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vuln-fix: Zip Slip Vulnerability
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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 <[email protected]>
Signed-off-by: Jonathan Leitschuh <[email protected]>

Bug-tracker: JLLeitschuh/security-research#16

Co-authored-by: Moderne <[email protected]>
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JLLeitschuh and TeamModerne committed Sep 23, 2022
1 parent 162d3dc commit 4a7f5f1
Showing 1 changed file with 8 additions and 1 deletion.
Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,10 @@ public static void unZipIt(String zipFilePath, String outputFolder) {
ZipEntry ze = zis.getNextEntry();
while (ze != null) {
String fileName = ze.getName();
File newFile = new File(outputFolder + File.separator + fileName);
File newFile = new File(outputFolder,fileName);
if (!newFile.toPath().normalize().startsWith(outputFolder)) {
throw new IOException("Bad zip entry");
}
System.out.println("file unzip : " + newFile.getAbsoluteFile());
//大部分网络上的源码,这里没有判断子目录
if (ze.isDirectory()) {
Expand Down Expand Up @@ -83,6 +86,10 @@ public static void unzip(File source, String out) throws IOException {

File file = new File(out, entry.getName());

if (!file.toPath().normalize().startsWith(out)) {
throw new IOException("Bad zip entry");
}

if (entry.isDirectory()) {
if (!file.mkdirs()) {
System.out.println("was not successful.");
Expand Down

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