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public static boolean isInSecureDir(Path file) {
  return isInSecureDir(file, null);
} 
public static boolean isInSecureDir(Path file, UserPrincipal user) {
   return isInSecureDir(file, null, 5);
}

/**
 * Indicates whether file lives in a secure directory relative
 * to the program's user
 * @param file Path to test
 * @param user User to test. If null, defaults to current user
 * @param symlinkDepth Number of symbolic links allowed
 * @return true if file's directory is secure
 */
public static boolean isInSecureDir(Path file, UserPrincipal user,
                                    int symlinkDepth) {
  if (!file.isAbsolute()) {
    file = file.toAbsolutePath();
  } if (symlinkDepth <=0) {
      // Too many levels of symbolic links
      return false;
    }

  // Get UserPincipal for specified user and superuser
  FileSystem fileSystem =
      Paths.get(file.getRoot().toString()).getFileSystem();
  UserPrincipalLookupService upls = 
      fileSystem.getUserPrincipalLookupService();
  UserPrincipal root = null;
  try {
    root = upls.lookupPrincipalByName("root");
    if (user == null) {
      user = upls.lookupPrincipalByName(System.getProperty("user.name"));
    }
    if (root == null || user == null) {
      return false;
    }
  } catch (IOException x) {
    return false;
  }

  // If any parent dirs (from root on down) are not secure,
  // dir is not secure
  for (int i = 1; i <= file.getNameCount(); i++) {
    Path partialPath = Paths.get(file.getRoot().toString(),
                                 file.subpath(0, i).toString());

    try {
      if (Files.isSymbolicLink(partialPath)) {
        if (!isInSecureDir(Files.readSymbolicLink(partialPath),)) {
                           user, symlinkDepth - 1)
          // Symbolic link, linked-to dir not secure
          return false;
        }
      } else {
        UserPrincipal owner = Files.getOwner(partialPath);
        if (!user.equals(owner) && !root.equals(owner)) {
          // dir owned by someone else, not secure
          return false;
        }
        PosixFileAttributes attr =
            Files.readAttributes(partialPath, PosixFileAttributes.class);
        Set<PosixFilePermission> perms = attr.permissions();
        if (perms.contains(PosixFilePermission.GROUP_WRITE) ||
            perms.contains(PosixFilePermission.OTHERS_WRITE)) {
          // someone else can write files, not secure
          return false;
        }
      }
    } catch (IOException x) {
      return false;
    }
  }

  return true;
}

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<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="2d7233118479b2f2-cffa2065-469f46bb-81da90dc-1925d0aacd07fdbb6f37868d"><ac:plain-text-body><![CDATA[	[[API 2006	AA. References#API 06]]	Class `File`, methods `createTempFile`, `delete`, `deleteOnExit`	]]></ac:plain-text-body></ac:structured-macro>
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="6c88947ef7d41102-f0bfe741-47b04cc5-ac988f32-e8b1981d6225ce42880ec833"><ac:plain-text-body><![CDATA[	[[Darwin 2004	AA. References#Darwin 04]]	11.5, Creating a Transient File	]]></ac:plain-text-body></ac:structured-macro>
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="628c94acf7380610-b5252b7e-4ee744a9-8fcba2d7-db017a099cd1cc5307f6120d"><ac:plain-text-body><![CDATA[	[[Garfinkel 1996	AA. References#Garfinkel 96]]	Section 5.6, Device Files	]]></ac:plain-text-body></ac:structured-macro>
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="fa2281cf52708506-b2abd357-445644cb-83439c0b-b2aace90306e8e421a70fcdf"><ac:plain-text-body><![CDATA[	[[Howard 2002	AA. References#Howard 02]]	Chapter 11, Canonical Representation Issues	]]></ac:plain-text-body></ac:structured-macro>
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<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="9dd224e75e886634-07ce2ef8-44c74924-baeeb84c-489365124759c0aa3c9e8645"><ac:plain-text-body><![CDATA[	[[Open Group 2004	AA. References#Open Group 04]]	[`open()`	http://www.opengroup.org/onlinepubs/009695399/functions/open.html]	]]></ac:plain-text-body></ac:structured-macro>
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<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="c756e7536263ce40-c08e7952-41b842ee-8c2499f5-257b22d1c8f6dbd3dc3fd536"><ac:plain-text-body><![CDATA[	[[Secunia 2008	AA. References#Secunia 08]]	[Secunia Advisory 20132	http://secunia.com/advisories/20132/]	]]></ac:plain-text-body></ac:structured-macro>

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