man > provider-signature(7)

PROVIDER-SIGNATURE(7SSL)                       OpenSSL                      PROVIDER-SIGNATURE(7SSL)

NAME
       provider-signature - The signature library <-> provider functions

SYNOPSIS
        #include <openssl/core_dispatch.h>
        #include <openssl/core_names.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.
         */

        /* Context management */
        void *OSSL_FUNC_signature_newctx(void *provctx, const char *propq);
        void OSSL_FUNC_signature_freectx(void *ctx);
        void *OSSL_FUNC_signature_dupctx(void *ctx);

        /* Signing */
        int OSSL_FUNC_signature_sign_init(void *ctx, void *provkey,
                                          const OSSL_PARAM params[]);
        int OSSL_FUNC_signature_sign(void *ctx, unsigned char *sig, size_t *siglen,
                                     size_t sigsize, const unsigned char *tbs, size_t tbslen);

        /* Verifying */
        int OSSL_FUNC_signature_verify_init(void *ctx, void *provkey,
                                            const OSSL_PARAM params[]);
        int OSSL_FUNC_signature_verify(void *ctx, const unsigned char *sig, size_t siglen,
                                       const unsigned char *tbs, size_t tbslen);

        /* Verify Recover */
        int OSSL_FUNC_signature_verify_recover_init(void *ctx, void *provkey,
                                                    const OSSL_PARAM params[]);
        int OSSL_FUNC_signature_verify_recover(void *ctx, unsigned char *rout,
                                               size_t *routlen, size_t routsize,
                                               const unsigned char *sig, size_t siglen);

        /* Digest Sign */
        int OSSL_FUNC_signature_digest_sign_init(void *ctx, const char *mdname,
                                                 void *provkey,
                                                 const OSSL_PARAM params[]);
        int OSSL_FUNC_signature_digest_sign_update(void *ctx, const unsigned char *data,
                                            size_t datalen);
        int OSSL_FUNC_signature_digest_sign_final(void *ctx, unsigned char *sig,
                                                  size_t *siglen, size_t sigsize);
        int OSSL_FUNC_signature_digest_sign(void *ctx,
                                     unsigned char *sigret, size_t *siglen,
                                     size_t sigsize, const unsigned char *tbs,
                                     size_t tbslen);

        /* Digest Verify */
        int OSSL_FUNC_signature_digest_verify_init(void *ctx, const char *mdname,
                                                   void *provkey,
                                                   const OSSL_PARAM params[]);
        int OSSL_FUNC_signature_digest_verify_update(void *ctx,
                                                     const unsigned char *data,
                                                     size_t datalen);
        int OSSL_FUNC_signature_digest_verify_final(void *ctx, const unsigned char *sig,
                                             size_t siglen);
        int OSSL_FUNC_signature_digest_verify(void *ctx, const unsigned char *sig,
                                       size_t siglen, const unsigned char *tbs,
                                       size_t tbslen);

        /* Signature parameters */
        int OSSL_FUNC_signature_get_ctx_params(void *ctx, OSSL_PARAM params[]);
        const OSSL_PARAM *OSSL_FUNC_signature_gettable_ctx_params(void *ctx,
                                                                  void *provctx);
        int OSSL_FUNC_signature_set_ctx_params(void *ctx, const OSSL_PARAM params[]);
        const OSSL_PARAM *OSSL_FUNC_signature_settable_ctx_params(void *ctx,
                                                                  void *provctx);
        /* MD parameters */
        int OSSL_FUNC_signature_get_ctx_md_params(void *ctx, OSSL_PARAM params[]);
        const OSSL_PARAM * OSSL_FUNC_signature_gettable_ctx_md_params(void *ctx);
        int OSSL_FUNC_signature_set_ctx_md_params(void *ctx, const OSSL_PARAM params[]);
        const OSSL_PARAM * OSSL_FUNC_signature_settable_ctx_md_params(void *ctx);

DESCRIPTION
       This documentation is primarily aimed at provider authors. See provider(7) for further
       information.

       The signature (OSSL_OP_SIGNATURE) operation enables providers to implement signature
       algorithms and make them available to applications via the API functions EVP_PKEY_sign(3),
       EVP_PKEY_verify(3), and EVP_PKEY_verify_recover(3) (as well as other related functions).

       All "functions" mentioned here are passed as function pointers between libcrypto and the
       provider in OSSL_DISPATCH(3) arrays via OSSL_ALGORITHM(3) arrays that are returned by the
       provider's provider_query_operation() function (see "Provider Functions" in
       provider-base(7)).

       All these "functions" have a corresponding function type definition named
       OSSL_FUNC_{name}_fn, and a helper function to retrieve the function pointer from an
       OSSL_DISPATCH(3) element named OSSL_FUNC_{name}.  For example, the "function"
       OSSL_FUNC_signature_newctx() has these:

        typedef void *(OSSL_FUNC_signature_newctx_fn)(void *provctx, const char *propq);
        static ossl_inline OSSL_FUNC_signature_newctx_fn
            OSSL_FUNC_signature_newctx(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:

        OSSL_FUNC_signature_newctx                 OSSL_FUNC_SIGNATURE_NEWCTX
        OSSL_FUNC_signature_freectx                OSSL_FUNC_SIGNATURE_FREECTX
        OSSL_FUNC_signature_dupctx                 OSSL_FUNC_SIGNATURE_DUPCTX

        OSSL_FUNC_signature_sign_init              OSSL_FUNC_SIGNATURE_SIGN_INIT
        OSSL_FUNC_signature_sign                   OSSL_FUNC_SIGNATURE_SIGN

        OSSL_FUNC_signature_verify_init            OSSL_FUNC_SIGNATURE_VERIFY_INIT
        OSSL_FUNC_signature_verify                 OSSL_FUNC_SIGNATURE_VERIFY

        OSSL_FUNC_signature_verify_recover_init    OSSL_FUNC_SIGNATURE_VERIFY_RECOVER_INIT
        OSSL_FUNC_signature_verify_recover         OSSL_FUNC_SIGNATURE_VERIFY_RECOVER

        OSSL_FUNC_signature_digest_sign_init       OSSL_FUNC_SIGNATURE_DIGEST_SIGN_INIT
        OSSL_FUNC_signature_digest_sign_update     OSSL_FUNC_SIGNATURE_DIGEST_SIGN_UPDATE
        OSSL_FUNC_signature_digest_sign_final      OSSL_FUNC_SIGNATURE_DIGEST_SIGN_FINAL
        OSSL_FUNC_signature_digest_sign            OSSL_FUNC_SIGNATURE_DIGEST_SIGN

        OSSL_FUNC_signature_digest_verify_init     OSSL_FUNC_SIGNATURE_DIGEST_VERIFY_INIT
        OSSL_FUNC_signature_digest_verify_update   OSSL_FUNC_SIGNATURE_DIGEST_VERIFY_UPDATE
        OSSL_FUNC_signature_digest_verify_final    OSSL_FUNC_SIGNATURE_DIGEST_VERIFY_FINAL
        OSSL_FUNC_signature_digest_verify          OSSL_FUNC_SIGNATURE_DIGEST_VERIFY

        OSSL_FUNC_signature_get_ctx_params         OSSL_FUNC_SIGNATURE_GET_CTX_PARAMS
        OSSL_FUNC_signature_gettable_ctx_params    OSSL_FUNC_SIGNATURE_GETTABLE_CTX_PARAMS
        OSSL_FUNC_signature_set_ctx_params         OSSL_FUNC_SIGNATURE_SET_CTX_PARAMS
        OSSL_FUNC_signature_settable_ctx_params    OSSL_FUNC_SIGNATURE_SETTABLE_CTX_PARAMS

        OSSL_FUNC_signature_get_ctx_md_params      OSSL_FUNC_SIGNATURE_GET_CTX_MD_PARAMS
        OSSL_FUNC_signature_gettable_ctx_md_params OSSL_FUNC_SIGNATURE_GETTABLE_CTX_MD_PARAMS
        OSSL_FUNC_signature_set_ctx_md_params      OSSL_FUNC_SIGNATURE_SET_CTX_MD_PARAMS
        OSSL_FUNC_signature_settable_ctx_md_params OSSL_FUNC_SIGNATURE_SETTABLE_CTX_MD_PARAMS

       A signature algorithm implementation may not implement all of these functions.  In order to
       be a consistent set of functions we must have at least a set of context functions
       (OSSL_FUNC_signature_newctx and OSSL_FUNC_signature_freectx) as well as a set of "signature"
       functions, i.e. at least one of:

       OSSL_FUNC_signature_sign_init and OSSL_FUNC_signature_sign
       OSSL_FUNC_signature_verify_init and OSSL_FUNC_signature_verify
       OSSL_FUNC_signature_verify_recover_init and OSSL_FUNC_signature_verify_recover
       OSSL_FUNC_signature_digest_sign_init, OSSL_FUNC_signature_digest_sign_update and
       OSSL_FUNC_signature_digest_sign_final
       OSSL_FUNC_signature_digest_verify_init, OSSL_FUNC_signature_digest_verify_update and
       OSSL_FUNC_signature_digest_verify_final
       OSSL_FUNC_signature_digest_sign_init and OSSL_FUNC_signature_digest_sign
       OSSL_FUNC_signature_digest_verify_init and OSSL_FUNC_signature_digest_verify

       OSSL_FUNC_signature_set_ctx_params  and OSSL_FUNC_signature_settable_ctx_params are optional,
       but if one of them is present then the other one must also be present. The  same  applies  to
       OSSL_FUNC_signature_get_ctx_params  and  OSSL_FUNC_signature_gettable_ctx_params,  as well as
       the "md_params" functions. The OSSL_FUNC_signature_dupctx function is optional.

       A signature algorithm must also implement some mechanism for generating, loading or importing
       keys via the key management (OSSL_OP_KEYMGMT) operation.  See provider-keymgmt(7) for further
       details.

   Context Management Functions
       OSSL_FUNC_signature_newctx() should create and return a pointer to a provider side  structure
       for holding context information during a signature operation.  A pointer to this context will
       be  passed  back  in a number of the other signature operation function calls.  The parameter
       provctx is the provider context generated during provider initialisation  (see  provider(7)).
       The  propq parameter is a property query string that may be (optionally) used by the provider
       during any "fetches" that it may perform (if it performs any).

       OSSL_FUNC_signature_freectx() is passed a pointer to the provider side signature  context  in
       the ctx parameter.  This function should free any resources associated with that context.

       OSSL_FUNC_signature_dupctx()  should duplicate the provider side signature context in the ctx
       parameter and return the duplicate copy.

   Signing Functions
       OSSL_FUNC_signature_sign_init() initialises a context  for  signing  given  a  provider  side
       signature context in the ctx parameter, and a pointer to a provider key object in the provkey
       parameter.   The  params,  if  not  NULL, should be set on the context in a manner similar to
       using OSSL_FUNC_signature_set_ctx_params().  The  key  object  should  have  been  previously
       generated,  loaded  or  imported into the provider using the key management (OSSL_OP_KEYMGMT)
       operation (see provider-keymgmt(7)>.

       OSSL_FUNC_signature_sign() performs the actual  signing  itself.   A  previously  initialised
       signature context is passed in the ctx parameter.  The data to be signed is pointed to be the
       tbs  parameter  which  is  tbslen  bytes  long.   Unless sig is NULL, the signature should be
       written to the location pointed to by the sig parameter and  it  should  not  exceed  sigsize
       bytes  in  length.  The length of the signature should be written to *siglen.  If sig is NULL
       then the maximum length of the signature should be written to *siglen.

   Verify Functions
       OSSL_FUNC_signature_verify_init() initialises a context for verifying  a  signature  given  a
       provider  side signature context in the ctx parameter, and a pointer to a provider key object
       in the provkey parameter.  The params, if not NULL, should be set on the context in a  manner
       similar  to  using  OSSL_FUNC_signature_set_ctx_params().   The  key  object should have been
       previously generated,  loaded  or  imported  into  the  provider  using  the  key  management
       (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>.

       OSSL_FUNC_signature_verify()   performs   the   actual  verification  itself.   A  previously
       initialised signature context is passed in the ctx parameter.  The data  that  the  signature
       covers  is  pointed  to  be  the  tbs parameter which is tbslen bytes long.  The signature is
       pointed to by the sig parameter which is siglen bytes long.

   Verify Recover Functions
       OSSL_FUNC_signature_verify_recover_init() initialises a context  for  recovering  the  signed
       data  given  a  provider  side  signature  context  in  the ctx parameter, and a pointer to a
       provider key object in the provkey parameter.  The params, if not NULL, should be set on  the
       context  in  a  manner similar to using OSSL_FUNC_signature_set_ctx_params().  The key object
       should have been previously generated, loaded or imported into the  provider  using  the  key
       management (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>.

       OSSL_FUNC_signature_verify_recover() performs the actual verify recover itself.  A previously
       initialised signature context is passed in the ctx parameter.  The signature is pointed to by
       the sig parameter which is siglen bytes long.  Unless rout is NULL, the recovered data should
       be  written  to  the  location  pointed  to by rout which should not exceed routsize bytes in
       length.  The length of the recovered data should be written to *routlen.   If  rout  is  NULL
       then the maximum size of the output buffer is written to the routlen parameter.

   Digest Sign Functions
       OSSL_FUNC_signature_digeset_sign_init()  initialises  a  context for signing given a provider
       side signature context in the ctx parameter, and a pointer to a provider key  object  in  the
       provkey parameter.  The params, if not NULL, should be set on the context in a manner similar
       to  using  OSSL_FUNC_signature_set_ctx_params()  and OSSL_FUNC_signature_set_ctx_md_params().
       The key object should have been previously generated, loaded or imported  into  the  provider
       using  the key management (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>.  The name of
       the digest to be used will be in the mdname parameter.

       OSSL_FUNC_signature_digest_sign_update() provides data to be signed  in  the  data  parameter
       which  should  be  of length datalen. A previously initialised signature context is passed in
       the ctx parameter. This function may be called multiple times to cumulatively add data to  be
       signed.

       OSSL_FUNC_signature_digest_sign_final()  finalises  a  signature operation previously started
       through OSSL_FUNC_signature_digest_sign_init()  and  OSSL_FUNC_signature_digest_sign_update()
       calls.      Once     finalised     no     more     data     will     be     added     through
       OSSL_FUNC_signature_digest_sign_update().  A  previously  initialised  signature  context  is
       passed  in  the  ctx  parameter.  Unless  sig is NULL, the signature should be written to the
       location pointed to by the sig parameter and it should not exceed sigsize  bytes  in  length.
       The  length  of  the  signature should be written to *siglen. If sig is NULL then the maximum
       length of the signature should be written to *siglen.

       OSSL_FUNC_signature_digest_sign() implements a "one shot" digest  sign  operation  previously
       started  through  OSSL_FUNC_signature_digeset_sign_init(). A previously initialised signature
       context is passed in the ctx parameter. The data to be signed  is  in  tbs  which  should  be
       tbslen  bytes  long.  Unless  sig  is  NULL,  the signature should be written to the location
       pointed to by the sig parameter and it should not exceed sigsize bytes in length. The  length
       of  the signature should be written to *siglen. If sig is NULL then the maximum length of the
       signature should be written to *siglen.

   Digest Verify Functions
       OSSL_FUNC_signature_digeset_verify_init()  initialises  a  context  for  verifying  given   a
       provider  side  verification  context  in  the ctx parameter, and a pointer to a provider key
       object in the provkey parameter.  The params, if not NULL, should be set on the context in  a
       manner          similar          to          OSSL_FUNC_signature_set_ctx_params()         and
       OSSL_FUNC_signature_set_ctx_md_params().   The  key  object  should  have   been   previously
       generated,  loaded  or  imported into the provider using the key management (OSSL_OP_KEYMGMT)
       operation (see provider-keymgmt(7)>.  The name of the digest to be used will be in the mdname
       parameter.

       OSSL_FUNC_signature_digest_verify_update() provides data to be verified in the data parameter
       which should be of length datalen. A previously initialised verification context is passed in
       the ctx parameter. This function may be called multiple times to cumulatively add data to  be
       verified.

       OSSL_FUNC_signature_digest_verify_final()   finalises  a  verification  operation  previously
       started            through            OSSL_FUNC_signature_digest_verify_init()            and
       OSSL_FUNC_signature_digest_verify_update()  calls.  Once finalised no more data will be added
       through OSSL_FUNC_signature_digest_verify_update().  A  previously  initialised  verification
       context  is  passed  in  the  ctx  parameter. The signature to be verified is in sig which is
       siglen bytes long.

       OSSL_FUNC_signature_digest_verify()  implements  a  "one  shot"   digest   verify   operation
       previously    started   through   OSSL_FUNC_signature_digeset_verify_init().   A   previously
       initialised verification context is passed in the ctx parameter. The data to be  verified  is
       in  tbs  which  should  be tbslen bytes long. The signature to be verified is in sig which is
       siglen bytes long.

   Signature parameters
       See  OSSL_PARAM(3)  for  further  details  on  the   parameters   structure   used   by   the
       OSSL_FUNC_signature_get_ctx_params() and OSSL_FUNC_signature_set_ctx_params() functions.

       OSSL_FUNC_signature_get_ctx_params()  gets  signature  parameters  associated  with the given
       provider side signature context ctx and stored them  in  params.   Passing  NULL  for  params
       should return true.

       OSSL_FUNC_signature_set_ctx_params()  sets the signature parameters associated with the given
       provider side signature context ctx to params.  Any parameter settings are additional to  any
       that were previously set.  Passing NULL for params should return true.

       Common parameters currently recognised by built-in signature algorithms are as follows.

       "digest" (OSSL_SIGNATURE_PARAM_DIGEST) <UTF8 string>
           Get  or  sets  the  name  of  the  digest  algorithm  used for the input to the signature
           functions. It is required in order to calculate the "algorithm-id".

       "properties" (OSSL_SIGNATURE_PARAM_PROPERTIES) <UTF8 string>
           Sets the name of the property query associated with the "digest" algorithm.  NULL is used
           if this optional value is not set.

       "digest-size" (OSSL_SIGNATURE_PARAM_DIGEST_SIZE) <unsigned integer>
           Gets or sets the output size of the digest algorithm used for the input to the  signature
           functions.  The length of the "digest-size" parameter should not exceed that of a size_t.

       "algorithm-id" (OSSL_SIGNATURE_PARAM_ALGORITHM_ID) <octet string>
           Gets the DER encoded AlgorithmIdentifier that corresponds to the combination of signature
           algorithm and digest algorithm for the signature operation.

       "kat" (OSSL_SIGNATURE_PARAM_KAT) <unsigned integer>
           Sets  a  flag  to  modify the sign operation to return an error if the initial calculated
           signature is invalid.  In the normal mode of operation - new  random  values  are  chosen
           until  the  signature  operation  succeeds.   By  default it retries until a signature is
           calculated.  Setting the value to 0 causes the sign operation  to  retry,  otherwise  the
           sign  operation  is  only tried once and returns whether or not it was successful.  Known
           answer tests can be performed if the random  generator  is  overridden  to  supply  known
           values that either pass or fail.

       OSSL_FUNC_signature_gettable_ctx_params() and OSSL_FUNC_signature_settable_ctx_params() get a
       constant  OSSL_PARAM(3)  array  that  describes  the  gettable  and settable parameters, i.e.
       parameters   that    can    be    used    with    OSSL_FUNC_signature_get_ctx_params()    and
       OSSL_FUNC_signature_set_ctx_params() respectively.

   MD parameters
       See   OSSL_PARAM(3)   for   further   details   on  the  parameters  structure  used  by  the
       OSSL_FUNC_signature_get_md_ctx_params()      and      OSSL_FUNC_signature_set_md_ctx_params()
       functions.

       OSSL_FUNC_signature_get_md_ctx_params()  gets  digest  parameters  associated  with the given
       provider side digest signature context ctx and stores  them  in  params.   Passing  NULL  for
       params should return true.

       OSSL_FUNC_signature_set_ms_ctx_params()  sets the digest parameters associated with the given
       provider side digest signature context ctx to params.  Any parameter settings are  additional
       to any that were previously set.  Passing NULL for params should return true.

       Parameters  currently  recognised  by built-in signature algorithms are the same as those for
       built-in digest  algorithms.  See  "Digest  Parameters"  in  provider-digest(7)  for  further
       information.

       OSSL_FUNC_signature_gettable_md_ctx_params() and OSSL_FUNC_signature_settable_md_ctx_params()
       get  a  constant  OSSL_PARAM(3)  array  that  describes  the  gettable  and  settable  digest
       parameters, i.e. parameters that can be used with OSSL_FUNC_signature_get_md_ctx_params() and
       OSSL_FUNC_signature_set_md_ctx_params() respectively.

RETURN VALUES
       OSSL_FUNC_signature_newctx() and OSSL_FUNC_signature_dupctx() should return the newly created
       provider side signature context, or NULL on failure.

       OSSL_FUNC_signature_gettable_ctx_params(),         OSSL_FUNC_signature_settable_ctx_params(),
       OSSL_FUNC_signature_gettable_md_ctx_params()                                              and
       OSSL_FUNC_signature_settable_md_ctx_params(), return the gettable or settable parameters in a
       constant OSSL_PARAM(3) array.

       All other functions should return 1 for success or 0 on error.

SEE ALSO
       provider(7)

HISTORY
       The provider SIGNATURE interface was introduced in OpenSSL 3.0.

COPYRIGHT
       Copyright 2019-2023 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>.

3.0.13                                       2026-07-29                     PROVIDER-SIGNATURE(7SSL)
provider-signature(7)
NAME SYNOPSIS DESCRIPTION
Context Management Functions Signing Functions Verify Functions Verify Recover Functions Digest Sign Functions Digest Verify Functions Signature parameters MD parameters
RETURN VALUES SEE ALSO HISTORY COPYRIGHT

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