X-Git-Url: https://git.openssl.org/gitweb/?a=blobdiff_plain;f=crypto%2Fbn%2Fbn_word.c;h=ee7b87c45ccd38839db6261ed81c2d87b9e881b5;hb=0f529cbdc354570dc872dbc72a37a9f85bebc9e8;hp=7e7ca58842bb92dbd732924a05d247d7aa8f6682;hpb=8b4e27e26efc097dbe65b0c3cd78a2da7be310ef;p=openssl.git

diff --git a/crypto/bn/bn_word.c b/crypto/bn/bn_word.c
index 7e7ca58842..ee7b87c45c 100644
--- a/crypto/bn/bn_word.c
+++ b/crypto/bn/bn_word.c
@@ -69,6 +69,10 @@ BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)
 #endif
 	int i;
 
+	if (w == 0)
+		return (BN_ULONG)-1;
+
+	bn_check_top(a);
 	w&=BN_MASK2;
 	for (i=a->top-1; i>=0; i--)
 		{
@@ -85,12 +89,24 @@ BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)
 
 BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)
 	{
-	BN_ULONG ret;
-	int i;
+	BN_ULONG ret = 0;
+	int i, j;
+
+	bn_check_top(a);
+	w &= BN_MASK2;
+
+	if (!w)
+		/* actually this an error (division by zero) */
+		return (BN_ULONG)-1;
+	if (a->top == 0)
+		return 0;
+
+	/* normalize input (so bn_div_words doesn't complain) */
+	j = BN_BITS2 - BN_num_bits_word(w);
+	w <<= j;
+	if (!BN_lshift(a, a, j))
+		return (BN_ULONG)-1;
 
-	if (a->top == 0) return(0);
-	ret=0;
-	w&=BN_MASK2;
 	for (i=a->top-1; i>=0; i--)
 		{
 		BN_ULONG l,d;
@@ -102,6 +118,8 @@ BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)
 		}
 	if ((a->top > 0) && (a->d[a->top-1] == 0))
 		a->top--;
+	ret >>= j;
+	bn_check_top(a);
 	return(ret);
 	}
 
@@ -110,6 +128,14 @@ int BN_add_word(BIGNUM *a, BN_ULONG w)
 	BN_ULONG l;
 	int i;
 
+	bn_check_top(a);
+	w &= BN_MASK2;
+
+	/* degenerate case: w is zero */
+	if (!w) return 1;
+	/* degenerate case: a is zero */
+	if(BN_is_zero(a)) return BN_set_word(a, w);
+	/* handle 'a' when negative */
 	if (a->neg)
 		{
 		a->neg=0;
@@ -118,12 +144,17 @@ int BN_add_word(BIGNUM *a, BN_ULONG w)
 			a->neg=!(a->neg);
 		return(i);
 		}
-	w&=BN_MASK2;
-	if (bn_wexpand(a,a->top+1) == NULL) return(0);
+	/* Only expand (and risk failing) if it's possibly necessary */
+	if (((BN_ULONG)(a->d[a->top - 1] + 1) == 0) &&
+			(bn_wexpand(a,a->top+1) == NULL))
+		return(0);
 	i=0;
 	for (;;)
 		{
-		l=(a->d[i]+(BN_ULONG)w)&BN_MASK2;
+		if (i >= a->top)
+			l=w;
+		else
+			l=(a->d[i]+w)&BN_MASK2;
 		a->d[i]=l;
 		if (w > l)
 			w=1;
@@ -133,6 +164,7 @@ int BN_add_word(BIGNUM *a, BN_ULONG w)
 		}
 	if (i >= a->top)
 		a->top++;
+	bn_check_top(a);
 	return(1);
 	}
 
@@ -140,6 +172,20 @@ int BN_sub_word(BIGNUM *a, BN_ULONG w)
 	{
 	int i;
 
+	bn_check_top(a);
+	w &= BN_MASK2;
+
+	/* degenerate case: w is zero */
+	if (!w) return 1;
+	/* degenerate case: a is zero */
+	if(BN_is_zero(a))
+		{
+		i = BN_set_word(a,w);
+		if (i != 0)
+			BN_set_negative(a, 1);
+		return i;
+		}
+	/* handle 'a' when negative */
 	if (a->neg)
 		{
 		a->neg=0;
@@ -148,7 +194,6 @@ int BN_sub_word(BIGNUM *a, BN_ULONG w)
 		return(i);
 		}
 
-	w&=BN_MASK2;
 	if ((a->top == 1) && (a->d[0] < w))
 		{
 		a->d[0]=w-a->d[0];
@@ -172,6 +217,7 @@ int BN_sub_word(BIGNUM *a, BN_ULONG w)
 		}
 	if ((a->d[i] == 0) && (i == (a->top-1)))
 		a->top--;
+	bn_check_top(a);
 	return(1);
 	}
 
@@ -179,16 +225,23 @@ int BN_mul_word(BIGNUM *a, BN_ULONG w)
 	{
 	BN_ULONG ll;
 
+	bn_check_top(a);
 	w&=BN_MASK2;
 	if (a->top)
 		{
-		ll=bn_mul_words(a->d,a->d,a->top,w);
-		if (ll)
+		if (w == 0)
+			BN_zero(a);
+		else
 			{
-			if (bn_wexpand(a,a->top+1) == NULL) return(0);
-			a->d[a->top++]=ll;
+			ll=bn_mul_words(a->d,a->d,a->top,w);
+			if (ll)
+				{
+				if (bn_wexpand(a,a->top+1) == NULL) return(0);
+				a->d[a->top++]=ll;
+				}
 			}
 		}
+	bn_check_top(a);
 	return(1);
 	}