The branch master has been updated
via 2500c093aa1e9c90c11c415053c0a27a00661d0d (commit)
from 48fdeca01dab31237a711d9fdf4452ebf8443716 (commit)
- Log -----------------------------------------------------------------
commit 2500c093aa1e9c90c11c415053c0a27a00661d0d
Author: Jake Massimo <[email protected]>
Date: Wed Mar 27 04:13:08 2019 +0000
Increase rounds of Miller-Rabin testing DH_check
DH_check is used to test the validity of Diffie-Hellman parameter sets (p,
q, g). Among the tests performed are primality tests on p and q, for this
BN_is_prime_ex is called with the rounds of Miller-Rabin set as default. This
will therefore use the average case error estimates derived from the function
BN_prime_checks_for_size based on the bit size of the number tested.
However, these bounds are only accurate on testing random input. Within
this testing scenario, where we are checking the validity of a DH parameter
set, we can not assert that these parameters are randomly generated. Thus we
must treat them as if they are adversarial in nature and increase the rounds of
Miller-Rabin performed.
Generally, each round of Miller-Rabin can declare a composite number prime
with probability at most (1/4), thus 64 rounds is sufficient in thwarting known
generation techniques (even in safe prime settings - see
https://eprint.iacr.org/2019/032 for full analysis). The choice of 64 rounds is
also consistent with SRP_NUMBER_ITERATIONS_FOR_PRIME 64 as used in
srp_Verify_N_and_g in openssl/apps/s_client.c.
Reviewed-by: Paul Dale <[email protected]>
Reviewed-by: Matt Caswell <[email protected]>
(Merged from https://github.com/openssl/openssl/pull/8593)
-----------------------------------------------------------------------
Summary of changes:
crypto/dh/dh_check.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/crypto/dh/dh_check.c b/crypto/dh/dh_check.c
index cd7f70b..8be2b91 100644
--- a/crypto/dh/dh_check.c
+++ b/crypto/dh/dh_check.c
@@ -12,6 +12,8 @@
#include <openssl/bn.h>
#include "dh_locl.h"
+# define DH_NUMBER_ITERATIONS_FOR_PRIME 64
+
/*-
* Check that p and g are suitable enough
*
@@ -125,7 +127,7 @@ int DH_check(const DH *dh, int *ret)
if (!BN_is_one(t1))
*ret |= DH_NOT_SUITABLE_GENERATOR;
}
- r = BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL);
+ r = BN_is_prime_ex(dh->q, DH_NUMBER_ITERATIONS_FOR_PRIME, ctx, NULL);
if (r < 0)
goto err;
if (!r)
@@ -153,7 +155,7 @@ int DH_check(const DH *dh, int *ret)
} else
*ret |= DH_UNABLE_TO_CHECK_GENERATOR;
- r = BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL);
+ r = BN_is_prime_ex(dh->p, DH_NUMBER_ITERATIONS_FOR_PRIME, ctx, NULL);
if (r < 0)
goto err;
if (!r)
@@ -161,7 +163,7 @@ int DH_check(const DH *dh, int *ret)
else if (!dh->q) {
if (!BN_rshift1(t1, dh->p))
goto err;
- r = BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL);
+ r = BN_is_prime_ex(t1, DH_NUMBER_ITERATIONS_FOR_PRIME, ctx, NULL);
if (r < 0)
goto err;
if (!r)
