Debian 13 – SSH public key login fails due to ~/.ssh permissions – Fix & Prevention

📖 ~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

Key-based authentication fails and administrators lose reliable remote access.

Environment & Reproduction

Often follows account migration or backup restore.

Root Cause Analysis

OpenSSH rejects keys when directory ownership or permissions are too permissive.

Quick Triage

Validate permission chain from home directory to authorized_keys.

Step-by-Step Diagnosis

Inspect effective sshd settings and auth log decisions.

Solution – Primary Fix

Apply strict file permissions and restart ssh service.

Solution – Alternative Approaches

Temporarily enable password auth under change control for emergency access.

Verification & Acceptance Criteria

Public key login succeeds and logs show key acceptance.

Rollback Plan

Restore previous sshd config if emergency changes cause issues.

Prevention & Hardening

Audit SSH permissions during provisioning and periodic checks.

Related Errors & Cross-Refs

Related to disabled PubkeyAuthentication and expired key material.

Related tutorial: View the step-by-step tutorial for Debian 13.

View all Debian 13 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Debian OpenSSH hardening and key management docs.