cis-ubuntu2004-v300-7-1-5

DevOps & Security

Ensure access to /etc/shadow is configured

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_20.04_LTS_Benchmark_v3.0.0/cis-ubuntu2004-v300-7-1-5/SKILL.md

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7.1.5 Ensure access to /etc/shadow is configured (Automated)

Profile

Level 1 - Server
Level 1 - Workstation

Description

The /etc/shadow file is used to store the information about user accounts that is critical to the security of those accounts, such as the hashed password and other security information.

Rationale

If attackers can gain read access to the /etc/shadow file, they can easily run a password cracking program against the hashed password to break it. Other security information that is stored in the /etc/shadow file (such as expiration) could also be useful to subvert the user accounts.

Impact

None

Audit Procedure

Command Line

Run the following command to verify /etc/shadow is mode 640 or more restrictive, Uid is 0/root and Gid is 0/root or {GID}/shadow:

# stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/shadow

Example:

Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow)

Expected Result

Mode 640 or more restrictive, Uid 0/root, Gid 0/root or {GID}/shadow.

Remediation

Command Line

Run one of the following commands to set ownership of /etc/shadow to root and group to either root or shadow:

# chown root:shadow /etc/shadow
  -OR-
# chown root:root /etc/shadow

Run the following command to remove excess permissions from /etc/shadow:

# chmod u-x,g-wx,o-rwx /etc/shadow

Default Value

Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow)

References

NIST SP 800-53 Rev. 5: AC-3. MP-2

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	3.3 Configure Data Access Control Lists	X	X	X
v7	14.6 Protect Information through Access Control Lists	X	X	X

MITRE ATT&CK Mappings:

Techniques / Sub-techniques	Tactics	Mitigations
T1003, T1003.008, T1222, T1222.002	TA0005	M1022