Squashed 'src/secp256k1/' changes from 8746600ee..44c2452fd

44c2452fd Merge bitcoin-core/secp256k1#1105: Don't export symbols in static libraries
6f6cab998 abi: Don't export symbols in static Windows libraries
485f608fa Merge bitcoin-core/secp256k1#1104: Fix the false positive of `SECP_64BIT_ASM_CHECK`
8b013fce5 Merge bitcoin-core/secp256k1#1056: Save negations in var-time group addition
7efc9835a Fix the false positive of `SECP_64BIT_ASM_CHECK`
2f984ffc4 Save negations in var-time group addition

git-subtree-dir: src/secp256k1
git-subtree-split: 44c2452fd387f7ca604ab42d73746e7d3a44d8a2

5 files changed, 111 insertions, 83 deletions

diff --git a/build-aux/m4/bitcoin_secp.m4 b/build-aux/m4/bitcoin_secp.m4
index dda770e001..9cb54de098 100644
--- a/build-aux/m4/bitcoin_secp.m4
+++ b/build-aux/m4/bitcoin_secp.m4
@@ -1,7 +1,7 @@
 dnl escape "$0x" below using the m4 quadrigaph @S|@, and escape it again with a \ for the shell.
 AC_DEFUN([SECP_64BIT_ASM_CHECK],[
 AC_MSG_CHECKING(for x86_64 assembly availability)
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+AC_LINK_IFELSE([AC_LANG_PROGRAM([[
   #include <stdint.h>]],[[
   uint64_t a = 11, tmp;
   __asm__ __volatile__("movq \@S|@0x100000000,%1; mulq %%rsi" : "+a"(a) : "S"(tmp) : "cc", "%rdx");
diff --git a/include/secp256k1.h b/include/secp256k1.h
index 86ab7e556d..dddab346ae 100644
--- a/include/secp256k1.h
+++ b/include/secp256k1.h
@@ -141,9 +141,13 @@ typedef int (*secp256k1_nonce_function)(
 # define SECP256K1_NO_BUILD
 #endif
 
+/** At secp256k1 build-time DLL_EXPORT is defined when building objects destined
+ *  for a shared library, but not for those intended for static libraries.
+ */
+
 #ifndef SECP256K1_API
 # if defined(_WIN32)
-#  ifdef SECP256K1_BUILD
+#  if defined(SECP256K1_BUILD) && defined(DLL_EXPORT)
 #   define SECP256K1_API __declspec(dllexport)
 #  else
 #   define SECP256K1_API
diff --git a/sage/prove_group_implementations.sage b/sage/prove_group_implementations.sage
index 96ce33506a..652bd87f11 100644
--- a/sage/prove_group_implementations.sage
+++ b/sage/prove_group_implementations.sage
@@ -40,29 +40,26 @@ def formula_secp256k1_gej_add_var(branch, a, b):
   s2 = s2 * a.Z
   h = -u1
   h = h + u2
-  i = -s1
-  i = i + s2
+  i = -s2
+  i = i + s1
   if branch == 2:
     r = formula_secp256k1_gej_double_var(a)
     return (constraints(), constraints(zero={h : 'h=0', i : 'i=0', a.Infinity : 'a_finite', b.Infinity : 'b_finite'}), r)
   if branch == 3:
     return (constraints(), constraints(zero={h : 'h=0', a.Infinity : 'a_finite', b.Infinity : 'b_finite'}, nonzero={i : 'i!=0'}), point_at_infinity())
-  i2 = i^2
+  t = h * b.Z
+  rz = a.Z * t
   h2 = h^2
+  h2 = -h2
   h3 = h2 * h
-  h = h * b.Z
-  rz = a.Z * h
   t = u1 * h2
-  rx = t
-  rx = rx * 2
+  rx = i^2
   rx = rx + h3
-  rx = -rx
-  rx = rx + i2
-  ry = -rx
-  ry = ry + t
-  ry = ry * i
+  rx = rx + t
+  rx = rx + t
+  t = t + rx
+  ry = t * i
   h3 = h3 * s1
-  h3 = -h3
   ry = ry + h3
   return (constraints(), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite'}, nonzero={h : 'h!=0'}), jacobianpoint(rx, ry, rz))
 
@@ -80,28 +77,25 @@ def formula_secp256k1_gej_add_ge_var(branch, a, b):
   s2 = s2 * a.Z
   h = -u1
   h = h + u2
-  i = -s1
-  i = i + s2
+  i = -s2
+  i = i + s1
   if (branch == 2):
     r = formula_secp256k1_gej_double_var(a)
     return (constraints(zero={b.Z - 1 : 'b.z=1'}), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite', h : 'h=0', i : 'i=0'}), r)
   if (branch == 3):
     return (constraints(zero={b.Z - 1 : 'b.z=1'}), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite', h : 'h=0'}, nonzero={i : 'i!=0'}), point_at_infinity())
-  i2 = i^2
-  h2 = h^2
-  h3 = h * h2
   rz = a.Z * h
+  h2 = h^2
+  h2 = -h2
+  h3 = h2 * h
   t = u1 * h2
-  rx = t
-  rx = rx * 2
+  rx = i^2
   rx = rx + h3
-  rx = -rx
-  rx = rx + i2
-  ry = -rx
-  ry = ry + t
-  ry = ry * i
+  rx = rx + t
+  rx = rx + t
+  t = t + rx
+  ry = t * i
   h3 = h3 * s1
-  h3 = -h3
   ry = ry + h3
   return (constraints(zero={b.Z - 1 : 'b.z=1'}), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite'}, nonzero={h : 'h!=0'}), jacobianpoint(rx, ry, rz))
 
@@ -109,14 +103,15 @@ def formula_secp256k1_gej_add_zinv_var(branch, a, b):
   """libsecp256k1's secp256k1_gej_add_zinv_var"""
   bzinv = b.Z^(-1)
   if branch == 0:
-    return (constraints(), constraints(nonzero={b.Infinity : 'b_infinite'}), a)
-  if branch == 1:
+    rinf = b.Infinity
     bzinv2 = bzinv^2
     bzinv3 = bzinv2 * bzinv
     rx = b.X * bzinv2
     ry = b.Y * bzinv3
     rz = 1
-    return (constraints(), constraints(zero={b.Infinity : 'b_finite'}, nonzero={a.Infinity : 'a_infinite'}), jacobianpoint(rx, ry, rz))
+    return (constraints(), constraints(nonzero={a.Infinity : 'a_infinite'}), jacobianpoint(rx, ry, rz, rinf))
+  if branch == 1:
+    return (constraints(), constraints(zero={a.Infinity : 'a_finite'}, nonzero={b.Infinity : 'b_infinite'}), a)
   azz = a.Z * bzinv
   z12 = azz^2
   u1 = a.X
@@ -126,29 +121,25 @@ def formula_secp256k1_gej_add_zinv_var(branch, a, b):
   s2 = s2 * azz
   h = -u1
   h = h + u2
-  i = -s1
-  i = i + s2
+  i = -s2
+  i = i + s1
   if branch == 2:
     r = formula_secp256k1_gej_double_var(a)
     return (constraints(), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite', h : 'h=0', i : 'i=0'}), r)
   if branch == 3:
     return (constraints(), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite', h : 'h=0'}, nonzero={i : 'i!=0'}), point_at_infinity())
-  i2 = i^2
+  rz = a.Z * h
   h2 = h^2
-  h3 = h * h2
-  rz = a.Z
-  rz = rz * h
+  h2 = -h2
+  h3 = h2 * h
   t = u1 * h2
-  rx = t
-  rx = rx * 2
+  rx = i^2
   rx = rx + h3
-  rx = -rx
-  rx = rx + i2
-  ry = -rx
-  ry = ry + t
-  ry = ry * i
+  rx = rx + t
+  rx = rx + t
+  t = t + rx
+  ry = t * i
   h3 = h3 * s1
-  h3 = -h3
   ry = ry + h3
   return (constraints(), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite'}, nonzero={h : 'h!=0'}), jacobianpoint(rx, ry, rz))
 
diff --git a/src/bench_internal.c b/src/bench_internal.c
index 3c145f306c..7eb3af28d7 100644
--- a/src/bench_internal.c
+++ b/src/bench_internal.c
@@ -254,6 +254,15 @@ void bench_group_add_affine_var(void* arg, int iters) {
     }
 }
 
+void bench_group_add_zinv_var(void* arg, int iters) {
+    int i;
+    bench_inv *data = (bench_inv*)arg;
+
+    for (i = 0; i < iters; i++) {
+        secp256k1_gej_add_zinv_var(&data->gej[0], &data->gej[0], &data->ge[1], &data->gej[0].y);
+    }
+}
+
 void bench_group_to_affine_var(void* arg, int iters) {
     int i;
     bench_inv *data = (bench_inv*)arg;
@@ -376,6 +385,7 @@ int main(int argc, char **argv) {
     if (d || have_flag(argc, argv, "group") || have_flag(argc, argv, "add")) run_benchmark("group_add_var", bench_group_add_var, bench_setup, NULL, &data, 10, iters*10);
     if (d || have_flag(argc, argv, "group") || have_flag(argc, argv, "add")) run_benchmark("group_add_affine", bench_group_add_affine, bench_setup, NULL, &data, 10, iters*10);
     if (d || have_flag(argc, argv, "group") || have_flag(argc, argv, "add")) run_benchmark("group_add_affine_var", bench_group_add_affine_var, bench_setup, NULL, &data, 10, iters*10);
+    if (d || have_flag(argc, argv, "group") || have_flag(argc, argv, "add")) run_benchmark("group_add_zinv_var", bench_group_add_zinv_var, bench_setup, NULL, &data, 10, iters*10);
     if (d || have_flag(argc, argv, "group") || have_flag(argc, argv, "to_affine")) run_benchmark("group_to_affine_var", bench_group_to_affine_var, bench_setup, NULL, &data, 10, iters);
 
     if (d || have_flag(argc, argv, "ecmult") || have_flag(argc, argv, "wnaf")) run_benchmark("wnaf_const", bench_wnaf_const, bench_setup, NULL, &data, 10, iters);
diff --git a/src/group_impl.h b/src/group_impl.h
index b19b02a01f..63735ab682 100644
--- a/src/group_impl.h
+++ b/src/group_impl.h
@@ -330,15 +330,14 @@ static void secp256k1_gej_double_var(secp256k1_gej *r, const secp256k1_gej *a, s
 }
 
 static void secp256k1_gej_add_var(secp256k1_gej *r, const secp256k1_gej *a, const secp256k1_gej *b, secp256k1_fe *rzr) {
-    /* Operations: 12 mul, 4 sqr, 2 normalize, 12 mul_int/add/negate */
-    secp256k1_fe z22, z12, u1, u2, s1, s2, h, i, i2, h2, h3, t;
+    /* 12 mul, 4 sqr, 11 add/negate/normalizes_to_zero (ignoring special cases) */
+    secp256k1_fe z22, z12, u1, u2, s1, s2, h, i, h2, h3, t;
 
     if (a->infinity) {
         VERIFY_CHECK(rzr == NULL);
         *r = *b;
         return;
     }
-
     if (b->infinity) {
         if (rzr != NULL) {
             secp256k1_fe_set_int(rzr, 1);
@@ -347,7 +346,6 @@ static void secp256k1_gej_add_var(secp256k1_gej *r, const secp256k1_gej *a, cons
         return;
     }
 
-    r->infinity = 0;
     secp256k1_fe_sqr(&z22, &b->z);
     secp256k1_fe_sqr(&z12, &a->z);
     secp256k1_fe_mul(&u1, &a->x, &z22);
@@ -355,7 +353,7 @@ static void secp256k1_gej_add_var(secp256k1_gej *r, const secp256k1_gej *a, cons
     secp256k1_fe_mul(&s1, &a->y, &z22); secp256k1_fe_mul(&s1, &s1, &b->z);
     secp256k1_fe_mul(&s2, &b->y, &z12); secp256k1_fe_mul(&s2, &s2, &a->z);
     secp256k1_fe_negate(&h, &u1, 1); secp256k1_fe_add(&h, &u2);
-    secp256k1_fe_negate(&i, &s1, 1); secp256k1_fe_add(&i, &s2);
+    secp256k1_fe_negate(&i, &s2, 1); secp256k1_fe_add(&i, &s1);
     if (secp256k1_fe_normalizes_to_zero_var(&h)) {
         if (secp256k1_fe_normalizes_to_zero_var(&i)) {
             secp256k1_gej_double_var(r, a, rzr);
@@ -367,24 +365,33 @@ static void secp256k1_gej_add_var(secp256k1_gej *r, const secp256k1_gej *a, cons
         }
         return;
     }
-    secp256k1_fe_sqr(&i2, &i);
-    secp256k1_fe_sqr(&h2, &h);
-    secp256k1_fe_mul(&h3, &h, &h2);
-    secp256k1_fe_mul(&h, &h, &b->z);
+
+    r->infinity = 0;
+    secp256k1_fe_mul(&t, &h, &b->z);
     if (rzr != NULL) {
-        *rzr = h;
+        *rzr = t;
     }
-    secp256k1_fe_mul(&r->z, &a->z, &h);
+    secp256k1_fe_mul(&r->z, &a->z, &t);
+
+    secp256k1_fe_sqr(&h2, &h);
+    secp256k1_fe_negate(&h2, &h2, 1);
+    secp256k1_fe_mul(&h3, &h2, &h);
     secp256k1_fe_mul(&t, &u1, &h2);
-    r->x = t; secp256k1_fe_mul_int(&r->x, 2); secp256k1_fe_add(&r->x, &h3); secp256k1_fe_negate(&r->x, &r->x, 3); secp256k1_fe_add(&r->x, &i2);
-    secp256k1_fe_negate(&r->y, &r->x, 5); secp256k1_fe_add(&r->y, &t); secp256k1_fe_mul(&r->y, &r->y, &i);
-    secp256k1_fe_mul(&h3, &h3, &s1); secp256k1_fe_negate(&h3, &h3, 1);
+
+    secp256k1_fe_sqr(&r->x, &i);
+    secp256k1_fe_add(&r->x, &h3);
+    secp256k1_fe_add(&r->x, &t);
+    secp256k1_fe_add(&r->x, &t);
+
+    secp256k1_fe_add(&t, &r->x);
+    secp256k1_fe_mul(&r->y, &t, &i);
+    secp256k1_fe_mul(&h3, &h3, &s1);
     secp256k1_fe_add(&r->y, &h3);
 }
 
 static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, const secp256k1_ge *b, secp256k1_fe *rzr) {
-    /* 8 mul, 3 sqr, 4 normalize, 12 mul_int/add/negate */
-    secp256k1_fe z12, u1, u2, s1, s2, h, i, i2, h2, h3, t;
+    /* 8 mul, 3 sqr, 13 add/negate/normalize_weak/normalizes_to_zero (ignoring special cases) */
+    secp256k1_fe z12, u1, u2, s1, s2, h, i, h2, h3, t;
     if (a->infinity) {
         VERIFY_CHECK(rzr == NULL);
         secp256k1_gej_set_ge(r, b);
@@ -397,7 +404,6 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, c
         *r = *a;
         return;
     }
-    r->infinity = 0;
 
     secp256k1_fe_sqr(&z12, &a->z);
     u1 = a->x; secp256k1_fe_normalize_weak(&u1);
@@ -405,7 +411,7 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, c
     s1 = a->y; secp256k1_fe_normalize_weak(&s1);
     secp256k1_fe_mul(&s2, &b->y, &z12); secp256k1_fe_mul(&s2, &s2, &a->z);
     secp256k1_fe_negate(&h, &u1, 1); secp256k1_fe_add(&h, &u2);
-    secp256k1_fe_negate(&i, &s1, 1); secp256k1_fe_add(&i, &s2);
+    secp256k1_fe_negate(&i, &s2, 1); secp256k1_fe_add(&i, &s1);
     if (secp256k1_fe_normalizes_to_zero_var(&h)) {
         if (secp256k1_fe_normalizes_to_zero_var(&i)) {
             secp256k1_gej_double_var(r, a, rzr);
@@ -417,28 +423,33 @@ static void secp256k1_gej_add_ge_var(secp256k1_gej *r, const secp256k1_gej *a, c
         }
         return;
     }
-    secp256k1_fe_sqr(&i2, &i);
-    secp256k1_fe_sqr(&h2, &h);
-    secp256k1_fe_mul(&h3, &h, &h2);
+
+    r->infinity = 0;
     if (rzr != NULL) {
         *rzr = h;
     }
     secp256k1_fe_mul(&r->z, &a->z, &h);
+
+    secp256k1_fe_sqr(&h2, &h);
+    secp256k1_fe_negate(&h2, &h2, 1);
+    secp256k1_fe_mul(&h3, &h2, &h);
     secp256k1_fe_mul(&t, &u1, &h2);
-    r->x = t; secp256k1_fe_mul_int(&r->x, 2); secp256k1_fe_add(&r->x, &h3); secp256k1_fe_negate(&r->x, &r->x, 3); secp256k1_fe_add(&r->x, &i2);
-    secp256k1_fe_negate(&r->y, &r->x, 5); secp256k1_fe_add(&r->y, &t); secp256k1_fe_mul(&r->y, &r->y, &i);
-    secp256k1_fe_mul(&h3, &h3, &s1); secp256k1_fe_negate(&h3, &h3, 1);
+
+    secp256k1_fe_sqr(&r->x, &i);
+    secp256k1_fe_add(&r->x, &h3);
+    secp256k1_fe_add(&r->x, &t);
+    secp256k1_fe_add(&r->x, &t);
+
+    secp256k1_fe_add(&t, &r->x);
+    secp256k1_fe_mul(&r->y, &t, &i);
+    secp256k1_fe_mul(&h3, &h3, &s1);
     secp256k1_fe_add(&r->y, &h3);
 }
 
 static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a, const secp256k1_ge *b, const secp256k1_fe *bzinv) {
-    /* 9 mul, 3 sqr, 4 normalize, 12 mul_int/add/negate */
-    secp256k1_fe az, z12, u1, u2, s1, s2, h, i, i2, h2, h3, t;
+    /* 9 mul, 3 sqr, 13 add/negate/normalize_weak/normalizes_to_zero (ignoring special cases) */
+    secp256k1_fe az, z12, u1, u2, s1, s2, h, i, h2, h3, t;
 
-    if (b->infinity) {
-        *r = *a;
-        return;
-    }
     if (a->infinity) {
         secp256k1_fe bzinv2, bzinv3;
         r->infinity = b->infinity;
@@ -449,7 +460,10 @@ static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a,
         secp256k1_fe_set_int(&r->z, 1);
         return;
     }
-    r->infinity = 0;
+    if (b->infinity) {
+        *r = *a;
+        return;
+    }
 
     /** We need to calculate (rx,ry,rz) = (ax,ay,az) + (bx,by,1/bzinv). Due to
      *  secp256k1's isomorphism we can multiply the Z coordinates on both sides
@@ -467,7 +481,7 @@ static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a,
     s1 = a->y; secp256k1_fe_normalize_weak(&s1);
     secp256k1_fe_mul(&s2, &b->y, &z12); secp256k1_fe_mul(&s2, &s2, &az);
     secp256k1_fe_negate(&h, &u1, 1); secp256k1_fe_add(&h, &u2);
-    secp256k1_fe_negate(&i, &s1, 1); secp256k1_fe_add(&i, &s2);
+    secp256k1_fe_negate(&i, &s2, 1); secp256k1_fe_add(&i, &s1);
     if (secp256k1_fe_normalizes_to_zero_var(&h)) {
         if (secp256k1_fe_normalizes_to_zero_var(&i)) {
             secp256k1_gej_double_var(r, a, NULL);
@@ -476,14 +490,23 @@ static void secp256k1_gej_add_zinv_var(secp256k1_gej *r, const secp256k1_gej *a,
         }
         return;
     }
-    secp256k1_fe_sqr(&i2, &i);
+
+    r->infinity = 0;
+    secp256k1_fe_mul(&r->z, &a->z, &h);
+
     secp256k1_fe_sqr(&h2, &h);
-    secp256k1_fe_mul(&h3, &h, &h2);
-    r->z = a->z; secp256k1_fe_mul(&r->z, &r->z, &h);
+    secp256k1_fe_negate(&h2, &h2, 1);
+    secp256k1_fe_mul(&h3, &h2, &h);
     secp256k1_fe_mul(&t, &u1, &h2);
-    r->x = t; secp256k1_fe_mul_int(&r->x, 2); secp256k1_fe_add(&r->x, &h3); secp256k1_fe_negate(&r->x, &r->x, 3); secp256k1_fe_add(&r->x, &i2);
-    secp256k1_fe_negate(&r->y, &r->x, 5); secp256k1_fe_add(&r->y, &t); secp256k1_fe_mul(&r->y, &r->y, &i);
-    secp256k1_fe_mul(&h3, &h3, &s1); secp256k1_fe_negate(&h3, &h3, 1);
+
+    secp256k1_fe_sqr(&r->x, &i);
+    secp256k1_fe_add(&r->x, &h3);
+    secp256k1_fe_add(&r->x, &t);
+    secp256k1_fe_add(&r->x, &t);
+
+    secp256k1_fe_add(&t, &r->x);
+    secp256k1_fe_mul(&r->y, &t, &i);
+    secp256k1_fe_mul(&h3, &h3, &s1);
     secp256k1_fe_add(&r->y, &h3);
 }