key_load_public: invalid format

I used PuTTY Key Generator to generate a 4096 bit RSA-2 key with a passphrase.

I save the .ppk and an openSSL format public key. The putty format public key doesn't work.

In any case, my error is as follows:

$ ssh -T [email protected]
key_load_public: invalid format
Enter passphrase for key '/c/Users/Dan/.ssh/id_rsa':
Hi Dan! You've successfully authenticated, but GitHub does not provide shell access.

What's the issue?

I use Pageant to load the keys and i use Git Bash to try the ssh connection. I've also loaded the key into GitHub, not sure what i'm doing wrong.

I've tried adding a new line and not adding a new line in GitHub

As Roland mentioned in their answer, it's a warning that the ssh-agent doesn't understand the format of the public key and even then, the public key will not be used locally.

However, I can also elaborate and answer why the warning is there. It simply boils down to the fact that the PuTTY Key Generator generates two different public key formats depending on what you do in the program.

Note: Throughout my explanation, the key files I will be using/generating will be named id_rsa with their appropriate extensions. Furthermore, for copy-paste convenience, the parent folder of the keys will be assumed to be ~/.ssh/. Adjust these details to suit your needs as desired.

The Formats

Link to the relevant PuTTY documentation

SSH-2

When you save a key using the PuTTY Key Generator using the "Save public key" button, it will be saved in the format defined by RFC 4716.

Example:

---- BEGIN SSH2 PUBLIC KEY ----
Comment: "github-example-key"
AAAAB3NzaC1yc2EAAAABJQAAAQEAhl/CNy9wI1GVdiHAJQV0CkHnMEqW7+Si9WYF
i2fSBrsGcmqeb5EwgnhmTcPgtM5ptGBjUZR84nxjZ8SPmnLDiDyHDPIsmwLBHxcp
pY0fhRSGtWL5fT8DGm9EfXaO1QN8c31VU/IkD8niWA6NmHNE1qEqpph3DznVzIm3
oMrongEjGw7sDP48ZTZp2saYVAKEEuGC1YYcQ1g20yESzo7aP70ZeHmQqI9nTyEA
ip3mL20+qHNsHfW8hJAchaUN8CwNQABJaOozYijiIUgdbtSTMRDYPi7fjhgB3bA9
tBjh7cOyuU/c4M4D6o2mAVYdLAWMBkSoLG8Oel6TCcfpO/nElw==
---- END SSH2 PUBLIC KEY ----

OpenSSH

Contrary to popular belief, this format doesn't get saved by the generator. However it is generated and shown in the text box titled "Public key for pasting into OpenSSH authorized_keys file". To save it as a file, you have to manually copy it from the text box and paste it into a new text file.

For the key shown above, this would be:

ssh-rsa AAAAB3NzaC1yc2EAAAABJQAAAQEAhl/CNy9wI1GVdiHAJQV0CkHnMEqW7+Si9WYFi2fSBrsGcmqeb5EwgnhmTcPgtM5ptGBjUZR84nxjZ8SPmnLDiDyHDPIsmwLBHxcppY0fhRSGtWL5fT8DGm9EfXaO1QN8c31VU/IkD8niWA6NmHNE1qEqpph3DznVzIm3oMrongEjGw7sDP48ZTZp2saYVAKEEuGC1YYcQ1g20yESzo7aP70ZeHmQqI9nTyEAip3mL20+qHNsHfW8hJAchaUN8CwNQABJaOozYijiIUgdbtSTMRDYPi7fjhgB3bA9tBjh7cOyuU/c4M4D6o2mAVYdLAWMBkSoLG8Oel6TCcfpO/nElw== github-example-key

The format of the key is simply ssh-rsa <signature> <comment> and can be created by rearranging the SSH-2 formatted file.

Regenerating Public Keys

If you are making use of ssh-agent, you will likely also have access to ssh-keygen.

If you have your OpenSSH Private Key (id_rsa file), you can generate the OpenSSH Public Key File using:

ssh-keygen -f ~/.ssh/id_rsa -y > ~/.ssh/id_rsa.pub

If you only have the PUTTY Private Key (id_rsa.ppk file), you will need to convert it first.

1. Open the PuTTY Key Generator
2. On the menu bar, click "File" > "Load private key"
3. Select your id_rsa.ppk file
4. On the menu bar, click "Conversions" > "Export OpenSSH key"
5. Save the file as id_rsa (without an extension)

Now that you have an OpenSSH Private Key, you can use the ssh-keygen tool as above to perform manipulations on the key.

Bonus: The PKCS#1 PEM-encoded Public Key Format

To be honest, I don't know what this key is used for as I haven't needed it. But I have it in my notes I've collated over the years and I'll include it here for wholesome goodness. The file will look like this:

-----BEGIN RSA PUBLIC KEY-----
MIIBCAKCAQEAhl/CNy9wI1GVdiHAJQV0CkHnMEqW7+Si9WYFi2fSBrsGcmqeb5Ew
gnhmTcPgtM5ptGBjUZR84nxjZ8SPmnLDiDyHDPIsmwLBHxcppY0fhRSGtWL5fT8D
Gm9EfXaO1QN8c31VU/IkD8niWA6NmHNE1qEqpph3DznVzIm3oMrongEjGw7sDP48
ZTZp2saYVAKEEuGC1YYcQ1g20yESzo7aP70ZeHmQqI9nTyEAip3mL20+qHNsHfW8
hJAchaUN8CwNQABJaOozYijiIUgdbtSTMRDYPi7fjhgB3bA9tBjh7cOyuU/c4M4D
6o2mAVYdLAWMBkSoLG8Oel6TCcfpO/nElwIBJQ==
-----END RSA PUBLIC KEY-----

This file can be generated using an OpenSSH Private Key (as generated in "Regenerating Public Keys" above) using:

ssh-keygen -f ~/.ssh/id_rsa -y -e -m pem > ~/.ssh/id_rsa.pem

Alternatively, you can use an OpenSSH Public Key using:

ssh-keygen -f ~/.ssh/id_rsa.pub -e -m pem > ~/.ssh/id_rsa.pem

##References:##

• "key_load_public: invalid format..." on AskUbuntu
• The Secure Shell (SSH) Public Key File Format
• Converting OpenSSH public keys

There is a simple solution if you can install and use puttygen tool. Below are the steps. You should have the passphrase of the private key.

step 1: Download latest puttygen and open puttygen

step 2: Load your existing private key file, see below image

step 3: Enter passphrase for key if asked and hit ok

step 4: as shown in the below image select "conversion" menu tab and select "Export OpenSSH key"

Save new private key file at preferred location and use accordingly.

TL;DR: also ensure that your id_rsa.pub is in ascii / UTF-8.

I had the same problem, however the accepted answer alone did not work because of the text encoding, which was an additional, easy-to-miss issue.

When I run

ssh-keygen -f ~/.ssh/id_rsa -y > ~/.ssh/id_rsa.pub

in Windows PowerShell, it saves the output to id_rsa.pub in UTF-16 LE BOM encoding, not in UTF-8. This is a property of some installations of PowerShell, which was discussed in Using PowerShell to write a file in UTF-8 without the BOM. Apparently, OpenSSH does not recognise the former text encoding and produces an identical error:

key_load_public: invalid format

Copying and pasting the output of ssh-keygen -f ~/.ssh/id_rsa -y into a text editor is the simplest way to solve this.

P.S. This could be an addition to the accepted answer, but I don't have enough karma to comment here yet.

In the case you copy your public key with clipboard and paste it, it may happen the public key string can be broken which contains new-line.

Make sure your public key string formed as one line.

It seems that ssh cannot read your public key. But that doesn't matter.

You upload your public key to github, but you authenticate using your private key. See e.g. the FILES section in ssh(1).

Generate id_rsa and id_rsa.pub files using the below command :

ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

Then :

1) Place file in id_rsa.pub into ~/.ssh/id_rsa.pub

2) sudo chmod 600 ~/.ssh/id_rsa.pub

3) Place file id_rsa into ~/.ssh/id_rsa

Now ~/.ssh contains two files..~/.ssh/id_rsa.pub and ~/.ssh/id_rsa

4) ssh-add  ~/.ssh/id_rsa

5) Enter the passphrase entered during creation of id_rsa

Output :

Identity added: /home/jay/.ssh/id_rsa (/home/jay/.ssh/id_rsa)

Now you can push pull without entering username password

The error is misleading - it says "pubkey" while pointing to a private key file ~/.ssh/id_rsa.

In my case, it was simply a missing public key (as I haven't restored it from a vault).

---

DETAILS

I used to skip deploying ~/.ssh/id_rsa.pub by automated scripts.

All ssh usages worked, but the error made me think of a possible mess.

Not at all - strace helped to notice that the trigger was actually the *.pub file:

strace ssh example.com
...
openat(AT_FDCWD, "/home/uvsmtid/.ssh/id_rsa.pub", O_RDONLY) = -1 ENOENT (No such file or directory)
...
write(2, "load pubkey \"/home/uvsmtid/.ssh/"..., 57) = 57
load pubkey "/home/uvsmtid/.ssh/id_rsa": invalid format

Instead of directly saving the private key Go to Conversions and Export SSh Key. Had the same issue and this worked for me

I had the same warning. It was a very old key. I regenerated a key on the current OpenSSH 7, and the error was gone.

If you're using Windows 10 with the built-in SSH, as of August 2020 it only supports ed25519 keys. You'll get the key_load_public: invalid format error if you use e.g. an RSA key.

As per this GitHub issue it should be fixed via Windows Update some time in 2020. So one solution is to just wait for the update to ship.

If you can't wait, a workaround is to generate a new ed25519 key, which is good advice anyway.

> ssh-keygen -o -a 100 -t ed25519

You can use it with e.g. github, but some older systems might not support this newer format.

After generating your key, if you're using either of the below features, don't forget to update them!

1. ~\.ssh\config might still point to the old key.
2. Add the new key to ssh-agent via the ssh-add command

Adding SSH-KEY in Git-hub: Windows

Type this in cmd: ssh-keygen -t ed25519 -C "your-email-id"

Go to C:\Users\your-name\.ssh

There you will get a file: id_ed25519.pub

open that file , copy that , go to github->setting->keys->ssh-key->new SSH Key

There paste your copied key

Done!!

So, after update I had the same issue. I was using PEM key_file without extension and simply adding .pem fixed my issue. Now the file is key_file.pem.

@uvsmtid Your post finally lead me into the right direction: simply deleting (actually renaming) the public key file id_rsa.pub solved the problem for me, that git was working though nagging about invalid format. Not quite sure, yet the file is not actually needed, since the pub key can be extracted from private key file id_rsa anyway.

I had a similar error Load key "/root/.ssh/id_rsa": invalid format when I tried

RUN echo "$ssh_prv_key" > /root/.ssh/id_rsa &&     chmod 600 /root/.ssh/id_rsa

This led to errors like identity file /root/.ssh/id_rsa type -1 invalid format and read_passphrase: can't open /dev/tty.

The right way would be to use

COPY id_rsa /root/.ssh/id_rsa
RUN chmod 600 /root/.ssh/id_rsa

The solution explained: my private key was wrongly formatted - instead of many lines, it was passed as a one-liner, and you might have any other format issue like a forgotten "-" at the start or end, or something wrong at the end of the lines, like a missing newline format or an additional letter at the end of a line.

See Dockerfile: clone repo with passwordless private key. Errors: “authentication agent” or “read_passphrase: can't open /dev/tty” for more details, with the main idea from Add private key to ssh-agent in docker file, which again had the idea from Gitlab CI/Docker: ssh-add keeps asking for passphrase.