SSH Key Authentication Fails Despite Correct Key

📖 ~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 falls back to password auth or denies access when key login is expected.

Environment & Reproduction

Run `ssh -vvv` from client and validate server-side `~/.ssh` permissions and ownership.

Root Cause Analysis

Confirm `openssh-server` and `openssh-clients` versions are supported on RHEL 9 baseline.

Quick Triage

Use `systemctl status sshd` and inspect effective settings with `sshd -T`.

Step-by-Step Diagnosis

Check `journalctl -u sshd` for pubkey rejection reason and auth method negotiation.

Solution – Primary Fix

Backup `/etc/ssh/sshd_config` and included drop-ins before policy changes.

Solution – Alternative Approaches

Confirm port exposure with `firewall-cmd –list-services` and route-level reachability.

Verification & Acceptance Criteria

Verify user home context and `.ssh` labels with `restorecon -Rv ~/.ssh`.

Rollback Plan

Set strict file permissions, correct authorized_keys format, and reload sshd service.

Prevention & Hardening

Retest key authentication and confirm password fallback is no longer required.

Related Errors & Cross-Refs

Automate account onboarding with standardized SSH policy and compliance checks.

Related tutorial: View the step-by-step tutorial for rhel-9.

View all rhel-9 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Provide verbose client trace and sshd journal entries with redacted identifiers.