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Database Access with Microsoft SQL Server with Active Directory authentication

Teleport can provide secure access to Microsoft SQL Server via the Teleport Database Service. This allows for fine-grained access control through Teleport's RBAC.

In this guide, you will:

  1. Configure your Microsoft SQL Server database with Active Directory authentication.
  2. Add the database to your Teleport cluster.
  3. Connect to the database via Teleport.

This guide will focus on Amazon RDS for SQL Server using AWS-managed Active Directory authentication.

How it works​

The Teleport Database Service joins the same Active Directory domain as the SQL Server database and uses the Kerberos protocol to authenticate with SQL Server. When a user connects to SQL Server via Teleport, the Database Service obtains a service ticket from Active Directory, then uses a long-term key for the database user to decrypt the ticket and connect to SQL Server. At that point, the Database Service forwards user traffic to the database.

Database access with SQL Server and AD authentication

Prerequisites​

  • A running Teleport cluster version 15.4.22 or above. If you want to get started with Teleport, sign up for a free trial or set up a demo environment.

  • The tctl admin tool and tsh client tool.

    On Teleport Enterprise, you must use the Enterprise version of tctl, which you can download from your Teleport account workspace. Otherwise, visit Installation for instructions on downloading tctl and tsh for Teleport Community Edition.

  • A SQL Server database with Active Directory authentication enabled.
  • A SQL Server network listener configured with a Certificate using Subject Alternative Names
  • A Windows machine joined to the same Active Directory domain as the database.
  • A Linux node joined to the same Active Directory domain as the database. This guide will walk you through the joining steps if you don't have one.
  • To check that you can connect to your Teleport cluster, sign in with tsh login, then verify that you can run tctl commands using your current credentials. tctl is supported on macOS and Linux machines. For example: 
    $ tsh login --proxy=teleport.example.com --user=email@example.com
    $ tctl status
    # Cluster  teleport.example.com
    # Version  15.4.22
    # CA pin   sha256:abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678
    If you can connect to the cluster and run the tctl status command, you can use your current credentials to run subsequent tctl commands from your workstation. If you host your own Teleport cluster, you can also run tctl commands on the computer that hosts the Teleport Auth Service for full permissions.

Step 1/7. Create a Teleport user​

tip

To modify an existing user to provide access to the Database Service, see Database Access Controls

Create a local Teleport user with the built-in access role:

$ tctl users add \
  --roles=access \
  --db-users="*" \
  --db-names="*" \
  alice
FlagDescription
--rolesList of roles to assign to the user. The builtin access role allows them to connect to any database server registered with Teleport.
--db-usersList of database usernames the user will be allowed to use when connecting to the databases. A wildcard allows any user.
--db-namesList of logical databases (aka schemas) the user will be allowed to connect to within a database server. A wildcard allows any database.
warning

Database names are only enforced for PostgreSQL, MongoDB, and Cloud Spanner databases.

For more detailed information about database access controls and how to restrict access see RBAC documentation.

Step 2/7. Join the Linux node to Active Directory​

note

You can skip this step if you already have a Linux node joined to the same Active Directory domain as your SQL Server instance.

The Linux node where the Database Service will run must be joined to the same Active Directory domain as the SQL Server database.

Note that in order to be able to join, the Linux node must be able to resolve your Active Directory fully-qualified domain name. For example, for AWS-managed AD, use nameservers provided under "Networking details" on the directory's overview page.

Install necessary packages:

$ sudo apt-get update
$ sudo apt-get -y install sssd realmd krb5-user samba-common packagekit adcli

Edit /etc/krb5.conf to disable reverse DNS resolution and set the default realm. Make sure that the [realms] section contains your domain definition and has admin_server and kdc fields set pointing to the domain controllers:

[libdefaults]
default_realm = EXAMPLE.COM
rdns = false

[realms]
  EXAMPLE.COM = {
    kdc = example.com
    admin_server = example.com
  }

Join the realm:

$ sudo realm join -v -U admin@EXAMPLE.COM example.com
...
 * Successfully enrolled machine in realm
warning

Note that the realm name in admin@EXAMPLE.COM must be capital case, otherwise the node might not be able to join.

To confirm the node has joined the realm, use the realm list command:

$ sudo realm list
example.com
  type: kerberos
  realm-name: EXAMPLE.COM
  domain-name: example.com
  configured: kerberos-member
  server-software: active-directory
  client-software: sssd
  ...

Step 3/7. Create keytab file​

Teleport requires a keytab file to obtain Kerberos service tickets from your Active Directory for authentication with SQL Server. The easiest way to generate it is to use the adutil Linux CLI utility.

Install adutil on the Linux node you have joined to your Active Directory domain:

$ curl https://packages.microsoft.com/keys/microsoft.asc | sudo apt-key add -
$ sudo curl https://packages.microsoft.com/config/ubuntu/18.04/prod.list | sudo tee /etc/apt/sources.list.d/msprod.list
$ sudo apt-get update
$ sudo ACCEPT_EULA=Y apt-get install -y adutil

Log in to Active Directory using the kinit command:

$ kinit admin@EXAMPLE.COM

Use the adutil keytab create command to generate keytab entries for each Active Directory user that will be connecting to the SQL Server database:

$ adutil keytab create teleport.keytab alice
$ adutil keytab create teleport.keytab bob

You will be prompted to enter each user's password. All keytab entries will be merged into the same teleport.keytab file.

Assign Service Principal Names

For the adutil keytab create command to work, each user account must be assigned a Service Principal Name, otherwise the command will not be able to determine its kvno (key version number).

To check if the user has any SPNs assigned, run the following command on the Windows machine joined to your Active Directory domain:

$ setspn -L alice

To assign an SPN to a user account, use the following command:

$ setspn -s user/alice alice

You can verify entries in the keytab file using klist command:

$ klist -ke teleport.keytab
Keytab name: FILE:teleport.keytab
KVNO Principal
---- --------------------------------------------------------------------------
   5 alice@EXAMPLE.COM (aes256-cts-hmac-sha1-96)
   2 bob@EXAMPLE.COM (aes256-cts-hmac-sha1-96)
warning

You must update the keytab file after updating a user's password to avoid authentication failures.

Step 4/7. Set up the Teleport Database Service​

The Database Service requires a valid join token to join your Teleport cluster. Run the following tctl command and save the token output in /tmp/token on the server that will run the Database Service:

$ tctl tokens add --type=db --format=text
abcd123-insecure-do-not-use-this

Install Teleport on your Linux server:

  1. Assign edition to one of the following, depending on your Teleport edition:

    EditionValue
    Teleport Enterprise Cloudcloud
    Teleport Enterprise (Self-Hosted)enterprise
    Teleport Community Editionoss

  2. Get the version of Teleport to install. If you have automatic agent updates enabled in your cluster, query the latest Teleport version that is compatible with the updater:

    $ TELEPORT_DOMAIN=example.teleport.com
    $ TELEPORT_VERSION="$(curl https://$TELEPORT_DOMAIN/v1/webapi/automaticupgrades/channel/default/version | sed 's/v//')"

    Otherwise, get the version of your Teleport cluster:

    $ TELEPORT_DOMAIN=example.teleport.com
    $ TELEPORT_VERSION="$(curl https://$TELEPORT_DOMAIN/v1/webapi/ping | jq -r '.server_version')"

  3. Install Teleport on your Linux server:

    $ curl https://cdn.teleport.dev/install-v15.4.22.sh | bash -s ${TELEPORT_VERSION} edition

    The installation script detects the package manager on your Linux server and uses it to install Teleport binaries. To customize your installation, learn about the Teleport package repositories in the installation guide.

note

Teleport Database Service must run on a Linux server joined to the same Active Directory domain as the SQL Server.

Configure the Teleport Database Service. Make sure to update --proxy to point to your Teleport Proxy Service address and --uri to the SQL Server endpoint.

$ sudo teleport db configure create \
  -o file \
  --token=/tmp/token \
  --proxy=teleport.example.com:443 \
  --name=sqlserver \
  --protocol=sqlserver \
  --uri=sqlserver.example.com:1433 \
  --ad-keytab-file=/path/to/teleport.keytab \
  --ad-domain=EXAMPLE.COM \
  --ad-spn=MSSQLSvc/sqlserver.example.com:1433 \
  --labels=env=dev

Provide Active Directory parameters:

FlagDescription
--ad-keytab-filePath to Kerberos keytab file generated above.
--ad-domainActive Directory domain (Kerberos realm) that SQL Server is joined.
--ad-spnService Principal Name for SQL Server to fetch Kerberos tickets for.

Service Principal Name​

You can use ldapsearch command to see the SPNs registered for your SQL Server. Typically, they take a form of MSSQLSvc/<name>.<ad-domain>:<port>.

For example, an AWS RDS SQL Server named sqlserver and joined to an AWS managed Active Directory domain EXAMPLE.COM will have the following SPNs registered:

$ ldapsearch -x -h example.com -D admin -W -b DC=example,DC=com servicePrincipalName
...
# EC2AMAZ-4KN05DU, RDS, AWS Reserved, example.com
dn: CN=EC2AMAZ-4KN05DU,OU=RDS,OU=AWS Reserved,DC=example,DC=com
servicePrincipalName: MSSQLSvc/sqlserver-rds.example.com:1433
servicePrincipalName: MSSQLSvc/EC2AMAZ-4KN05DU.example.com:1433
servicePrincipalName: MSSQLSvc/EC2AMAZ-4KN05DU.example.com
...

Alternatively, you can look SPNs up in the Attribute Editor of the Active Directory Users and Computers dialog on your AD-joined Windows machine. The RDS SQL Server object typically resides under the AWS Reserved / RDS path:

SPN

tip

If you don't see Attribute Editor tab, make sure that "View > Advanced Features" toggle is enabled.

Step 5/7. Start the Database Service​

Configure the Teleport Database Service to start automatically when the host boots up by creating a systemd service for it. The instructions depend on how you installed the Teleport Database Service.

On the host where you will run the Teleport Database Service, enable and start Teleport:

$ sudo systemctl enable teleport
$ sudo systemctl start teleport

You can check the status of the Teleport Database Service with systemctl status teleport and view its logs with journalctl -fu teleport.

Step 6/7. Create SQL Server AD users​

note

You can skip this step if you already have Active Directory logins in your SQL Server.

Connect to your SQL Server as an administrative account (e.g. sa) and create logins that will use Active Directory authentication:

master> CREATE LOGIN [EXAMPLE\alice] FROM WINDOWS WITH DEFAULT_DATABASE = [master], DEFAULT_LANGUAGE = [us_english];

Step 7/7. Connect​

Log in to your Teleport cluster. Your SQL Server database should appear in the list of available databases:

$ tsh login --proxy=teleport.example.com --user=alice
$ tsh db ls
# Name      Description         Labels
# --------- ------------------- -------
# sqlserver                     env=dev

To retrieve credentials for a database and connect to it:

$ tsh db connect --db-user=teleport sqlserver
note

Either the sqlcmd or mssql-cli command-line clients should be available in PATH in order to be able to connect. tsh attempts to run sqlcmd first and, if it's not present on the PATH, runs mssql-cli.

If you have neither command-line clients available on your system, you can run the following command to start a local proxy server that you can connect to with your SQL Server client:

$ tsh proxy db --db-user=teleport --tunnel sqlserver

Read the Database Access GUI Clients guide for how to connect your DB GUI client to the local proxy.

To log out of the database and remove credentials:

$ tsh db logout sqlserver

Troubleshooting​

Certificate error​

If your tsh db connect error includes the following text, the certificate used by SQL Server is not a known Certificate Authority.

Error message: TLS Handshake failed: x509: certificate signed by unknown authority

To solve this, you can add the CA configuration to the database like the following:

  databases:
  - name: sqlserver
    protocol: sqlserver
    uri: sqlserver.example.com:1433
    ad:
      keytab_file: /path/to/teleport.keytab
      domain: EXAMPLE.COM
      spn: MSSQLSvc/sqlserver.example.com:1433
    static_labels:
      "env": "dev"
+   tls:
+     # Point it to your Database CA PEM certificate.
+     ca_cert_file: "rdsca.pem"
+     # If your database certificate has an empty CN filed, you must change
+     # the TLS mode to only verify the CA.
+     mode: verify-ca

If you’re unable to acquire the database CA, you can skip TLS verification by providing the configuration tls.mode: "insecure". However, we do not recommend skipping TLS verification in production environments.

Next steps​

  • Take a look at the YAML configuration reference.

Further reading​