API Key and HMAC Authentication for inbound REST APIs › Token-based authentication › API Authentication › Authentication › Access Management

Release: Australia · Updated: 2026-03-12 · Official documentation · View source

Configure HMAC - Token-based authentication

Configure HMAC to support authentication for REST API endpoints.

Before you begin

Role required: api_service_admin, adaptive_auth_policy_admin

Plugin required: API Key and HMAC Authentication (com.glide.tokenbased_auth)

Note: While configuring the HMAC, ensure the name of the script that starts with HMAC to populated in the script list view.

Procedure

Create an HMAC configuration.
1. Navigate to All > System Web Services > API Access Policies > HMAC Configuration.
2. Select New.
  
  Note: You can also use the Default HMAC SHA256 Base64 Encoding which is created when installing the plugin.
3. On the form, fill the fields:

Field	Description
Name	Name for the HMAC configuration.
Application	Scope of the configuration.
Description	Detailed description about the configuration.
Hash Algorithm	Choose the Hash Algorithm. Options available:- HmacSHA256 - HmacSHA384 - HmacSHA512
HMAC util script	Utility script for HMAC.Note: If you validate HMAC authentication using Request body, Time stamp and Secret with no Key Id, then do the following: Create a customized script include as HMAC util script Use that script include util to interpret the passed in timestamp, and request body. For every shared secret created in the ServiceNow® instance, there is a key ID. You need to configure the key ID into Default key id in HMAC auth profile.

Image omitted: configure-hmac.png
HMAC Configuration

4.  Submit the record.

Create an inbound authentication profile.
1. Navigate to All > System Web Services > API Access Policies > Inbound Authentication Profiles.
2. Select New.
  
  The system displays the message What kind of authentication profile?
3. Select Create HMAC authentication profiles.

Image omitted: hmac-profile.png
HMAC authentication profile

4.  On the form, fill in the fields.

Field	Description
Name	Name to identify the authentication policy.
Application	Scope of the authentication policy.
Configuration for HMAC	Select the HMAC configuration that was created.
Auth Parameter	Select the auth parameter for the authentication request. You can select the default options or create a new auth parameter:- x-sn-hmac-signature-256: Auth Header - x-sn-hmac-signature-256: Query Parameter
Default Key ID of Shared Secret	The token information that can be updated in this field for using HMAC.

    **Note:** The selected option has to be defined in the REST call as part of the Auth Header or Query Parameter.

Image omitted: hmac-parameter.png
HMAC Profile

5.  Submit the form.

Create an HMAC secret.
1. Navigate to All > System Web Services > API Access Policies > REST API HMAC Secret.
2. Select New.
3. On the form, fill the fields:

Field	Description
Name	Name to identify the REST API HMAC secret.
Description	Description for the REST API HMAC secret.
Active	Status of the REST API HMAC secret.
User	User associated to the REST API HMAC secret. Use the look-up icon to select the user.
Key ID	Key ID that must be sent as part of the REST call. Key ID is generated after submitting the form.
Shared Secret	Shared secrets of the user. For example, the password.
Source	Source of the record.
Expiry	Time after which the credential is no longer valid. Empty value means no expiration.Note: For more information, about expiry of token, see Cleaning up token Expiry .

4.  Submit the form.

5.  Open the record that was created.

    Find the Key ID generated by the ServiceNow AI Platform for the user.

Image omitted: hmac-key.png
HMAC Key ID

    **Note:** You can add the Key ID that was generated during the Key ID in the Authentication Profile that was created for HMAC if you don't want to specify the Auth or Query parameter for the API call.

Create a REST API access policy.
1. Navigate to All > System Web Services > REST API Access Policies.
2. Select New.
3. On the form, fill in the fields.

Field	Description
Name	Unique name of the API access policy.
Active	Option to make the API access policy active.
REST API	The REST API to which the access policy is applied. For example, Attachment API.
REST API PATH	API path of the REST API. This field is auto-populated based on the selected REST API. For example, now/attachment.
HTTP Method	Method used for interacting with the API. This field is auto-populated based on the selected REST API.
Version	Version of the API. For example, v1. This field is auto-populated based on the selected REST API.Note: If you want to create an authentication policy for all versions of a REST API, you must create individual policies for each version.
Resource	Child resource of the REST API. This field is auto-populated based on the selected REST API. For example, /now/attachment
Application	Scope of the application.
Global	Enable this field to apply auth policy to all methods, versions, and resources for the API.Note: Token Based Auth isn’t allowed in the Global REST API Policy.
Apply to all methods	Enable this field to apply the auth policy for the API to all the methods, versions, and resources for the API.
Apply to all resources	Enable this field to apply the auth policy for the API to all the versions.
Apply to all versions	Enable this field to apply the auth policy for the API to all the resources.

4.  Add the API authentication profile that was created.

Image omitted: hmac-profile-added.png
HMAC Profile added to Access Policy

5.  Submit the form.

    You can send the REST API call:

    -   With the x-sn-hmac-signature-256 that was generated by ServiceNow® during the API Key creation within the Header or Query parameter based on the configuration for authentication.
    -   With pre-request Script with Shared Secret specified as part of the request.
    **Warning:** Use **POST** request when submitting any sensitive information to the server.