From 3aa8f28db7efb311cdd1b6fe15a9cd3b167a2222 Mon Sep 17 00:00:00 2001
From: Mark Thomas <markt@apache.org>
Date: Tue, 5 May 2020 15:50:15 +0100
Subject: [PATCH] Improve validation of storage location when using FileStore.

---
 .../apache/catalina/session/FileStore.java    | 19 +++++++++++++++++--
 .../catalina/session/LocalStrings.properties  |  1 +
 webapps/docs/changelog.xml                    |  3 +++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/java/org/apache/catalina/session/FileStore.java b/java/org/apache/catalina/session/FileStore.java
index 066d6035f15a..cf3ea880fa8d 100644
--- a/java/org/apache/catalina/session/FileStore.java
+++ b/java/org/apache/catalina/session/FileStore.java
@@ -33,6 +33,8 @@
 import org.apache.catalina.Globals;
 import org.apache.catalina.Session;
 import org.apache.juli.logging.Log;
+import org.apache.juli.logging.LogFactory;
+import org.apache.tomcat.util.res.StringManager;
 
 /**
  * Concrete implementation of the <b>Store</b> interface that utilizes
@@ -43,6 +45,10 @@
  */
 public final class FileStore extends StoreBase {
 
+    private static final Log log = LogFactory.getLog(FileStore.class);
+    private static final StringManager sm = StringManager.getManager(FileStore.class);
+
+
     // ----------------------------------------------------- Constants
 
     /**
@@ -336,11 +342,20 @@ private File directory() throws IOException {
      *    used in the file naming.
      */
     private File file(String id) throws IOException {
-        if (this.directory == null) {
+        File storageDir = directory();
+        if (storageDir == null) {
             return null;
         }
+
         String filename = id + FILE_EXT;
-        File file = new File(directory(), filename);
+        File file = new File(storageDir, filename);
+
+        // Check the file is within the storage directory
+        if (!file.getCanonicalPath().startsWith(storageDir.getCanonicalPath())) {
+            log.warn(sm.getString("fileStore.invalid", file.getPath(), id));
+            return null;
+        }
+
         return file;
     }
 }
diff --git a/java/org/apache/catalina/session/LocalStrings.properties b/java/org/apache/catalina/session/LocalStrings.properties
index 62a8b49ddb8d..127cd438e186 100644
--- a/java/org/apache/catalina/session/LocalStrings.properties
+++ b/java/org/apache/catalina/session/LocalStrings.properties
@@ -29,6 +29,7 @@ JDBCStore.wrongDataSource=Cannot open JNDI DataSource [{0}]
 fileStore.createFailed=Unable to create directory [{0}] for the storage of session data
 fileStore.deleteFailed=Unable to delete file [{0}] which is preventing the creation of the session storage location
 fileStore.deleteSessionFailed=Unable to delete file [{0}] which is no longer required
+fileStore.invalid=Invalid persistence file [{0}] for session ID [{1}]
 fileStore.loading=Loading Session [{0}] from file [{1}]
 fileStore.removing=Removing Session [{0}] at file [{1}]
 fileStore.saving=Saving Session [{0}] to file [{1}]
diff --git a/webapps/docs/changelog.xml b/webapps/docs/changelog.xml
index 479714ce100e..3cb4b574d52d 100644
--- a/webapps/docs/changelog.xml
+++ b/webapps/docs/changelog.xml
@@ -99,6 +99,9 @@
         replacement to <code>:-</code> due to possible conflicts. The
         syntax is now <code>${name:-default}</code>. (remm)
       </fix>
+      <add>
+        Improve validation of storage location when using FileStore. (markt)
+      </add>
     </changelog>
   </subsection>
   <subsection name="Coyote">