System.NotSupportedException: Key 'OPENSSH' is not supported.

[mauroa]

A NotSupportedException is thrown when generating SSH keys with the "ssh-keygen" command on a Mac with macOS Mojave 10.14.1. With lower versions it's working fine.

Exception:

System.NotSupportedException: Key 'OPENSSH' is not supported.
at Renci.SshNet.PrivateKeyFile.Open(Stream privateKey, String passPhrase)
at Renci.SshNet.PrivateKeyFile..ctor(String fileName, String passPhrase)

Inspecting the generated private key I can see that the header starts with:

"-----BEGIN OPENSSH PRIVATE KEY-----"

Also, If I inspect a private key generated in a Mac with a lower macOS version, I can see something like:

"-----BEGIN RSA PRIVATE KEY-----"

The following code in this repo tries to match a Regex to detect they key name and act based on it. For this reason, It doesn't recognize "OPENSSH" as a valid private key name and it fails:

SSH.NET/src/Renci.SshNet/PrivateKeyFile.cs

Lines 190 to 273 in bd01d97

	switch (keyName)
	{
	case "RSA":
	_key = new RsaKey(decryptedData);
	HostKey = new KeyHostAlgorithm("ssh-rsa", _key);
	break;
	case "DSA":
	_key = new DsaKey(decryptedData);
	HostKey = new KeyHostAlgorithm("ssh-dss", _key);
	break;
	case "SSH2 ENCRYPTED":
	var reader = new SshDataReader(decryptedData);
	var magicNumber = reader.ReadUInt32();
	if (magicNumber != 0x3f6ff9eb)
	{
	throw new SshException("Invalid SSH2 private key.");
	}
	reader.ReadUInt32(); // Read total bytes length including magic number
	var keyType = reader.ReadString(SshData.Ascii);
	var ssh2CipherName = reader.ReadString(SshData.Ascii);
	var blobSize = (int)reader.ReadUInt32();
	byte[] keyData;
	if (ssh2CipherName == "none")
	{
	keyData = reader.ReadBytes(blobSize);
	}
	else if (ssh2CipherName == "3des-cbc")
	{
	if (string.IsNullOrEmpty(passPhrase))
	throw new SshPassPhraseNullOrEmptyException("Private key is encrypted but passphrase is empty.");
	var key = GetCipherKey(passPhrase, 192 / 8);
	var ssh2Сipher = new TripleDesCipher(key, new CbcCipherMode(new byte[8]), new PKCS7Padding());
	keyData = ssh2Сipher.Decrypt(reader.ReadBytes(blobSize));
	}
	else
	{
	throw new SshException(string.Format("Cipher method '{0}' is not supported.", cipherName));
	}
	// TODO: Create two specific data types to avoid using SshDataReader class
	reader = new SshDataReader(keyData);
	var decryptedLength = reader.ReadUInt32();
	if (decryptedLength > blobSize - 4)
	throw new SshException("Invalid passphrase.");
	if (keyType == "if-modn{sign{rsa-pkcs1-sha1},encrypt{rsa-pkcs1v2-oaep}}")
	{
	var exponent = reader.ReadBigIntWithBits();//e
	var d = reader.ReadBigIntWithBits();//d
	var modulus = reader.ReadBigIntWithBits();//n
	var inverseQ = reader.ReadBigIntWithBits();//u
	var q = reader.ReadBigIntWithBits();//p
	var p = reader.ReadBigIntWithBits();//q
	_key = new RsaKey(modulus, exponent, d, p, q, inverseQ);
	HostKey = new KeyHostAlgorithm("ssh-rsa", _key);
	}
	else if (keyType == "dl-modp{sign{dsa-nist-sha1},dh{plain}}")
	{
	var zero = reader.ReadUInt32();
	if (zero != 0)
	{
	throw new SshException("Invalid private key");
	}
	var p = reader.ReadBigIntWithBits();
	var g = reader.ReadBigIntWithBits();
	var q = reader.ReadBigIntWithBits();
	var y = reader.ReadBigIntWithBits();
	var x = reader.ReadBigIntWithBits();
	_key = new DsaKey(p, q, g, y, x);
	HostKey = new KeyHostAlgorithm("ssh-dss", _key);
	}
	else
	{
	throw new NotSupportedException(string.Format("Key type '{0}' is not supported.", keyType));
	}
	break;
	default:
	throw new NotSupportedException(string.Format(CultureInfo.CurrentCulture, "Key '{0}' is not supported.", keyName));

Thanks.

[darinkes]

Please see #496, which adds OPENSSH-Format for ed25519 Keys.
What kind of key you used? Can't find on a quick search what MacOS ssh-keygen generates by default.

The usual default is: If invoked without any arguments, ssh-keygen will generate an RSA key.
(https://man.openbsd.org/ssh-keygen)

[darinkes]

Ah! I see now. Yeah, the default format was changed. Will see if my PR can be updated to support more than just ed25519 Keys.

[drieseng]

@darinkes Please submit a separate PR for this.

[darinkes]

@drieseng sure! first finish the big one.

@mauroa If you want to give it a shot: https://github.com/darinkes/SSH.NET-1/tree/openssh_format_rsa

[gojimmypi]

@darinkes - cool you are working on openssh; wondering about the status of your changes? will it include Message Authentication Code (HMAC)? perhaps I can help?

[darinkes]

@gojimmypi I'm waiting for upstream to catch up with current PRs, before creating new ones.

[ssougnez]

Is there any advancement on this one ?
I really need to be able to connect through SFTP via OpenSSH key :-)

[nukadelic]

Same here, failed to support generated ssh via ssh-keygen -t rsa

Edit: Using puttygen and exporting under different format fixed my issue, here is a neat article:
https://lluisfranco.com/2017/11/29/how-to-connect-via-sftp-using-ssh-net/

[watsonsong]

The same problem. Is there any plan to support OPENSSH keyname?

[darinkes]

The same problem. Is there any plan to support OPENSSH keyname?

Yes, the diff is ready for an PR. But @drieseng is currently busy with other projects.
You can check out and test the diff from here: #485 (comment)

[drieseng]

@darinkes Please submit a PR for this. If you make sure there's sufficient test coverage, I'll do my best to review it :p

[drieseng]

@darinkes ... and thx!

[darinkes]

@drieseng The diff is based on the Elliptic Curves Branch, cause OPENSSH format was needed there already partially.

[michael-andreev]

Having the same problem. Could you tell the current status of this issue?

[yhjhoo]

for me, this lib works in mac but no in windows 2012R2