add query to detect accidential leak of private files

javascript/ql/src/Security/CWE-200/PrivateFileExposure.qhelp

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+<!DOCTYPE qhelp PUBLIC
+"-//Semmle//qhelp//EN"
+"qhelp.dtd">
+<qhelp>
+
+<overview>
+  <p>
+    Placeholder
+  </p>
+</overview>
+
+<recommendation>
+  <p>
+    Placeholder
+  </p>
+</recommendation>
+
+<example>
+  <p>
+    Placeholder
+  </p>
+</example>
+
+<references>
+  <li>OWASP: <a href="https://www.owasp.org/index.php/Top_10-2017_A3-Sensitive_Data_Exposure">Sensitive Data Exposure</a>.</li>
+</references>
+</qhelp>

javascript/ql/src/Security/CWE-200/PrivateFileExposure.ql

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+/**
+ * @name Exposure of private files
+ * @description Exposing a node_modules folder, or the project folder to the public, can cause exposure
+ *              of private information.
+ * @kind problem
+ * @problem.severity warning
+ * @id js/exposure-of-private-files
+ * @tags security
+ *       external/cwe/cwe-200
+ * @precision high
+ */
+
+import javascript
+
+/**
+ * Holds if `folder` is a node_modules folder, and at most 1 subdirectory down.
+ */
+bindingset[folder]
+predicate isNodeModuleFolder(string folder) {
+  folder.regexpMatch("(\\.?\\.?/)*node_modules(/|(/[a-zA-Z@_-]+/?))?")
+}
+
+/**
+ * Get a data-flow node that represents a path to the node_modules folder represented by the string-literal `path`.
+ */
+DataFlow::Node getANodeModulePath(string path) {
+  result.getStringValue() = path and
+  isNodeModuleFolder(path)
+  or
+  exists(DataFlow::CallNode resolve |
+    resolve = DataFlow::moduleMember("path", ["resolve", "join"]).getACall()
+  |
+    result = resolve and
+    resolve.getLastArgument() = getANodeModulePath(path)
+  )
+  or
+  exists(StringOps::ConcatenationRoot root | root = result |
+    root.getLastLeaf() = getANodeModulePath(path)
+  )
+  or
+  result.getAPredecessor() = getANodeModulePath(path) // local data-flow
+  or
+  exists(string base, string folder |
+    path = base + folder and
+    folder.regexpMatch("(/)?[a-zA-Z@_-]+/?") and
+    base.regexpMatch("(\\.?\\.?/)*node_modules(/)?") // node_modules, without any sub-folders.
+  |
+    exists(StringOps::ConcatenationRoot root | root = result |
+      root.getNumOperand() = 2 and
+      root.getFirstLeaf() = getANodeModulePath(base) and
+      root.getLastLeaf().getStringValue() = folder
+    )
+    or
+    exists(DataFlow::CallNode resolve |
+      resolve = DataFlow::moduleMember("path", ["resolve", "join"]).getACall()
+    |
+      result = resolve and
+      resolve.getNumArgument() = 2 and
+      resolve.getArgument(0) = getANodeModulePath(path) and
+      resolve.getArgument(1).mayHaveStringValue(folder)
+    )
+  )
+}
+
+/**
+ * Gets a folder that contains a `package.json` file.
+ */
+pragma[noinline]
+Folder getAPackageJSONFolder() { result = any(PackageJSON json).getFile().getParentContainer() }
+
+/**
+ * Gets a reference to `dirname` that might cause information to be leaked.
+ * That can happen if there is a `package.json` file in the same folder.
+ * (It is assumed that the presence of a `package.json` file means that a `node_modules` folder can also exist.
+ */
+DataFlow::Node dirname() {
+  exists(ModuleScope ms | result.asExpr() = ms.getVariable("__dirname").getAnAccess()) and
+  result.getFile().getParentContainer() = getAPackageJSONFolder()
+  or
+  result.getAPredecessor() = dirname()
+  or
+  exists(StringOps::ConcatenationRoot root | root = result |
+    root.getNumOperand() = 2 and
+    root.getOperand(0) = dirname() and
+    root.getOperand(1).getStringValue() = "/"
+  )
+}
+
+/**
+ * Gets a data-flow node that represents a path to the private folder `path`.
+ */
+DataFlow::Node getAPrivateFolderPath(string description) {
+  exists(string path |
+    result = getANodeModulePath(path) and description = "the folder \"" + path + "\""
+  )
+  or
+  result = dirname() and
+  description = "the folder " + result.getFile().getParentContainer().getRelativePath()
+  or
+  result.getStringValue() = [".", "./"] and
+  description = "the current working folder"
+}
+
+/**
+ * Gest a call that serves the folder `path` to the public.
+ */
+DataFlow::CallNode servesAPrivateFolder(string description) {
+  result = DataFlow::moduleMember("express", "static").getACall() and
+  result.getArgument(0) = getAPrivateFolderPath(description)
+}
+
+from Express::RouteSetup setup, string path
+where
+  setup.isUseCall() and
+  setup.getArgument([0 .. 1]) = servesAPrivateFolder(path).getEnclosingExpr()
+select setup, "Serves " + path + ", which can contain private information."

javascript/ql/test/query-tests/Security/CWE-200/PrivateFileExposure.expected

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+| lib/tst.js:7:1:7:45 | app.use ... rname)) | Serves the folder query-tests/Security/CWE-200/lib, which can contain private information. |
+| lib/tst.js:9:1:9:43 | app.use ... otDir)) | Serves the folder query-tests/Security/CWE-200/lib, which can contain private information. |
+| lib/tst.js:11:1:11:52 | app.use ... + '/')) | Serves the folder query-tests/Security/CWE-200/lib, which can contain private information. |
+| private-file-exposure.js:8:1:8:49 | app.use ... ular')) | Serves the folder "./node_modules/angular", which can contain private information. |
+| private-file-exposure.js:9:1:9:59 | app.use ... ular')) | Serves the folder "node_modules/angular", which can contain private information. |
+| private-file-exposure.js:10:1:10:67 | app.use ... mate')) | Serves the folder "node_modules/angular-animate", which can contain private information. |
+| private-file-exposure.js:11:1:11:67 | app.use ... ular')) | Serves the folder "/node_modules/angular", which can contain private information. |
+| private-file-exposure.js:12:1:12:78 | app.use ... ute/')) | Serves the folder "/node_modules/angular-route/", which can contain private information. |
+| private-file-exposure.js:13:1:13:48 | app.use ... ular')) | Serves the folder "/node_modules/angular", which can contain private information. |
+| private-file-exposure.js:14:1:14:84 | app.use ... les'))) | Serves the folder "../node_modules", which can contain private information. |
+| private-file-exposure.js:15:1:15:35 | app.use ... ('./')) | Serves the current working folder, which can contain private information. |
+| private-file-exposure.js:16:1:16:67 | app.use ... lar/')) | Serves the folder "./node_modules/angular/", which can contain private information. |
+| private-file-exposure.js:17:1:17:78 | app.use ... ar/'))) | Serves the folder "./node_modules/angular/", which can contain private information. |
+| private-file-exposure.js:18:1:18:74 | app.use ... les"))) | Serves the folder "/node_modules", which can contain private information. |
+| private-file-exposure.js:19:1:19:88 | app.use ... lar/')) | Serves the folder "/node_modules/angular/", which can contain private information. |
+| private-file-exposure.js:22:1:22:58 | app.use ... lar/')) | Serves the folder "/node_modules/angular/", which can contain private information. |

javascript/ql/test/query-tests/Security/CWE-200/PrivateFileExposure.qlref

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+Security/CWE-200/PrivateFileExposure.ql

javascript/ql/test/query-tests/Security/CWE-200/lib/package.json

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+{
+    "name": "foo",
+    "dependencies": {
+        "async": "3.2.0"
+    }
+}

javascript/ql/test/query-tests/Security/CWE-200/lib/tst.js

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+
+var express = require('express');
+var path = require("path");
+
+var app = express();
+
+app.use('basedir', express.static(__dirname)); // BAD
+const rootDir = __dirname;
+app.use('basedir', express.static(rootDir)); // BAD
+
+app.use('/monthly', express.static(__dirname + '/')); // BAD

javascript/ql/test/query-tests/Security/CWE-200/private-file-exposure.js

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+
+var express = require('express');
+var path = require("path");
+
+var app = express();
+
+// Not good. 
+app.use(express.static('./node_modules/angular'));
+app.use('/angular', express.static('node_modules/angular'));
+app.use('/animate', express.static('node_modules/angular-animate'));
+app.use('/js', express.static(__dirname + '/node_modules/angular'));
+app.use('/router', express.static(__dirname + '/node_modules/angular-route/'));
+app.use(express.static('/node_modules/angular'));
+app.use('/node_modules', express.static(path.resolve(__dirname, '../node_modules')));
+app.use('/js',express.static('./'));
+app.use('/angular', express.static("./node_modules" + '/angular/'));
+app.use('/angular', express.static(path.join("./node_modules" + '/angular/')));
+app.use('/angular', express.static(path.join(__dirname, "/node_modules")));
+app.use('/angular', express.static(path.join(__dirname, "/node_modules") + '/angular/'));
+const rootDir = __dirname;
+const nodeDir = path.join(rootDir + "/node_modules");
+app.use('/angular', express.static(nodeDir + '/angular/'));
+
+
+// Good
+app.use(express.static('./node_modules/jquery/dist'));
+app.use(express.static('./node_modules/bootstrap/dist'));
+app.use('/js', express.static(__dirname + '/node_modules/html5sortable/dist'));
+app.use('/css', express.static(__dirname + '/css'));
+app.use('/favicon.ico', express.static(__dirname + '/favicon.ico'));
+app.use(express.static(__dirname + "/static"));
+app.use(express.static(__dirname + "/static/js"));
+app.use('/docs/api', express.static('docs/api'));
+app.use('/js/', express.static('node_modules/bootstrap/dist/js'))
+app.use('/css/', express.static('node_modules/font-awesome/css'));
+app.use('basedir', express.static(__dirname)); // GOOD, because there is no package.json in the same folder.
+app.use('/monthly', express.static(__dirname + '/')); // GOOD, because there is no package.json in the same folder.