1 files changed, 15 insertions, 12 deletions

diff --git a/src/lib/libcrypto/bn/bn_shift.c b/src/lib/libcrypto/bn/bn_shift.c
index c4d301afc4..a6fca2c424 100644
--- a/src/lib/libcrypto/bn/bn_shift.c
+++ b/src/lib/libcrypto/bn/bn_shift.c
@@ -99,7 +99,7 @@ int BN_lshift1(BIGNUM *r, const BIGNUM *a)
 int BN_rshift1(BIGNUM *r, const BIGNUM *a)
         {
         BN_ULONG *ap,*rp,t,c;
-        int i;
+        int i,j;
 
         bn_check_top(r);
         bn_check_top(a);
@@ -109,22 +109,25 @@ int BN_rshift1(BIGNUM *r, const BIGNUM *a)
                 BN_zero(r);
                 return(1);
                 }
+        i = a->top;
+        ap= a->d;
+        j = i-(ap[i-1]==1);
         if (a != r)
                 {
-                if (bn_wexpand(r,a->top) == NULL) return(0);
-                r->top=a->top;
+                if (bn_wexpand(r,j) == NULL) return(0);
                 r->neg=a->neg;
                 }
-        ap=a->d;
         rp=r->d;
-        c=0;
-        for (i=a->top-1; i>=0; i--)
+        t=ap[--i];
+        c=(t&1)?BN_TBIT:0;
+        if (t>>=1) rp[i]=t;
+        while (i>0)
                 {
-                t=ap[i];
+                t=ap[--i];
                 rp[i]=((t>>1)&BN_MASK2)|c;
                 c=(t&1)?BN_TBIT:0;
                 }
-        bn_correct_top(r);
+        r->top=j;
         bn_check_top(r);
         return(1);
         }
@@ -182,10 +185,11 @@ int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
                 BN_zero(r);
                 return(1);
                 }
+        i = (BN_num_bits(a)-n+(BN_BITS2-1))/BN_BITS2;
         if (r != a)
                 {
                 r->neg=a->neg;
-                if (bn_wexpand(r,a->top-nw+1) == NULL) return(0);
+                if (bn_wexpand(r,i) == NULL) return(0);
                 }
         else
                 {
@@ -196,7 +200,7 @@ int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
         f= &(a->d[nw]);
         t=r->d;
         j=a->top-nw;
-        r->top=j;
+        r->top=i;
 
         if (rb == 0)
                 {
@@ -212,9 +216,8 @@ int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
                         l= *(f++);
                         *(t++) =(tmp|(l<<lb))&BN_MASK2;
                         }
-                *(t++) =(l>>rb)&BN_MASK2;
+                if ((l = (l>>rb)&BN_MASK2)) *(t) = l;
                 }
-        bn_correct_top(r);
         bn_check_top(r);
         return(1);
         }