File nss-fips-rsa-keygen-strictness.patch of Package mozilla-nss.15194
commit 4b8c0eac6b092717157b4141c82b4d76ccdc91b3
Author: Hans Petter Jansson <hpj@cl.no>
Date: Sun Mar 15 21:54:30 2020 +0100
Patch 16: nss-fips-rsa-keygen-strictness.patch
diff --git a/nss/lib/freebl/mpi/mpprime.c b/nss/lib/freebl/mpi/mpprime.c
index 9d6232c..ccb0b53 100644
--- a/nss/lib/freebl/mpi/mpprime.c
+++ b/nss/lib/freebl/mpi/mpprime.c
@@ -14,6 +14,8 @@
#include <stdlib.h>
#include <string.h>
+#include "../fips.h"
+
#define SMALL_TABLE 0 /* determines size of hard-wired prime table */
#define RANDOM() rand()
@@ -451,6 +453,25 @@ mpp_make_prime(mp_int *start, mp_size nBits, mp_size strong)
} else
num_tests = 50;
+ /* FIPS 186-4 mandates more M-R tests for probable primes generation - make
+ * sure the minimums are observed (see Appendix C, tables C.1 and C.2).
+ * For DSA this is handled in pqg_ParamGen() through the use of
+ * prime_testcount_p() and prime_testcount_q() respectively.
+ * For RSA this unfortunately seems to be the right place to prevent larger
+ * code changes. On the other hand, it seems to generally speed things up,
+ * since there are measurably less errors while calculating inverse modulo in
+ * rsa_build_from_primes().
+ */
+ if (FIPS_mode()) {
+ if (nBits >= 1536)
+ i = 4;
+ else
+ i = 5;
+ if (i > num_tests)
+ num_tests = i;
+ i = 0;
+ }
+
if (strong)
--nBits;
MP_CHECKOK(mpl_set_bit(start, nBits - 1, 1));
diff --git a/nss/lib/freebl/rsa.c b/nss/lib/freebl/rsa.c
index a08636d..b74641a 100644
--- a/nss/lib/freebl/rsa.c
+++ b/nss/lib/freebl/rsa.c
@@ -16,11 +16,13 @@
#include "prinit.h"
#include "blapi.h"
#include "mpi.h"
+#include "mpi-priv.h"
#include "mpprime.h"
#include "mplogic.h"
#include "secmpi.h"
#include "secitem.h"
#include "blapii.h"
+#include "fips.h"
/*
** Number of times to attempt to generate a prime (p or q) from a random
@@ -143,11 +145,24 @@ rsa_build_from_primes(const mp_int *p, const mp_int *q,
err = mp_invmod(d, &phi, e);
} else {
err = mp_invmod(e, &phi, d);
- }
+ /* FIPS 186-4 (B.3.1.3.a) places additional requirements on the
+ * private exponent d:
+ * 2^(n/2) < d < lcm(p-1, q-1) = phi
+ */
+ if (FIPS_mode() && (MP_OKAY == err)) {
+ CHECK_MPI_OK( mp_2expt(&tmp, keySizeInBits / 2) );
+ if ((mp_cmp(d, &tmp) <= 0) || (mp_cmp(d, &phi) >= 0)) {
+ /* new set of p, q is needed for another calculation of d */
+ err = MP_UNDEF;
+ }
+ }
+ }
} else {
err = MP_OKAY;
}
- /* Verify that phi(n) and e have no common divisors */
+ /* Verify that phi(n) and e have no common divisors
+ * This is also the coprimality constraint from FIPS 186-4 (B.3.1.2.a)
+ */
if (err != MP_OKAY) {
if (err == MP_UNDEF) {
PORT_SetError(SEC_ERROR_NEED_RANDOM);
@@ -280,10 +295,12 @@ RSA_NewKey(int keySizeInBits, SECItem *publicExponent)
mp_int q = { 0, 0, 0, NULL };
mp_int e = { 0, 0, 0, NULL };
mp_int d = { 0, 0, 0, NULL };
+ mp_int u = { 0, 0, 0, NULL };
+ mp_int v = { 0, 0, 0, NULL };
int kiter;
int max_attempts;
mp_err err = MP_OKAY;
- SECStatus rv = SECSuccess;
+ SECStatus rv = SECFailure;
int prerr = 0;
RSAPrivateKey *key = NULL;
PLArenaPool *arena = NULL;
@@ -301,11 +318,40 @@ RSA_NewKey(int keySizeInBits, SECItem *publicExponent)
PORT_SetError(SEC_ERROR_INVALID_ARGS);
goto cleanup;
}
+
+ MP_DIGITS(&p) = 0;
+ MP_DIGITS(&q) = 0;
+ MP_DIGITS(&d) = 0;
+ MP_DIGITS(&u) = 0;
+ MP_DIGITS(&v) = 0;
+ CHECK_MPI_OK(mp_init(&p));
+ CHECK_MPI_OK(mp_init(&q));
+ CHECK_MPI_OK(mp_init(&d));
+ CHECK_MPI_OK(mp_init(&u));
+ CHECK_MPI_OK(mp_init(&v));
+
#ifndef NSS_FIPS_DISABLED
- /* Check that the exponent is not smaller than 65537 */
- if (mp_cmp_d(&e, 0x10001) < 0) {
- PORT_SetError(SEC_ERROR_INVALID_ARGS);
- goto cleanup;
+ if (FIPS_mode()) {
+ /* Check that the exponent is not smaller than 65537 */
+ if (mp_cmp_d(&e, 0x10001) < 0) {
+ PORT_SetError(SEC_ERROR_INVALID_ARGS);
+ goto cleanup;
+ }
+
+ /* FIPS 186-4 requires 2^16 < e < 2^256 (B.3.1.1.b) */
+ CHECK_MPI_OK( mp_2expt(&v, 256) );
+ if (!(mp_cmp(&e, &v) < 0 )) {
+ err = MP_BADARG;
+ goto cleanup;
+ }
+
+ /* FIPS 186-4 mandates keys to be either 2048, 3072 or 4096 bits long.
+ * We also allow a key length of 4096, since this is needed in order to
+ * pass the CAVS RSA SigGen test. */
+ if (keySizeInBits < 2048) {
+ PORT_SetError(SEC_ERROR_INVALID_ARGS);
+ goto cleanup;
+ }
}
#endif
@@ -323,12 +369,7 @@ RSA_NewKey(int keySizeInBits, SECItem *publicExponent)
key->arena = arena;
/* length of primes p and q (in bytes) */
primeLen = keySizeInBits / (2 * PR_BITS_PER_BYTE);
- MP_DIGITS(&p) = 0;
- MP_DIGITS(&q) = 0;
- MP_DIGITS(&d) = 0;
- CHECK_MPI_OK(mp_init(&p));
- CHECK_MPI_OK(mp_init(&q));
- CHECK_MPI_OK(mp_init(&d));
+
/* 3. Set the version number (PKCS1 v1.5 says it should be zero) */
SECITEM_AllocItem(arena, &key->version, 1);
key->version.data[0] = 0;
@@ -339,13 +380,64 @@ RSA_NewKey(int keySizeInBits, SECItem *publicExponent)
PORT_SetError(0);
CHECK_SEC_OK(generate_prime(&p, primeLen));
CHECK_SEC_OK(generate_prime(&q, primeLen));
- /* Assure p > q */
+ /* Assure p >= q */
/* NOTE: PKCS #1 does not require p > q, and NSS doesn't use any
* implementation optimization that requires p > q. We can remove
* this code in the future.
*/
if (mp_cmp(&p, &q) < 0)
mp_exch(&p, &q);
+
+ /* FIPS 186-4 puts additional requirements on the primes (B.3.1.2.a-d)
+ * (n = key bit length):
+ * 1) both (p-1) and (q-1) are coprime to e (B.3.1.2.a), i.e.:
+ * gcd(p-1,e) = 1, gcd(q-1,e) = 1
+ * this is ensured in rsa_build_from_primes(), where
+ * phi = lcm(p-1)(q-1) is tested for coprimality to e
+ * 2) magnitude constraint (B.3.1.2.b and B.3.1.2.c):
+ * both p and q are from open the interval
+ * I = ( sqrt(2) * 2^(n/2 - 1) , 2^(n/2 - 1) )
+ * 3) minimum distance (B.3.1.2.d): abs(p-q) > 2 ^ (n/2 - 100)
+ */
+ if (FIPS_mode()) {
+ /* 2 */
+ /* in order not to constrain the selection too much,
+ * expand the inequality:
+ * x > 2^(1/2) * 2^(n/2 - 1)
+ * = 2^(1/2 + k) * 2^(n/2 - k - 1)
+ * = y(k) * r(k)
+ * for z(k) >= y(k) it clearly holds:
+ * x > z(k) * r(k)
+ * one suitable z(k) such that z(k)/y(k) - 1 = o(1) is
+ * ceil(y(k)) for big-enough k
+ * ceil(y(30))/y(30) - 1 < 10^-10, so lets use that
+ * 2^30.5 = 1518500249.98802484622388101120...
+ * the magic constant is thus z(30) = 1518500250 < 2^31
+ *
+ * Additionally, since p >= q is required above, the
+ * condtitions can be shortened to:
+ * 1518500250 * 2^(n/2 - 31) = v < q
+ * p < u = 2^(n/2 - 1)
+ */
+ CHECK_MPI_OK( mp_2expt(&u, keySizeInBits / 2 - 31) );
+ CHECK_MPI_OK( mp_mul_d(&u, 1518500250, &v) );
+ CHECK_MPI_OK( mp_2expt(&u, keySizeInBits / 2) );
+ if ((mp_cmp(&q, &v) <= 0) || (mp_cmp(&p, &u) >= 0)) {
+ prerr = SEC_ERROR_NEED_RANDOM; /* retry with different values */
+ kiter++;
+ continue;
+ }
+ /* 3 */
+ CHECK_MPI_OK( mp_sub(&p, &q, &u) );
+ CHECK_MPI_OK( mp_abs(&u, &u) );
+ CHECK_MPI_OK( mp_2expt(&v, keySizeInBits / 2 - 100) );
+ if (mp_cmp(&u, &v) < 0) {
+ prerr = SEC_ERROR_NEED_RANDOM; /* retry with different values */
+ kiter++;
+ continue;
+ }
+ }
+
/* Attempt to use these primes to generate a key */
rv = rsa_build_from_primes(&p, &q,
&e, PR_FALSE, /* needPublicExponent=false */
@@ -368,7 +460,9 @@ cleanup:
mp_clear(&q);
mp_clear(&e);
mp_clear(&d);
- if (err) {
+ mp_clear(&u);
+ mp_clear(&v);
+ if (err != MP_OKAY) {
MP_TO_SEC_ERROR(err);
rv = SECFailure;
}
