RSA_check_key_ex, RSA_check_key - validate private RSA keys
 #include <openssl/rsa.h>
 int RSA_check_key_ex(RSA *rsa, BN_GENCB *cb);
 int RSA_check_key(RSA *rsa);
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)
RSA_check_key_ex() appeared after OpenSSL 1.0.2.
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Licensed under the OpenSSL license (the "License"). You
    may not use this file except in compliance with the License. You can obtain
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