Obtain REST API access in a user context

For some scenarios, you might need to get REST API access in a user context by using the device authorization flow. The steps to set this up have been documented in PowerShell, but any language will do. Here is how it works:

1. Query the well-known OpenID configuration endpoint to retrieve the server’s token and device authorization endpoints:

try {
    $wellKnownResponse = Invoke-RestMethod -Method Get -Uri $wellKnownEndpoint

    $tokenEndpoint = $wellKnownResponse.token_endpoint
    $deviceCodeEndpoint = $wellKnownResponse.device_authorization_endpoint
} catch {
    Write-Error "Error obtaining server information"
    exit
}

1. Send a request to the device authorization endpoint for a device code, a user code, a verification URL, and a complete verification URL, as well as details regarding how long the codes are valid and how often to check. Then, either open a browser to the complete verification URL, or direct the user to manually enter their or her user code and approve the device access request:

$body = "client_id=$clientId&scope=$([uri]::EscapeDataString($scope))"

try {
    $deviceCodeResponse = Invoke-RestMethod -Method Post -Uri $deviceCodeEndpoint `
                            -ContentType "application/x-www-form-urlencoded" -Body $body
} catch {
    Write-Error "Failed to obtain device code: $_"
    exit
}

# Extract values from the response (field names may vary by provider)
$device_code               = $deviceCodeResponse.device_code
$user_code                 = $deviceCodeResponse.user_code
$verification_uri          = $deviceCodeResponse.verification_uri
$verification_uri_complete = $deviceCodeResponse.verification_uri_complete
$interval                  = 10   # in seconds
$expires_in                = $deviceCodeResponse.expires_in   # in seconds

# Provide a default interval if none was returned or if it's zero/null
if (-not $interval -or $interval -eq 0) {
    $interval = 5
    Write-Host "Interval not provided or invalid; defaulting to $interval seconds."
}

# Instead of instructing the user, open the browser to the verification_uri_complete
if ($verification_uri_complete) {
    Write-Host "Opening browser for device authorization..."
    Start-Process $verification_uri_complete
} else {
    Write-Host "verification_uri_complete not provided. Please manually go to $verification_uri and enter the code: $user_code"
}

1. Start a loop that periodically sends a request to the token endpoint with the device code and client ID until the server returns an access token:

$startTime = Get-Date
$tokenResponse = $null

while (((Get-Date) - $startTime).TotalSeconds -lt $expires_in) {
    Start-Sleep -Seconds $interval

    try {# Build the POST body to exchange the device code for an access token
        $tokenBody = "grant_type=urn:ietf:params:oauth:grant-type:device_code&client_id=$clientId&device_code=$device_code"
        $tokenResponse = Invoke-RestMethod -Method Post -Uri $tokenEndpoint -ContentType "application/x-www-form-urlencoded" -Body $tokenBody

        if ($tokenResponse.access_token) {
            Write-Host "Access token obtained:" $tokenResponse.access_token
            break
        }
    }
    catch {# Instead of reading the response content (which may be disposed), use the exception message.
        $errorMessage = $_.Exception.Message

        # Check if the exception message indicates that authorization is still pending.
        if ($errorMessage -match "authorization_pending") {
            Write-Host "Authorization pending..."
            continue
        }
        else {
            Write-Error "Error during token polling: $errorMessage"
            break
        }
    }
}

if (-not $tokenResponse -or -not $tokenResponse.access_token) {
    Write-Host "Failed to obtain an access token or authorization expired."
}

1. When needed, use the refresh token obtained during step #1 to request a new token from the token endpoint, ensuring continued access to the application:

$body = "grant_type=refresh_token&authorization=bearer $($tokenResponse.access_token)&refresh_token=$($tokenResponse.refresh_token)&client_id=dvls"

try {
    $refreshResponse = Invoke-RestMethod -Method Post -Uri $tokenEndpoint -ContentType "application/x-www-form-urlencoded" -Body $body

    if ($refreshResponse.access_token) {
        Write-Host "Access token obtained:" $tokenResponse.access_token
        break
    }
} catch {
    Write-Error "Failed to obtain device code: $_"
    exit
}

See Okta's documentation for more information on the Device Authorization Flow.

See also

• REST API documentation