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RSA_check_key - validate private RSA keys
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#include <openssl/rsa.h>
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int RSA_check_key(RSA *rsa);
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This function validates RSA keys. It checks that B<p> and B<q> are
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in fact prime, and that B<n = p*q>.
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It also checks that B<d*e = 1 mod (p-1*q-1)>,
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and that B<dmp1>, B<dmq1> and B<iqmp> are set correctly or are B<NULL>.
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As such, this function can not be used with any arbitrary RSA key object,
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even if it is otherwise fit for regular RSA operation. See B<NOTES> for more
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RSA_check_key() returns 1 if B<rsa> is a valid RSA key, and 0 otherwise.
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-1 is returned if an error occurs while checking the key.
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If the key is invalid or an error occurred, the reason code can be
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obtained using L<ERR_get_error(3)|ERR_get_error(3)>.
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This function does not work on RSA public keys that have only the modulus
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and public exponent elements populated. It performs integrity checks on all
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the RSA key material, so the RSA key structure must contain all the private
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Unlike most other RSA functions, this function does B<not> work
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transparently with any underlying ENGINE implementation because it uses the
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key data in the RSA structure directly. An ENGINE implementation can
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override the way key data is stored and handled, and can even provide
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support for HSM keys - in which case the RSA structure may contain B<no>
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key data at all! If the ENGINE in question is only being used for
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acceleration or analysis purposes, then in all likelihood the RSA key data
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is complete and untouched, but this can't be assumed in the general case.
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A method of verifying the RSA key using opaque RSA API functions might need
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to be considered. Right now RSA_check_key() simply uses the RSA structure
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elements directly, bypassing the RSA_METHOD table altogether (and
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completely violating encapsulation and object-orientation in the process).
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The best fix will probably be to introduce a "check_key()" handler to the
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RSA_METHOD function table so that alternative implementations can also
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provide their own verifiers.
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L<rsa(3)|rsa(3)>, L<ERR_get_error(3)|ERR_get_error(3)>
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RSA_check_key() appeared in OpenSSL 0.9.4.