1 files changed, 137 insertions, 0 deletions
diff --git a/security/nss/lib/freebl/ecl/ecp_521.c b/security/nss/lib/freebl/ecl/ecp_521.c
new file mode 100644
index 0000000000..6ca0dbb11f
--- /dev/null
+++ b/security/nss/lib/freebl/ecl/ecp_521.c
@@ -0,0 +1,137 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ecp.h"
+#include "mpi.h"
+#include "mplogic.h"
+#include "mpi-priv.h"
+
+#define ECP521_DIGITS ECL_CURVE_DIGITS(521)
+
+/* Fast modular reduction for p521 = 2^521 - 1.  a can be r. Uses
+ * algorithm 2.31 from Hankerson, Menezes, Vanstone. Guide to
+ * Elliptic Curve Cryptography. */
+static mp_err
+ec_GFp_nistp521_mod(const mp_int *a, mp_int *r, const GFMethod *meth)
+{
+    mp_err res = MP_OKAY;
+    int a_bits = mpl_significant_bits(a);
+    unsigned int i;
+
+    /* m1, m2 are statically-allocated mp_int of exactly the size we need */
+    mp_int m1;
+
+    mp_digit s1[ECP521_DIGITS] = { 0 };
+
+    MP_SIGN(&m1) = MP_ZPOS;
+    MP_ALLOC(&m1) = ECP521_DIGITS;
+    MP_USED(&m1) = ECP521_DIGITS;
+    MP_DIGITS(&m1) = s1;
+
+    if (a_bits < 521) {
+        if (a == r)
+            return MP_OKAY;
+        return mp_copy(a, r);
+    }
+    /* for polynomials larger than twice the field size or polynomials
+     * not using all words, use regular reduction */
+    if (a_bits > (521 * 2)) {
+        MP_CHECKOK(mp_mod(a, &meth->irr, r));
+    } else {
+#define FIRST_DIGIT (ECP521_DIGITS - 1)
+        for (i = FIRST_DIGIT; i < MP_USED(a) - 1; i++) {
+            s1[i - FIRST_DIGIT] = (MP_DIGIT(a, i) >> 9) | (MP_DIGIT(a, 1 + i) << (MP_DIGIT_BIT - 9));
+        }
+        s1[i - FIRST_DIGIT] = MP_DIGIT(a, i) >> 9;
+
+        if (a != r) {
+            MP_CHECKOK(s_mp_pad(r, ECP521_DIGITS));
+            for (i = 0; i < ECP521_DIGITS; i++) {
+                MP_DIGIT(r, i) = MP_DIGIT(a, i);
+            }
+        }
+        MP_USED(r) = ECP521_DIGITS;
+        MP_DIGIT(r, FIRST_DIGIT) &= 0x1FF;
+
+        MP_CHECKOK(s_mp_add(r, &m1));
+        if (MP_DIGIT(r, FIRST_DIGIT) & 0x200) {
+            MP_CHECKOK(s_mp_add_d(r, 1));
+            MP_DIGIT(r, FIRST_DIGIT) &= 0x1FF;
+        } else if (s_mp_cmp(r, &meth->irr) == 0) {
+            mp_zero(r);
+        }
+        s_mp_clamp(r);
+    }
+
+CLEANUP:
+    return res;
+}
+
+/* Compute the square of polynomial a, reduce modulo p521. Store the
+ * result in r.  r could be a.  Uses optimized modular reduction for p521.
+ */
+static mp_err
+ec_GFp_nistp521_sqr(const mp_int *a, mp_int *r, const GFMethod *meth)
+{
+    mp_err res = MP_OKAY;
+
+    MP_CHECKOK(mp_sqr(a, r));
+    MP_CHECKOK(ec_GFp_nistp521_mod(r, r, meth));
+CLEANUP:
+    return res;
+}
+
+/* Compute the product of two polynomials a and b, reduce modulo p521.
+ * Store the result in r.  r could be a or b; a could be b.  Uses
+ * optimized modular reduction for p521. */
+static mp_err
+ec_GFp_nistp521_mul(const mp_int *a, const mp_int *b, mp_int *r,
+                    const GFMethod *meth)
+{
+    mp_err res = MP_OKAY;
+
+    MP_CHECKOK(mp_mul(a, b, r));
+    MP_CHECKOK(ec_GFp_nistp521_mod(r, r, meth));
+CLEANUP:
+    return res;
+}
+
+/* Divides two field elements. If a is NULL, then returns the inverse of
+ * b. */
+static mp_err
+ec_GFp_nistp521_div(const mp_int *a, const mp_int *b, mp_int *r,
+                    const GFMethod *meth)
+{
+    mp_err res = MP_OKAY;
+    mp_int t;
+
+    /* If a is NULL, then return the inverse of b, otherwise return a/b. */
+    if (a == NULL) {
+        return mp_invmod(b, &meth->irr, r);
+    } else {
+        /* MPI doesn't support divmod, so we implement it using invmod and
+         * mulmod. */
+        MP_CHECKOK(mp_init(&t));
+        MP_CHECKOK(mp_invmod(b, &meth->irr, &t));
+        MP_CHECKOK(mp_mul(a, &t, r));
+        MP_CHECKOK(ec_GFp_nistp521_mod(r, r, meth));
+    CLEANUP:
+        mp_clear(&t);
+        return res;
+    }
+}
+
+/* Wire in fast field arithmetic and precomputation of base point for
+ * named curves. */
+mp_err
+ec_group_set_gfp521(ECGroup *group, ECCurveName name)
+{
+    if (name == ECCurve_NIST_P521) {
+        group->meth->field_mod = &ec_GFp_nistp521_mod;
+        group->meth->field_mul = &ec_GFp_nistp521_mul;
+        group->meth->field_sqr = &ec_GFp_nistp521_sqr;
+        group->meth->field_div = &ec_GFp_nistp521_div;
+    }
+    return MP_OKAY;
+}