If you SSH to a Linux machine and encounter the following error:
lyle@lyle-laptop:~/Downloads$ ssh -i key-test.pem [email protected]
Permissions 0640 for 'key-test.pem' are too open. It is required that your private key files are NOT accessible by others. This private key will be ignored.
-rw-r----- 1 lyle lyle 1696 Jan 12 14:06 key-test.pem
-rw------- 1 lyle lyle 1771 Jan 23 10:09 key-prod.pem
Now notice that the permissions for key-test.pem is 640 and the permissions for key-prod.pem is 600
If I was to SSH to a certain box using the key-test.pem it would give me the error above in the first line of this post. If I was to use the key-prod.pem and it is a valid key on that system then it would login without any problems.
To solve this we change the permission of the key file.
lyle@lyle-laptop:~/Downloads$ chmod 600 key-test.pem
Check the permissions
-rw------- 1 lyle lyle 1696 Jan 12 14:06 key-test.pem
-rw------- 1 lyle lyle 1771 Jan 23 10:09 key-prod.pem
Now you would be able to SSH without any problem.
Just for reference in case you need. A little handy table.
| Numeric Value | Permission | Plain English |
|---|---|---|
| 7 | 4+2+1 | (read/write/execute) |
| 6 | 4+2 | (read/write) |
| 5 | 4+1 | (read/execute) |
| 4 | 4 | (read) |
| 3 | 2+1 | (write/execute) |
| 2 | 2 | (write) |
| 1 | 1 | (execute) |