Skip to main content
Workload Identity Practices
Workload Identity Practices
draft-ietf-wimse-workload-identity-practices-03
| Document | Type | Active Internet-Draft (wimse WG) | |
|---|---|---|---|
| Authors | Arndt Schwenkschuster , Yaroslav Rosomakho | ||
| Last updated | 2025-10-17 | ||
| Replaces | draft-ietf-wimse-workload-identity-bcp | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-wimse-workload-identity-practices-03
Workload Identity in Multi System Environments A. Schwenkschuster
Internet-Draft SPIRL
Intended status: Informational Y. Rosomakho
Expires: 20 April 2026 Zscaler
17 October 2025
Workload Identity Practices
draft-ietf-wimse-workload-identity-practices-03
Abstract
This document describes industry practices for providing secure
identities to workloads in container orchestration, cloud platforms,
and other workload platforms. It explains how workloads obtain
credentials for external authentication purposes, without managing
long-lived secrets directly. It does not take into account the
standards work in progress for the WIMSE architecture
[I-D.ietf-wimse-arch] and other protocols, such as
[I-D.ietf-wimse-s2s-protocol].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 20 April 2026.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 1]
Internet-Draft Workload Identity October 2025
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Delivery Patterns . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Environment Variables . . . . . . . . . . . . . . . . . . 5
3.2. Filesystem . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Local APIs . . . . . . . . . . . . . . . . . . . . . . . 6
4. Practices . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Kubernetes . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Secure Production Identity Framework For Everyone
(SPIFFE) . . . . . . . . . . . . . . . . . . . . . . . . 10
4.3. Cloud Providers . . . . . . . . . . . . . . . . . . . . . 12
4.4. Continuous Integration and Deployment Systems . . . . . . 14
4.5. Service Meshes . . . . . . . . . . . . . . . . . . . . . 15
5. Security Considerations . . . . . . . . . . . . . . . . . . . 16
5.1. Credential Delivery . . . . . . . . . . . . . . . . . . . 16
5.1.1. Environment Variables . . . . . . . . . . . . . . . . 16
5.1.2. Filesystem . . . . . . . . . . . . . . . . . . . . . 16
5.1.3. Local APIs . . . . . . . . . . . . . . . . . . . . . 17
5.2. Token typing . . . . . . . . . . . . . . . . . . . . . . 17
5.3. Custom claims are important for context . . . . . . . . . 17
5.4. Token lifetime . . . . . . . . . . . . . . . . . . . . . 18
5.5. Workload lifecycle and invalidation . . . . . . . . . . . 18
5.6. Proof of possession . . . . . . . . . . . . . . . . . . . 18
5.7. Audience . . . . . . . . . . . . . . . . . . . . . . . . 18
5.8. Multi-Tenancy Considerations . . . . . . . . . . . . . . 19
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
8.1. Normative References . . . . . . . . . . . . . . . . . . 19
8.2. Informative References . . . . . . . . . . . . . . . . . 20
Appendix A. Variations . . . . . . . . . . . . . . . . . . . . . 21
A.1. Direct access to protected resources . . . . . . . . . . 22
A.2. Custom assertion flows . . . . . . . . . . . . . . . . . 22
Appendix B. Document History . . . . . . . . . . . . . . . . . . 22
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 2]
Internet-Draft Workload Identity October 2025
1. Introduction
Just like people, the workloads inside container orchestration
systems (e.g., Kubernetes) need identities to authenticate with other
systems, such as databases, web servers, or other workloads. The
challenge for workloads is to obtain a credential that can be used to
authenticate with these resources without managing secrets directly,
for instance, an OAuth 2.0 access token.
The common use of the OAuth 2.0 framework [RFC6749] in this context
poses challenges, particularly in managing credentials. To address
this, the industry has shifted to a federation-based approach where
credentials of the underlying workload platform are used to
authenticate to other identity providers, which in turn, issue
credentials that grant access to resources.
Traditionally, workloads were provisioned with client credentials and
used for example the corresponding client credential flow
(Section 1.3.4 [RFC6749]) to retrieve an OAuth 2.0 access token.
This model presents a number of security and maintenance issues.
Secret materials must be provisioned and rotated, which requires
either automation to be built, or periodic manual effort. Secret
materials can be stolen and used by attackers to impersonate the
workload. Other, non OAuth 2.0 flows, such as direct API keys or
other secrets, suffer from the same issues.
Instead of provisioning secret material to the workload, one solution
to this problem is to attest the workload by using its underlying
platform. Many platforms provision workloads with a credential, such
as a JWT ([RFC7519]). Cryptographically signed by the platform's
issuer, this credential attests the workload and its attributes.
Figure 1 illustrates a generic pattern that is seen across many
workload platforms, more concrete variations are found in Section 4.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 3]
Internet-Draft Workload Identity October 2025
+----------------------------------------------------------+
| Workload Platform |
| +-----------------+ +------------------+ |
| | | | | |
| | Workload |<--------------->| Platform Issuer | |
| | | 1) push/pull | | |
| +-----+-+------+--+ credentials +------------------+ |
| | | | |
| | | | |
| | | | +--------------+ |
| | | | A) access | | |
| | | +----------------------->| Resource | |
| | | | | |
| | | +--------------+ |
+-------+-+------------------------------------------------+
| |
| | +--------------+
B1) federate | | B2) access | |
| +------------------------------>| Resource |
v | |
+-------------------+ +--------------+
| |
| Identity Provider |
| |
+-------------------+
Figure 1: Generic workload identity pattern
The figure outlines the following steps which are applicable in any
pattern.
* 1) Platform issues credential to workload. The way this is
achieved varies by platform, for instance, it can be pushed to the
workload or pulled by the workload.
* A) The credential can give the workload direct access to resources
within the platform or the platform itself (e.g., to perform
infrastructure operations)
* B1) The workload uses the credential to federate to an Identity
Provider. This step is optional and only needed when accessing
outside resources.
* B2) The workload accesses resources outside of the platform and
uses the federated identity obtained in the previous step.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 4]
Internet-Draft Workload Identity October 2025
Accessing different outside resources may require the workload to
repeat steps B1) and B2), federating to multiple Identity Providers.
It is also possible that step 1) needs to be repeated, for instance
in situations where the platform-issued credential is scoped to
accessing a certain resource or federating to a specific Identity
Provider.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Delivery Patterns
Credentials can be provisioned to the workload by different
mechanisms, each of which has its own advantages, challenges, and
security risks. The following section highlights the pros and cons
of common solutions. Security recommendations for these methods are
covered in Section 5.1.
3.1. Environment Variables
Injecting the credentials into the environment variables allows for
simple and fast deployments. Applications can directly access them
through system-level mechanisms, e.g., through the env command in
Linux. Note that environment variables are static in nature in that
they cannot be changed after application initialization.
3.2. Filesystem
Filesystem delivery allows both container secret injection and access
control. Many solutions find the main benefit in the asynchronous
provisioning of the credentials to the workload. This allows the
workload to run independently of the credentials update, and to
access them by reading the file.
Credential rotation requires a solution to detect soon-to-expire
secrets as a rotation trigger. One practice is that the new secret
is renewed _before_ the old secret is invalidated. For example, the
solution can choose to update the secret an hour before it is
invalidated. This gives applications time to update without
downtime.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 5]
Internet-Draft Workload Identity October 2025
Because credentials are written to a shared filesystem, the solution
is responsible for ensuring atomicity when updating them. Writes
SHOULD be performed in a way that prevents workloads from observing a
partially written file (for example by writing to a temporary file
and renaming it atomically). Solutions SHOULD also perform a flush
operation immediately after the update to minimize the chance of race
conditions and ensure durability.
3.3. Local APIs
In this pattern, the workload obtains credentials by communicating
with a local API exposed by the credential issuer. Implementations
commonly use UNIX domain sockets (e.g., SPIFFE), loopback interfaces,
or link-local "magic addresses" 169.254.169.254 commonly used for
cloud provider Instance Metadata Services as the transport mechanism.
Local APIs support re-provisioning of updated credentials, either on
demand or through persistent connections that enable the issuer to
push new credentials. This enables the use of short-lived, narrowly
scoped credentials, improving security posture compared to long-lived
secrets.
The security of this approach relies heavily on network isolation to
prevent unauthorised access to the local API. In addition, the
pattern requires client-side code, which may introduce portability
challenges. The request–response paradigm can also increase latency,
particularly when communication goes over the network.
4. Practices
The following practices outline more concrete examples of platforms,
including their delivery patterns.
4.1. Kubernetes
In Kubernetes, machine identity is implemented through "service
accounts" [KubernetesServiceAccount]. Service accounts can be
explicitly created, or a default one is automatically assigned.
Service accounts use JSON Web Tokens (JWTs) [RFC7519] as their
credential format, with the Kubernetes Control Plane acting as the
signer.
Service accounts serve multiple authentication purposes within the
Kubernetes ecosystem. They are used to authenticate to Kubernetes
APIs, between different workloads and to access external resources.
This latter use case is particularly relevant for the purposes of
this document.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 6]
Internet-Draft Workload Identity October 2025
To programmatically use service accounts, workloads can:
* Have the token "projected" into the file system of the workload.
This is similar to volume mounting in non-Kubernetes environments,
and is commonly referred to as "projected service account token".
* Use the Token Request API [TokenRequestV1] of the control plane.
This option, however, requires an initial projected service
account token as a means of authentication.
Both options allow workloads to:
* Specify a custom audience. Possible audiences can be restricted
based on policy.
* Specify a custom lifetime. Maximum lifetime can be restricted by
policy.
* Bind the token lifetime to an object lifecycle. This allows the
token to be invalidated when the object is deleted. For example,
this may happen when a Kubernetes Deployment is removed from the
server. Note that invalidation is only detected when the Token
Review API [TokenReviewV1] of Kubernetes is used to validate the
token.
To validate service account tokens, Kubernetes allows workloads to:
* Make use of the Token Review API [TokenReviewV1]. This API
introspects the token, makes sure it hasn't been invalidated and
returns the claims.
* Mount the public keys used to sign the tokens into the file system
of the workload. This allows workloads to validate a token's
signature without calling the Token Review API.
* Optionally, a JSON Web Key Set [RFC7517] is exposed via a web
server. This allows the Service Account Token to be validated
outside of the cluster and access to the actual Kubernetes Control
Plane API.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 7]
Internet-Draft Workload Identity October 2025
+-------------------------------------------------+
| Kubernetes |
| +--------------+ |
| A1) access | | |
| +-------------->| API Server | |
| | | | |
| | +--------------+ |
| +----+----+ ^ 1) request token |
| | | 2) schedule +----+----+ |
| | Pod |<------------+ Kubelet | |
| | | +---------+ |
| +-+-+---+-+ |
| | | | +--------------+ |
| | | | B1) access | | |
| | | +--------------------->| Resource | |
| | | | | |
| | | +--------------+ |
| | | |
+---+-+-------------------------------------------+
| |
| | +--------------+
C1) federate | | C2) access | |
| +------------------------->| Resource |
v | |
+---------------------+ +--------------+
| |
| Identity Provider |
| |
+---------------------+
Figure 2: Kubernetes workload identity in practice
The steps shown in Figure 2 are:
* 1) The kubelet is tasked to schedule a Pod. Based on
configuration, it requests a Service Account Token from the
Kubernetes API server.
* 2) The kubelet starts the Pod and, based on the configuration of
the Pod, delivers the token to the containers within the Pod.
Now, the Pod can use the token to:
* A) Access the Kubernetes Control Plane, considering it has access
to it.
* B) Access other resources within the cluster, for instance, other
Pods.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 8]
Internet-Draft Workload Identity October 2025
* C) Access resources outside of the cluster:
- C1) The application within the Pod uses the Service Account
Token to federate to an Identity Provider outside of the
Kubernetes Cluster.
- C2) Using the federated identity, the application within the
Pod accesses resources outside of the cluster.
As an example, the following JSON illustrates the claims contained in
a Kubernetes Service Account token.
{
"aud": [ # matches the requested audiences, or the API server's default audiences when none are explicitly requested
"https://kubernetes.default.svc"
],
"exp": 1731613413,
"iat": 1700077413,
"iss": "https://kubernetes.default.svc", # matches the first value passed to the --service-account-issuer flag
"jti": "ea28ed49-2e11-4280-9ec5-bc3d1d84661a", # ServiceAccountTokenJTI feature must be enabled for the claim to be present
"kubernetes.io": {
"namespace": "my-namespace",
"node": { # ServiceAccountTokenPodNodeInfo feature must be enabled for the API server to add this node reference claim
"name": "127.0.0.1",
"uid": "58456cb0-dd00-45ed-b797-5578fdceaced"
},
"pod": {
"name": "my-workload-69cbfb9798-jv9gn",
"uid": "778a530c-b3f4-47c0-9cd5-ab018fb64f33"
},
"serviceaccount": {
"name": "my-workload",
"uid": "a087d5a0-e1dd-43ec-93ac-f13d89cd13af"
},
"warnafter": 1700081020
},
"nbf": 1700077413,
"sub": "system:serviceaccount:my-namespace:my-workload"
}
Figure 3: Example Kubernetes Service Account Token claims
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 9]
Internet-Draft Workload Identity October 2025
4.2. Secure Production Identity Framework For Everyone (SPIFFE)
The Secure Production Identity Framework For Everyone, also known as
SPIFFE [SPIFFE], is a Cloud Native Computing Foundation (CNCF)
project that defines a "Workload API" to deliver machine identity to
workloads. Workloads can retrieve either X.509 certificates or JWTs.
The Workload API does not require clients to authenticate themselves.
Instead, implementation collect identifying information of the
workload from the environment, such as the workload platform or the
operating system.
SPIFFE refers to the JWT-formatted credential as a "JWT-SVID" (JWT -
SPIFFE Verifiable Identity Document) and the X509-formatted
credential as "X509-SVID".
Workloads are required to specify at least one audience when
requesting a JWT-SVID from the Workload API.
For validation, SPIFFE offers:
* A set of public keys encoded in JWK format [RFC7517] retrieved
from the Workload API that can be used to validate signatures. In
SPIFFE this is referred to as the "trust bundle".
* An endpoint where the public keys used for signing are published
in JWK format [RFC7517]. See SPIFFE Bundle Endpoint at [SPIFFE].
The following figure illustrates how a workload can use its JWT-SVID
to access a protected resource outside of SPIFFE:
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 10]
Internet-Draft Workload Identity October 2025
+--------------------------------------------------------+
| SPIFFE Trust Domain |
| |
| +--------------+ 1) Get JWT-SVID +--------------+ |
| | +-------------------->| SPIFFE | |
| | Workload | | Workload API | |
| | | +--------------+ |
| +----+-+----+--+ |
| | | | +--------------+ |
| | | | A) access | | |
| | | +----------------------->| Resource | |
| | | | | |
| | | +--------------+ |
+------+-+-----------------------------------------------+
| |
| | +--------------+
B1) federate | | B2) access | |
| +---------------------------->| Resource |
v | |
+---------------------+ +--------------+
| |
| Identity Provider |
| |
+---------------------+
Figure 4: Workload identity in SPIFFE
The steps shown in Figure 4 are:
* 1) The workload requests a JWT-SVID from the SPIFFE Workload API.
* A) The JWT-SVID can be used to directly access resources or other
workloads within the same SPIFFE Trust Domain.
* B1) To access resources protected by other Identity Providers, the
workload uses the SPIFFE JWT-SVID to federate to the Identity
Provider.
* B2) Once federated, the workload can access resources outside of
its trust domain.
Here are example claims for a JWT-SVID:
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 11]
Internet-Draft Workload Identity October 2025
{
"aud": [
"external-authorization-server"
],
"exp": 1729087175,
"iat": 1729086875,
"sub": "spiffe://example.org/myservice"
}
4.3. Cloud Providers
Workloads in cloud platforms can have any shape or form.
Historically, virtual machines were the most common. The
introduction of containerization brought hosted container
environments or Kubernetes clusters. Containers have evolved into
serverless offerings. Regardless of the actual workload packaging,
distribution, or runtime platform, all these workloads need
identities.
The biggest cloud providers have established the pattern of an
"Instance Metadata Endpoint". Aside from allowing workloads to
retrieve metadata about themselves, it also allows them to receive
identity. The credential types offered can vary. JWT, however, is
the one that is common across all of them. The issued credential
provides proof to anyone it is being presented to that the workload
platform has attested the workload and it can be considered
authenticated.
Within a cloud provider, the issued credential can often directly be
used to access resources of any kind across the platform, making
integration between the services straightforward. From the workload
perspective, no credential needs to be issued, provisioned, rotated
or revoked, as everything is handled internally by the platform.
This is not true for resources outside of the platform, such as on-
premise resources, generic web servers or other cloud provider
resources. Here, the workload first needs to federate to the Secure
Token Service (STS) of the respective cloud, which is effectively an
Identity Provider. The STS issues a new credential with which the
workload can then access resources.
This pattern also applies when accessing resources in the same cloud
but across different security boundaries (e.g., different account or
tenant). The actual flows and implementations may vary in these
situations though.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 12]
Internet-Draft Workload Identity October 2025
+----------------------------------------------------------+
| Cloud |
| |
| +-------------------+ |
| +--------------+ 1) get identity | | |
| | +---------------->| Instance Metadata | |
| | Workload | | Service/Endpoint | |
| | | | | |
| +-----+-+----+-+ +-------------------+ |
| | | | |
| | | | +--------------+ |
| | | | A) access | | |
| | | +----------------------->| Resource | |
| | | | | |
| | | +--------------+ |
+--------+-+-----------------------------------------------+
| |
B1) federate | | B2) access
| |
+--------+-+-----------------------------------------------+
| | | External (e.g. other cloud) |
| | | |
| | | +--------------+ |
| | | | | |
| | +---------------------------->| Resource | |
| v | | |
| +-----------------------------+ +--------------+ |
| | | |
| | Secure Token Service (STS) | |
| | | |
| +-----------------------------+ |
+----------------------------------------------------------+
Figure 5: Workload identity in a cloud provider
The steps shown in Figure 5 are:
* 1) The workload retrieves an identity from the Instance Metadata
Service or Endpoint. This endpoint exposes an API and is
available at a well- known, but local-only location such as
169.254.169.254.
When the workload needs to access a resource within the cloud (e.g.,
located in the same security boundary; protected by the same issuer
as the workload identity):
* A) The workload directly accesses the protected resource with the
credential issued in Step 1.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 13]
Internet-Draft Workload Identity October 2025
When the workload needs to access a resource outside of the cloud
(e.g., different cloud; same cloud, but different security boundary):
* B1) The workload uses the cloud-issued credential to federate to
the Secure Token Service of the other cloud/account.
* B2) Using the federated identity, the workload can access the
resource outside, assuming the federated identity has the
necessary permissions.
4.4. Continuous Integration and Deployment Systems
Continuous integration and deployment (CI-CD) systems allow their
pipelines (or workflows) to receive an identity at runtime. It is a
common task to upload build outputs and other artifacts to external
resources. For this, federation to external Identity Providers is
often necessary.
+-------------------------------------------------+
| Continuous Integration / Deployment Platform |
| |
| +-----------------+ +------------+ |
| | | 1) schedule | | |
| | Pipeline/Task |<------------+ Platform | |
| | (Workload) | | | |
| | | +------------+ |
| +-----+-+---------+ |
+-------+-+---------------------------------------+
| |
| | +--------------+
2) federate | | 3) access | |
| +-------------------->| Resource |
v | |
+-------------------+ +--------------+
| |
| Identity Provider |
| |
+-------------------+
Figure 6: OAuth2 Assertion Flow in a continuous integration/
deployment environment
The steps shown in Figure 6 are:
* 1) The CI-CD platform schedules a workload (pipeline or task).
Based on configuration, a Workload Identity is made available by
the platform.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 14]
Internet-Draft Workload Identity October 2025
* 2) The workload uses the identity to federate to an Identity
Provider.
* 3) The workload uses the federated identity to access resources.
For instance, an artifact store to upload compiled binaries, or to
download libraries needed to resolve dependencies. It is also
common to access actual infrastructure as resources to make
deployments or changes to it.
While token structure is vendor-specific, all tokens contain claims
carrying the basic context of the executed tasks, such as source code
management data such as git branch, initiation context and more.
4.5. Service Meshes
Service meshes provide infrastructure-level workload identity and
secure communication for applications through sidecar proxies
deployed alongside each workload. In a service mesh, workload
identity is typically implemented using X.509 certificates issued by
the service mesh. Service meshes handle identity credential
provisioning to sidecar proxies rather than directly to application
workloads. The sidecar intercepts network traffic and handles
authentication transparently to the application code.
+--------------+
| |
+-------+ Service Mesh +--------+
1) issue | | | | 1) issue
identity | +--------------+ | identity
| |
v 3) communicate v
+-----------+ on behalf of +-----------+
| | workloads | |
| Proxy |<=================>| Proxy |
| | | |
+-----------+ +-----------+
^ ^
| 2) delegate | 2) delegate
| |
+-----+-----+ +-----+-----+
| | | |
| Workload | | Workload |
| | | |
+-----------+ +-----------+
Figure 7: Simple service mesh communication between 2 workload
The steps shown in Figure 7 are:
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 15]
Internet-Draft Workload Identity October 2025
* 1) The Service Mesh issues identities in the form of credentials
to proxies.
* 2) The proxies act on behalf of workloads that delegate their
communication to them. In above figure each workload has its own
proxy that solely represents it and no other workload.
* 3) The proxies communicate with each other on behalf of the
workloads they represent. This communication includes
authentication spects, for instance in the form of X.509
certificates.
In above pattern each workload has a specific sidecar. An
alternative deployment is to share proxies between workloads. This
often results in a single proxy on each node acting on behalf of all
workloads on the node.
5. Security Considerations
All security considerations in section 8 of [RFC7521] apply.
5.1. Credential Delivery
5.1.1. Environment Variables
Leveraging environment variables to provide credentials presents many
security limitations. Environment variables have a wide set of use
cases and are observed by many components. They are often captured
for monitoring, observability, debugging and logging purposes and
sent to components outside of the workload. Access control is not
trivial and does not achieve the same security results as other
methods.
This approach should be limited to non-production cases where
convenience outweighs security considerations, and the provided
secrets are limited in validity or utility. For example, an initial
secret might be used during the setup of the application.
5.1.2. Filesystem
* 1) Access control to the mounted file should be configured to
limit reads to authorized applications. Linux supports solutions
such as DAC (uid and gid) or MAC (e.g., SELinux, AppArmor).
* 2) Mounted shared memory should be isolated from other host OS
paths and processes. For example, on Linux this can be achieved
by using namespaces.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 16]
Internet-Draft Workload Identity October 2025
5.1.3. Local APIs
Local APIs often operate in clear-text such as unencrypted HTTP
without any confidentiality or integrity protection. Privileged
component on the machine or in the infrastructure can be able to
eyes-drop the connection and the credential within it.
Mitigating measures are required to mitigate a particular variant of
Server-Side Request Forgery attacks against local APIs. For example,
requiring a specific header that cannot be controlled externally or
preventing the use of link-local IPs, including through redirects.
Adequate attestation is required to make sure unauthorized access is
denied and credentials are not issued to other parties when the Local
API is unauthenticated. Introspection of the platform, like in
SPIFFE or cloud providers, can be used to identify workloads and
grant access. The more fine-grained and strict the attestation, the
smaller the attack surface. For instance, allowing access by IP or
other machine-global identifiers permits any process to receive the
identity, while including user ID or other process-scoped identifiers
prevents this broader access.
The potential for denial-of-service attacks against Local APIs need
to be taken into account and protective measures should be
implemented. Depending on the platform these attacks can affect
other workloads and their ability to receive a platform credential.
5.2. Token typing
Issuers SHOULD strongly type the issued tokens to workloads via the
JOSE typ header and Identity Providers accepting these tokens SHOULD
validate the value of it according to policy. See Section 3.1 of
[RFC8725] for details on explicit typing.
Issuers SHOULD use authorization-grant+jwt as a typ value according
to [I-D.ietf-oauth-rfc7523bis]. For broad support, JWT or JOSE MAY
be used by issuers and accepted by authorization servers but it is
important to highlight that a wide range of tokens, meant for all
sorts of purposes, use these values and would be accepted.
5.3. Custom claims are important for context
Some platform-issued credentials have custom claims that are vital
for context and are required to be validated. For example, in a
continuous integration and deployment platform where a workload is
scheduled for a Git repository, the branch is crucial. A "main"
branch may be protected and considered trusted to federate to
external authorization servers. But other branches may not be
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 17]
Internet-Draft Workload Identity October 2025
allowed to access protected resources.
Authorization servers that validate assertions SHOULD make use of
these claims. Platform issuers SHOULD allow differentiation based on
the subject claim alone.
5.4. Token lifetime
Tokens SHOULD NOT exceed the lifetime of the workloads they
represent. For example, a workload that has an expected lifetime of
one hour should not receive a token valid for two hours or more.
Within the scope of this document, where a platform-issued credential
is used to authenticate to retrieve an access token for an external
authorization domain, short-lived credentials are recommended.
5.5. Workload lifecycle and invalidation
Platform issuers SHOULD invalidate tokens when the workload stops,
pauses, or ceases to exist and SHOULD offer validators a mechanism to
query this status. How these credentials are invalidated and the
status is queried varies and is not in scope of this document.
5.6. Proof of possession
Credentials SHOULD be bound to workloads, and proof of possession
SHOULD be performed when these credentials are used. This mitigates
token theft. This proof of possession applies to both the platform
credential and the access token of the external authorization
domains.
5.7. Audience
For issued credentials in the form of JWTs, they MUST be audienced
using the aud claim. Each JWT SHOULD only carry a single audience.
We RECOMMEND using URIs to specify audiences. See Section 3 of
[RFC8707] for more details and security implications.
Some workload platforms provide credentials for interacting with
their own APIs (e.g., Kubernetes). These credentials MUST NOT be
used beyond the platform API. In the example of Kubernetes, a token
used for anything other than the Kubernetes API itself MUST NOT carry
the Kubernetes server in the aud claim.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 18]
Internet-Draft Workload Identity October 2025
5.8. Multi-Tenancy Considerations
In multi-tenant platforms, relying parties MUST carefully evaluate
which attributes are considered trustworthy when making authorization
decisions. Access or federation MUST NOT be granted based solely on
untrusted or easily forgeable attributes. In particular, the issuer
claim in such environments may not uniquely identify a trusted
authority, since each tenant could be configured with the same issuer
identifier.
Relying parties SHOULD ensure that attributes used for authorization
are bound to a trust domain under their control or validated by an
entity with a clearly defined trust boundary.
6. IANA Considerations
This document does not require actions by IANA.
7. Acknowledgements
The authors and contributors would like to thank the following people
for their feedback and contributions to this document (in no
particular order): Dag Sneeggen, Ned Smith, Dean H. Saxe, Yaron
Sheffer, Andrii Deinega, Marcel Levy, Justin Richer, Pieter
Kasselmann, Simon Canning, Evan Gilman and Joseph Salowey.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/rfc/rfc6749>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/rfc/rfc7517>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/rfc/rfc7519>.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 19]
Internet-Draft Workload Identity October 2025
[RFC7521] Campbell, B., Mortimore, C., Jones, M., and Y. Goland,
"Assertion Framework for OAuth 2.0 Client Authentication
and Authorization Grants", RFC 7521, DOI 10.17487/RFC7521,
May 2015, <https://www.rfc-editor.org/rfc/rfc7521>.
[RFC7523] Jones, M., Campbell, B., and C. Mortimore, "JSON Web Token
(JWT) Profile for OAuth 2.0 Client Authentication and
Authorization Grants", RFC 7523, DOI 10.17487/RFC7523, May
2015, <https://www.rfc-editor.org/rfc/rfc7523>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8414] Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
Authorization Server Metadata", RFC 8414,
DOI 10.17487/RFC8414, June 2018,
<https://www.rfc-editor.org/rfc/rfc8414>.
[RFC8693] Jones, M., Nadalin, A., Campbell, B., Ed., Bradley, J.,
and C. Mortimore, "OAuth 2.0 Token Exchange", RFC 8693,
DOI 10.17487/RFC8693, January 2020,
<https://www.rfc-editor.org/rfc/rfc8693>.
[RFC8707] Campbell, B., Bradley, J., and H. Tschofenig, "Resource
Indicators for OAuth 2.0", RFC 8707, DOI 10.17487/RFC8707,
February 2020, <https://www.rfc-editor.org/rfc/rfc8707>.
[RFC8725] Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
Current Practices", BCP 225, RFC 8725,
DOI 10.17487/RFC8725, February 2020,
<https://www.rfc-editor.org/rfc/rfc8725>.
8.2. Informative References
[I-D.ietf-oauth-rfc7523bis]
Jones, M. B., Campbell, B., Mortimore, C., and F. Skokan,
"Updates to OAuth 2.0 JSON Web Token (JWT) Client
Authentication and Assertion-Based Authorization Grants",
Work in Progress, Internet-Draft, draft-ietf-oauth-
rfc7523bis-03, 7 October 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-oauth-
rfc7523bis-03>.
[I-D.ietf-wimse-arch]
Salowey, J. A., Rosomakho, Y., and H. Tschofenig,
"Workload Identity in a Multi System Environment (WIMSE)
Architecture", Work in Progress, Internet-Draft, draft-
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 20]
Internet-Draft Workload Identity October 2025
ietf-wimse-arch-06, 30 September 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-wimse-
arch-06>.
[I-D.ietf-wimse-s2s-protocol]
Campbell, B., Salowey, J. A., Schwenkschuster, A., and Y.
Sheffer, "WIMSE Workload-to-Workload Authentication", Work
in Progress, Internet-Draft, draft-ietf-wimse-s2s-
protocol-07, 16 October 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-wimse-
s2s-protocol-07>.
[KubernetesServiceAccount]
"Kubernetes Service Account", May 2024,
<https://kubernetes.io/docs/concepts/security/service-
accounts/>.
[OIDC] Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0 incorporating
errata set 1", November 2014,
<https://openid.net/specs/openid-connect-core-1_0.html>.
[OIDCDiscovery]
Sakimura, N., Bradley, J., Jones, M. and Jay, E., "OpenID
Connect Discovery 1.0 incorporating errata set 2",
December 2023, <https://openid.net/specs/openid-connect-
discovery-1_0.html>.
[SPIFFE] "Secure Production Identity Framework for Everyone
(SPIFFE)", May 2023,
<https://github.com/spiffe/spiffe/blob/main/standards/
SPIFFE.md>.
[TokenRequestV1]
"Kubernetes Token Request API V1", August 2024,
<https://kubernetes.io/docs/reference/kubernetes-api/
authentication-resources/token-request-v1/>.
[TokenReviewV1]
"Kubernetes Token Review API V1", August 2024,
<https://kubernetes.io/docs/reference/kubernetes-api/
authentication-resources/token-review-v1/>.
Appendix A. Variations
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 21]
Internet-Draft Workload Identity October 2025
A.1. Direct access to protected resources
Resource servers that protect resources may choose to trust multiple
authorization servers, including the one that issues the platform
identities. Instead of using the platform-issued identity to receive
an access token of a different authorization domain, workloads can
directly use the platform-issued identity to access a protected
resource.
In this case, technically, the protected resource and workload are
part of the same authorization domain.
A.2. Custom assertion flows
While [RFC7521] and [RFC7523] are the proposed standards for this
pattern, some authorization servers use [RFC8693] or a custom API for
the issuance of an access token based on existing platform identity
credentials. These patterns are not recommended and prevent
interoperability.
Appendix B. Document History
[[ To be removed from the final specification ]]
-03
* Add service-mesh section
* Add multi-tenancy considerations
* Add atomicity and flushing requirements to filesystem section
* Make it clear that invalidation is a matter of querying the status
* Rework local api section & security considerations
* Refer to RFC7517 in SPIFFE and add clarity on key distribution
* Editorial changes
-02
* Updated structure, bringing concrete examples back into the main
text.
* Use more generic "federation" term instead of RFC 7523 specifics.
* Overall editorial improvements.
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 22]
Internet-Draft Workload Identity October 2025
* Fix reference of Kubernetes Token Request API
* Prefer the term "document" over "specification".
* Update contributor and acknowledgements sections.
* Remove section about OIDC as it is too specific to a certain
implementation.
* Rewrite abstract to better reflect the current content of the
document.
-01
* Add credential delivery mechanisms
* Highlight relationship to other WIMSE work
* Add details about token typing and relation to OpenID Connect
* Add security considerations for audience
-00
* Rename draft with no content changes.
* Set Arndt to Editor role.
*[as draft-wimse-workload-identity-bcp]*
-02
* Move scope from Kubernetes to generic workload identity platform
* Add various patterns to appendix
- Kubernetes
- Cloud providers
- SPIFFE
- CI/CD
* Add some security considerations
* Update title
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 23]
Internet-Draft Workload Identity October 2025
-01
* Editorial updates
-00
* Adopted by the WIMSE WG
Contributors
Benedikt Hofmann
Siemens
Email: hofmann.benedikt@siemens.com
Hannes Tschofenig
Siemens
Email: hannes.tschofenig@gmx.net
Edoardo Giordano
Nokia
Email: edoardo.giordano@nokia.com
Authors' Addresses
Arndt Schwenkschuster
SPIRL
Email: arndts.ietf@gmail.com
Yaroslav Rosomakho
Zscaler
Email: yrosomakho@zscaler.com
Schwenkschuster & RosomakhExpires 20 April 2026 [Page 24]