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Excessive privileges - Access Mode

Need​

Restrict access privileges to system files and directories

Context​

  • Usage of Scala for building scalable and high-performance applications
  • Usage of java.nio.file.Paths for working with file paths in Java
  • Usage of java.nio.file.Files for file operations in Java
  • Usage of PosixFilePermission for managing file permissions in Java's java.nio.file.attribute package
  • Usage of scala.collection.JavaConverters for converting Java collections to Scala collections and vice versa

Description​

Non compliant code​

import java.nio.file.{Paths, Files}
import java.nio.file.attribute.PosixFilePermission
import scala.collection.JavaConverters._

val path = Paths.get("/tmp/myfile")
val perms = Set(PosixFilePermission.OWNER_READ, PosixFilePermission.OWNER_WRITE, PosixFilePermission.OWNER_EXECUTE, PosixFilePermission.GROUP_READ, PosixFilePermission.GROUP_WRITE, PosixFilePermission.GROUP_EXECUTE, PosixFilePermission.OTHERS_READ, PosixFilePermission.OTHERS_WRITE, PosixFilePermission.OTHERS_EXECUTE).asJava
Files.createFile(path, perms)

The above Scala code is creating a file at the path "/tmp/myfile" with all permissions set to all categories of users - owner, group, and others. This means that any user, regardless of their role or group, can read, write, and execute this file.

The line val perms = Set(PosixFilePermission.OWNER_READ, PosixFilePermission.OWNER_WRITE, PosixFilePermission.OWNER_EXECUTE, PosixFilePermission.GROUP_READ, PosixFilePermission.GROUP_WRITE, PosixFilePermission.GROUP_EXECUTE, PosixFilePermission.OTHERS_READ, PosixFilePermission.OTHERS_WRITE, PosixFilePermission.OTHERS_EXECUTE).asJava is where the permissions are being set.

This is a security vulnerability known as "Excessive Privileges" where the access control is too permissive. It can lead to unauthorized access, data leaks, or even data loss if a malicious user gains access to the system.

It's important to follow the principle of least privilege where users are given the minimum levels of access – or permissions – that they need to complete their work tasks. This helps to reduce the attack surface of the system and the potential for damage.

Steps​

  • Review the access mode permissions required for the file or directory.
  • Determine the minimum necessary access mode permissions needed for the file or directory.
  • Modify the code to set the access mode permissions to the minimum necessary permissions.
  • Test the modified code to ensure it functions correctly.
  • Repeat the process for any other files or directories with excessive access mode permissions.

Compliant code​

import java.nio.file.{Paths, Files}
import java.nio.file.attribute.PosixFilePermission
import scala.collection.JavaConverters._

val path = Paths.get("/tmp/myfile")
val perms = Set(PosixFilePermission.OWNER_READ, PosixFilePermission.OWNER_WRITE, PosixFilePermission.GROUP_READ).asJava
Files.createFile(path, perms)

The original code was creating a file with excessive permissions, allowing the owner, group, and others to read, write, and execute the file. This is a security vulnerability as it allows unauthorized users to potentially read sensitive data, modify the file, or execute arbitrary code.

The fixed code reduces the permissions to the minimum necessary. In this case, the owner has read and write permissions, and the group has read permissions. This means that the owner can read and modify the file, while the group can only read the file. Other users have no permissions, so they cannot interact with the file in any way.

This change ensures that only authorized users can interact with the file in the intended ways, reducing the risk of unauthorized access or modification. It's important to always follow the principle of least privilege when setting file permissions, giving users only the permissions they need to perform their tasks and no more. This helps to minimize the potential damage if a user's account is compromised.

Remember to test the modified code to ensure it still functions as expected. Also, review the permissions of any other files or directories in your application to ensure they are also set to the minimum necessary permissions.

References​

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