rspec/rules/S4639/java/rule.adoc

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== Noncompliant Code Example

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Enumeration<? extends ZipEntry> entries = zipFile.entries();
while (entries.hasMoreElements()) {
  ZipEntry entry = entries.nextElement();
  File extractedFile = new File(toDir, entry.getName()); 

  FileOutputStream fos = new FileOutputStream(extractedFile); // Noncompliant; entry.getName() that was used to created "extractedFile" may be tainted with "../../../../../../../../tmp/evil.sh"
  InputStream input = zipFile.getInputStream(entry);
  IOUtils.copy(input, fos);
}
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== Compliant Solution

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Enumeration<? extends ZipEntry> entries = zipFile.entries();
while (entries.hasMoreElements()) {
  ZipEntry zipEntry = entries.nextElement();
  String fileName = zipEntry.getName();
  File extractedFile = new File(toDir, fileName);

  String canonicalDirPath = toDir.getCanonicalPath();
  String canonicalDestPath = extractedFile.getCanonicalPath();

  sanitizeAgainstZipFlipVulnerability(fileName, canonicalDestPath, canonicalDirPath); // Compliant

  FileOutputStream fos = new FileOutputStream(extractedFile);
  InputStream input = zipFile.getInputStream(entry);
  IOUtils.copy(input, fos);
}

public static void sanitizeAgainstZipFlipVulnerability(String fileName, String canonicalDestPath, String canonicalDirPath) throws ArchiverException {
    if (fileName.indexOf("..") != -1 && !canonicalDestPath.startsWith(canonicalDirPath + File.separator)) { // Sanitizer
      throw new ArchiverException("The file " + fileName + " is trying to leave the target output directory.");
    }
  }
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== Comments And Links
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