Move from experimental

java/ql/src/Security/CWE/CWE-117/LogInjection.qhelp

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+
+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp>
+
+<overview>
+
+<p>If unsanitized user input is written to a log entry, a malicious user may be able to forge new log entries.</p>
+
+<p>Forgery can occur if a user provides some input creating the appearance of multiple
+  log entries. This can include unescaped new-line characters, or HTML or other markup.</p>
+</overview>
+
+<recommendation>
+<p>
+User input should be suitably sanitized before it is logged.
+</p>
+<p>
+If the log entries are plain text then line breaks should be removed from user input, using for example
+<code>String replace(char oldChar, char newChar)</code> or similar. Care should also be taken that user input is clearly marked
+in log entries, and that a malicious user cannot cause confusion in other ways.
+</p>
+<p>
+For log entries that will be displayed in HTML, user input should be HTML encoded before being logged, to prevent forgery and
+other forms of HTML injection.
+</p>
+
+</recommendation>
+
+<example>
+  <p>In the example, a username, provided by the user, is logged using <code>logger.warn</code> (from  <code>org.slf4j.Logger</code>). 
+    In the first case (<code>/bad</code> endpoint), the username is logged without any sanitization.
+    If a malicious user provides <code>Guest'%0AUser:'Admin</code> as a username parameter, 
+    the log entry will be split into two separate lines, where the first line will be <code>User:'Guest'</code> and the second one will be <code>User:'Admin'</code>.
+</p>
+<sample src="LogInjectionBad.java" />
+
+<p> In the second case (<code>/good</code> endpoint), <code>matches()</code> is used to ensure the user input only has alphanumeric characters.
+  If a malicious user provides `Guest'%0AUser:'Admin` as a username parameter, 
+  the log entry will not be split into two separate lines, resulting in a single line <code>User:'Guest'User:'Admin'</code>.</p>
+
+<sample src="LogInjectionGood.java" />
+</example>
+
+<references>
+<li>OWASP: <a href="https://owasp.org/www-community/attacks/Log_Injection">Log Injection</a>.</li>
+</references>
+</qhelp>

java/ql/src/Security/CWE/CWE-117/LogInjection.ql

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+/**
+ * @name Log Injection
+ * @description Building log entries from user-controlled data is vulnerable to
+ *              insertion of forged log entries by a malicious user.
+ * @kind path-problem
+ * @problem.severity error
+ * @precision high
+ * @id java/log-injection
+ * @tags security
+ *       external/cwe/cwe-117
+ */
+
+import java
+import DataFlow::PathGraph
+import experimental.semmle.code.java.Logging
+import semmle.code.java.dataflow.FlowSources
+
+/**
+ * A taint-tracking configuration for tracking untrusted user input used in log entries.
+ */
+private class LogInjectionConfiguration extends TaintTracking::Configuration {
+  LogInjectionConfiguration() { this = "Log Injection" }
+
+  override predicate isSource(DataFlow::Node source) { source instanceof RemoteFlowSource }
+
+  override predicate isSink(DataFlow::Node sink) {
+    sink.asExpr() = any(LoggingCall c).getALogArgument()
+  }
+
+  override predicate isSanitizer(DataFlow::Node node) {
+    node.getType() instanceof BoxedType or node.getType() instanceof PrimitiveType
+  }
+}
+
+from LogInjectionConfiguration cfg, DataFlow::PathNode source, DataFlow::PathNode sink
+where cfg.hasFlowPath(source, sink)
+select sink.getNode(), source, sink, "$@ flows to log entry.", source.getNode(),
+  "User-provided value"

java/ql/src/Security/CWE/CWE-117/LogInjectionBad.java

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+package com.example.restservice;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class LogInjection {
+
+    private final Logger log = LoggerFactory.getLogger(LogInjection.class);
+
+    // /bad?username=Guest'%0AUser:'Admin
+    @GetMapping("/bad")
+    public String bad(@RequestParam(value = "username", defaultValue = "name") String username) {
+        log.warn("User:'{}'", username);
+        // The logging call above would result in multiple log entries as shown below:
+        // User:'Guest'
+        // User:'Admin'
+        return username;
+    }
+}
+

java/ql/src/Security/CWE/CWE-117/LogInjectionGood.java

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+package com.example.restservice;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class LogInjection {
+
+    private final Logger log = LoggerFactory.getLogger(LogInjection.class);
+
+    // /good?username=Guest'%0AUser:'Admin
+    @GetMapping("/good")
+    public String good(@RequestParam(value = "username", defaultValue = "name") String username) {
+        // The regex check here, allows only alphanumeric characters to pass.
+        // Hence, does not result in log injection
+        if (username.matches("\w*")) {
+            log.warn("User:'{}'", username);
+            
+            return username;
+        }
+    }
+}