aes256-ctr not supported for private keys

[brohee]

Hi,

Newer OpenSSH versions seem to create private keys enciphered with aes256-ctr by default, at least for ed25519 keys, making them impossible to load with SSH.NET. Given than ssh-keygen doesn't provide a handy way to reencode the key, it's pretty annoying.

Stacktrace of an attempt at loading such a key:

Renci.SshNet.Common.SshException: cipher name aes256-ctr for openssh key file is not supported
   . Renci.SshNet.PrivateKeyFile.ParseOpenSshV1Key(Byte[] keyFileData, String passPhrase)
   . Renci.SshNet.PrivateKeyFile.Open(Stream privateKey, String passPhrase)
   . Renci.SshNet.PrivateKeyFile..ctor(Stream privateKey, String passPhrase)

[darinkes]

This PR includes this: #614

[MAGICCC]

Seems we need to have a release so other programs can update their dependencies against the new release

[lilhoser]

When will this fix be available?

[darkoperator]

No nuget released announced yet, but you can git pull and conpile

…

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[kcadduk]

I don't suppose you have an update on the next release to fix this issue?

[Dean-NC]

I'm using the main branch (version 2020.0.1) so I also get this error. I know it's fixed in the develop branch, but I decided to not use a password on the key right now, which avoids the error. Hopefully a new main release will get put out soon.

[icedream]

This specific cipher is currently not implemented in the case of decrypting OpenSSH V1 keys:

https://github.com/sshnet/SSH.NET/blob/2020.0.2/src/Renci.SshNet/PrivateKeyFile.cs#L427-L455

The code simply assumes the encryption is either aes256-cbc or non-existent, otherwise it fails. So someone needs to implement aes256-ctr (and preferably other possible ciphers for this case).

[MAGICCC]

If you want to use ed25519 keys you may change the encryption cipher using the -Z parameter

-Z cipher
Specifies the cipher to use for encryption when writing an OpenSSH-format private key file. The list of available ciphers may be >obtained using "ssh -Q cipher". The default is “aes256-ctr”.

ssh-keygen -t ed25519 -b 384 -C "<comment>" -f <output_keyfile> -Z aes256-cbc

[ming86]

If you want to use ed25519 keys you may change the encryption cipher using the -Z parameter

-Z cipher
Specifies the cipher to use for encryption when writing an OpenSSH-format private key file. The list of available ciphers may be >obtained using "ssh -Q cipher". The default is “aes256-ctr”.

ssh-keygen -t ed25519 -b 384 -C "<comment>" -f <output_keyfile> -Z aes256-cbc

If you want to change passphrase and cipher of an existing ed25519 key

ssh-keygen -f <private_keyfile> -p -Z aes256-cbc

enter the passphrase as prompts.

[tparikka]

Is there a release date planned for this fix?

[Dean-NC]

I think a release should be made. It's been a while.