RegexInjection.ql

/**
 * @name Regular expression injection
 * @description User input should not be used in regular expressions without first being escaped,
 *              otherwise a malicious user may be able to provide a regex that could require
 *              exponential time on certain inputs.
 * @kind path-problem
 * @problem.severity error
 * @security-severity 7.5
 * @precision high
 * @id cs/regex-injection
 * @tags security
 *       external/cwe/cwe-730
 *       external/cwe/cwe-400
 */

import csharp
import semmle.code.csharp.security.dataflow.RegexInjectionQuery::RegexInjection
import semmle.code.csharp.frameworks.system.text.RegularExpressions
import semmle.code.csharp.dataflow.DataFlow::DataFlow::PathGraph

from TaintTrackingConfiguration c, DataFlow::PathNode source, DataFlow::PathNode sink
where
  c.hasFlowPath(source, sink) and
  // No global timeout set
  not exists(RegexGlobalTimeout r)
select sink.getNode(), source, sink, "$@ flows to the construction of a regular expression.",
  source.getNode(), "User-provided value"