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Merge pull request #18946 from paldepind/rust-regex-injection
Rust: Add regular expression injection query
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‎rust/ql/integration-tests/hello-project/summary.expected‎

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| Macro calls - resolved | 2 |
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| Macro calls - total | 2 |
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| Macro calls - unresolved | 0 |
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| Taint edges - number of edges | 1670 |
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| Taint edges - number of edges | 1671 |
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| Taint reach - nodes tainted | 0 |
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| Taint reach - per million nodes | 0 |
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| Taint sinks - cryptographic operations | 0 |

‎rust/ql/integration-tests/hello-workspace/summary.cargo.expected‎

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| Macro calls - resolved | 2 |
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| Macro calls - total | 2 |
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| Macro calls - unresolved | 0 |
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| Taint edges - number of edges | 1670 |
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| Taint edges - number of edges | 1671 |
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| Taint reach - nodes tainted | 0 |
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| Taint reach - per million nodes | 0 |
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| Taint sinks - cryptographic operations | 0 |

‎rust/ql/integration-tests/hello-workspace/summary.rust-project.expected‎

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| Macro calls - resolved | 2 |
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| Macro calls - total | 2 |
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| Macro calls - unresolved | 0 |
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| Taint edges - number of edges | 1670 |
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| Taint edges - number of edges | 1671 |
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| Taint reach - nodes tainted | 0 |
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| Taint reach - per million nodes | 0 |
2020
| Taint sinks - cryptographic operations | 0 |

‎rust/ql/lib/codeql/rust/frameworks/regex.model.yml‎

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# Models for the `regex` crate.
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extensions:
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- addsTo:
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pack: codeql/rust-all
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extensible: summaryModel
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data:
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- ["repo:https://github.com/rust-lang/regex:regex", "crate::escape", "Argument[0].Reference", "ReturnValue", "taint", "manual"]

‎rust/ql/lib/codeql/rust/security/regex/RegexInjectionExtensions.qll‎

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/**
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* Provides classes and predicates to reason about regular expression injection
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* vulnerabilities.
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*/
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private import codeql.util.Unit
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private import rust
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private import codeql.rust.dataflow.DataFlow
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private import codeql.rust.controlflow.CfgNodes
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private import codeql.rust.dataflow.FlowSink
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/**
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* A data flow sink for regular expression injection vulnerabilities.
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*/
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abstract class RegexInjectionSink extends DataFlow::Node { }
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/**
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* A barrier for regular expression injection vulnerabilities.
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*/
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abstract class RegexInjectionBarrier extends DataFlow::Node { }
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/** A sink for `a` in `Regex::new(a)` when `a` is not a literal. */
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private class NewRegexInjectionSink extends RegexInjectionSink {
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NewRegexInjectionSink() {
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exists(CallExprCfgNode call, PathExpr path |
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path = call.getFunction().getExpr() and
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path.getResolvedCrateOrigin() = "repo:https://github.com/rust-lang/regex:regex" and
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path.getResolvedPath() = "<crate::regex::string::Regex>::new" and
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this.asExpr() = call.getArgument(0) and
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not this.asExpr() instanceof LiteralExprCfgNode
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)
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}
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}
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private class MadRegexInjectionSink extends RegexInjectionSink {
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MadRegexInjectionSink() { sinkNode(this, "regex-use") }
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}
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/**
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* A unit class for adding additional flow steps.
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*/
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class RegexInjectionAdditionalFlowStep extends Unit {
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/**
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* Holds if the step from `node1` to `node2` should be considered a flow
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* step for paths related to regular expression injection vulnerabilities.
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*/
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abstract predicate step(DataFlow::Node node1, DataFlow::Node node2);
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}
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/**
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* An escape barrier for regular expression injection vulnerabilities.
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*/
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private class RegexInjectionDefaultBarrier extends RegexInjectionBarrier {
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RegexInjectionDefaultBarrier() {
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// A barrier is any call to a function named `escape`, in particular this
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// makes calls to `regex::escape` a barrier.
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this.asExpr()
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.getExpr()
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.(CallExpr)
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.getFunction()
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.(PathExpr)
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.getPath()
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.getPart()
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.getNameRef()
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.getText() = "escape"
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}
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}

‎rust/ql/src/queries/security/CWE-020/RegexInjection.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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Constructing a regular expression with unsanitized user input can be dangerous.
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A malicious user may be able to modify the meaning of the expression, causing it
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to match unexpected strings and construct large regular expressions by using
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counted repetitions.
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</p>
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</overview>
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<recommendation>
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<p>
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Before embedding user input into a regular expression, escape the input string
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using a function such as <a
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href="https://docs.rs/regex/latest/regex/fn.escape.html">regex::escape</a> to
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escape meta-characters that have special meaning.
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</p>
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<p>
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If purposefully supporting user supplied regular expressions, then use <a
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href="https://docs.rs/regex/latest/regex/struct.RegexBuilder.html#method.size_limit">RegexBuilder::size_limit</a>
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to limit the pattern size so that it is no larger than necessary.
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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 constructs a regular expressions from the user input
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<code>key</code> without escaping it first.
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</p>
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<sample src="RegexInjectionBad.rs" />
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<p>
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The regular expression is intended to match strings starting with
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<code>"property"</code> such as <code>"property:foo=bar"</code>. However, a
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malicious user might inject the regular expression <code>".*^|key"</code> and
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unexpectedly cause strings such as <code>"key=secret"</code> to match.
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</p>
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<p>
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If user input is used to construct a regular expression, it should be escaped
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first. This ensures that malicious users cannot insert characters that have special
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meanings in regular expressions.
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</p>
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<sample src="RegexInjectionGood.rs" />
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</example>
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<references>
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<li>
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<code>regex</code> crate documentation: <a href="https://docs.rs/regex/latest/regex/index.html#untrusted-patterns">Untrusted patterns</a>.
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</li>
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</references>
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</qhelp>

‎rust/ql/src/queries/security/CWE-020/RegexInjection.ql‎

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/**
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* @name Regular expression injection
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* @description User input should not be used in regular expressions without first being
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* escaped, otherwise a malicious user may be able to inject an expression that
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* could modify the meaning of the expression, causing it to match unexpected
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* strings.
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* @kind path-problem
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* @problem.severity error
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* @security-severity 7.8
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* @precision high
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* @id rust/regex-injection
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* @tags security
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* external/cwe/cwe-020
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* external/cwe/cwe-074
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*/
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private import rust
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private import codeql.rust.dataflow.DataFlow
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private import codeql.rust.dataflow.TaintTracking
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private import codeql.rust.Concepts
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private import codeql.rust.security.regex.RegexInjectionExtensions
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/**
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* A taint configuration for detecting regular expression injection vulnerabilities.
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*/
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module RegexInjectionConfig implements DataFlow::ConfigSig {
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predicate isSource(DataFlow::Node source) { source instanceof ActiveThreatModelSource }
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predicate isSink(DataFlow::Node sink) { sink instanceof RegexInjectionSink }
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predicate isBarrier(DataFlow::Node barrier) { barrier instanceof RegexInjectionBarrier }
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predicate isAdditionalFlowStep(DataFlow::Node nodeFrom, DataFlow::Node nodeTo) {
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any(RegexInjectionAdditionalFlowStep s).step(nodeFrom, nodeTo)
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}
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}
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/**
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* Detect taint flow of tainted data that reaches a regular expression sink.
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*/
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module RegexInjectionFlow = TaintTracking::Global<RegexInjectionConfig>;
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private import RegexInjectionFlow::PathGraph
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from RegexInjectionFlow::PathNode sourceNode, RegexInjectionFlow::PathNode sinkNode
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where RegexInjectionFlow::flowPath(sourceNode, sinkNode)
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select sinkNode.getNode(), sourceNode, sinkNode,
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"This regular expression is constructed from a $@.", sourceNode.getNode(), "user-provided value"

‎rust/ql/src/queries/security/CWE-020/RegexInjectionBad.rs‎

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use regex::Regex;
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fn get_value<'h>(key: &str, property: &'h str) -> Option<&'h str> {
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// BAD: User provided `key` is interpolated into the regular expression.
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let pattern = format!(r"^property:{key}=(.*)$");
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let re = Regex::new(&pattern).unwrap();
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re.captures(property)?.get(1).map(|m| m.as_str())
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}

‎rust/ql/src/queries/security/CWE-020/RegexInjectionGood.rs‎

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use regex::{escape, Regex};
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fn get_value<'h>(key: &str, property: &'h str) -> option<&'h str> {
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// GOOD: User input is escaped before being used in the regular expression.
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let escaped_key = escape(key);
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let pattern = format!(r"^property:{escaped_key}=(.*)$");
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let re = regex::new(&pattern).unwrap();
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re.captures(property)?.get(1).map(|m| m.as_str())
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}

‎rust/ql/test/default-threat-models.model.yml‎

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extensions:
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- addsTo:
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pack: codeql/threat-models
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extensible: threatModelConfiguration
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data:
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- ["local", true, 0]

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