Duplicate User IDs (UIDs) must not exist for interactive users.

From Canonical Ubuntu 16.04 LTS Security Technical Implementation Guide

Part of SRG-OS-000104-GPOS-00051

Associated with: CCI-000764 CCI-000804 CCI-001084

SV-90227r2_rule Duplicate User IDs (UIDs) must not exist for interactive users.

Vulnerability discussion

To assure accountability and prevent unauthenticated access, interactive users must be identified and authenticated to prevent potential misuse and compromise of the system.Interactive users include organizational employees or individuals the organization deems to have equivalent status of employees (e.g., contractors). Interactive users (and processes acting on behalf of users) must be uniquely identified and authenticated to all accesses, except for the following: 1) Accesses explicitly identified and documented by the organization. Organizations document specific user actions that can be performed on the information system without identification or authentication; and2) Accesses that occur through authorized use of group authenticators without individual authentication. Organizations may require unique identification of individuals in group accounts (e.g., shared privilege accounts) or for detailed accountability of individual activity.Satisfies: SRG-OS-000104-GPOS-00051, SRG-OS-000121-GPOS-00062, SRG-OS-000134-GPOS-00068

Check content

Verify that the Ubuntu operating system contains no duplicate User IDs (UIDs) for interactive users. Check that the Ubuntu operating system contains no duplicate UIDs for interactive users with the following command: # awk -F ":" 'list[$3]++{print $1, $3}' /etc/passwd If output is produced, and the accounts listed are interactive user accounts, this is a finding.

Fix text

Edit the file "/etc/passwd" and provide each interactive user account that has a duplicate User ID (UID) with a unique UID.

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