1 files changed, 92 insertions, 0 deletions
diff --git a/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_gcd.c b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_gcd.c
new file mode 100644
index 00000000000..53029baf304
--- /dev/null
+++ b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_gcd.c
@@ -0,0 +1,92 @@
+#include "tommath_private.h"
+#ifdef BN_MP_GCD_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* Greatest Common Divisor using the binary method */
+mp_err mp_gcd(const mp_int *a, const mp_int *b, mp_int *c)
+{
+   mp_int  u, v;
+   int     k, u_lsb, v_lsb;
+   mp_err err;
+
+   /* either zero than gcd is the largest */
+   if (MP_IS_ZERO(a)) {
+      return mp_abs(b, c);
+   }
+   if (MP_IS_ZERO(b)) {
+      return mp_abs(a, c);
+   }
+
+   /* get copies of a and b we can modify */
+   if ((err = mp_init_copy(&u, a)) != MP_OKAY) {
+      return err;
+   }
+
+   if ((err = mp_init_copy(&v, b)) != MP_OKAY) {
+      goto LBL_U;
+   }
+
+   /* must be positive for the remainder of the algorithm */
+   u.sign = v.sign = MP_ZPOS;
+
+   /* B1.  Find the common power of two for u and v */
+   u_lsb = mp_cnt_lsb(&u);
+   v_lsb = mp_cnt_lsb(&v);
+   k     = MP_MIN(u_lsb, v_lsb);
+
+   if (k > 0) {
+      /* divide the power of two out */
+      if ((err = mp_div_2d(&u, k, &u, NULL)) != MP_OKAY) {
+         goto LBL_V;
+      }
+
+      if ((err = mp_div_2d(&v, k, &v, NULL)) != MP_OKAY) {
+         goto LBL_V;
+      }
+   }
+
+   /* divide any remaining factors of two out */
+   if (u_lsb != k) {
+      if ((err = mp_div_2d(&u, u_lsb - k, &u, NULL)) != MP_OKAY) {
+         goto LBL_V;
+      }
+   }
+
+   if (v_lsb != k) {
+      if ((err = mp_div_2d(&v, v_lsb - k, &v, NULL)) != MP_OKAY) {
+         goto LBL_V;
+      }
+   }
+
+   while (!MP_IS_ZERO(&v)) {
+      /* make sure v is the largest */
+      if (mp_cmp_mag(&u, &v) == MP_GT) {
+         /* swap u and v to make sure v is >= u */
+         mp_exch(&u, &v);
+      }
+
+      /* subtract smallest from largest */
+      if ((err = s_mp_sub(&v, &u, &v)) != MP_OKAY) {
+         goto LBL_V;
+      }
+
+      /* Divide out all factors of two */
+      if ((err = mp_div_2d(&v, mp_cnt_lsb(&v), &v, NULL)) != MP_OKAY) {
+         goto LBL_V;
+      }
+   }
+
+   /* multiply by 2**k which we divided out at the beginning */
+   if ((err = mp_mul_2d(&u, k, c)) != MP_OKAY) {
+      goto LBL_V;
+   }
+   c->sign = MP_ZPOS;
+   err = MP_OKAY;
+LBL_V:
+   mp_clear(&u);
+LBL_U:
+   mp_clear(&v);
+   return err;
+}
+#endif