Cis Ubuntu2004 V300 5 4 1 4

---
name: cis-ubuntu2004-v300-5-4-1-4
description: "Ensure strong password hashing algorithm is configured"
category: cis-iam
version: "3.0.0"
author: cyberstrike-official
tags: [cis, ubuntu, linux, ubuntu-20.04, users, authentication]
cis_id: "5.4.1.4"
cis_benchmark: "CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0"
tech_stack: [ubuntu, linux]
cwe_ids: []
chains_with: []
prerequisites: []
severity_boost: {}
---

# 5.4.1.4 Ensure strong password hashing algorithm is configured (Automated)

## Profile

- Level 1 - Server
- Level 1 - Workstation

## Description

A cryptographic hash function converts an arbitrary-length input into a fixed length output. Password hashing performs a one-way transformation of a password, turning the password into another string, called the hashed password.

`ENCRYPT_METHOD` (string) - This defines the system default encryption algorithm for encrypting passwords (if no algorithm are specified on the command line). It can take one of these values:

- `MD5` - MD5-based algorithm will be used for encrypting password
- `SHA256` - SHA256-based algorithm will be used for encrypting password
- `SHA512` - SHA512-based algorithm will be used for encrypting password
- `BCRYPT` - BCRYPT-based algorithm will be used for encrypting password
- `YESCRYPT` - YESCRYPT-based algorithm will be used for encrypting password
- `DES` - DES-based algorithm will be used for encrypting password (default)

Note:

- This parameter overrides the deprecated `MD5_CRYPT_ENAB` variable.
- This parameter will only affect the generation of group passwords.
- The generation of user passwords is done by PAM and subject to the PAM configuration.
- It is recommended to set this variable consistently with the PAM configuration.

## Rationale

The `SHA-512` and `yescrypt` algorithms provide a stronger hash than other algorithms used by Linux for password hash generation. A stronger hash provides additional protection to the system by increasing the level of effort needed for an attacker to successfully determine local group passwords.

## Audit Procedure

### Command Line

Run the following command to verify the hashing algorithm is `sha512` or `yescrypt` in `/etc/login.defs`:

```bash
# grep -Pi -- '^\h*ENCRYPT_METHOD\h+(SHA512|yescrypt)\b' /etc/login.defs
```

Example output:

```
ENCRYPT_METHOD SHA512
- OR -
ENCRYPT_METHOD   YESCRYPT
```

## Expected Result

Output should show `ENCRYPT_METHOD` set to `SHA512` or `YESCRYPT`.

## Remediation

### Command Line

Edit `/etc/login.defs` and set the `ENCRYPT_METHOD` to `SHA512` or `YESCRYPT`:

```
ENCRYPT_METHOD <HASHING_ALGORITHM>
```

Example:

```
ENCRYPT_METHOD YESCRYPT
```

Note:

- This only effects local groups' passwords created after updating the file to use `sha512` or `yescrypt`.
- If it is determined that the password algorithm being used is not `sha512` or `yescrypt`, once it is changed, it is recommended that all group passwords be updated to use the stronger hashing algorithm.
- It is recommended that the chosen hashing algorithm is consistent across `/etc/login.defs` and the PAM configuration

## Default Value

ENCRYPT_METHOD SHA512

## References

1. NIST SP 800-53 Rev. 5: IA-5

## CIS Controls

v8 - 3.11 Encrypt Sensitive Data at Rest: Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, meets the minimum requirement of this Safeguard. Additional encryption methods may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. (IG 2, IG 3)

v7 - 16.4 Encrypt or Hash all Authentication Credentials: Encrypt or hash with a salt all authentication credentials when stored. (IG 2, IG 3)

MITRE ATT&CK Mappings: T1003, T1003.008, T1110, T1110.002 - Tactics: TA0006 - Mitigations: M1041