1=pod
2
3=head1 NAME
4
5RSA_check_key - validate private RSA keys
6
7=head1 SYNOPSIS
8
9 #include <openssl/rsa.h>
10
11 int RSA_check_key(RSA *rsa);
12
13=head1 DESCRIPTION
14
15This function validates RSA keys. It checks that B<p> and B<q> are
16in fact prime, and that B<n = p*q>.
17
18It also checks that B<d*e = 1 mod (p-1*q-1)>,
19and that B<dmp1>, B<dmq1> and B<iqmp> are set correctly or are B<NULL>.
20
21As such, this function can not be used with any arbitrary RSA key object,
22even if it is otherwise fit for regular RSA operation. See B<NOTES> for more
23information.
24
25=head1 RETURN VALUE
26
27RSA_check_key() returns 1 if B<rsa> is a valid RSA key, and 0 otherwise.
28-1 is returned if an error occurs while checking the key.
29
30If the key is invalid or an error occurred, the reason code can be
31obtained using L<ERR_get_error(3)|ERR_get_error(3)>.
32
33=head1 NOTES
34
35This function does not work on RSA public keys that have only the modulus
36and public exponent elements populated. It performs integrity checks on all
37the RSA key material, so the RSA key structure must contain all the private
38key data too.
39
40Unlike most other RSA functions, this function does B<not> work
41transparently with any underlying ENGINE implementation because it uses the
42key data in the RSA structure directly. An ENGINE implementation can
43override the way key data is stored and handled, and can even provide
44support for HSM keys - in which case the RSA structure may contain B<no>
45key data at all! If the ENGINE in question is only being used for
46acceleration or analysis purposes, then in all likelihood the RSA key data
47is complete and untouched, but this can't be assumed in the general case.
48
49=head1 BUGS
50
51A method of verifying the RSA key using opaque RSA API functions might need
52to be considered. Right now RSA_check_key() simply uses the RSA structure
53elements directly, bypassing the RSA_METHOD table altogether (and
54completely violating encapsulation and object-orientation in the process).
55The best fix will probably be to introduce a "check_key()" handler to the
56RSA_METHOD function table so that alternative implementations can also
57provide their own verifiers.
58
59=head1 SEE ALSO
60
61L<rsa(3)|rsa(3)>, L<ERR_get_error(3)|ERR_get_error(3)>
62
63=head1 HISTORY
64
65RSA_check_key() appeared in OpenSSL 0.9.4.
66
67=cut
68