RSA_check_key_ex, RSA_check_key - validate private RSA keys
 #include <openssl/rsa.h>
The following functions have been deprecated since OpenSSL 3.0,
    and can be hidden entirely by defining OPENSSL_API_COMPAT with a
    suitable version value, see openssl_user_macros(7):
 int RSA_check_key_ex(const RSA *rsa, BN_GENCB *cb);
 int RSA_check_key(const RSA *rsa);
Both of the functions described on this page are deprecated. Applications should
  instead use EVP_PKEY_public_check(3), EVP_PKEY_private_check(3)
  and EVP_PKEY_pairwise_check(3).
RSA_check_key_ex() function validates RSA keys. It checks
    that p and q are in fact prime, and that n = p*q.
It does not work on RSA public keys that have only the modulus and
    public exponent elements populated. It also checks that d*e = 1 mod
    (p-1*q-1), and that dmp1, dmq1 and iqmp are set
    correctly or are NULL. It performs integrity checks on all the RSA
    key material, so the RSA key structure must contain all the private key data
    too. Therefore, it cannot be used with any arbitrary RSA key object, even if
    it is otherwise fit for regular RSA operation.
The cb parameter is a callback that will be invoked in the
    same manner as BN_is_prime_ex(3).
RSA_check_key() is equivalent to RSA_check_key_ex()
    with a NULL cb.
RSA_check_key_ex() and RSA_check_key() return 1 if rsa is a
  valid RSA key, and 0 otherwise. They return -1 if an error occurs while
  checking the key.
If the key is invalid or an error occurred, the reason code can be
    obtained using ERR_get_error(3).
Unlike most other RSA functions, this function does not work
  transparently with any underlying ENGINE implementation because it uses the
  key data in the RSA structure directly. An ENGINE implementation can override
  the way key data is stored and handled, and can even provide support for HSM
  keys - in which case the RSA structure may contain no key data at all!
  If the ENGINE in question is only being used for acceleration or analysis
  purposes, then in all likelihood the RSA key data is complete and untouched,
  but this can't be assumed in the general case.
A method of verifying the RSA key using opaque RSA API functions might need to
  be considered. Right now RSA_check_key() simply uses the RSA structure
  elements directly, bypassing the RSA_METHOD table altogether (and completely
  violating encapsulation and object-orientation in the process). The best fix
  will probably be to introduce a "check_key()" handler to the
  RSA_METHOD function table so that alternative implementations can also provide
  their own verifiers.
BN_is_prime_ex(3), ERR_get_error(3)
All of these functions were deprecated in OpenSSL 3.0.
RSA_check_key_ex() appeared after OpenSSL 1.0.2.
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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>.