PROVIDER-BASE(7SSL) OpenSSL PROVIDER-BASE(7SSL)
NAME
provider-base - The basic OpenSSL library <-> provider functions
SYNOPSIS
#include <openssl/core_dispatch.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_CORE_HANDLE *handle);
int core_get_params(const OSSL_CORE_HANDLE *handle, OSSL_PARAM params[]);
typedef void (*OSSL_thread_stop_handler_fn)(void *arg);
int core_thread_start(const OSSL_CORE_HANDLE *handle,
OSSL_thread_stop_handler_fn handfn,
void *arg);
OPENSSL_CORE_CTX *core_get_libctx(const OSSL_CORE_HANDLE *handle);
void core_new_error(const OSSL_CORE_HANDLE *handle);
void core_set_error_debug(const OSSL_CORE_HANDLE *handle,
const char *file, int line, const char *func);
void core_vset_error(const OSSL_CORE_HANDLE *handle,
uint32_t reason, const char *fmt, va_list args);
int core_obj_add_sigid(const OSSL_CORE_HANDLE *prov, const char *sign_name,
const char *digest_name, const char *pkey_name);
int core_obj_create(const OSSL_CORE_HANDLE *handle, const char *oid,
const char *sn, const char *ln);
/*
* 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_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 *buflen);
OSSL_CORE_BIO *BIO_new_file(const char *filename, const char *mode);
OSSL_CORE_BIO *BIO_new_membuf(const void *buf, int len);
int BIO_read_ex(OSSL_CORE_BIO *bio, void *data, size_t data_len,
size_t *bytes_read);
int BIO_write_ex(OSSL_CORE_BIO *bio, const void *data, size_t data_len,
size_t *written);
int BIO_up_ref(OSSL_CORE_BIO *bio);
int BIO_free(OSSL_CORE_BIO *bio);
int BIO_vprintf(OSSL_CORE_BIO *bio, const char *format, va_list args);
int BIO_vsnprintf(char *buf, size_t n, const char *fmt, va_list args);
void OSSL_SELF_TEST_set_callback(OSSL_LIB_CTX *libctx, OSSL_CALLBACK *cb,
void *cbarg);
size_t get_entropy(const OSSL_CORE_HANDLE *handle,
unsigned char **pout, int entropy,
size_t min_len, size_t max_len);
size_t get_user_entropy(const OSSL_CORE_HANDLE *handle,
unsigned char **pout, int entropy,
size_t min_len, size_t max_len);
void cleanup_entropy(const OSSL_CORE_HANDLE *handle,
unsigned char *buf, size_t len);
void cleanup_user_entropy(const OSSL_CORE_HANDLE *handle,
unsigned char *buf, size_t len);
size_t get_nonce(const OSSL_CORE_HANDLE *handle,
unsigned char **pout, size_t min_len, size_t max_len,
const void *salt, size_t salt_len);
size_t get_user_nonce(const OSSL_CORE_HANDLE *handle,
unsigned char **pout, size_t min_len, size_t max_len,
const void *salt, size_t salt_len);
void cleanup_nonce(const OSSL_CORE_HANDLE *handle,
unsigned char *buf, size_t len);
void cleanup_user_nonce(const OSSL_CORE_HANDLE *handle,
unsigned char *buf, size_t len);
/* Functions for querying the providers in the application library context */
int provider_register_child_cb(const OSSL_CORE_HANDLE *handle,
int (*create_cb)(const OSSL_CORE_HANDLE *provider,
void *cbdata),
int (*remove_cb)(const OSSL_CORE_HANDLE *provider,
void *cbdata),
int (*global_props_cb)(const char *props, void *cbdata),
void *cbdata);
void provider_deregister_child_cb(const OSSL_CORE_HANDLE *handle);
const char *provider_name(const OSSL_CORE_HANDLE *prov);
void *provider_get0_provider_ctx(const OSSL_CORE_HANDLE *prov);
const OSSL_DISPATCH *provider_get0_dispatch(const OSSL_CORE_HANDLE *prov);
int provider_up_ref(const OSSL_CORE_HANDLE *prov, int activate);
int provider_free(const OSSL_CORE_HANDLE *prov, int deactivate);
/* 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);
void provider_unquery_operation(void *provctx, int operation_id,
const OSSL_ALGORITHM *algs);
const OSSL_ITEM *provider_get_reason_strings(void *provctx);
int provider_get_capabilities(void *provctx, const char *capability,
OSSL_CALLBACK *cb, void *arg);
int provider_self_test(void *provctx);
DESCRIPTION
All "functions" mentioned here are passed as function pointers between
libcrypto and the provider in OSSL_DISPATCH(3) arrays, in the call of
the provider initialization function. See "Provider" in provider(7) for
a description of the initialization function. They are known as
"upcalls".
All these "functions" have a corresponding function type definition
named OSSL_FUNC_{name}_fn, and a helper function to retrieve the
function pointer from a OSSL_DISPATCH(3) element named OSSL_FUNC_{name}.
For example, the "function" core_gettable_params() has these:
typedef OSSL_PARAM *
(OSSL_FUNC_core_gettable_params_fn)(const OSSL_CORE_HANDLE *handle);
static ossl_inline OSSL_NAME_core_gettable_params_fn
OSSL_FUNC_core_gettable_params(const OSSL_DISPATCH *opf);
OSSL_DISPATCH(3) arrays are indexed by numbers that are provided as
macros in openssl-core_dispatch.h(7), as follows:
For in (the OSSL_DISPATCH(3) array passed from 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_libctx OSSL_FUNC_CORE_GET_LIBCTX
core_new_error OSSL_FUNC_CORE_NEW_ERROR
core_set_error_debug OSSL_FUNC_CORE_SET_ERROR_DEBUG
core_vset_error OSSL_FUNC_CORE_VSET_ERROR
core_set_error_mark OSSL_FUNC_CORE_SET_ERROR_MARK
core_clear_last_error_mark OSSL_FUNC_CORE_CLEAR_LAST_ERROR_MARK
core_pop_error_to_mark OSSL_FUNC_CORE_POP_ERROR_TO_MARK
core_count_to_mark OSSL_FUNC_CORE_COUNT_TO_MARK
core_obj_add_sigid OSSL_FUNC_CORE_OBJ_ADD_SIGID
core_obj_create OSSL_FUNC_CORE_OBJ_CREATE
CRYPTO_malloc OSSL_FUNC_CRYPTO_MALLOC
CRYPTO_zalloc OSSL_FUNC_CRYPTO_ZALLOC
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_write_ex OSSL_FUNC_BIO_WRITE_EX
BIO_up_ref OSSL_FUNC_BIO_UP_REF
BIO_free OSSL_FUNC_BIO_FREE
BIO_vprintf OSSL_FUNC_BIO_VPRINTF
BIO_vsnprintf OSSL_FUNC_BIO_VSNPRINTF
BIO_puts OSSL_FUNC_BIO_PUTS
BIO_gets OSSL_FUNC_BIO_GETS
BIO_ctrl OSSL_FUNC_BIO_CTRL
OPENSSL_cleanse OSSL_FUNC_OPENSSL_CLEANSE
OSSL_SELF_TEST_set_callback OSSL_FUNC_SELF_TEST_CB
ossl_rand_get_entropy OSSL_FUNC_GET_ENTROPY
ossl_rand_get_user_entropy OSSL_FUNC_GET_USER_ENTROPY
ossl_rand_cleanup_entropy OSSL_FUNC_CLEANUP_ENTROPY
ossl_rand_cleanup_user_entropy OSSL_FUNC_CLEANUP_USER_ENTROPY
ossl_rand_get_nonce OSSL_FUNC_GET_NONCE
ossl_rand_get_user_nonce OSSL_FUNC_GET_USER_NONCE
ossl_rand_cleanup_nonce OSSL_FUNC_CLEANUP_NONCE
ossl_rand_cleanup_user_nonce OSSL_FUNC_CLEANUP_USER_NONCE
provider_register_child_cb OSSL_FUNC_PROVIDER_REGISTER_CHILD_CB
provider_deregister_child_cb OSSL_FUNC_PROVIDER_DEREGISTER_CHILD_CB
provider_name OSSL_FUNC_PROVIDER_NAME
provider_get0_provider_ctx OSSL_FUNC_PROVIDER_GET0_PROVIDER_CTX
provider_get0_dispatch OSSL_FUNC_PROVIDER_GET0_DISPATCH
provider_up_ref OSSL_FUNC_PROVIDER_UP_REF
provider_free OSSL_FUNC_PROVIDER_FREE
For *out (the OSSL_DISPATCH(3) array passed from the provider to
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_unquery_operation OSSL_FUNC_PROVIDER_UNQUERY_OPERATION
provider_get_reason_strings OSSL_FUNC_PROVIDER_GET_REASON_STRINGS
provider_get_capabilities OSSL_FUNC_PROVIDER_GET_CAPABILITIES
provider_self_test OSSL_FUNC_PROVIDER_SELF_TEST
Core functions
core_gettable_params() returns a constant array of descriptor
OSSL_PARAM(3), for parameters that core_get_params() can handle.
core_get_params() retrieves parameters from the core for the given
handle. See "Core parameters" below for a description of currently
known parameters.
The core_thread_start() function informs the core that the provider has
stated an interest in the current thread. The core will inform the
provider when the thread eventually stops. It must be passed the handle
for this provider, as well as a callback handfn which will be called
when the thread stops. The callback will subsequently be called, with
the supplied argument arg, from the thread that is stopping and gets
passed the provider context as an argument. This may be useful to
perform thread specific clean up such as freeing thread local variables.
core_get_libctx() retrieves the core context in which the library object
for the current provider is stored, accessible through the handle. This
function is useful only for built-in providers such as the default
provider. Never cast this to OSSL_LIB_CTX in a provider that is not
built-in as the OSSL_LIB_CTX of the library loading the provider might
be a completely different structure than the OSSL_LIB_CTX of the library
the provider is linked to. Use OSSL_LIB_CTX_new_child(3) instead to
obtain a proper library context that is linked to the application
library context.
core_new_error(), core_set_error_debug() and core_vset_error() are
building blocks for reporting an error back to the core, with reference
to the handle.
core_new_error()
allocates a new thread specific error record.
This corresponds to the OpenSSL function ERR_new(3).
core_set_error_debug()
sets debugging information in the current thread specific error
record. The debugging information includes the name of the file
file, the line line and the function name func where the error
occurred.
This corresponds to the OpenSSL function ERR_set_debug(3).
core_vset_error()
sets the reason for the error, along with any addition data. The
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 fmt and a set of arguments args, which are treated in
the same manner as with BIO_vsnprintf(). file and line may also be
passed to indicate exactly where the error occurred or was reported.
This corresponds to the OpenSSL function ERR_vset_error(3).
core_set_error_mark()
sets a mark on the current topmost error record if there is one.
This corresponds to the OpenSSL function ERR_set_mark(3).
core_clear_last_error_mark()
removes the last mark added if there is one.
This corresponds to the OpenSSL function ERR_clear_last_mark(3).
core_pop_error_to_mark()
pops the top of the error stack until a mark is found. The mark is
then removed. If there is no mark, the whole stack is removed.
This corresponds to the OpenSSL function ERR_pop_to_mark(3).
core_count_to_mark()
returns the number of entries on the error stack above the most
recently marked entry, not including that entry. If there is no mark
in the error stack, the number of entries in the error stack is
returned.
This corresponds to the OpenSSL function ERR_count_to_mark(3).
The core_obj_create() function registers a new OID and associated short
name sn and long name ln for the given handle. It is similar to the
OpenSSL function OBJ_create(3) except that it returns 1 on success or 0
on failure. It will treat as success the case where the OID already
exists (even if the short name sn or long name ln provided as arguments
differ from those associated with the existing OID, in which case the
new names are not associated).
The core_obj_add_sigid() function registers a new composite signature
algorithm (sign_name) consisting of an underlying signature algorithm
(pkey_name) and digest algorithm (digest_name) for the given handle. It
assumes that the OIDs for the composite signature algorithm as well as
for the underlying signature and digest algorithms are either already
known to OpenSSL or have been registered via a call to
core_obj_create(). It corresponds to the OpenSSL function
OBJ_add_sigid(3), except that the objects are identified by name rather
than a numeric NID. Any name (OID, short name or long name) can be used
to identify the object. It will treat as success the case where the
composite signature algorithm already exists (even if registered against
a different underlying signature or digest algorithm). For digest_name,
NULL or an empty string is permissible for signature algorithms that do
not need a digest to operate correctly. The function returns 1 on
success or 0 on failure.
CRYPTO_malloc(), CRYPTO_zalloc(), 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_write_ex(), BIO_up_ref(),
BIO_free(), BIO_vprintf(), BIO_vsnprintf(), BIO_gets(), BIO_puts(),
BIO_ctrl(), OPENSSL_cleanse() and OPENSSL_hexstr2buf() correspond
exactly to the public functions with the same name. As a matter of
fact, the pointers in the OSSL_DISPATCH(3) array are typically direct
pointers to those public functions. Note that the BIO functions take an
OSSL_CORE_BIO type rather than the standard BIO type. This is to ensure
that a provider does not mix BIOs from the core with BIOs used on the
provider side (the two are not compatible).
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.
get_entropy() retrieves seeding material from the operating system. The
seeding material will have at least entropy bytes of randomness and the
output will have at least min_len and at most max_len bytes. The buffer
address is stored in *pout and the buffer length is returned to the
caller. On error, zero is returned.
get_user_entropy() is the same as get_entropy() except that it will
attempt to gather seed material via the seed source specified by a call
to RAND_set_seed_source_type(3) or via "Random Configuration" in
config(5).
cleanup_entropy() is used to clean up and free the buffer returned by
get_entropy(). The entropy pointer returned by get_entropy() is passed
in buf and its length in len.
cleanup_user_entropy() is used to clean up and free the buffer returned
by get_user_entropy(). The entropy pointer returned by
get_user_entropy() is passed in buf and its length in len.
get_nonce() retrieves a nonce using the passed salt parameter of length
salt_len and operating system specific information. The salt should
contain uniquely identifying information and this is included, in an
unspecified manner, as part of the output. The output is stored in a
buffer which contains at least min_len and at most max_len bytes. The
buffer address is stored in *pout and the buffer length returned to the
caller. On error, zero is returned.
get_user_nonce() is the same as get_nonce() except that it will attempt
to gather seed material via the seed source specified by a call to
RAND_set_seed_source_type(3) or via "Random Configuration" in config(5).
cleanup_nonce() is used to clean up and free the buffer returned by
get_nonce(). The nonce pointer returned by get_nonce() is passed in buf
and its length in len.
cleanup_user_nonce() is used to clean up and free the buffer returned by
get_user_nonce(). The nonce pointer returned by get_user_nonce() is
passed in buf and its length in len.
provider_register_child_cb() registers callbacks for being informed
about the loading and unloading of providers in the application's
library context. handle is this provider's handle and cbdata is this
provider's data that will be passed back to the callbacks. It returns 1
on success or 0 otherwise. These callbacks may be called while holding
locks in libcrypto. In order to avoid deadlocks the callback
implementation must not be long running and must not call other OpenSSL
API functions or upcalls.
create_cb is a callback that will be called when a new provider is
loaded into the application's library context. It is also called for any
providers that are already loaded at the point that this callback is
registered. The callback is passed the handle being used for the new
provider being loadded and this provider's data in cbdata. It should
return 1 on success or 0 on failure.
remove_cb is a callback that will be called when a new provider is
unloaded from the application's library context. It is passed the handle
being used for the provider being unloaded and this provider's data in
cbdata. It should return 1 on success or 0 on failure.
global_props_cb is a callback that will be called when the global
properties from the parent library context are changed. It should return
1 on success or 0 on failure.
provider_deregister_child_cb() unregisters callbacks previously
registered via provider_register_child_cb(). If
provider_register_child_cb() has been called then
provider_deregister_child_cb() should be called at or before the point
that this provider's teardown function is called.
provider_name() returns a string giving the name of the provider
identified by handle.
provider_get0_provider_ctx() returns the provider context that is
associated with the provider identified by prov.
provider_get0_dispatch() gets the dispatch table registered by the
provider identified by prov when it initialised.
provider_up_ref() increments the reference count on the provider prov.
If activate is nonzero then the provider is also loaded if it is not
already loaded. It returns 1 on success or 0 on failure.
provider_free() decrements the reference count on the provider prov. If
deactivate is nonzero then the provider is also unloaded if it is not
already loaded. It returns 1 on success or 0 on failure.
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 provctx.
provider_gettable_params() should return a constant array of descriptor
OSSL_PARAM(3), for parameters that provider_get_params() can handle.
provider_get_params() should process the OSSL_PARAM(3) array params,
setting the values of the parameters it understands.
provider_query_operation() should return a constant OSSL_ALGORITHM(3)
that corresponds to the given operation_id. It should indicate if the
core may store a reference to this array by setting *no_store to 0 (core
may store a reference) or 1 (core may not store a reference).
provider_unquery_operation() informs the provider that the result of a
provider_query_operation() is no longer directly required and that the
function pointers have been copied. The operation_id should match that
passed to provider_query_operation() and algs should be its return
value.
provider_get_reason_strings() should return a constant OSSL_ITEM(3)
array that provides reason strings for reason codes the provider may use
when reporting errors using core_put_error().
The provider_get_capabilities() function should call the callback cb
passing it a set of OSSL_PARAM(3)s and the caller supplied argument arg.
The OSSL_PARAM(3)s should provide details about the capability with the
name given in the capability argument relevant for the provider context
provctx. If a provider supports multiple capabilities with the given
name then it may call the callback multiple times (one for each
capability). Capabilities can be useful for describing the services that
a provider can offer. For further details see the "CAPABILITIES" section
below. It should return 1 on success or 0 on error.
The provider_self_test() function should perform known answer tests on a
subset of the algorithms that it uses, and may also verify the integrity
of the provider module. It should return 1 on success or 0 on error. It
will return 1 if this function is not used.
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().
Provider parameters
provider_get_params() can return the following provider parameters to
the core:
"name" (OSSL_PROV_PARAM_NAME) <UTF8 ptr>
This points to a string that should give a unique name for the
provider.
"version" (OSSL_PROV_PARAM_VERSION) <UTF8 ptr>
This points to a string that is a version number associated with
this provider. OpenSSL in-built providers use OPENSSL_VERSION_STR,
but this may be different for any third party provider. This string
is for informational purposes only.
"buildinfo" (OSSL_PROV_PARAM_BUILDINFO) <UTF8 ptr>
This points to a string that is a build information associated with
this provider. OpenSSL in-built providers use
OPENSSL_FULL_VERSION_STR, but this may be different for any third
party provider.
"status" (OSSL_PROV_PARAM_STATUS) <unsigned integer>
This returns 0 if the provider has entered an error state, otherwise
it returns 1.
provider_gettable_params() should return the above parameters.
Core parameters
core_get_params() can retrieve the following core parameters for each
provider:
"openssl-version" (OSSL_PROV_PARAM_CORE_VERSION) <UTF8 string ptr>
This points to the OpenSSL libraries' full version string, i.e. the
string expanded from the macro OPENSSL_VERSION_STR.
"provider-name" (OSSL_PROV_PARAM_CORE_PROV_NAME) <UTF8 string ptr>
This points to the OpenSSL libraries' idea of what the calling
provider is named.
"module-filename" (OSSL_PROV_PARAM_CORE_MODULE_FILENAME) <UTF8 string
ptr>
This points to a string containing the full filename of the
providers module file.
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:
config_diagnostics = 1
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:
"activate"
pointing at the string "1"
"data1"
pointing at the string "2"
"data2"
pointing at the string "str"
"more.data3"
pointing at the string "foo,bar"
For more information on handling parameters, see OSSL_PARAM(3) as
OSSL_PARAM_int(3).
CAPABILITIES
Capabilities describe some of the services that a provider can offer.
Applications can query the capabilities to discover those services.
"TLS-GROUP" Capability
The "TLS-GROUP" capability can be queried by libssl to discover the list
of TLS groups that a provider can support. Each group supported can be
used for key exchange (KEX) or key encapsulation method (KEM) during a
TLS handshake. TLS clients can advertise the list of TLS groups they
support in the supported_groups extension, and TLS servers can select a
group from the offered list that they also support. In this way a
provider can add to the list of groups that libssl already supports with
additional ones.
Each TLS group that a provider supports should be described via the
callback passed in through the provider_get_capabilities function. Each
group should have the following details supplied (all are mandatory,
except OSSL_CAPABILITY_TLS_GROUP_IS_KEM):
"tls-group-name" (OSSL_CAPABILITY_TLS_GROUP_NAME) <UTF8 string>
The name of the group as given in the IANA TLS Supported Groups
registry
<https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-8>.
"tls-group-name-internal" (OSSL_CAPABILITY_TLS_GROUP_NAME_INTERNAL)
<UTF8 string>
The name of the group as known by the provider. This could be the
same as the "tls-group-name", but does not have to be.
"tls-group-id" (OSSL_CAPABILITY_TLS_GROUP_ID) <unsigned integer>
The TLS group id value as given in the IANA TLS Supported Groups
registry.
It is possible to register the same group id from within different
providers. Users should note that if no property query is specified,
or more than one implementation matches the property query then it
is unspecified which implementation for a particular group id will
be used.
"tls-group-alg" (OSSL_CAPABILITY_TLS_GROUP_ALG) <UTF8 string>
The name of a Key Management algorithm that the provider offers and
that should be used with this group. Keys created should be able to
support key exchange or key encapsulation method (KEM), as implied
by the optional OSSL_CAPABILITY_TLS_GROUP_IS_KEM flag. The
algorithm must support key and parameter generation as well as the
key/parameter generation parameter, OSSL_PKEY_PARAM_GROUP_NAME. The
group name given via "tls-group-name-internal" above will be passed
via OSSL_PKEY_PARAM_GROUP_NAME when libssl wishes to generate
keys/parameters.
"tls-group-sec-bits" (OSSL_CAPABILITY_TLS_GROUP_SECURITY_BITS) <unsigned
integer>
The number of bits of security offered by keys in this group. The
number of bits should be comparable with the ones given in table 2
and 3 of the NIST SP800-57 document.
"tls-group-is-kem" (OSSL_CAPABILITY_TLS_GROUP_IS_KEM) <unsigned integer>
Boolean flag to describe if the group should be used in key exchange
(KEX) mode (0, default) or in key encapsulation method (KEM) mode
(1).
This parameter is optional: if not specified, KEX mode is assumed as
the default mode for the group.
In KEX mode, in a typical Diffie-Hellman fashion, both sides execute
keygen then derive against the peer public key. To operate in KEX
mode, the group implementation must support the provider functions
as described in provider-keyexch(7).
In KEM mode, the client executes keygen and sends its public key,
the server executes encapsulate using the client's public key and
sends back the resulting ciphertext, finally the client executes
decapsulate to retrieve the same shared secret generated by the
server's encapsulate. To operate in KEM mode, the group
implementation must support the provider functions as described in
provider-kem(7).
Both in KEX and KEM mode, the resulting shared secret is then used
according to the protocol specification.
"tls-min-tls" (OSSL_CAPABILITY_TLS_GROUP_MIN_TLS) <integer>
"tls-max-tls" (OSSL_CAPABILITY_TLS_GROUP_MAX_TLS) <integer>
"tls-min-dtls" (OSSL_CAPABILITY_TLS_GROUP_MIN_DTLS) <integer>
"tls-max-dtls" (OSSL_CAPABILITY_TLS_GROUP_MAX_DTLS) <integer>
These parameters can be used to describe the minimum and maximum TLS
and DTLS versions supported by the group. The values equate to the
on-the-wire encoding of the various TLS versions. For example
TLSv1.3 is 0x0304 (772 decimal), and TLSv1.2 is 0x0303 (771
decimal). A 0 indicates that there is no defined minimum or maximum.
A -1 indicates that the group should not be used in that protocol.
"TLS-SIGALG" Capability
The "TLS-SIGALG" capability can be queried by libssl to discover the
list of TLS signature algorithms that a provider can support. Each
signature supported can be used for client- or server-authentication in
addition to the built-in signature algorithms. TLS1.3 clients can
advertise the list of TLS signature algorithms they support in the
signature_algorithms extension, and TLS servers can select an algorithm
from the offered list that they also support. In this way a provider can
add to the list of signature algorithms that libssl already supports
with additional ones.
Each TLS signature algorithm that a provider supports should be
described via the callback passed in through the
provider_get_capabilities function. Each algorithm can have the
following details supplied:
"iana-name" (OSSL_CAPABILITY_TLS_SIGALG_IANA_NAME) <UTF8 string>
The name of the signature algorithm as given in the IANA TLS
Signature Scheme registry as "Description":
<https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-signaturescheme>.
This value must be supplied.
"iana-code-point" (OSSL_CAPABILITY_TLS_SIGALG_CODE_POINT) <unsigned
integer>
The TLS algorithm ID value as given in the IANA TLS SignatureScheme
registry. This value must be supplied.
It is possible to register the same code point from within different
providers. Users should note that if no property query is specified,
or more than one implementation matches the property query then it
is unspecified which implementation for a particular code point will
be used.
"sigalg-name" (OSSL_CAPABILITY_TLS_SIGALG_NAME) <UTF8 string>
A name for the full (possibly composite hash-and-signature)
signature algorithm. The provider may, but is not obligated to,
provide a signature implementation with this name; if it doesn't,
this is assumed to be a composite of a pure signature algorithm and
a hash algorithm, which must be given with the parameters "sig-name"
and "hash-name". This value must be supplied.
"sigalg-oid" (OSSL_CAPABILITY_TLS_SIGALG_OID) <UTF8 string>
The OID of the "sigalg-name" algorithm in canonical numeric text
form. If this parameter is given, OBJ_create() will be used to
create an OBJ and a NID for this OID, using the "sigalg-name"
parameter for its (short) name. Otherwise, it's assumed to already
exist in the object database, possibly done by the provider with the
core_obj_create() upcall. This value is optional.
"sig-name" (OSSL_CAPABILITY_TLS_SIGALG_SIG_NAME) <UTF8 string>
The name of the pure signature algorithm that is part of a composite
"sigalg-name". If "sigalg-name" is implemented by the provider, this
parameter is redundant and must not be given. This value is
optional.
"sig-oid" (OSSL_CAPABILITY_TLS_SIGALG_SIG_OID) <UTF8 string>
The OID of the "sig-name" algorithm in canonical numeric text form.
If this parameter is given, OBJ_create() will be used to create an
OBJ and a NID for this OID, using the "sig-name" parameter for its
(short) name. Otherwise, it is assumed to already exist in the
object database. This can be done by the provider using the
core_obj_create() upcall. This value is optional.
"hash-name" (OSSL_CAPABILITY_TLS_SIGALG_HASH_NAME) <UTF8 string>
The name of the hash algorithm that is part of a composite "sigalg-
name". If "sigalg-name" is implemented by the provider, this
parameter is redundant and must not be given. This value is
optional.
"hash-oid" (OSSL_CAPABILITY_TLS_SIGALG_HASH_OID) <UTF8 string>
The OID of the "hash-name" algorithm in canonical numeric text form.
If this parameter is given, OBJ_create() will be used to create an
OBJ and a NID for this OID, using the "hash-name" parameter for its
(short) name. Otherwise, it's assumed to already exist in the
object database, possibly done by the provider with the
core_obj_create() upcall. This value is optional.
"key-type" (OSSL_CAPABILITY_TLS_SIGALG_KEYTYPE) <UTF8 string>
The key type of the public key of applicable certificates. If this
parameter isn't present, it's assumed to be the same as "sig-name"
if that's present, otherwise "sigalg-name". This value is optional.
"key-type-oid" (OSSL_CAPABILITY_TLS_SIGALG_KEYTYPE_OID) <UTF8 string>
The OID of the "key-type" in canonical numeric text form. If this
parameter is given, OBJ_create() will be used to create an OBJ and a
NID for this OID, using the "key-type" parameter for its (short)
name. Otherwise, it's assumed to already exist in the object
database, possibly done by the provider with the core_obj_create()
upcall. This value is optional.
"sec-bits" (OSSL_CAPABILITY_TLS_SIGALG_SECURITY_BITS) <unsigned integer>
The number of bits of security offered by keys of this algorithm.
The number of bits should be comparable with the ones given in table
2 and 3 of the NIST SP800-57 document. This number is used to
determine the security strength of the algorithm if no digest
algorithm has been registered that otherwise defines the security
strength. If the signature algorithm implements its own digest
internally, this value needs to be set to properly reflect the
overall security strength. This value must be supplied.
"tls-min-tls" (OSSL_CAPABILITY_TLS_SIGALG_MIN_TLS) <integer>
"tls-max-tls" (OSSL_CAPABILITY_TLS_SIGALG_MAX_TLS) <integer>
"tls-min-dtls" (OSSL_CAPABILITY_TLS_SIGALG_MIN_DTLS) <integer>
"tls-max-dtls" (OSSL_CAPABILITY_TLS_SIGALG_MAX_DTLS) <integer>
These parameters can be used to describe the minimum and maximum TLS
and DTLS versions supported by the signature algorithm. The values
equate to the on-the-wire encoding of the various TLS versions. For
example TLSv1.3 is 0x0304 (772 decimal), and TLSv1.2 is 0x0303 (771
decimal). A 0 indicates that there is no defined minimum or maximum.
A -1 in either the min or max field indicates that the signature
algorithm should not be used in that protocol. Presently, provider
signature algorithms are used only with TLS 1.3, if that's enclosed
in the specified range.
NOTES
The core_obj_create() and core_obj_add_sigid() functions were not thread
safe in OpenSSL 3.0.
EXAMPLES
This is an example of a simple provider made available as a dynamically
loadable module. It implements the fictitious algorithm "FOO" for the
fictitious operation "BAR".
#include <malloc.h>
#include <openssl/core.h>
#include <openssl/core_dispatch.h>
/* Errors used in this provider */
#define E_MALLOC 1
static const OSSL_ITEM reasons[] = {
{ E_MALLOC, "memory allocation failure" }.
OSSL_DISPATCH_END
};
/*
* To ensure we get the function signature right, forward declare
* them using function types provided by openssl/core_dispatch.h
*/
OSSL_FUNC_bar_newctx_fn foo_newctx;
OSSL_FUNC_bar_freectx_fn foo_freectx;
OSSL_FUNC_bar_init_fn foo_init;
OSSL_FUNC_bar_update_fn foo_update;
OSSL_FUNC_bar_final_fn foo_final;
OSSL_FUNC_provider_query_operation_fn p_query;
OSSL_FUNC_provider_get_reason_strings_fn p_reasons;
OSSL_FUNC_provider_teardown_fn p_teardown;
OSSL_provider_init_fn OSSL_provider_init;
OSSL_FUNC_core_put_error *c_put_error = NULL;
/* Provider context */
struct prov_ctx_st {
OSSL_CORE_HANDLE *handle;
}
/* 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->handle, 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 },
OSSL_DISPATCH_END
};
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 },
OSSL_DISPATCH_END
};
int OSSL_provider_init(const OSSL_CORE_HANDLE *handle,
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_FUNC_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(handle, E_MALLOC, __FILE__, __LINE__);
return 0;
}
pctx->handle = handle;
return 1;
}
This relies on a few things existing in openssl/core_dispatch.h:
#define OSSL_OP_BAR 4711
#define OSSL_FUNC_BAR_NEWCTX 1
typedef void *(OSSL_FUNC_bar_newctx_fn)(void *provctx);
static ossl_inline OSSL_FUNC_bar_newctx(const OSSL_DISPATCH *opf)
{ return (OSSL_FUNC_bar_newctx_fn *)opf->function; }
#define OSSL_FUNC_BAR_FREECTX 2
typedef void (OSSL_FUNC_bar_freectx_fn)(void *ctx);
static ossl_inline OSSL_FUNC_bar_freectx(const OSSL_DISPATCH *opf)
{ return (OSSL_FUNC_bar_freectx_fn *)opf->function; }
#define OSSL_FUNC_BAR_INIT 3
typedef void *(OSSL_FUNC_bar_init_fn)(void *ctx);
static ossl_inline OSSL_FUNC_bar_init(const OSSL_DISPATCH *opf)
{ return (OSSL_FUNC_bar_init_fn *)opf->function; }
#define OSSL_FUNC_BAR_UPDATE 4
typedef void *(OSSL_FUNC_bar_update_fn)(void *ctx,
unsigned char *in, size_t inl);
static ossl_inline OSSL_FUNC_bar_update(const OSSL_DISPATCH *opf)
{ return (OSSL_FUNC_bar_update_fn *)opf->function; }
#define OSSL_FUNC_BAR_FINAL 5
typedef void *(OSSL_FUNC_bar_final_fn)(void *ctx);
static ossl_inline OSSL_FUNC_bar_final(const OSSL_DISPATCH *opf)
{ return (OSSL_FUNC_bar_final_fn *)opf->function; }
SEE ALSO
provider(7)
HISTORY
The concept of providers and everything surrounding them was introduced
in OpenSSL 3.0.
Definitions for OSSL_CAPABILITY_TLS_SIGALG_MIN_DTLS and
OSSL_CAPABILITY_TLS_SIGALG_MAX_DTLS were added in OpenSSL 3.5.
COPYRIGHT
Copyright 2019-2025 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
<https://www.openssl.org/source/license.html>.
3.5.4 2025-09-30 PROVIDER-BASE(7SSL)
Generated by dwww version 1.16 on Fri Dec 12 12:54:39 CET 2025.