Changing security directory lookup to a prefix match rather than exac…

…t match.

rcl/src/rcl/node.c

@@ -101,6 +101,130 @@ const char * rcl_create_node_logger_name(
   return node_logger_name;
 }
 
+/// Return the directory whose name most closely matches node_name (longest-prefix match), scanning under base_dir.
+/**
+ * By using a prefix match, a node named e.g. "my_node_123" will be able to load and use the directory "my_node" if no better match exists.
+ * \param[in] base_dir
+ * \param[in] node_name
+ * \param[out] matched_name must be a valid memory address allocated with at least _TINYDIR_FILENAME_MAX characters.
+ * \return true if a match was found
+ */
+static bool get_best_matching_directory(
+  const char * base_dir,
+  const char * node_name,
+  char * matched_name)
+{
+  int max_match_length = 0;
+  tinydir_dir dir;
+  if (-1 == tinydir_open(&dir, base_dir)) {
+    return false;
+  }
+  while (dir.has_next) {
+    tinydir_file file;
+    if (-1 == tinydir_readfile(&dir, &file)) {
+      goto cleanup;
+    }
+    if (!file.is_dir) {
+      continue;
+    }
+    size_t matched_name_length = strnlen(file.name, sizeof(file.name) - 1);
+    if (0 == strncmp(file.name, node_name, matched_name_length) && matched_name_length > max_match_length) {
+      max_match_length = matched_name_length;
+      strncpy(matched_name, file.name, max_match_length);
+    }
+    if (-1 == tinydir_next(&dir)) {
+      goto cleanup;
+    }
+  }
+cleanup:
+  tinydir_close(&dir);
+  return max_match_length > 0;
+}
+
+/// Return the secure root directory associated with a node given its validated name and namespace.
+/**
+ * E.g. for a node named "c" in namespace "/a/b", the secure root path will be
+ * "a/b/c", where the delimiter "/" is native for target file system (e.g. "\\" for _WIN32).
+ * If no exact match is found for the node name, a best match would be used instead (by performing longest-prefix matching).
+ *
+ * However, this expansion can be overridden by setting the secure node directory environment
+ * variable, allowing users to explicitly specify the exact secure root directory to be utilized.
+ * Such an override is useful for where the FQN of a node is non-deterministic before runtime,
+ * or when testing and using additional tools that may not otherwise not be easily provisioned.
+ *
+ * \param[in] node_name validated node name (a single token)
+ * \param[in] node_namespace validated, absolute namespace (starting with "/")
+ * \param[in] allocator the allocator to use for allocation
+ * \returns machine specific (absolute) node secure root path or NULL on failure
+ */
+const char * rcl_get_secure_root(
+  const char * node_name,
+  const char * node_namespace,
+  const rcl_allocator_t * allocator)
+{
+  bool ros_secure_node_override = true;
+  const char * ros_secure_root_env = NULL;
+  if (NULL == node_name) {
+    return NULL;
+  }
+  if (rcutils_get_env(ROS_SECURITY_NODE_DIRECTORY_VAR_NAME, &ros_secure_root_env)) {
+    return NULL;
+  }
+  if (!ros_secure_root_env) {
+    return NULL;
+  }
+  size_t ros_secure_root_size = strlen(ros_secure_root_env);
+  if (!ros_secure_root_size) {
+    // check root directory if node directory environment variable is empty
+    if (rcutils_get_env(ROS_SECURITY_ROOT_DIRECTORY_VAR_NAME, &ros_secure_root_env)) {
+      return NULL;
+    }
+    if (!ros_secure_root_env) {
+      return NULL;
+    }
+    ros_secure_root_size = strlen(ros_secure_root_env);
+    if (!ros_secure_root_size) {
+      return NULL;  // environment variable was empty
+    } else {
+      ros_secure_node_override = false;
+    }
+  }
+
+  char * node_secure_root = NULL;
+  if (ros_secure_node_override) {
+    node_secure_root =
+      (char *)allocator->allocate(ros_secure_root_size + 1, allocator->state);
+    memcpy(node_secure_root, ros_secure_root_env, ros_secure_root_size + 1);
+    // TODO(ros2team): This make an assumption on the value and length of the root namespace.
+    // This should likely come from another (rcl/rmw?) function for reuse.
+    // If the namespace is the root namespace ("/"), the secure root is just the node name.
+  } else {
+    // Perform longest prefix match for the node's name in directory <root dir>/<namespace>.
+    char * base_lookup_dir = NULL;
+    if (strlen(node_namespace) == 1) {
+      base_lookup_dir = ros_secure_root_env;
+    } else {
+      char matched_dir[_TINYDIR_FILENAME_MAX] = {0};
+      // TODO(ros2team): remove the hard-coded length, use the length of the root namespace instead.
+      base_lookup_dir = rcutils_join_path(ros_secure_root_env, node_namespace + 1, *allocator);
+    }
+    if (get_best_matching_directory(base_lookup_dir, node_name, matched_dir)) {
+      node_secure_root = rcutils_join_path(base_lookup_dir, matched_dir, *allocator);
+    }
+    if (base_lookup_dir != ros_secure_root_env && NULL != base_lookup_dir) {
+      allocator->deallocate(base_lookup_dir, allocator->state);
+    }
+  }
+  // Check node_secure_root is not NULL before checking directory
+  if (NULL == node_secure_root) {
+    return NULL;
+  } else if (!rcutils_is_directory(node_secure_root)) {
+    allocator->deallocate(node_secure_root, allocator->state);
+    return NULL;
+  }
+  return node_secure_root;
+}
+
 rcl_node_t
 rcl_get_zero_initialized_node()
 {