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Add support for authenticating with OAuth Client Credential Grant #292

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63 changes: 42 additions & 21 deletions ServiceNow/Private/Get-ServiceNowAuth.ps1
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Original file line number Diff line number Diff line change
Expand Up @@ -38,31 +38,52 @@ function Get-ServiceNowAuth {
if ($ServiceNowSession.Version) { $hashOut.uri = $hashOut.uri + $ServiceNowSession.Version }

# check if we need a new access token
if ( $ServiceNowSession.ExpiresOn -lt (Get-Date) -and $ServiceNowSession.RefreshToken -and $ServiceNowSession.ClientCredential ) {
# we've expired and have a refresh token
$refreshParams = @{
Uri = 'https://{0}/oauth_token.do' -f $ServiceNowSession.Domain
Method = 'POST'
ContentType = 'application/x-www-form-urlencoded'
Body = @{
grant_type = 'refresh_token'
client_id = $ServiceNowSession.ClientCredential.UserName
client_secret = $ServiceNowSession.ClientCredential.GetNetworkCredential().password
refresh_token = $ServiceNowSession.RefreshToken.GetNetworkCredential().password
}
if ( $ServiceNowSession.ExpiresOn -lt (Get-Date) -and $ServiceNowSession.ClientCredential ) {

# Build refresh/re-auth body based on grant type
$refreshBody = @{
client_id = $ServiceNowSession.ClientCredential.UserName
client_secret = $ServiceNowSession.ClientCredential.GetNetworkCredential().password
}

$response = Invoke-RestMethod @refreshParams

$ServiceNowSession.AccessToken = New-Object System.Management.Automation.PSCredential('AccessToken', ($response.access_token | ConvertTo-SecureString -AsPlainText -Force))
$ServiceNowSession.RefreshToken = New-Object System.Management.Automation.PSCredential('RefreshToken', ($response.refresh_token | ConvertTo-SecureString -AsPlainText -Force))
if ($response.expires_in) {
$ServiceNowSession.ExpiresOn = (Get-Date).AddSeconds($response.expires_in)
Write-Verbose ('Access token has been refreshed and will expire at {0}' -f $ServiceNowSession.ExpiresOn)
if ($ServiceNowSession.GrantType -eq 'client_credentials') {
# Client credentials: re-authenticate (no refresh token available)
$refreshBody['grant_type'] = 'client_credentials'
}
elseif ($ServiceNowSession.RefreshToken) {
# Password grant: use refresh token
$refreshBody['grant_type'] = 'refresh_token'
$refreshBody['refresh_token'] = $ServiceNowSession.RefreshToken.GetNetworkCredential().password
}
else {
Write-Warning 'Access token expired but no refresh method available'
}

if ($refreshBody.ContainsKey('grant_type')) {
$refreshParams = @{
Uri = 'https://{0}/oauth_token.do' -f $ServiceNowSession.Domain
Method = 'POST'
ContentType = 'application/x-www-form-urlencoded'
Body = $refreshBody
}

# ensure script/module scoped variable is updated
$script:ServiceNowSession = $ServiceNowSession
$response = Invoke-RestMethod @refreshParams

$ServiceNowSession.AccessToken = New-Object System.Management.Automation.PSCredential('AccessToken', ($response.access_token | ConvertTo-SecureString -AsPlainText -Force))

# Update refresh token if provided (password grant only)
if ($response.refresh_token) {
$ServiceNowSession.RefreshToken = New-Object System.Management.Automation.PSCredential('RefreshToken', ($response.refresh_token | ConvertTo-SecureString -AsPlainText -Force))
}

if ($response.expires_in) {
$ServiceNowSession.ExpiresOn = (Get-Date).AddSeconds($response.expires_in)
Write-Verbose ('Access token has been refreshed and will expire at {0}' -f $ServiceNowSession.ExpiresOn)
}

# ensure script/module scoped variable is updated
$script:ServiceNowSession = $ServiceNowSession
}
}

if ( $ServiceNowSession.AccessToken ) {
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44 changes: 32 additions & 12 deletions ServiceNow/Public/New-ServiceNowSession.ps1
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Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,7 @@ function New-ServiceNowSession {

[Parameter(Mandatory, ParameterSetName = 'OAuth')]
[Parameter(Mandatory, ParameterSetName = 'OAuthProxy')]
[Parameter(Mandatory, ParameterSetName = 'OAuthClientCredential')]
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@gdbarron gdbarron Jan 31, 2026 •
edited
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we'll need to add a OAuthClientCredentialProxy paramset for ClientCredential, Proxy, and ProxyCredential params.

[System.Management.Automation.PSCredential] $ClientCredential,

[Parameter(Mandatory, ParameterSetName = 'AccessToken')]
Expand Down Expand Up @@ -160,19 +161,32 @@ function New-ServiceNowSession {
}

$script:PSDefaultParameterValues['Invoke-WebRequest:TimeoutSec'] = $TimeoutSec
$script:PSDefaultParameterValues['Invoke-RestMethodt:TimeoutSec'] = $TimeoutSec
$script:PSDefaultParameterValues['Invoke-RestMethod:TimeoutSec'] = $TimeoutSec

switch -Wildcard ($PSCmdLet.ParameterSetName) {
'OAuth*' {
# Determine OAuth grant type and build request body
$oauthBody = @{
'client_id' = $ClientCredential.UserName
'client_secret' = $ClientCredential.GetNetworkCredential().Password
}

if ($PSCmdLet.ParameterSetName -eq 'OAuthClientCredential') {
# Client Credentials Grant (machine-to-machine)
$oauthBody['grant_type'] = 'client_credentials'
$grantType = 'client_credentials'
}
else {
# Password Grant (user credentials)
$oauthBody['grant_type'] = 'password'
$oauthBody['username'] = $Credential.UserName
$oauthBody['password'] = $Credential.GetNetworkCredential().Password
$grantType = 'password'
}

$params = @{
Uri = 'https://{0}/oauth_token.do' -f $Url
Body = @{
'grant_type' = 'password'
'client_id' = $ClientCredential.UserName
'client_secret' = $ClientCredential.GetNetworkCredential().Password
'username' = $Credential.UserName
'password' = $Credential.GetNetworkCredential().Password
}
Body = $oauthBody
Method = 'Post'
UseBasicParsing = $true
}
Expand All @@ -198,18 +212,24 @@ function New-ServiceNowSession {
if ( $response.Content ) {
$token = $response.Content | ConvertFrom-Json
$newSession.Add('AccessToken', (New-Object System.Management.Automation.PSCredential('AccessToken', ($token.access_token | ConvertTo-SecureString -AsPlainText -Force))))
$newSession.Add('RefreshToken', (New-Object System.Management.Automation.PSCredential('RefreshToken', ($token.refresh_token | ConvertTo-SecureString -AsPlainText -Force))))

# Password grant returns refresh_token, client credentials does not
if ($token.refresh_token) {
$newSession.Add('RefreshToken', (New-Object System.Management.Automation.PSCredential('RefreshToken', ($token.refresh_token | ConvertTo-SecureString -AsPlainText -Force))))
}

if ($token.expires_in) {
$expiryTime = (Get-Date).AddSeconds($token.expires_in)
$newSession.Add('ExpiresOn', $expiryTime)
Write-Verbose "Access token will expire at $expiryTime"
}
# store client credential as it will be needed to refresh the access token
$newSession.Add('ClientCredential', $ClientCredential)

# Store credentials and grant type for token refresh
$newSession.Add('ClientCredential', $ClientCredential)
$newSession.Add('GrantType', $grantType)
} else {
# invoke-webrequest didn't throw an error, but we didn't get a token back either
throw ('"{0} : {1}' -f $response.StatusCode, $response | Out-String )
throw ('{0} : {1}' -f $response.StatusCode, $response | Out-String )
}
}

Expand Down