size_tification.
[openssl.git] / crypto / bn / bn_lib.c
index 0ad6265..f22d358 100644 (file)
 #endif
 
 #include <assert.h>
+#include <limits.h>
 #include <stdio.h>
 #include "cryptlib.h"
 #include "bn_lcl.h"
 
-const char *BN_version="Big Number" OPENSSL_VERSION_PTEXT;
+const char BN_version[]="Big Number" OPENSSL_VERSION_PTEXT;
 
+/* 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
@@ -90,28 +93,28 @@ void BN_set_params(int mult, int high, int low, int mont)
        {
        if (mult >= 0)
                {
-               if (mult > (sizeof(int)*8)-1)
+               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 > (sizeof(int)*8)-1)
+               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 > (sizeof(int)*8)-1)
+               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 > (sizeof(int)*8)-1)
+               if (mont > (int)(sizeof(int)*8)-1)
                        mont=sizeof(int)*8-1;
                bn_limit_bits_mont=mont;
                bn_limit_num_mont=1<<mont;
@@ -126,11 +129,12 @@ int BN_get_params(int which)
        else if (which == 3) return(bn_limit_bits_mont);
        else return(0);
        }
+#endif
 
-BIGNUM *BN_value_one(void)
+const BIGNUM *BN_value_one(void)
        {
-       static BN_ULONG data_one=1L;
-       static BIGNUM const_one={&data_one,1,1,0};
+       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);
        }
@@ -144,11 +148,11 @@ char *BN_options(void)
                {
                init++;
 #ifdef BN_LLONG
-               sprintf(data,"bn(%d,%d)",(int)sizeof(BN_ULLONG)*8,
-                       (int)sizeof(BN_ULONG)*8);
+               BIO_snprintf(data,sizeof data,"bn(%d,%d)",
+                            (int)sizeof(BN_ULLONG)*8,(int)sizeof(BN_ULONG)*8);
 #else
-               sprintf(data,"bn(%d,%d)",(int)sizeof(BN_ULONG)*8,
-                       (int)sizeof(BN_ULONG)*8);
+               BIO_snprintf(data,sizeof data,"bn(%d,%d)",
+                            (int)sizeof(BN_ULONG)*8,(int)sizeof(BN_ULONG)*8);
 #endif
                }
        return(data);
@@ -156,7 +160,7 @@ char *BN_options(void)
 
 int BN_num_bits_word(BN_ULONG l)
        {
-       static const char bits[256]={
+       static const unsigned char bits[256]={
                0,1,2,2,3,3,3,3,4,4,4,4,4,4,4,4,
                5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
                6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
@@ -231,7 +235,7 @@ int BN_num_bits_word(BN_ULONG l)
                else
 #endif
                        {
-#if defined(SIXTEEN_BIT) || defined(THIRTY_TWO_BIT) || defined(SIXTY_FOUR_BIT) || defined(SIXTY_FOUR_BIT_LONG)
+#if defined(THIRTY_TWO_BIT) || defined(SIXTY_FOUR_BIT) || defined(SIXTY_FOUR_BIT_LONG)
                        if (l & 0xff00L)
                                return(bits[(int)(l>>8)]+8);
                        else    
@@ -243,16 +247,11 @@ int BN_num_bits_word(BN_ULONG l)
 
 int BN_num_bits(const BIGNUM *a)
        {
-       BN_ULONG l;
-       int i;
-
+       int i = a->top - 1;
        bn_check_top(a);
 
-       if (a->top == 0) return(0);
-       l=a->d[a->top-1];
-       assert(l != 0);
-       i=(a->top-1)*BN_BITS2;
-       return(i+BN_num_bits_word(l));
+       if (BN_is_zero(a)) return 0;
+       return ((i*BN_BITS2) + BN_num_bits_word(a->d[i]));
        }
 
 void BN_clear_free(BIGNUM *a)
@@ -260,14 +259,15 @@ void BN_clear_free(BIGNUM *a)
        int i;
 
        if (a == NULL) return;
+       bn_check_top(a);
        if (a->d != NULL)
                {
-               memset(a->d,0,a->dmax*sizeof(a->d[0]));
+               OPENSSL_cleanse(a->d,a->dmax*sizeof(a->d[0]));
                if (!(BN_get_flags(a,BN_FLG_STATIC_DATA)))
                        OPENSSL_free(a->d);
                }
        i=BN_get_flags(a,BN_FLG_MALLOCED);
-       memset(a,0,sizeof(BIGNUM));
+       OPENSSL_cleanse(a,sizeof(BIGNUM));
        if (i)
                OPENSSL_free(a);
        }
@@ -275,16 +275,24 @@ void BN_clear_free(BIGNUM *a)
 void BN_free(BIGNUM *a)
        {
        if (a == NULL) return;
+       bn_check_top(a);
        if ((a->d != NULL) && !(BN_get_flags(a,BN_FLG_STATIC_DATA)))
                OPENSSL_free(a->d);
-       a->flags|=BN_FLG_FREE; /* REMOVE? */
        if (a->flags & BN_FLG_MALLOCED)
                OPENSSL_free(a);
+       else
+               {
+#ifndef OPENSSL_NO_DEPRECATED
+               a->flags|=BN_FLG_FREE;
+#endif
+               a->d = NULL;
+               }
        }
 
 void BN_init(BIGNUM *a)
        {
        memset(a,0,sizeof(BIGNUM));
+       bn_check_top(a);
        }
 
 BIGNUM *BN_new(void)
@@ -301,27 +309,34 @@ BIGNUM *BN_new(void)
        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 *internal_bn_expand(const BIGNUM *b, int words)
+static BN_ULONG *bn_expand_internal(const BIGNUM *b, size_t words)
        {
        BN_ULONG *A,*a = NULL;
        const BN_ULONG *B;
        int i;
 
-       bn_check_top(b);        
+       bn_check_top(b);
+
+       if (words > (INT_MAX/(4*BN_BITS2)))
+               {
+               BNerr(BN_F_BN_EXPAND_INTERNAL,BN_R_BIGNUM_TOO_LONG);
+               return NULL;
+               }
        if (BN_get_flags(b,BN_FLG_STATIC_DATA))
                {
-               BNerr(BN_F_BN_EXPAND2,BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
+               BNerr(BN_F_BN_EXPAND_INTERNAL,BN_R_EXPAND_ON_STATIC_BIGNUM_DATA);
                return(NULL);
                }
-       a=A=(BN_ULONG *)OPENSSL_malloc(sizeof(BN_ULONG)*(words+1));
+       a=A=(BN_ULONG *)OPENSSL_malloc(sizeof(BN_ULONG)*words);
        if (A == NULL)
                {
-               BNerr(BN_F_BN_EXPAND2,ERR_R_MALLOC_FAILURE);
+               BNerr(BN_F_BN_EXPAND_INTERNAL,ERR_R_MALLOC_FAILURE);
                return(NULL);
                }
 #if 1
@@ -329,70 +344,6 @@ static BN_ULONG *internal_bn_expand(const BIGNUM *b, int words)
        /* Check if the previous number needs to be copied */
        if (B != NULL)
                {
-#if 0
-               /* This lot is an unrolled loop to copy b->top 
-                * BN_ULONGs from B to A
-                */
-/*
- * I have nothing against unrolling but it's usually done for
- * several reasons, namely:
- * - minimize percentage of decision making code, i.e. branches;
- * - avoid cache trashing;
- * - make it possible to schedule loads earlier;
- * Now let's examine the code below. The cornerstone of C is
- * "programmer is always right" and that's what we love it for:-)
- * For this very reason C compilers have to be paranoid when it
- * comes to data aliasing and assume the worst. Yeah, but what
- * does it mean in real life? This means that loop body below will
- * be compiled to sequence of loads immediately followed by stores
- * as compiler assumes the worst, something in A==B+1 style. As a
- * result CPU pipeline is going to starve for incoming data. Secondly
- * if A and B happen to share same cache line such code is going to
- * cause severe cache trashing. Both factors have severe impact on
- * performance of modern CPUs and this is the reason why this
- * particular piece of code is #ifdefed away and replaced by more
- * "friendly" version found in #else section below. This comment
- * also applies to BN_copy function.
- *
- *                                     <appro@fy.chalmers.se>
- */
-               for (i=b->top&(~7); i>0; i-=8)
-                       {
-                       A[0]=B[0]; A[1]=B[1]; A[2]=B[2]; A[3]=B[3];
-                       A[4]=B[4]; A[5]=B[5]; A[6]=B[6]; A[7]=B[7];
-                       A+=8;
-                       B+=8;
-                       }
-               switch (b->top&7)
-                       {
-               case 7:
-                       A[6]=B[6];
-               case 6:
-                       A[5]=B[5];
-               case 5:
-                       A[4]=B[4];
-               case 4:
-                       A[3]=B[3];
-               case 3:
-                       A[2]=B[2];
-               case 2:
-                       A[1]=B[1];
-               case 1:
-                       A[0]=B[0];
-               case 0:
-                       /* I need the 'case 0' entry for utrix cc.
-                        * If the optimizer is turned on, it does the
-                        * switch table by doing
-                        * a=top&7
-                        * a--;
-                        * goto jump_table[a];
-                        * If top is 0, this makes us jump to 0xffffffc 
-                        * which is rather bad :-(.
-                        * eric 23-Apr-1998
-                        */
-                       ;
-                       }
-#else
                for (i=b->top>>2; i>0; i--,A+=4,B+=4)
                        {
                        /*
@@ -413,23 +364,15 @@ static BN_ULONG *internal_bn_expand(const BIGNUM *b, int words)
                case 3: A[2]=B[2];
                case 2: A[1]=B[1];
                case 1: A[0]=B[0];
-               case 0: ; /* ultrix cc workaround, see above */
+               case 0: /* workaround for ultrix cc: without 'case 0', the optimizer does
+                        * the switch table by doing a=top&3; a--; goto jump_table[a];
+                        * which fails for top== 0 */
+                       ;
                        }
-#endif
                }
 
-       /* Now need to zero any data between b->top and b->max */
-
-       A= &(a[b->top]);
-       for (i=(words - 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=(words - b->top)&7; i>0; i--,A++)
-               A[0]=0;
 #else
-       memset(A,0,sizeof(BN_ULONG)*(words+1));
+       memset(A,0,sizeof(BN_ULONG)*words);
        memcpy(A,b->d,sizeof(b->d[0])*b->top);
 #endif
                
@@ -447,13 +390,22 @@ static BN_ULONG *internal_bn_expand(const BIGNUM *b, int words)
  * while bn_dup_expand() makes sure allocation is made only once.
  */
 
-BIGNUM *bn_dup_expand(const BIGNUM *b, int words)
+#ifndef OPENSSL_NO_DEPRECATED
+BIGNUM *bn_dup_expand(const BIGNUM *b, size_t 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 = internal_bn_expand(b, words);
+               BN_ULONG *a = bn_expand_internal(b, words);
 
                if (a)
                        {
@@ -472,54 +424,74 @@ BIGNUM *bn_dup_expand(const BIGNUM *b, int words)
                                }
                        }
                /* If a == NULL, there was an error in allocation in
-                  internal_bn_expand(), and NULL should be returned */
+                  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 number.
+ * 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)
+BIGNUM *bn_expand2(BIGNUM *b, size_t words)
        {
+       bn_check_top(b);
+
        if (words > b->dmax)
                {
-               BN_ULONG *a = internal_bn_expand(b, words);
+               BN_ULONG *a = bn_expand_internal(b, words);
+               if(!a) return NULL;
+               if(b->d) OPENSSL_free(b->d);
+               b->d=a;
+               b->dmax=words;
+               }
 
-               if (a)
+/* 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)
                        {
-                       OPENSSL_free(b->d);
-                       b->d=a;
-                       b->dmax=words;
+                       A[0]=0; A[1]=0; A[2]=0; A[3]=0;
+                       A[4]=0; A[5]=0; A[6]=0; A[7]=0;
                        }
-               else
-                       b = NULL;
+               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 *r, *t;
+       BIGNUM *t;
 
        if (a == NULL) return NULL;
-
        bn_check_top(a);
 
        t = BN_new();
-       if (t == NULL) return(NULL);
-       r = BN_copy(t, a);
-       /* now  r == t || r == NULL */
-       if (r == NULL)
+       if (t == NULL) return NULL;
+       if(!BN_copy(t, a))
+               {
                BN_free(t);
-       return r;
+               return NULL;
+               }
+       bn_check_top(t);
+       return t;
        }
 
 BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
@@ -547,22 +519,54 @@ BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
                case 3: A[2]=B[2];
                case 2: A[1]=B[1];
                case 1: A[0]=B[0];
-               case 0: ; /* ultrix cc workaround, see comments in bn_expand2 */
+               case 0: ; /* ultrix cc workaround, see comments in bn_expand_internal */
                }
 #else
        memcpy(a->d,b->d,sizeof(b->d[0])*b->top);
 #endif
 
-/*     memset(&(a->d[b->top]),0,sizeof(a->d[0])*(a->max-b->top));*/
        a->top=b->top;
-       if ((a->top == 0) && (a->d != NULL))
-               a->d[0]=0;
        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)
                memset(a->d,0,a->dmax*sizeof(a->d[0]));
        a->top=0;
@@ -571,61 +575,36 @@ void BN_clear(BIGNUM *a)
 
 BN_ULONG BN_get_word(const BIGNUM *a)
        {
-       int i,n;
-       BN_ULONG ret=0;
-
-       n=BN_num_bytes(a);
-       if (n > sizeof(BN_ULONG))
-               return(BN_MASK2);
-       for (i=a->top-1; i>=0; i--)
-               {
-#ifndef SIXTY_FOUR_BIT /* the data item > unsigned long */
-               ret<<=BN_BITS4; /* stops the compiler complaining */
-               ret<<=BN_BITS4;
-#else
-               ret=0;
-#endif
-               ret|=a->d[i];
-               }
-       return(ret);
+       if (a->top > 1)
+               return BN_MASK2;
+       else if (a->top == 1)
+               return a->d[0];
+       /* a->top == 0 */
+       return 0;
        }
 
 int BN_set_word(BIGNUM *a, BN_ULONG w)
        {
-       int i,n;
-       if (bn_expand(a,sizeof(BN_ULONG)*8) == NULL) return(0);
-
-       n=sizeof(BN_ULONG)/BN_BYTES;
-       a->neg=0;
-       a->top=0;
-       a->d[0]=(BN_ULONG)w&BN_MASK2;
-       if (a->d[0] != 0) a->top=1;
-       for (i=1; i<n; i++)
-               {
-               /* the following is done instead of
-                * w>>=BN_BITS2 so compilers don't complain
-                * on builds where sizeof(long) == BN_TYPES */
-#ifndef SIXTY_FOUR_BIT /* the data item > unsigned long */
-               w>>=BN_BITS4;
-               w>>=BN_BITS4;
-#else
-               w=0;
-#endif
-               a->d[i]=(BN_ULONG)w&BN_MASK2;
-               if (a->d[i] != 0) a->top=i+1;
-               }
+       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);
        }
 
-/* ignore negative */
-BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
+BIGNUM *BN_bin2bn(const unsigned char *s, size_t len, BIGNUM *ret)
        {
        unsigned int i,m;
        unsigned int n;
        BN_ULONG l;
+       BIGNUM  *bn = NULL;
 
-       if (ret == NULL) ret=BN_new();
+       if (ret == NULL)
+               ret = bn = BN_new();
        if (ret == NULL) return(NULL);
+       bn_check_top(ret);
        l=0;
        n=len;
        if (n == 0)
@@ -633,12 +612,16 @@ BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
                ret->top=0;
                return(ret);
                }
-       if (bn_expand(ret,(int)(n+2)*8) == NULL)
-               return(NULL);
        i=((n-1)/BN_BYTES)+1;
        m=((n-1)%(BN_BYTES));
+       if (bn_wexpand(ret, i) == NULL)
+               {
+               if (bn) BN_free(bn);
+               return NULL;
+               }
        ret->top=i;
-       while (n-- > 0)
+       ret->neg=0;
+       while (n--)
                {
                l=(l<<8L)| *(s++);
                if (m-- == 0)
@@ -650,7 +633,7 @@ BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret)
                }
        /* need to call this due to clear byte at top if avoiding
         * having the top bit set (-ve number) */
-       bn_fix_top(ret);
+       bn_correct_top(ret);
        return(ret);
        }
 
@@ -660,8 +643,9 @@ 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-- > 0)
+       while (i--)
                {
                l=a->d[i/BN_BYTES];
                *(to++)=(unsigned char)(l>>(8*(i%BN_BYTES)))&0xff;
@@ -686,7 +670,7 @@ int BN_ucmp(const BIGNUM *a, const BIGNUM *b)
                t1= ap[i];
                t2= bp[i];
                if (t1 != t2)
-                       return(t1 > t2?1:-1);
+                       return((t1 > t2) ? 1 : -1);
                }
        return(0);
        }
@@ -734,7 +718,10 @@ int BN_cmp(const BIGNUM *a, const BIGNUM *b)
 
 int BN_set_bit(BIGNUM *a, int n)
        {
-       int i,j,k;
+       size_t i,j,k;
+
+       if (n < 0)
+               return 0;
 
        i=n/BN_BITS2;
        j=n%BN_BITS2;
@@ -747,6 +734,7 @@ int BN_set_bit(BIGNUM *a, int n)
                }
 
        a->d[i]|=(((BN_ULONG)1)<<j);
+       bn_check_top(a);
        return(1);
        }
 
@@ -754,12 +742,15 @@ 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_fix_top(a);
+       bn_correct_top(a);
        return(1);
        }
 
@@ -767,20 +758,24 @@ int BN_is_bit_set(const BIGNUM *a, int n)
        {
        int i,j;
 
-       if (n < 0) return(0);
+       bn_check_top(a);
+       if (n < 0) return 0;
        i=n/BN_BITS2;
        j=n%BN_BITS2;
-       if (a->top <= i) return(0);
-       return((a->d[i]&(((BN_ULONG)1)<<j))?1:0);
+       if (a->top <= i) return 0;
+       return(((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 (w >= a->top) return 0;
        if (b == 0)
                a->top=w;
        else
@@ -788,11 +783,19 @@ int BN_mask_bits(BIGNUM *a, int n)
                a->top=w+1;
                a->d[w]&= ~(BN_MASK2<<b);
                }
-       bn_fix_top(a);
+       bn_correct_top(a);
        return(1);
        }
 
-int bn_cmp_words(BN_ULONG *a, BN_ULONG *b, int n)
+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;
@@ -809,3 +812,34 @@ int bn_cmp_words(BN_ULONG *a, BN_ULONG *b, int n)
        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);
+       }