Error checking and memory leak fixes in NISTZ256.

Reviewed-by: NRichard Levitte <levitte@openssl.org>

crypto/bn/bn_err.c

 /* crypto/bn/bn_err.c */
 /* ====================================================================
- * Copyright (c) 1999-2014 The OpenSSL Project.  All rights reserved.
+ * Copyright (c) 1999-2015 The OpenSSL Project.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -113,6 +113,7 @@ static ERR_STRING_DATA BN_str_functs[] = {
     {ERR_FUNC(BN_F_BN_NEW), "BN_new"},
     {ERR_FUNC(BN_F_BN_RAND), "BN_rand"},
     {ERR_FUNC(BN_F_BN_RAND_RANGE), "BN_rand_range"},
+    {ERR_FUNC(BN_F_BN_SET_WORDS), "bn_set_words"},
     {ERR_FUNC(BN_F_BN_USUB), "BN_usub"},
     {0, NULL}
 };

crypto/bn/bn_intern.c

@@ -233,11 +233,20 @@ void bn_set_static_words(BIGNUM *a, BN_ULONG *words, int size)
     a->dmax = a->top = size;
     a->neg = 0;
     a->flags |= BN_FLG_STATIC_DATA;
+    bn_correct_top(a);
 }
 
-void bn_set_data(BIGNUM *a, const void *data, size_t size)
+int bn_set_words(BIGNUM *a, BN_ULONG *words, int num_words)
 {
-    memcpy(a->d, data, size);
+    if (bn_wexpand(a, num_words) == NULL) {
+        BNerr(BN_F_BN_SET_WORDS, ERR_R_MALLOC_FAILURE);
+        return 0;
+    }
+
+    memcpy(a->d, words, sizeof(BN_ULONG) * num_words);
+    a->top = num_words;
+    bn_correct_top(a);
+    return 1;
 }
 
 size_t bn_sizeof_BIGNUM(void)

crypto/ec/ecp_nistz256.c

@@ -1133,6 +1133,7 @@ static int ecp_nistz256_points_mul(const EC_GROUP *group,
     const PRECOMP256_ROW *preComputedTable = NULL;
     const EC_PRE_COMP *pre_comp = NULL;
     const EC_POINT *generator = NULL;
+    BN_CTX *new_ctx = NULL;
     unsigned int idx = 0;
     const unsigned int window_size = 7;
     const unsigned int mask = (1 << (window_size + 1)) - 1;
@@ -1152,6 +1153,7 @@ static int ecp_nistz256_points_mul(const EC_GROUP *group,
         ECerr(EC_F_ECP_NISTZ256_POINTS_MUL, EC_R_INCOMPATIBLE_OBJECTS);
         return 0;
     }
+
     if ((scalar == NULL) && (num == 0))
         return EC_POINT_set_to_infinity(group, r);
 
@@ -1162,13 +1164,13 @@ static int ecp_nistz256_points_mul(const EC_GROUP *group,
         }
     }
 
-    /* Need 256 bits for space for all coordinates. */
-    bn_wexpand(r->X, P256_LIMBS);
-    bn_wexpand(r->Y, P256_LIMBS);
-    bn_wexpand(r->Z, P256_LIMBS);
-    bn_set_top(r->X, P256_LIMBS);
-    bn_set_top(r->Y, P256_LIMBS);
-    bn_set_top(r->Z, P256_LIMBS);
+    if (ctx == NULL) {
+        ctx = new_ctx = BN_CTX_new();
+        if (ctx == NULL)
+            goto err;
+    }
+
+    BN_CTX_start(ctx);
 
     if (scalar) {
         generator = EC_GROUP_get0_generator(group);
@@ -1194,8 +1196,10 @@ static int ecp_nistz256_points_mul(const EC_GROUP *group,
 
             if (!ecp_nistz256_set_from_affine(pre_comp_generator,
                                               group, pre_comp->precomp[0],
-                                              ctx))
+                                              ctx)) {
+                EC_POINT_free(pre_comp_generator);
                 goto err;
+            }
 
             if (0 == EC_POINT_cmp(group, generator, pre_comp_generator, ctx))
                 preComputedTable = (const PRECOMP256_ROW *)pre_comp->precomp;
@@ -1300,14 +1304,14 @@ static int ecp_nistz256_points_mul(const EC_GROUP *group,
         new_scalars = OPENSSL_malloc((num + 1) * sizeof(BIGNUM *));
         if (!new_scalars) {
             ECerr(EC_F_ECP_NISTZ256_POINTS_MUL, ERR_R_MALLOC_FAILURE);
-            return 0;
+            goto err;
         }
 
         new_points = OPENSSL_malloc((num + 1) * sizeof(EC_POINT *));
         if (!new_points) {
             OPENSSL_free(new_scalars);
             ECerr(EC_F_ECP_NISTZ256_POINTS_MUL, ERR_R_MALLOC_FAILURE);
-            return 0;
+            goto err;
         }
 
         memcpy(new_scalars, scalars, num * sizeof(BIGNUM *));
@@ -1336,18 +1340,20 @@ static int ecp_nistz256_points_mul(const EC_GROUP *group,
         OPENSSL_free(scalars);
     }
 
-    bn_set_data(r->X, p.p.X, sizeof(p.p.X));
-    bn_set_data(r->Y, p.p.Y, sizeof(p.p.Y));
-    bn_set_data(r->Z, p.p.Z, sizeof(p.p.Z));
     /* Not constant-time, but we're only operating on the public output. */
-    bn_correct_top(r->X);
-    bn_correct_top(r->Y);
-    bn_correct_top(r->Z);
+    if (!bn_set_words(r->X, p.p.X, P256_LIMBS) ||
+        !bn_set_words(r->Y, p.p.Y, P256_LIMBS) ||
+        !bn_set_words(r->Z, p.p.Z, P256_LIMBS)) {
+        goto err;
+    }
     r->Z_is_one = is_one(p.p.Z);
 
     ret = 1;
 
- err:
+err:
+    if (ctx)
+        BN_CTX_end(ctx);
+    BN_CTX_free(new_ctx);
     return ret;
 }
 
@@ -1360,6 +1366,7 @@ static int ecp_nistz256_get_affine(const EC_GROUP *group,
     BN_ULONG x_aff[P256_LIMBS];
     BN_ULONG y_aff[P256_LIMBS];
     BN_ULONG point_x[P256_LIMBS], point_y[P256_LIMBS], point_z[P256_LIMBS];
+    BN_ULONG x_ret[P256_LIMBS], y_ret[P256_LIMBS];
 
     if (EC_POINT_is_at_infinity(group, point)) {
         ECerr(EC_F_ECP_NISTZ256_GET_AFFINE, EC_R_POINT_AT_INFINITY);
@@ -1378,19 +1385,17 @@ static int ecp_nistz256_get_affine(const EC_GROUP *group,
     ecp_nistz256_mul_mont(x_aff, z_inv2, point_x);
 
     if (x != NULL) {
-        bn_wexpand(x, P256_LIMBS);
-        bn_set_top(x, P256_LIMBS);
-        ecp_nistz256_from_mont(bn_get_words(x), x_aff);
-        bn_correct_top(x);
+        ecp_nistz256_from_mont(x_ret, x_aff);
+        if (!bn_set_words(x, x_ret, P256_LIMBS))
+            return 0;
     }
 
     if (y != NULL) {
         ecp_nistz256_mul_mont(z_inv3, z_inv3, z_inv2);
         ecp_nistz256_mul_mont(y_aff, z_inv3, point_y);
-        bn_wexpand(y, P256_LIMBS);
-        bn_set_top(y, P256_LIMBS);
-        ecp_nistz256_from_mont(bn_get_words(y), y_aff);
-        bn_correct_top(y);
+        ecp_nistz256_from_mont(y_ret, y_aff);
+        if (!bn_set_words(y, y_ret, P256_LIMBS))
+            return 0;
     }
 
     return 1;

crypto/include/internal/bn_int.h

@@ -102,10 +102,15 @@ BN_ULONG *bn_get_words(const BIGNUM *a);
 void bn_set_static_words(BIGNUM *a, BN_ULONG *words, int size);
 
 /*
- * Copy data into the BIGNUM. The caller must check that dmax is sufficient to
- * hold the data
+ * Copy words into the BIGNUM |a|, reallocating space as necessary.
+ * The negative flag of |a| is not modified.
+ * Returns 1 on success and 0 on failure.
  */
-void bn_set_data(BIGNUM *a, const void *data, size_t size);
+/*
+ * |num_words| is int because bn_expand2 takes an int. This is an internal
+ * function so we simply trust callers not to pass negative values.
+ */
+int bn_set_words(BIGNUM *a, BN_ULONG *words, int num_words);
 
 size_t bn_sizeof_BIGNUM(void);
 

include/openssl/bn.h

@@ -730,6 +730,7 @@ void ERR_load_BN_strings(void);
 # define BN_F_BN_NEW                                      113
 # define BN_F_BN_RAND                                     114
 # define BN_F_BN_RAND_RANGE                               122
+# define BN_F_BN_SET_WORDS                                144
 # define BN_F_BN_USUB                                     115
 
 /* Reason codes. */