Revert "CHANGES: mention "universal" ARM support."
[openssl.git] / crypto / bn / bn_lib.c
index 1f45b09d080b6c86593c5fe304a57d42ccccfc0c..886de0d81fb0d10488842760a9037816a21e7a09 100644 (file)
 # define NDEBUG
 #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;
 
-/* For a 32 bit machine
+/* 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
@@ -127,37 +131,19 @@ int BN_get_params(int which)
        else if (which == 3) return(bn_limit_bits_mont);
        else return(0);
        }
+#endif
 
 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);
        }
 
-char *BN_options(void)
-       {
-       static int init=0;
-       static char data[16];
-
-       if (!init)
-               {
-               init++;
-#ifdef BN_LLONG
-               sprintf(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);
-#endif
-               }
-       return(data);
-       }
-
 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,
@@ -232,7 +218,7 @@ 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    
@@ -244,16 +230,11 @@ 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)
@@ -261,6 +242,7 @@ void BN_clear_free(BIGNUM *a)
        int i;
 
        if (a == NULL) return;
+       bn_check_top(a);
        if (a->d != NULL)
                {
                OPENSSL_cleanse(a->d,a->dmax*sizeof(a->d[0]));
@@ -276,11 +258,18 @@ 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)
@@ -315,24 +304,33 @@ static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)
        const BN_ULONG *B;
        int i;
 
+       bn_check_top(b);
+
        if (words > (INT_MAX/(4*BN_BITS2)))
                {
                BNerr(BN_F_BN_EXPAND_INTERNAL,BN_R_BIGNUM_TOO_LONG);
                return NULL;
                }
-
-       bn_check_top(b);        
        if (BN_get_flags(b,BN_FLG_STATIC_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_EXPAND_INTERNAL,ERR_R_MALLOC_FAILURE);
                return(NULL);
                }
+#ifdef PURIFY
+       /* Valgrind complains in BN_consttime_swap because we process the whole
+        * array even if it's not initialised yet. This doesn't matter in that
+        * function - what's important is constant time operation (we're not
+        * actually going to use the data)
+       */
+       memset(a, 0, sizeof(BN_ULONG)*words);
+#endif
+
 #if 1
        B=b->d;
        /* Check if the previous number needs to be copied */
@@ -366,66 +364,13 @@ static BN_ULONG *bn_expand_internal(const BIGNUM *b, int words)
                }
 
 #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
                
        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.
- */
-
-BIGNUM *bn_dup_expand(const BIGNUM *b, int words)
-       {
-       BIGNUM *r = NULL;
-
-       /* 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 */
-                               OPENSSL_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;
-       }
-
 /* 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.
@@ -434,28 +379,24 @@ BIGNUM *bn_dup_expand(const BIGNUM *b, int words)
 
 BIGNUM *bn_expand2(BIGNUM *b, int words)
        {
-       BN_ULONG *A;
-       int i;
+       bn_check_top(b);
 
        if (words > b->dmax)
                {
                BN_ULONG *a = bn_expand_internal(b, words);
-
-               if (a)
-                       {
-                       if (b->d)
-                               OPENSSL_free(b->d);
-                       b->d=a;
-                       b->dmax=words;
-                       }
-               else
-                       b = NULL;
+               if(!a) return NULL;
+               if(b->d) OPENSSL_free(b->d);
+               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 != NULL) && (b->top < b->dmax))
+       if (b->top < b->dmax)
                {
-               A = &(b->d[b->top]);
+               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;
@@ -465,26 +406,27 @@ BIGNUM *bn_expand2(BIGNUM *b, int words)
                        A[0]=0;
                assert(A == &(b->d[b->dmax]));
                }
-       else if(b) bn_check_top(b);
+#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);
-       bn_check_top(r);
-       return r;
+               return NULL;
+               }
+       bn_check_top(t);
+       return t;
        }
 
 BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
@@ -518,67 +460,21 @@ BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
        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);
        }
 
-BIGNUM *BN_ncopy(BIGNUM *a, const BIGNUM *b, size_t n)
-       {
-       int i, min;
-       BN_ULONG *A;
-       const BN_ULONG *B;
-
-       bn_check_top(b);
-
-       if (a == b)
-               return a;
-
-       min = (b->top < (int)n)? b->top: (int)n;
-
-       if (!min)
-               {
-               BN_zero(a);
-               return a;
-               }
-
-       if (bn_wexpand(a, min) == NULL)
-               return NULL;
-
-       A=a->d;
-       B=b->d;
-       for (i=min>>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 (min&3)
-               {
-               case 3: A[2]=B[2];
-               case 2: A[1]=B[1];
-               case 1: A[0]=B[0];
-               case 0: ;
-               }
-       a->top = min;
-
-       a->neg = b->neg;
-       bn_correct_top(a);
-
-       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;
 
@@ -603,61 +499,32 @@ void BN_swap(BIGNUM *a, BIGNUM *b)
        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;
        a->neg=0;
-       bn_check_top(a);
        }
 
 BN_ULONG BN_get_word(const BIGNUM *a)
        {
-       int i,n;
-       BN_ULONG ret=0;
-
-       n=BN_num_bytes(a);
-       if (n > (int)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;
+       bn_check_top(a);
        if (bn_expand(a,(int)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;
-               }
+       a->neg = 0;
+       a->d[0] = w;
+       a->top = (w ? 1 : 0);
        bn_check_top(a);
        return(1);
        }
@@ -667,9 +534,12 @@ 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 (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)
@@ -677,13 +547,16 @@ 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, (int)i) == NULL)
+               {
+               if (bn) BN_free(bn);
+               return NULL;
+               }
        ret->top=i;
        ret->neg=0;
-       while (n-- > 0)
+       while (n--)
                {
                l=(l<<8L)| *(s++);
                if (m-- == 0)
@@ -705,13 +578,13 @@ 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;
                }
-       bn_check_top(a);
        return(n);
        }
 
@@ -732,7 +605,7 @@ 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);
        }
@@ -782,6 +655,9 @@ 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)
@@ -801,6 +677,9 @@ 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);
@@ -814,20 +693,24 @@ 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 (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 (w >= a->top) return 0;
        if (b == 0)
                a->top=w;
        else
@@ -839,6 +722,14 @@ int BN_mask_bits(BIGNUM *a, int n)
        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;
@@ -887,3 +778,206 @@ int bn_cmp_part_words(const BN_ULONG *a, const BN_ULONG *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
+}
+
+/* Bits of security, see SP800-57 */
+
+int BN_security_bits(int L, int N)
+       {
+       int secbits, bits;
+       if (L >= 15360)
+               secbits = 256;
+       else if (L >= 7690)
+               secbits = 192;
+       else if (L >= 3072)
+               secbits = 128;
+       else if (L >= 2048)
+               secbits = 112;
+       else if (L >= 1024)
+               secbits = 80;
+       else
+               return 0;
+       if (N == -1)
+               return secbits;
+       bits = N / 2;
+       if (bits < 80)
+               return 0;
+       return bits >= secbits ? secbits : bits;
+       }
+
+
+void BN_zero_ex(BIGNUM *a)
+       {
+       a->top = 0;
+       a->neg = 0;
+       }
+
+int BN_abs_is_word(const BIGNUM *a, const BN_ULONG w)
+       {
+       return ((a->top == 1) && (a->d[0] == w)) || ((w == 0) && (a->top == 0));
+       }
+
+int BN_is_zero(const BIGNUM *a)
+       {
+       return a->top == 0;
+       }
+
+int BN_is_one(const BIGNUM *a)
+       {
+       return BN_abs_is_word(a, 1) && !a->neg;
+       }
+
+int BN_is_word(const BIGNUM *a, const BN_ULONG w)
+       {
+       return BN_abs_is_word(a, w) && (!w || !a->neg);
+       }
+
+int BN_is_odd(const BIGNUM *a)
+       {
+       return (a->top > 0) && (a->d[0] & 1);
+       }
+
+int BN_is_negative(const BIGNUM *a)
+       {
+       return (a->neg != 0);
+       }
+
+int BN_to_montgomery(BIGNUM *r,const BIGNUM *a,        BN_MONT_CTX *mont, BN_CTX *ctx)
+       {
+       return BN_mod_mul_montgomery(r,a,&(mont->RR),mont,ctx);
+       }
+
+void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int n)
+       {
+       dest->d=b->d;
+       dest->top=b->top;
+       dest->dmax=b->dmax;
+       dest->neg=b->neg;
+       dest->flags=((dest->flags & BN_FLG_MALLOCED)
+               |  (b->flags & ~BN_FLG_MALLOCED)
+               |  BN_FLG_STATIC_DATA
+               |  n);
+       }
+
+BN_GENCB *BN_GENCB_new(void)
+       {
+       BN_GENCB *ret;
+
+       if ((ret=(BN_GENCB *)OPENSSL_malloc(sizeof(BN_GENCB))) == NULL)
+               {
+               BNerr(BN_F_BN_GENCB_NEW,ERR_R_MALLOC_FAILURE);
+               return(NULL);
+               }
+
+       return ret;
+       }
+
+void BN_GENCB_free(BN_GENCB *cb)
+       {
+       if (cb == NULL) return;
+       OPENSSL_free(cb);
+       }
+
+void BN_set_flags(BIGNUM *b, int n)
+       {
+       b->flags|=n;
+       }
+
+int BN_get_flags(const BIGNUM *b, int n)
+       {
+       return b->flags&n;
+       }
+
+/* Populate a BN_GENCB structure with an "old"-style callback */
+void BN_GENCB_set_old(BN_GENCB *gencb, void (*callback)(int, int, void *), void *cb_arg)
+       {
+       BN_GENCB *tmp_gencb = gencb;
+       tmp_gencb->ver = 1;
+       tmp_gencb->arg = cb_arg;
+       tmp_gencb->cb.cb_1 = callback;
+       }
+
+/* Populate a BN_GENCB structure with a "new"-style callback */
+void BN_GENCB_set(BN_GENCB *gencb, int (*callback)(int, int, BN_GENCB *), void *cb_arg)
+       {
+       BN_GENCB *tmp_gencb = gencb;
+       tmp_gencb->ver = 2;
+       tmp_gencb->arg = cb_arg;
+       tmp_gencb->cb.cb_2 = callback;
+       }
+
+void *BN_GENCB_get_arg(BN_GENCB *cb)
+       {
+       return cb->arg;
+       }
+
+
+BIGNUM *bn_wexpand(BIGNUM *a, int words)
+       {
+       return (words <= a->dmax)?a:bn_expand2(a,words);
+       }
+
+void bn_correct_top(BIGNUM *a)
+       {
+       BN_ULONG *ftl;
+       int tmp_top = a->top;
+
+       if (tmp_top > 0)
+               {
+               for (ftl= &(a->d[tmp_top-1]); tmp_top > 0; tmp_top--)
+                       if (*(ftl--)) break;
+               a->top = tmp_top;
+               }
+       bn_pollute(a);
+       }