SSH.NET Public Key Authentication

Question

I know that private key authentication works, however I'm looking for public key authentication.

I'm trying to establish a connection using SSH.NET and a public key.

In the Git Bash terminal I can connect and run commands fine using my public key, but when I try connecting to the same host using SSH.NET I get an exception.

Here is my how I'm trying to connect:

using (var client = new SshClient("host.name.com", port, "username"))
{
    client.Connect(); // exception thrown here
}

I've also tried this route:

var authMethod = new PrivateKeyAuthenticationMethod("username");
var info = new ConnectionInfo("host.name.com", port, "username", authMethod);
using (var client = new SshClient(info))

Both give the same exception: Permission denied (publickey).

It seems as though I need to specify where my public key is, or I need to put my public key in a certain spot, but I can't find any documentation telling me where to put it.

Answer 1

There's no "private key authentication". It's actually called "public key authentication".

Though you need both private and public key to authenticate using "public key authentication". It's called "public key authentication", because a client (SSH.NET in this case) sends only the public key to the server – So the server authenticates you using the public key only. The private key is used locally only.

Though file formats that are commonly referred to as a private key (like PEM or .ppk) – as opposite to public key (.pub) formats – actually contain whole key pair (both public and private key).

So the question that you link to – SSH.NET Authenticate via private key only (public key authentication) – actually does what you want. It shows how to authenticate using "public key authentication" – using private key file format (both public and private key really). I've edited the title of that question to make this more clear.

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And to correct you, it's not true that "In the Git Bash terminal I can connect and run commands fine using my public key" – That's not possible. You must have a private key too.