 NAME

provider-base
- The basic OpenSSL library E<lt>-E<gt> provider functions

=head1 SYNOPSIS

 #include <openssl/core_numbers.h>

 /*
  * None of these are actual functions, but are displayed like this for
  * the function signatures for functions that are offered as function
  * pointers in OSSL_DISPATCH arrays.
  */

 /* Functions offered by libcrypto to the providers */
 const OSSL_ITEM *core_gettable_params(const OSSL_PROVIDER *prov);
 int core_get_params(const OSSL_PROVIDER *prov, OSSL_PARAM params[]);
 int core_thread_start(const OSSL_PROVIDER *prov,
                       OSSL_thread_stop_handler_fn handfn);
 OPENSSL_CTX *core_get_library_context(const OSSL_PROVIDER *prov);
 void core_new_error(const OSSL_PROVIDER *prov);
 void core_set_error_debug(const OSSL_PROVIDER *prov,
                           const char *file, int line, const char *func);
 void core_vset_error(const OSSL_PROVIDER *prov,
                      uint32_t reason, const char *fmt, va_list args);

 /*
  * Some OpenSSL functionality is directly offered to providers via
  * dispatch
  */
 void *CRYPTO_malloc(size_t num, const char *file, int line);
 void *CRYPTO_zalloc(size_t num, const char *file, int line);
 void *CRYPTO_memdup(const void *str, size_t siz,
                     const char *file, int line);
 char *CRYPTO_strdup(const char *str, const char *file, int line);
 char *CRYPTO_strndup(const char *str, size_t s,
                      const char *file, int line);
 void CRYPTO_free(void *ptr, const char *file, int line);
 void CRYPTO_clear_free(void *ptr, size_t num,
                        const char *file, int line);
 void *CRYPTO_realloc(void *addr, size_t num,
                      const char *file, int line);
 void *CRYPTO_clear_realloc(void *addr, size_t old_num, size_t num,
                            const char *file, int line);
 void *CRYPTO_secure_malloc(size_t num, const char *file, int line);
 void *CRYPTO_secure_zalloc(size_t num, const char *file, int line);
 void CRYPTO_secure_free(void *ptr, const char *file, int line);
 void CRYPTO_secure_clear_free(void *ptr, size_t num,
                               const char *file, int line);
 int CRYPTO_secure_allocated(const void *ptr);
 void OPENSSL_cleanse(void *ptr, size_t len);
 unsigned char *OPENSSL_hexstr2buf(const char *str, long *len);

 /* Functions offered by the provider to libcrypto */
 void provider_teardown(void *provctx);
 const OSSL_ITEM *provider_gettable_params(void *provctx);
 int provider_get_params(void *provctx, OSSL_PARAM params[]);
 const OSSL_ALGORITHM *provider_query_operation(void *provctx,
                                                int operation_id,
                                                const int *no_store);
 const OSSL_ITEM *provider_get_reason_strings(void *provctx);

=head1 DESCRIPTION

All "functions" mentioned here are passed as function pointers between
F<libcrypto> and the provider in B<OSSL_DISPATCH> arrays, in the call
of the provider initialization function.  See L<provider(7)/Provider>
for a description of the initialization function.

All these "functions" have a corresponding function type definition
named B<OSSL_{name}_fn>, and a helper function to retrieve the
function pointer from a B<OSSL_DISPATCH> element named
B<OSSL_get_{name}>.
For example, the "function" core_gettable_params() has these:

 typedef OSSL_ITEM *
     (OSSL_core_gettable_params_fn)(const OSSL_PROVIDER *prov);
 static ossl_inline OSSL_NAME_core_gettable_params_fn
     OSSL_get_core_gettable_params(const OSSL_DISPATCH *opf);

B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as
macros in L<openssl-core_numbers.h(7)>, as follows:

For I<in> (the B<OSSL_DISPATCH> array passed from F<libcrypto> to the
provider):

 core_gettable_params           OSSL_FUNC_CORE_GETTABLE_PARAMS
 core_get_params                OSSL_FUNC_CORE_GET_PARAMS
 core_thread_start              OSSL_FUNC_CORE_THREAD_START
 core_get_library_context       OSSL_FUNC_CORE_GET_LIBRARY_CONTEXT
 core_new_error                 OSSL_FUNC_CORE_NEW_ERROR
 core_set_error_debug           OSSL_FUNC_CORE_SET_ERROR_DEBUG
 core_set_error                 OSSL_FUNC_CORE_SET_ERROR
 CRYPTO_malloc                  OSSL_FUNC_CRYPTO_MALLOC
 CRYPTO_zalloc                  OSSL_FUNC_CRYPTO_ZALLOC
 CRYPTO_memdup                  OSSL_FUNC_CRYPTO_MEMDUP
 CRYPTO_strdup                  OSSL_FUNC_CRYPTO_STRDUP
 CRYPTO_strndup                 OSSL_FUNC_CRYPTO_STRNDUP
 CRYPTO_free                    OSSL_FUNC_CRYPTO_FREE
 CRYPTO_clear_free              OSSL_FUNC_CRYPTO_CLEAR_FREE
 CRYPTO_realloc                 OSSL_FUNC_CRYPTO_REALLOC
 CRYPTO_clear_realloc           OSSL_FUNC_CRYPTO_CLEAR_REALLOC
 CRYPTO_secure_malloc           OSSL_FUNC_CRYPTO_SECURE_MALLOC
 CRYPTO_secure_zalloc           OSSL_FUNC_CRYPTO_SECURE_ZALLOC
 CRYPTO_secure_free             OSSL_FUNC_CRYPTO_SECURE_FREE
 CRYPTO_secure_clear_free       OSSL_FUNC_CRYPTO_SECURE_CLEAR_FREE
 CRYPTO_secure_allocated        OSSL_FUNC_CRYPTO_SECURE_ALLOCATED
 BIO_new_file                   OSSL_FUNC_BIO_NEW_FILE
 BIO_new_mem_buf                OSSL_FUNC_BIO_NEW_MEMBUF
 BIO_read_ex                    OSSL_FUNC_BIO_READ_EX
 BIO_free                       OSSL_FUNC_BIO_FREE
 BIO_vprintf                    OSSL_FUNC_BIO_VPRINTF
 OPENSSL_cleanse                OSSL_FUNC_OPENSSL_CLEANSE
 OPENSSL_hexstr2buf             OSSL_FUNC_OPENSSL_HEXSTR2BUF
 OSSL_SELF_TEST_set_callback    OSSL_FUNC_SELF_TEST_CB

For I<*out> (the B<OSSL_DISPATCH> array passed from the provider to
F<libcrypto>):

 provider_teardown              OSSL_FUNC_PROVIDER_TEARDOWN
 provider_gettable_params       OSSL_FUNC_PROVIDER_GETTABLE_PARAMS
 provider_get_params            OSSL_FUNC_PROVIDER_GET_PARAMS
 provider_query_operation       OSSL_FUNC_PROVIDER_QUERY_OPERATION
 provider_get_reason_strings    OSSL_FUNC_PROVIDER_GET_REASON_STRINGS

=head2 Core functions

core_gettable_params() returns a constant array of descriptor
B<OSSL_PARAM>, for parameters that core_get_params() can handle.

core_get_params() retrieves I<prov> parameters from the core.
See L</Core parameters> below for a description of currently known
parameters.

=for comment core_thread_start() TBA

core_get_library_context() retrieves the library context in which the
B<OSSL_PROVIDER> object I<prov> is stored.
This may sometimes be useful if the provider wishes to store a
reference to its context in the same library context.

core_new_error(), core_set_error_debug() and core_set_error() are
building blocks for reporting an error back to the core, with
reference to the provider object I<prov>.

=over 4

=item core_new_error()

allocates a new thread specific error record.

This corresponds to the OpenSSL function L<ERR_new(3)>.

=item core_set_error_debug()

sets debugging information in the current thread specific error
record.
The debugging information includes the name of the file I<file>, the
line I<line> and the function name I<func> where the error occurred.

This corresponds to the OpenSSL function L<ERR_set_debug(3)>.

=item core_set_error()

sets the I<reason> for the error, along with any addition data.
The I<reason> is a number defined by the provider and used to index
the reason strings table that's returned by
provider_get_reason_strings().
The additional data is given as a format string I<fmt> and a set of
arguments I<args>, which are treated in the same manner as with
BIO_vsnprintf().
I<file> and I<line> may also be passed to indicate exactly where the
error occurred or was reported.

This corresponds to the OpenSSL function L<ERR_vset_error(3)>.

=back

CRYPTO_malloc(), CRYPTO_zalloc(), CRYPTO_memdup(), CRYPTO_strdup(),
CRYPTO_strndup(), CRYPTO_free(), CRYPTO_clear_free(),
CRYPTO_realloc(), CRYPTO_clear_realloc(), CRYPTO_secure_malloc(),
CRYPTO_secure_zalloc(), CRYPTO_secure_free(),
CRYPTO_secure_clear_free(), CRYPTO_secure_allocated(),
BIO_new_file(), BIO_new_mem_buf(), BIO_read_ex(), BIO_free(),
BIO_vprintf(), OPENSSL_cleanse(), and OPENSSL_hexstr2buf()
correspond exactly to the public functions with the same name.
As a matter of fact, the pointers in the B<OSSL_DISPATCH> array are
direct pointers to those public functions.
OSSL_SELF_TEST_set_callback() is used to set an optional callback that can be
passed into a provider. This may be ignored by a provider.

=head2 Provider functions

provider_teardown() is called when a provider is shut down and removed
from the core's provider store.
It must free the passed I<provctx>.

provider_gettable_params() should return a constant array of
descriptor B<OSSL_PARAM>, for parameters that provider_get_params()
can handle.

provider_get_params() should process the B<OSSL_PARAM> array
I<params>, setting the values of the parameters it understands.

provider_query_operation() should return a constant B<OSSL_ALGORITHM>
that corresponds to the given I<operation_id>.
It should indicate if the core may store a reference to this array by
setting I<*no_store> to 0 (core may store a reference) or 1 (core may
not store a reference).

provider_get_reason_strings() should return a constant B<OSSL_ITEM>
array that provides reason strings for reason codes the provider may
use when reporting errors using core_put_error().

None of these functions are mandatory, but a provider is fairly
useless without at least provider_query_operation(), and
provider_gettable_params() is fairly useless if not accompanied by
provider_get_params().

=head2 Core parameters

core_get_params() understands the following known parameters:

=over 4

=item "openssl-version"

This is a B<OSSL_PARAM_UTF8_PTR> type of parameter, pointing at the
OpenSSL libraries' full version string, i.e. the string expanded from
the macro B<OPENSSL_VERSION_STR>.

=item "provider-name"

This is a B<OSSL_PARAM_UTF8_PTR> type of parameter, pointing at the
OpenSSL libraries' idea of what the calling provider is called.

=back

Additionally, provider specific configuration parameters from the
config file are available, in dotted name form.
The dotted name form is a concatenation of section names and final
config command name separated by periods.

For example, let's say we have the following config example:

 openssl_conf = openssl_init

 [openssl_init]
 providers = providers_sect

 [providers_sect]
 foo = foo_sect

 [foo_sect]
 activate = 1
 data1 = 2
 data2 = str
 more = foo_more

 [foo_more]
 data3 = foo,bar

The provider will have these additional parameters available:

=over 4

=item "activate"

pointing at the string "1"

=item "data1"

pointing at the string "2"

=item "data2"

pointing at the string "str"

=item "more.data3"

pointing at the string "foo,bar"

=back

For more information on handling parameters, see L<OSSL_PARAM(3)> as
L<OSSL_PARAM_int(3)>.

=head1 EXAMPLES

This is an example of a simple provider made available as a
dynamically loadable module.
It implements the fictitious algorithm C<FOO> for the fictitious
operation C<BAR>.

 #include <malloc.h>
 #include <openssl/core.h>
 #include <openssl/core_numbers.h>

 /* Errors used in this provider */
 #define E_MALLOC       1

 static const OSSL_ITEM reasons[] = {
     { E_MALLOC, "memory allocation failure" }.
     { 0, NULL } /* Termination */
 };

 /*
  * To ensure we get the function signature right, forward declare
  * them using function types provided by openssl/core_numbers.h
  */
 OSSL_OP_bar_newctx_fn foo_newctx;
 OSSL_OP_bar_freectx_fn foo_freectx;
 OSSL_OP_bar_init_fn foo_init;
 OSSL_OP_bar_update_fn foo_update;
 OSSL_OP_bar_final_fn foo_final;

 OSSL_provider_query_operation_fn p_query;
 OSSL_provider_get_reason_strings_fn p_reasons;
 OSSL_provider_teardown_fn p_teardown;

 OSSL_provider_init_fn OSSL_provider_init;

 OSSL_core_put_error *c_put_error = NULL;

 /* Provider context */
 struct prov_ctx_st {
     OSSL_PROVIDER *prov;
 }

 /* operation context for the algorithm FOO */
 struct foo_ctx_st {
     struct prov_ctx_st *provctx;
     int b;
 };

 static void *foo_newctx(void *provctx)
 {
     struct foo_ctx_st *fooctx = malloc(sizeof(*fooctx));

     if (fooctx != NULL)
         fooctx->provctx = provctx;
     else
         c_put_error(provctx->prov, E_MALLOC, __FILE__, __LINE__);
     return fooctx;
 }

 static void foo_freectx(void *fooctx)
 {
     free(fooctx);
 }

 static int foo_init(void *vfooctx)
 {
     struct foo_ctx_st *fooctx = vfooctx;

     fooctx->b = 0x33;
 }

 static int foo_update(void *vfooctx, unsigned char *in, size_t inl)
 {
     struct foo_ctx_st *fooctx = vfooctx;

     /* did you expect something serious? */
     if (inl == 0)
         return 1;
     for (; inl-- > 0; in++)
         *in ^= fooctx->b;
     return 1;
 }

 static int foo_final(void *vfooctx)
 {
     struct foo_ctx_st *fooctx = vfooctx;

     fooctx->b = 0x66;
 }

 static const OSSL_DISPATCH foo_fns[] = {
     { OSSL_FUNC_BAR_NEWCTX, (void (*)(void))foo_newctx },
     { OSSL_FUNC_BAR_FREECTX, (void (*)(void))foo_freectx },
     { OSSL_FUNC_BAR_INIT, (void (*)(void))foo_init },
     { OSSL_FUNC_BAR_UPDATE, (void (*)(void))foo_update },
     { OSSL_FUNC_BAR_FINAL, (void (*)(void))foo_final },
     { 0, NULL }
 };

 static const OSSL_ALGORITHM bars[] = {
     { "FOO", "provider=chumbawamba", foo_fns },
     { NULL, NULL, NULL }
 };

 static const OSSL_ALGORITHM *p_query(void *provctx, int operation_id,
                                      int *no_store)
 {
     switch (operation_id) {
     case OSSL_OP_BAR:
         return bars;
     }
     return NULL;
 }

 static const OSSL_ITEM *p_reasons(void *provctx)
 {
     return reasons;
 }

 static void p_teardown(void *provctx)
 {
     free(provctx);
 }

 static const OSSL_DISPATCH prov_fns[] = {
     { OSSL_FUNC_PROVIDER_TEARDOWN, (void (*)(void))p_teardown },
     { OSSL_FUNC_PROVIDER_QUERY_OPERATION, (void (*)(void))p_query },
     { OSSL_FUNC_PROVIDER_GET_REASON_STRINGS, (void (*)(void))p_reasons },
     { 0, NULL }
 };

 int OSSL_provider_init(const OSSL_PROVIDER *provider,
                        const OSSL_DISPATCH *in,
                        const OSSL_DISPATCH **out,
                        void **provctx)
 {
     struct prov_ctx_st *pctx = NULL;

     for (; in->function_id != 0; in++)
         switch (in->function_id) {
         case OSSL_FUNC_CORE_PUT_ERROR:
             c_put_error = OSSL_get_core_put_error(in);
             break;
         }

     *out = prov_fns;

     if ((pctx = malloc(sizeof(*pctx))) == NULL) {
         /*
          * ALEA IACTA EST, if the core retrieves the reason table
          * regardless, that string will be displayed, otherwise not.
          */
         c_put_error(provider, E_MALLOC, __FILE__, __LINE__);
         return 0;
     }
     return 1;
 }

This relies on a few things existing in F<openssl/core_numbers.h>:

 #define OSSL_OP_BAR            4711

 #define OSSL_FUNC_BAR_NEWCTX      1
 typedef void *(OSSL_OP_bar_newctx_fn)(void *provctx);
 static ossl_inline OSSL_get_bar_newctx(const OSSL_DISPATCH *opf)
 { return (OSSL_OP_bar_newctx_fn *)opf->function; }

 #define OSSL_FUNC_BAR_FREECTX     2
 typedef void (OSSL_OP_bar_freectx_fn)(void *ctx);
 static ossl_inline OSSL_get_bar_newctx(const OSSL_DISPATCH *opf)
 { return (OSSL_OP_bar_freectx_fn *)opf->function; }

 #define OSSL_FUNC_BAR_INIT        3
 typedef void *(OSSL_OP_bar_init_fn)(void *ctx);
 static ossl_inline OSSL_get_bar_init(const OSSL_DISPATCH *opf)
 { return (OSSL_OP_bar_init_fn *)opf->function; }

 #define OSSL_FUNC_BAR_UPDATE      4
 typedef void *(OSSL_OP_bar_update_fn)(void *ctx,
                                       unsigned char *in, size_t inl);
 static ossl_inline OSSL_get_bar_update(const OSSL_DISPATCH *opf)
 { return (OSSL_OP_bar_update_fn *)opf->function; }

 #define OSSL_FUNC_BAR_FINAL       5
 typedef void *(OSSL_OP_bar_final_fn)(void *ctx);
 static ossl_inline OSSL_get_bar_final(const OSSL_DISPATCH *opf)
 { return (OSSL_OP_bar_final_fn *)opf->function; }

=head1 SEE ALSO

L<provider(7)>

=head1 HISTORY

The concept of providers and everything surrounding them was
introduced in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.

=cut