JS: Add Permissive CORS query (CWE-942)

javascript/ql/src/change-notes/2023-11-27-cors-permissive-configuarion.md

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+---
+category: minorAnalysis
+---
+* Added a new experimental query, `js/cors-misconfiguration`, which detects misconfigured CORS HTTP headers in the `cors` and `apollo` libraries. 

javascript/ql/src/experimental/Security/CWE-942/Apollo.qll

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+/**
+ * Provides classes for working with Apollo GraphQL connectors.
+ */
+
+import javascript
+
+/** Provides classes modeling the apollo packages [@apollo/server](https://npmjs.com/package/@apollo/server`) */
+module Apollo {
+  /** Get a reference to the `ApolloServer` class. */
+  private API::Node apollo() {
+    result =
+      API::moduleImport([
+          "@apollo/server", "@apollo/apollo-server-express", "@apollo/apollo-server-core",
+          "apollo-server", "apollo-server-express"
+        ]).getMember("ApolloServer")
+  }
+
+  /** Gets a reference to the `gql` function that parses GraphQL strings. */
+  private API::Node gql() {
+    result =
+      API::moduleImport([
+          "@apollo/server", "@apollo/apollo-server-express", "@apollo/apollo-server-core",
+          "apollo-server", "apollo-server-express"
+        ]).getMember("gql")
+  }
+
+  /** An instantiation of an `ApolloServer`. */
+  class ApolloServer extends API::NewNode {
+    ApolloServer() { this = apollo().getAnInstantiation() }
+  }
+
+  /** A string that is interpreted as a GraphQL query by a `apollo` package. */
+  private class ApolloGraphQLString extends GraphQL::GraphQLString {
+    ApolloGraphQLString() { this = gql().getACall().getArgument(0) }
+  }
+}

javascript/ql/src/experimental/Security/CWE-942/Cors.qll

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+/**
+ * Provides classes for working with Cors connectors.
+ */
+
+import javascript
+
+/** Provides classes modeling the [cors](https://npmjs.com/package/cors) library. */
+module Cors {
+  /**
+   * An expression that creates a new CORS configuration.
+   */
+  class Cors extends DataFlow::CallNode {
+    Cors() { this = DataFlow::moduleImport("cors").getAnInvocation() }
+
+    /** Get the options used to configure Cors */
+    DataFlow::Node getOptionsArgument() { result = this.getArgument(0) }
+
+    /** Holds if cors is using default configuration */
+    predicate isDefault() { this.getNumArgument() = 0 }
+
+    /** Gets the value of the `origin` option used to configure this Cors instance. */
+    DataFlow::Node getOrigin() { result = this.getOptionArgument(0, "origin") }
+  }
+}

javascript/ql/src/experimental/Security/CWE-942/CorsPermissiveConfiguration.qhelp

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+<!DOCTYPE qhelp PUBLIC
+"-//Semmle//qhelp//EN"
+"qhelp.dtd">
+<qhelp>
+
+<overview>
+	<p>
+
+		A server can use <code>CORS</code> (Cross-Origin Resource Sharing) to relax the 
+        restrictions imposed by the <code>SOP</code> (Same-Origin Policy), allowing controlled, secure
+        cross-origin requests when necessary. 
+
+        A server with an overly permissive <code>CORS</code> configuration may inadvertently 
+        expose sensitive data or lead to <code>CSRF</code> which is an attack that allows attackers to trick
+        users into performing unwanted operations in websites they're authenticated to.
+
+	</p>
+
+</overview>
+
+<recommendation>
+	<p>
+
+		When the <code>origin</code> is set to <code>true</code>, it signifies that the server 
+        is accepting requests from <code>any</code> origin, potentially exposing the system to 
+        CSRF attacks. This can be fixed using <code>false</code> as origin value or using a whitelist.
+
+	</p>
+	<p>
+
+		On the other hand, if the <code>origin</code> is 
+        set to <code>null</code>, it can be exploited by an attacker to deceive a user into making 
+        requests from a <code>null</code> origin form, often hosted within a sandboxed iframe.
+
+	</p>
+
+    <p>
+
+		If the <code>origin</code> value is user controlled, make sure that the data
+        is properly sanitized.
+
+	</p>
+</recommendation>
+
+<example>
+	<p>
+
+		In the example below, the <code>server_1</code> accepts requests from any origin
+        since the value of <code>origin</code> is set to <code>true</code>. 
+		And <code>server_2</code>'s origin is user-controlled.
+
+	</p>
+
+	<sample src="examples/CorsPermissiveConfigurationBad.js"/>
+
+	<p>
+
+		In the example below, the <code>server_1</code> CORS is restrictive so it's not
+		vulnerable to CSRF attacks. And <code>server_2</code>'s is using properly sanitized
+		user-controlled data.
+
+	</p>
+
+	<sample src="examples/CorsPermissiveConfigurationGood.js"/>
+</example>
+
+<references>
+	<li>Mozilla Developer Network: <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Origin">CORS, Access-Control-Allow-Origin</a>.</li>
+	<li>W3C: <a href="https://w3c.github.io/webappsec-cors-for-developers/#resources">CORS for developers, Advice for Resource Owners</a></li>
+</references>
+</qhelp>

javascript/ql/src/experimental/Security/CWE-942/CorsPermissiveConfiguration.ql

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+/**
+ * @name overly CORS configuration
+ * @description Misconfiguration of CORS HTTP headers allows CSRF attacks.
+ * @kind path-problem
+ * @problem.severity error
+ * @security-severity 7.5
+ * @precision high
+ * @id js/cors-misconfiguration
+ * @tags security
+ *       external/cwe/cwe-942
+ */
+
+import javascript
+import CorsPermissiveConfigurationQuery
+import DataFlow::PathGraph
+
+from Configuration cfg, DataFlow::PathNode source, DataFlow::PathNode sink
+where cfg.hasFlowPath(source, sink)
+select sink.getNode(), source, sink, "CORS Origin misconfiguration due to a $@.", source.getNode(),
+  "too permissive or user controlled value"

javascript/ql/src/experimental/Security/CWE-942/CorsPermissiveConfigurationCustomizations.qll

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+/**
+ * Provides default sources, sinks and sanitizers for reasoning about
+ * overly permissive CORS configurations, as well as
+ * extension points for adding your own.
+ */
+
+import javascript
+import Cors::Cors
+import Apollo::Apollo
+
+/** Module containing sources, sinks, and sanitizers for overly permissive CORS configurations. */
+module CorsPermissiveConfiguration {
+  /**
+   * A data flow source for permissive CORS configuration.
+   */
+  abstract class Source extends DataFlow::Node { }
+
+  /**
+   * A data flow sink for permissive CORS configuration.
+   */
+  abstract class Sink extends DataFlow::Node { }
+
+  /**
+   * A sanitizer for permissive CORS configuration.
+   */
+  abstract class Sanitizer extends DataFlow::Node { }
+
+  /** A source of remote user input, considered as a flow source for CORS misconfiguration. */
+  class RemoteFlowSourceAsSource extends Source instanceof RemoteFlowSource {
+    RemoteFlowSourceAsSource() { not this instanceof ClientSideRemoteFlowSource }
+  }
+
+  /** A flow label representing `true` and `null` values. */
+  abstract class TrueAndNull extends DataFlow::FlowLabel {
+    TrueAndNull() { this = "TrueAndNull" }
+  }
+
+  TrueAndNull truenullLabel() { any() }
+
+  /** A flow label representing `*` value. */
+  abstract class Wildcard extends DataFlow::FlowLabel {
+    Wildcard() { this = "Wildcard" }
+  }
+
+  Wildcard wildcardLabel() { any() }
+
+  /** An overly permissive value for `origin` (Apollo) */
+  class TrueNullValue extends Source {
+    TrueNullValue() { this.mayHaveBooleanValue(true) or this.asExpr() instanceof NullLiteral }
+  }
+
+  /** An overly permissive value for `origin` (Express) */
+  class WildcardValue extends Source {
+    WildcardValue() { this.mayHaveStringValue("*") }
+  }
+
+  /**
+   * The value of cors origin when initializing the application.
+   */
+  class CorsApolloServer extends Sink, DataFlow::ValueNode {
+    CorsApolloServer() {
+      exists(ApolloServer agql |
+        this =
+          agql.getOptionArgument(0, "cors").getALocalSource().getAPropertyWrite("origin").getRhs()
+      )
+    }
+  }
+
+  /**
+   * The value of cors origin when initializing the application.
+   */
+  class ExpressCors extends Sink, DataFlow::ValueNode {
+    ExpressCors() {
+      exists(CorsConfiguration config | this = config.getCorsConfiguration().getOrigin())
+    }
+  }
+
+  /**
+   * An express route setup configured with the `cors` package.
+   */
+  class CorsConfiguration extends DataFlow::MethodCallNode {
+    Cors corsConfig;
+
+    CorsConfiguration() {
+      exists(Express::RouteSetup setup | this = setup |
+        if setup.isUseCall()
+        then corsConfig = setup.getArgument(0)
+        else corsConfig = setup.getArgument(any(int i | i > 0))
+      )
+    }
+
+    /** Gets the expression that configures `cors` on this route setup. */
+    Cors getCorsConfiguration() { result = corsConfig }
+  }
+}

javascript/ql/src/experimental/Security/CWE-942/CorsPermissiveConfigurationQuery.qll

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+/**
+ * Provides a dataflow taint tracking configuration for reasoning
+ * about overly permissive CORS configurations.
+ *
+ * Note, for performance reasons: only import this file if
+ * `CorsPermissiveConfiguration::Configuration` is needed,
+ * otherwise `CorsPermissiveConfigurationCustomizations` should
+ * be imported instead.
+ */
+
+import javascript
+import CorsPermissiveConfigurationCustomizations::CorsPermissiveConfiguration
+
+/**
+ * A data flow configuration for overly permissive CORS configuration.
+ */
+class Configuration extends TaintTracking::Configuration {
+  Configuration() { this = "CorsPermissiveConfiguration" }
+
+  override predicate isSource(DataFlow::Node source, DataFlow::FlowLabel label) {
+    source instanceof TrueNullValue and label = truenullLabel()
+    or
+    source instanceof WildcardValue and label = wildcardLabel()
+    or
+    source instanceof RemoteFlowSource and label = DataFlow::FlowLabel::taint()
+  }
+
+  override predicate isSink(DataFlow::Node sink, DataFlow::FlowLabel label) {
+    sink instanceof CorsApolloServer and label = [DataFlow::FlowLabel::taint(), truenullLabel()]
+    or
+    sink instanceof ExpressCors and label = [DataFlow::FlowLabel::taint(), wildcardLabel()]
+  }
+
+  override predicate isSanitizer(DataFlow::Node node) {
+    super.isSanitizer(node) or
+    node instanceof Sanitizer
+  }
+}
+
+private class WildcardActivated extends DataFlow::FlowLabel, Wildcard {
+  WildcardActivated() { this = this }
+}
+
+private class TrueAndNullActivated extends DataFlow::FlowLabel, TrueAndNull {
+  TrueAndNullActivated() { this = this }
+}

javascript/ql/src/experimental/Security/CWE-942/examples/CorsPermissiveConfigurationBad.js

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+import { ApolloServer } from 'apollo-server';
+var https = require('https'),
+    url = require('url');
+
+var server = https.createServer(function () { });
+
+server.on('request', function (req, res) {
+    // BAD: origin is too permissive
+    const server_1 = new ApolloServer({
+        cors: { origin: true }
+    });
+
+    let user_origin = url.parse(req.url, true).query.origin;
+    // BAD: CORS is controlled by user
+    const server_2 = new ApolloServer({
+        cors: { origin: user_origin }
+    });
+});

javascript/ql/src/experimental/Security/CWE-942/examples/CorsPermissiveConfigurationGood.js

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+import { ApolloServer } from 'apollo-server';
+var https = require('https'),
+    url = require('url');
+
+var server = https.createServer(function () { });
+
+server.on('request', function (req, res) {
+    // GOOD: origin is restrictive
+    const server_1 = new ApolloServer({
+        cors: { origin: false }
+    });
+
+    let user_origin = url.parse(req.url, true).query.origin;
+    // GOOD: user data is properly sanitized
+    const server_2 = new ApolloServer({
+        cors: { origin: (user_origin === "https://allowed1.com" || user_origin === "https://allowed2.com") ? user_origin : false }
+    });
+});

javascript/ql/test/experimental/Security/CWE-942/CorsPermissiveConfiguration.expected

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+nodes
+| apollo-test.js:8:9:8:59 | user_origin |
+| apollo-test.js:8:23:8:46 | url.par ... , true) |
+| apollo-test.js:8:23:8:52 | url.par ... ).query |
+| apollo-test.js:8:23:8:59 | url.par ... .origin |
+| apollo-test.js:8:33:8:39 | req.url |
+| apollo-test.js:8:33:8:39 | req.url |
+| apollo-test.js:11:25:11:28 | true |
+| apollo-test.js:11:25:11:28 | true |
+| apollo-test.js:11:25:11:28 | true |
+| apollo-test.js:21:25:21:28 | null |
+| apollo-test.js:21:25:21:28 | null |
+| apollo-test.js:21:25:21:28 | null |
+| apollo-test.js:26:25:26:35 | user_origin |
+| apollo-test.js:26:25:26:35 | user_origin |
+| express-test.js:10:9:10:59 | user_origin |
+| express-test.js:10:23:10:46 | url.par ... , true) |
+| express-test.js:10:23:10:52 | url.par ... ).query |
+| express-test.js:10:23:10:59 | url.par ... .origin |
+| express-test.js:10:33:10:39 | req.url |
+| express-test.js:10:33:10:39 | req.url |
+| express-test.js:26:17:26:19 | '*' |
+| express-test.js:26:17:26:19 | '*' |
+| express-test.js:26:17:26:19 | '*' |
+| express-test.js:33:17:33:27 | user_origin |
+| express-test.js:33:17:33:27 | user_origin |
+edges
+| apollo-test.js:8:9:8:59 | user_origin | apollo-test.js:26:25:26:35 | user_origin |
+| apollo-test.js:8:9:8:59 | user_origin | apollo-test.js:26:25:26:35 | user_origin |
+| apollo-test.js:8:23:8:46 | url.par ... , true) | apollo-test.js:8:23:8:52 | url.par ... ).query |
+| apollo-test.js:8:23:8:52 | url.par ... ).query | apollo-test.js:8:23:8:59 | url.par ... .origin |
+| apollo-test.js:8:23:8:59 | url.par ... .origin | apollo-test.js:8:9:8:59 | user_origin |
+| apollo-test.js:8:33:8:39 | req.url | apollo-test.js:8:23:8:46 | url.par ... , true) |
+| apollo-test.js:8:33:8:39 | req.url | apollo-test.js:8:23:8:46 | url.par ... , true) |
+| apollo-test.js:11:25:11:28 | true | apollo-test.js:11:25:11:28 | true |
+| apollo-test.js:21:25:21:28 | null | apollo-test.js:21:25:21:28 | null |
+| express-test.js:10:9:10:59 | user_origin | express-test.js:33:17:33:27 | user_origin |
+| express-test.js:10:9:10:59 | user_origin | express-test.js:33:17:33:27 | user_origin |
+| express-test.js:10:23:10:46 | url.par ... , true) | express-test.js:10:23:10:52 | url.par ... ).query |
+| express-test.js:10:23:10:52 | url.par ... ).query | express-test.js:10:23:10:59 | url.par ... .origin |
+| express-test.js:10:23:10:59 | url.par ... .origin | express-test.js:10:9:10:59 | user_origin |
+| express-test.js:10:33:10:39 | req.url | express-test.js:10:23:10:46 | url.par ... , true) |
+| express-test.js:10:33:10:39 | req.url | express-test.js:10:23:10:46 | url.par ... , true) |
+| express-test.js:26:17:26:19 | '*' | express-test.js:26:17:26:19 | '*' |
+#select
+| apollo-test.js:11:25:11:28 | true | apollo-test.js:11:25:11:28 | true | apollo-test.js:11:25:11:28 | true | CORS Origin misconfiguration due to a $@. | apollo-test.js:11:25:11:28 | true | too permissive or user controlled value |
+| apollo-test.js:21:25:21:28 | null | apollo-test.js:21:25:21:28 | null | apollo-test.js:21:25:21:28 | null | CORS Origin misconfiguration due to a $@. | apollo-test.js:21:25:21:28 | null | too permissive or user controlled value |
+| apollo-test.js:26:25:26:35 | user_origin | apollo-test.js:8:33:8:39 | req.url | apollo-test.js:26:25:26:35 | user_origin | CORS Origin misconfiguration due to a $@. | apollo-test.js:8:33:8:39 | req.url | too permissive or user controlled value |
+| express-test.js:26:17:26:19 | '*' | express-test.js:26:17:26:19 | '*' | express-test.js:26:17:26:19 | '*' | CORS Origin misconfiguration due to a $@. | express-test.js:26:17:26:19 | '*' | too permissive or user controlled value |
+| express-test.js:33:17:33:27 | user_origin | express-test.js:10:33:10:39 | req.url | express-test.js:33:17:33:27 | user_origin | CORS Origin misconfiguration due to a $@. | express-test.js:10:33:10:39 | req.url | too permissive or user controlled value |

javascript/ql/test/experimental/Security/CWE-942/CorsPermissiveConfiguration.qlref

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+./experimental/Security/CWE-942/CorsPermissiveConfiguration.ql