github · aschackmull · Aug 6, 2020 · Jul 2, 2020 · Jul 18, 2020 · Jul 18, 2020
diff --git a/java/ql/src/Security/CWE/CWE-022/PathsCommon.qll b/java/ql/src/Security/CWE/CWE-022/PathsCommon.qll
diff --git a/java/ql/src/Security/CWE/CWE-022/TaintedPath.ql b/java/ql/src/Security/CWE/CWE-022/TaintedPath.ql
@@ -14,8 +14,9 @@
 
 import java
 import semmle.code.java.dataflow.FlowSources
-import PathsCommon
+import semmle.code.java.security.PathCreation
 import DataFlow::PathGraph
+import TaintedPathCommon
 
 class ContainsDotDotSanitizer extends DataFlow::BarrierGuard {
   ContainsDotDotSanitizer() {
@@ -34,7 +35,7 @@ class TaintedPathConfig extends TaintTracking::Configuration {
   override predicate isSource(DataFlow::Node source) { source instanceof RemoteFlowSource }
 
   override predicate isSink(DataFlow::Node sink) {
-    exists(Expr e | e = sink.asExpr() | e = any(PathCreation p).getInput() and not guarded(e))
+    exists(Expr e | e = sink.asExpr() | e = any(PathCreation p).getAnInput() and not guarded(e))
   }
 
   override predicate isSanitizer(DataFlow::Node node) {
@@ -48,7 +49,7 @@ class TaintedPathConfig extends TaintTracking::Configuration {
 
 from DataFlow::PathNode source, DataFlow::PathNode sink, PathCreation p, TaintedPathConfig conf
 where
-  sink.getNode().asExpr() = p.getInput() and
+  sink.getNode().asExpr() = p.getAnInput() and
   conf.hasFlowPath(source, sink)
 select p, source, sink, "$@ flows to here and is used in a path.", source.getNode(),
   "User-provided value"
diff --git a/java/ql/src/Security/CWE/CWE-022/TaintedPathCommon.qll b/java/ql/src/Security/CWE/CWE-022/TaintedPathCommon.qll
@@ -0,0 +1,33 @@
+/**
+ * Models a very basic guard for the tainted path queries.
+ */
+
+import java
+import semmle.code.java.controlflow.Guards
+import semmle.code.java.security.PathCreation
+
+private predicate inWeakCheck(Expr e) {
+  // None of these are sufficient to guarantee that a string is safe.
+  exists(MethodAccess m, Method def | m.getQualifier() = e and m.getMethod() = def |
+    def.getName() = "startsWith" or
+    def.getName() = "endsWith" or
+    def.getName() = "isEmpty" or
+    def.getName() = "equals"
+  )
+  or
+  // Checking against `null` has no bearing on path traversal.
+  exists(EqualityTest b | b.getAnOperand() = e | b.getAnOperand() instanceof NullLiteral)
+}
+
+// Ignore cases where the variable has been checked somehow,
+// but allow some particularly obviously bad cases.
+predicate guarded(VarAccess e) {
+  exists(PathCreation p | e = p.getAnInput()) and
+  exists(ConditionBlock cb, Expr c |
+    cb.getCondition().getAChildExpr*() = c and
+    c = e.getVariable().getAnAccess() and
+    cb.controls(e.getBasicBlock(), true) and
+    // Disallow a few obviously bad checks.
+    not inWeakCheck(c)
+  )
+}
diff --git a/java/ql/src/Security/CWE/CWE-022/TaintedPathLocal.ql b/java/ql/src/Security/CWE/CWE-022/TaintedPathLocal.ql
@@ -14,23 +14,26 @@
 
 import java
 import semmle.code.java.dataflow.FlowSources
-import PathsCommon
+import semmle.code.java.security.PathCreation
 import DataFlow::PathGraph
+import TaintedPathCommon
 
 class TaintedPathLocalConfig extends TaintTracking::Configuration {
   TaintedPathLocalConfig() { this = "TaintedPathLocalConfig" }
 
   override predicate isSource(DataFlow::Node source) { source instanceof LocalUserInput }
 
-  override predicate isSink(DataFlow::Node sink) { sink.asExpr() = any(PathCreation p).getInput() }
+  override predicate isSink(DataFlow::Node sink) {
+    sink.asExpr() = any(PathCreation p).getAnInput()
+  }
 }
 
 from
   DataFlow::PathNode source, DataFlow::PathNode sink, PathCreation p, Expr e,
   TaintedPathLocalConfig conf
 where
   e = sink.getNode().asExpr() and
-  e = p.getInput() and
+  e = p.getAnInput() and
   conf.hasFlowPath(source, sink) and
   not guarded(e)
 select p, source, sink, "$@ flows to here and is used in a path.", source.getNode(),

diff --git a/java/ql/src/semmle/code/java/security/PathCreation.qll b/java/ql/src/semmle/code/java/security/PathCreation.qll
@@ -0,0 +1,141 @@
+/**
+ * Models the different ways to create paths. Either by using `java.io.File`-related APIs or `java.nio.file.Path`-related APIs.
+ */
+
+import java
+
+/** Models the creation of a path. */
+abstract class PathCreation extends Expr {
+  /**
+   * Gets an input that is used in the creation of this path.
+   * This excludes inputs of type `File` and `Path`.
+   */
+  abstract Expr getAnInput();
+}
+
+/** Models the `java.nio.file.Paths.get` method. */
+private class PathsGet extends PathCreation, MethodAccess {
+  PathsGet() {
+    exists(Method m | m = this.getMethod() |
+      m.getDeclaringType() instanceof TypePaths and
+      m.getName() = "get"
+    )
+  }
+
+  override Expr getAnInput() { result = this.getAnArgument() }
+}
+
+/** Models the `java.nio.file.FileSystem.getPath` method. */
+private class FileSystemGetPath extends PathCreation, MethodAccess {
+  FileSystemGetPath() {
+    exists(Method m | m = this.getMethod() |
+      m.getDeclaringType() instanceof TypeFileSystem and
+      m.getName() = "getPath"
+    )
+  }
+
+  override Expr getAnInput() { result = this.getAnArgument() }
+}
+
+/** Models the `new java.io.File(...)` constructor. */
+private class FileCreation extends PathCreation, ClassInstanceExpr {
+  FileCreation() { this.getConstructedType() instanceof TypeFile }
+
+  override Expr getAnInput() {
+    result = this.getAnArgument() and
+    // Relevant arguments include those that are not a `File`.
+    not result.getType() instanceof TypeFile
+  }
+}
+
+/** Models the `java.nio.file.Path.resolveSibling` method. */
+private class PathResolveSiblingCreation extends PathCreation, MethodAccess {
+  PathResolveSiblingCreation() {
+    exists(Method m | m = this.getMethod() |
+      m.getDeclaringType() instanceof TypePath and
+      m.getName() = "resolveSibling"
+    )
+  }
+
+  override Expr getAnInput() {
+    result = this.getAnArgument() and
+    // Relevant arguments are those of type `String`.
+    result.getType() instanceof TypeString
+  }
+}
+
+/** Models the `java.nio.file.Path.resolve` method. */
+private class PathResolveCreation extends PathCreation, MethodAccess {
+  PathResolveCreation() {
+    exists(Method m | m = this.getMethod() |
+      m.getDeclaringType() instanceof TypePath and
+      m.getName() = "resolve"
+    )
+  }
+
+  override Expr getAnInput() {
+    result = this.getAnArgument() and
+    // Relevant arguments are those of type `String`.
+    result.getType() instanceof TypeString
+  }
+}
+
+/** Models the `java.nio.file.Path.of` method. */
+private class PathOfCreation extends PathCreation, MethodAccess {
+  PathOfCreation() {
+    exists(Method m | m = this.getMethod() |
+      m.getDeclaringType() instanceof TypePath and
+      m.getName() = "of"
+    )
+  }
+
+  override Expr getAnInput() { result = this.getAnArgument() }
+}
+
+/** Models the `new java.io.FileWriter(...)` constructor. */
+private class FileWriterCreation extends PathCreation, ClassInstanceExpr {
+  FileWriterCreation() { this.getConstructedType().hasQualifiedName("java.io", "FileWriter") }
+
+  override Expr getAnInput() {
+    result = this.getAnArgument() and
+    // Relevant arguments are those of type `String`.
+    result.getType() instanceof TypeString
+  }
+}
+
+/** Models the `new java.io.FileReader(...)` constructor. */
+private class FileReaderCreation extends PathCreation, ClassInstanceExpr {
+  FileReaderCreation() { this.getConstructedType().hasQualifiedName("java.io", "FileReader") }
+
+  override Expr getAnInput() {
+    result = this.getAnArgument() and
+    // Relevant arguments are those of type `String`.
+    result.getType() instanceof TypeString
+  }
+}
+
+/** Models the `new java.io.FileInputStream(...)` constructor. */
+private class FileInputStreamCreation extends PathCreation, ClassInstanceExpr {
+  FileInputStreamCreation() {
+    this.getConstructedType().hasQualifiedName("java.io", "FileInputStream")
+  }
+
+  override Expr getAnInput() {
+    result = this.getAnArgument() and
+    // Relevant arguments are those of type `String`.
+    result.getType() instanceof TypeString
+  }
+}
+
+/** Models the `new java.io.FileOutputStream(...)` constructor. */
+private class FileOutputStreamCreation extends PathCreation, ClassInstanceExpr {
+  FileOutputStreamCreation() {
+    this.getConstructedType().hasQualifiedName("java.io", "FileOutputStream")
+  }
+
+  override Expr getAnInput() {
+    result = this.getAnArgument() and
+    // Relevant arguments are those of type `String`.
+    result.getType() instanceof TypeString
+  }
+}
diff --git a/java/ql/test/library-tests/pathcreation/PathCreation.expected b/java/ql/test/library-tests/pathcreation/PathCreation.expected
@@ -0,0 +1,25 @@
+| PathCreation.java:13:18:13:32 | new File(...) | PathCreation.java:13:27:13:31 | "dir" |
+| PathCreation.java:14:19:14:40 | new File(...) | PathCreation.java:14:28:14:32 | "dir" |
+| PathCreation.java:14:19:14:40 | new File(...) | PathCreation.java:14:35:14:39 | "sub" |
+| PathCreation.java:18:18:18:49 | new File(...) | PathCreation.java:18:44:18:48 | "sub" |
+| PathCreation.java:18:27:18:41 | new File(...) | PathCreation.java:18:36:18:40 | "dir" |
+| PathCreation.java:22:18:22:41 | new File(...) | PathCreation.java:22:27:22:40 | new URI(...) |
+| PathCreation.java:26:18:26:31 | of(...) | PathCreation.java:26:26:26:30 | "dir" |
+| PathCreation.java:27:19:27:39 | of(...) | PathCreation.java:27:27:27:31 | "dir" |
+| PathCreation.java:27:19:27:39 | of(...) | PathCreation.java:27:34:27:38 | "sub" |
+| PathCreation.java:31:18:31:40 | of(...) | PathCreation.java:31:26:31:39 | new URI(...) |
+| PathCreation.java:35:18:35:33 | get(...) | PathCreation.java:35:28:35:32 | "dir" |
+| PathCreation.java:36:19:36:41 | get(...) | PathCreation.java:36:29:36:33 | "dir" |
+| PathCreation.java:36:19:36:41 | get(...) | PathCreation.java:36:36:36:40 | "sub" |
+| PathCreation.java:40:18:40:42 | get(...) | PathCreation.java:40:28:40:41 | new URI(...) |
+| PathCreation.java:44:18:44:56 | getPath(...) | PathCreation.java:44:51:44:55 | "dir" |
+| PathCreation.java:45:19:45:64 | getPath(...) | PathCreation.java:45:52:45:56 | "dir" |
+| PathCreation.java:45:19:45:64 | getPath(...) | PathCreation.java:45:59:45:63 | "sub" |
+| PathCreation.java:49:18:49:31 | of(...) | PathCreation.java:49:26:49:30 | "dir" |
+| PathCreation.java:49:18:49:53 | resolveSibling(...) | PathCreation.java:49:48:49:52 | "sub" |
+| PathCreation.java:53:18:53:31 | of(...) | PathCreation.java:53:26:53:30 | "dir" |
+| PathCreation.java:53:18:53:46 | resolve(...) | PathCreation.java:53:41:53:45 | "sub" |
+| PathCreation.java:57:25:57:45 | new FileWriter(...) | PathCreation.java:57:40:57:44 | "dir" |
+| PathCreation.java:61:25:61:45 | new FileReader(...) | PathCreation.java:61:40:61:44 | "dir" |
+| PathCreation.java:65:32:65:58 | new FileOutputStream(...) | PathCreation.java:65:53:65:57 | "dir" |
+| PathCreation.java:69:31:69:56 | new FileInputStream(...) | PathCreation.java:69:51:69:55 | "dir" |