EVP_PKEY_ASN1_METHOD(3)

NAME
EVP_PKEY_ASN1_METHOD, EVP_PKEY_asn1_new, EVP_PKEY_asn1_copy, EVP_PKEY_asn1_free, EVP_PKEY_asn1_add0, EVP_PKEY_asn1_add_alias, EVP_PKEY_asn1_set_public, EVP_PKEY_asn1_set_private, EVP_PKEY_asn1_set_param, EVP_PKEY_asn1_set_free, EVP_PKEY_asn1_set_ctrl, EVP_PKEY_asn1_set_item, EVP_PKEY_asn1_set_siginf, EVP_PKEY_asn1_set_check, EVP_PKEY_asn1_set_public_check, EVP_PKEY_asn1_set_param_check, EVP_PKEY_asn1_set_security_bits, EVP_PKEY_asn1_set_set_priv_key, EVP_PKEY_asn1_set_set_pub_key, EVP_PKEY_asn1_set_get_priv_key, EVP_PKEY_asn1_set_get_pub_key, EVP_PKEY_get0_asn1 - manipulating and registering EVP_PKEY_ASN1_METHOD structure

LIBRARY
libcrypto, -lcrypto

SYNOPSIS
 #include <openssl/evp.h>

 typedef struct evp_pkey_asn1_method_st EVP_PKEY_ASN1_METHOD;

 EVP_PKEY_ASN1_METHOD *EVP_PKEY_asn1_new(int id, int flags,
                                         const char *pem_str,
                                         const char *info);
 void EVP_PKEY_asn1_copy(EVP_PKEY_ASN1_METHOD *dst,
                         const EVP_PKEY_ASN1_METHOD *src);
 void EVP_PKEY_asn1_free(EVP_PKEY_ASN1_METHOD *ameth);
 int EVP_PKEY_asn1_add0(const EVP_PKEY_ASN1_METHOD *ameth);
 int EVP_PKEY_asn1_add_alias(int to, int from);

 void EVP_PKEY_asn1_set_public(EVP_PKEY_ASN1_METHOD *ameth,
                               int (*pub_decode) (EVP_PKEY *pk,
                                                  X509_PUBKEY *pub),
                               int (*pub_encode) (X509_PUBKEY *pub,
                                                  const EVP_PKEY *pk),
                               int (*pub_cmp) (const EVP_PKEY *a,
                                               const EVP_PKEY *b),
                               int (*pub_print) (BIO *out,
                                                 const EVP_PKEY *pkey,
                                                 int indent, ASN1_PCTX *pctx),
                               int (*pkey_size) (const EVP_PKEY *pk),
                               int (*pkey_bits) (const EVP_PKEY *pk));
 void EVP_PKEY_asn1_set_private(EVP_PKEY_ASN1_METHOD *ameth,
                                int (*priv_decode) (EVP_PKEY *pk,
                                                    const PKCS8_PRIV_KEY_INFO
                                                    *p8inf),
                                int (*priv_encode) (PKCS8_PRIV_KEY_INFO *p8,
                                                    const EVP_PKEY *pk),
                                int (*priv_print) (BIO *out,
                                                   const EVP_PKEY *pkey,
                                                   int indent,
                                                   ASN1_PCTX *pctx));
 void EVP_PKEY_asn1_set_param(EVP_PKEY_ASN1_METHOD *ameth,
                              int (*param_decode) (EVP_PKEY *pkey,
                                                   const unsigned char **pder,
                                                   int derlen),
                              int (*param_encode) (const EVP_PKEY *pkey,
                                                   unsigned char **pder),
                              int (*param_missing) (const EVP_PKEY *pk),
                              int (*param_copy) (EVP_PKEY *to,
                                                 const EVP_PKEY *from),
                              int (*param_cmp) (const EVP_PKEY *a,
                                                const EVP_PKEY *b),
                              int (*param_print) (BIO *out,
                                                  const EVP_PKEY *pkey,
                                                  int indent,
                                                  ASN1_PCTX *pctx));

 void EVP_PKEY_asn1_set_free(EVP_PKEY_ASN1_METHOD *ameth,
                             void (*pkey_free) (EVP_PKEY *pkey));
 void EVP_PKEY_asn1_set_ctrl(EVP_PKEY_ASN1_METHOD *ameth,
                             int (*pkey_ctrl) (EVP_PKEY *pkey, int op,
                                               long arg1, void *arg2));
 void EVP_PKEY_asn1_set_item(EVP_PKEY_ASN1_METHOD *ameth,
                             int (*item_verify) (EVP_MD_CTX *ctx,
                                                 const ASN1_ITEM *it,
                                                 void *asn,
                                                 X509_ALGOR *a,
                                                 ASN1_BIT_STRING *sig,
                                                 EVP_PKEY *pkey),
                             int (*item_sign) (EVP_MD_CTX *ctx,
                                               const ASN1_ITEM *it,
                                               void *asn,
                                               X509_ALGOR *alg1,
                                               X509_ALGOR *alg2,
                                               ASN1_BIT_STRING *sig));

 void EVP_PKEY_asn1_set_siginf(EVP_PKEY_ASN1_METHOD *ameth,
                               int (*siginf_set) (X509_SIG_INFO *siginf,
                                                  const X509_ALGOR *alg,
                                                  const ASN1_STRING *sig));

 void EVP_PKEY_asn1_set_check(EVP_PKEY_ASN1_METHOD *ameth,
                              int (*pkey_check) (const EVP_PKEY *pk));

 void EVP_PKEY_asn1_set_public_check(EVP_PKEY_ASN1_METHOD *ameth,
                                     int (*pkey_pub_check) (const EVP_PKEY *pk));

 void EVP_PKEY_asn1_set_param_check(EVP_PKEY_ASN1_METHOD *ameth,
                                    int (*pkey_param_check) (const EVP_PKEY *pk));

 void EVP_PKEY_asn1_set_security_bits(EVP_PKEY_ASN1_METHOD *ameth,
                                      int (*pkey_security_bits) (const EVP_PKEY
                                                                 *pk));

 void EVP_PKEY_asn1_set_set_priv_key(EVP_PKEY_ASN1_METHOD *ameth,
                                     int (*set_priv_key) (EVP_PKEY *pk,
                                                          const unsigned char
                                                             *priv,
                                                          size_t len));

 void EVP_PKEY_asn1_set_set_pub_key(EVP_PKEY_ASN1_METHOD *ameth,
                                    int (*set_pub_key) (EVP_PKEY *pk,
                                                        const unsigned char *pub,
                                                        size_t len));

 void EVP_PKEY_asn1_set_get_priv_key(EVP_PKEY_ASN1_METHOD *ameth,
                                     int (*get_priv_key) (const EVP_PKEY *pk,
                                                          unsigned char *priv,
                                                          size_t *len));

 void EVP_PKEY_asn1_set_get_pub_key(EVP_PKEY_ASN1_METHOD *ameth,
                                    int (*get_pub_key) (const EVP_PKEY *pk,
                                                        unsigned char *pub,
                                                        size_t *len));

 const EVP_PKEY_ASN1_METHOD *EVP_PKEY_get0_asn1(const EVP_PKEY *pkey);

DESCRIPTION
EVP_PKEY_ASN1_METHOD is a structure which holds a set of ASN.1 conversion, printing and information methods for a specific public key algorithm.

There are two places where the EVP_PKEY_ASN1_METHOD objects are stored: one is a built-in 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_asn1_add0(3).

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

 int (*pub_decode) (EVP_PKEY *pk, X509_PUBKEY *pub);
 int (*pub_encode) (X509_PUBKEY *pub, const EVP_PKEY *pk);
 int (*pub_cmp) (const EVP_PKEY *a, const EVP_PKEY *b);
 int (*pub_print) (BIO *out, const EVP_PKEY *pkey, int indent,
                   ASN1_PCTX *pctx);

The pub_decode() and pub_encode() methods are called to decode / encode X509_PUBKEY ASN.1 parameters to / from pk. They MUST return 0 on error, 1 on success. They're called by X509_PUBKEY_get0(3) and X509_PUBKEY_set(3).

The pub_cmp() method is called when two public keys are to be compared. It MUST return 1 when the keys are equal, 0 otherwise. It's called by EVP_PKEY_cmp(3).

The pub_print() method is called to print a public key in humanly readable text to out, indented indent spaces. It MUST return 0 on error, 1 on success. It's called by EVP_PKEY_print_public(3).

 int (*priv_decode) (EVP_PKEY *pk, const PKCS8_PRIV_KEY_INFO *p8inf);
 int (*priv_encode) (PKCS8_PRIV_KEY_INFO *p8, const EVP_PKEY *pk);
 int (*priv_print) (BIO *out, const EVP_PKEY *pkey, int indent,
                    ASN1_PCTX *pctx);

The priv_decode() and priv_encode() methods are called to decode / encode PKCS8_PRIV_KEY_INFO form private key to / from pk. They MUST return 0 on error, 1 on success. They're called by EVP_PKCS82PKEY(3) and EVP_PKEY2PKCS8(3).

The priv_print() method is called to print a private key in humanly readable text to out, indented indent spaces. It MUST return 0 on error, 1 on success. It's called by EVP_PKEY_print_private(3).

 int (*pkey_size) (const EVP_PKEY *pk);
 int (*pkey_bits) (const EVP_PKEY *pk);
 int (*pkey_security_bits) (const EVP_PKEY *pk);

The pkey_size() method returns the key size in bytes. It's called by EVP_PKEY_size(3).

The pkey_bits() method returns the key size in bits. It's called by EVP_PKEY_bits(3).

 int (*param_decode) (EVP_PKEY *pkey,
                      const unsigned char **pder, int derlen);
 int (*param_encode) (const EVP_PKEY *pkey, unsigned char **pder);
 int (*param_missing) (const EVP_PKEY *pk);
 int (*param_copy) (EVP_PKEY *to, const EVP_PKEY *from);
 int (*param_cmp) (const EVP_PKEY *a, const EVP_PKEY *b);
 int (*param_print) (BIO *out, const EVP_PKEY *pkey, int indent,
                     ASN1_PCTX *pctx);

The param_decode() and param_encode() methods are called to decode / encode DER formatted parameters to / from pk. They MUST return 0 on error, 1 on success. They're called by PEM_read_bio_Parameters(3) and the file: OSSL_STORE_LOADER(3).

The param_missing() method returns 0 if a key parameter is missing, otherwise 1. It's called by EVP_PKEY_missing_parameters(3).

The param_copy() method copies key parameters from from to to. It MUST return 0 on error, 1 on success. It's called by EVP_PKEY_copy_parameters(3).

The param_cmp() method compares the parameters of keys a and b. It MUST return 1 when the keys are equal, 0 when not equal, or a negative number on error. It's called by EVP_PKEY_cmp_parameters(3).

The param_print() method prints the private key parameters in humanly readable text to out, indented indent spaces. It MUST return 0 on error, 1 on success. It's called by EVP_PKEY_print_params(3).

 int (*sig_print) (BIO *out,
                   const X509_ALGOR *sigalg, const ASN1_STRING *sig,
                   int indent, ASN1_PCTX *pctx);

The sig_print() method prints a signature in humanly readable text to out, indented indent spaces. sigalg contains the exact signature algorithm. If the signature in sig doesn't correspond to what this method expects, X509_signature_dump() must be used as a last resort. It MUST return 0 on error, 1 on success. It's called by X509_signature_print(3).

 void (*pkey_free) (EVP_PKEY *pkey);

The pkey_free() method helps freeing the internals of pkey. It's called by EVP_PKEY_free(3), EVP_PKEY_set_type(3), EVP_PKEY_set_type_str(3), and EVP_PKEY_assign(3).

 int (*pkey_ctrl) (EVP_PKEY *pkey, int op, long arg1, void *arg2);

The pkey_ctrl() method adds extra algorithm specific control. It's called by EVP_PKEY_get_default_digest_nid(3), EVP_PKEY_set1_tls_encodedpoint(3), EVP_PKEY_get1_tls_encodedpoint(3), PKCS7_SIGNER_INFO_set(3), PKCS7_RECIP_INFO_set(3), ...

 int (*old_priv_decode) (EVP_PKEY *pkey,
                         const unsigned char **pder, int derlen);
 int (*old_priv_encode) (const EVP_PKEY *pkey, unsigned char **pder);

The old_priv_decode() and old_priv_encode() methods decode / encode they private key pkey from / to a DER formatted array. These are exclusively used to help decoding / encoding older (pre PKCS#8) PEM formatted encrypted private keys. old_priv_decode() MUST return 0 on error, 1 on success. old_priv_encode() MUST the return same kind of values as i2d_PrivateKey(). They're called by d2i_PrivateKey(3) and i2d_PrivateKey(3).

 int (*item_verify) (EVP_MD_CTX *ctx, const ASN1_ITEM *it, void *asn,
                     X509_ALGOR *a, ASN1_BIT_STRING *sig, EVP_PKEY *pkey);
 int (*item_sign) (EVP_MD_CTX *ctx, const ASN1_ITEM *it, void *asn,
                   X509_ALGOR *alg1, X509_ALGOR *alg2,
                   ASN1_BIT_STRING *sig);

The item_sign() and item_verify() methods make it possible to have algorithm specific signatures and verification of them.

item_sign() MUST return one of:

<=0 error

1   item_sign() did everything, OpenSSL internals just needs to pass the signature length back.

2   item_sign() did nothing, OpenSSL internal standard routines are expected to continue with the default signature production.

3   item_sign() set the algorithm identifier algor1 and algor2, OpenSSL internals should just sign using those algorithms.

item_verify() MUST return one of:

<=0 error

1   item_sign() did everything, OpenSSL internals just needs to pass the signature length back.

2   item_sign() did nothing, OpenSSL internal standard routines are expected to continue with the default signature production.

item_verify() and item_sign() are called by ASN1_item_verify(3) and ASN1_item_sign(3), and by extension, X509_verify(3), X509_REQ_verify(3), X509_sign(3), X509_REQ_sign(3), ...

 int (*siginf_set) (X509_SIG_INFO *siginf, const X509_ALGOR *alg,
                    const ASN1_STRING *sig);

The siginf_set() method is used to set custom X509_SIG_INFO parameters. It MUST return 0 on error, or 1 on success. It's called as part of X509_check_purpose(3), X509_check_ca(3) and X509_check_issued(3).

 int (*pkey_check) (const EVP_PKEY *pk);
 int (*pkey_public_check) (const EVP_PKEY *pk);
 int (*pkey_param_check) (const EVP_PKEY *pk);

The pkey_check(), pkey_public_check() and pkey_param_check() methods are used to check the validity of pk for key-pair, public component and parameters, respectively. They MUST return 0 for an invalid key, or 1 for a valid key. They are called by EVP_PKEY_check(3), EVP_PKEY_public_check(3) and EVP_PKEY_param_check(3) respectively.

 int (*set_priv_key) (EVP_PKEY *pk, const unsigned char *priv, size_t len);
 int (*set_pub_key) (EVP_PKEY *pk, const unsigned char *pub, size_t len);

The set_priv_key() and set_pub_key() methods are used to set the raw private and public key data for an EVP_PKEY. They MUST return 0 on error, or 1 on success. They are called by EVP_PKEY_new_raw_private_key(3), and EVP_PKEY_new_raw_public_key(3) respectively.

  Functions
EVP_PKEY_asn1_new() creates and returns a new EVP_PKEY_ASN1_METHOD object, and associates the given id, flags, pem_str and info. id is a NID, pem_str is the PEM type string, info is a descriptive string. The following flags are supported:

 ASN1_PKEY_SIGPARAM_NULL

If ASN1_PKEY_SIGPARAM_NULL is set, then the signature algorithm parameters are given the type V_ASN1_NULL by default, otherwise they will be given the type V_ASN1_UNDEF (i.e. the parameter is omitted). See X509_ALGOR_set0(3) for more information.

EVP_PKEY_asn1_copy() copies an EVP_PKEY_ASN1_METHOD object from src to dst. This function is not thread safe, it's recommended to only use this when initializing the application.

EVP_PKEY_asn1_free() frees an existing EVP_PKEY_ASN1_METHOD pointed by ameth.

EVP_PKEY_asn1_add0() adds ameth to the user defined stack of methods unless another EVP_PKEY_ASN1_METHOD with the same NID is already there. This function is not thread safe, it's recommended to only use this when initializing the application.

EVP_PKEY_asn1_add_alias() creates an alias with the NID to for the EVP_PKEY_ASN1_METHOD with NID from unless another EVP_PKEY_ASN1_METHOD with the same NID is already added. This function is not thread safe, it's recommended to only use this when initializing the application.

EVP_PKEY_asn1_set_public(), EVP_PKEY_asn1_set_private(), EVP_PKEY_asn1_set_param(), EVP_PKEY_asn1_set_free(), EVP_PKEY_asn1_set_ctrl(), EVP_PKEY_asn1_set_item(), EVP_PKEY_asn1_set_siginf(), EVP_PKEY_asn1_set_check(), EVP_PKEY_asn1_set_public_check(), EVP_PKEY_asn1_set_param_check(), EVP_PKEY_asn1_set_security_bits(), EVP_PKEY_asn1_set_set_priv_key(), EVP_PKEY_asn1_set_set_pub_key(), EVP_PKEY_asn1_set_get_priv_key() and EVP_PKEY_asn1_set_get_pub_key() set the diverse methods of the given EVP_PKEY_ASN1_METHOD object.

EVP_PKEY_get0_asn1() finds the EVP_PKEY_ASN1_METHOD associated with the key pkey.

RETURN VALUES
EVP_PKEY_asn1_new() returns NULL on error, or a pointer to an EVP_PKEY_ASN1_METHOD object otherwise.

EVP_PKEY_asn1_add0() and EVP_PKEY_asn1_add_alias() return 0 on error, or 1 on success.

EVP_PKEY_get0_asn1() returns NULL on error, or a pointer to a constant EVP_PKEY_ASN1_METHOD object otherwise.

COPYRIGHT
Copyright 2017-2018 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>.