Set up FIPS-compliant secure remote Linux development

Article
10/17/2022

Linux support is available in Visual Studio 2017 and later. FIPS-compliant secure remote Linux development is available in Visual Studio 2019 version 16.5 and later.

Federal Information Processing Standard (FIPS) Publication 140-2 is a U.S. government standard for cryptographic modules. Implementations of the standard are validated by NIST. Windows has validated support for FIPS-compliant cryptographic modules. In Visual Studio 2019 version 16.5 and later, you can use a secure, FIPS-compliant cryptographic connection to your Linux system for remote development.

Here's how to set up a secure, FIPS-compliant connection between Visual Studio and your remote Linux system. This guide is applicable when you build CMake or MSBuild Linux projects in Visual Studio. This article is the FIPS-compliant version of the connection instructions in Connect to your remote Linux computer.

Prepare a FIPS-compliant connection

Some preparation is required to use a FIPS-compliant, cryptographically secure ssh connection between Visual Studio and your remote Linux system. For FIPS-140-2 compliance, Visual Studio only supports RSA keys.

The examples in this article use Ubuntu 18.04 LTS with OpenSSH server version 7.6. However, the instructions should be the same for any distro using a moderately recent version of OpenSSH.

To set up the SSH server on the remote system

On the Linux system, install and start the OpenSSH server:
```
sudo apt install openssh-server
sudo service ssh start
```
If you'd like the ssh server to start automatically when the system boots, enable it using systemctl:
```
sudo systemctl enable ssh
```
Open /etc/ssh/sshd_config as root. Edit (or add, if they don't exist) the following lines:
```
Ciphers aes256-cbc,aes192-cbc,aes128-cbc,3des-cbc
HostKeyAlgorithms ssh-rsa
KexAlgorithms diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1
MACs hmac-sha2-256,hmac-sha1
```
Note

ssh-rsa is the only FIPS compliant host key algorithm VS supports. The aes*-ctr algorithms are also FIPS compliant, but the implementation in Visual Studio isn't approved. The ecdh-* key exchange algorithms are FIPS compliant, but Visual Studio doesn't support them.

You're not limited to these options. You can configure ssh to use other ciphers, host key algorithms, and so on. Some other relevant security options you may want to consider are PermitRootLogin, PasswordAuthentication, and PermitEmptyPasswords. For more information, see the man page for sshd_config or the article SSH Server Configuration.
After saving and closing sshd_config, restart the ssh server to apply the new configuration:
```
sudo service ssh restart
```

Next, you'll create an RSA key pair on your Windows computer. Then you'll copy the public key to the remote Linux system for use by ssh.

To create and use an RSA key file

On the Windows machine, generate a public/private RSA key pair by using this command:
```
ssh-keygen -t rsa -b 4096 -m PEM
```
The command creates a public key and a private key. By default, the keys are saved to %USERPROFILE%\.ssh\id_rsa and %USERPROFILE%\\.ssh\\id_rsa.pub. (In PowerShell, use $env:USERPROFILE instead of the cmd macro %USERPROFILE%) If you change the key name, use the changed name in the steps that follow. We recommend you use a passphrase for increased security.
From Windows, copy the public key to the Linux machine:
```
scp %USERPROFILE%\.ssh\id_rsa.pub user@hostname:
```
On the Linux system, add the key to the list of authorized keys, and ensure the file has the correct permissions:
```
cat ~/id_rsa.pub >> ~/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys
```
Now, you can test to see if the new key works in ssh. Use it to sign in from Windows:
```
ssh -i %USERPROFILE%\.ssh\id_rsa user@hostname
```

You've successfully set up ssh, created and deployed encryption keys, and tested your connection. Now you're ready to set up the Visual Studio connection.

Connect to the remote system in Visual Studio

In Visual Studio, choose Tools > Options on the menu bar to open the Options dialog. Then select Cross Platform > Connection Manager to open the Connection Manager dialog.

If you haven't set up a connection in Visual Studio before, when you build your project for the first time, Visual Studio opens the Connection Manager dialog for you.
In the Connection Manager dialog, choose the Add button to add a new connection.

The Connect to Remote System window is displayed.

In the Connect to Remote System dialog, enter the connection details of your remote machine.

Entry	Description
Host Name	Name or IP address of your target device
Port	Port that the SSH service is running on, typically 22
User name	User to authenticate as
Authentication type	Choose Private Key for a FIPS-compliant connection
Private key file	Private key file created for ssh connection
Passphrase	Passphrase used with private key selected above

Change the authentication type to Private Key. Enter the path to your private key in the Private key file field. You can use the Browse button to navigate to your private key file instead. Then, enter the passphrase used to encrypt your private key file in the Passphrase field.

Choose the Connect button to attempt a connection to the remote computer.

If the connection succeeds, Visual Studio configures IntelliSense to use the remote headers. For more information, see IntelliSense for headers on remote systems.

If the connection fails, the entry boxes that need to be changed are outlined in red.

For more information on troubleshooting your connection, see Connect to your remote Linux computer.

Command-line utility for the Connection Manager

Visual Studio 2019 version 16.5 or later: ConnectionManager.exe is a command-line utility to manage remote development connections outside of Visual Studio. It's useful for tasks such as provisioning a new development machine. Or, you can use it to set up Visual Studio for continuous integration. For examples and a complete reference to the ConnectionManager command, see ConnectionManager reference.

Optional: Enable or disable FIPS mode

It's possible to enable FIPS mode globally in Windows.

To enable FIPS mode, press Windows+R to open the Run dialog, and then run gpedit.msc.
Expand Local Computer Policy > Computer Configuration > Windows Settings > Security Settings > Local Policies and select Security Options.
Under Policy, select System cryptography: Use FIPS-compliant algorithms for encryption, hashing, and signing, and then press Enter to open its dialog box.
In the Local Security Setting tab, select Enabled or Disabled, and then choose OK to save your changes.

Warning

Enabling FIPS mode may cause some applications to break or behave unexpectedly. For more information, see the blog post Why We're Not Recommending "FIPS mode" Anymore.