Cis Ubuntu2004 V300 5 4 1 4

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:

# 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