Fix issue found by addrss sanitizer

If an attribute had an empty value (which is apparently possible with
some tokens), the copy function would fail to initialize the pointer
causing an invalid free when the attributes array is freed.

Ensure pValue is zeroed on copy if the attri bute length is 0, and
also ensure the attribute length is correctly set to 0.

Then belt&suspender approach ensure the buffer is allocated with
OPENSSL_zalloc instead of OPENSSL_malloc, which will eansure by default
all addresses and legth are a safe default NULL/0 value.

Signed-off-by: Simo Sorce <simo@redhat.com>

src/objects.c

@@ -2762,7 +2762,7 @@ static CK_RV return_dup_key(P11PROV_OBJ *dst, P11PROV_OBJ *src)
     dst->cka_token = src->cka_token;
     dst->data.key = src->data.key;
 
-    dst->attrs = OPENSSL_malloc(sizeof(CK_ATTRIBUTE) * src->numattrs);
+    dst->attrs = OPENSSL_zalloc(sizeof(CK_ATTRIBUTE) * src->numattrs);
     if (!dst->attrs) {
         rv = CKR_HOST_MEMORY;
         P11PROV_raise(dst->ctx, rv, "Failed allocation");

src/util.c

@@ -1016,8 +1016,10 @@ CK_RV p11prov_copy_attr(CK_ATTRIBUTE *dst, CK_ATTRIBUTE *src)
             return CKR_HOST_MEMORY;
         }
         memcpy(dst->pValue, src->pValue, src->ulValueLen);
-        dst->ulValueLen = src->ulValueLen;
+    } else {
+        dst->pValue = NULL;
     }
+    dst->ulValueLen = src->ulValueLen;
     dst->type = src->type;
 
     return CKR_OK;