pypsrp

pypsrp - Python PowerShell Remoting Protocol Client library

pypsrp is a Python client for the PowerShell Remoting Protocol (PSRP) and Windows Remote Management (WinRM) service. It allows your to execute commands on a remote Windows host from any machine that can run Python.

This library exposes 4 different types of APIs;

• A simple client API that can copy files to and from the remote Windows host as well as execute processes and PowerShell scripts
• A WSMan interface to execute various WSMan calls like Send, Create, Connect, Disconnect, etc
• A Windows Remote Shell (WinRS) layer that executes cmd commands and executables using the base WinRM protocol
• A PowerShell Remoting Protocol (PSRP) layer allows you to create remote Runspace Pools and PowerShell pipelines

At a basic level, you can use this library to;

• Execute a cmd command
• Run another executable
• Execute PowerShell scripts
• Copy a file from the localhost to the remote Windows host
• Fetch a file from the remote Windows host to the localhost
• Create a Runspace Pool that contains one or multiple PowerShell pipelines and execute them asynchronously
• Support for a reference host base implementation of PSRP for interactive scripts

Currently this library only supports the WSMan transport method but is designed to support SSH at some point in the future (PR's are welcome). By default it supports the following authentication methods with WSMan;

• Basic
• Certificate
• NTLM

It also supports Negotiate/Kerberos, and CredSSP but require extra libraries to be installed.

Requirements

See How to Install for more details

• CPython 3.6+
• cryptography
• pyspnego
• requests

Optional Requirements

The following Python libraries can be installed to add extra features that do not come with the base package:

• python-gssapi for Kerberos authentication on Linux
• pykrb5 for Kerberos authentication on Linux
• requests-credssp for CredSSP authentication

How to Install

To install pypsrp with all the basic features, run:

pip install pypsrp

Kerberos Authentication

While pypsrp supports Kerberos authentication, it isn't included by default for Linux hosts due to it's reliance on system packages to be present.

To install these packages, depending on your distribution, run one of the following script blocks.

For Debian/Ubuntu

# For Python 2
apt-get install gcc python-dev libkrb5-dev

# For Python 3
apt-get install gcc python3-dev libkrb5-dev

# To add NTLM to the GSSAPI SPNEGO auth run
apt-get install gss-ntlmssp

For RHEL/Centos

yum install gcc python-devel krb5-devel

# To add NTLM to the GSSAPI SPNEGO auth run
yum install gssntlmssp

For Fedora

dnf install gcc python-devel krb5-devel

# To add NTLM to the GSSAPI SPNEGO auth run
dnf install gssntlmssp

For Arch Linux

pacman -S gcc krb5

Once installed you can install the Python packages with

pip install pypsrp[kerberos]

Kerberos also needs to be configured to talk to the domain but that is outside the scope of this page.

CredSSP Authentication

Like Kerberos auth, CredSSP is supported but isn't included by default. To add support for CredSSP auth try to run the following

pip install pypsrp[credssp]

If that fails you may need to update pip and setuptools to a newer version pip install -U pip setuptools.

How to Use

There are 3 main components that are in use within this library;

• Transport: Handles the raw transport of messages to and from the server
• Shell: Handles the WSMV or PSRP protocol details used to create the remote shell that processes are run on, uses Connection to send the details
• Process: Runs the process or script within a shell

Connection

Currently only the connection that is supported is the WSMan protocol over HTTP through pypsrp.wsman.WSMan and offers mostly all the same features in the WSMV spec including;

• Basic, Certificate, Negotiate, Kerberos, and CredSSP authentication
• TLS encryption
• Message encryption with Negotiate, Kerberos, and CredSSP authentication
• Definable proxy

These are the options that can be used to setup WSMan;

• server: The hostname or IP address of the host to connect to
• max_envelope_size: The maximum envelope size, in bytes, that can be sent to the server, default is 153600
• operation_timeout: The operation timeout, in seconds, of each WSMan operation, default is 20. This should always be lower than read_timeout.
• port: The port to connect to, default is 5986 if ssl=True else 5985
• username: The username to connect with, required for all auths except certificate and optionally required for negotiate/kerberos
• password: The password for username. Due to a bug on MacOS/Heimdal GSSAPI implementations, this will persist in the user's ccache when using Negotiate or Kerberos authentication, run kdestroy manually to remove this
• ssl: Whether to connect over https or https, default is True
• path: The WinRM path to connect to, default is wsman
• auth: The authentication protocol to use, default is negotiate, choices are basic, certificate, negotiate, ntlm, kerberos, credssp
• cert_validation: Whether to validate the server's SSL certificate, default is True. Can be False to not validate or a path to a PEM file of trusted certificates
• connection_timeout: The timeout for creating a HTTP connection, default is 30
• read_timeout: The timeout for receiving a response from the server after a request has been made, default is 30
• encryption: Controls the encryption settings, default is auto, choices are auto, always, never. Set to always to always run message encryption even over HTTPS, never to never use message encryption even over HTTP
• proxy: The proxy URL used to connect to the remote host
• no_proxy: Whether to ignore any environment proxy variable and connect directly to the host, default is False
• locale: The wsmv:Locale value to set on each WSMan request. This specifies the language in which the cleint wants response text to be translated, default is en-US
• data_locale: The wsmv:DataLocale value to set on each WSMan request. This specifies the format in which numerical data is presented in the response text, default is the value of locale
• reconnection_retries: Number of retries on a connection problem, default is 0
• reconnection_backoff: Number of seconds to backoff in between reconnection attempts (first sleeps X, then sleeps 2X, 4X, 8*X, ...), default is 2.0
• certificate_key_pem: The path to the certificate key used in certificate authentication
• certificate_pem: The path to the certificate used in certificate authentication
• credssp_auth_mechanism: The sub-auth mechanism used in CredSSP, default is auto, choices are auto, ntlm, or kerberos
• credssp_disable_tlsv1_2: Whether to used CredSSP auth over the insecure TLSv1.0, default is False
• credssp_minimum_version: The minimum CredSSP server version that the client will connect to, default is 2
• negotiate_delegate: Whether to negotiate the credential to the host, default is False. This is only valid if negotiate auth negotiated Kerberos or kerberos was explicitly set
• negotiate_hostname_override: The hostname used to calculate the host SPN when authenticating the host with Kerberos auth. This is only valid if negotiate auth negotiated Kerberos or kerberos was explicitly set
• negotiate_send_cbt: Whether to binding the channel binding token (HTTPS only) to the auth or ignore, default is True
• negotiate_service: Override the service part of the calculated SPN used when authenticating the server, default is WSMAN. This is only valid if negotiate auth negotiated Kerberos or kerberos was explicitly set

When running over HTTP, this library will enforce encryption by default but if that is not supported (Basic auth) or isn't available on the host then either use HTTPS or disable encryption with encryption="never".

There are plans to add support for SSH as a connection but this still needs to be implemented. SSH will work on hosts that are running PowerShell Core but not the standard PowerShell.

Shell

There are two shells that can be used in this library, pypsrp.shell.WinRS and pypsrp.powershell.RunspacePool.

WinRS is a cmd shell that can be used to issue cmd commands, including but not limited to other executables. Here are the options that can be used to configure a WinRS shell;

• wsman: WinRS only works over WSMan, so this is the pypsrp.wsman.WSMan object to run the commands over
• resource_uri: The resource uri of the shell, defaults to http://schemas.microsoft.com/wbem/wsman/1/windows/shell/cmd
• id: The ID if the shell, this should be kept as None as it is created dynamically by the server
• input_streams: The input stream(s) of the shell, default is stdin
• output_streams: The output stream(s) of the shell, default is stdout, stderr
• codepage: The codepage of the shell, default is the default of the host
• environment: A dictionary of environment key/values to set for the remote shell
• idle_time_out: THe idle timeout in seconds of the shell
• lifetime: The total lifetime of the shell
• name: The name (description only) of the shell
• no_profile: Whether to create the shell with the user profile loaded or not
• working_directory: The default working directory of the created shell

RunspacePool is a shell used by the PSRP protocol, it is designed to be a close implementation of the .NET System.Management.Automation.Runspaces.RunspacePool class. The methods and properties are similar and can mostly do the same thing. Here are the options that can be used to configure a RunspacePool shell;

• connection: The connection object used by the RunspacePool to send commands to the remote server, currently only supports WSMan
• apartment_state: The int value of pypsrp.complex_objects.ApartmentState for the remote thread, default is UNKNOWN
• thread_options: The int value of pypsrp.complex_objects.ThreadOptions that specifies the type of thread to create, default is DEFAULT
• host: The local host info implementation, default is no host
• configuration_name: The configuration name to connect to, default is Microsoft.PowerShell and can be used to specify the Just Enough Administration (JEA) to connect to
• min_runspaces: The minimuum number of runspaces that a pool can hold, default is 1
• max_runspaces: The maximum number of runspaces that a pool can hold. Each PowerShell pipeline is run in a single Runspace, default is 1
• session_key_timeout_ms: The maximum time to wait for a session key transfer from the server

Process

There are two process objects that can be used, pypsrp.shell.Process for the WinRS shell and pypsrp.powershell.PowerShell for the RunspacePool shell. These objects are ultimately used to execute commands, processes, or scripts on the remote host.

Process is used with the WinRS shell to execute a cmd command or another executable. The following options are used to configure the Process object;

• shell: The WinRS shell the process is run over
• executable: The executable or command to run
• arguments: A list of arguments to the executable or command, default is no arguments
• id: The ID of the created command, if not specified then this is dynamically created
• no_shell: Whether to create a command in the cmd shell or bypass it, default is False. If True then the executable must be the full path to the exe. This only works on older OS' before 2012 R2 (not including)

To execute the process, call .invoke(), the stdout, stderr, and rc properties contain the output of the command once complete.

PowerShell is used by the PSRP protocol, it is designed to be a close implementation of the System.Management.Automation.PowerShell class. The methods and properties are similar and can mostly do the same thing. Here are the options that can be used to configure a PowerShell process;

• runspace_pool: The RunspacePool object to run the PowerShell process on

To execute the process, call .invoke(), the output, had_erros, and streams contains the execution status and output information of the process. Before invoke can be called, cmdlets or scripts must be added. These can be done with the following methods;

• add_script: Add a raw PowerShell script to the pending commands
• add_cmdlet: Add a cmdlet to the pending commands
• add_parameters: Add a dictionary of key/value parameters to the last added command
• add_argument: Add a value argument to the last added command
• add_statement: Set the last command/script to be the end of that pipeline so the next command/script is like a newline

See the examples below for more details.

Examples

How to use the high level client API

from pypsrp.client import Client

# this takes in the same kwargs as the WSMan object
with Client("server", username="user", password="password") as client:

    # execute a cmd command
    stdout, stderr, rc = client.execute_cmd("dir")

    stdout, stderr, rc = client.execute_cmd("powershell.exe gci $pwd")
    sanitised_stderr = client.sanitise_clixml(stderr)

    # execute a PowerShell script
    output, streams, had_errors = client.execute_ps('''$path = "%s"
if (Test-Path -Path $path) {
    Remove-Item -Path $path -Force -Recurse
}
New-Item -Path $path -ItemType Directory''' % path)
    output, streams, had_errors = client.execute_ps("New-Item -Path C:\\temp\\folder -ItemType Directory")

    # copy a file from the local host to the remote host
    client.copy("~/file.txt", "C:\\temp\\file.txt")

    # fetch a file from the remote host to the local host
    client.fetch("C:\\temp\\file.txt", "~/file.txt")

How to use WinRS/Process to execute a command

from pypsrp.shell import Process, SignalCode, WinRS
from pypsrp.wsman import WSMan

# creates a http connection with no encryption and basic auth
wsman = WSMan("server", ssl=False, auth="basic", encryption="never",
              username="vagrant", password="vagrant")

with wsman, WinRS(wsman) as shell:
    process = Process(shell, "dir")
    process.invoke()
    process.signal(SignalCode.CTRL_C)

    # execute a process with arguments in the background
    process = Process(shell, "powershell", ["gci", "$pwd"])
    process.begin_invoke()  # start the invocation and return immediately
    process.poll_invoke()  # update the output stream
    process.end_invoke()  # finally wait until the process is finished
    process.signal(SignalCode.CTRL_C)

How to use RunspacePool/PowerShell to execute a PowerShell script/command

from pypsrp.powershell import PowerShell, RunspacePool
from pypsrp.wsman import WSMan

# creates a https connection with explicit kerberos auth and implicit credentials
wsman = WSMan("server", auth="kerberos", cert_validation=False))

with wsman, RunspacePool(wsman) as pool:
    # execute 'Get-Process | Select-Object Name'
    ps = PowerShell(pool)
    ps.add_cmdlet("Get-Process").add_cmdlet("Select-Object").add_argument("Name")
    output = ps.invoke()

    # execute 'Get-Process | Select-Object -Property Name'
    ps.add_cmdlet("Get-Process").add_cmdlet("Select-Object")
    ps.add_parameter("Property", "Name")
    ps.begin_invoke()  # execute process in the background
    ps.poll_invoke()  # update the output streams
    ps.end_invoke()  # wait until the process is finished

    # execute 'Get-Process | Select-Object -Property Name; Get-Service audiosrv'
    ps.add_cmdlet("Get-Process").add_cmdlet("Select-Object").add_parameter("Property", "Name")
    ps.add_statement()
    ps.add_cmdlet("Get-Service").add_argument("audiosrc")
    ps.invoke()

    # execute a PowerShell script with input being sent
    script = '''begin {
    $DebugPreference = "Continue"
    Write-Debug -Message "begin"
} process {
    Write-Output -InputObject $input
} end {
    Write-Debug -Message "end"
}
'''
    ps.add_script(script)
    ps.invoke(["string", 1])
    print(ps.output)
    print(ps.streams.debug)

Logging

This library takes advantage of the Python logging configuration and messages are logged to the pypsrp named logger as well as pypsrp.* where * is each Python script in the pypsrp directory.

An easy way to turn on logging for the entire library is to create the following JSON file and run your script with PYPSRP_LOG_CFG=log.json python script.py (this does not work with Python 2.6).

{
    "version": 1,
    "disable_existing_loggers": false,
    "formatters": {
        "simple": {
            "format": "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
        }
    },

    "handlers": {
        "console": {
            "class": "logging.StreamHandler",
            "level": "DEBUG",
            "formatter": "simple",
            "stream": "ext://sys.stdout"
        }
    },

    "loggers": {
        "pypsrp": {
            "level": "DEBUG",
            "handlers": ["console"],
            "propagate": "no"
        }
    }
}

You can adjust the log level by changing the level value in logger to INFO.

Note: DEBUG contains a lot of information and will output all the messages sent to and from the client. This can have the side effect of leaking sensitive information and should only be used for debugging purposes.

Testing

Any changes are more than welcome in pull request form, you can run the current test suite with tox like so;

# make sure tox is installed
pip install tox

# run the tox suite
tox

# or run the test manually for the current Python environment
py.test -v --pep8 --cov pypsrp --cov-report term-missing

A lot of the tests either simulate a remote Windows host but you can also run a lot of them against a real Windows host. To do this, set the following environment variables before running the tests;

• PYPSRP_SERVER: The hostname or IP of the remote host
• PYPSRP_USERNAME: The username to connect with
• PYPSRP_PASSWORD: The password to connect with
• PYPSRR_PORT: The port to connect with (default: 5986)
• PYPSRP_AUTH: The authentication protocol to auth with (default: negotiate)

There are further integration tests that require a specific host setup to run correctly. You can use Vagrant to set this host up. This is done by running the following commands;

# download the Vagrant box and start it up based on the Vagrantfile
vagrant up

# once the above script is complete run the following
vagrant ssh  # password is vagrant

powershell.exe
Register-PSSessionConfiguration -Path "C:\Users\vagrant\Documents\JEARoleSettings.pssc" -Name JEARole -Force

$sec_pass = ConvertTo-SecureString -String "vagrant" -AsPlainText -Force
$credential = New-Object -TypeName System.Management.Automation.PSCredential -ArgumentList "vagrant", $sec_pass
$thumbprint = (Get-ChildItem -Path Cert:\LocalMachine\TrustedPeople)[0].Thumbprint

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


# exit the remote PowerShell session
exit

# exist the SSH session
exit

Once complete, set the following environment variables to run the integration tests;

• PYPSRP_RUN_INTEGRATION: To any value
• PYPSRP_SERVER: Set to 127.0.0.1
• PYPSRP_USERNAME: Set to vagrant
• PYPSRP_PASSWORD: Set to vagrant
• PYPSRP_HTTP_PORT: Set to 55985
• PYPSRP_HTTPS_PORT: Set to 55986
• PYPSRP_CERT_DIR: Set to the full path of the project directory

From here you can run the normal test suite and it will run all the integration tests.

Backlog

• Look at implementing the following transport options
  • Named pipes
  • SSH
• Update CI to use named pipes for integration tests
• Add Ansible playbook for better integration tests
• Improved serialization between Python and .NET objects
• Live interactive console for PSRP