X509_get_pubkey, X509_get0_pubkey, X509_set_pubkey, X509_get_X509_PUBKEY,
  X509_REQ_get_pubkey, X509_REQ_get0_pubkey, X509_REQ_set_pubkey,
  X509_REQ_get_X509_PUBKEY - get or set certificate or certificate request
  public key
 #include <openssl/x509.h>
 EVP_PKEY *X509_get_pubkey(X509 *x);
 EVP_PKEY *X509_get0_pubkey(const X509 *x);
 int X509_set_pubkey(X509 *x, EVP_PKEY *pkey);
 X509_PUBKEY *X509_get_X509_PUBKEY(const X509 *x);
 EVP_PKEY *X509_REQ_get_pubkey(X509_REQ *req);
 EVP_PKEY *X509_REQ_get0_pubkey(X509_REQ *req);
 int X509_REQ_set_pubkey(X509_REQ *x, EVP_PKEY *pkey);
 X509_PUBKEY *X509_REQ_get_X509_PUBKEY(X509_REQ *x);
X509_get_pubkey() attempts to decode the public key for certificate
  x. If successful it returns the public key as an EVP_PKEY
  pointer with its reference count incremented: this means the returned key must
  be freed up after use. X509_get0_pubkey() is similar except it does
  not increment the reference count of the returned EVP_PKEY so it
  must not be freed up after use.
X509_get_X509_PUBKEY() returns an internal pointer to the
    X509_PUBKEY structure which encodes the certificate of x. The
    returned value must not be freed up after use.
X509_set_pubkey() attempts to set the public key for
    certificate x to pkey. The key pkey should be freed up
    after use.
X509_REQ_get_pubkey(), X509_REQ_get0_pubkey(),
    X509_REQ_set_pubkey() and X509_REQ_get_X509_PUBKEY() are
    similar but operate on certificate request req.
The first time a public key is decoded the EVP_PKEY structure is cached
  in the certificate or certificate request itself. Subsequent calls return the
  cached structure with its reference count incremented to improve performance.
X509_get_pubkey(), X509_get0_pubkey(),
  X509_get_X509_PUBKEY(), X509_REQ_get_pubkey() and
  X509_REQ_get_X509_PUBKEY() return a public key or NULL if an
  error occurred.
X509_set_pubkey() and X509_REQ_set_pubkey() return 1
    for success and 0 for failure.
d2i_X509(3), ERR_get_error(3), X509_CRL_get0_by_serial(3),
  X509_get0_signature(3), X509_get_ext_d2i(3),
  X509_get_extension_flags(3), X509_get_subject_name(3),
  X509_get_version(3), X509_NAME_add_entry_by_txt(3),
  X509_NAME_ENTRY_get_object(3), X509_NAME_get_index_by_NID(3),
  X509_NAME_print_ex(3), X509_new(3), X509_sign(3),
  X509V3_get_d2i(3), X509_verify_cert(3)
Copyright 2015-2021 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>.