crypto: rsa - allow only odd e and restrict value in FIPS mode
check if rsa public exponent is odd and check its value is between
2^16 < e < 2^256.
FIPS 186-5 DSS (page 35)[1] specify that:
1. The public exponent e shall be selected with the following constraints:
(a) The public verification exponent e shall be selected prior to
generating the primes, p and q, and the private signature exponent
d.
(b) The exponent e shall be an odd positive integer such that:
2^16 < e < 2^256.
[1] https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.186-5.pdf
Signed-off-by: Mahmoud Adam <mngyadam@amazon.com>
Reviewed-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>