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@xxxxxxxxxx> --- crypto/rsa.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/crypto/rsa.c b/crypto/rsa.c index c50f2d2a4d06..c79613cdce6e 100644 --- a/crypto/rsa.c +++ b/crypto/rsa.c @@ -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: -- 2.40.1
