From d9841a2fb2495cac839d58d3d6a42f3dab4a4598 Mon Sep 17 00:00:00 2001 From: Jonathan Leitschuh Date: Mon, 3 Oct 2022 21:25:35 +0000 Subject: [PATCH] vuln-fix: Zip Slip Vulnerability This fixes a Zip-Slip vulnerability. This change does one of two things. This change either 1. Inserts a guard to protect against Zip Slip. OR 2. Replaces `dir.getCanonicalPath().startsWith(parent.getCanonicalPath())`, which is vulnerable to partial path traversal attacks, with the more secure `dir.getCanonicalFile().toPath().startsWith(parent.getCanonicalFile().toPath())`. For number 2, consider `"/usr/outnot".startsWith("/usr/out")`. The check is bypassed although `/outnot` is not under the `/out` directory. It's important to understand that the terminating slash may be removed when using various `String` representations of the `File` object. For example, on Linux, `println(new File("/var"))` will print `/var`, but `println(new File("/var", "/")` will print `/var/`; however, `println(new File("/var", "/").getCanonicalPath())` will print `/var`. Weakness: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') Severity: High CVSSS: 7.4 Detection: CodeQL (https://codeql.github.com/codeql-query-help/java/java-zipslip/) & OpenRewrite (https://public.moderne.io/recipes/org.openrewrite.java.security.ZipSlip) Reported-by: Jonathan Leitschuh Signed-off-by: Jonathan Leitschuh Bug-tracker: https://github.com/JLLeitschuh/security-research/issues/16 Co-authored-by: Moderne --- src/org/loklak/LoklakServer.java | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/src/org/loklak/LoklakServer.java b/src/org/loklak/LoklakServer.java index b9c49136c..54156833b 100644 --- a/src/org/loklak/LoklakServer.java +++ b/src/org/loklak/LoklakServer.java @@ -374,7 +374,10 @@ private static void extractContents() { private static void extract(JarFile jar, JarEntry file) throws IOException { Path workingDirectory = Paths.get("").toAbsolutePath(); - File target = new File(workingDirectory.toString() + File.separator + file.getName()); + File target = new File(workingDirectory.toString(), file.getName()); + if (!target.toPath().normalize().startsWith(workingDirectory.toString())) { + throw new IOException("Bad zip entry"); + } if (target.exists()) return;