How to Fix Linux SSH Key Permissions Too Open Error

In this tutorial, you'll learn about How to Fix Linux SSH Key Permissions Too Open Error. We cover key concepts, practical examples, and best practices.

You try to SSH with a key and get Permissions 0644 for 'id_rsa' are too open — SSH refuses to use a private key that is accessible by other users.

The Problem

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @
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Permissions 0644 for '/home/user/.ssh/id_rsa' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.

Step-by-Step Fix

Step 1: Fix private key permissions

# WRONG — readable by all
-rw-r--r-- 1 user user 2602 Jun 24 10:00 id_rsa

# RIGHT — owner read-only
chmod 600 ~/.ssh/id_rsa

Verify:

ls -la ~/.ssh/id_rsa

Expected:

-rw------- 1 user user 2602 Jun 24 10:00 id_rsa

Step 2: Fix public key permissions

Public keys can be more permissive:

chmod 644 ~/.ssh/id_rsa.pub

Step 3: Fix .ssh directory permissions

# WRONG — group/world writable
chmod 777 ~/.ssh

# RIGHT — owner only
chmod 700 ~/.ssh

Step 4: Fix authorized_keys permissions

chmod 600 ~/.ssh/authorized_keys
chmod 700 ~/.ssh

Step 5: Fix home directory permissions

Your home directory should not be writable by others:

chmod 755 ~

Step 6: Verify all permissions

ls -la ~/.ssh/

Expected:

drwx------  2 user user 4096 Jun 24 10:00 .
-rw-------  1 user user 2602 Jun 24 10:00 id_rsa
-rw-r--r--  1 user user  573 Jun 24 10:00 id_rsa.pub
-rw-------  1 user user 1024 Jun 24 10:00 authorized_keys

Prevention Tips

• Always run chmod 600 ~/.ssh/id_rsa after generating keys
• Never share private key files with other users
• Use ssh-keygen -t ed25519 for newer key types
• Set umask to 077 before creating keys
• Use ssh-agent to manage keys securely

Common Mistakes with ssh key permission

1. Misunderstanding that String is [Char] with poor performance for large text operations
2. Using foldl instead of foldl' causing stack overflow on large lists
3. Forgetting deriving (Show, Eq) on custom data types needed for debugging

These mistakes appear frequently in real-world LINUX code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

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