Endpoints

Endpoint configuration for Universal APIs.

Endpoints are defined by their URI and HTTP method. Calls made to the Universal server that match the API endpoint and method that you define will execute the API endpoint script.

New-PSUEndpoint -Url '/endpoint' -Method 'GET' -Endpoint {
   "Hello, world!"
}

To invoke the above method, you could use Invoke-RestMethod.

Invoke-RestMethod http://localhost:5000/endpoint

When defining endpoints in the management API, you can skip the New-PSUEndpoint call as it will be defined by the admin console.

The only contents that you need to provide in the editor will be the script you wish to call.

Variable URL

URLs can contain variable segments. You can denote a variable segment using a colon (:). For example, the following URL would provide a variable for the ID of the user. The $Id variable will be defined within the endpoint when it is executed. Variables must be unique in the same endpoint URL.

New-PSUEndpoint -Url '/user/:id' -Method 'GET' -Endpoint {
   Get-User -Id $Id
}

To call this API and specify the ID, you would do the following.

Invoke-RestMethod http://localhost:5000/user/123

Query String Parameters

Query string parameters are automatically passed into endpoints as variables that you can then access. For example, if you had an endpoint that expected an $Id variable, it could be provided via the query string.

New-PSUEndpoint -Url '/user' -Method 'GET' -Endpoint {
   Get-User -Id $Id
}

The resulting Invoke-RestMethod call must then include the query string parameter.

Invoke-RestMethod http://localhost:5000/user?Id=123

Security Considerations

When accepting input via Query String parameters you may be vulnerable to CWE-914: Improper Control of Dynamically-Identified Variables. Consider using a param block to ensure that only valid parameters are provided to the endpoint.

Below is an example of CWE-914. A $IsChallengePassed query string parameter could be included to bypass the challenge.

New-PSUEndpoint -Url "/api/v1.0/CWE914Test" -Description "Vulnerable to CWE-914" -Endpoint {
	if($ChallengeInputData -eq "AcceptableInput") {
		$IsChallengePassed = $true
	}
	if($IsChallengePassed) {
		"Challenge passed. Here is Sensitive Information"
	} else {
		"Challenge not passed"
	}
}

In order to avoid this particular issue, you can use a param block.

New-PSUEndpoint -Url "/api/v1.0/CWE914Test" -Description "Not Vulnerable to CWE-914" -Endpoint {
	Param(
		$ChallengeInputData
	)
	if($ChallengeInputData -eq "AcceptableInput") {
		$IsChallengePassed = $true
	}
	if($IsChallengePassed) {
		"Challenge passed. Here is Sensitive Information"
	} else {
		"Challenge not passed"
	}
}

Body

To access a request body, you will simply access the $Body variable. Universal $Body variable will be a string. If you expect JSON, you should use ConvertFrom-Json.

New-PSUEndpoint -Url '/user' -Method Post -Endpoint {
    $User = ConvertFrom-Json $Body 
    New-User $User
}

To call the above endpoint, you would have to specify the body of Invoke-RestMethod.

Invoke-RestMethod http://localhost:5000/user -Method Post -Body "{'username': 'adam'}"

Form Data

You can pass data to an endpoint as form data. Form data will be passed into your endpoint as parameters.

New-PSUEndpoint -Url '/user' -Method Post -Endpoint {
    param([Parameter(Mandatory)]$userName, $FirstName, $LastName)
     
    New-User $UserName -FirstName $FirstName -LastName $LastName
}

You can then use a hashtable with Invoke-RestMethod to pass form data.

Invoke-RestMethod http://localhost:5000/user -Method Post -Body @{ 
    UserName = "adriscoll"
    FirstName = "Adam"
    LastName = "Driscoll"
}

JSON Data

PowerShell Universal 2.6 or later required.

You can pass JSON data to an endpoint and it will automatically bind to a param block.

New-PSUEndpoint -Url '/user' -Method Post -Endpoint {
    param([Parameter(Mandatory)]$userName, $FirstName, $LastName)
     
    New-User $UserName -FirstName $FirstName -LastName $LastName
}

You can then send JSON data to the endpoint.

Invoke-RestMethod http://localhost:5000/user -Method Post -Body (@{ 
    UserName = "adriscoll"
    FirstName = "Adam"
    LastName = "Driscoll"
} | ConvertTo-Json) -ContentType 'application/json'

Param Block

You can use a param block within your script to enforce mandatory parameters and provide default values for optional parameters such as query string parameters. Variables such as $Body, $Headers and $User are provided automatically.

In the below example, the $Name parameter is mandatory and the $Role parameter has a default value of Default.

New-PSUEndpoint -Url '/user/:name' -Endpoint {
    param([Parameter(Mandatory)$Name, $Role = "Default")
}

Returning Data

Data returned from endpoints will be assumed to be JSON data. If you return an object from the endpoint script block, it will be automatically serialized to JSON. If you want to return another type of data, you can return a string formatted however you chose.

Processing Files

Uploading Files

You can process uploaded files by using the $Data parameter to access the byte array of data uploaded to the endpoint.

New-PSUEndpoint -Url '/file' -Method Post -Endpoint {
    $Data
}

PS C:\Users\adamr> iwr http://localhost:5000/file -method post -InFile '.\Desktop\add-dashboard.png'

StatusCode        : 200
StatusDescription : OK
Content           : [137,80,78,71,13,10,26,10,0,0,0,13,73,72,68,82,0,0,2,17,0,0,1,92,8,2,0,0,0,249,210,123,106,0,0,0,1,
                    115,82,71,66,0,174,206,28,233,0,0,0,4,103,65,77,65,0,0,177,143,11,252,97,5,0,0,0,9,112,72,89,115,0,
                    0,…

You could also save the file into a directory.

New-PSUEndpoint -Url '/file' -Method Post -Endpoint {
    [IO.File]::WriteAllBytes("tempfile.dat", $Data)
}

Downloading Files

You can send files down using the New-PSUApiResponse cmdlet.

New-PSUEndpoint -Url '/image' -Endpoint {
    $ImageData = [IO.File]::ReadAllBytes("image.jpeg")
    New-PSUApiResponse -ContentType 'image/jpg' -Data $ImageData
}

Returning Custom Responses

You can return custom responses from endpoints by using the New-PSUApiResponse cmdlet in your endpoint. This cmdlet allows you to set the status code, content type and even specify the byte[] data for the content to be returned.

New-PSUEndpoint -Url '/file' -Method Get -Endpoint {
    New-PSUApiResponse -StatusCode 410
}

You can also return custom body data by using the -Body parameter of New-PSUApiResponse.

New-PSUEndpoint -Url '/file' -Method Get -Endpoint {
    New-PSUApiResponse -Body "Not what you're looking for." -StatusCode 404
}

Invoking the REST method will return the custom error code.

PS C:\Users\adamr\Desktop> invoke-restmethod http://localhost:8080/file

Invoke-RestMethod: Not what you're looking for.

You can control the content type of the data that is returned by using the -ContentType parameter.

New-PSUEndpoint -Url '/file' -Method Get -Endpoint {
    New-PSUApiResponse -Body "<xml><node>1</node><node2>2</node2></xml>" -ContentType 'text/xml'
}

Documenting APIs

APIs that you create will automatically be added to the OpenAPI documentation that is generated by PowerShell Universal. You can access the Swagger documentation page by navigating to Security \ Tokens and clicking API Documentation. All your custom endpoints will be listed under APIs.

Help Text

You can specify help text for your APIs using comment-based help. Including a synopsis, description and parameter descriptions will result in each of those pieces being documented in the OpenAPI documentation and Swagger age.

For example, with a simple /get/:id endpoint, we could have comment-based help such as this.

<# 
.SYNOPSIS
This is an endpoint

.DESCRIPTION
This is a description

.PARAMETER ID
This is an ID.

#>
param($ID)
    
$Id

The resulting Swagger page will show each of these descriptions.

Persistent Runspaces

Persistent runspaces allow you to maintain runspace state between API calls. This is important for users that perform some sort of initialization within their endpoints that they do not want to execute on subsequent API calls.

By default, runspaces will be reset after each execution. This will cause variables, modules and functions defined during the execution of the API to be removed.

To enable persistent runspaces, you will need to configure an environment for your API. Set the -PersistentRunspace parameter to enable this feature. This is configured in the environments.ps1 script.

New-PSUEnvironment -Name 'Env' -Path 'powershell.exe' -PersistentRunspace

You can then assign the API environment in the settings.ps1 script.

Set-PSUSetting -ApiEnvironment 'Env'

Timeout

Available in PowerShell Universal 2.8 or later.

By default, endpoints will not time out. To set a timeout for your endpoints, you can use the New-PSUEndpoint -Timeout parameter. The timeout is set in the number of seconds.

External Endpoint Content

Available in PowerShell Universal 2.10 or later.

You can define the path to an external endpoint content file by using the -Path parameter of New-PSUEndpoint. The path is relative to the Repository directory. For example, the file layout would appear like this.

The content of the endpoints.ps1 file is then this.

New-PSUEndpoint -Url "/path" -Path "endpoint-path.ps1"

API

PreviousAbout NextSecurity

Last updated 2 years ago