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-rw-r--r--crypto/bn/bn_rsa_fips186_4.c53
-rw-r--r--crypto/rsa/rsa_sp800_56b_check.c27
-rw-r--r--include/crypto/bn.h3
-rw-r--r--test/rsa_sp800_56b_test.c2
4 files changed, 64 insertions, 21 deletions
diff --git a/crypto/bn/bn_rsa_fips186_4.c b/crypto/bn/bn_rsa_fips186_4.c
index c31b43ba8f..492eb297c3 100644
--- a/crypto/bn/bn_rsa_fips186_4.c
+++ b/crypto/bn/bn_rsa_fips186_4.c
@@ -31,6 +31,27 @@
#include <openssl/bn.h>
#include "bn_local.h"
#include "crypto/bn.h"
+#include "internal/nelem.h"
+
+#if BN_BITS2 == 64
+# define BN_DEF(lo, hi) (BN_ULONG)hi<<32|lo
+#else
+# define BN_DEF(lo, hi) lo, hi
+#endif
+
+/* 1 / sqrt(2) * 2^256, rounded up */
+static const BN_ULONG inv_sqrt_2_val[] = {
+ BN_DEF(0x83339916UL, 0xED17AC85UL), BN_DEF(0x893BA84CUL, 0x1D6F60BAUL),
+ BN_DEF(0x754ABE9FUL, 0x597D89B3UL), BN_DEF(0xF9DE6484UL, 0xB504F333UL)
+};
+
+const BIGNUM bn_inv_sqrt_2 = {
+ (BN_ULONG *)inv_sqrt_2_val,
+ OSSL_NELEM(inv_sqrt_2_val),
+ OSSL_NELEM(inv_sqrt_2_val),
+ 0,
+ BN_FLG_STATIC_DATA
+};
/*
* FIPS 186-4 Table B.1. "Min length of auxiliary primes p1, p2, q1, q2".
@@ -221,9 +242,12 @@ int bn_rsa_fips186_4_derive_prime(BIGNUM *Y, BIGNUM *X, const BIGNUM *Xin,
int i, imax;
int bits = nlen >> 1;
BIGNUM *tmp, *R, *r1r2x2, *y1, *r1x2;
+ BIGNUM *base, *range;
BN_CTX_start(ctx);
+ base = BN_CTX_get(ctx);
+ range = BN_CTX_get(ctx);
R = BN_CTX_get(ctx);
tmp = BN_CTX_get(ctx);
r1r2x2 = BN_CTX_get(ctx);
@@ -235,6 +259,24 @@ int bn_rsa_fips186_4_derive_prime(BIGNUM *Y, BIGNUM *X, const BIGNUM *Xin,
if (Xin != NULL && BN_copy(X, Xin) == NULL)
goto err;
+ /*
+ * We need to generate a random number X in the range
+ * 1/sqrt(2) * 2^(nlen/2) <= X < 2^(nlen/2).
+ * We can rewrite that as:
+ * base = 1/sqrt(2) * 2^(nlen/2)
+ * range = ((2^(nlen/2))) - (1/sqrt(2) * 2^(nlen/2))
+ * X = base + random(range)
+ * We only have the first 256 bit of 1/sqrt(2)
+ */
+ if (Xin == NULL) {
+ if (bits < BN_num_bits(&bn_inv_sqrt_2))
+ goto err;
+ if (!BN_lshift(base, &bn_inv_sqrt_2, bits - BN_num_bits(&bn_inv_sqrt_2))
+ || !BN_lshift(range, BN_value_one(), bits)
+ || !BN_sub(range, range, base))
+ goto err;
+ }
+
if (!(BN_lshift1(r1x2, r1)
/* (Step 1) GCD(2r1, r2) = 1 */
&& BN_gcd(tmp, r1x2, r2, ctx)
@@ -257,16 +299,9 @@ int bn_rsa_fips186_4_derive_prime(BIGNUM *Y, BIGNUM *X, const BIGNUM *Xin,
if (Xin == NULL) {
/*
* (Step 3) Choose Random X such that
- * sqrt(2) * 2^(nlen/2-1) < Random X < (2^(nlen/2)) - 1.
- *
- * For the lower bound:
- * sqrt(2) * 2^(nlen/2 - 1) == sqrt(2)/2 * 2^(nlen/2)
- * where sqrt(2)/2 = 0.70710678.. = 0.B504FC33F9DE...
- * so largest number will have B5... as the top byte
- * Setting the top 2 bits gives 0xC0.
+ * sqrt(2) * 2^(nlen/2-1) <= Random X <= (2^(nlen/2)) - 1.
*/
- if (!BN_priv_rand_ex(X, bits, BN_RAND_TOP_TWO, BN_RAND_BOTTOM_ANY,
- ctx))
+ if (!BN_priv_rand_range_ex(X, range, ctx) || !BN_add(X, X, base))
goto end;
}
/* (Step 4) Y = X + ((R - X) mod 2r1r2) */
diff --git a/crypto/rsa/rsa_sp800_56b_check.c b/crypto/rsa/rsa_sp800_56b_check.c
index d614504bc9..c4c0b6a95b 100644
--- a/crypto/rsa/rsa_sp800_56b_check.c
+++ b/crypto/rsa/rsa_sp800_56b_check.c
@@ -75,38 +75,41 @@ int rsa_check_crt_components(const RSA *rsa, BN_CTX *ctx)
* See SP800-5bBr1 6.4.1.2.1 Part 5 (c) & (g) - used for both p and q.
*
* (√2)(2^(nbits/2 - 1) = (√2/2)(2^(nbits/2))
- * √2/2 = 0.707106781186547524400 = 0.B504F333F9DE6484597D8
- * 0.B504F334 gives an approximation to 11 decimal places.
- * The range is then from
- * 0xB504F334_0000.......................000 to
- * 0xFFFFFFFF_FFFF.......................FFF
*/
int rsa_check_prime_factor_range(const BIGNUM *p, int nbits, BN_CTX *ctx)
{
int ret = 0;
- BIGNUM *tmp, *low;
+ BIGNUM *low;
+ int shift;
nbits >>= 1;
+ shift = nbits - BN_num_bits(&bn_inv_sqrt_2);
/* Upper bound check */
if (BN_num_bits(p) != nbits)
return 0;
BN_CTX_start(ctx);
- tmp = BN_CTX_get(ctx);
low = BN_CTX_get(ctx);
+ if (low == NULL)
+ goto err;
/* set low = (√2)(2^(nbits/2 - 1) */
- if (low == NULL || !BN_set_word(tmp, 0xB504F334))
+ if (!BN_copy(low, &bn_inv_sqrt_2))
goto err;
- if (nbits >= 32) {
- if (!BN_lshift(low, tmp, nbits - 32))
+ if (shift >= 0) {
+ /*
+ * We don't have all the bits. bn_inv_sqrt_2 contains a rounded up
+ * value, so there is a very low probabilty that we'll reject a valid
+ * value.
+ */
+ if (!BN_lshift(low, low, shift))
goto err;
- } else if (!BN_rshift(low, tmp, 32 - nbits)) {
+ } else if (!BN_rshift(low, low, -shift)) {
goto err;
}
- if (BN_cmp(p, low) < 0)
+ if (BN_cmp(p, low) <= 0)
goto err;
ret = 1;
err:
diff --git a/include/crypto/bn.h b/include/crypto/bn.h
index 91c6cd5dcc..f2cb30de0a 100644
--- a/include/crypto/bn.h
+++ b/include/crypto/bn.h
@@ -111,4 +111,7 @@ int bn_rsa_fips186_4_derive_prime(BIGNUM *Y, BIGNUM *X, const BIGNUM *Xin,
const BIGNUM *e, BN_CTX *ctx, BN_GENCB *cb);
OPENSSL_CTX *bn_get_lib_ctx(BN_CTX *ctx);
+
+extern const BIGNUM bn_inv_sqrt_2;
+
#endif
diff --git a/test/rsa_sp800_56b_test.c b/test/rsa_sp800_56b_test.c
index 1e6ea8d0b6..b928655794 100644
--- a/test/rsa_sp800_56b_test.c
+++ b/test/rsa_sp800_56b_test.c
@@ -223,6 +223,8 @@ static int test_check_prime_factor_range(void)
&& TEST_true(BN_set_word(p, 0x10))
&& TEST_false(rsa_check_prime_factor_range(p, 8, ctx))
&& TEST_true(BN_set_word(p, 0xB))
+ && TEST_false(rsa_check_prime_factor_range(p, 8, ctx))
+ && TEST_true(BN_set_word(p, 0xC))
&& TEST_true(rsa_check_prime_factor_range(p, 8, ctx))
&& TEST_true(BN_set_word(p, 0xF))
&& TEST_true(rsa_check_prime_factor_range(p, 8, ctx))
generated by cgit v1.2.3 (git 2.25.1) at 2024-07-30 15:10:58 +0000