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NAME

       RSA_check_key_ex, RSA_check_key - validate private RSA keys

SYNOPSIS

        #include <openssl/rsa.h>

        int RSA_check_key_ex(RSA *rsa, BN_GENCB *cb);

        int RSA_check_key(RSA *rsa);

DESCRIPTION

       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.

RETURN VALUES

       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).

NOTES

       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.

BUGS

       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.

SEE ALSO

       BN_is_prime_ex(3), ERR_get_error(3)

HISTORY

       RSA_check_key_ex() appeared after OpenSSL 1.0.2.

COPYRIGHT

       Copyright 2000-2018 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>.