early-access version 1255

externals/libressl/crypto/bn/bn_lib.c

@@ -0,0 +1,940 @@
+/* $OpenBSD: bn_lib.c,v 1.47 2019/06/17 17:11:48 tb Exp $ */
+/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
+ * All rights reserved.
+ *
+ * This package is an SSL implementation written
+ * by Eric Young (eay@cryptsoft.com).
+ * The implementation was written so as to conform with Netscapes SSL.
+ *
+ * This library is free for commercial and non-commercial use as long as
+ * the following conditions are aheared to.  The following conditions
+ * apply to all code found in this distribution, be it the RC4, RSA,
+ * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
+ * included with this distribution is covered by the same copyright terms
+ * except that the holder is Tim Hudson (tjh@cryptsoft.com).
+ *
+ * Copyright remains Eric Young's, and as such any Copyright notices in
+ * the code are not to be removed.
+ * If this package is used in a product, Eric Young should be given attribution
+ * as the author of the parts of the library used.
+ * This can be in the form of a textual message at program startup or
+ * in documentation (online or textual) provided with the package.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *    "This product includes cryptographic software written by
+ *     Eric Young (eay@cryptsoft.com)"
+ *    The word 'cryptographic' can be left out if the rouines from the library
+ *    being used are not cryptographic related :-).
+ * 4. If you include any Windows specific code (or a derivative thereof) from
+ *    the apps directory (application code) you must include an acknowledgement:
+ *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * The licence and distribution terms for any publically available version or
+ * derivative of this code cannot be changed.  i.e. this code cannot simply be
+ * copied and put under another distribution licence
+ * [including the GNU Public Licence.]
+ */
+
+#ifndef BN_DEBUG
+# undef NDEBUG /* avoid conflicting definitions */
+# define NDEBUG
+#endif
+
+#include <assert.h>
+#include <limits.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <openssl/opensslconf.h>
+
+#include <openssl/err.h>
+
+#include "bn_lcl.h"
+
+/* This stuff appears to be completely unused, so is deprecated */
+#ifndef OPENSSL_NO_DEPRECATED
+/* For a 32 bit machine
+ * 2 -   4 ==  128
+ * 3 -   8 ==  256
+ * 4 -  16 ==  512
+ * 5 -  32 == 1024
+ * 6 -  64 == 2048
+ * 7 - 128 == 4096
+ * 8 - 256 == 8192
+ */
+static int bn_limit_bits = 0;
+static int bn_limit_num = 8;        /* (1<<bn_limit_bits) */
+static int bn_limit_bits_low = 0;
+static int bn_limit_num_low = 8;    /* (1<<bn_limit_bits_low) */
+static int bn_limit_bits_high = 0;
+static int bn_limit_num_high = 8;   /* (1<<bn_limit_bits_high) */
+static int bn_limit_bits_mont = 0;
+static int bn_limit_num_mont = 8;   /* (1<<bn_limit_bits_mont) */
+
+void
+BN_set_params(int mult, int high, int low, int mont)
+{
+	if (mult >= 0) {
+		if (mult > (int)(sizeof(int) * 8) - 1)
+			mult = sizeof(int) * 8 - 1;
+		bn_limit_bits = mult;
+		bn_limit_num = 1 << mult;
+	}
+	if (high >= 0) {
+		if (high > (int)(sizeof(int) * 8) - 1)
+			high = sizeof(int) * 8 - 1;
+		bn_limit_bits_high = high;
+		bn_limit_num_high = 1 << high;
+	}
+	if (low >= 0) {
+		if (low > (int)(sizeof(int) * 8) - 1)
+			low = sizeof(int) * 8 - 1;
+		bn_limit_bits_low = low;
+		bn_limit_num_low = 1 << low;
+	}
+	if (mont >= 0) {
+		if (mont > (int)(sizeof(int) * 8) - 1)
+			mont = sizeof(int) * 8 - 1;
+		bn_limit_bits_mont = mont;
+		bn_limit_num_mont = 1 << mont;
+	}
+}
+
+int
+BN_get_params(int which)
+{
+	if (which == 0)
+		return (bn_limit_bits);
+	else if (which == 1)
+		return (bn_limit_bits_high);
+	else if (which == 2)
+		return (bn_limit_bits_low);
+	else if (which == 3)
+		return (bn_limit_bits_mont);
+	else
+		return (0);
+}
+#endif
+
+const BIGNUM *
+BN_value_one(void)
+{
+	static const BN_ULONG data_one = 1L;
+	static const BIGNUM const_one = {
+		(BN_ULONG *)&data_one, 1, 1, 0, BN_FLG_STATIC_DATA
+	};
+
+	return (&const_one);
+}
+
+int
+BN_num_bits_word(BN_ULONG l)
+{
+	BN_ULONG x, mask;
+	int bits;
+	unsigned int shift;
+
+	/* Constant time calculation of floor(log2(l)) + 1. */
+	bits = (l != 0);
+	shift = BN_BITS4;	/* On _LP64 this is 32, otherwise 16. */
+	do {
+		x = l >> shift;
+		/* If x is 0, set mask to 0, otherwise set it to all 1s. */
+		mask = ((~x & (x - 1)) >> (BN_BITS2 - 1)) - 1;
+		bits += shift & mask;
+		/* If x is 0, leave l alone, otherwise set l = x. */
+		l ^= (x ^ l) & mask;
+	} while ((shift /= 2) != 0);
+
+	return bits;
+}
+
+int
+BN_num_bits(const BIGNUM *a)
+{
+	int i = a->top - 1;
+
+	bn_check_top(a);
+
+	if (BN_is_zero(a))
+		return 0;
+	return ((i * BN_BITS2) + BN_num_bits_word(a->d[i]));
+}
+
+void
+BN_clear_free(BIGNUM *a)
+{
+	int i;
+
+	if (a == NULL)
+		return;
+	bn_check_top(a);
+	if (a->d != NULL && !(BN_get_flags(a, BN_FLG_STATIC_DATA)))
+		freezero(a->d, a->dmax * sizeof(a->d[0]));
+	i = BN_get_flags(a, BN_FLG_MALLOCED);
+	explicit_bzero(a, sizeof(BIGNUM));
+	if (i)
+		free(a);
+}
+
+void
+BN_free(BIGNUM *a)
+{
+	BN_clear_free(a);
+}
+
+void
+BN_init(BIGNUM *a)
+{
+	memset(a, 0, sizeof(BIGNUM));
+	bn_check_top(a);
+}
+
+BIGNUM *
+BN_new(void)
+{
+	BIGNUM *ret;
+
+	if ((ret = malloc(sizeof(BIGNUM))) == NULL) {
+		BNerror(ERR_R_MALLOC_FAILURE);
+		return (NULL);
+	}
+	ret->flags = BN_FLG_MALLOCED;
+	ret->top = 0;
+	ret->neg = 0;
+	ret->dmax = 0;
+	ret->d = NULL;
+	bn_check_top(ret);
+	return (ret);
+}
+
+/* This is used both by bn_expand2() and bn_dup_expand() */
+/* The caller MUST check that words > b->dmax before calling this */
+static BN_ULONG *
+bn_expand_internal(const BIGNUM *b, int words)
+{
+	BN_ULONG *A, *a = NULL;
+	const BN_ULONG *B;
+	int i;
+
+	bn_check_top(b);
+
+	if (words > (INT_MAX/(4*BN_BITS2))) {
+		BNerror(BN_R_BIGNUM_TOO_LONG);
+		return NULL;
+	}
+	if (BN_get_flags(b, BN_FLG_STATIC_DATA)) {
+		BNerror(BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
+		return (NULL);
+	}
+	a = A = reallocarray(NULL, words, sizeof(BN_ULONG));
+	if (A == NULL) {
+		BNerror(ERR_R_MALLOC_FAILURE);
+		return (NULL);
+	}
+#if 1
+	B = b->d;
+	/* Check if the previous number needs to be copied */
+	if (B != NULL) {
+		for (i = b->top >> 2; i > 0; i--, A += 4, B += 4) {
+			/*
+			 * The fact that the loop is unrolled
+			 * 4-wise is a tribute to Intel. It's
+			 * the one that doesn't have enough
+			 * registers to accommodate more data.
+			 * I'd unroll it 8-wise otherwise:-)
+			 *
+			 *		<appro@fy.chalmers.se>
+			 */
+			BN_ULONG a0, a1, a2, a3;
+			a0 = B[0];
+			a1 = B[1];
+			a2 = B[2];
+			a3 = B[3];
+			A[0] = a0;
+			A[1] = a1;
+			A[2] = a2;
+			A[3] = a3;
+		}
+		switch (b->top & 3) {
+		case 3:
+			A[2] = B[2];
+		case 2:
+			A[1] = B[1];
+		case 1:
+			A[0] = B[0];
+		}
+	}
+
+#else
+	memset(A, 0, sizeof(BN_ULONG) * words);
+	memcpy(A, b->d, sizeof(b->d[0]) * b->top);
+#endif
+
+	return (a);
+}
+
+/* This is an internal function that can be used instead of bn_expand2()
+ * when there is a need to copy BIGNUMs instead of only expanding the
+ * data part, while still expanding them.
+ * Especially useful when needing to expand BIGNUMs that are declared
+ * 'const' and should therefore not be changed.
+ * The reason to use this instead of a BN_dup() followed by a bn_expand2()
+ * is memory allocation overhead.  A BN_dup() followed by a bn_expand2()
+ * will allocate new memory for the BIGNUM data twice, and free it once,
+ * while bn_dup_expand() makes sure allocation is made only once.
+ */
+
+#ifndef OPENSSL_NO_DEPRECATED
+BIGNUM *
+bn_dup_expand(const BIGNUM *b, int words)
+{
+	BIGNUM *r = NULL;
+
+	bn_check_top(b);
+
+	/* This function does not work if
+	 *      words <= b->dmax && top < words
+	 * because BN_dup() does not preserve 'dmax'!
+	 * (But bn_dup_expand() is not used anywhere yet.)
+	 */
+
+	if (words > b->dmax) {
+		BN_ULONG *a = bn_expand_internal(b, words);
+
+		if (a) {
+			r = BN_new();
+			if (r) {
+				r->top = b->top;
+				r->dmax = words;
+				r->neg = b->neg;
+				r->d = a;
+			} else {
+				/* r == NULL, BN_new failure */
+				free(a);
+			}
+		}
+		/* If a == NULL, there was an error in allocation in
+		   bn_expand_internal(), and NULL should be returned */
+	} else {
+		r = BN_dup(b);
+	}
+
+	bn_check_top(r);
+	return r;
+}
+#endif
+
+/* This is an internal function that should not be used in applications.
+ * It ensures that 'b' has enough room for a 'words' word number
+ * and initialises any unused part of b->d with leading zeros.
+ * It is mostly used by the various BIGNUM routines. If there is an error,
+ * NULL is returned. If not, 'b' is returned. */
+
+BIGNUM *
+bn_expand2(BIGNUM *b, int words)
+{
+	bn_check_top(b);
+
+	if (words > b->dmax) {
+		BN_ULONG *a = bn_expand_internal(b, words);
+		if (!a)
+			return NULL;
+		if (b->d)
+			freezero(b->d, b->dmax * sizeof(b->d[0]));
+		b->d = a;
+		b->dmax = words;
+	}
+
+/* None of this should be necessary because of what b->top means! */
+#if 0
+	/* NB: bn_wexpand() calls this only if the BIGNUM really has to grow */
+	if (b->top < b->dmax) {
+		int i;
+		BN_ULONG *A = &(b->d[b->top]);
+		for (i = (b->dmax - b->top) >> 3; i > 0; i--, A += 8) {
+			A[0] = 0;
+			A[1] = 0;
+			A[2] = 0;
+			A[3] = 0;
+			A[4] = 0;
+			A[5] = 0;
+			A[6] = 0;
+			A[7] = 0;
+		}
+		for (i = (b->dmax - b->top)&7; i > 0; i--, A++)
+			A[0] = 0;
+		assert(A == &(b->d[b->dmax]));
+	}
+#endif
+	bn_check_top(b);
+	return b;
+}
+
+BIGNUM *
+BN_dup(const BIGNUM *a)
+{
+	BIGNUM *t;
+
+	if (a == NULL)
+		return NULL;
+	bn_check_top(a);
+
+	t = BN_new();
+	if (t == NULL)
+		return NULL;
+	if (!BN_copy(t, a)) {
+		BN_free(t);
+		return NULL;
+	}
+	bn_check_top(t);
+	return t;
+}
+
+BIGNUM *
+BN_copy(BIGNUM *a, const BIGNUM *b)
+{
+	int i;
+	BN_ULONG *A;
+	const BN_ULONG *B;
+
+	bn_check_top(b);
+
+	if (a == b)
+		return (a);
+	if (bn_wexpand(a, b->top) == NULL)
+		return (NULL);
+
+#if 1
+	A = a->d;
+	B = b->d;
+	for (i = b->top >> 2; i > 0; i--, A += 4, B += 4) {
+		BN_ULONG a0, a1, a2, a3;
+		a0 = B[0];
+		a1 = B[1];
+		a2 = B[2];
+		a3 = B[3];
+		A[0] = a0;
+		A[1] = a1;
+		A[2] = a2;
+		A[3] = a3;
+	}
+	switch (b->top & 3) {
+	case 3:
+		A[2] = B[2];
+	case 2:
+		A[1] = B[1];
+	case 1:
+		A[0] = B[0];
+	}
+#else
+	memcpy(a->d, b->d, sizeof(b->d[0]) * b->top);
+#endif
+
+	a->top = b->top;
+	a->neg = b->neg;
+	bn_check_top(a);
+	return (a);
+}
+
+void
+BN_swap(BIGNUM *a, BIGNUM *b)
+{
+	int flags_old_a, flags_old_b;
+	BN_ULONG *tmp_d;
+	int tmp_top, tmp_dmax, tmp_neg;
+
+	bn_check_top(a);
+	bn_check_top(b);
+
+	flags_old_a = a->flags;
+	flags_old_b = b->flags;
+
+	tmp_d = a->d;
+	tmp_top = a->top;
+	tmp_dmax = a->dmax;
+	tmp_neg = a->neg;
+
+	a->d = b->d;
+	a->top = b->top;
+	a->dmax = b->dmax;
+	a->neg = b->neg;
+
+	b->d = tmp_d;
+	b->top = tmp_top;
+	b->dmax = tmp_dmax;
+	b->neg = tmp_neg;
+
+	a->flags = (flags_old_a & BN_FLG_MALLOCED) |
+	    (flags_old_b & BN_FLG_STATIC_DATA);
+	b->flags = (flags_old_b & BN_FLG_MALLOCED) |
+	    (flags_old_a & BN_FLG_STATIC_DATA);
+	bn_check_top(a);
+	bn_check_top(b);
+}
+
+void
+BN_clear(BIGNUM *a)
+{
+	bn_check_top(a);
+	if (a->d != NULL)
+		explicit_bzero(a->d, a->dmax * sizeof(a->d[0]));
+	a->top = 0;
+	a->neg = 0;
+}
+
+BN_ULONG
+BN_get_word(const BIGNUM *a)
+{
+	if (a->top > 1)
+		return BN_MASK2;
+	else if (a->top == 1)
+		return a->d[0];
+	/* a->top == 0 */
+	return 0;
+}
+
+BIGNUM *
+bn_expand(BIGNUM *a, int bits)
+{
+	if (bits > (INT_MAX - BN_BITS2 + 1))
+		return (NULL);
+
+	if (((bits + BN_BITS2 - 1) / BN_BITS2) <= a->dmax)
+		return (a);
+
+	return bn_expand2(a, (bits + BN_BITS2 - 1) / BN_BITS2);
+}
+
+int
+BN_set_word(BIGNUM *a, BN_ULONG w)
+{
+	bn_check_top(a);
+	if (bn_expand(a, (int)sizeof(BN_ULONG) * 8) == NULL)
+		return (0);
+	a->neg = 0;
+	a->d[0] = w;
+	a->top = (w ? 1 : 0);
+	bn_check_top(a);
+	return (1);
+}
+
+BIGNUM *
+BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
+{
+	unsigned int i, m;
+	unsigned int n;
+	BN_ULONG l;
+	BIGNUM *bn = NULL;
+
+	if (len < 0)
+		return (NULL);
+	if (ret == NULL)
+		ret = bn = BN_new();
+	if (ret == NULL)
+		return (NULL);
+	bn_check_top(ret);
+	l = 0;
+	n = len;
+	if (n == 0) {
+		ret->top = 0;
+		return (ret);
+	}
+	i = ((n - 1) / BN_BYTES) + 1;
+	m = ((n - 1) % (BN_BYTES));
+	if (bn_wexpand(ret, (int)i) == NULL) {
+		BN_free(bn);
+		return NULL;
+	}
+	ret->top = i;
+	ret->neg = 0;
+	while (n--) {
+		l = (l << 8L) | *(s++);
+		if (m-- == 0) {
+			ret->d[--i] = l;
+			l = 0;
+			m = BN_BYTES - 1;
+		}
+	}
+	/* need to call this due to clear byte at top if avoiding
+	 * having the top bit set (-ve number) */
+	bn_correct_top(ret);
+	return (ret);
+}
+
+/* ignore negative */
+int
+BN_bn2bin(const BIGNUM *a, unsigned char *to)
+{
+	int n, i;
+	BN_ULONG l;
+
+	bn_check_top(a);
+	n = i=BN_num_bytes(a);
+	while (i--) {
+		l = a->d[i / BN_BYTES];
+		*(to++) = (unsigned char)(l >> (8 * (i % BN_BYTES))) & 0xff;
+	}
+	return (n);
+}
+
+int
+BN_ucmp(const BIGNUM *a, const BIGNUM *b)
+{
+	int i;
+	BN_ULONG t1, t2, *ap, *bp;
+
+	bn_check_top(a);
+	bn_check_top(b);
+
+	i = a->top - b->top;
+	if (i != 0)
+		return (i);
+	ap = a->d;
+	bp = b->d;
+	for (i = a->top - 1; i >= 0; i--) {
+		t1 = ap[i];
+		t2 = bp[i];
+		if (t1 != t2)
+			return ((t1 > t2) ? 1 : -1);
+	}
+	return (0);
+}
+
+int
+BN_cmp(const BIGNUM *a, const BIGNUM *b)
+{
+	int i;
+	int gt, lt;
+	BN_ULONG t1, t2;
+
+	if ((a == NULL) || (b == NULL)) {
+		if (a != NULL)
+			return (-1);
+		else if (b != NULL)
+			return (1);
+		else
+			return (0);
+	}
+
+	bn_check_top(a);
+	bn_check_top(b);
+
+	if (a->neg != b->neg) {
+		if (a->neg)
+			return (-1);
+		else
+			return (1);
+	}
+	if (a->neg == 0) {
+		gt = 1;
+		lt = -1;
+	} else {
+		gt = -1;
+		lt = 1;
+	}
+
+	if (a->top > b->top)
+		return (gt);
+	if (a->top < b->top)
+		return (lt);
+	for (i = a->top - 1; i >= 0; i--) {
+		t1 = a->d[i];
+		t2 = b->d[i];
+		if (t1 > t2)
+			return (gt);
+		if (t1 < t2)
+			return (lt);
+	}
+	return (0);
+}
+
+int
+BN_set_bit(BIGNUM *a, int n)
+{
+	int i, j, k;
+
+	if (n < 0)
+		return 0;
+
+	i = n / BN_BITS2;
+	j = n % BN_BITS2;
+	if (a->top <= i) {
+		if (bn_wexpand(a, i + 1) == NULL)
+			return (0);
+		for (k = a->top; k < i + 1; k++)
+			a->d[k] = 0;
+		a->top = i + 1;
+	}
+
+	a->d[i] |= (((BN_ULONG)1) << j);
+	bn_check_top(a);
+	return (1);
+}
+
+int
+BN_clear_bit(BIGNUM *a, int n)
+{
+	int i, j;
+
+	bn_check_top(a);
+	if (n < 0)
+		return 0;
+
+	i = n / BN_BITS2;
+	j = n % BN_BITS2;
+	if (a->top <= i)
+		return (0);
+
+	a->d[i] &= (~(((BN_ULONG)1) << j));
+	bn_correct_top(a);
+	return (1);
+}
+
+int
+BN_is_bit_set(const BIGNUM *a, int n)
+{
+	int i, j;
+
+	bn_check_top(a);
+	if (n < 0)
+		return 0;
+	i = n / BN_BITS2;
+	j = n % BN_BITS2;
+	if (a->top <= i)
+		return 0;
+	return (int)(((a->d[i]) >> j) & ((BN_ULONG)1));
+}
+
+int
+BN_mask_bits(BIGNUM *a, int n)
+{
+	int b, w;
+
+	bn_check_top(a);
+	if (n < 0)
+		return 0;
+
+	w = n / BN_BITS2;
+	b = n % BN_BITS2;
+	if (w >= a->top)
+		return 0;
+	if (b == 0)
+		a->top = w;
+	else {
+		a->top = w + 1;
+		a->d[w] &= ~(BN_MASK2 << b);
+	}
+	bn_correct_top(a);
+	return (1);
+}
+
+void
+BN_set_negative(BIGNUM *a, int b)
+{
+	if (b && !BN_is_zero(a))
+		a->neg = 1;
+	else
+		a->neg = 0;
+}
+
+int
+bn_cmp_words(const BN_ULONG *a, const BN_ULONG *b, int n)
+{
+	int i;
+	BN_ULONG aa, bb;
+
+	aa = a[n - 1];
+	bb = b[n - 1];
+	if (aa != bb)
+		return ((aa > bb) ? 1 : -1);
+	for (i = n - 2; i >= 0; i--) {
+		aa = a[i];
+		bb = b[i];
+		if (aa != bb)
+			return ((aa > bb) ? 1 : -1);
+	}
+	return (0);
+}
+
+/* Here follows a specialised variants of bn_cmp_words().  It has the
+   property of performing the operation on arrays of different sizes.
+   The sizes of those arrays is expressed through cl, which is the
+   common length ( basicall, min(len(a),len(b)) ), and dl, which is the
+   delta between the two lengths, calculated as len(a)-len(b).
+   All lengths are the number of BN_ULONGs...  */
+
+int
+bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *b, int cl, int dl)
+{
+	int n, i;
+
+	n = cl - 1;
+
+	if (dl < 0) {
+		for (i = dl; i < 0; i++) {
+			if (b[n - i] != 0)
+				return -1; /* a < b */
+		}
+	}
+	if (dl > 0) {
+		for (i = dl; i > 0; i--) {
+			if (a[n + i] != 0)
+				return 1; /* a > b */
+		}
+	}
+	return bn_cmp_words(a, b, cl);
+}
+
+/*
+ * Constant-time conditional swap of a and b.
+ * a and b are swapped if condition is not 0.
+ * The code assumes that at most one bit of condition is set.
+ * nwords is the number of words to swap.
+ * The code assumes that at least nwords are allocated in both a and b,
+ * and that no more than nwords are used by either a or b.
+ * a and b cannot be the same number
+ */
+void
+BN_consttime_swap(BN_ULONG condition, BIGNUM *a, BIGNUM *b, int nwords)
+{
+	BN_ULONG t;
+	int i;
+
+	bn_wcheck_size(a, nwords);
+	bn_wcheck_size(b, nwords);
+
+	assert(a != b);
+	assert((condition & (condition - 1)) == 0);
+	assert(sizeof(BN_ULONG) >= sizeof(int));
+
+	condition = ((condition - 1) >> (BN_BITS2 - 1)) - 1;
+
+	t = (a->top^b->top) & condition;
+	a->top ^= t;
+	b->top ^= t;
+
+#define BN_CONSTTIME_SWAP(ind) \
+	do { \
+		t = (a->d[ind] ^ b->d[ind]) & condition; \
+		a->d[ind] ^= t; \
+		b->d[ind] ^= t; \
+	} while (0)
+
+
+	switch (nwords) {
+	default:
+		for (i = 10; i < nwords; i++)
+			BN_CONSTTIME_SWAP(i);
+		/* Fallthrough */
+	case 10: BN_CONSTTIME_SWAP(9); /* Fallthrough */
+	case 9: BN_CONSTTIME_SWAP(8); /* Fallthrough */
+	case 8: BN_CONSTTIME_SWAP(7); /* Fallthrough */
+	case 7: BN_CONSTTIME_SWAP(6); /* Fallthrough */
+	case 6: BN_CONSTTIME_SWAP(5); /* Fallthrough */
+	case 5: BN_CONSTTIME_SWAP(4); /* Fallthrough */
+	case 4: BN_CONSTTIME_SWAP(3); /* Fallthrough */
+	case 3: BN_CONSTTIME_SWAP(2); /* Fallthrough */
+	case 2: BN_CONSTTIME_SWAP(1); /* Fallthrough */
+	case 1:
+		BN_CONSTTIME_SWAP(0);
+	}
+#undef BN_CONSTTIME_SWAP
+}
+
+/*
+ * Constant-time conditional swap of a and b.
+ * a and b are swapped if condition is not 0.
+ * nwords is the number of words to swap.
+ */
+int
+BN_swap_ct(BN_ULONG condition, BIGNUM *a, BIGNUM *b, size_t nwords)
+{
+	BN_ULONG t;
+	int i, words;
+
+	if (a == b)
+		return 1;
+	if (nwords > INT_MAX)
+		return 0;
+	words = (int)nwords;
+	if (bn_wexpand(a, words) == NULL || bn_wexpand(b, words) == NULL)
+		return 0;
+	if (a->top > words || b->top > words) {
+		BNerror(BN_R_INVALID_LENGTH);
+		return 0;
+	}
+
+	/* Set condition to 0 (if it was zero) or all 1s otherwise. */
+	condition = ((~condition & (condition - 1)) >> (BN_BITS2 - 1)) - 1;
+
+	/* swap top field */
+	t = (a->top ^ b->top) & condition;
+	a->top ^= t;
+	b->top ^= t;
+
+	/* swap neg field */
+	t = (a->neg ^ b->neg) & condition;
+	a->neg ^= t;
+	b->neg ^= t;
+
+	/* swap BN_FLG_CONSTTIME from flag field */
+	t = ((a->flags ^ b->flags) & BN_FLG_CONSTTIME) & condition;
+	a->flags ^= t;
+	b->flags ^= t;
+
+	/* swap the data */
+	for (i = 0; i < words; i++) {
+		t = (a->d[i] ^ b->d[i]) & condition;
+		a->d[i] ^= t;
+		b->d[i] ^= t;
+	}
+
+	return 1;
+}
+
+BN_GENCB *
+BN_GENCB_new(void)
+{
+	BN_GENCB *cb;
+
+	if ((cb = calloc(1, sizeof(*cb))) == NULL)
+		return NULL;
+
+	return cb;
+}
+
+void
+BN_GENCB_free(BN_GENCB *cb)
+{
+	if (cb == NULL)
+		return;
+	free(cb);
+}
+
+void *
+BN_GENCB_get_arg(BN_GENCB *cb)
+{
+	return cb->arg;
+}