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crypto: rsa - allow only odd e and restrict value in FIPS mode

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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>
This commit is contained in:
Mahmoud Adam 2023-06-13 16:17:31 +00:00 committed by Herbert Xu
parent ba51738fa7
commit 6637e11e4a
1 changed files with 36 additions and 0 deletions
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36
crypto/rsa.c
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@ -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: