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(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 2015-2016 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>.