permission: fix parent directory over-grant in fs radix tree

Author: Nashit-h

src/permission/fs_permission.cc

@@ -304,7 +304,11 @@ bool FSPermission::RadixTree::Lookup(const std::string_view& s,
 
     auto node = current_node->NextNode(path, parent_node_prefix_len);
     if (node == nullptr) {
-      return false;
+      // The whole path matched this node. Grant it when the directory itself
+      // was allowed through a trailing wildcard ("/dir/*"), which after a
+      // radix split lives on a descendant rather than on this node.
+      return parent_node_prefix_len == path_len &&
+             current_node->HasWildcardGrantForSelf();
     }
 
     current_node = node;

src/permission/fs_permission.h

@@ -68,7 +68,13 @@ class FSPermission final : public PermissionBase {
             return split_child->CreateChild(path_prefix.substr(i));
           }
         }
-        child->is_leaf = true;
+        // Only mark the child as a leaf when it already terminates an
+        // inserted path. Routing a longer path through this node must not
+        // turn a pass-through prefix into a granted entry, or an unrelated
+        // parent directory would be treated as allowed.
+        if (child->IsEndNode()) {
+          child->is_leaf = true;
+        }
         return child->CreateChild(path_prefix.substr(i));
       }
 
@@ -137,6 +143,31 @@ class FSPermission final : public PermissionBase {
         }
         return is_leaf;
       }
+
+      // A directory allowed with a trailing wildcard ("/dir/*") also grants
+      // access to the directory itself. After a radix split that grant is
+      // stored as a "/" + "*" descendant of this node rather than on the
+      // node, so look for it explicitly.
+      bool HasWildcardGrantForSelf() const {
+        const char pattern[2] = {node::kPathSeparator, '*'};
+        size_t matched = 0;
+        const Node* current = this;
+        while (matched < 2) {
+          auto it = current->children.find(pattern[matched]);
+          if (it == current->children.end()) {
+            return false;
+          }
+          const Node* child = it->second;
+          for (size_t i = 0; i < child->prefix.length(); ++i) {
+            if (matched >= 2 || child->prefix[i] != pattern[matched]) {
+              return false;
+            }
+            ++matched;
+          }
+          current = child;
+        }
+        return current->wildcard_child != nullptr;
+      }
     };
 
     RadixTree();

test/parallel/test-permission-fs-wildcard.js

@@ -126,3 +126,31 @@ if (common.isWindows) {
     assert.strictEqual(status, 0, stderr.toString());
   }
 }
+
+{
+  // A trailing-wildcard grant for a subdirectory must not leak access to an
+  // unrelated parent directory that only shares a path prefix with sibling
+  // grants. The directory that owns the wildcard stays accessible.
+  if (!common.isWindows) {
+    const { status, stderr } = spawnSync(
+      process.execPath,
+      [
+        '--permission',
+        '--allow-fs-read=/etc/app/logs/*',
+        '--allow-fs-read=/etcd/data/file',
+        '--allow-fs-read=/etcx/y',
+        '-e',
+        `
+        const assert = require('assert')
+        assert.ok(!process.permission.has('fs.read', '/etc'));
+        assert.ok(!process.permission.has('fs.read', '/etc/passwd'));
+        assert.ok(process.permission.has('fs.read', '/etc/app/logs'));
+        assert.ok(process.permission.has('fs.read', '/etc/app/logs/app.log'));
+        assert.ok(process.permission.has('fs.read', '/etcd/data/file'));
+        assert.ok(process.permission.has('fs.read', '/etcx/y'));
+      `,
+      ]
+    );
+    assert.strictEqual(status, 0, stderr.toString());
+  }
+}