Some changes for bn_gf2m.c: better error checking plus some minor

optimizations.

Submitted by: Nils Larsch

diff --git a/crypto/bn/bn_gf2m.c b/crypto/bn/bn_gf2m.c
index 0bb4f9b2515f62a43c4d0e2ad74466df92c4d765..1cdad7473b464aafe3ffef5f63b7caa1ec73bea7 100644 (file)
--- a/crypto/bn/bn_gf2m.c
+++ b/crypto/bn/bn_gf2m.c
@@ -323,8 +323,12 @@ int BN_GF2m_mod_arr(BIGNUM *r, const BIGNUM *a, const unsigned int p[])
        int n, dN, d0, d1;
        BN_ULONG zz, *z;
        
-       /* Since the algorithm does reduction in the r value, if a != r, copy the
-        * contents of a into r so we can do reduction in r. 
+       if (!p[0])
+               /* reduction mod 1 => return 0 */
+               return BN_zero(r);
+
+       /* Since the algorithm does reduction in the r value, if a != r, copy
+        * the contents of a into r so we can do reduction in r. 
         */
        if (a != r)
                {
@@ -345,7 +349,7 @@ int BN_GF2m_mod_arr(BIGNUM *r, const BIGNUM *a, const unsigned int p[])
                if (z[j] == 0) { j--; continue; }
                z[j] = 0;
 
-               for (k = 1; p[k] > 0; k++)
+               for (k = 1; p[k] != 0; k++)
                        {
                        /* reducing component t^p[k] */
                        n = p[0] - p[k];
@@ -375,7 +379,7 @@ int BN_GF2m_mod_arr(BIGNUM *r, const BIGNUM *a, const unsigned int p[])
                if (d0) z[dN] = (z[dN] << d1) >> d1; /* clear up the top d1 bits */
                z[0] ^= zz; /* reduction t^0 component */
 
-               for (k = 1; p[k] > 0; k++)
+               for (k = 1; p[k] != 0; k++)
                        {
                        BN_ULONG tmp_ulong;
 
@@ -408,7 +412,8 @@ int BN_GF2m_mod(BIGNUM *r, const BIGNUM *a, const BIGNUM *p)
        const int max = BN_num_bits(p);
        unsigned int *arr=NULL, ret = 0;
        if ((arr = (unsigned int *)OPENSSL_malloc(sizeof(unsigned int) * max)) == NULL) goto err;
-       if (BN_GF2m_poly2arr(p, arr, max) > max)
+       ret = BN_GF2m_poly2arr(p, arr, max);
+       if (!ret || ret > max)
                {
                BNerr(BN_F_BN_GF2M_MOD,BN_R_INVALID_LENGTH);
                goto err;
@@ -459,9 +464,9 @@ int BN_GF2m_mod_mul_arr(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const unsig
                }
 
        bn_correct_top(s);
-       BN_GF2m_mod_arr(r, s, p);
+       if (BN_GF2m_mod_arr(r, s, p))
+               ret = 1;
        bn_check_top(r);
-       ret = 1;
 
   err:
        BN_CTX_end(ctx);
@@ -481,7 +486,8 @@ int BN_GF2m_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *p
        const int max = BN_num_bits(p);
        unsigned int *arr=NULL, ret = 0;
        if ((arr = (unsigned int *)OPENSSL_malloc(sizeof(unsigned int) * max)) == NULL) goto err;
-       if (BN_GF2m_poly2arr(p, arr, max) > max)
+       ret = BN_GF2m_poly2arr(p, arr, max);
+       if (!ret || ret > max)
                {
                BNerr(BN_F_BN_GF2M_MOD_MUL,BN_R_INVALID_LENGTH);
                goto err;
@@ -531,7 +537,8 @@ int BN_GF2m_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
        const int max = BN_num_bits(p);
        unsigned int *arr=NULL, ret = 0;
        if ((arr = (unsigned int *)OPENSSL_malloc(sizeof(unsigned int) * max)) == NULL) goto err;
-       if (BN_GF2m_poly2arr(p, arr, max) > max)
+       ret = BN_GF2m_poly2arr(p, arr, max);
+       if (!ret || ret > max)
                {
                BNerr(BN_F_BN_GF2M_MOD_SQR,BN_R_INVALID_LENGTH);
                goto err;
@@ -567,10 +574,6 @@ int BN_GF2m_mod_inv(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
        if (!BN_GF2m_mod(u, a, p)) goto err;
        if (!BN_copy(v, p)) goto err;
 
-       u->neg = 0; /* Need to set u->neg = 0 because BN_is_one(u) checks
-                    * the neg flag of the bignum.
-                    */
-
        if (BN_is_zero(u)) goto err;
 
        while (1)
@@ -585,7 +588,7 @@ int BN_GF2m_mod_inv(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
                        if (!BN_rshift1(b, b)) goto err;
                        }
 
-               if (BN_is_one(u)) break;
+               if (BN_abs_is_word(u, 1)) break;
 
                if (BN_num_bits(u) < BN_num_bits(v))
                        {
@@ -679,10 +682,6 @@ int BN_GF2m_mod_div(BIGNUM *r, const BIGNUM *y, const BIGNUM *x, const BIGNUM *p
        if (!BN_copy(b, p)) goto err;
        if (!BN_zero(v)) goto err;
        
-       a->neg = 0; /* Need to set a->neg = 0 because BN_is_one(a) checks
-                    * the neg flag of the bignum.
-                    */
-
        while (!BN_is_odd(a))
                {
                if (!BN_rshift1(a, a)) goto err;
@@ -703,7 +702,7 @@ int BN_GF2m_mod_div(BIGNUM *r, const BIGNUM *y, const BIGNUM *x, const BIGNUM *p
                                if (!BN_rshift1(v, v)) goto err;
                                } while (!BN_is_odd(b));
                        }
-               else if (BN_is_one(a))
+               else if (BN_abs_is_word(a, 1))
                        break;
                else
                        {
@@ -763,9 +762,10 @@ int        BN_GF2m_mod_exp_arr(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const unsig
        BIGNUM *u;
        
        if (BN_is_zero(b))
-               {
                return(BN_one(r));
-               }
+
+       if (BN_abs_is_word(b, 1))
+               return (BN_copy(r, a) != NULL);
        
 
        BN_CTX_start(ctx);
@@ -804,7 +804,8 @@ int BN_GF2m_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *p
        const int max = BN_num_bits(p);
        unsigned int *arr=NULL, ret = 0;
        if ((arr = (unsigned int *)OPENSSL_malloc(sizeof(unsigned int) * max)) == NULL) goto err;
-       if (BN_GF2m_poly2arr(p, arr, max) > max)
+       ret = BN_GF2m_poly2arr(p, arr, max);
+       if (!ret || ret > max)
                {
                BNerr(BN_F_BN_GF2M_MOD_EXP,BN_R_INVALID_LENGTH);
                goto err;
@@ -824,6 +825,10 @@ int        BN_GF2m_mod_sqrt_arr(BIGNUM *r, const BIGNUM *a, const unsigned int p[], BN_
        {
        int ret = 0;
        BIGNUM *u;
+
+       if (!p[0])
+               /* reduction mod 1 => return 0 */
+               return BN_zero(r);
        
        BN_CTX_start(ctx);
        if ((u = BN_CTX_get(ctx)) == NULL) goto err;
@@ -850,7 +855,8 @@ int BN_GF2m_mod_sqrt(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
        const int max = BN_num_bits(p);
        unsigned int *arr=NULL, ret = 0;
        if ((arr = (unsigned int *)OPENSSL_malloc(sizeof(unsigned int) * max)) == NULL) goto err;
-       if (BN_GF2m_poly2arr(p, arr, max) > max)
+       ret = BN_GF2m_poly2arr(p, arr, max);
+       if (!ret || ret > max)
                {
                BNerr(BN_F_BN_GF2M_MOD_EXP,BN_R_INVALID_LENGTH);
                goto err;
@@ -870,7 +876,11 @@ int BN_GF2m_mod_solve_quad_arr(BIGNUM *r, const BIGNUM *a_, const unsigned int p
        int ret = 0, count = 0;
        unsigned int j;
        BIGNUM *a, *z, *rho, *w, *w2, *tmp;
-       
+
+       if (!p[0])
+               /* reduction mod 1 => return 0 */
+               return BN_zero(r);
+
        BN_CTX_start(ctx);
        a = BN_CTX_get(ctx);
        z = BN_CTX_get(ctx);
@@ -951,7 +961,8 @@ int BN_GF2m_mod_solve_quad(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *
        const int max = BN_num_bits(p);
        unsigned int *arr=NULL, ret = 0;
        if ((arr = (unsigned int *)OPENSSL_malloc(sizeof(unsigned int) * max)) == NULL) goto err;
-       if (BN_GF2m_poly2arr(p, arr, max) > max)
+       ret = BN_GF2m_poly2arr(p, arr, max);
+       if (!ret || ret > max)
                {
                BNerr(BN_F_BN_GF2M_MOD_SOLVE_QUAD,BN_R_INVALID_LENGTH);
                goto err;
@@ -963,21 +974,28 @@ int BN_GF2m_mod_solve_quad(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *
        return ret;
        }
 
-/* Convert the bit-string representation of a polynomial a into an array
+/* Convert the bit-string representation of a polynomial
+ * ( \sum_{i=0}^n a_i * x^i , where a_0 is *not* zero) into an array
  * of integers corresponding to the bits with non-zero coefficient.
  * Up to max elements of the array will be filled.  Return value is total
  * number of coefficients that would be extracted if array was large enough.
  */
 int BN_GF2m_poly2arr(const BIGNUM *a, unsigned int p[], int max)
        {
-       int i, j, k;
+       int i, j, k = 0;
        BN_ULONG mask;
 
-       for (k = 0; k < max; k++) p[k] = 0;
-       k = 0;
+       if (BN_is_zero(a) || !BN_is_bit_set(a, 0))
+               /* a_0 == 0 => return error (the unsigned int array
+                * must be terminated by 0)
+                */
+               return 0;
 
        for (i = a->top - 1; i >= 0; i--)
                {
+               if (!a->d[i])
+                       /* skip word if a->d[i] == 0 */
+                       continue;
                mask = BN_TBIT;
                for (j = BN_BITS2 - 1; j >= 0; j--)
                        {
@@ -1001,7 +1019,7 @@ int BN_GF2m_arr2poly(const unsigned int p[], BIGNUM *a)
        int i;
 
        BN_zero(a);
-       for (i = 0; p[i] > 0; i++)
+       for (i = 0; p[i] != 0; i++)
                {
                BN_set_bit(a, p[i]);
                }