-/* $OpenBSD: bn_add.c,v 1.22 2023/02/13 04:25:37 jsing Exp $ */
+/* $OpenBSD: bn_add.c,v 1.23 2023/02/16 04:42:20 jsing Exp $ */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
* All rights reserved.
*
#include "bn_arch.h"
#include "bn_local.h"
+#include "bn_internal.h"
BN_ULONG bn_add(BIGNUM *r, int rn, const BIGNUM *a, const BIGNUM *b);
BN_ULONG bn_sub(BIGNUM *r, int rn, const BIGNUM *a, const BIGNUM *b);
+/*
+ * bn_add_words() computes (carry:r[i]) = a[i] + b[i] + carry, where a and b
+ * are both arrays of words. Any carry resulting from the addition is returned.
+ */
#ifndef HAVE_BN_ADD_WORDS
-#ifdef BN_LLONG
BN_ULONG
bn_add_words(BN_ULONG *r, const BN_ULONG *a, const BN_ULONG *b, int n)
{
- BN_ULLONG ll = 0;
+ BN_ULONG carry = 0;
assert(n >= 0);
if (n <= 0)
- return ((BN_ULONG)0);
-
-#ifndef OPENSSL_SMALL_FOOTPRINT
- while (n & ~3) {
- ll += (BN_ULLONG)a[0] + b[0];
- r[0] = (BN_ULONG)ll & BN_MASK2;
- ll >>= BN_BITS2;
- ll += (BN_ULLONG)a[1] + b[1];
- r[1] = (BN_ULONG)ll & BN_MASK2;
- ll >>= BN_BITS2;
- ll += (BN_ULLONG)a[2] + b[2];
- r[2] = (BN_ULONG)ll & BN_MASK2;
- ll >>= BN_BITS2;
- ll += (BN_ULLONG)a[3] + b[3];
- r[3] = (BN_ULONG)ll & BN_MASK2;
- ll >>= BN_BITS2;
- a += 4;
- b += 4;
- r += 4;
- n -= 4;
- }
-#endif
- while (n) {
- ll += (BN_ULLONG)a[0] + b[0];
- r[0] = (BN_ULONG)ll & BN_MASK2;
- ll >>= BN_BITS2;
- a++;
- b++;
- r++;
- n--;
- }
- return ((BN_ULONG)ll);
-}
-#else /* !BN_LLONG */
-BN_ULONG
-bn_add_words(BN_ULONG *r, const BN_ULONG *a, const BN_ULONG *b, int n)
-{
- BN_ULONG c, l, t;
-
- assert(n >= 0);
- if (n <= 0)
- return ((BN_ULONG)0);
+ return 0;
- c = 0;
#ifndef OPENSSL_SMALL_FOOTPRINT
while (n & ~3) {
- t = a[0];
- t = (t + c) & BN_MASK2;
- c = (t < c);
- l = (t + b[0]) & BN_MASK2;
- c += (l < t);
- r[0] = l;
- t = a[1];
- t = (t + c) & BN_MASK2;
- c = (t < c);
- l = (t + b[1]) & BN_MASK2;
- c += (l < t);
- r[1] = l;
- t = a[2];
- t = (t + c) & BN_MASK2;
- c = (t < c);
- l = (t + b[2]) & BN_MASK2;
- c += (l < t);
- r[2] = l;
- t = a[3];
- t = (t + c) & BN_MASK2;
- c = (t < c);
- l = (t + b[3]) & BN_MASK2;
- c += (l < t);
- r[3] = l;
+ bn_addw_addw(a[0], b[0], carry, &carry, &r[0]);
+ bn_addw_addw(a[1], b[1], carry, &carry, &r[1]);
+ bn_addw_addw(a[2], b[2], carry, &carry, &r[2]);
+ bn_addw_addw(a[3], b[3], carry, &carry, &r[3]);
a += 4;
b += 4;
r += 4;
}
#endif
while (n) {
- t = a[0];
- t = (t + c) & BN_MASK2;
- c = (t < c);
- l = (t + b[0]) & BN_MASK2;
- c += (l < t);
- r[0] = l;
+ bn_addw_addw(a[0], b[0], carry, &carry, &r[0]);
a++;
b++;
r++;
n--;
}
- return ((BN_ULONG)c);
+ return carry;
}
-#endif /* !BN_LLONG */
#endif
+/*
+ * bn_sub_words() computes (borrow:r[i]) = a[i] - b[i] - borrow, where a and b
+ * are both arrays of words. Any borrow resulting from the subtraction is
+ * returned.
+ */
#ifndef HAVE_BN_SUB_WORDS
BN_ULONG
bn_sub_words(BN_ULONG *r, const BN_ULONG *a, const BN_ULONG *b, int n)
{
- BN_ULONG t1, t2;
- int c = 0;
+ BN_ULONG borrow = 0;
assert(n >= 0);
if (n <= 0)
- return ((BN_ULONG)0);
+ return 0;
#ifndef OPENSSL_SMALL_FOOTPRINT
- while (n&~3) {
- t1 = a[0];
- t2 = b[0];
- r[0] = (t1 - t2 - c) & BN_MASK2;
- if (t1 != t2)
- c = (t1 < t2);
- t1 = a[1];
- t2 = b[1];
- r[1] = (t1 - t2 - c) & BN_MASK2;
- if (t1 != t2)
- c = (t1 < t2);
- t1 = a[2];
- t2 = b[2];
- r[2] = (t1 - t2 - c) & BN_MASK2;
- if (t1 != t2)
- c = (t1 < t2);
- t1 = a[3];
- t2 = b[3];
- r[3] = (t1 - t2 - c) & BN_MASK2;
- if (t1 != t2)
- c = (t1 < t2);
+ while (n & ~3) {
+ bn_subw_subw(a[0], b[0], borrow, &borrow, &r[0]);
+ bn_subw_subw(a[1], b[1], borrow, &borrow, &r[1]);
+ bn_subw_subw(a[2], b[2], borrow, &borrow, &r[2]);
+ bn_subw_subw(a[3], b[3], borrow, &borrow, &r[3]);
a += 4;
b += 4;
r += 4;
}
#endif
while (n) {
- t1 = a[0];
- t2 = b[0];
- r[0] = (t1 - t2 - c) & BN_MASK2;
- if (t1 != t2)
- c = (t1 < t2);
+ bn_subw_subw(a[0], b[0], borrow, &borrow, &r[0]);
a++;
b++;
r++;
n--;
}
- return (c);
+ return borrow;
}
#endif
-#ifndef HAVE_BN_ADD
/*
* bn_add() computes a + b, storing the result in r (which may be the same as a
* or b). The caller must ensure that r has been expanded to max(a->top, b->top)
* words. Any carry resulting from the addition is returned.
*/
+#ifndef HAVE_BN_ADD
BN_ULONG
bn_add(BIGNUM *r, int rn, const BIGNUM *a, const BIGNUM *b)
{
}
#endif
-#ifndef HAVE_BN_SUB
/*
* bn_sub() computes a - b, storing the result in r (which may be the same as a
* or b). The caller must ensure that the number of words in a is greater than
* or equal to the number of words in b and that r has been expanded to
* a->top words. Any borrow resulting from the subtraction is returned.
*/
+#ifndef HAVE_BN_SUB
BN_ULONG
bn_sub(BIGNUM *r, int rn, const BIGNUM *a, const BIGNUM *b)
{
-/* $OpenBSD: bn_internal.h,v 1.4 2023/02/15 04:46:49 tb Exp $ */
+/* $OpenBSD: bn_internal.h,v 1.5 2023/02/16 04:42:20 jsing Exp $ */
/*
* Copyright (c) 2023 Joel Sing <jsing@openbsd.org>
*
#endif
#endif
+/*
+ * bn_addw_addw() computes (r1:r0) = a + b + c, where all inputs are single
+ * words, producing a double word result.
+ */
+#ifndef HAVE_BN_ADDW_ADDW
+static inline void
+bn_addw_addw(BN_ULONG a, BN_ULONG b, BN_ULONG c, BN_ULONG *out_r1,
+ BN_ULONG *out_r0)
+{
+ BN_ULONG carry, r1, r0;
+
+ bn_addw(a, b, &r1, &r0);
+ bn_addw(r0, c, &carry, &r0);
+ r1 += carry;
+
+ *out_r1 = r1;
+ *out_r0 = r0;
+}
+#endif
+
+/*
+ * bn_subw() computes r0 = a - b, where both inputs are single words,
+ * producing a single word result and borrow.
+ */
+#ifndef HAVE_BN_SUBW
+static inline void
+bn_subw(BN_ULONG a, BN_ULONG b, BN_ULONG *out_borrow, BN_ULONG *out_r0)
+{
+ BN_ULONG borrow, r0;
+
+ r0 = a - b;
+ borrow = ((r0 | (b & ~a)) & (b | ~a)) >> (BN_BITS2 - 1);
+
+ *out_borrow = borrow;
+ *out_r0 = r0;
+}
+#endif
+
+/*
+ * bn_subw_subw() computes r0 = a - b - c, where all inputs are single words,
+ * producing a single word result and borrow.
+ */
+#ifndef HAVE_BN_SUBW_SUBW
+static inline void
+bn_subw_subw(BN_ULONG a, BN_ULONG b, BN_ULONG c, BN_ULONG *out_borrow,
+ BN_ULONG *out_r0)
+{
+ BN_ULONG b1, b2, r0;
+
+ bn_subw(a, b, &b1, &r0);
+ bn_subw(r0, c, &b2, &r0);
+
+ *out_borrow = b1 + b2;
+ *out_r0 = r0;
+}
+#endif
+
#ifndef HAVE_BN_UMUL_HILO
#ifdef BN_LLONG
static inline void
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