Release 2.0.6.1 (beta) 2021 - SFTP failure (Synology)

warwickmm · May 11, 2021, 4:32pm

Looking into this some more, I believe this might explain what we’ve discovered. This pull request added support for elliptic curve algorithms in SSH.NET. For ECDSA, it relies on the System.Security.Cryptography.ECDsaCng class

github.com

sshnet/SSH.NET/blob/a5bd08d655bb6a3c762306472cec354556dca3a3/src/Renci.SshNet/Security/Cryptography/EcdsaKey.cs#L357


            {
                bw.Write((int)curve_magic);
                bw.Write(cord_size);
                bw.Write(qx); // q.x
                bw.Write(qy); // q.y
                if (privatekey != null)
                    bw.Write(privatekey); // d
            }
            key = CngKey.Import(blob, privatekey == null ? CngKeyBlobFormat.EccPublicBlob : CngKeyBlobFormat.EccPrivateBlob);


            Ecdsa = new ECDsaCng(key);
#endif
        }


        private string GetCurveOid(string curve_s)
        {
            switch (curve_s.ToLower())
            {
                case "nistp256":
                    return ECDSA_P256_OID_VALUE;
                case "nistp384":

which is not implemented in Mono

github.com

mono/mono/blob/def4f3be68c44c3fb353fe46f00d540f4ed9bd15/mcs/class/referencesource/System.Core/System/Security/Cryptography/ECDsaCng.cs#L29-L32


[SecuritySafeCritical]
public ECDsaCng(CngKey key) {
    throw new NotImplementedException ();
}

For ED25519, SSH.NET provides its own implementation (from Choas.NaCl).