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Merge pull request #9718 from asgerf/js/case-sensitive-middleware
JS: Add 'case sensitive middleware' query
2 parents 43a8200 + 18c5a8c commit 855d4c2

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‎javascript/ql/lib/semmle/javascript/Routing.qll‎

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@@ -148,6 +148,18 @@ module Routing {
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this instanceof MkRouter
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}
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/**
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* Like `mayResumeDispatch` but without the assumption that functions with an unknown
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* implementation invoke their continuation.
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*/
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predicate definitelyResumesDispatch() {
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this.getLastChild().definitelyResumesDispatch()
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or
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exists(this.(RouteHandler).getAContinuationInvocation())
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or
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this instanceof MkRouter
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}
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/** Gets the parent of this node, provided that this node may invoke its continuation. */
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private Node getContinuationParent() {
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result = this.getParent() and

‎javascript/ql/lib/semmle/javascript/frameworks/Express.qll‎

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@@ -33,6 +33,11 @@ module Express {
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or
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// `app = [new] express.Router()`
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result = DataFlow::moduleMember("express", "Router").getAnInvocation()
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or
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exists(DataFlow::SourceNode app |
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app.hasUnderlyingType("probot/lib/application", "Application") and
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result = app.getAMethodCall("route")
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)
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}
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/**
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override DataFlow::SourceNode getOutput() { result = this.getCallback(2).getParameter(1) }
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}
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private class ResumeDispatchRefinement extends Routing::RouteHandler {
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ResumeDispatchRefinement() { this.getFunction() instanceof RouteHandler }
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override predicate mayResumeDispatch() { this.getAParameter().getName() = "next" }
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override predicate definitelyResumesDispatch() { this.getAParameter().getName() = "next" }
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}
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private class ExpressStaticResumeDispatchRefinement extends Routing::Node {
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ExpressStaticResumeDispatchRefinement() {
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this = Routing::getNode(DataFlow::moduleMember("express", "static").getACall())
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}
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override predicate mayResumeDispatch() { none() }
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override predicate definitelyResumesDispatch() { none() }
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}
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}

‎javascript/ql/src/Security/CWE-178/CaseSensitiveMiddlewarePath.qhelp‎

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<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>
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Using a case-sensitive regular expression path in a middleware route enables an attacker to bypass that middleware
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when accessing an endpoint with a case-insensitive path.
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Paths specified using a string are case-insensitive, whereas regular expressions are case-sensitive by default.
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</p>
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</overview>
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<recommendation>
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<p>
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When using a regular expression as a middleware path, make sure the regular expression is
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case-insensitive by adding the <code>i</code> flag.
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</p>
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</recommendation>
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<example>
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<p>
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The following example restricts access to paths in the <code>/admin</code> path to users logged in as
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administrators:
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</p>
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<sample src="examples/CaseSensitiveMiddlewarePath.js" />
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<p>
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A path such as <code>/admin/users/45</code> can only be accessed by an administrator. However, the path
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<code>/ADMIN/USERS/45</code> can be accessed by anyone because the upper-case path doesn't match the case-sensitive regular expression, whereas
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Express considers it to match the path string <code>/admin/users</code>.
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</p>
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<p>
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The issue can be fixed by adding the <code>i</code> flag to the regular expression:
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</p>
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<sample src="examples/CaseSensitiveMiddlewarePathGood.js" />
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</example>
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<references>
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<li>
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MDN
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<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions#advanced_searching_with_flags">Regular Expression Flags</a>.
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</li>
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</references>
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</qhelp>

‎javascript/ql/src/Security/CWE-178/CaseSensitiveMiddlewarePath.ql‎

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/**
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* @name Case-sensitive middleware path
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* @description Middleware with case-sensitive paths do not protect endpoints with case-insensitive paths.
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* @kind problem
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* @problem.severity warning
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* @security-severity 7.3
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* @precision high
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* @id js/case-sensitive-middleware-path
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* @tags security
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* external/cwe/cwe-178
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*/
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import javascript
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/**
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* Converts `s` to upper case, or to lower-case if it was already upper case.
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*/
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bindingset[s]
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string toOtherCase(string s) {
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if s.regexpMatch(".*[a-z].*") then result = s.toUpperCase() else result = s.toLowerCase()
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}
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RegExpCharacterClass getEnclosingClass(RegExpTerm term) {
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term = result.getAChild()
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or
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term = result.getAChild().(RegExpRange).getAChild()
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}
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/**
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* Holds if `term` seems to distinguish between upper and lower case letters, assuming the `i` flag is not present.
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*/
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pragma[inline]
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predicate isLikelyCaseSensitiveRegExp(RegExpTerm term) {
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exists(RegExpConstant const |
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const = term.getAChild*() and
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const.getValue().regexpMatch(".*[a-zA-Z].*") and
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not getEnclosingClass(const).getAChild().(RegExpConstant).getValue() =
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toOtherCase(const.getValue()) and
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not const.getParent*() instanceof RegExpNegativeLookahead and
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not const.getParent*() instanceof RegExpNegativeLookbehind
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)
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}
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/**
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* Gets a string matched by `term`, or part of such a string.
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*/
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string getExampleString(RegExpTerm term) {
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result = term.getAMatchedString()
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or
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// getAMatchedString does not recurse into sequences. Perform one step manually.
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exists(RegExpSequence seq | seq = term |
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result =
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strictconcat(RegExpTerm child, int i, string text |
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child = seq.getChild(i) and
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(
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text = child.getAMatchedString()
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or
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not exists(child.getAMatchedString()) and
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text = ""
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)
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|
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text order by i
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)
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)
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}
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string getCaseSensitiveBypassExample(RegExpTerm term) {
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exists(string example |
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example = getExampleString(term) and
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result = toOtherCase(example) and
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result != example // getting an example string is approximate; ensure we got a proper case-change example
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)
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}
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/**
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* Holds if `setup` has a path-argument `arg` referring to the given case-sensitive `regexp`.
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*/
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predicate isCaseSensitiveMiddleware(
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Routing::RouteSetup setup, DataFlow::RegExpCreationNode regexp, DataFlow::Node arg
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) {
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exists(DataFlow::MethodCallNode call |
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setup = Routing::getRouteSetupNode(call) and
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(
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setup.definitelyResumesDispatch()
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or
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// If applied to all HTTP methods, be a bit more lenient in detecting middleware
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setup.mayResumeDispatch() and
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not exists(setup.getOwnHttpMethod())
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) and
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arg = call.getArgument(0) and
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regexp.getAReference().flowsTo(arg) and
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isLikelyCaseSensitiveRegExp(regexp.getRoot()) and
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exists(string flags |
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flags = regexp.getFlags() and
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not RegExp::isIgnoreCase(flags)
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)
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)
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}
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predicate isGuardedCaseInsensitiveEndpoint(
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Routing::RouteSetup endpoint, Routing::RouteSetup middleware
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) {
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isCaseSensitiveMiddleware(middleware, _, _) and
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exists(DataFlow::MethodCallNode call |
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endpoint = Routing::getRouteSetupNode(call) and
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endpoint.isGuardedByNode(middleware) and
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call.getArgument(0).mayHaveStringValue(_)
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)
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}
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from
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DataFlow::RegExpCreationNode regexp, Routing::RouteSetup middleware, Routing::RouteSetup endpoint,
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DataFlow::Node arg, string example
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where
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isCaseSensitiveMiddleware(middleware, regexp, arg) and
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example = getCaseSensitiveBypassExample(regexp.getRoot()) and
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isGuardedCaseInsensitiveEndpoint(endpoint, middleware) and
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exists(endpoint.getRelativePath().toLowerCase().indexOf(example.toLowerCase()))
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select arg,
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"This route uses a case-sensitive path $@, but is guarding a case-insensitive path $@. A path such as '"
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+ example + "' will bypass the middleware.", regexp, "pattern", endpoint, "here"

‎javascript/ql/src/Security/CWE-178/examples/CaseSensitiveMiddlewarePath.js‎

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const app = require('express')();
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app.use(/\/admin\/.*/, (req, res, next) => {
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if (!req.user.isAdmin) {
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res.status(401).send('Unauthorized');
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} else {
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next();
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}
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});
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app.get('/admin/users/:id', (req, res) => {
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res.send(app.database.users[req.params.id]);
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});

‎javascript/ql/src/Security/CWE-178/examples/CaseSensitiveMiddlewarePathGood.js‎

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const app = require('express')();
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app.use(/\/admin\/.*/i, (req, res, next) => {
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if (!req.user.isAdmin) {
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res.status(401).send('Unauthorized');
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} else {
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next();
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}
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});
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app.get('/admin/users/:id', (req, res) => {
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res.send(app.database.users[req.params.id]);
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});

‎javascript/ql/src/change-notes/2022-06-27-case-sensitive-middleware.md‎

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---
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category: newQuery
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---
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- A new query "Case-sensitive middleware path" (`js/case-sensitive-middleware-path`) has been added.
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It highlights middleware routes that can be bypassed due to having a case-sensitive regular expression path.

‎javascript/ql/test/query-tests/Security/CWE-178/CaseSensitiveMiddlewarePath.expected‎

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| tst.js:8:9:8:19 | /\\/foo\\/.*/ | This route uses a case-sensitive path $@, but is guarding a case-insensitive path $@. A path such as '/FOO/' will bypass the middleware. | tst.js:8:9:8:19 | /\\/foo\\/.*/ | pattern | tst.js:60:1:61:2 | app.get ... ware\\n}) | here |
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| tst.js:14:5:14:28 | new Reg ... (.*)?') | This route uses a case-sensitive path $@, but is guarding a case-insensitive path $@. A path such as '/FOO' will bypass the middleware. | tst.js:14:5:14:28 | new Reg ... (.*)?') | pattern | tst.js:60:1:61:2 | app.get ... ware\\n}) | here |
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| tst.js:41:9:41:25 | /\\/foo\\/([0-9]+)/ | This route uses a case-sensitive path $@, but is guarding a case-insensitive path $@. A path such as '/FOO/' will bypass the middleware. | tst.js:41:9:41:25 | /\\/foo\\/([0-9]+)/ | pattern | tst.js:60:1:61:2 | app.get ... ware\\n}) | here |

‎javascript/ql/test/query-tests/Security/CWE-178/CaseSensitiveMiddlewarePath.qlref‎

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Security/CWE-178/CaseSensitiveMiddlewarePath.ql

‎javascript/ql/test/query-tests/Security/CWE-178/charclass.js‎

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const express = require('express');
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const app = express();
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app.get(/\/[a-zA-Z]+/, (req, res, next) => { // OK - regexp term is case insensitive
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next();
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});
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app.get('/foo', (req, res) => {
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});

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