protected override void OnFatalError()

in sources/Google.Solutions.IapDesktop.Extensions.Session/ToolWindows/Session/SshView.cs [179:250]
64 lines of code
13 McCabe index (conditional complexity)

        protected override void OnFatalError(Exception e)
        {
            //
            // Translate common exceptions to make them more actionable.
            //
            if (e.Unwrap() is Libssh2Exception unverifiedEx &&
                unverifiedEx.ErrorCode == LIBSSH2_ERROR.PUBLICKEY_UNVERIFIED &&
                this.viewModel.Value.Credential is PlatformCredential unverifiedPlatformCredential &&
                unverifiedPlatformCredential.AuthorizationMethod == KeyAuthorizationMethods.Oslogin)
            {
                OnFatalError(new OsLoginAuthenticationFailedException(
                    "Authenticating to the VM failed. Possible reasons for this " +
                    "error include:\n\n" +
                    " - The VM is configured to require 2-step verification,\n" +
                    "   and you haven't set up 2SV for your user account\n" +
                    " - The guest environment is misconfigured or not running",
                    e,
                    HelpTopics.TroubleshootingOsLogin));
            }
            else if (e.Unwrap() is Libssh2Exception authEx &&
                authEx.ErrorCode == LIBSSH2_ERROR.AUTHENTICATION_FAILED &&
                this.viewModel.Value.Credential is PlatformCredential failedPlatformCredential)
            {
                if (failedPlatformCredential.AuthorizationMethod == KeyAuthorizationMethods.Oslogin)
                {
                    var outdatedMessage = failedPlatformCredential.Signer is OsLoginCertificateSigner
                        ? " - The VM is running an outdated version of the guest environment \n" +
                          "   that doesn't support certificate-based authentication\n"
                        : string.Empty;

                    var message =
                        "Authenticating to the VM failed. Possible reasons for this " +
                        "error include:\n\n" +
                        " - You don't have sufficient access to log in\n" +
                        outdatedMessage +
                        " - The VM's guest environment is misconfigured or not running\n\n" +
                        "To log in, you need all of the following roles:\n\n" +
                        " 1. 'Compute OS Login' or 'Compute OS Admin Login'\n" +
                        " 2. 'Service Account User' (if the VM uses a service account)\n" +
                        " 3. 'Compute OS Login External User'\n" +
                        "    (if the VM belongs to a different GCP organization)\n\n" +
                        "Note that it might take several minutes for IAM policy changes to take effect.";

                    OnFatalError(new OsLoginAuthenticationFailedException(
                        message,
                        e,
                        HelpTopics.GrantingOsLoginRoles));
                }
                else
                {
                    OnFatalError(new MetadataKeyAuthenticationFailedException(
                        "Authentication failed. Verify that the Compute Engine guest environment " +
                        "is installed on the VM and that the agent is running.",
                        e,
                        HelpTopics.ManagingMetadataAuthorizedKeys));
                }
            }
            else if (e.Unwrap() is Libssh2Exception kexEx &&
                kexEx.ErrorCode == LIBSSH2_ERROR.KEY_EXCHANGE_FAILURE &&
                Environment.OSVersion.Version.Build <= 10000)
            {
                //
                // Libssh2's CNG support requires Windows 10+.
                //
                OnFatalError(new PlatformNotSupportedException(
                    "SSH is not supported on this version of Windows"));
            }
            else
            {
                base.OnFatalError(e);
            }
        }