internal static SftpClient CreateSftpClient(this string connectionString)
{
if (connectionString == null)
{
throw new ArgumentNullException("connectionString");
}
// get parts of connection string
var csb = new DbConnectionStringBuilder {
ConnectionString = connectionString
};
var host = csb["host"] as string;
var username = csb["username"] as string;
var password = csb["password"] as string;
var hostkey = csb["hostkey"] as string;
var port = Attempt.Get(() => Convert.ToInt32(csb["port"]));
// do this when connstring is bad
Action <string> badConnString = detail =>
{
throw new FormatException(
string.Format(
"SFTP connection string invalid. {0} Example: username=USERNAME;password=PASSWORD;host=HOSTNAME;hostkey=ssh-dss 1024 3b:1c:20:aa:27:00:83:4f:7a:49:9c:9f:e7:67:ab:03",
detail ?? ""));
};
// check required conn string params
if (new[] { host, username, password, hostkey }.Any(string.IsNullOrWhiteSpace))
{
badConnString("Missing required parameter.");
}
// check format of host key
var hostKeyParts =
hostkey.Split().Where(x => !string.IsNullOrWhiteSpace(x)).Select(x => x.Trim().ToLower()).ToArray();
// host key needs 3 parts: name, length, fingerprint
if (hostKeyParts.Length != 3)
{
badConnString(string.Format("Host key '{0}' is incorrectly formatted.", hostkey));
}
// length neeeds to be an int
int hostKeyLength;
if (!int.TryParse(hostKeyParts[1], out hostKeyLength))
{
badConnString(string.Format("Host key length '{0}' is not an integer.", hostKeyParts[1]));
}
// finter print needs to be a byte array as hex string
var hostKeyPrint =
Attempt.Get(() => SoapHexBinary.Parse(string.Concat(hostKeyParts[2].Where(char.IsLetterOrDigit))).Value);
if (!hostKeyPrint.Succeeded)
{
badConnString(string.Format("Invalid host key fingerprint '{0}'.", hostKeyParts[2]));
}
// using only pw auth for time being
var pwAuthMethod = new PasswordAuthenticationMethod(username, password);
var connInfo = port.Succeeded
? new ConnectionInfo(host, port.Value, username, pwAuthMethod)
: new ConnectionInfo(host, username, pwAuthMethod);
var sftpClient = new SftpClient(connInfo);
// validate host key
sftpClient.HostKeyReceived += (s, e) =>
{
e.CanTrust = hostKeyParts[0].Equals(e.HostKeyName.Trim(), StringComparison.OrdinalIgnoreCase) &&
hostKeyLength == e.KeyLength &&
hostKeyPrint.Value.SequenceEqual(e.FingerPrint);
};
return(sftpClient);
}
