Java: Big Decimal DOS

java/ql/src/experimental/Security/BigDecimalDOS/BigDecimalDOS.java

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+	@GetMapping("/tonghuaroot-DOSDemo01")
+	@ResponseBody
+    // BAD:
+	public Long demo(@RequestParam(name = "num") BigDecimal num) {
+		Long startTime = System.currentTimeMillis();
+		BigDecimal num1 = new BigDecimal(0.005);
+		System.out.println(num1.add(num));
+		Long endTime = System.currentTimeMillis();
+		Long tempTime = (endTime - startTime);
+		System.out.println(tempTime);
+		return tempTime;
+	}
+
+    @GetMapping("/tonghuaroot-DOSDemo02")
+	@ResponseBody
+    // GOOD:
+	public Long demo02(@RequestParam(name = "num") String num) {
+        if (num.length() > 33 || num.matches("(?i)e")) { 
+            return "Input Parameter is too long."
+        }
+		Long startTime = System.currentTimeMillis();
+		BigDecimal num1 = new BigDecimal(0.005);
+		System.out.println(num1.add(num));
+		Long endTime = System.currentTimeMillis();
+		Long tempTime = (endTime - startTime);
+		System.out.println(tempTime);
+		return tempTime;
+	}

java/ql/src/experimental/Security/BigDecimalDOS/BigDecimalDOS.qhelp

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+<!DOCTYPE qhelp PUBLIC
+  "-//Semmle//qhelp//EN"
+  "qhelp.dtd">
+<qhelp>
+
+
+<overview>
+<p>Directly incorporating user input into an BigDecimal Operation Function without validating the input
+can facilitate DOS attacks. In these attacks, the server
+will consume a lot of computing resources. A typical scenario is that the CPU usage rises to close to 100%.
+This issue often occurs in scenarios that require scientific computing, such as e-commerce platforms and electronic payments.
+</p>
+
+</overview>
+<recommendation>
+
+<p>To guard against BigDecimal DOS attacks, you should avoid putting user-provided input
+directly into a BigDecimal Method(like: add(), subtract()). Instead, In some e-commerce payment scenarios, 
+we should verify the size of the incoming number. For example, under normal circumstances, 
+the number representing money will not contain "e".</p>
+
+</recommendation>
+<example>
+
+<p>The following example shows a BigDecimal parameter being directly passed
+to a BigDecimal method (like: add(), subtract()) without validating the input, which facilitates DOS attacks.
+It also shows how to remedy the problem by validating the user input against a known fixed string.
+</p>
+
+<sample src="BigDecimalDOS.java" />
+
+</example>
+<references>
+  <li>
+    <a href="https://www.cuijianxiong.top/2021/03/30/%E6%9A%B4%E5%8A%9B%E7%9A%84%E6%94%BB%E5%87%BBDos/">暴力的攻击-Dos</a>
+  </li>
+  <li>
+    <a href="https://mp.weixin.qq.com/s/4YX7XA34fShdCpGawO-Q_Q">BigDecimal DOS</a>
+  </li>
+
+</references>
+</qhelp>

java/ql/src/experimental/Security/BigDecimalDOS/BigDecimalDOS.ql

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+/**
+ * @id java/BigDecimalDOS
+ * @name Java-BigDecimal-DOS-Vulnerability
+ * @description When user-controllable data is passed to the relevant methods in BigDecimal, it may cause DOS issues when computing resources are limited. This issue is common in business scenarios such as e-commerce platforms.
+ * @kind path-problem
+ * @problem.severity error
+ */
+
+import java
+import semmle.code.java.dataflow.FlowSources
+import DataFlow::PathGraph
+
+class BigDecimalDOSConfig extends TaintTracking::Configuration {
+  BigDecimalDOSConfig() { this = "Java-BigDecimal-DOS-Vulnerability-Config" }
+
+  override predicate isSource(DataFlow::Node src) { src instanceof RemoteFlowSource }
+
+  override predicate isSink(DataFlow::Node sink) {
+    exists(Method method, MethodAccess call |
+      method.getDeclaringType().hasQualifiedName("java.math", "BigDecimal") and
+      method.hasName(["add", "subtract"]) and
+      call.getMethod() = method and
+      sink.asExpr() = call.getArgument(0)
+    )
+  }
+}
+
+from BigDecimalDOSConfig config, DataFlow::PathNode source, DataFlow::PathNode sink
+where config.hasFlowPath(source, sink)
+select source.getNode(), source, sink, "Potential Java BigDecimal DOS issue due to $@.",
+  source.getNode(), "a user-provided value"

java/ql/test/experimental/query-tests/security/BigDecimalDOS/BigDecimalDOS.expected

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+edges
+| BigDecimalDOS.java:12:28:12:69 | num : BigDecimal | BigDecimalDOS.java:14:30:14:32 | num |
+nodes
+| BigDecimalDOS.java:12:28:12:69 | num : BigDecimal | semmle.label | num : BigDecimal |
+| BigDecimalDOS.java:14:30:14:32 | num | semmle.label | num |
+subpaths
+#select
+| BigDecimalDOS.java:12:28:12:69 | num | BigDecimalDOS.java:12:28:12:69 | num : BigDecimal | BigDecimalDOS.java:14:30:14:32 | num | Potential Java BigDecimal DOS Issue due to $@. | BigDecimalDOS.java:12:28:12:69 | num | a user-provided value |

java/ql/test/experimental/query-tests/security/BigDecimalDOS/BigDecimalDOS.java

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+package com.example.servingwebcontent;
+
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.Model;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.ResponseBody;
+
+import java.math.BigDecimal;
+import java.math.MathContext;
+
+@Controller
+public class GreetingController {
+	@GetMapping("/tonghuaroot-DOSDemo01")
+	@ResponseBody
+    // BAD:
+	public Long demo(@RequestParam(name = "num") BigDecimal num) {
+		Long startTime = System.currentTimeMillis();
+		BigDecimal num1 = new BigDecimal(0.005);
+		System.out.println(num1.add(num));
+		Long endTime = System.currentTimeMillis();
+		Long tempTime = (endTime - startTime);
+		System.out.println(tempTime);
+		return tempTime;
+	}
+
+    @GetMapping("/tonghuaroot-DOSDemo02")
+	@ResponseBody
+    // GOOD:
+	public Long demo02(@RequestParam(name = "num") String num) {
+        if (num.length() > 33 || num.matches("(?i)e")) { 
+            return "Input Parameter is too long."
+        }
+		Long startTime = System.currentTimeMillis();
+		BigDecimal num1 = new BigDecimal(0.005);
+		System.out.println(num1.add(num));
+		Long endTime = System.currentTimeMillis();
+		Long tempTime = (endTime - startTime);
+		System.out.println(tempTime);
+		return tempTime;
+	}
+}

java/ql/test/experimental/query-tests/security/BigDecimalDOS/BigDecimalDOS.qlref

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+experimental/Security/BigDecimalDOS/BigDecimalDOS.ql

java/ql/test/experimental/query-tests/security/BigDecimalDOS/options

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+//semmle-extractor-options: --javac-args -cp ${testdir}/../../../../stubs/servlet-api-2.4:${testdir}/../../../../stubs/springframework-5.3.8/