CVE-2021-21234 (published 2021-01-05T18:15Z)

spring-boot-actuator-logview in a library that adds a simple logfile viewer as spring boot actuator endpoint. It is maven package "eu.hinsch:spring-boot-actuator-logview". In spring-boot-actuator-logview before version 0.2.13 there is a directory traversal vulnerability. The nature of this library is to expose a log file directory via admin (spring boot actuator) HTTP endpoints. Both the filename to view and a base folder (relative to the logging folder root) can be specified via request parameters. While the filename parameter was checked to prevent directory traversal exploits (so that `filename=../somefile` would not work), the base folder parameter was not sufficiently checked, so that `filename=somefile&base=../` could access a file outside the logging base directory). The vulnerability has been patched in release 0.2.13. Any users of 0.2.12 should be able to update without any issues as there are no other changes in that release. There is no workaround to fix the vulnerability other than updating or removing the dependency. However, removing read access of the user the application is run with to any directory not required for running the application can limit the impact. Additionally, access to the logview endpoint can be limited by deploying the application behind a reverse proxy.

Severity: MEDIUM
CVSS v2 base score: 4.0 (AV:N/AC:L/Au:S/C:P/I:N/A:N)
CVSS v3 base score: 7.7, HIGH (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N)

Weakness information:
cwe_id: CWE-22
cwe_name: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
description: The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
extended_description: 
            Many file operations are intended to take place within a restricted directory. By using special elements such as ".." and "/" separators, attackers can escape outside of the restricted location to access files or directories that are elsewhere on the system. One of the most common special elements is the "../" sequence, which in most modern operating systems is interpreted as the parent directory of the current location. This is referred to as relative path traversal. Path traversal also covers the use of absolute pathnames such as "/usr/local/bin" to access unexpected files. This is referred to as absolute path traversal.
         
         

Fix information:
repo_url: https://github.com/lukashinsch/spring-boot-actuator-logview
commit_details: repo_url: https://github.com/lukashinsch/spring-boot-actuator-logview
author: Lukas Hinsch
author_date: 2021-01-01 22:36:07+01:00
msg: backport directory traversal vulnerability fix
repository: repo_url: https://github.com/lukashinsch/spring-boot-actuator-logview
repo_name: lukashinsch/spring-boot-actuator-logview
description: Simple logfile viewer as spring boot actuator endpoint
repo_language: Java
owner: lukashinsch
file_changes: filename: .gitignore
change_type: ModificationType.MODIFY
diff: @@ -2,3 +2,4 @@
 .idea
 *.iml
 build/
+out/

programming_language: Batchfile
filename: .travis.yml
change_type: ModificationType.MODIFY
diff: @@ -1,6 +1,6 @@
 language: java
 jdk:
-  - oraclejdk8
+  - openjdk8
 
 after_success:
   - ./gradlew lib:jacocoTestReport lib:coveralls
\ No newline at end of file

programming_language: Markdown
filename: LogViewEndpoint.java
change_type: ModificationType.MODIFY
diff: @@ -60,9 +60,9 @@ public class LogViewEndpoint implements MvcEndpoint{
                        @RequestParam(required = false, defaultValue = "FILENAME") SortBy sortBy,
                        @RequestParam(required = false, defaultValue = "false") boolean desc,
                        @RequestParam(required = false) String base) throws IOException, TemplateException {
-        securityCheck(base);
-
         Path currentFolder = loggingPath(base);
+        securityCheck(currentFolder, null);
+
 
         List<FileEntry> files = getFileProvider(currentFolder).getFileEntries(currentFolder);
         List<FileEntry> sortedFiles = sortFiles(files, sortBy, desc);
@@ -127,10 +127,10 @@ public class LogViewEndpoint implements MvcEndpoint{
                      @RequestParam(required = false) String base,
                      @RequestParam(required = false) Integer tailLines,
                      HttpServletResponse response) throws IOException {
-        securityCheck(filename);
-        response.setContentType(MediaType.TEXT_PLAIN_VALUE);
 
         Path path = loggingPath(base);
+        securityCheck(path, filename);
+        response.setContentType(MediaType.TEXT_PLAIN_VALUE);
         FileProvider fileProvider = getFileProvider(path);
         if (tailLines != null) {
             fileProvider.tailContent(path, filename, response.getOutputStream(), tailLines);
@@ -171,8 +171,15 @@ public class LogViewEndpoint implements MvcEndpoint{
         }
     }
 
-    private void securityCheck(String filename) {
-        Assert.doesNotContain(filename, "..");
+    private void securityCheck(Path base, String filename) {
+        try {
+            String canonicalLoggingPath = (filename != null ? new File(base.toFile().toString(), filename) : new File(base.toFile().toString())).getCanonicalPath();
+            String baseCanonicalPath = new File(loggingPath).getCanonicalPath();
+            String errorMessage = "File " + base.toString() + "/" + filename + " may not be located outside base path " + loggingPath;
+            Assert.isTrue(canonicalLoggingPath.startsWith(baseCanonicalPath), errorMessage);
+        } catch (IOException e) {
+            throw new IllegalStateException(e);
+        }
     }
 
     @Override

programming_language: Java
filename: LogViewEndpointTest.java
change_type: ModificationType.MODIFY
diff: @@ -330,12 +330,22 @@ public class LogViewEndpointTest {
     public void shouldNotAllowToListFileOutsideRoot() throws Exception {
         // given
         expectedException.expect(IllegalArgumentException.class);
-        expectedException.expectMessage(containsString("this String argument must not contain the substring [..]"));
+        expectedException.expectMessage(containsString("may not be located outside base path"));
 
         // when
         logViewEndpoint.view("../somefile", null, null, null);
     }
 
+    @Test
+    public void shouldNotAllowToListWithBaseOutsideRoot() throws Exception {
+        // given
+        expectedException.expect(IllegalArgumentException.class);
+        expectedException.expectMessage(containsString("may not be located outside base path"));
+
+        // when
+        logViewEndpoint.view("somefile", "../otherdir", null, null);
+    }
+
     @Test
     public void shouldViewFile() throws Exception {
         // given

programming_language: Java
repo_url: https://github.com/lukashinsch/spring-boot-actuator-logview
commit_details: repo_url: https://github.com/lukashinsch/spring-boot-actuator-logview
author: Lukas Hinsch
author_date: 2021-01-01 22:46:05+01:00
msg: Merge pull request #30 from lukashinsch/hotfix/dir-traversal

backport directory traversal vulnerability fix
repository: repo_url: https://github.com/lukashinsch/spring-boot-actuator-logview
repo_name: lukashinsch/spring-boot-actuator-logview
description: Simple logfile viewer as spring boot actuator endpoint
repo_language: Java
owner: lukashinsch