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[SECURITY] Fix Zip Slip Vulnerability #1

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[SECURITY] Fix Zip Slip Vulnerability #1

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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 <Jonathan.Leitschuh@gmail.com>
Signed-off-by: Jonathan Leitschuh <Jonathan.Leitschuh@gmail.com>

Bug-tracker: JLLeitschuh/security-research#16


Co-authored-by: Moderne <team@moderne.io>
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@JLLeitschuh @TeamModerne
JLLeitschuh and TeamModerne committed Oct 3, 2022
commit 83e8eaf0b4aecc16a6e7f60240cd67125c05868a
6 changes: 2 additions & 4 deletions src/main/java/org/apache/catalina/startup/ExpandWar.java
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Original file line number Diff line number Diff line change
Expand Up @@ -134,8 +134,7 @@ public static String expand(Host host, URL war, String pathname)
JarEntry jarEntry = jarEntries.nextElement();
String name = jarEntry.getName();
File expandedFile = new File(docBase, name);
if (!expandedFile.getCanonicalPath().startsWith(
canonicalDocBasePrefix)) {
if (!expandedFile.getCanonicalFile().toPath().startsWith(canonicalDocBasePrefix)) {
// Trying to expand outside the docBase
// Throw an exception to stop the deployment
throw new IllegalArgumentException(
Expand Down Expand Up @@ -220,8 +219,7 @@ public static void validate(Host host, URL war, String pathname) throws IOExcept
JarEntry jarEntry = jarEntries.nextElement();
String name = jarEntry.getName();
File expandedFile = new File(docBase, name);
if (!expandedFile.getCanonicalPath().startsWith(
canonicalDocBasePrefix)) {
if (!expandedFile.getCanonicalFile().toPath().startsWith(canonicalDocBasePrefix)) {
// Entry located outside the docBase
// Throw an exception to stop the deployment
throw new IllegalArgumentException(
Expand Down