Windows Remote Management

Unlike Linux/Unix hosts, which use SSH by default, Windows hosts are configured with WinRM. This topic covers how to configure and use WinRM with Ansible.

• What is WinRM?
• Authentication Options
  • Basic
  • Certificate
    • Generate a Certificate
    • Import a Certificate to the Certificate Store
    • Mapping a Certificate to an Account
  • NTLM
  • Kerberos
    • Installing the Kerberos Library
    • Configuring Host Kerberos
    • Automatic Kerberos Ticket Management
    • Manual Kerberos Ticket Management
    • Troubleshooting Kerberos
  • CredSSP
    • Installing CredSSP Library
    • CredSSP and TLS 1.2
    • Set CredSSP Certificate
• Non-Administrator Accounts
• WinRM Encryption
• Inventory Options
• IPv6 Addresses
• HTTPS Certificate Validation
• Limitations

What is WinRM?

WinRM is a management protocol used by Windows to remotely communicate with another server. It is a SOAP-based protocol that communicates over HTTP/HTTPS, and is included in all recent Windows operating systems. Since Windows Server 2012, WinRM has been enabled by default, but in most cases extra configuration is required to use WinRM with Ansible.

Ansible uses the pywinrm package to communicate with Windows servers over WinRM. It is not installed by default with the Ansible package, but can be installed by running the following:

pip install "pywinrm>=0.3.0"

Authentication Options

When connecting to a Windows host, there are several different options that can be used when authenticating with an account. The authentication type may be set on inventory hosts or groups with the ansible_winrm_transport variable.

The following matrix is a high level overview of the options:

Option	Local Accounts	Active Directory Accounts	Credential Delegation	HTTP Encryption
Basic	Yes	No	No	No
Certificate	Yes	No	No	No
Kerberos	No	Yes	Yes	Yes
NTLM	Yes	Yes	No	Yes
CredSSP	Yes	Yes	Yes	Yes

Basic

Basic authentication is one of the simplest authentication options to use, but is also the most insecure. This is because the username and password are simply base64 encoded, and if a secure channel is not in use (eg, HTTPS) then it can be decoded by anyone. Basic authentication can only be used for local accounts (not domain accounts).

The following example shows host vars configured for basic authentication:

ansible_user: LocalUsername
ansible_password: Password
ansible_connection: winrm
ansible_winrm_transport: basic

Basic authentication is not enabled by default on a Windows host but can be enabled by running the following in PowerShell:

Set-Item -Path WSMan:\localhost\Service\Auth\Basic -Value $true

Certificate

Certificate authentication uses certificates as keys similar to SSH key pairs, but the file format and key generation process is different.

The following example shows host vars configured for certificate authentication:

ansible_connection: winrm
ansible_winrm_cert_pem: /path/to/certificate/public/key.pem
ansible_winrm_cert_key_pem: /path/to/certificate/private/key.pem
ansible_winrm_transport: certificate

Certificate authentication is not enabled by default on a Windows host but can be enabled by running the following in PowerShell:

Set-Item -Path WSMan:\localhost\Service\Auth\Certificate -Value $true

Generate a Certificate

A certificate must be generated before it can be mapped to a local user. This can be done using one of the following methods:

• OpenSSL
• PowerShell, using the New-SelfSignedCertificate cmdlet
• Active Directory Certificate Services

Active Directory Certificate Services is beyond of scope in this documentation but may be the best option to use when running in a domain environment. For more information, see the Active Directory Certificate Services documentation.

To generate a certificate with OpenSSL:

# set the name of the local user that will have the key mapped to
USERNAME="username"

cat > openssl.conf << EOL
distinguished_name = req_distinguished_name
[req_distinguished_name]
[v3_req_client]
extendedKeyUsage = clientAuth
subjectAltName = otherName:1.3.6.1.4.1.311.20.2.3;UTF8:$USERNAME@localhost
EOL

export OPENSSL_CONF=openssl.conf
openssl req -x509 -nodes -days 3650 -newkey rsa:2048 -out cert.pem -outform PEM -keyout cert_key.pem -subj "/CN=$USERNAME" -extensions v3_req_client
rm openssl.conf

To generate a certificate with New-SelfSignedCertificate:

# set the name of the local user that will have the key mapped
$username = "username"
$output_path = "C:\temp"

# instead of generating a file, the cert will be added to the personal
# LocalComputer folder in the certificate store
$cert = New-SelfSignedCertificate -Type Custom `
    -Subject "CN=$username" `
    -TextExtension @("2.5.29.37={text}1.3.6.1.5.5.7.3.2","2.5.29.17={text}upn=$username@localhost") `
    -KeyUsage DigitalSignature,KeyEncipherment `
    -KeyAlgorithm RSA `
    -KeyLength 2048

# export the public key
$pem_output = @()
$pem_output += "-----BEGIN CERTIFICATE-----"
$pem_output += [System.Convert]::ToBase64String($cert.RawData) -replace ".{64}", "$&`n"
$pem_output += "-----END CERTIFICATE-----"
[System.IO.File]::WriteAllLines("$output_path\cert.pem", $pem_output)

# export the private key in a PFX file
[System.IO.File]::WriteAllBytes("$output_path\cert.pfx", $cert.Export("Pfx"))

Import a Certificate to the Certificate Store

Once a certificate has been generated, the issuing certificate needs to be imported into the Trusted Root Certificate Authorities of the LocalMachine store, and the client certificate public key must be present in the Trusted People folder of the LocalMachine store. For this example, both the issuing certificate and public key are the same.

Following example shows how to import the issuing certificate:

$cert = New-Object -TypeName System.Security.Cryptography.X509Certificates.X509Certificate2
$cert.Import("cert.pem")

$store_name = [System.Security.Cryptography.X509Certificates.StoreName]::Root
$store_location = [System.Security.Cryptography.X509Certificates.StoreLocation]::LocalMachine
$store = New-Object -TypeName System.Security.Cryptography.X509Certificates.X509Store -ArgumentList $store_name, $store_location
$store.Open("MaxAllowed")
$store.Add($cert)
$store.Close()

The code to import the client certificate public key is:

$cert = New-Object -TypeName System.Security.Cryptography.X509Certificates.X509Certificate2
$cert.Import("cert.pem")

$store_name = [System.Security.Cryptography.X509Certificates.StoreName]::TrustedPeople
$store_location = [System.Security.Cryptography.X509Certificates.StoreLocation]::LocalMachine
$store = New-Object -TypeName System.Security.Cryptography.X509Certificates.X509Store -ArgumentList $store_name, $store_location
$store.Open("MaxAllowed")
$store.Add($cert)
$store.Close()

Mapping a Certificate to an Account

Once the certificate has been imported, it needs to be mapped to the local user account.

This can be done with the following PowerShell command:

$username = "username"
$password = ConvertTo-SecureString -String "password" -AsPlainText -Force
$credential = New-Object -TypeName System.Management.Automation.PSCredential -ArgumentList $username, $password

# this is the issuer thumbprint which in the case of a self generated cert
# is the public key thumbprint, additional logic may be required for other
# scenarios
$thumbprint = (Get-ChildItem -Path cert:\LocalMachine\root | Where-Object { $_.Subject -eq "CN=$username" }).Thumbprint

New-Item -Path WSMan:\localhost\ClientCertificate `
    -Subject "$username@localhost" `
    -URI * `
    -Issuer $thumbprint `
    -Credential $credential `
    -Force

Once this is complete, the hostvar ansible_winrm_cert_pem should be set to the path of the public key and the ansible_winrm_cert_key_pem variable should be set to the path of the private key.

NTLM

NTLM is an older authentication mechanism used by Microsoft that can support both local and domain accounts. NTLM is enabled by default on the WinRM service, so no setup is required before using it.

NTLM is the easiest authentication protocol to use and is more secure than Basic authentication. If running in a domain environment, Kerberos should be used instead of NTLM.

Kerberos has several advantages over using NTLM:

• NTLM is an older protocol and does not support newer encryption protocols.
• NTLM is slower to authenticate because it requires more round trips to the host in the authentication stage.
• Unlike Kerberos, NTLM does not allow credential delegation.

This example shows host variables configured to use NTLM authentication:

ansible_user: LocalUsername
ansible_password: Password
ansible_connection: winrm
ansible_winrm_transport: ntlm

Kerberos

Kerberos is the recommended authentication option to use when running in a domain environment. Kerberos supports features like credential delegation and message encryption over HTTP and is one of the more secure options that is available through WinRM.

Kerberos requires some additional setup work on the Ansible host before it can be used properly.

The following example shows host vars configured for Kerberos authentication:

ansible_user: [email protected]
ansible_password: Password
ansible_connection: winrm
ansible_winrm_transport: kerberos

As of Ansible version 2.3, the Kerberos ticket will be created based on ansible_user and ansible_password. If running on an older version of Ansible or when ansible_winrm_kinit_mode is manual, a Kerberos ticket must already be obtained. See below for more details.

There are some extra host variables that can be set:

ansible_winrm_kinit_mode: managed/manual (manual means Ansible will not obtain a ticket)
ansible_winrm_kinit_cmd: the kinit binary to use to obtain a Kerberos ticket (default to kinit)
ansible_winrm_service: overrides the SPN prefix that is used, the default is ``HTTP`` and should rarely ever need changing
ansible_winrm_kerberos_delegation: allows the credentials to traverse multiple hops
ansible_winrm_kerberos_hostname_override: the hostname to be used for the kerberos exchange

Installing the Kerberos Library

Some system dependencies that must be installed prior to using Kerberos. The script below lists the dependencies based on the distro:

# Via Yum (RHEL/Centos/Fedora)
yum -y install python-devel krb5-devel krb5-libs krb5-workstation

# Via Apt (Ubuntu)
sudo apt-get install python-dev libkrb5-dev krb5-user

# Via Portage (Gentoo)
emerge -av app-crypt/mit-krb5
emerge -av dev-python/setuptools

# Via Pkg (FreeBSD)
sudo pkg install security/krb5

# Via OpenCSW (Solaris)
pkgadd -d http://get.opencsw.org/now
/opt/csw/bin/pkgutil -U
/opt/csw/bin/pkgutil -y -i libkrb5_3

# Via Pacman (Arch Linux)
pacman -S krb5

Once the dependencies have been installed, the python-kerberos wrapper can be install using pip:

pip install pywinrm[kerberos]

Configuring Host Kerberos

Once the dependencies have been installed, Kerberos needs to be configured so that it can communicate with a domain. This configuration is done through the /etc/krb5.conf file, which is installed with the packages in the script above.

To configure Kerberos, in the section that starts with:

[realms]

Add the full domain name and the fully qualified domain names of the primary and secondary Active Directory domain controllers. It should look something like this:

[realms]
    MY.DOMAIN.COM = {
        kdc = domain-controller1.my.domain.com
        kdc = domain-controller2.my.domain.com
    }

In the section that starts with:

[domain_realm]

Add a line like the following for each domain that Ansible needs access for:

[domain_realm]
    .my.domain.com = MY.DOMAIN.COM

You can configure other settings in this file such as the default domain. See krb5.conf for more details.

Automatic Kerberos Ticket Management

Ansible version 2.3 and later defaults to automatically managing Kerberos tickets when both ansible_user and ansible_password are specified for a host. In this process, a new ticket is created in a temporary credential cache for each host. This is done before each task executes to minimize the chance of ticket expiration. The temporary credential caches are deleted after each task completes and will not interfere with the default credential cache.

To disable automatic ticket management, set ansible_winrm_kinit_mode=manual via the inventory.

Automatic ticket management requires a standard kinit binary on the control host system path. To specify a different location or binary name, set the ansible_winrm_kinit_cmd hostvar to the fully qualified path to a MIT krbv5 kinit-compatible binary.

Manual Kerberos Ticket Management

To manually manage Kerberos tickets, the kinit binary is used. To obtain a new ticket the following command is used:

kinit [email protected]

To see what tickets (if any) have been acquired, use the following command:

klist

To destroy all the tickets that have been acquired, use the following command:

kdestroy

Troubleshooting Kerberos

Kerberos is reliant on a properly-configured environment to work. To troubleshoot Kerberos issues, ensure that:

• The hostname set for the Windows host is the FQDN and not an IP address.
• The forward and reverse DNS lookups are working properly in the domain. To test this, ping the windows host by name and then use the ip address returned with nslookup. The same name should be returned when using nslookup on the IP address.
• The Ansible host’s clock is synchronized with the domain controller. Kerberos is time sensitive, and a little clock drift can cause the ticket generation process to fail.

• Ensure that the fully qualified domain name for the domain is configured in the krb5.conf file. To check this, run:

  kinit -C [email protected]
  klist
  

  If the domain name returned by klist is different from the one requested, an alias is being used. The krb5.conf file needs to be updated so that the fully qualified domain name is used and not an alias.

CredSSP

CredSSP authentication is a newer authentication protocol that allows credential delegation. This is achieved by encrypting the username and password after authentication has succeeded and sending that to the server using the CredSSP protocol.

Because the username and password are sent to the server to be used for double hop authentication, ensure that the hosts that the Windows host communicates with are not compromised and are trusted.

CredSSP can be used for both local and domain accounts and also supports message encryption over HTTP.

To use CredSSP authentication, the host vars are configured like so:

ansible_user: Username
ansible_password: Password
ansible_connection: winrm
ansible_winrm_transport: credssp

There are some extra host variables that can be set as shown below:

ansible_winrm_credssp_disable_tlsv1_2: when true, will not use TLS 1.2 in the CredSSP auth process

CredSSP authentication is not enabled by default on a Windows host, but can be enabled by running the following in PowerShell:

Enable-WSManCredSSP -Role Server -Force

Installing CredSSP Library

The requests-credssp wrapper can be installed using pip:

pip install pywinrm[credssp]

CredSSP and TLS 1.2

By default the requests-credssp library is configured to authenticate over the TLS 1.2 protocol. TLS 1.2 is installed and enabled by default for Windows Server 2012 and Windows 8 and more recent releases.

There are two ways that older hosts can be used with CredSSP:

• Install and enable a hotfix to enable TLS 1.2 support (recommended for Server 2008 R2 and Windows 7).
• Set ansible_winrm_credssp_disable_tlsv1_2=True in the inventory to run over TLS 1.0. This is the only option when connecting to Windows Server 2008, which has no way of supporting TLS 1.2

To enable TLS 1.2 support on Server 2008 R2 and Windows 7, the optional update KRB3080079 needs to be installed.

Once the update has been applied and the Windows host rebooted, run the following PowerShell commands to enable TLS 1.2:

$reg_path = "HKLM:\SYSTEM\CurrentControlSet\Control\SecurityProvider\SCHANNEL\Protocols\TLS 1.2"
New-Item -Path $reg_path
New-Item -Path "$reg_path\Server"
New-Item -Path "$reg_path\Client"

New-ItemProperty -Path "$reg_path\Server" -Name "Enabled" -Value 1 -PropertyType DWord
New-ItemProperty -Path "$reg_path\Server" -Name "DisabledByDefault" -Value 0 -PropertyType DWord
New-ItemProperty -Path "$reg_path\Client" -Name "Enabled" -Value 1 -PropertyType DWord
New-ItemProperty -Path "$reg_path\Client" -Name "DisabledByDefault" -Value 0 -PropertyType DWord

Set CredSSP Certificate

CredSSP works by encrypting the credentials through the TLS protocol and uses a self-signed certificate by default. The CertificateThumbprint option under the WinRM service configuration can be used to specify the thumbprint of another certificate.

To explicitly set the certificate to use for CredSSP:

# note the value $certificate_thumbprint will be different in each
# situation, this needs to be set based on the cert that is used.
$certificate_thumbprint = "7C8DCBD5427AFEE6560F4AF524E325915F51172C"

# set the thumbprint value
Set-Item -Path WSMan:\localhost\Service\CertificateThumbprint -Value $certificate_thumbprint

Non-Administrator Accounts

WinRM is configured by default to only allow connections from accounts in the local Administrators group. This can be changed by running:

winrm configSDDL default

This will display an ACL editor, where new users or groups may be added. To run commands over WinRM, users and groups must have at least the Read and Execute permissions enabled.

While non-administrative accounts can be used with WinRM, most typical server administration tasks require some level of administrative access, so the utility is usually limited.

WinRM Encryption

By default WinRM will fail to work when running over an unencrypted channel. The WinRM protocol considers the channel to be encrypted if using TLS over HTTP (HTTPS) or using message level encryption. Using WinRM with TLS is the recommended option as it works with all authentication options, but requires a certificate to be created and used on the WinRM listener.

The ConfigureRemotingForAnsible.ps1 creates a self-signed certificate and creates the listener with that certificate. If in a domain environment, ADCS can also create a certificate for the host that is issued by the domain itself.

If using HTTPS is not an option, then HTTP can be used when the authentication option is NTLM, Kerberos or CredSSP. These protocols will encrypt the WinRM payload with their own encryption method before sending it to the server. The message-level encryption is not used when running over HTTPS because the encryption uses the more secure TLS protocol instead. If both transport and message encryption is required, set ansible_winrm_message_encryption=always in the host vars.

A last resort is to disable the encryption requirement on the Windows host. This should only be used for development and debugging purposes, as anything sent from Ansible can viewed by anyone on the network. To disable the encryption requirement, run the following from PowerShell on the target host:

Set-Item -Path WSMan:\localhost\Service\AllowUnencrypted -Value $true

Inventory Options

Ansible’s Windows support relies on a few standard variables to indicate the username, password, and connection type of the remote hosts. These variables are most easily set up in the inventory, but can be set on the host_vars/ group_vars level.

When setting up the inventory, the following variables are required:

# it is suggested that these be encrypted with ansible-vault:
# ansible-vault edit group_vars/windows.yml
ansible_connection: winrm

# may also be passed on the command-line via --user
ansible_user: Administrator

# may also be supplied at runtime with --ask-pass
ansible_password: SecretPasswordGoesHere

Using the variables above, Ansible will connect to the Windows host with Basic authentication through HTTPS. If ansible_user has a UPN value like [email protected] then the authentication option will automatically attempt to use Kerberos unless ansible_winrm_transport has been set to something other than kerberos.

The following custom inventory variables are also supported for additional configuration of WinRM connections:

• ansible_port: The port WinRM will run over, HTTPS is 5986 which is the default while HTTP is 5985
• ansible_winrm_scheme: Specify the connection scheme (http or https) to use for the WinRM connection. Ansible uses https by default unless ansible_port is 5985
• ansible_winrm_path: Specify an alternate path to the WinRM endpoint, Ansible uses /wsman by default
• ansible_winrm_realm: Specify the realm to use for Kerberos authentication. If ansible_user contains @, Ansible will use the part of the username after @ by default
• ansible_winrm_transport: Specify one or more authentication transport options as a comma-separated list. By default, Ansible will use kerberos, basic if the kerberos module is installed and a realm is defined, otherwise it will be plaintext
• ansible_winrm_server_cert_validation: Specify the server certificate validation mode (ignore or validate). Ansible defaults to validate on Python 2.7.9 and higher, which will result in certificate validation errors against the Windows self-signed certificates. Unless verifiable certificates have been configured on the WinRM listeners, this should be set to ignore
• ansible_winrm_operation_timeout_sec: Increase the default timeout for WinRM operations, Ansible uses 20 by default
• ansible_winrm_read_timeout_sec: Increase the WinRM read timeout, Ansible uses 30 by default. Useful if there are intermittent network issues and read timeout errors keep occurring
• ansible_winrm_message_encryption: Specify the message encryption operation (auto, always, never) to use, Ansible uses auto by default. auto means message encryption is only used when ansible_winrm_scheme is http and ansible_winrm_transport supports message encryption. always means message encryption will always be used and never means message encryption will never be used
• ansible_winrm_ca_trust_path: Used to specify a different cacert container than the one used in the certifi module. See the HTTPS Certificate Validation section for more details.
• ansible_winrm_send_cbt: When using ntlm or kerberos over HTTPS, the authentication library will try to send channel binding tokens to mitigate against man in the middle attacks. This flag controls whether these bindings will be sent or not (default: True).
• ansible_winrm_*: Any additional keyword arguments supported by winrm.Protocol may be provided in place of *

In addition, there are also specific variables that need to be set for each authentication option. See the section on authentication above for more information.

IPv6 Addresses

IPv6 addresses can be used instead of IPv4 addresses or hostnames. This option is normally set in an inventory. Ansible will attempt to parse the address using the ipaddress package and pass to pywinrm correctly.

When defining a host using an IPv6 address, just add the IPv6 address as you would an IPv4 address or hostname:

[windows-server]
2001:db8::1

[windows-server:vars]
ansible_user=username
ansible_password=password
ansible_connection=winrm

HTTPS Certificate Validation

As part of the TLS protocol, the certificate is validated to ensure the host matches the subject and the client trusts the issuer of the server certificate. When using a self-signed certificate or setting ansible_winrm_server_cert_validation: ignore these security mechanisms are bypassed. While self signed certificates will always need the ignore flag, certificates that have been issued from a certificate authority can still be validated.

One of the more common ways of setting up a HTTPS listener in a domain environment is to use Active Directory Certificate Service (AD CS). AD CS is used to generate signed certificates from a Certificate Signing Request (CSR). If the WinRM HTTPS listener is using a certificate that has been signed by another authority, like AD CS, then Ansible can be set up to trust that issuer as part of the TLS handshake.

To get Ansible to trust a Certificate Authority (CA) like AD CS, the issuer certificate of the CA can be exported as a PEM encoded certificate. This certificate can then be copied locally to the Ansible controller and used as a source of certificate validation, otherwise known as a CA chain.

The CA chain can contain a single or multiple issuer certificates and each entry is contained on a new line. To then use the custom CA chain as part of the validation process, set ansible_winrm_ca_trust_path to the path of the file. If this variable is not set, the default CA chain is used instead which is located in the install path of the Python package certifi.

Limitations

Due to the design of the WinRM protocol , there are a few limitations when using WinRM that can cause issues when creating playbooks for Ansible. These include:

• Credentials are not delegated for most authentication types, which causes authentication errors when accessing network resources or installing certain programs.
• Many calls to the Windows Update API are blocked when running over WinRM.
• Some programs fail to install with WinRM due to no credential delegation or because they access forbidden Windows API like WUA over WinRM.
• Commands under WinRM are done under a non-interactive session, which can prevent certain commands or executables from running.
• You cannot run a process that interacts with DPAPI, which is used by some installers (like Microsoft SQL Server).

Some of these limitations can be mitigated by doing one of the following:

• Set ansible_winrm_transport to credssp or kerberos (with ansible_winrm_kerberos_delegation=true) to bypass the double hop issue and access network resources
• Use become to bypass all WinRM restrictions and run a command as it would locally. Unlike using an authentication transport like credssp, this will also remove the non-interactive restriction and API restrictions like WUA and DPAPI
• Use a scheduled task to run a command which can be created with the win_scheduled_task module. Like become, this bypasses all WinRM restrictions but can only run a command and not modules.