RHEL 10 SSH Public Key Authentication Suddenly Stops Working

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution — Primary Fix
7. Solution — Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

SSH key login fails, forcing password auth or locking automation out of the host.

Environment & Reproduction

Often appears after home directory migration or hardening edits to sshd_config.

ssh -vvv user@host ; sudo systemctl status sshd

Root Cause Analysis

Wrong file mode, ownership, or SELinux context causes sshd to ignore authorized_keys.

Quick Triage

Inspect sshd logs and verify key auth settings.

sudo journalctl -u sshd -n 100 ; sudo grep -E 'PubkeyAuthentication|AuthorizedKeysFile' /etc/ssh/sshd_config

Step-by-Step Diagnosis

Validate user home perms, authorized_keys ownership, and SELinux labels.

namei -l /home/user/.ssh/authorized_keys ; ls -laZ /home/user/.ssh ; getenforce

Solution — Primary Fix

Repair permissions and contexts, then reload sshd safely.

chmod 700 /home/user/.ssh ; chmod 600 /home/user/.ssh/authorized_keys ; chown -R user:user /home/user/.ssh ; restorecon -Rv /home/user/.ssh ; sudo systemctl reload sshd

Solution — Alternative Approaches

Temporarily enable PasswordAuthentication only during controlled recovery window.

Verification & Acceptance Criteria

Key-based login succeeds and password fallback is disabled per policy.

ssh -o PreferredAuthentications=publickey user@host true ; sudo sshd -t

Rollback Plan

Restore previous sshd_config and authorized_keys backup if regressions occur.

sudo cp /etc/ssh/sshd_config.bak /etc/ssh/sshd_config ; sudo systemctl restart sshd

Prevention & Hardening

Use config management to enforce ssh file perms and regularly run sshd config tests.

Related Errors & Cross-Refs

May coincide with SELinux AVC denials and SSSD home directory mapping issues.

Related tutorial: View the step-by-step tutorial for rhel-10.

View all rhel-10 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

OpenSSH hardening guides and RHEL security baseline recommendations.