- NAME
- SYNOPSIS
- DESCRIPTION
  - Methods
  - Functions
- RETURN VALUES
- COPYRIGHT

# NAME

EVP_PKEY_meth_new, EVP_PKEY_meth_free, EVP_PKEY_meth_copy, EVP_PKEY_meth_find, EVP_PKEY_meth_add0, EVP_PKEY_METHOD, EVP_PKEY_meth_set_init, EVP_PKEY_meth_set_copy, EVP_PKEY_meth_set_cleanup, EVP_PKEY_meth_set_paramgen, EVP_PKEY_meth_set_keygen, EVP_PKEY_meth_set_sign, EVP_PKEY_meth_set_verify, EVP_PKEY_meth_set_verify_recover, EVP_PKEY_meth_set_signctx, EVP_PKEY_meth_set_verifyctx, EVP_PKEY_meth_set_encrypt, EVP_PKEY_meth_set_decrypt, EVP_PKEY_meth_set_derive, EVP_PKEY_meth_set_ctrl, EVP_PKEY_meth_set_digestsign, EVP_PKEY_meth_set_digestverify, EVP_PKEY_meth_set_check, EVP_PKEY_meth_set_public_check, EVP_PKEY_meth_set_param_check, EVP_PKEY_meth_set_digest_custom, EVP_PKEY_meth_get_init, EVP_PKEY_meth_get_copy, EVP_PKEY_meth_get_cleanup, EVP_PKEY_meth_get_paramgen, EVP_PKEY_meth_get_keygen, EVP_PKEY_meth_get_sign, EVP_PKEY_meth_get_verify, EVP_PKEY_meth_get_verify_recover, EVP_PKEY_meth_get_signctx, EVP_PKEY_meth_get_verifyctx, EVP_PKEY_meth_get_encrypt, EVP_PKEY_meth_get_decrypt, EVP_PKEY_meth_get_derive, EVP_PKEY_meth_get_ctrl, EVP_PKEY_meth_get_digestsign, EVP_PKEY_meth_get_digestverify, EVP_PKEY_meth_get_check, EVP_PKEY_meth_get_public_check, EVP_PKEY_meth_get_param_check, EVP_PKEY_meth_get_digest_custom, EVP_PKEY_meth_remove - manipulating EVP_PKEY_METHOD structure

# SYNOPSIS

    #include <openssl/evp.h>

    typedef struct evp_pkey_method_st EVP_PKEY_METHOD;

    EVP_PKEY_METHOD *EVP_PKEY_meth_new(int id, int flags);
    void EVP_PKEY_meth_free(EVP_PKEY_METHOD *pmeth);
    void EVP_PKEY_meth_copy(EVP_PKEY_METHOD *dst, const EVP_PKEY_METHOD *src);
    const EVP_PKEY_METHOD *EVP_PKEY_meth_find(int type);
    int EVP_PKEY_meth_add0(const EVP_PKEY_METHOD *pmeth);
    int EVP_PKEY_meth_remove(const EVP_PKEY_METHOD *pmeth);

    void EVP_PKEY_meth_set_init(EVP_PKEY_METHOD *pmeth,
                                int (*init) (EVP_PKEY_CTX *ctx));
    void EVP_PKEY_meth_set_copy(EVP_PKEY_METHOD *pmeth,
                                int (*copy) (EVP_PKEY_CTX *dst,
                                             EVP_PKEY_CTX *src));
    void EVP_PKEY_meth_set_cleanup(EVP_PKEY_METHOD *pmeth,
                                   void (*cleanup) (EVP_PKEY_CTX *ctx));
    void EVP_PKEY_meth_set_paramgen(EVP_PKEY_METHOD *pmeth,
                                    int (*paramgen_init) (EVP_PKEY_CTX *ctx),
                                    int (*paramgen) (EVP_PKEY_CTX *ctx,
                                                     EVP_PKEY *pkey));
    void EVP_PKEY_meth_set_keygen(EVP_PKEY_METHOD *pmeth,
                                  int (*keygen_init) (EVP_PKEY_CTX *ctx),
                                  int (*keygen) (EVP_PKEY_CTX *ctx,
                                                 EVP_PKEY *pkey));
    void EVP_PKEY_meth_set_sign(EVP_PKEY_METHOD *pmeth,
                                int (*sign_init) (EVP_PKEY_CTX *ctx),
                                int (*sign) (EVP_PKEY_CTX *ctx,
                                             unsigned char *sig, size_t *siglen,
                                             const unsigned char *tbs,
                                             size_t tbslen));
    void EVP_PKEY_meth_set_verify(EVP_PKEY_METHOD *pmeth,
                                  int (*verify_init) (EVP_PKEY_CTX *ctx),
                                  int (*verify) (EVP_PKEY_CTX *ctx,
                                                 const unsigned char *sig,
                                                 size_t siglen,
                                                 const unsigned char *tbs,
                                                 size_t tbslen));
    void EVP_PKEY_meth_set_verify_recover(EVP_PKEY_METHOD *pmeth,
                                          int (*verify_recover_init) (EVP_PKEY_CTX
                                                                      *ctx),
                                          int (*verify_recover) (EVP_PKEY_CTX
                                                                 *ctx,
                                                                 unsigned char
                                                                 *sig,
                                                                 size_t *siglen,
                                                                 const unsigned
                                                                 char *tbs,
                                                                 size_t tbslen));
    void EVP_PKEY_meth_set_signctx(EVP_PKEY_METHOD *pmeth,
                                   int (*signctx_init) (EVP_PKEY_CTX *ctx,
                                                        EVP_MD_CTX *mctx),
                                   int (*signctx) (EVP_PKEY_CTX *ctx,
                                                   unsigned char *sig,
                                                   size_t *siglen,
                                                   EVP_MD_CTX *mctx));
    void EVP_PKEY_meth_set_verifyctx(EVP_PKEY_METHOD *pmeth,
                                     int (*verifyctx_init) (EVP_PKEY_CTX *ctx,
                                                            EVP_MD_CTX *mctx),
                                     int (*verifyctx) (EVP_PKEY_CTX *ctx,
                                                       const unsigned char *sig,
                                                       int siglen,
                                                       EVP_MD_CTX *mctx));
    void EVP_PKEY_meth_set_encrypt(EVP_PKEY_METHOD *pmeth,
                                   int (*encrypt_init) (EVP_PKEY_CTX *ctx),
                                   int (*encryptfn) (EVP_PKEY_CTX *ctx,
                                                     unsigned char *out,
                                                     size_t *outlen,
                                                     const unsigned char *in,
                                                     size_t inlen));
    void EVP_PKEY_meth_set_decrypt(EVP_PKEY_METHOD *pmeth,
                                   int (*decrypt_init) (EVP_PKEY_CTX *ctx),
                                   int (*decrypt) (EVP_PKEY_CTX *ctx,
                                                   unsigned char *out,
                                                   size_t *outlen,
                                                   const unsigned char *in,
                                                   size_t inlen));
    void EVP_PKEY_meth_set_derive(EVP_PKEY_METHOD *pmeth,
                                  int (*derive_init) (EVP_PKEY_CTX *ctx),
                                  int (*derive) (EVP_PKEY_CTX *ctx,
                                                 unsigned char *key,
                                                 size_t *keylen));
    void EVP_PKEY_meth_set_ctrl(EVP_PKEY_METHOD *pmeth,
                                int (*ctrl) (EVP_PKEY_CTX *ctx, int type, int p1,
                                             void *p2),
                                int (*ctrl_str) (EVP_PKEY_CTX *ctx,
                                                 const char *type,
                                                 const char *value));
    void EVP_PKEY_meth_set_digestsign(EVP_PKEY_METHOD *pmeth,
                                      int (*digestsign) (EVP_MD_CTX *ctx,
                                                         unsigned char *sig,
                                                         size_t *siglen,
                                                         const unsigned char *tbs,
                                                         size_t tbslen));
    void EVP_PKEY_meth_set_digestverify(EVP_PKEY_METHOD *pmeth,
                                        int (*digestverify) (EVP_MD_CTX *ctx,
                                                             const unsigned char *sig,
                                                             size_t siglen,
                                                             const unsigned char *tbs,
                                                             size_t tbslen));
    void EVP_PKEY_meth_set_check(EVP_PKEY_METHOD *pmeth,
                                 int (*check) (EVP_PKEY *pkey));
    void EVP_PKEY_meth_set_public_check(EVP_PKEY_METHOD *pmeth,
                                        int (*check) (EVP_PKEY *pkey));
    void EVP_PKEY_meth_set_param_check(EVP_PKEY_METHOD *pmeth,
                                       int (*check) (EVP_PKEY *pkey));
    void EVP_PKEY_meth_set_digest_custom(EVP_PKEY_METHOD *pmeth,
                                        int (*digest_custom) (EVP_PKEY_CTX *ctx,
                                                              EVP_MD_CTX *mctx));

    void EVP_PKEY_meth_get_init(const EVP_PKEY_METHOD *pmeth,
                                int (**pinit) (EVP_PKEY_CTX *ctx));
    void EVP_PKEY_meth_get_copy(const EVP_PKEY_METHOD *pmeth,
                                int (**pcopy) (EVP_PKEY_CTX *dst,
                                               EVP_PKEY_CTX *src));
    void EVP_PKEY_meth_get_cleanup(const EVP_PKEY_METHOD *pmeth,
                                   void (**pcleanup) (EVP_PKEY_CTX *ctx));
    void EVP_PKEY_meth_get_paramgen(const EVP_PKEY_METHOD *pmeth,
                                    int (**pparamgen_init) (EVP_PKEY_CTX *ctx),
                                    int (**pparamgen) (EVP_PKEY_CTX *ctx,
                                                       EVP_PKEY *pkey));
    void EVP_PKEY_meth_get_keygen(const EVP_PKEY_METHOD *pmeth,
                                  int (**pkeygen_init) (EVP_PKEY_CTX *ctx),
                                  int (**pkeygen) (EVP_PKEY_CTX *ctx,
                                                   EVP_PKEY *pkey));
    void EVP_PKEY_meth_get_sign(const EVP_PKEY_METHOD *pmeth,
                                int (**psign_init) (EVP_PKEY_CTX *ctx),
                                int (**psign) (EVP_PKEY_CTX *ctx,
                                               unsigned char *sig, size_t *siglen,
                                               const unsigned char *tbs,
                                               size_t tbslen));
    void EVP_PKEY_meth_get_verify(const EVP_PKEY_METHOD *pmeth,
                                  int (**pverify_init) (EVP_PKEY_CTX *ctx),
                                  int (**pverify) (EVP_PKEY_CTX *ctx,
                                                   const unsigned char *sig,
                                                   size_t siglen,
                                                   const unsigned char *tbs,
                                                   size_t tbslen));
    void EVP_PKEY_meth_get_verify_recover(const EVP_PKEY_METHOD *pmeth,
                                          int (**pverify_recover_init) (EVP_PKEY_CTX
                                                                        *ctx),
                                          int (**pverify_recover) (EVP_PKEY_CTX
                                                                   *ctx,
                                                                   unsigned char
                                                                   *sig,
                                                                   size_t *siglen,
                                                                   const unsigned
                                                                   char *tbs,
                                                                   size_t tbslen));
    void EVP_PKEY_meth_get_signctx(const EVP_PKEY_METHOD *pmeth,
                                   int (**psignctx_init) (EVP_PKEY_CTX *ctx,
                                                          EVP_MD_CTX *mctx),
                                   int (**psignctx) (EVP_PKEY_CTX *ctx,
                                                     unsigned char *sig,
                                                     size_t *siglen,
                                                     EVP_MD_CTX *mctx));
    void EVP_PKEY_meth_get_verifyctx(const EVP_PKEY_METHOD *pmeth,
                                     int (**pverifyctx_init) (EVP_PKEY_CTX *ctx,
                                                              EVP_MD_CTX *mctx),
                                     int (**pverifyctx) (EVP_PKEY_CTX *ctx,
                                                         const unsigned char *sig,
                                                         int siglen,
                                                         EVP_MD_CTX *mctx));
    void EVP_PKEY_meth_get_encrypt(const EVP_PKEY_METHOD *pmeth,
                                   int (**pencrypt_init) (EVP_PKEY_CTX *ctx),
                                   int (**pencryptfn) (EVP_PKEY_CTX *ctx,
                                                       unsigned char *out,
                                                       size_t *outlen,
                                                       const unsigned char *in,
                                                       size_t inlen));
    void EVP_PKEY_meth_get_decrypt(const EVP_PKEY_METHOD *pmeth,
                                   int (**pdecrypt_init) (EVP_PKEY_CTX *ctx),
                                   int (**pdecrypt) (EVP_PKEY_CTX *ctx,
                                                     unsigned char *out,
                                                     size_t *outlen,
                                                     const unsigned char *in,
                                                     size_t inlen));
    void EVP_PKEY_meth_get_derive(const EVP_PKEY_METHOD *pmeth,
                                  int (**pderive_init) (EVP_PKEY_CTX *ctx),
                                  int (**pderive) (EVP_PKEY_CTX *ctx,
                                                   unsigned char *key,
                                                   size_t *keylen));
    void EVP_PKEY_meth_get_ctrl(const EVP_PKEY_METHOD *pmeth,
                                int (**pctrl) (EVP_PKEY_CTX *ctx, int type, int p1,
                                               void *p2),
                                int (**pctrl_str) (EVP_PKEY_CTX *ctx,
                                                   const char *type,
                                                   const char *value));
    void EVP_PKEY_meth_get_digestsign(EVP_PKEY_METHOD *pmeth,
                                      int (**digestsign) (EVP_MD_CTX *ctx,
                                                          unsigned char *sig,
                                                          size_t *siglen,
                                                          const unsigned char *tbs,
                                                          size_t tbslen));
    void EVP_PKEY_meth_get_digestverify(EVP_PKEY_METHOD *pmeth,
                                        int (**digestverify) (EVP_MD_CTX *ctx,
                                                              const unsigned char *sig,
                                                              size_t siglen,
                                                              const unsigned char *tbs,
                                                              size_t tbslen));
    void EVP_PKEY_meth_get_check(const EVP_PKEY_METHOD *pmeth,
                                 int (**pcheck) (EVP_PKEY *pkey));
    void EVP_PKEY_meth_get_public_check(const EVP_PKEY_METHOD *pmeth,
                                        int (**pcheck) (EVP_PKEY *pkey));
    void EVP_PKEY_meth_get_param_check(const EVP_PKEY_METHOD *pmeth,
                                       int (**pcheck) (EVP_PKEY *pkey));
    void EVP_PKEY_meth_get_digest_custom(EVP_PKEY_METHOD *pmeth,
                                        int (**pdigest_custom) (EVP_PKEY_CTX *ctx,
                                                                EVP_MD_CTX *mctx));

# DESCRIPTION

EVP_PKEY_METHOD is a structure which holds a set of methods for a specific public key cryptographic algorithm. Those methods are usually used to perform different jobs, such as generating a key, signing or verifying, encrypting or decrypting, etc.

There are two places where the EVP_PKEY_METHOD objects are stored: one is a built-in static array representing the standard methods for different algorithms, and the other one is a stack of user-defined application-specific methods, which can be manipulated by using EVP_PKEY_meth_add0(3).

The EVP_PKEY_METHOD objects are usually referenced by EVP_PKEY_CTX objects.

## Methods

The methods are the underlying implementations of a particular public key algorithm present by the EVP_PKEY_CTX object.

    int (*init) (EVP_PKEY_CTX *ctx);
    int (*copy) (EVP_PKEY_CTX *dst, EVP_PKEY_CTX *src);
    void (*cleanup) (EVP_PKEY_CTX *ctx);

The init() method is called to initialize algorithm-specific data when a new EVP_PKEY_CTX is created. As opposed to init(), the cleanup() method is called when an EVP_PKEY_CTX is freed. The copy() method is called when an EVP_PKEY_CTX is being duplicated. Refer to EVP_PKEY_CTX_new(3), EVP_PKEY_CTX_new_id(3), EVP_PKEY_CTX_free(3) and EVP_PKEY_CTX_dup(3).

    int (*paramgen_init) (EVP_PKEY_CTX *ctx);
    int (*paramgen) (EVP_PKEY_CTX *ctx, EVP_PKEY *pkey);

The paramgen_init() and paramgen() methods deal with key parameter generation. They are called by EVP_PKEY_paramgen_init(3) and EVP_PKEY_paramgen(3) to handle the parameter generation process.

    int (*keygen_init) (EVP_PKEY_CTX *ctx);
    int (*keygen) (EVP_PKEY_CTX *ctx, EVP_PKEY *pkey);

The keygen_init() and keygen() methods are used to generate the actual key for the specified algorithm. They are called by EVP_PKEY_keygen_init(3) and EVP_PKEY_keygen(3).

    int (*sign_init) (EVP_PKEY_CTX *ctx);
    int (*sign) (EVP_PKEY_CTX *ctx, unsigned char *sig, size_t *siglen,
                 const unsigned char *tbs, size_t tbslen);

The sign_init() and sign() methods are used to generate the signature of a piece of data using a private key. They are called by EVP_PKEY_sign_init(3) and EVP_PKEY_sign(3).

    int (*verify_init) (EVP_PKEY_CTX *ctx);
    int (*verify) (EVP_PKEY_CTX *ctx,
                   const unsigned char *sig, size_t siglen,
                   const unsigned char *tbs, size_t tbslen);

The verify_init() and verify() methods are used to verify whether a signature is valid. They are called by EVP_PKEY_verify_init(3) and EVP_PKEY_verify(3).

    int (*verify_recover_init) (EVP_PKEY_CTX *ctx);
    int (*verify_recover) (EVP_PKEY_CTX *ctx,
                           unsigned char *rout, size_t *routlen,
                           const unsigned char *sig, size_t siglen);

The verify_recover_init() and verify_recover() methods are used to verify a signature and then recover the digest from the signature (for instance, a signature that was generated by RSA signing algorithm). They are called by EVP_PKEY_verify_recover_init(3) and EVP_PKEY_verify_recover(3).

    int (*signctx_init) (EVP_PKEY_CTX *ctx, EVP_MD_CTX *mctx);
    int (*signctx) (EVP_PKEY_CTX *ctx, unsigned char *sig, size_t *siglen,
                    EVP_MD_CTX *mctx);

The signctx_init() and signctx() methods are used to sign a digest present by a EVP_MD_CTX object. They are called by the EVP_DigestSign functions. See EVP_DigestSignInit(3) for details.

    int (*verifyctx_init) (EVP_PKEY_CTX *ctx, EVP_MD_CTX *mctx);
    int (*verifyctx) (EVP_PKEY_CTX *ctx, const unsigned char *sig, int siglen,
                      EVP_MD_CTX *mctx);

The verifyctx_init() and verifyctx() methods are used to verify a signature against the data in a EVP_MD_CTX object. They are called by the various EVP_DigestVerify functions. See EVP_DigestVerifyInit(3) for details.

    int (*encrypt_init) (EVP_PKEY_CTX *ctx);
    int (*encrypt) (EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen,
                    const unsigned char *in, size_t inlen);

The encrypt_init() and encrypt() methods are used to encrypt a piece of data. They are called by EVP_PKEY_encrypt_init(3) and EVP_PKEY_encrypt(3).

    int (*decrypt_init) (EVP_PKEY_CTX *ctx);
    int (*decrypt) (EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen,
                    const unsigned char *in, size_t inlen);

The decrypt_init() and decrypt() methods are used to decrypt a piece of data. They are called by EVP_PKEY_decrypt_init(3) and EVP_PKEY_decrypt(3).

    int (*derive_init) (EVP_PKEY_CTX *ctx);
    int (*derive) (EVP_PKEY_CTX *ctx, unsigned char *key, size_t *keylen);

The derive_init() and derive() methods are used to derive the shared secret from a public key algorithm (for instance, the DH algorithm). They are called by EVP_PKEY_derive_init(3) and EVP_PKEY_derive(3).

    int (*ctrl) (EVP_PKEY_CTX *ctx, int type, int p1, void *p2);
    int (*ctrl_str) (EVP_PKEY_CTX *ctx, const char *type, const char *value);

The ctrl() and ctrl_str() methods are used to adjust algorithm-specific settings. See EVP_PKEY_CTX_ctrl(3) and related functions for details.

    int (*digestsign) (EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen,
                       const unsigned char *tbs, size_t tbslen);
    int (*digestverify) (EVP_MD_CTX *ctx, const unsigned char *sig,
                         size_t siglen, const unsigned char *tbs,
                         size_t tbslen);

The digestsign() and digestverify() methods are used to generate or verify a signature in a one-shot mode. They could be called by EVP_DigestSign(3) and EVP_DigestVerify(3).

    int (*check) (EVP_PKEY *pkey);
    int (*public_check) (EVP_PKEY *pkey);
    int (*param_check) (EVP_PKEY *pkey);

The check(), public_check() and param_check() methods are used to validate a key-pair, the public component and parameters respectively for a given pkey. They could be called by EVP_PKEY_check(3), EVP_PKEY_public_check(3) and EVP_PKEY_param_check(3) respectively.

    int (*digest_custom) (EVP_PKEY_CTX *ctx, EVP_MD_CTX *mctx);

The digest_custom() method is used to generate customized digest content before the real message is passed to functions like EVP_DigestSignUpdate(3) or EVP_DigestVerifyInit(3). This is usually required by some public key signature algorithms like SM2 which requires a hashed prefix to the message to be signed. The digest_custom() function will be called by EVP_DigestSignInit(3) and EVP_DigestVerifyInit(3).

## Functions

EVP_PKEY_meth_new() creates and returns a new EVP_PKEY_METHOD object, and associates the given id and flags. The following flags are supported:

    EVP_PKEY_FLAG_AUTOARGLEN
    EVP_PKEY_FLAG_SIGCTX_CUSTOM

If an EVP_PKEY_METHOD is set with the EVP_PKEY_FLAG_AUTOARGLEN flag, the maximum size of the output buffer will be automatically calculated or checked in corresponding EVP methods by the EVP framework. Thus the implementations of these methods don't need to care about handling the case of returning output buffer size by themselves. For details on the output buffer size, refer to EVP_PKEY_sign(3).

The EVP_PKEY_FLAG_SIGCTX_CUSTOM is used to indicate the signctx() method of an EVP_PKEY_METHOD is always called by the EVP framework while doing a digest signing operation by calling EVP_DigestSignFinal(3).

EVP_PKEY_meth_free() frees an existing EVP_PKEY_METHOD pointed by pmeth.

EVP_PKEY_meth_copy() copies an EVP_PKEY_METHOD object from src to dst.

EVP_PKEY_meth_find() finds an EVP_PKEY_METHOD object with the id. This function first searches through the user-defined method objects and then the built-in objects.

EVP_PKEY_meth_add0() adds pmeth to the user defined stack of methods.

EVP_PKEY_meth_remove() removes an EVP_PKEY_METHOD object added by EVP_PKEY_meth_add0().

The EVP_PKEY_meth_set functions set the corresponding fields of EVP_PKEY_METHOD structure with the arguments passed.

The EVP_PKEY_meth_get functions get the corresponding fields of EVP_PKEY_METHOD structure to the arguments provided.

# RETURN VALUES

EVP_PKEY_meth_new() returns a pointer to a new EVP_PKEY_METHOD object or returns NULL on error.

EVP_PKEY_meth_free() and EVP_PKEY_meth_copy() do not return values.

EVP_PKEY_meth_find() returns a pointer to the found EVP_PKEY_METHOD object or returns NULL if not found.

EVP_PKEY_meth_add0() returns 1 if method is added successfully or 0 if an error occurred.

EVP_PKEY_meth_remove() returns 1 if method is removed successfully or 0 if an error occurred.

All EVP_PKEY_meth_set and EVP_PKEY_meth_get functions have no return values. For the 'get' functions, function pointers are returned by arguments.

# COPYRIGHT

Copyright 2017-2019 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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.