Commit 6637e11e authored by Mahmoud Adam's avatar Mahmoud Adam Committed by Herbert Xu
Browse files

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: default avatarMahmoud Adam <mngyadam@amazon.com>
Reviewed-by: default avatarStephan Mueller <smueller@chronox.de>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent ba51738f

crypto/rsa.c

+36 −0
Original line number Diff line number Diff line
@@ -205,6 +205,32 @@ static int rsa_check_key_length(unsigned int len) 
	return -EINVAL;

}



static int rsa_check_exponent_fips(MPI e)

{

	MPI e_max = NULL;



	/* check if odd */

	if (!mpi_test_bit(e, 0)) {

		return -EINVAL;

	}



	/* check if 2^16 < e < 2^256. */

	if (mpi_cmp_ui(e, 65536) <= 0) {

		return -EINVAL;

	}



	e_max = mpi_alloc(0);

	mpi_set_bit(e_max, 256);



	if (mpi_cmp(e, e_max) >= 0) {

		mpi_free(e_max);

		return -EINVAL;

	}



	mpi_free(e_max);

	return 0;

}



static int rsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,

			   unsigned int keylen)

{
@@ -232,6 +258,11 @@ static int rsa_set_pub_key(struct crypto_akcipher *tfm, const void *key, 
		return -EINVAL;

	}



	if (fips_enabled && rsa_check_exponent_fips(mpi_key->e)) {

		rsa_free_mpi_key(mpi_key);

		return -EINVAL;

	}



	return 0;



err:
@@ -290,6 +321,11 @@ static int rsa_set_priv_key(struct crypto_akcipher *tfm, const void *key, 
		return -EINVAL;

	}



	if (fips_enabled && rsa_check_exponent_fips(mpi_key->e)) {

		rsa_free_mpi_key(mpi_key);

		return -EINVAL;

	}



	return 0;



err: