Check return value of some BN functions.

Factorise multiple bn_get_top(group->field) calls
Add missing checks on some conditional BN_copy return value
Add missing checks on some BN_copy return value
Add missing checks on a few bn_wexpand return value

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1626)
(cherry picked from commit 78e09b53a40729f5e99829ccc733b592bd22fea1)

6 files changed, 24 insertions, 17 deletions

diff --git a/crypto/bn/bn_exp.c b/crypto/bn/bn_exp.c
index 1670f01d1d..195a7867a4 100644
--- a/crypto/bn/bn_exp.c
+++ b/crypto/bn/bn_exp.c
@@ -180,8 +180,9 @@ int BN_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p, BN_CTX *ctx)
                 goto err;
         }
     }
-    if (r != rr)
-        BN_copy(r, rr);
+    if (r != rr && BN_copy(r, rr) == NULL)
+        goto err;
+
     ret = 1;
  err:
     BN_CTX_end(ctx);
diff --git a/crypto/bn/bn_mul.c b/crypto/bn/bn_mul.c
index b174850b6b..3c618dc307 100644
--- a/crypto/bn/bn_mul.c
+++ b/crypto/bn/bn_mul.c
@@ -1083,8 +1083,9 @@ int BN_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
  end:
 #endif
     bn_correct_top(rr);
-    if (r != rr)
-        BN_copy(r, rr);
+    if (r != rr && BN_copy(r, rr) == NULL)
+        goto err;
+
     ret = 1;
  err:
     bn_check_top(r);
diff --git a/crypto/bn/bn_prime.c b/crypto/bn/bn_prime.c
index 1d256874c9..8177fd2947 100644
--- a/crypto/bn/bn_prime.c
+++ b/crypto/bn/bn_prime.c
@@ -283,7 +283,8 @@ int BN_is_prime_fasttest_ex(const BIGNUM *a, int checks, BN_CTX *ctx_passed,
         BIGNUM *t;
         if ((t = BN_CTX_get(ctx)) == NULL)
             goto err;
-        BN_copy(t, a);
+        if (BN_copy(t, a) == NULL)
+            goto err;
         t->neg = 0;
         A = t;
     } else
diff --git a/crypto/bn/bn_sqr.c b/crypto/bn/bn_sqr.c
index 3ca69879ee..256d26e8db 100644
--- a/crypto/bn/bn_sqr.c
+++ b/crypto/bn/bn_sqr.c
@@ -143,8 +143,9 @@ int BN_sqr(BIGNUM *r, const BIGNUM *a, BN_CTX *ctx)
         rr->top = max - 1;
     else
         rr->top = max;
-    if (rr != r)
-        BN_copy(r, rr);
+    if (r != rr && BN_copy(r, rr) == NULL)
+        goto err;
+
     ret = 1;
  err:
     bn_check_top(rr);
diff --git a/crypto/ec/ec2_mult.c b/crypto/ec/ec2_mult.c
index 68cc8771d5..1f9cc00aea 100644
--- a/crypto/ec/ec2_mult.c
+++ b/crypto/ec/ec2_mult.c
@@ -267,7 +267,7 @@ static int ec_GF2m_montgomery_point_multiply(const EC_GROUP *group,
                                              BN_CTX *ctx)
 {
     BIGNUM *x1, *x2, *z1, *z2;
-    int ret = 0, i;
+    int ret = 0, i, group_top;
     BN_ULONG mask, word;
 
     if (r == point) {
@@ -297,10 +297,12 @@ static int ec_GF2m_montgomery_point_multiply(const EC_GROUP *group,
     x2 = &r->X;
     z2 = &r->Y;
 
-    bn_wexpand(x1, group->field.top);
-    bn_wexpand(z1, group->field.top);
-    bn_wexpand(x2, group->field.top);
-    bn_wexpand(z2, group->field.top);
+    group_top = group->field.top;
+    if (bn_wexpand(x1, group_top) == NULL
+        || bn_wexpand(z1, group_top) == NULL
+        || bn_wexpand(x2, group_top) == NULL
+        || bn_wexpand(z2, group_top) == NULL)
+        goto err;
 
     if (!BN_GF2m_mod_arr(x1, &point->X, group->poly))
         goto err;               /* x1 = x */
@@ -329,14 +331,14 @@ static int ec_GF2m_montgomery_point_multiply(const EC_GROUP *group,
     for (; i >= 0; i--) {
         word = scalar->d[i];
         while (mask) {
-            BN_consttime_swap(word & mask, x1, x2, group->field.top);
-            BN_consttime_swap(word & mask, z1, z2, group->field.top);
+            BN_consttime_swap(word & mask, x1, x2, group_top);
+            BN_consttime_swap(word & mask, z1, z2, group_top);
             if (!gf2m_Madd(group, &point->X, x2, z2, x1, z1, ctx))
                 goto err;
             if (!gf2m_Mdouble(group, x1, z1, ctx))
                 goto err;
-            BN_consttime_swap(word & mask, x1, x2, group->field.top);
-            BN_consttime_swap(word & mask, z1, z2, group->field.top);
+            BN_consttime_swap(word & mask, x1, x2, group_top);
+            BN_consttime_swap(word & mask, z1, z2, group_top);
             mask >>= 1;
         }
         mask = BN_TBIT;
diff --git a/crypto/rsa/rsa_gen.c b/crypto/rsa/rsa_gen.c
index 7f7dca39fd..082c8da2ef 100644
--- a/crypto/rsa/rsa_gen.c
+++ b/crypto/rsa/rsa_gen.c
@@ -142,7 +142,8 @@ static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value,
     if (!rsa->iqmp && ((rsa->iqmp = BN_new()) == NULL))
         goto err;
 
-    BN_copy(rsa->e, e_value);
+    if (BN_copy(rsa->e, e_value) == NULL)
+        goto err;
 
     /* generate p and q */
     for (;;) {