BN_CTX_get() can fail - consistently check its return value.

There are currently cases where the return from each call is checked,
the return from only the last call is checked and cases where it is not
checked at all (including code in bn, ec and engine).

Checking the last return value is valid as once the function fails it will
continue to return NULL. However, in order to be consistent check each
call with the same idiom. This makes it easy to verify.

Note there are still a handful of cases that do not follow the idiom -
these will be handled separately.

ok beck@ doug@

1 files changed, 32 insertions, 24 deletions

diff --git a/src/lib/libcrypto/ec/ec2_smpl.c b/src/lib/libcrypto/ec/ec2_smpl.c
index b9c066c5c1..43f0afd5ae 100644
--- a/src/lib/libcrypto/ec/ec2_smpl.c
+++ b/src/lib/libcrypto/ec/ec2_smpl.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ec2_smpl.c,v 1.13 2015/02/08 22:25:03 miod Exp $ */
+/* $OpenBSD: ec2_smpl.c,v 1.14 2015/02/09 15:49:22 jsing Exp $ */
 /* ====================================================================
  * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
  *
@@ -291,8 +291,7 @@ ec_GF2m_simple_group_check_discriminant(const EC_GROUP * group, BN_CTX * ctx)
                 }
         }
         BN_CTX_start(ctx);
-        b = BN_CTX_get(ctx);
-        if (b == NULL)
+        if ((b = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (!BN_GF2m_mod_arr(b, &group->b, group->poly))
@@ -464,15 +463,21 @@ ec_GF2m_simple_add(const EC_GROUP *group, EC_POINT *r, const EC_POINT *a,
                         return 0;
         }
         BN_CTX_start(ctx);
-        x0 = BN_CTX_get(ctx);
-        y0 = BN_CTX_get(ctx);
-        x1 = BN_CTX_get(ctx);
-        y1 = BN_CTX_get(ctx);
-        x2 = BN_CTX_get(ctx);
-        y2 = BN_CTX_get(ctx);
-        s = BN_CTX_get(ctx);
-        t = BN_CTX_get(ctx);
-        if (t == NULL)
+        if ((x0 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((y0 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((x1 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((y1 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((x2 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((y2 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((s = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((t = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (a->Z_is_one) {
@@ -611,9 +616,9 @@ ec_GF2m_simple_is_on_curve(const EC_GROUP *group, const EC_POINT *point, BN_CTX
                         return -1;
         }
         BN_CTX_start(ctx);
-        y2 = BN_CTX_get(ctx);
-        lh = BN_CTX_get(ctx);
-        if (lh == NULL)
+        if ((y2 = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((lh = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         /*
@@ -651,7 +656,8 @@ err:
  *   1   not equal
  */
 int 
-ec_GF2m_simple_cmp(const EC_GROUP * group, const EC_POINT * a, const EC_POINT * b, BN_CTX * ctx)
+ec_GF2m_simple_cmp(const EC_GROUP *group, const EC_POINT *a,
+    const EC_POINT *b, BN_CTX *ctx)
 {
         BIGNUM *aX, *aY, *bX, *bY;
         BN_CTX *new_ctx = NULL;
@@ -672,11 +678,13 @@ ec_GF2m_simple_cmp(const EC_GROUP * group, const EC_POINT * a, const EC_POINT *
                         return -1;
         }
         BN_CTX_start(ctx);
-        aX = BN_CTX_get(ctx);
-        aY = BN_CTX_get(ctx);
-        bX = BN_CTX_get(ctx);
-        bY = BN_CTX_get(ctx);
-        if (bY == NULL)
+        if ((aX = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((aY = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((bX = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((bY = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (!EC_POINT_get_affine_coordinates_GF2m(group, a, aX, aY, ctx))
@@ -710,9 +718,9 @@ ec_GF2m_simple_make_affine(const EC_GROUP * group, EC_POINT * point, BN_CTX * ct
                         return 0;
         }
         BN_CTX_start(ctx);
-        x = BN_CTX_get(ctx);
-        y = BN_CTX_get(ctx);
-        if (y == NULL)
+        if ((x = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((y = BN_CTX_get(ctx)) == NULL)
                 goto err;
 
         if (!EC_POINT_get_affine_coordinates_GF2m(group, point, x, y, ctx))